A regional survey was conducted in Nubaria region, concerning maize (Zea mays L.) in order to develop diagnostic norms and evaluate yield- limiting nutrients in case of low-yielding maize.The leaf nutrient status was interpreted using Diagnosis and Recommendation Integrated System (DRIS) of Beaufils (1973). Leaf samples were taken at the silking stage and analyzed for N, P, K, Ca, Ng, Fe, Mn, and Zn. Nutrient indices were calculated using published standards and locally-developed indices (Nubaria region). Preliminary DRIS norms for maize leaves are developed from 287 sets of data on elemental (NPKCaMgFeMnZn) leaf composition and corresponding yields. This is done by dividing the population of observations into two subpopulations on basis of yield. The norms are calculated from those forms of expressing the leaf parameters which significantly discriminate between the two subpopulations.
The degree of nutrient imbalance in plant is expressed in terms of DRIS index which measures the extent to which a particular nutrient deviates from the established norm. The norms are developed in such a way that the influence of age of tissue sampled on the diagnostic index is minimized. The DRIS norms enable one to diagnose whether N,P, K,Ca,Mg,Fe,Mn or Zn is the nutrient most limiting to maize production in a particular case to be diagnosed. However the DRIS studies can be made irrespective of variety and age at which the plant leaf is sampled.
The DRIS system in predicting nutrient imbalances even when the nutrient concentration in the plant is in or above the critical or suficiency level range, is illustrated.
|
