Response surface studies relating to the effect of fertilizers on wheat at various model agronomic centres.

Abstract

The date of Model Agronomic Experiments on the high yielding and locally improved varieties of wheat conducted during the years 1968-69 and 1969-70 have been taken up for the present study. Various model agronomic centers have been classified according to different soil types. Quadratic response surfaces were fitted to the data of all the experiments for various soil types and for different groups of varieties. The fitted functions, the S.E.’s of coefficients and R2 have been given in appendix- I. Further, the varieties have been grouped on the basic of their agronomic characteristics especially the duration of the growth. These have been given in Chapter III. The study reveals that the coefficients of multiple determinations,R2s, are highly significant in almost all the centers indicating thereby that the surface fit well to the data of almost all the experiments, for the discussion of the results, we have selected only those experiments for which the optimum (physical) combinations of fertilizers are found to be within the range levels tried in the experiments. The selected function for a given group of variety is either the pooled one or the one having minimum Cvi. A discussion of the method of such selection of the function representing the entire group within a soil type appears in chapter IV. The method of fitting of the quad ratio response surfaces, estimates of the various regression coefficients and their S.E.’s have been described in Chapter IV. The optimum combinations of fertilizers, the corresponding maximum yields in q/ha and not profits have been worked out only for the selected functions. The study reveals that the fertilizer responses very significantly by soil type and varieties. It is evident from this study that high yielding varieties comprising groups I, II and III have given higher response generally in all types of soils. The response is highest for varieties classified under Group I. It is also seen from this study that the application of nitrogen has attained the stage where the production has generally reached its maximum. However, the responses in case of phosphorus and potassium do not show consistent patterns in various soil types although in few cases local improved varieties classified in Group IV have shown better performance. The results of this study indicate that local varieties have given the lowest not profits when this optimum doses of fertilizers are applied. There is no consistency in the case of high yielding varieties for the entire study period. In some cases group I varieties have shown better profits whereas in other cases varieties classified under groups II and III have shown better performances, so far as not profits at optimum doses of fertilizer use. Although it is evident from the present study that there is variation in responses according to varieties and soil types, but it is different to demarcate with only two years data soil types and variety groups into specific categories having high or low responses. For any such worthy objective, it may be desirable to analyze on the lines suggested here the data based on several years experiments. Further research is also required to investigate the causes of insignificance of phosphorus and passion fertilizers. It may be worthwhile to investigate the causes why generally the interaction terms are non-significant.