Multiple nutrient imbalances in ear leaves of on-farm unfertilized maize in eastern and southern Africa

Maize is a major food crop in eastern and southern Africa and is often cultivated with insufficient supplies of nutrients. The current studies are aimed at diagnosing any potential nutrient limitation in maize under farmers' conditions using the nutrient content in ear leaf tissue at tasseling stage. The majority of the maize crops were considered below the critical nitrogen (N) content in the ear leaves with mean N content of 1.84%. Phosphorus (P), B and Cu content appeared critically low at three of the four sites. Unique fingerprinting by multivariate statistics was possible for each site when using the proportion of nutrients in the leaf tissue. The content of six macro elements (N, P, K, S, Mg, Ca) at the tasseling stage were found to be able to predict 83% of the variation in the grain yield at maturity whereas the inclusion of micronutrients only improved this prediction with an additional 3%. N alone predicted 50% of the variation in grain yield and the N supply of the maize crops in eastern and southern Africa must thus be the first priority before yields can be improved.