GRAZING POTENTIAL AND ECONOMIC VIABILITY OF 

CORN (Zea mays L.) PRODUCTION IN LIVING MULCH SYSTEMS 

  

 

 

 

 

A Dissertation Presented for the 

Doctor of Philosophy 

Degree 

The University of Tennessee, Knoxville 

 

 

 

 

 

 

Márcia Pereira Quinby 

August 2022 

  



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Copyright © 2022 by Márcia Pereira Quinby. 

All rights reserved. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  



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ACKNOWLEDGEMENTS 

To God for allowing me to come until here. To my mentor Dr. Renata Oakes that guided 

me throughout graduate school and her patience during my learning process. To my 

committee members: Dr. Gary Bates, Dr. Carl Sams, Dr. Virginia Sykes, and Dr. Chris 

Boyer, for giving me advice to help me succeed on my research and academic life. To the 

staff and facilities of the Middle Tennessee Research and Education Center (MTREC) 

and The University of Tennessee where my studies were conducted. To the CIG NRCS 

grant for funding part of my project, including Dr. Nicholas Hill and Dr. Matthew Levi 

from the University of Georgia. To my graduate student colleagues Dereck Corbin, Tracy 

Hawk, Tyler Carr, Brooke Keadle, Dr. Devon Carroll, Diana Ramirez, and Dr. Erick 

Ribeiro. To my husband Jack Quinby for staying by my side, for his encouragement, 

love, and inspiration, thank you. To my parents Eleni and Anisio da Silva, and my 

siblings Elaine Wilson and Anisio Jr., that although from afar, provided me with love and 

support during these years of school.  

 

 

 



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ABSTRACT 

Living mulch (LM) is a practice in which forages are grown simultaneously with 

the main crop, serving as a living cover throughout the growing season. The LM systems 

were developed to alleviate concerns of soil depletion and reduce negative effects of 

tillage on soil productivity. In addition, legumes used, it can decrease the reliance on N 

fertilizer. The use of corn in LM has been previously studied due to the crop being a large 

commodity in the U.S. In addition, the ability to graze the LM after corn production can 

increase land use efficiency. To determine the benefits of LM in the Southeastern U.S., 

two studies were developed. The first study had WC (Trifolium repens L. [WC]) LM and 

a mixture of crimson clover (Trifolium incarnatum L.) and cereal rye (Secale cereale L. 

[CCCR]), in Spring Hill, TN from 2018 to 2021. Cull cows were used for the grazing 

period of four weeks before planting and after harvest of corn. The study evaluated the 

botanical composition (BC), LM mass (LMM), nutritive value (NV), corn silage and 

grain production, and cows average daily gain (ADG). The second experiment contained 

WC LM seeded with corn silage and grain in different N levels to determine the best 

level of fertilization when utilizing WC. The production of corn at harvest, botanical 

composition, and LM mass throughout the corn growing season were assessed. Lastly, 

economic analysis was performed in both projects to determine the viability of the 

system. 

 

 



v 

 

TABLE OF CONTENTS 

1. INTRODUCTION .............................................................................................................. 1 

Living mulch species (e. g. white clover, crimson clover, and cereal rye) ..... 4 

Living Mulch Grazing..................................................................................... 7 

Living mulch economics ................................................................................. 8 

Objectives ..................................................................................................... 10 

References ......................................................................................................... 11 

1. CHAPTER I: Corn Production in Living Mulch Systems in the Southeastern U.S. ........ 23 

Abstract ............................................................................................................. 24 

Introduction ....................................................................................................... 25 

Materials & Methods ........................................................................................ 26 

Measurements and Management ................................................................... 27 

Living mulch botanical composition, mass, and nutritive value .................. 29 

Corn production and nutritive value ............................................................. 30 

Grazing .......................................................................................................... 31 

Economic analysis ........................................................................................ 31 

Statistical analysis ......................................................................................... 32 

Results and Discussion ..................................................................................... 33 

Weather ......................................................................................................... 33 

Botanical composition (BC) ......................................................................... 33 

Living mulch mass (LMM) ........................................................................... 35 



vi 

 

Crude Protein value of LM ........................................................................... 35 

Corn production and nutritive value (NV) .................................................... 36 

Grazing .......................................................................................................... 39 

Economic analysis ........................................................................................ 44 

Conclusions ....................................................................................................... 44 

Appendix ........................................................................................................... 46 

References ......................................................................................................... 66 

2. CHAPTER II Nitrogen requirements for corn production in white clover living mulch 

systems 73 

Abstract ............................................................................................................. 74 

Introduction ....................................................................................................... 75 

Materials & Methods ........................................................................................ 76 

Measurements and Management ................................................................... 77 

LM botanical composition, mass, and nutritive value .................................. 78 

Corn production and nutritive value ............................................................. 79 

Statistical analysis ......................................................................................... 80 

Results & Discussion ........................................................................................ 80 

Weather ......................................................................................................... 80 

Experiment I.................................................................................................. 81 

Experiment II ................................................................................................ 86 

Conclusion ........................................................................................................ 90 



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Appendix ........................................................................................................... 91 

References ....................................................................................................... 105 

3. CHAPTER III: Assessment of yield and partial net returns of corn production in LM 

systems in different N LEVELS ..................................................................................... 110 

Abstract ........................................................................................................... 111 

Introduction ..................................................................................................... 112 

Material & Methods ........................................................................................ 113 

Economic analysis ...................................................................................... 114 

Statistical analysis ....................................................................................... 114 

Results & Discussion ...................................................................................... 115 

Weather ....................................................................................................... 115 

Corn production .......................................................................................... 115 

Partial net returns and implications of the LM system ............................... 116 

Conclusions ..................................................................................................... 117 

Appendix ......................................................................................................... 118 

References ....................................................................................................... 125 

4. CONCLUSIONS & FUTURE DIRECTIONS ............................................................... 128 

5. VITA 130 

 

  



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LIST OF TABLES 

Table 1-1: Grazing period, forage sampling dates and number of animals used on 

paddocks of corn growing with living mulch in 2020 and 2021 in Spring Hill, TN 46 

Table 1-2: Precipitation (mm) and temperature (ºC) from 2018 to 2021 field preparation 

and growing season, and 30-year average in Spring Hill, TN .................................. 47 

Table 1-3: Botanical composition (g kg-1) of living mulch (LM) (crimson clover/cereal 

rye, CCCR; and white clover, WC) and its differences between beginning and end of 

the corn growing season of two consecutive years in Spring Hill, TN. .................... 49 

Table 1-4: Living mulch mass (LMM) (kg ha-1) of white clover (WC) and a crimson 

clover-cereal rye mixture (CCCR) during the corn growing season of two 

consecutive years (2020 and 2021) in Spring Hill, TN ............................................ 51 

Table 1-5: Crude protein levels (g kg-1) of white clover (WC) and a crimson clover-cereal 

rye mixture (CCCR) as a living mulch during the corn growing season of two 

consecutive years (2020 and 2021) in Spring Hill, TN ............................................ 53 

Table 1-6: Corn grain and silage production (DM t ha-1) grown in living mulch systems 

(crimson clover and cereal mixture, CCCR; white clover, WC) of two consecutive 

growing seasons (2020 and 2021) in Spring Hill, TN .............................................. 54 

Table 1-7: Nutritive value of unfermented and fermented silage grown in living mulch 

systems during two consecutive growing seasons (2020 and 2021) in Spring Hill, 

TN ............................................................................................................................. 55 



ix 

 

Table 1-8: Nutritive value analysis of corn grain grown in living mulch systems during 

two consecutive growing seasons (2020 and 2021) in Spring Hill, TN ................... 56 

Table 1-9: Botanical composition (g kg-1) of living mulch (LM) (crimson clover/cereal 

rye, CCCR; and white clover, WC) and its differences between beginning and end of 

each 28-d grazing period during two consecutive years (2020 and 2021) in Spring 

Hill, TN. .................................................................................................................... 57 

Table 1-10: Living mulch mass (LMM, kg ha-1) at the beginning and end of each 28-d 

grazing period during two consecutive years in Spring Hill, TN. ............................ 60 

Table 1-11: Crude Protein (CP), Neutral Detergent Fiber (NDF), and In-Vitro Dry Matter 

Digestibility - 48 hours (IVTDMD48) ANOVA for the grazing LM nutritive values 

of CP, NDF, and IVTDMD48, during the grazing seasons in 2020 and 2021 in 

Spring Hill, TN ......................................................................................................... 61 

Table 1-12: Crude Protein (CP), Neutral Detergent Fiber (NDF), and In-Vitro Dry Matter 

Digestibility - 48 hours (IVTDMD48) for grain and silage paddocks at the beginning 

and end of grazing period of 30-days in Spring Hill, TN ......................................... 62 

Table 1-13: Average Daily Gain (ADG, kg) of cows in living mulch (LM) (crimson 

clover/cereal rye, CCCR; and white clover, WC) paddocks at the beginning and end 

of each 28-d grazing period during two consecutive years in Spring Hill, TN. ....... 63 

