Date of Award

5-2011

Degree Type

Thesis

Degree Name

Master of Science

Major

Biosystems Engineering Technology

Major Professor

Hubert J. Savoy

Committee Members

Brian Leib, John Wilkerson, Joann Logan

Abstract

A nitrogen fertility study with Vaughn’s hybrid bermudagrass conducted on a Crider silt loam soil (fine, silty, mixed, active, mesic Typic Paleudalfs) over three (3) years (2008-2011) at the Highland Rim Research and Education Center near Springfield, Tennessee is evaluated in this manuscript. Nitrogen applications are evaluated in both irrigated and non-irrigated plots at five (5) different application rates: 0, 56, 112, 168, and 224 kg N ha-1. These rates are applied beginning in late April, and three (3) additional times upon harvests occurring in June, July, and August. Irrigation plots receive enough water to bring total weekly water up to 2.24 cm/plot whenever rainfall is less than that amount. Normalized difference vegetative index (NDVI) measurements are collected mid harvest and on harvest dates to investigate new nitrogen status indicators between Vaughn’s hybrid bermudagrass yields. Plant tissue samples are collected at harvest. Soil samples are collected mid harvest to investigate soil nitrate nitrogen and its relationship with bermudagrass yields.

The results of the study show irrigation has no effect on yields during the period of this study. There is a significant effect resulting from the interaction between month and nitrogen application on yield. Investigation of this interaction reveals two (2) distinct periods of production potential during the growing season. A low to medium yielding period produces an average harvest yield maximum of 3.14 Mg ha-1. A medium to high yield period produces an average harvest yield maximum of 5.4 Mg ha-1. Based on an analysis of variance and mean separation, a nitrogen rate of 56 kg N ha-1 rate is recommended for harvests occurring during the low to medium yielding period, and a nitrogen rate of 113 kg N ha-1 is recommended for those occurring during the high to medium yielding period. NDVI is highly correlated with yield on date of harvest. The results also show NDVI is correlated with mid-harvest yields also, which suggests a possible development of using NDVI as a mid harvest nitrogen status indicator. The results show soil nitrate is not correlated with yield, but did indicate accumulation in the soil as the growing season progressed.

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