Dris evaluation of n, p, k status of determinent soybeans in Brazil

Abstract

Abstract The Diagnois and Recommendation Integrated System (DRIS) has advantage over the critical value method to assess the state of nutrient balance of plants because it utilizes nutrient ratio relationships. The DRIS method was evaluated utilizing 3 data sets of N, P, and K foliar analyses of determinent soybeans from P‐response experiments in Brazil. Evaluation of data sets collected at growth stage R‐2 resulted in lowest calculated DRIS sum, an indication of highest degree of nutrient balance, to conform to highest yield. The DRIS method proved useful as a analytical tool to evaluate responsiveness of soybeans to phosphorus fertilizer materials. Foliar analyses of plants approaching maturity, R‐7, would indicate a different order of nutrient requirements than when collected at growth stages R‐2 or R‐5. This would suggest that DRIS, as a nutrient status evaluation instru‐ ment, also has limitations as to plant age. The order of requirement appears to account for judgement of high and low levels of nutrients, but needs some additional interpretation with respect to sufficiency of nutrients. Because DRIS can be used to diagnos nutrient balance and imbalance, refinement of the method for use with annual crops should be encouraged.