Table 1-14: Cost of production in 65% moisture ($ ha-1), corn yield (t ha-1), revenue ($ 

ha-1), and profit ($ ha-1) of corn production of silage and grain in no-LM (living 



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mulch) systems compared to CCCR (crimson clover-cereal rye mixtures) and white 

clover (WC) LM in Spring Hill, TN during 2020 and 2021 growing seasons. ........ 64 

Table 1-15: Difference in cost of production ($ ha-1) between no-LM (living mulch) and 

LM systems (CCCR, crimson clover-cereal rye; white clover, WC), $ per head, and 

$ per head per day in Spring and Fall grazing in 2020 and 2021 growing seasons in 

Spring Hill, TN. ........................................................................................................ 65 

Table 2-1: Living mulch (LM) botanical composition (DM g kg-1) grown with silage corn 

during two consecutive growing seasons (2020 and 2021) in Spring Hill, TN. ....... 92 

Table 2-2: Total living mulch (LM) mass (LM and weeds) (DM kg ha-1) grown with 

silage corn during two consecutive growing seasons (2020 and 2021) in Spring Hill, 

TN. ............................................................................................................................ 94 

Table 2-3: Living Mulch (LM) crude protein (CP), grown with silage corn during two 

consecutive growing seasons (2020 and 2021) in Spring Hill, TN. ......................... 95 

Table 2-4: Corn silage production (DM ton ha-1) during two consecutive growing seasons 

(2020 and 2021) in Spring Hill, TN. ......................................................................... 96 

Table 2-5: Nutritive value (g kg-1) of fermented and unfermented silage during two 

consecutive growing seasons (2020 and 2021) in Spring Hill, TN. ......................... 96 

Table 2-6: Living mulch (LM) botanical composition (DM g kg-1) grown with grain corn 

during two consecutive growing seasons (2020 and 2021) in Spring Hill, TN. ....... 99 



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Table 2-7: Total living mulch (LM) mass (LM and weeds) (DM kg ha-1) grown with 

grain corn during two consecutive growing seasons (2020 and 2021) in Spring Hill, 

TN. .......................................................................................................................... 101 

Table 2-8: Living Mulch (LM) crude protein (CP), grown with grain corn during two 

consecutive growing seasons (2020 and 2021) in Spring Hill, TN. ....................... 102 

Table 2-9: Corn grain production (Ton ha-1) during two consecutive growing seasons 

(2020 and 2021) in Spring Hill, TN. ....................................................................... 103 

Table 2-10: Nutritive value (g kg-1) of corn grain during two consecutive growing 

seasons (2020 and 2021) in Spring Hill, TN........................................................... 104 

Table 3-1: Variety, plating date, and seeding rates of LM grown in 2020 and 2021 in 

Spring Hill, TN. ...................................................................................................... 118 

Table 3-2: Variety, planting date, and seeding rates of LM grown in 2020 and 2021 in 

Spring Hill, TN. ...................................................................................................... 119 

Table 3-3: Annual budget of corn silage production within each assigned treatment with 

and without living mulch (LM) at different N fertilizer rates in Spring Hill, TN .. 122 

Table 3-4: Annual budget for corn grain production within each assigned treatment with 

and without living mulch (LM) at different N fertilizer rates in Spring Hill, TN .. 123 

Table 3-5: Yield of corn silage and grain in 2020 and 2021 growing seasons, and partial 

net returns within treatments in Spring Hill, TN .................................................... 124 

 

 



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LIST OF FIGURES 

Figure 1-1: Precipitation (mm) of June 2021 growing season and 30-year average in 

Spring Hill, TN ......................................................................................................... 48 

Figure 1-2: Botanical composition (BC) of living mulch (LM) (crimson clover/cereal rye, 

CCCR; and white clover, WC) paddocks during the 2020 and 2021 corn growing 

season in Spring Hill, TN.......................................................................................... 50 

Figure 1-3: Living mulch mass (LMM) (kg ha-1) of CCCR and WC during the growing 

season of 2020 and 2021 in Spring Hill, TN.. .......................................................... 52 

Figure 1-4: Botanical composition (BC) of living mulch (LM) (crimson clover/cereal rye, 

CCCR; and white clover, WC) paddocks during each 28-d grazing period on spring 

and fall of 2020 and 2021 in Spring Hill, TN. .......................................................... 59 

Figure 2-1: Precipitation (mm) and temperature (ºC) from 2018 to 2021 field preparation 

and growing season, and 30-year average in Spring Hill, TN .................................. 91 

Figure 3-1: Precipitation (in) and temperature (ºF) from 2018 to 2021 field preparation 

and growing season, and 30-year average in Spring Hill, TN ................................ 121 

 

 

 

 

 



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1. INTRODUCTION  

Corn (Zea mays L.) is the major cereal crop of the U.S. (Boyer & Hannah, 2000). The 

U.S. alone is responsible for 32% of the world corn production (FAS, 2022); and its holistic use, 

from human to animal consumption (Revilla et al., 2021; Hallauer, 2004), make this crop an 

important commodity around the world. Corn is a warm-season annual plant from the grass 

family, with fibrous root system, a single leaf at each node. Depending on the hybrid, it can 

reach 3.5-m in height (Tollenar & Dwyer, 1999). 

Corn is fed as silage or grain for animal production (Klopfenstein et al., 2013), especially 

in dairy production systems (Putnam & Delcurto, 2020). Total corn production in the 

Southeastern U.S. has increased 77% from 2007 to 2017, and silage is one of the most important 

forages for dairy producers (NASS Quick Stats1, 2020). Silage is a method of forage preservation 

through fermentation in an anaerobic environment, allowing the feed to be ready for cattle 

consumption (Muck et al., 2020). However, even though total corn production increased, silage 

production has simultaneously decreased 15% (NASS Quick Stats1, 2020) due to the sharp 

decline in dairy production in this region (Rahelizatovo & Gillespie, 1999).  

Although corn grain production keeps increasing, only 8% of the crop grain area is 

harvested in the Southeastern states (NASS, 2022). For this reason, strategies to increase the land 

use efficiency are necessary. In addition, corn production in the Southeastern U.S. is usually 

affected by poor soil health, and issues such as erosion can result in low yields. Strategies such 

as no-till (Cassel et al., 1995) and living mulch (LM) systems are helpful to overcome these 

issues. 

Living mulch is a system in which the forage species are established before or 

simultaneously with the row crop and maintained as a living cover throughout the growing 



2 

 

season (Hartwig & Ammon, 2002). One of the first known studies utilizing LM systems was 

conducted by Adrien Pieters in 1927, where the author demonstrates the different types of green 

manure that can be adopted by farmers to maintain soil health. In this report, LM is referred as a 

“companion crop”, where clovers were seeded with corn and oats; and, after harvesting the grain, 

the clovers were harvested for hay production (Pieters, 1927). In general, LM systems were 

developed to alleviate concerns of soil depletion and find reduce negative effects of tillage on 

soil productivity, since farmers would rely solely on tillage for weed control before the 

introduction of herbicides (Paine & Harrison, 1993).  

While conventional production can negatively affect the soil health (Kibblewhite, et al., 

2008), LM systems could have the opposite effect. The LM system can improve soil structure by 

reducing soil erosion (Siller et al., 2016) and restricting weed growth in between corn rows 

(Sanders et al., 2018). In addition, the U.S. and Europe are trying to encourage producers to 

reduce the use of synthetic N by recommending the use of green manures, legumes, and organic 

fertilizers (Prasad, 1998). When utilizing legumes as a LM, the association with Rhizobium spp. 

in legume roots leads to an influx of N, increasing the N pool for plant uptake (Peoples & 

Craswell, 1992). 

Nitrogen is an essential macronutrient for plant growth because it is responsible for 

amino acid and protein synthesis, and it is a component of the chlorophyll molecule (Barker & 

Culman, 2020; Tripathi et al., 2014) for photosynthesis. To meet the N demand of crops, 

synthetic N fertilizers are often used in most cash crop production systems.  However, these 

synthetic N fertilizers can have harmful side effects, such as acid rain and contamination of 

ground waters due to nitrate concentration, and ammonia volatilization (Prasad, 1998). For this 



3 

 

reason, the use of legumes to ease the amount of synthetic fertilizer can ultimately provide N to 

the corn (Andrews et al., 2018) through N transfer.  

The N transfer occurs through forage decomposition (Sanders et al., 2018), N from the 

root exudates (Paynel et al., 2001; Ta et al., 1986), or arbuscular mychorrizal fungi (AMF) 

association (Thilakarathna et al., 2016). According to Soumare et al. (2020), AMF aids BNF 

(Biological Nitrogen Fixation) by the direct or indirect interaction with microorganisms that have 

N-fixing functions. In addition, lower N fertilization should be applied to assure that the N 

uptake comes from the BNF rather than chemical fertilization (Ledgard et al., 2001). Enriquez-

Hidalgo et al. (2006), it found that synthetic N fertilization reduces the amount of fixed N with 

increased N fertilizer. The BNF is an energetically costly system, thus, when N is available in 

soils, the roots association do not occur effectively. According to Kunelius (1974), N fertilization 

decreases the nodulation and weight of the nodules in legume, which leads to less BNF. 

