FARM EXTENSION ACTIVITIES
Corn N Rate Studies in Producer Fields
The effect of fertilizer nitrogen-rate on yield and plant-soil nitrogen relationships was studied in six irrigated corn fields (fields p-v), on two farms at Oakes ND, in 2008. The goal in this study was to compare the results of the field N rate to a strip within the each field where 40 lb/acre extra N was applied. Some additional N rates higher than the field rate were also tested. Therefore N rates above the field rate ranged from 30 to 105 lb N/ac. These strips and the field rate were then compared by yield, soil nitrate-N, chlorophyll meter readings at silking, end of season stalk nitrate-N test, grain protein, starch, and oil content as well as test weight. The nitrate-N content in mature corn stalks was determined on 8-inch stalk sections taken at 6 inches above the soil surface. Stalk test criteria states that N is deficient at nitrate-N contents of 0-250 ppm, marginal at 250-700 ppm, adequate at 700-2,000 ppm and excessive when over 2,000 ppm The return to fertilizer N applied above the lowest N rate for each field was also calculated for a corn price of $3.50/bu and a fertilizer N price of $0.55/lb of actual N.