EFFECTS OF SPRING N APPLICATION ON YIELD AND N CONTENT OF FOUR WINTER WHEAT CULTIVARS

Abstract

The effects of spring N fertilization on yield and N content of grain were studied over a 3-yr period on four cultivars of winter wheat (Triticum aestivum L.) with three rates of fall-applied fertilizer. No increases in grain yield, grain N concentration or grain N yield were observed when fall-applied N was increased from 22 to 44 kg/ha, or when fall-applied K was increased from 37 to 74 kg/ha. Increasing the rate of spring-applied N from 0 to 33 kg/ha increased grain yields by 0.84 metric ton/ha with no increase in grain N concentration. Increasing the rate of N application from 33 to 67 kg/ha increased grain yield by 0.59 metric ton/ha. This was accompanied by a 0.14% increase in grain N concentration. Increasing the rate of N application from 67 to 100 kg/ha increased grain yields by only 0.14 metric ton/ha. This was accompanied by an increase of 0.21% in grain N concentration. The increase in grain N yield was similar with each increment of N application and averaged 0.40 kg N in grain per kg fertilizer N applied in the spring. Larger increases in yield and smaller increases in grain N concentration were generally obtained with the high yielding, low N cv. Yorkstar than with the low yielding, high N cv. Richmond. The effects of N on Genesee and Talbot were intermediate.