Therefore, intensive management and adequate environmental conditions are necessary for the 

success of the LM system. 

A study conducted in Nova Scotia showed that the LM system is limited in climates with 

lower temperatures, because the LM leads to lower soil temperature, delaying corn emergence, 

development, and increasing its sensitivity to frost (Martin et al., 1999). In the other hand, a 

study conducted in Georgia concluded that LM systems can be successful in areas with warmer 

soils (Andrews et al., 2018), since higher soil temperatures can increase soil mineralization 

(Guntiñas et al., 2012) by releasing important nutrients for plant growth. 

According to Siller et al., (2016), the LM systems can decrease soil loss through erosion 

by 77% and P and N loss by 80%. Deguchi et al. (2017) observed that P fertilization might not 

be necessary in silage corn grown under LM systems, due to a potential increased mycorrhizal 



4 

 

association with the corn. Püschel et al. (2017) found that mychorrizal associations not only 

increase the P uptake, but also increase the total plant N through BNF. According to Israel 

(1987), P increases the number of nodules and fresh weight in soybeans; These. Therefore, these 

associations have a great impact in increasing crop production (Messa & Savioli, 2021) due to 

the increase in root contact surface by the fungal mycelia that develop in the roots (Smith & 

Smith, 2012) and for the increase in P acquisition that increases the efficiency of BNF by the 

increase of nodule mass (Divito & Sadras, 2014) 

To maximize cash crop production, suppression of the LM is necessary to avoid 

competition between corn and LM for nutrients and water (Sanders et al., 2017; Affeldt et al., 

2004; Hoffman et al., 1993). Zemenchik et al. (2000) studied kura clover as LM and found that, 

if the LM was not suppressed, it delayed corn emergence;. Ginakes et al. (2020) found that 

suppression of LM through tillage methods provided greater soil N, thus increasing grain yields. 

Similar responses were found using partial rototilling to suppress LM two weeks after corn 

emergence (Grubinger et al., 1990). 

Even though LM systems are, for the most part, beneficial, they can also produce some 

challenges. Several studies observed that corn yield tended to be lower under living mulch 

systems than corn grown conventionally (Hill, et al., 2021; Andrews et al., 2018; Sanders et al., 

2018; Ochsner et al., 2010). However, the benefits in local biodiversity must be considered, 

given the current emphasis in agricultural sustainable practices (Jordan et al., 2007). 

Living mulch species (e. g. white clover, crimson clover, and cereal rye)  

White clover is a cool-season perennial legume used for hay production, grazing, and 

cover crops; and it can be used both in mixtures or as a monoculture (Ball et al., 2007; Gibson & 



5 

 

Hollowell, 1966). White clover has the potential to biologically fix more than 200 kg of N per 

ha-1 (Wedin & Russelle, 2020). Given current sustainable efforts to reduce the use of synthetic N 

fertilization, the reliability on legumes can help the production of a neighboring species (Caradus 

et al., 1995).  

Van Eekeren et al. (2009) observed that introducing white clover to a grassland helps to 

maintain soil structure and increase supply of nutrients through the soil; Carlsen et al. (2012) 

found that white clover has the ability to release chemical compounds that regulate the soil 

microbial community to inhibit weed growth; and Chapman et al. (2016) concluded that the 

contribution of white clover to grass mixtures increased the forage accumulation in pastures, 

decreasing the need for synthetic N fertilization. Legume plants also have species-specific 

advantages when incorporated into a system. Brtnicky et al. (2021) observed that aboveground 

dry matter (DM) biomass was greater in crimson clover (Trifolium incarnatum L.) than white 

clover, but the root fresh biomass was greater in white clover than crimson clover. Yet, both 

species can be successfully utilized in forage systems. 

Crimson clover was first introduced in the U.S. in the early 1800’s (Westgate, 1913). It is 

a winter annual forage legume easily spotted by its red vibrant inflorescence. It is widely used in 

pasture, hay, or green manure (Ball et al., 2007). Crimson clover thrives in well-drained soil with 

moderate fertility (Duggar et al., 1925). Since it is a legume, it does not require N fertilization as 

it can fix up to 190 kg N ha-1 (Wedin & Russelle, 2020). In a study by Knight, 1967, crimson 

clover overseeded in grass swards increased the overall forage mass. Dyck & Liebman (1994) 

studied the use of crimson clover as green manure to suppress lambsquarter (Chenopodium 

album) and aid sweet corn growth, and observed that crimson clover suppressed the emergence 

and growth of weeds while not negatively affecting the germination and growth of sweet corn.  



6 

 

However, the seeding of crimson clover should be done before planting the main crop to 

avoid crimson clover establishment issues due to shading (Brooker et al., 2020). Youngerman et 

al. (2018) found that, although cover crops aid in the suppression of weeds, the negative 

relationship between corn density and cover crop biomass suggests that lower corn density 

would be beneficial to these systems to allow greater light transmission to the cover crop. Also, 

although crimson clover has slow N release (Dyck and Liebman, 1994), when used as a cover 

crop for corn production, it can release N before corn demand (Ranells and Wagger, 1996). 

Therefore). Therefore). Therefore, it is recommended that corn should be planted soon after 

incorporation of crimson clover cover crop (Yang et al., 2020). 

Crimson clover is often grown with cereal rye (Secale cereale L.) as a cover crop in row 

crops production for weed suppression and soil moisture conservation (Geddes & Gulden, 2021; 

Hodgskiss et al., 2021; Vann et al., 2018; Wiggins, et al., 2016). Cereal rye is considered an N 

scavenger (Andrews et al., 2020; Ranells and Wagger, 1997) and for this reason, must be 

suppressed to avoid competition with the corn (Ilnicki & Enache, 1992; Echtenkamp & 

Moomaw, 1989). Cereal rye has a high C:N ratio, but its N release can be delayed when 

compared to legumes (Sievers & Cook, 2018). Since 1940, the benefits of using cereal rye as 

weed suppressor in the U.S. have been reported (Faulkner, 1943), and since then, its use as a 

cover crop remains significant. 

Siller et al. (2016), found cereal rye with kura clover in corn silage, reduced water runoff 

and soil and nutrient losses. Rorick and Kladivko (2017) observed that cereal rye improved soil 

aggregate stability, helping with erosion control and improving water infiltration in no-till corn 

systems. Although crimson clover and cereal rye are commonly grown as cover crops, their use 



7 

 

as LM can decrease the extra costs of termination and incorporation of the forage in the systems 

before the cash crop. In addition, their use as LM has not been previously assessed. 

Living Mulch Grazing  

The need to provide sufficient nutritious forage for grazing animals has been recognized 

since the 1800’s by using grass and legume mixtures (Fussel, 1966). The use of legumes for 

animal consumption leads to better quality forage and, consequently, better quality manure 

which can assist in the growth of the subsequent row-crop (Fussel, 1967). There are several 

available white clover cultivars, and all can provide sufficient nutrients to grazing ruminants 

(Jahufer et al., 2021). In the Southeastern U.S., white clover can withstand persistent grazing due 

to its regional adaptation (Brink et al., 1999). When grazed by dairy cows, it can result in up to 

33% more milk than pastures without clovers (Harris et al., 1997). However, legume species as a 

monoculture in grazing systems are not common due to potential bloating issues. Therefore, 

grass and legume mixed pastures are often recommended. 

Binary mixtures of white clover with grasses result in positive effects on digestibility and 

protein components of the overall feed, which benefits the grazing animal (Brink et al., 2015). 

These benefits are expressed by greater milk production and lower methane emissions (Loza et 

al., 2021). Gerhards (2018) found the residual white clover LM was dense following corn 

harvest, which could be ideal for its use in grazing systems. In addition, when grazed in areas 

previously used for corn production, the cattle also would have access to corn stover for 

consumption (Franzluebbers & Stuedemann, 2014). 

The consumption of LM species, such as cereal rye, can provide sufficient forage very 

early in the growing season, since it is the most cold-hardy of all forages, with ADG greater than 



8 

 

0.8 kg per day (Mckee et al., 2017). Studies have shown that the grazing of cover crops can 

positively affect soil health. Schomberg et al. (2021) studied the grazing of cereal rye cover crop 

in no-till cotton systems and observed that cereal rye increased the C return to the soil organic 

matter (SOM) pool, improving soil health. Blanco-Canqui et al. (2020) observed that soil fertility 

and corn silage yield did not differ in grazed and non-grazed paddocks containing a cereal rye 

cover crop. The grazing of crimson clover-ryegrass cover crops also enhanced soil microbial 

biomass C under no till systems (Franzluebbers & Stuedemann, 2015).  

