Corn Uptake and Soil Accumulation of Nitrogen: Management and Hybrid Effects

Abstract

AbstractInefficient use of fertilizer N by corn (Zea mays L.) can result in the accumulation of excessive amounts of NO‐3 subject to leaching losses in the crop root zone. The fate of fertilizer N as influenced by N rate, nitrapyrin [2‐chloro‐6‐(trichloromethyl)pyridine], and corn hybrid was evaluated in a 3‐yr study with sprinkler‐irrigated corn. Variables were fertilizer‐N rate (75, 150, and 300 kg N/ha); nitrapyrin (0 and 0.5 kg/ha); and corn hybrid (Pioneer hybrids 3377, 3475, and 3551). Nitrogen was applied as late‐sidedressed (V6‐V9) NH3. The fate of fertilizer N was evaluated by measurement of apparent fertilizer‐N uptake (AFU), form of N in the fertilizer band prior to and following anthesis, and accumulation and distribution of N in the soil profile. There were no significant effects of hybrid on AFU across years, and no significant hybrid × nitrapyrin interactions on AFU. Nitrapyrin significantly reduced AFU across N rates and hybrids in 2 of 3 yr. Nitrate‐N concentrations in the fertilizer band, in the presence of nitrapyrin, were reduced prior to anthesis in 1986. Higher NH+4‐N concentrations in the fertilizer band in 1986, as well as trends towards higher total inorganic‐N concentrations all 3 yr following anthesis, suggest mineralization of temporarily immobilized fertilizer NH+4. Reduced AFU in the presence of nitrapyrin in 1986 and 1987 indicates reduced availability of fertilizer N consistent with a temporary immobilization process. Nitrate accumulation in the soil to a depth of 1.8 m after three growing seasons indicates a trend toward less NO‐3 accumulation where nitrapyrin was applied at N rates of 75 and 150 kg/ha. Nitrate concentrations in the soil at a depth of 1.8 m were significantly greater at the 150 and 300 kg N/ha rates, compared with the 75 kg N/ha rate or unfertilized soil, indicating probable movement of fertilizer N below the 1.8‐m depth at the higher rates. These results indicate that nitrapyrin should not be applied with NH3 at late‐sidedress time for this soil.