Submitted to: International Symposium on Precision Agriculture
Publication Type: Proceedings
Publication Acceptance Date: July 22, 1998
Publication Date: N/A
Interpretive Summary: Many factors affect soybean yield. Relative yields of varieties on different soils give us clues of factors unidentified in earlier work. This work describes a newly identified factor in soybean yields. In this study, a rather new technique called resin-extraction was used to extract ions from different soils. The suite of extracted elements was compared with the yields of three soybean varieties. The results show that one variety seems very sensitive to the presence of vanadium. Vanadium is a known poison but little evidence of its effect on plant yield has been reported. One soybean variety was insensitive and the third variety showed a mild sensitivity to the presence of vanadium. The sensitivity to vanadium was also affected by the extractable phosphorus concentration in the soil. So, some of the effect of vanadium in soil can be overcome by fertilizing with phosphorus or selecting insensitive varieties. The greatest effect of vanadium resulted in a 20% yield decrease in soybean or about 8 bu per acre. Crop producers can use these data to more efficiently fertilize for soybean production, thereby reducing costs.
Technical Abstract: In order to realize benefits of differences between soils, two goals must be accomplished: 1) testing methods must be developed which describe differences between soils and 2) plant varieties or hybrids must be developed which respond to these differences. A 3.3 ha field experiment was designed to test whether 1) resin extractions (RE) could distinguish immediately adjacent soil mapping units and 2) soil mapping units interacted with soybean variety. Soils were Buse loam, Barnes loam, Hamerly clay loam, Svea loam, and Parnell silty clay loam. The area was divided into three 1.1 ha plots which were further divided between 360 plots measuring about 3 m by 10 m. Commercial varieties of soybean were grown in 0.75 m row spacing. Soil samples were taken in selected plots, extracted with resins, and the extracts analyzed by ICP. Resin extractions show that each soil was distinguished by its suite of extractable ions. Seed yield results showed that the varieties responded differently to different soils. Examination of the results showed a complex correlation between yield for a variety and the molar ratio of V:(V+P). Soybean yields from the Buse loam < Barnes loam even though both occupy similar landscape positions. Seed yields varied from 2.65 to 3.60 Mg per ha but were positively correlated with RE-P or bicarbonate extractable-P. Seed yields were negatively correlated with extractable V for two varieties. Conventional techniques for chemical evaluation of soil are unable to identify these complex relationships. All plots were considered "upper medium" to "high" in relative bicarbonate-extractable P levels; however, P addition on the Buse loam is predicted to enhance soybean seed yield.