The average farm size in the Southeastern U.S. is 90 ha, according to 2019 summary of 

farmland in the U.S. (USDA, 2020). Therefore, the use of strategies that can optimize land use 

efficiency is warranted, and the grazing of LM can be beneficial. To define LM as a sustainable 

practice, it has to follow the three dimensions of sustainability, which are social, 

environmentally, and economic (Purvis et al., 2019). However, the economic assessment of LM 

system has yet to be performed. 

Living mulch economics 

The cropland in the U.S. has remained constant in the past 100 years; however, the land 

shifting of production makes land more vulnerable to erosion and nutrient loss (Lubowski et al., 

2006).  Every agricultural decision can affect the biodiversity and food security in a system 

(Kanter et al., 2018). The use of agricultural practices that deviate from monocultures are 

increasing and are often preferable given the sustainable targets of the 21st century (Jordan et al., 

2007). Practices such as intercropping and using cover crops or LM aid the net returns for row 

crop producers (Schnitkey et al., 2016). 



9 

 

Alexander et al. (2019) studied the use of kura clover LM in corn production and found 

that partial management costs are greater in LM systems than conventional corn production. The 

N costs were reduced by $132 ha-1 in the first year of production. Although, the costs were not 

different from conventional production in the second year, there are economic returns of stover 

harvest up to $318 ha-1 in LM systems.  

The use of forage legumes in cropping systems often decrease the reliance on N 

fertilization due to its BNF (Ledgard et al., 2001). However, to maximize yield in cropping 

systems such as corn, additional N fertilizer is essential, even when intercropping legumes in the 

system (Karpenstein-Machan & Stuelpnagel, 2000). This additional N fertilizer can be 

economically hefty, especially since urea is often the N fertilizer of choice. The use of urea 

exponentially increased from less than 20% of the total N fertilizer used worldwide to more than 

40% in 2005 (Gilbert et al., 2006). According to the USDA Economic Research Service, urea is 

one of the most utilized N sources for cropping systems, with 6,384,816 metric tons in 2015 

(USDA, 2019). Even when commodity prices increase, the high fertilizer prices result in 

negative net returns (Huang et al., 2009). In a publication by Huang (2009), the author explains 

that the increase in fertilizer prices since 2008 were due to exponential demand for production, 

intensifying the N reliance in crop monocultures. 

Corn is one of the most valuable commodities in the U.S. in agricultural exports, valued 

as more than 17 billion dollars in 2021 (USDA1, 2022). Heavy feeder cattle prices are positively 

affected by the increase in corn prices (Martinez et al., 2021), yet, according to the USDA 

agricultural projections, the price of corn in monoculture is expected to decrease from $4.53 per 

bushel to $4.00 per bushels in 10 years (USDA2, 2022). In TN, the pastureland asset value in $ 

ha-1 increased 225% from 1997 to 2021 (NASS Quick Stats2, 2022). The production of corn in 



10 

 

LM systems can be a good strategy compared to purchasing feed for backgrounding or cow-calf 

operations. Given the added benefit of LM in weed control (Westbrook et al., 2022), the 

potential decrease in herbicide use can account for further expense reductions. Tillage practices 

are known to negatively affect weed control. Ilnicki and Enache (1992) observed that minimum 

tillage or no-tillage practices decreased weed biomass when utilizing subterranean clover as LM. 

Therefore, the LM system must be assessed not only agronomically, but also economically. 

Objectives 

The objectives of this study were [1] to assess corn silage production, grain production, 

and grazing potential in white clover LM and in a crimson clover and cereal rye mixture [2] 

evaluate N fertilization rate effects on white clover LM systems for corn yield, and [3] determine 

the economic viability of the LM system in silage and grain. We hypothesized that [1] white 

clover LM system will be comparable to conventional systems in corn yield, and grazing will be 

an added economic benefit of the LM system with additional weight gain or maintenance, [2] the 

use of synthetic N fertilizer in LM system will be reduced while achieving comparable corn 

productivity to conventional corn systems, and [3] the LM system will confer economic 

advantages to producers in yield and profit. 

  



11 

 

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23 

 

 

1. CHAPTER I: CORN PRODUCTION IN LIVING MULCH SYSTEMS IN 

THE SOUTHEASTERN U.S.  

 

 

  



24 

 

 Abstract  

The living mulch (LM) system is a novelty in the southeastern U.S., and its viability and 

functionality must be studied. The objective of this study was to evaluate the benefits of LM in 

corn silage and grain production, and to evaluate the potential of LM grazing between the corn 

growing season. The experiment was conducted in Spring Hill, TN in 2020 and 2021, and 

consisted of two LM species, white clover (Trifolium repens L. [WC]) and a mixture of crimson 

clover (Trifolium incarnatum L.) and cereal rye (Secale cereale L. [CCCR]). Cull cows were 

used for the grazing period of four weeks before planting and after harvest of corn. The study 

evaluated the botanical composition (BC), LM mass (LMM), nutritive value (NV), corn silage 

and grain production, and cow average daily gain (ADG). The WC treatment had a greater weed 

control than CCCR. In 2020, when differences in LMM were observed, CCCR had greater LMM 

than WC. Meanwhile, in 2021 the LMM did not differ between WC and CCCR, with both 

treatments showing less mass in spring and early summer. Greater silage and grain production 

were observed in 2020 for WC paddocks, but, in 2021, no differences were observed. The ADG 

was greater in WC than CCCR paddocks. It was concluded that WC as LM can lead to greater 

corn production than CCCR. The LM for grazing is a beneficial strategy if feeding costs are 

greater than $2.28 head/day.  



25 

 

Introduction 

The inclusion of corn in living mulch (LM) systems are limited in the southeastern U.S., 

and the system could potentially benefit the environment as well as decrease the need for 

synthetic fertilization. The use of LM in the Southeastern U.S. has not yet been assessed for its 

potential for grazing operations to increase land use efficiency. Therefore, the necessity to 

determine the viability of the system is warranted. 

The LM is a system in which the forage species are established before or simultaneously 

with the row crop and maintained as a living cover throughout the growing season (Hartwig & 

Ammon, 2002). Living mulch can improve soil structure by reducing soil erosion (Siller et al., 

2016), while limiting weed competition in between corn rows (Sanders et al., 2018, Deguchi et 

al., 2017; Ilnicki & Enache, 1992). Additionally, legume species used as a living mulch can 

provide N to the corn (Andrews et al., 2018; Brophy & Heichel, 1989; Ebelhar et al., 1984).  

The utilization of white clover (Trifolium repens L. [WC]) intercropped with grass 

species has been long determined a good strategy to decrease the use of synthetic N fertilizers 

(Martin et al., 1999) due to its ability to biologically fix N (Peters et al., 2020). It grows best in 

the humid regions of the temperate zone (Gibson & Hollowell, 1966); therefore, TN is in a well-

suited region for incorporating WC. Meanwhile, cereal rye (Secale cereale L.) and crimson 

clover (Trifolium incarnatum L.) have been traditionally used as cover crops in corn production 

systems;; however, data in crimson clover or cereal rye as a living mulch do not exist.  

To ensure the benefits of LM in the field, LM must be well suppressed to avoid 

competition with the main crop. Studies examining the use of herbicides (Sanders et al., 2017; 

Eberlein et al., 1992) or mechanical suppression of LM (Grubinger & Minotti, 1990) have been 

conducted. Yet, LM grazing has the potential to suppress the LM before corn planting, while 



26 

 

providing sufficient feed for body weight maintenance of dry cows or weight gain of calves in 

integrated systems (Guy et al., 2020). According to Johansen et al. (2017), the grazing of WC 

can lead to greater milk production when compared to red clover and grasses. Meanwhile, cereal 

rye can extend the grazing season and, when mixed with legumes, can generate equal ADG to 

that from pastures without legumes and with 45 to 67 kg ha-1 of synthetic N fertilizer (Mckee, et 

al., 2017). Therefore, there is a need to determine the benefits of grazing and corn production in 

LM production systems.  

The objective of this study was to evaluate the benefits of two different LM in corn silage 

and grain production, and to evaluate the potential of LM grazing before and after the corn 

growing season in spring and fall. It was hypothesized that the LM systems can successfully 

increase corn production compared to no-LM systems, and produce sufficient LM mass for 

grazing operations. 

