On-Farm Nitrogen Rate Trials Calibrate Grower Expectations

On-farm nitrogen rate trials were established on three cotton farms in 2011 and repeated in 2012. The farms are located in the Mississippi alluvial plain, the Macon Ridge loess deposits, and the Red River alluvial plain on non-irrigated fields. Three nitrogen rates were utilized - the grower standard rate, the standard rate plus 30 pounds N/acre, and the standard rate less 30 pounds N/acre. Nitrogen was applied by knifing in a liquid 30-0-0-2S urea ammonium nitrate-based solution at sidedress approximately 30 days after planting. Each rate was replicated three times in the trial, and each plot was field length. Pre-application soil samples were extracted to ensure no other nutrient was a potentially limiting factor. Greenseeker NDVI data were collected at first bloom and 30 days after first bloom. Yields were recorded by yield monitor calibrated with a weigh-scale equipped boll buggy. 2011 was characterized by drought, while 2012 was characterized by timely rainfall. Results indicated that in 2012 the yield from the farmer standard nitrogen rate was significantly greater than the yield from the lower nitrogen rate, but that increasing the nitrogen rate did not significantly increase cotton lint yield but there was a slight suppression of lint yield. Affects of electrical conductivity zones and soil texture zones will be discussed.