For the establishment of a model of nutritional status for various grain yield class the contents of nitrogen, phosphorus, potassium and silica at different growth stages from the results of plant analyses in N. P. K simple trial carried out countrywide for three years. were investigated in relation to grain yield (1967-1969). The increasing tendency of nutrient content in straw or grain with the increase of grain yield was N$gt;P$gt;K$gt;Si. The tendency was yearly changed differently according to kind of nutrient and growth stage. Nutrient contents appear to have closer relation to the grain yield class than to the total dry matter yield class.