Materials & Methods 

The research was conducted at the Middle Tennessee Research and Education Center 

(MTREC) in Spring Hill, TN (35°72′ N, 86°96′ W) from October 2018 to April 2021. Initial soil 

nutrient levels on the experiment site were pH = 5.6, P = 810 kg ha-1, K =415 kg ha-1, Ca = 3904 

kg ha-1, and Mg = 300 kg ha-1. The area consisted of several well drained soil types with 

elevation ranging from 400 to 1200 ft. The soil types were Armour series (fine-silty, mixed, 

active, thermic Ultic Hapludalfs) silt loam soil complex with 0 to 5% slopes, Braxton series 

(fine, mixed, active, thermic Typic Paleudalfs) cherty silty clay loam soil complex with 5 to 12% 

slopes, Braxton series (fine, mixed, active, thermic Typic Paleudalfs), silty clay loam soil 

complex with 5 to 12% slopes, Huntington series (fine-silty, mixed, active, mesic Fluventic 

Hapludolls) silt loam soil complex 0 to 6% slopes, Inman series (fine, mixed, active, thermic 



27 

 

Ruptic-Alfic Eutrudepts) and Hampshire series (fine, mixed, active, thermic Ultic Hapludalfs) 

silty clay loams soil complex with 4 to 12% slopes, and Maury series (fine, mixed, active, mesic 

Typic Paleudalfs) silt loam with 2 to 5% slopes (NRCS, 2019). 

Due to limited available space, the plots were divided into large paddocks and a smaller 

set of control plots. The large paddocks contained either corn silage or grain, grown with living 

mulch of either (“Durana” white clover (Trifolium repens L.) [WC]or with a mixture of crimson 

clover (“AU Sunrise” Trifolium incarnatum L.) and cereal rye (“Wintergrazer” Secale cereale 

L.) [CCR]). Paddocks were arranged in a complete randomized design (CRD) in triplicate, 

totaling 12 plots. Each large paddock had on average 0.7 ha-1. The small plots consisted of the 

control group and were grown in an adjacent area, each measuring approximately 6 x 16 m. In 

the control group, the two corn types were seeded in seedbeds without LM and replicated four 

times, totaling eight plots also in a CRD.  

Measurements and Management 

On Oct 18, 2018, the field was cleaned by spraying 2.25 kg ha-1 glyphosate (N-

(phosphonomethyl) glycine; Cornerstone Plus, Agrisolutions, St. Paul, MN) and 0.2 kg ha-1 of 

Fusilade (FusiladeDX, Syngenta, United Kingdom) in the entire area using a Bestway Field-pro 

III trailer-mounted sprayer (Janson). On Oct 23, 2018, WC was seeded at 11 kg ha-1 using a 

Great Plains 38-cm drill (Manufacturing Inc, Salina, KS). To ensure complete establishment of 

WC, the experimental period started in the fall of 2019.  

Crimson clover and cereal rye were seeded on Oct 23, 2019, and on Nov 28, 2020 at 11 

kg ha-1 and at 22 kg ha-1, respectively, using the same Great Plains 38-cm drill (Manufacturing 

Inc, Salina, KS). Lanes for corn seeding measured approximately 90-cm. These lanes were 



28 

 

created each year (May 15, 2020 and May 17, 2021) by spraying 0.45 kg ha-1 glyphosate (N-

(phosphonomethyl) glycine; Cornerstone Plus, Agrisolutions, St. Paul, MN) and 0.16 kg ha-1 

2,4-D ammine 4 (Loveland, Greeley, CO) using a 210 Redball 4-row and 8-row hooded sprayer 

(Wilmar, Benson, MN). The second spraying preceding corn seeding occurred on May 29, 2020 

and May 31, 2021, with 0.5 kg ha-1 of paraquat (Paraquat concentrate, Solera, Yuma, AZ), 0.62 

kg ha-1 of atrazine (Atrazine 4L, Drexel, Memphis, TN), 0.28 kg ha-1 of s-metolachlor (Charger 

Max, Agrisolutions, St. Paul, MN), and surfactant (Surf 80, Cannon packaging Co., Inc.) at 35 

ml ha-1 using a 210 Redball 4-row and 8-row hooded sprayer (Wilmar, Benson, MN). The entire 

area with the control plots were sprayed on May 28, 2020 and on May 17, 2021 with 1.3 kg ha-1 

of paraquat (Paraquat concentrate, Solera, Yuma, AZ) and surfactant (Surf 80, Cannon 

packaging Co., Inc.) 35 ml ha-1, using the RM 200 plot sprayer (AgSpray, Hopkinsville, KY). 

 Different relative maturity (RM) of each corn variety was used to minimize the harvest 

period between grain (RM 108) and silage (RM 120). On June 1 of 2020 and 2021, corn grain 

(Croplan 5887VT2P/RIB) and corn silage (Dekalb DKC67-44) were planted at 77,000 seeds per 

ha-1 with 90-cm spacing using a 4-row planter (John Deere, Lewisburg, TN). Urea (46-0-0) was 

applied at 36 kg ha-1 using a 3-m drop spreader (Gandy, Owatonna, MN) on June 8 and 26, 2020, 

and on May 3 and June 30, 2021. 

The corn silage was harvested on August 20, 2020, and on August 23, 2021, using a 900 

and T100 chopper (New Holland, Racine, WI) and a feeder mixer for material collection (Helm 

Welding, Lucknow, Ontario). The corn grain was harvested on September 16, 2020, and Oct 13, 

2021, using a plot combine (Almaco and Allis-chalmers Gleaner K2), the Ford F600 grain truck, 

and a service weigh wagon (Par-Kan). 



29 

 

Living mulch botanical composition, mass, and nutritive value 

Measurements to determine botanical composition (BC) and living mulch mass (LMM) 

were conducted simultaneously by clipping samples using a 0.1 m2 quadrat in 10 random spots 

within each paddock, randomly choosing corn lanes, totaling 120 samples. These samples were 

collected biweekly, from May 28 to Sept 24 in 2020, and from May 25 to Oct 15 in 2021. Each 

sample was then separated into LM (WC or crimson clover + cereal rye) and weeds and placed 

in a drier at 60°C to constant weight (~72 hr). The samples were weighed for determination of 

the dry matter (DM) LMM. All living mulch samples collected were then recombined after 

separation for BC, and ground in a Wiley Mill Grinder (Thomas-Wiley Laboratory Mill Model 4, 

Arthur H. Thomas Co., Philadelphia, PA) using a 2-mm screen for CP, NDF, and IVTDMD48 

analyses. Samples were then passed through a 1-mm cyclone mill (FOSS Cyclotec, Eden Praire, 

MN) to decrease particle size (McIntosh et al., 2022). Prior to analysis, the samples were 

individually placed in foil tins and dried for 30-min in a forced air oven at 55°C to allow 

consistent moisture content for scanning and decrease variability across results (McIntosh et al., 

2019). These samples were scanned in small ring cups on Near-infrared spectroscopy (NIRS) 

technology (Unity SpectraStar XL-R, Unity Scientific, Milford, MA). Unfermented Corn Silage 

(UC), Fermented Corn Silage (CS) and Haylage (HL) calibrations were provided and licensed by 

the NIRS Forage and Feed Consortium (NIRSC, Berea, KY) were used. The global and 

neighborhood statistical tests were monitored and analyzed for accuracy across all predictions 

with entire data set fitting the calibrations within the (H < 3.0) limit of fit and reported 

accordingly (Murray and Cowe, 2004). Units of measurement for nutritive analyses are presented 

at 100% dry matter (DM) across the entire data set. 



30 

 

Corn production and nutritive value 

Corn yield of silage and grain were determined by harvesting the two middle rows of 

each plot (both large paddocks and control plots). The length of the plot and numbers of rows 

were determined prior to harvesting, and the weight was recorded for determination of the 

production per ha-1. In both years, a sample from the harvested material of corn silage was taken 

from the bulk harvested, then dried and ground in a Wiley Mill Grinder (Thomas-Wiley 

Laboratory Mill Model 4, Arthur H. Thomas Co., Philadelphia, PA) using a 2-mm screen to be 

used later for the determination of the silage nutritive value of unfermented corn silage on the 

NIRS. Fermented silage was made by utilizing 18 x 20 cm air-tight Ziploc® bags, containing 

approximately 100 g of the harvested material, then pressed by hand to remove as much air as 

possible. Individual bags were placed in an extra-large space bag (Ziploc® Space Bag®). The 

bags were airtight and waterproof, and the air was removed by utilizing the vacuum in the one-

way valve to maintain an anaerobic environment. These bags were placed in a 55 L plastic bin 

covered by a 32 kg-1 sandbag to compress the samples and avoid external oxygen contamination. 

The plastic bin was then closed with a lid for 30 days before opening for determination of the 

nutritive value after dried. The samples were also ground in a Wiley Mill Grinder (Thomas-

Wiley Laboratory Mill Model 4, Arthur H. Thomas Co., Philadelphia, PA) using a 2-mm screen. 

All samples from both unfermented and fermented silage were scanned using the same 

methodology described for the LM nutritive value analyses on the NIRS, using the unfermented 

and fermented corn silage spectra for CP, NDF, Starch, and IVTDMD48. The corn grain was 

analyzed using the Ingratec Grain Analyser (FOSS North America, Inc., Eden Prairie, MN). The 

samples were best scanned when the amount averaged 470g. However, some samples, especially 



31 

 

in 2021, did not yield the optimum amount and.  Therefore, these were scanned twice for 

accuracy and the average results were utilized. 

