Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/18/2016
Publication Date: 9/2/2016
Citation: Bruns, H.A. 2016. Macro-nutrient concentration and content of irrigated soybean grown in the early production system of the Midsouth. Communications in Soil Science and Plant Analysis. doi:1080.00103624.2016.1225079.

Interpretive Summary: Information on the uptake of macro-nutrients by irrigated soybean grown in the Early Soybean Production System common to the Midsouth would be helpful in making fertilizer recommendations, but it is currently unavailable. A scientist at the USDA-ARS, Crop Production Systems Research Unit, Stoneville, MS, has completed an experiment that determined the amount of N, P, K, Ca, Mg, and S contained in the leaves, stems, pods, and seed throughout the season of three popular soybean varieties. Two sites were used, a sandy loam soil and a heavy clay. The nutrient concentrations in the plant tissue were found not to have changed from levels observed in old varieties evaluated over 50 to 75 years ago. However, total nutrient requirements per acre have increased due to higher yields that have resulted from improved genetics and cultural practices. This research found that a 48 bu/A seed yield will remove about 175 lbs/A of N, 16.5 lbs/A of P, 77 lbs of K, 15.5 lbs/A of Ca, 7.5 lbs/A of Mg, and 8.5 lbs/A of S.

Technical Abstract: Generally macro-nutrient concentrations and contents in soybean (Glycine max L. Merr.) has not been extensively researched in nearly 50 y. Concentrations and contents of N, P, K, Ca, Mg, and S were determined for three irrigated cultivars grown using the early soybean production system 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. Data showed no change in macro-nutrient concentrations due to soil type or years and modern cultivars had similar concentrations to data collected over 50 y ago. A mean seed yield of 3328 kg ha-1 was estimated to remove 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 when harvested. Increases in soybean seed yields and total phytomass over the decades has likely been due to changes in plant architecture and/or pests resistance, improved cultural practices, chemical weed control, and increased levels of atmospheric CO2. From these data though, yield improvements by way of genetically manipulating nutrient uptake appears to be unlikely.