Submitted to: International Soil Science Society Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/26/1998
Publication Date: N/A
Interpretive Summary: Current soil testing methods are generally unable to distinguish between complex chemical effects of closely related elements. An example is phosphorus (P) and vanadium (V). Phosphorus, an essential nutrient element for all life forms, is taken up by plants. Vanadium, while common in soil, is usually present in concentrations much less than that of P. Most soil tests ignore V because no previous evidence existed of its importance to crop production. The chemical forms of both, as they exist in the soil, are similar. A new extraction device, developed at the USDA-ARS North Central Soil Conservation Research Laboratory, permits extraction of up to 20 elements simultaneously from the soil. Use of this test, along with field studies, showed that the presence of vanadium may interfere with the plant's uptake of phosphorus even when soils are moderately rich in phosphorus, thus depressing yields of some soybean varieties by as much as 10 bushels per acre. This new soil test can enable producers to determine if V is likely to be a problem for soybean production. These data also provide guidelines to assist the producers in adjusting either their phosphorous fertilizer practices and/or soybean seed variety selection to reduce the risks and costs of production.
Technical Abstract: Methods of soil evaluation often limit the number of elements which can be quantified from a single extract. This constraint obscures subtle and complex interactions between nutrient elements and plant genotypes. A complex interaction of phosphorus(P)and vanadium(V)on soybean seed yield was identified using resin extraction techniques in a wheat (Triticum aestivum L.)-soybean-maize(Zea mays L.)rotation on the Swan Lake Res. Farm near Morris, MN. Soils were Barnes loam(Udic Haploboroll),Hamerly clay loam (Aeric Calciaquoll), Parnell silty clay loam (Typic Argiaquoll), Buse loam (Udothentic Haploboroll), and Svea loam (Udic Haploboroll ). Each rotation consisted of 360 plots measuring 3 m by 10 m. Soybean was planted in strips containing 30 consecutive plots. Seeds were planted in rows spaced at 0.75 m intervals at a rate of 65 seeds m**-2. Pioneer Brand seed 9061 and 9091 were planted in 1995 and 1996. Cenex Brand variety 704 was also planted in 1996. Soil samples were collected during the summer, dried, crushed and passed through a 2.0 mm sieve. Soil samples(6 g)were suspended in 20%(v/v) methanol and equilibrated with ion exchange resins. After equilibration, resins were eluted and analyzed directly using ICP methods. Data on extractable chemistries were analyzed using SAS PROC GLM procedures. Soils differed in NaHCO3 extractable P, resin extractable (RE)-P, and RE-V. Seed yields varied from 2.65 to 3.60 Mg ha**-1 but were positively correlated with RE-P or HCO-3 extractable P. Seed yields were negatively correlated with extractable V for Pioneer 9061 and Cenex 704; Pioneer 9061 was unaffected by extractable V. A complex RE-P by RE-V interaction affected seed yield. Non-resin techniques for chemical evaluation of soil are generally unable to identify these complex relationships.