Grazing 

Grazing was performed in spring and fall of 2020 and 2021 (Table 1.1). The stocking rate 

was variable among paddocks according to the forage availability of each large paddock. 

Variable stocking rate was conducted to avoid over or under-grazing and varied from 1 to 4 

animals (Table 1.1). Jersey cull cows were used, averaging 513 kg of body weight (BW) per 

paddock for each 28-d grazing period, and weighed immediately before and after entering the 

paddocks. Single-wire electric fences were used in each paddock and Bloat Guard® blocks 

(Sweetlix, Mankato, MN) were available to the animals to avoid bloating issues, while water was 

available ad libitum. To determine BC and LMM of the paddocks, ten 0.1 m2 quadrats were 

randomly clipped before and after the grazing period. The BC was determined by separating 

each LM sample into three categories: LM (WC or crimson clover + cereal rye), broadleaf weeds 

(BLW), and grass weeds (GW). Each sample was dried at 60ºC for 72-h, recombined, and 

weighed to determine the DM LMM.  

Economic analysis 

Annual production budgets for each LM treatment were developed based on The 

University of Tennessee Field Crop Budgets (Smith & Bowling, 2022). The values of seeding 

and machinery for WC planting were only accounted in the year of establishment, while CCCR 

costs of machinery and seeding were accounted every year. The cost of production includes the 

corn and LM seed, the fertilizer rate, herbicides, repair, maintenance, fuel, oil, and filter of the 

utilized machinery, operating labor and crop insurance as variable expenses, and capital recovery 



32 

 

and management labor as fixed expenses. The budget costs were used to determine the difference 

between the change in cost per ha of corn in LM and without LM ($ ha-1). The $ head-1 was 

determined by dividing the $ ha-1 by the stocking density in each plot (Table 1.1). Finally, the 

$/head/day was determined by dividing the $ head-1 by 28 grazing days. 

Statistical analysis 

Mixed model analyses of variance were performed to determine differences in least 

square means using the Fisher’s LSD. Data were analyzed by using the PROC GLIMMIX 

procedure in SAS (SAS 9.4, Cary, NC). The dependent variables related to LM were BC, LMM, 

and CP the fixed effects were sampling month, LM species, corn type, year and its four-way 

interaction with random effects of replication within LM species, and replication × LM species × 

sampling month × year, with repeated measures of sampling day. 

The corn production fixed effects were LM species, corn type, and its two-way 

interaction with the random effect of replication. For the grain, dependent variables of NV were 

starch, oil, and protein, and the fixed effects were LM species with the random effect of 

replication. For fermented and unfermented silage, dependent variables were CP, NDF, starch, 

and IVTDMD48; and fixed effects were LM species, year, and its two-way interaction, with the 

random effect of replication.  

The grazing study was separated by year (2020 and 2021) and season (fall and spring), 

given the differences of each grazing period in production and composition. The sampling dates 

were considered the beginning and end of the grazing period. The grazing study dependent 

variables were BC, LMM, and NV (CP, NDF, and IVTDMD48); and fixed effects were 

sampling date, LM species, and its two-way interaction with the random effect of replication. For 



33 

 

the ADG dependent variable, fixed effects were considered corn type, LM species, and its two-

way interactions with random effect of replication within corn type and LM species. All results 

were evaluated for significance at P < 0.05. 

Results and Discussion 

Weather 

In Oct. 2018, there was 8% less precipitation than the 30-year average; yet the 

temperature was 22% greater than the 30-year average. Meanwhile, in Oct. 2019, there was 

nearly 90% greater precipitation than the 30-year average, and 14% greater temperature than the 

30-year average. From June to September, in 2020 there was 20% greater precipitation compared 

to the 30-year average, and temperature was 2% greater than the 30-year average. From June to 

September 2021, precipitation was 60% greater than the 30-year average, and temperature was 

4% less than the 30-year average in 2021 (Table 1.2).  Although precipitation was greater than 

average through the growing season, in June there was a lack of precipitation following planting 

that greatly affected corn germination (Fig. 1.1). Germination of corn occurs between 2 to 6 

days, depending on the soil temperature (Wang & Fields, 1978);). During this time, the only 

precipitation between day 1 and 6 was a 20-mm on day four after planting. In total, there were 

only nine days of precipitation throughout the entire month, which affected the germination. 

Botanical composition (BC) 

There were differences between years for the BC of LM, but no differences between corn 

type (grain or silage) were found; therefore, results are reported by year while corn type was 

combined (Table 1.3). In 2020, there was a sampling month × LM species interaction (P < 

0.0001; Table 1.3). In May, the LM proportion was greater for CCCR, but it did not differ from 



34 

 

WC in Jun; whereas in the remaining months, WC showed greater LM proportion. Meanwhile, 

the exact opposite happened for weed proportion, which is expected given that crimson clover 

and cereal rye are short-lived annual species (Ingels et al., 1998). The mass accumulation of 

cereal rye can be great until the first week of June. In cover crop practices it is common to 

terminate crimson clover or cereal rye between May and June prior corn planting (Keene et al., 

2017; Vann et al., 2018). 

In 2021, the LM proportion did not differ between CCCR and WC in May, likely due to 

the late establishment of CCCR in 2020, reducing its overall presence in the field. Abdin et al. 

(1997) also observed that late seeding of grass species can lead to poor establishment when 

compared to early seeding. Due to the low soil temperatures that can occur in Nov and Dec, late 

seeding can delay seed germination (Wilson et al., 2013). In addition, water uptake at low 

temperatures damages seedling development (Mayer & Shain, 1974), which affects its 

establishment. Meanwhile, in Jun and Jul the LM proportion of CCCR was lower than WC, and 

in the later months (Aug, Sep and Oct) no differences were observed between LM treatments 

(Table 1.3).  

These later months of the growing season shows a shift in the overall BC of the stand, 

with predominantly weeds in all treatments. Clovers can be challenging when grown under high 

temperatures and dry conditions (Kendall et al., 1985); leading to decreases in overall proportion 

in the field. In a study conducted by Ehret et al. (2015), working with different shading levels to 

WC in agroforestry systems, it was concluded that WC responded negatively to shade for its 

productivity. The WC in our study was established in the fall of 2018, and as observed by Guy et 

al. (2020) the persistence of WC decreases during the third year after establishment, which led to 

the greater weed competition for WC plots in 2021 as compared to 2020 (Fig. 1.2). 



35 

 

Living mulch mass (LMM) 

The years were analyzed separately given the differences. In 2020, there was a LM × 

sampling date interaction (P ≤ 0.0001). No differences in LMM between WC and CCCR were 

observed in May and Jun (Table 1.4, Fig. 1.3). The greatest mass production was observed in 

Aug for CCCR and in May for WC (Table 1.4). As a C3 plant, CCCR and WC grows rapidly in 

spring and thrive under lower temperatures (Ball et al., 2007). The greater mass in Aug for 

CCCR reflect the increased proportion of warm-season weeds shown in CCCR treatments (Table 

1.3), such as crabgrass [Digitaria sanguinalis (L.) Scop] and especially pigweed (Amaranthus 

ssp.) (data not shown), which can reach heights up to 2-m (Steckel, 2007). These results reveal 

that annual winter species, such as crimson clover and cereal rye are better suited as cover crops 

rather than LM (Hill, et al., 2021; Xu et al., 2021; Andrews et al., 2020; Sanders et al., 2018). 

In 2021, there was only sampling month main effect (P < 0.0001) with less LMM in May 

and Jun, and greater mass in Sept and Oct (Table 1.4, Fig. 1.3). The lack of differences between 

CCCR and WC is attributed to the decreased persistence of WC, greatly affected by the intense 

management of the area and stressors from the previous corn presence. In addition, the CCCR 

mixture was planted in December 2020, whereas it was the third year after WC establishment, 

leading to a weakened stand. Meanwhile, in September, cool-season forages grow more 

vigorously, contributing to the increased LMM (Mullenix & Rouquette Jr, 2018). 

Crude Protein value of LM 

There was a LM × Year (P = 0.0351) and a LM × sampling month (P = 0.0091) 

interaction in the CP content of the LM species throughout the corn growing season (Table 1.5). 

The protein levels could influence the level of N available for corn uptake during WC 



36 

 

decomposition. For WC no differences were observed throughout the months, but in 2020 there 

were greater CP content than 2021, likely due to the greater WC content (Table 1.3). Meanwhile, 

the CCCR had greater CP in Jul and Aug, likely due to the presence of pigweed, that as a 

broadleaf weed, is also known to have great CP content, although is not consumed by animals. 

No differences were observed between 2020 and 2021 in CCCR, likely due to the similar 

botanical composition (Table 1.3). 

Corn production and nutritive value (NV) 

In 2020 and 2021, silage production was greater than grain production when they are 

compared in the same scale (Table 1.6). This occurs because when harvesting corn for silage, the 

entire plant is harvested and utilized, which increases the final weight of the harvested material. 

Meanwhile, in grain production, only the kernels are harvested, decreasing the total weight. 

