Macro-Nutrient Concentration and Content of Irrigated Soybean Grown in the Early Production System of the Midsouth

Macro-nutrients in soybean (Glycine max L. Merr.) have not been extensively researched recently. Concentrations and contents of nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur (N, P, K, Ca, Mg, and S) were determined for three irrigated cultivars grown using the early soybean production system (ESPS) on two soils (a sandy loam and a clay) in the Mississippi Delta during 2011 and 2012. Data were collected at growth stages V3, R2, R4, R6, and R8. No change in macro-nutrients due to soil type or years occurred and modern cultivars were similar to data collected >50 years ago. Mean seed yield of 3328 kg ha^?1 removed 194.7 kg N ha^?1, 16.5 kg P ha^?1, 86.0 kg K ha^?1, 17.5 kg Ca ha^?1, 9.0 kg Mg ha^?1, and 10.4 kg S ha^?1. Increased yields over the decades are likely due to changed plant architecture and/or pests resistance, improved cultural practices, chemical weed control, and increased levels of atmospheric carbon dioxide (CO₂). Yield improvements by genetically manipulating nutrient uptake appear to be unlikely.