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

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Abstract
The Diagnois and Recommendation Integrated System (DRIS) has advantage over the critical value method in assessing the state of nutrient balance of plants because it utilizes nutrient ratio relationships. The DRIS method was evaluated using 3 data sets of N, P and K foliar analyses of determinate soybeans from P-response experiments. 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 was a useful analytical tool to evaluate responsiveness of soybeans to P fertilizer. 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 instrument, also has limitations as to plant age. The order of requirement apparently accounts for judgment of high and low levels of nutrients, but needs additional interpretation with respect to sufficiency of nutrients. DRIS may be used to diagnose nutrient balance and imbalance in annual crops.