Ionic Ratios and Crop Performance: II. Eects of Interactions amongst 3 Vanadium, Phosphorus, Magnesium and Calcium on Soybean Yield

Because vanadium (V) is easily reduced to a cationic form within plant cells, data from resin-extraction of soil were analysed for evidence 5 of interactions between V and the resin-extractable concentrations of magnesium (Mg) and calcium (Ca) on soybean seed yield. Three varieties, 9091, 9061 and 704, were grown over a 3-year period in a corn± soybean±wheat rotation. Surface soil samples (0±15 cm) were extracted with ion-exchange resins, extracts were analysed by inductively coupled plasma methods (ICP) 6 , and the results were regressed against seed yield using SAS PROC STEPWISE analysis using forward selection, backward elimination and maximum R routines. The seed yield of each variety showed a correlation with a unique set of resin-extractable concentrations of V, phosphorus (P), Mg and Ca, and the V:(V + P), Mg:(Mg + Ca), Mg:(Mg + 1000 V) and Ca:(Ca + 1000 V) ratios. Variety 9091 was most sensitive to the Mg:(Mg + Ca) ratio. Variety 9061 was most sensitive to extractable V and to the V:(V + P) ratio. Variety 704 was sensitive to extractable P, V and Ca and the Mg:(Mg + 1000 V) ratio. For variety 9091, Mg fertilization (not currently practised) may be an economical practice, whereas P fertilization of 704 may not be economical 7 . Each regression technique varied slightly in identi®cation of important factors in seed yield. Concentrations and ratios of resin-extractable elements in soil provide insights into optimal genotype selection and possible management alternatives for a given soil.