Response of bread wheat (Tritcum aestivum L.) to nitrogen after major leguminous crops rotation in Tigray, northern Ethiopia
Crop rotation is a common practice in the study area, but there is no enough information on the specific rate of nitrogen to be applied after legumes for wheat production. Hence, on farm field experiments were conducted to determine the amount of nitrogen fertilizer rates needed for bread wheat after chick pea, grass pea, fababean and field pea precursor crops. The field experiments were conducted during 2014 main cropping season at Hawzien after chick pea and grass pea and at Emba Alaje after fababean and field pea precursor crops. The experiment consists of six nitrogen rates (0, 11.5, 23, 34.5, 46 and 69 kg Nha-1) laid in a RCBD with three replications. Phosphorus, sulfur and potassium fertilizers were also applied as basal for all plots at sowing. Surface soil samples were collected before planting and analyzed for selected soil properties. Soil analysis result of the experimental sites revealed that total nitrogen content (%) of the soil after chickpea-wheat (0.0695), grass pea-wheat (0.067), fababean-wheat (0.074) crop rotation were categorized under low range and after field pea-wheat (0.102) under medium range. Application of nitrogen had significantly increased grain and straw yield at Hawzien district after chick pea and grass pea precursor crops. At Emba-Alaje the highest grain yield was recorded on plots treated with 69 kg N ha-1 (6242 kg ha-1). Grain and straw yields of wheat increased up to a rate of 46 kg N ha-1 after fababean at Emba-Alaje district. There is no significant difference in grain and straw yields of wheat due to application of nitrogen after field pea crop rotation. In Hawzien the highest agronomic efficiency after chick pea and grass pea was recorded from plots treated with 46 kg N ha-1 and 34.5 kg N ha-1, respectively. In Emba Alaje the highest agronomic efficiency after faba bean and field pea was recorded from plots treated with 11.5 kg N ha-1 and 23 kg N ha-1 , respectively. At Hawzien, the partial budget analysis revealed that application of 46 kg N ha-1 for bread wheat after chick pea and grass pea was economical with 1545% and 796 % marginal rate of return, respectively. At Emba Alaje, the partial budget analysis revealed that application of 34.5 kg N ha-1 for bread wheat after fababean was economical with 895% marginal rate of return. It could be concluded that application rate of N for wheat after leguminous crops should consider initial soil N and precursor crop.