|Stone, Kenneth - Ken|
|ANDRAE, JOHN - Clemson University|
|BUSSCHER, WARREN - Retired ARS Employee|
|Strickland Jr, Ernest|
Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2014
Publication Date: 3/1/2015
Citation: Bauer, P.J., Stone, K.C., Andrae, J.G., Busscher, W.J., Millen, J.A., Strickland Jr, E.E., Evans, D.E. 2015. Water deficit and nitrogen fertility effects on NDVI of 'Tifton 85' bermudagrass during regrowth. Applied Engineering in Agriculture. 31(1):97-102. https://doi.org/10.13031/aea.31.10731.
Interpretive Summary: A better understanding of how bermudagrass regrowth is influenced by production inputs is needed to design protocols for using remote sensing to precision apply nitrogen fertilizer to hay fields in the southeast US. We conducted this field experiment to determine how irrigation and nitrogen rate influence bermudagrass regrowth. We measured normalized difference vegetative index (NDVI) with commercially available sensors that can be mounted on fertilizer application equipment. We found that nitrogen fertilizer rate and irrigation (when rainfall was lacking) generally increased NDVI. In two of three evaluations, measuring NDVI of the grass nine days into regrowth provided a good prediction of forage yield at the end of the four-week cutting cycle. These results will be used by researchers developing bermudagrass hay and pasture management practices to increase fertilizer nitrogen use efficiency and thereby reduce potential losses of nitrogen fertilizer to the environment.
Technical Abstract: A better understanding of how bermudagrass (Cynodon spp.) regrowth is influenced by production inputs will aid in advancing precision management in the southeast US. The objective of this two-yr study was to evaluate how irrigation and nitrogen influence bermudagrass regrowth. Normalized difference vegetative index (NDVI) data were collected in an experiment evaluating two harvest schedules (four or eight weeks), four rates of irrigation (0, 4.2, 8.4, or 12.5 millimeters (mm) of water when tensiometers at 30 centimeter soil depth in the 12.5 mm treatment averaged -30 kilopascals), and three rates of nitrogen (season total of 168, 336, and 504 kilograms nitrogen per hectare). Both irrigation and nitrogen influenced NDVI of bermudagrass during the regrowth periods of both the four- and eight-week harvest schedules, but there were no interactions between irrigation and nitrogen. As was expected, regrowth (as measured by NDVI) in response to irrigation was dependent on the timing and duration of rain-free periods within the regrowth periods. Generally, NDVI increased with increasing nitrogen rate at most sampling dates. In two of three 4-week harvest schedules when no nitrogen was applied at the beginning of the regrowth period, NDVI at nine days after cutting was a good predictor of yield (correlation coefficients of 0.55 and 0.76). Further refinement of using NDVI for precision N management in bermudagrass in short harvest cycles will require determining how late in the regrowth period nitrogen can be applied and a quantification of the amount of regrowth necessary for consistent estimates of yield.