Conventionally, the planting of corn at MTREC in Spring Hill, TN, occurs at the end of April, 

but in this study, both years, corn was seeded on June 1st, and delaying planting can lead to a 

reduction in corn yield (Hoffman et al., 1993). The lower production of 2021 is likely due to the 

decrease in precipitation after corn seeding compared to 2021 (Table 1.2). Given that 

precipitation greatly affects germination of seeds (Queiroz et al., 2019), plants were not able to 

establish and germinate properly since the peak of drought occurred in June (Table 1.2). In 

addition, the average ear height was 129-cm in 2020 as compared to 76-cm in 2021 (data not 

shown).  Ears were also much smaller and some plants did not produce kernels. 

According to the corn silage and grain variety tests in Tennessee (Sykes, et al., 2020 & 

2021), the average production in Spring Hill at MTREC had an average corn silage production of 

18.3 t ha-1 in 2020 and 11.4 t ha-1 in 2021. The same can be said about grain production, in which 



37 

 

the average production was 13.2 t ha-1 in 2020 and 10.3 t ha-1 in 2021. Therefore, the LM 

production of corn was lower than conventional systems. 

The lack of differences between CCCR, WC, and control in 2020 and 2021 reflects the 

great presence of weeds in all paddocks, especially after corn was established (Table 1.3, Fig. 

1.2). A study conducted by Sanders et al., (2018) showed that WC LM led to less corn 

production under drought than CCCR cover crops. Although in optimal conditions the WC can 

supplement the N required for corn growth, its decreased persistence in the third year did not 

confer any production advantages to the WC when compared to CCCR or control. 

The analysis of fermented and unfermented silage was different between years, and due 

to the lack of kernels in 2021, the samples was analyzed as haylage in 2021, and corn silage in 

2020. There was an interaction between LM species × year (P = 0.0005) for CP content of 

unfermented silage, with greater CP observed in WC in 2020 (Table 1.7). These results are 

expected, given the greater proportion of WC (Table 1.3). WC has high CP content, therefore 

increasing the overall nutritive value of the feed (Javanmard et al., 2009). The control plots did 

not differ from CCCR, and both treatments were composed mainly of weeds during the course of 

corn production. Interestingly, there were no differences in the NDF content among treatments, 

and these results could be attributed to the overall composition of the sward. Most weeds found 

in both paddocks and control plots were crabgrass and broadleaf weeds, which are known for 

low NDF content, therefore contributing to the lack of differences in the NDF of unfermented 

silage. Meanwhile, starch content was greater in 2020 than 2021, but it did not differ among 

treatments each year. The starch is present in the endosperm of the corn grain (Rooney & 

Pflugfelder, 1986), and given the greater ear production in 2020, the starch content was expected 

to be higher. The IVTDMD48 was greater in 2021 than 2020 (P = .0001; Table 1.7), and also no 



38 

 

differences were observed among treatments each year. The WSC (water soluble carbohydrates) 

are responsible for aiding the fermentation in haylage and silage, and the WSC are greater in 

haylage than silage (Müller et al., 2016) which affects the digestibility of the feed. For this 

reason, 2021 had greater digestibility, due to the greater amount of forage material in the silage. 

Meanwhile, the fermented silage only showed differences between years for NDF, starch, 

and IVTDMD48 (Table 1.7). The NDF was greater in 2021 than 2020, likely due to the weed 

composition in the harvested material, while starch and IVTDMD48 had greater values in 2020, 

due to greater ear presence in the fermented sample. The endosperm of corn increases the 

digestibility of the feed (Rooney & Pflugfelder, 1986) and, when fermented, its sugars are 

utilized during the process of fermentation towards stability (Kung, 2018). The differences in CP 

content are more difficult to observe since nearly 60% of the protein is utilized during the 

process of fermentation (Woolford & Pahlow, 1998), and these results are reflected in our study. 

The grain nutritive value showed a greater starch content in 2021 than 2020, likely due to 

the concentration of the component in less kernels. Greater protein content in WC (Table 1.8). A 

study conducted by Miao et al., (2006) working with N levels in corn production, showed an 

increase in protein content with increased N, and since legumes are a source of N to the 

companion crops, these results were expected. The lack of differences of starch and oil showed 

the stability and consistency of these components. Singh et al., (1996) showed that even 

locations did not affect the starch content of the kernel. Although the oil content can vary within 

different hybrids (Singh et al., 2000), in our study there were no differences between corn grain 

and silage, therefore the lack of differences in starch and oil content was expected. 



39 

 

Grazing 

1. Botanical composition (BC) 

In spring 2020, the LM proportion was greater in CCCR than WC, and a greater 

proportion of broadleaf weeds (BLW) were observed in WC (Table 1.9). These results are 

expected, since WC was slowly starting to grow during spring giving BLW an opportunity to 

grow, while CCCR (a winter annual mixture) was thriving and outcompeting weeds. In a study 

conducted by Adhikari et al. (2018), cereal rye affected the seedling establishment of alfalfa due 

to its allelopathic effects, which could explain why crimson clover had lower proportions (Fig. 

1.3).  Yet, the BC between the beginning and end of the grazing period did not differ (Table 1.9), 

likely because of the vigorous spring growth of C3 species (Ball et al., 2007). Similarly, during 

spring of 2021 greater LM proportion was observed in CCCR as compared to WC, although 

there were less LM in CCCR at the end of the grazing period. The CCCR were seeded in 

December 2020, and WC established in the fall of 2018, which could reflect the weakened stand 

to support animal pressure. The BLW remained greater in WC similar to results observed in the 

spring of 2020. An interaction between sampling date and LM species in the grass weeds (GW) 

proportions was observed. The CCCR had greater GW proportion at the end of the grazing 

period (Table 1.9), likely because after the annual forages were grazed, the weeds were able to 

establish and compete for resources. 

In the fall of 2020, LM proportion was greater in WC than CCCR (Table 1.9) due to the 

WC regrowth that occurred in the fall (Mullenix & Rouquette Jr, 2018) after corn harvest. In 

addition, BLW were greater in WC than CCCR, and the GW proportion was inversely related to 

the BLW composition in the field (Table 1.9). Meanwhile, in the fall of 2021, no differences 

were observed for all variables (Table 1.9). In addition, GW grew exponentially in the fall on 



40 

 

WC as compared to the other grazing periods, due to the low competitive strength of WC in the 

third year of establishment (Guy et al., 2020). 

2. Living mulch mass (LMM) 

Given the differences observed between corn types and between years, the analyses were 

conducted separately (Table 1.10). In spring 2020, there were no differences in LMM between 

the beginning and end of the grazing period in corn grain or in silage paddocks, yet greater LMM 

was observed in CCCR than WC in silage paddocks (P = 0.0494; Table 1.10), likely due to the 

greater LM proportion observed in the BC (Table 1.9). In spring 2021, the grain paddocks had 

greater mass in the beginning of the season than the end (P = 0.0125), and greater LMM was 

observed in WC (P = 0.0145; Table 1.10), which follows the finding of the BC, where greater 

BLW proportion was observed in WC, increasing the LMM accumulation (Table 1.10). 

However, these findings were not seen in the silage paddocks, where no differences were found 

(Table 1.10). When harvesting the silage paddocks, the entire plant is removed of what would 

otherwise become organic matter which assists with plant regrowth. A study by Bertora et al. 

(2009) showed that maize straw can increase the C in the soils, and subsequently forages can 

remove it for its growth. 

In the fall of 2020, there was a main effect of LM species (P = 0.0001, Table 1.10) in 

grain paddocks, with greater LMM in CCCR, and these results were attributed to the greater GW 

content (Table 1.9). Meanwhile, there was a sampling date × LM species interaction (P = 

0.0404) for silage paddocks, with less LMM observed for WC at the end of the grazing period 

(Table 1.10). Although these results are not a direct reflection of the BC, it is possible to assume 

that WC was getting ready for dormancy, since the grazing ended in the last week of November. 



41 

 

In the fall of 2021, there was a sampling date × LM species interaction (P = 0.0321) in 

grain paddocks, with the greatest LMM observed in WC at the beginning of the grazing period. 

The CCCR paddocks did not differ in the same period and treatment, likely due to the amount of 

corn residue in the field, which remained constant throughout the grazing period. There was a 

main effect of sampling date in silage paddocks (P = 0.0171), with a decreased LMM at the end 

of the grazing period for both CCCR and WC (Table 1.10), which is expected after the forage is 

consumed by the animals. 

3. Nutritive Value (NV) 

No differences between grain and silage were observed in spring 2020 and 2021, and fall 

2020, therefore the analyses for these three periods were combined (Table 1.12). In spring 2020, 

the CP was greater in WC both in the beginning and end of the grazing period, results that are 

expected in legume monocultures. The NDF content showed the opposite pattern to CP 

concentration, which is expected. For IVTDMD48, there was also greater digestibility in the 

legume monoculture (WC) as opposed to mixed swards (CCCR) due to the greater presence of 

CP.  

