Optimum productivity of any cropping systems depends on an adequate supply of plant nutrients.Although one or more nutrients are applied to most crops, thequantity of nutrients removed in the harvested crop is generally much greater than the quantity added.The proper rate of plant nutrients is determined by knowing the nutrient requirement of the crop and the nutrient supplying power of the soil. Although several techniques are employed to assess the fertility status of a soil: 1)nutrient deficiency symptoms of plants. 2)analysis of tissue from plants growing on the soil. 3)biological tests in which the growth of either higher plants or certain microorganism is used as a measure of soil fertility. 4)soil analysis. DRIS is a system that identifies all the nutritional factor limiting crop production and thus,increases the chance of obtaining high crop yields by improving fertilizers recommendations. Index vaiues that measure how far particular nutrients in the leaf or plant are from the optimum are used in the calibration to classify yield factors in order of limiting importance. To develop a DRIS for a crop, the following requirements must be met whenever possible: 1)All factors suspected of having an effect on crop yield must be defined. 2)The relationship between these factors and yield must be described. 3)Calibrated norms must be established. 4)Recommendations suited to particular sets of conditions and based on correct and judicious use of these norms must be continually refined. ESTABLISHMENT OF DRIS NORMS: A survey is first employed in obtaining the data required to establish DRIS norms. A large number of sites where a crop is growing are selected at random in order to represent the whole production area of a country, state, or district. At each site, plant and soil analysis for all essential nutrients are conducted. Other parameters likely to be related directly or indirectly to yield are also recorded. Second, the entire population of observations is divided into two populations (high & low yielders)based on vigor, quality and yield. Each nutrient in the plant is expressed in as many ways as possible.For example, the percentage of N in the dry matter or ratios of N/P, N/K, OR products N-P, N-K, and so on, may be used. The mean of eacg ratio for each population is calculated. Eacg ratio that significantly discriminates between the high- and low-yielding populations is retained as a useful diagnostic norms. Using N-P-K in corn leaves as an example, the significant ratios have been found to be N/P, N/K and K/P. DRIS system has several advantages over the critical level approach in making diagnoses for fertilizers recommendation purposes: 1)The importance of nutritional balance is taken into account in delivering the norms and making diagnoses. 2)the norms for the nutrient content in leaves can be universally applied to the particular crop, regardless of where it is grown. 3)diagnoses can be made over a wide range of stages of crop development, irrespective of the cultivar. 4) the nutrients limitinh yield, through either excess or insufficiency , can be readily identified and arranged in order of their limiting importance for yield.