Nitrogen Rate and Environmental Effects on Irrigated Corn Yield in Southeastern North Dakota

摘要

Corn for grain has a significant economic and environmental impact in irrigated crop rotations on sand plains in Southeastern ND. The current algorithm for fertilizer N recommendation calls for 1.2 Ib/ac of soil puls ferttilizer N for each bu/ac of yield goal. Research in Wisconsin and Kansas has shown that optimum economic N rated for specific soils determined from long term studies more accurately predicts N requirement than yield goal. Five corn N rate data bases, comprised of 19 site years during the period from 1971 to 1995 conducted on irrigated sand plains in Southeasttern ND, were analyzed to determine the efficacy of optimum economic N rates versus yield goal based N rates.Maximum yield in cool and normal seasons, described in regression fited curves, were attained at 171 and 187 lb/ac of fertilizer N, respectively, despitte a 79 bu/ac difference between them. The optimum economic N rate ranged from 163 lb N/ac at a low corn price to N cost rattio of 6.67(dollar 2.00 /bu corn, dollar 0.30/lb N ) to 176 lb N/ac at a high corn price to N cost ratio of 15.00(dollar 3.00/bu corn, dollar 0.20/lb N). Despite a maximum yield of only 103 bu/ac in cool seasons, the optimum economic fertilizer N rate was 129 lbN/ac at the low corn price to N cost ratio. Yield in bu/ac was a poor indicator whereas optimum economic N rate was a good indicator of N requirement in irrigated sand plains in Southeastern ND.