Defoliation and Fertilizer Nitrogen Effects on Nitrate‐nitrogen Profiles in Maize1

Abstract

AbstractCorn (Zea mays L.) vegetative tissue remaining after hail damage is often utilized for forage. Environmental stresses may cause levels of nitrate‐nitrogen (NO−3‐N) in plant tissue that are toxic to ruminants. This study was conducted to determine the effect of leaf blade removal (simulated hail damage) and N fertilization of the soil on the NO−3‐N profile of corn fodder.Leaf blade removal of 0, 50, 100% was imposed at tasseling on the corn hybrid ‘Dekalb XL45A’ grown in soil fertilized with either 115 or 230 kg N/ha. Plants were sampled approximately weekly for 6 weeks after defoliation.Both stalk and total fodder NO−3‐N concentration increased as either level of defoliation or N rate increased. Stalks of nondefoliated plants contained up to over 4,500 ppm (dry matter basis) NO−3‐N while stalks of plants having 50 and 100% of the leaf blades removed contained up to 5,000 and 5,500 ppm NO−3‐N, respectively.When completely defoliated, fodder NO−3‐N concentration was as high as 1,900 ppm for corn receiving 115 kg N/ha. Fodder of 100%‐defoliated plants receiving 230 kg N/ha contained as much as 2,300 ppm NO−3‐N.These results suggest that corn fodder NO−3‐N concentration increases due to the defoliation caused by hail. Thus hail damage to corn fodder may increase the chances of NO−3‐N toxicity to animals, especially when high rates of fertilizer N are used.