In spring 2021, no differences in CP were observed (Table 1.12). Most species present in 

the CCCR paddocks, although weeds, were immature at vegetative stage and had similar CP 

content as those of legumes at the same stage of maturity. There was a main effect of sampling 

date (P = 0.0078) and LM species (P = 0.0329) for NDF content (Table 1.12). Greater fiber 

content is expected in CCCR versus WC since there are greater structural components required 

for the growth and development of cereal rye (Brink & Fairbrother, 1992). Meanwhile at the end 

of the grazing period, greater NDF was observed, due to the consumption of leaves, which have 

lower fiber content as opposed to the stubble left behind (Griggs et al., 2007). Interestingly, 



42 

 

greater IVTDMD48 was observed in CCCR, likely due to the vegetative presence of the weeds 

as compared to WC. 

In the fall of 2020, there was a main effect of sampling date and LM species in CP 

(sampling date: P = 0.0032; LM: P = 0.0047), NDF (sampling date: P = 0.0004; LM: P = 

0.0033), and IVTDMD48 (sampling date: P <0.0001; LM: P = 0.0024). Greater CP was 

observed in WC as compared to CCCR, leading to lower NDF and greater IVTDMD48. Also, 

greater CP, greater IVTDMD48, and lower NDF were observed in the beginning of the grazing 

period as compared to the end (Table 1.12). The results are expected because when fiber content 

is reduced, it usually indicates high digestibility (Cherney & Parsons, 2020). 

In the fall of 2021, there was the main effect of corn type, therefore the analysis was 

conducted separately. For grain paddocks, there was a main effect of sampling date (P = 0.0069) 

with greater CP in the beginning of the grazing period. Also, there was greater CP content for 

CCCR than WC paddocks (P = 0.0090, Table 1.12). These results reflect the increase in weed 

proportion in WC paddocks (Table 1.9). The IVTDMD48, was greater in the beginning of the 

grazing season, which is expected because after removal of leaves by grazing, the stems are left 

behind, which are less digestible (Nave et al., 2014). For silage in the fall of 2021, there were no 

differences in CP and NDF content, reflecting the homogeneity of the forage composition in the 

plot (Table 1.9). The IVTDMD48 showed a sampling date (P = 0.0187) main effect with greater 

digestibility in the beginning of the grazing period than the end (Table 1.12) similarly to the 

grain paddocks. 

4. Average Daily Gain (ADG) 

Differences between corn types and grazing periods were significant; therefore, the 

analyses were done separately. In spring 2020, there was a LM species × corn interaction (P = 



43 

 

0.0272), and the ADG in WC was greater in silage than grain, while no differences were 

observed in CCCR (Table 1.13). A study conducted by Schaefer et al., (2014) observed that WC 

can positively influence animal performance through its greater NV, which is confirmed by this 

study. In spring 2021, there was only the main effect of LM species (P = 0.0052) where greater 

ADG was observed in WC than CCCR due to the greater LMM available (Table 1.10). Mckee et 

al., (2017) also observed that animals grazing in legume or grass paddocks containing cereal rye 

led to lower ADG due to legume selectivity. In the fall of 2020, the main effect of LM species (P 

= 0.0304) also showed greater ADG for WC, although lower LMM was recorded (Table 1.10); 

the WC had greater CP, and it was more digestible than CCCR (Table 1.12), which affected the 

ADG. Finally, in the fall of 2021, no differences were observed, which was reflected by the lack 

of differences in nutritive value of the feed (Tables 1.12, 1.13). 

From these observations, it is important to observe that nutritive value plays an important 

role in ADG during the fall, while LMM plays a greater role in the spring. Cool-season forage 

species have greater growth in the spring (Ball et al., 2007), and the NDF tends to be lower than 

in the fall, which affects the digestibility. The lack of differences in ADG in the fall of 2021 

showed that the lack of BC differences (Table 1.9) directly affected the weight gain of the 

animals. Also, the ADG tended to decrease in WC from spring 2020 as compared to later grazing 

periods. This is likely due to decreased persistence of these species (Guy et al., 2020; Schaefer et 

al., 2014). In addition, the average NDF had > 70% content in the fall of 2021, which greatly 

affects the intake and digestibility of the feed (Cherney & Parsons, 2020; Buxton, 1996), and 

consequently the ADG. 



44 

 

Economic analysis 

The WC is a perennial forage; therefore, the cost of production is different from 2020 to 

2021. Meanwhile, CCCR and conventional corn production remained the same across the years 

(Table 1.14). Profits were greater in corn grown in WC LM in 2020, likely due to the added N 

from WC, leading to a $683.74 higher profit than corn in conventional systems. However, CCCR 

did not result in higher profits when compared to conventional systems ($252.00 less profit in 

2020). Although a similar pattern was observed in 2021, the production and outcomes were 

much lower due to the poor establishment of corn, therefore all treatments were not profitable. 

For corn grain, similar results were observed, with greater profit in corn with WC LM in 2020, 

but no profits observed in 2021 (Table 1.14).  

The decrease in corn production in 2021 is attributed to the low precipitation after 

seeding, which affected its germination and development. Except for grain in WC in 2021, the 

differences in cost by adopting LM are greater than conventional corn systems (Table 1.14), yet 

it is possible to conclude that the use of LM is beneficial in WC systems rather than CCCR based 

on the profits. The grazing component diluted the additional costs of production when the system 

is adopted. Although the $/head/day costs are dependent on the stocking density adopted, the 

highest cost of grazing was $2.22 for WC in the Spring of 2020 (Table 1.15). Therefore, if 

feeding costs of cull cows are above the calculated values (Table 1.15), it is recommended that 

LM is adopted for greater returns and land use efficiency. 

Conclusions 

The use of WC as LM leads to a reduction in weed pressure and increased corn 

production compared with crimson clover-cereal rye mixtures. Also, the use of a perennial 

forage decreases the need for annual planting. Although CCCR produced greater LMM in the 



45 

 

first week of sampling, the use of cereal rye would be more beneficial as a cover crop, due to its 

short-lived morphology. In normal weather conditions corn grain and silage produced similar 

yields, but having WC allowed a greater overall production, likely due to the added N. When 

irregular precipitation patterns are observed, grain production is more affected than silage; 

therefore, irrigation might be necessary to ensure germination and development of corn 

seedlings. WC as a living mulch also showed positive applications in grazing systems with 

greater LMM and NV in most instances. Although cull cows were utilized for grazing, a slight 

weight gain was observed in animals grazing WC. Further studies using steers are warranted to 

help advance the use of LM in the Southeastern U.S. The profit is greater in silage than grain and 

greater in WC LM systems than CCCR or conventional systems when the weather patterns are 

favorable for corn growth, otherwise irrigation might be necessary. In addition, when feeding 

costs are greater than $2.22 head/day, LM systems are a good strategy for grazing operations. 

 



46 

 

Appendix 

Table 1-1: Grazing period, forage sampling dates and number of animals used on paddocks of 

corn growing with living mulch in 2020 and 2021 in Spring Hill, TN 
  Forage Sampling Grazing Period 

Year Season Enter Exit Enter Exit 

2020 
Spring 30-Mar 1-May 1-Apr 30-Apr 

Fall 26-Oct 24-Nov 28-Oct 24-Nov 

2021 
Spring 5-Apr 3-May 5-Apr 3-May 

Fall 18-Oct 19-Nov 20-Oct 17-Nov 

                                                        Number of animals    
  2020 2021 

Treatments Spring Fall Spring Fall 

Corn grain 

†CCCR 

2 3 2 3 

1 3 3 3 

2 3 2 3 

WC 

2 3 3 3 

1 3 3 3 

1 3 3 3 

Corn silage 

CCCR 

4 3 3 3 

3 3 3 3 

3 3 3 3 

WC 

1 3 3 3 

1 3 3 3 

1 3 3 3 

†CCCR, Crimson clover- cereal rye mixture; White clover, WC. 

  



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Table 1-2: Precipitation (mm) and temperature (ºC) from 2018 to 2021 field preparation and 

growing season, and 30-year average in Spring Hill, TN 

Month 30-year avg. 2018 2019 2020 2021 
 Precipitation (mm) 

Jan 116.3 34 162.6 172.2 77 

Feb 129.6 273.3 267.5 253 117.3 

Mar 136.6 171.2 102.1 206.5 315.2 

Apr 123.6 160.8 158.8 126.7 23.9 

May 129.6 90.4 81.3 106.7 142.7 

Jun 113.2 116.1 209.3 106.4 93.2 

Jul 112.5 41.7 48 168.9 127 

Aug 92.8 56.4 53.1 125.5 260.9 

Sep 112.7 234.7 19.3 126.7 187.2 

Oct 104.7 96.8 198.4 127.8 119.9 

Nov 101.9 105.4 143.8 44.7 44.7 

Dec 147.4 180.3 187.7 146.1 59.2 

 Temperature (ºC) 

Jan 3