Nutrient removal by corn grain harvest

Effective nutrient management requires an accurate accounting of nutrients removed from soils in the harvested portion of a crop. Because the typical crop nutrient values that have historically been used may be different under current production practices, a study was conducted to measure nutrient uptake in grain harvested in 1998 and 1999 from 23 site-years in the Mid-Atlantic region of the USA. There were 10 hybrids included in the study, but each site grew only one hybrid each year. Corn (Zea mays L.) production practices followed local state extension recommendations. Minimum, maximum, and mean corn grain yields were 4.9, 16.7, and 10.3 Mg ha(-1). Nutrient concentrations were determined on grain samples oven-dried at 70degreesC for 24 h. Minimum, maximum, and median nutrient concentration values were as follows: 10.2,15.0, and 12.9 g N kg(-1); 2.2,5.4, and 3.8 g P kg(-1); 3.1, 6.2, and 4.8 g K kg(-1); 0.13, 0.45, and 0.28 g Ca kg(-1); 0.88, 2.18, and 1.45 g Mg kg(-1); 0.9, 1.4, and 1.0 g S kg(-1); 9.0, 89.5, and 33.6 mg Fe kg(-1); 15.0, 34.5, and 26.8 mg Zn kg(-1); 1.0, 9.8, and 5.3 mg Mn kg(-1); 1.0, 5.8, and 3.0 mg Cu kg(-1); and 2.3, 10.0, and 5.5 mg B kg(-1). Median nutrient uptake values found in this study are similar to commonly used book values, but there was considerable variation among samples of corn grain. Concentrations of P and K in grain were positively associated with yield level, and concentrations of grain P were positively correlated with Mehlich-3 soil test P. The variability in nutrient removal values seen in this study, even for the same hybrid, raises questions about the usefulness of average values for estimating crop nutrient removal across a range of cropping conditions. Research is needed to identify or develop a means to correct for the sources of variability.