Determine sward nutrient status to indicate deficiencies and over-supply with nutrients.
Determining sward nutrient status with DRIS-ryegrass (Diagnosis and Recommendation Integrated System) is a mathematical model which interprets the results of grass tissue analysis to give a series of indices for N, P, K and S. Negative indices indicate deficiencies that are serious enough to limit sward production. An index of -1 indicates that at least 10% of the maximum DM yield has been lost, and indices between -10 and -30 suggest that up to 40% of the possible DM yield has been lost. Positive indices indicate that the swards are either adequately or over-supplied with these nutrients. The optimum DRIS index range is between +5 and +15. Above +15 the nutrient in question is truly surplus to crop requirement.