Submitted to: International Conference on Site Specific Agriculture
Publication Type: Abstract Only
Publication Acceptance Date: July 19, 2000
Publication Date: N/A
Technical Abstract: Plant growth is sensitive to concentrations of resin extractable elements in soil. Resin extractable element concentrations vary with soil type, landscape position and climatological zone. We have shown that soybean (Glycine max L.) seed yield is sensitive to the resin extractable V:(V+P) molar ratio in soil and that the effect of this ratio was cultivar- dependent. Because V is a potent ATPase inhibitor and Mg and Ca are important ATPase cofactors, we examined the data for correlation between seed yield and the resin extractable Mg:(Mg+Ca) molar ratio. Data were obtained from a 3.2 ha field site. The field site was divided into three equal portions and each had 360 plots. Two cultivars were planted in 1995 (9091 and 9061) and a third (704) was added in 1996 and 1997. Composite soil samples were taken from 180 plots in each portion to a depth of 60 cm. Surface soil samples (6 g) from selected plots were subjected to extraction nwith cation and anion resin extractors for 5 days. Extractors were washed and eluted with acid and the extracts were analyzed with ICP methods. Seed yields of 9091 increased by 27% as the resin extractable Mg:(Mg + Ca) molar ratio increased 0.2 to 0.8. Seed yields of 9061 increased in 2 of 3 years as the Mg:(Mg + Ca) molar ratio increased. Seed yields of 704 increased as the resin extractable Mg:(Mg + Ca) molar ratio increased in both years in which it was grown. The relative gains of 9061 and 704 were much less than those of 9091. Greenhouse studies using the same soils as the field study show soybean yields are increased with the application of MgPO4; this suggests a real effect of resin extractable Mg on soybean yields. Knowledge of complex elemental interactions serves as a guide to both site specific soil management and plant breeding.