The use of critical concentration approach to diagnosis the nutrient status of plants is somewhat erroneous in that ‘critical nutrient concentrations’ are not independent diagnostics, but can vary in magnitude as the background concentrations of other nutrients increase or decrease in crop tissue. The Diagnosis and Recommendation Integrated System (DRIS), an alternative is sometimes less sensitive than the sufficiency range approach to differences caused by leaf position, tissues age, climate, soil conditions, and cultivar effect because it uses nutrient ratios. The DRIS provides a reliable means of linking leaf nutrient concentrations to the yield of groundnut, and may be developed for this crop using existing experimental data. The present study was carried out in the Upper Catchment of Benin in 2001 and 2002, and grain yield and leaf nutrient concentration data from organic and inorganic trials were used to establish DRIS norms for N, P, K, Mg, Ca, S and Zn and statistical parameters for groundnut. The DRIS norms from this study were K/Ca: 1.4, K/S: 15.8, K/N:0.7, Mg/Ca: 0.2, Mg/K: 0.2, Mg/P: 2.1, Mg/Zn: 159.8, N/Ca: 2, N/S: 23.9, Zn/N: 0.0008, P/K: 0.1, P/N: 0.1, P/S: 1.3, P/Ca: 0.1, P/Zn: 76.1, S/Ca: 0.1, and Zn/Ca: 0.002. Although the database was relatively small, the norms derived for nutrient ratios of key biological significance, i.e. N/S and K/N, were within the expected narrow ranges for higher plants, giving credibility to both the database and the DRIS model. Data from future surveys and field experiments may subsequently be used to enlarge the database allowing the refinement of model parameters and hopefully an expansion of the diagnostic scope such as to include other micro-nutrients. The nutrient status assessment using the selected DRIS norms shows a good nutrient level for N, P, K, Ca, S and Zn in the groundnut leaves for high yielding as their value was similar to those presented in the literature. As it stands, this preliminary DRIS model for groundnut offers a good diagnostic tool for evaluating the N, P, K, Ca, S and Zn status of groundnut crops in Benin.
