Evaluation of Sensor Based Nitrogen Application in Producers Fields.

Oklahoma State University research and extension programs have been educating producers on the use of N-Rich strips (NRS) and the Sensor Based Nitrogen Rate Calculator (SBNRC)in winter wheat production  since 2000.  The SBNRC utilizes optical sensor readings collected from the N-Rich strip and neighboring farmers practice to predict yield and estimate response to nitrogen to derive a top-dress N rate.    The majority of the data used in extension was collected from small plot research trials.  During the 2008-09 and 2009-10 winter wheat cropping seasons large scale trials where established in producers fields across the state of Oklahoma to evaluate the use of the SBNRC.  Each trial consisted of 3 treatments replicated 3 times with a plot size of 20m x 133.33m.  The three treatments implemented were 1) Pre-plant fertilization only, 2) Producers planned top-dress (PR), and 3) SBNRC flat rate.   The producers applied their typical pre-plant fertility program and sowed the entire field as one unit.   OSU applied the N-rich strips after emergence and top-dress N prior to Feekes growth stage 5.  At maturity the trials were harvest by the producers and grain was collected in a weigh wagon to record yield.    Over 15 site years the SBNRC applied an average of 43 kg N ha^-1 while the PR applied 65 kg N ha^-1.  The SBNRC average yield of 3441 kg ha^-1 was 6 kg higher than the PR.  The SBNRC yields were significantly higher than the PR at four locations and significantly lower in four  with the remainder showing no significant difference.  Over the site years grain N concentration was higher in the PR two times and SBNRC three times.  This project documented the use of the SBNRC and NRS could both reduce N while maintaining yields and increase N rate when higher yield potential was possible.