Characterizing Most Profitable Nitrogen Application Rates and Yields in Hybrid Bermudagrass Through The Use of Tissue Sampling, Soil Sampling, and NDVI
A nitrogen fertility study with Vaughn’s hybrid bermudagrass was 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. Nitrogen applications were 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 applications were applied beginning in late May, and three (3) additional times upon harvests occurring in June, July, and August. Normalized difference vegetative index (NDVI) measurements were collected mid harvest and on harvest dates to investigate new nitrogen status indicators between Vaughn’s hybrid bermudagrass yields. Soil samples were collected mid harvest to investigate soil nitrate nitrogen and its relationship with bermudagrass yields.
The results of the study revealed irrigation had no effect on yields. There was a significant effect resulting from the interaction between month and nitrogen application on yield. Unlike previous studies, this experiment investigated this interaction and found two (2) distinct periods during the growing season. A low to medium yielding period (occurring during June and September) produced an average yield maximum of 3.14 Mg ha-1. A medium to high yield period (occurring during July and August) produced an average yield maximum of 5.4 Mg ha-1. An annual rate of 148 kg N ha-1 rate is recommended for the low to medium yielding period, and an annual rate of 156 kg N ha-1 rate is recommended for the high to medium yielding period. The savings from this analysis results in a decreased use of nitrogen by as much as 25%. NDVI was highly correlated with yield on date of harvest. NDVI was also related with yields 10-14 days after harvest, which suggests a possible development of using NDVI as a mid harvest nitrogen status indicator. Soil nitrate was not correlated with yield, but did indicate accumulation in the soil as the growing season progressed. Lack of correlation may be due to a poor yield response observed in 2010.