Adjusting In-Season Nitrogen Fertilizer Rate for Wheat with Real-Time Sensing.

Real time sensing of plant nitrogen status can be a useful tool in managing nitrogen inputs.  Very good correlations have been observed between remotely sensed crop nitrogen status, in-season nitrogen fertilizer recommendations and yield.  However, these other wheat growing regions do not match the high input, high yield potential conditions for wheat production in the southern San Joaquin Valley.  The objectives of this project were to assess the reliability of remotely sensed non-destructive plant nitrogen measurements to wet chemistry data from sampled plant tissue and develop in-season nitrogen recommendations based on remotely sensed data for improved nitrogen use efficiency.  Instruments used were Minolta SPAD 502, Field Scout CM 1000 NDVI and Opti-Sciences CCM-200 plus.  Very good correlation was observed (R²=0.85) for the SPAD meter readings and V5 nitrogen concentration.  In-season nitrogen fertilizer rate recommendations were well correlated to SPAD meter readings (R²=0.70) and CCM-200 (R²=0.75).