Tuesday, November 6, 2007
193-3

Can Spectral Indices Predict Forage Yield in Winter Pasture.

Jagadeesh Mosali, Billy Cook, Shawn Norton, Frank Motal, and Jeffrey Ball. The Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73402-2180

Nitrogen(N) fertilizer recommendations currently based on yield goal for forage production in rye without considering the temporal and spatial variations in soil to supply N. Current study is taken up to develop a nitrogen fertilizer optimization algorithm using in-season spectral measurements collected in early growth phase. Reflectance measurements are taken to calculate normalized difference vegetative index (NDVI)) using a GreenSeeker Hand Held optical reflectance sensor(NTech industries, Ukiah, CA). One experimental site was established to investigate at Burneyville (Minco fine sandy loam, Udic Haplustolls), Oklahoma in the year 2006. Spectral reflectance measurements were taken every 2 weeks and the forage is clipped for dry matter yields. In-season estimate of yield (INSEY) which is NDVI taken in-season divided by cumulative growing degree days is correlated with the forage clippings and an algorithm was developed to predict the fertilizer that is needed by the crop for that particular harvest. 48% of variability in yield was explained by the INSEY equation in estimation of yield. This work has the potential to increase the N uptake and increase the NUE and decrease the environmental concerns.

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