EFFECT OF MINERAL NP AND ORGANIC FERTILIZERS ON THE PRODUCTIVITY AND NITROGEN USE EFFICIENCY OF BREAD WHEAT (Triticum aestivum L.) IN GOZAMIN DISTRICT, NORTH-WESTERN ETHIOPIA

Abstract

Wheat is one of the most important food grain sources of livelihood for smallholder farmers of the Gozamin district in north-western Ethiopia. However, the productivity of the crop is markedly low due to low soil fertility and associated low soil nutrient availability especially Nitrogen and Phosphorous deficiency, low plant N use efficiency, and use of inadequate fertilizer management practices. Adopting appropriate agronomic practices such as use of integrated nutrient management, appropriate rate of nutrient application, and use of nutrient efficient crop plants are important strategies for improving nitrogen use efficiency and consequently increasing the productivity of the crop. Therefore, one pot and two field experiments were conducted in the study area for two consecutive growing seasons (2011 and 2012). The three experiments were conducted to evaluate bread wheat varieties for nitrogen use efficiency; to elucidate the effect of nitrogen fertilizer on yield and yield components of bread wheat varieties, and to investigate the influence of farmyard manure and mineral nitrogen and phosphorus fertilizers on the productivity of bread wheat and to find out the optimum combined rates of mineral NP and farmyard manure for enhancing wheat productivity and nitrogen use efficiency. The experiment on evaluation of the nitrogen use efficiency of bread wheat varieties comprised factorial combinations of three rates of N: low (0 mg N kg-1 of soil1), medium (107 mg N kg -1 of soil), and high (214 mg N kg-1 of soil) and 10 bread wheat varieties (Bobicho, Damphe, Digalu, Dinkensh, Gasay, Pavon 76, Picaflor, Senkegna, Tay, and Tuse) in a completely randomized design with three replications. The results also revealed that the wheat varieties differed significantly (P < 0.01) in nitrogen use efficiency. On the basis of grain yield efficiency index (GYEI), it was possible to classify the wheat varieties into different N efficiency categories. Accordingly, the varieties Gasay, Tay, Picaflor and Digalu were found to be efficient and responsive. The varieties Senkegna and Bobicho were efficient and non-responsive. Damphe and Tuse were grouped as non-efficient and responsive whereas Pavon 76 and Dinkensh were found to be non-efficient and non-responsive. However, the overall nitrogen agronomic and recovery efficiency values obtained xx for the tested wheat varieties were much lower than the world’s average values for cereals. In conclusion, the results of the study have revealed that the tested bread wheat varieties differed significantly in both productivity and nitrogen use efficiency, and could provide wheat farmers the option for choice of cultivars for optimum production of the crop depending on the nitrogen input afforded by the farmers and the nitrogen status of the soil. An experiment was also conducted with a factorial combinations of six levels of nitrogen (0, 30, 60, 90, 120 and 150 kg N ha-1) and three bread wheat varieties (Gasay, Senkegna and Tay ) with RCBD with three replications to investigate the effect of N fertilizer on yield and yield components of three bread wheat varieties (Gasay, Senkegna, and Tay). Analysis of the results revealed that the rate of N application and variety significantly interacted to influence all yield and yield components. At the highest rate of nitrogen supply, the grain yield of Tay exceeded those of Gasay and Senkegna by about 11 and 8%, respectively. Moreover, the application mineral N fertilizer increased grain yield of wheat by positively affecting the important components of the crop plant. Therefore, from this study, it could be concluded that the tested varieties markedly responded to the increased rates of nitrogen application and showed the need to apply variety-specific higher rates of nitrogen for attaining optimum grain yields of the crop in the study area. The experiment with farmyard manure (FYM) and mineral nitrogen (N), and mineral phosphorus (P) fertilizers comprised a factorial combinations of three rates of FYM (0, 10, and 15 t ha-1), three rates of nitrogen (0, 60, and 120 kg N ha-1) and three rates of phosphorus (0, 46, and 92 kg P2O5 ha-1) in RCB design with three replications. Analysis of the results revealed that the combined application of FYM at 10 t ha-1 with 120 kg N and 92 kg P2O5 ha-1 increased grain yield by 153% and 16%compared to the negative (0-0-0 kg ha-1 FYM-N-P2O5) and positive (0-120-92 kg ha-1 FYM-N-P2O5) controls, respectively. It was observed that the integrated use of 10 t ha-1 FYM with 120 kg N and 92 kg P2O5 ha-1 resulted in the maximum grain yield and yield components, grain N uptake and protein content. However, results of the economic analysis showed that the maximum net benefit was obtained in response to the application of 15 t ha-1FYM combined with 60 kg N ha-1 and 46 kg P2O5ha