EFFECTS OF BLENDED NPSB FERTILIZER RATES ON GROWTH, YIELD COMPONENTS AND YIELD OF BREAD WHEAT (Triticum asetivum.L) VARIETIES AT DEGAM DISTRICT, CENTRAL ETHIOPIA

Bread wheat (Triticum aestivum L.) is an important food crop and source of income for farmers at Degam district in central highland of Ethiopia. However, its productivity is mainly constrained by poor soil fertility and lack of site specific fertilizer (NPSB) recommendation in general and in the study area in particular. Thus, field experiment was conducted at Degam district on farmer's field in 2019 main cropping season to investigate the response of bread wheat varieties to blended NPSB fertilizer rates and identify its economic benefit. Factorial combination of three improved bread wheat varieties (Danda’a, Hidase and Kakaba) and six fertilizer rates [Control, 50 kg NPSB, 100 kg NPSB, 150 kg NPSB, 200 kg NPSB each supplemented with 92 kg N ha-1 and 64/20 kg NP ha-1 (Blanket recommendation) were laid out in randomized complete block design with three replications. Analysis of the results revealed that number of total tillers (NTT), spike length (SL), number of kernels per spike (NKS), above ground biomass (AGBM), straw yield (SY) and grain yield (GY) were significantly affected by the main effect of fertilizers; similarly, number of total tillers (NTT), number of kernels per spike (NKS), thousand kernels weight (TKW) and grain yield (GY) were significantly affected by the main effect of varieties. While days to 50% heading (DH), days to maturity (DM), plant height (PH) and number of productive tillers (NPT) were affected by interaction effects of fertilizer and varieties. The highest NKS (54.9), AGBM (13.8 tons ha-1 ), SY (9.4 tons ha-1 ) and GY (4549kg ha-1 ) were recorded from 200 kg NPSB fertilizer. Among the varieties the highest NKS (54.3) from Danda’a, TKW (49.3 g) and GY (3351kg ha-1 ) were recorded from Hidase variety. Variety Kakaba score the highest PH (102.5 cm) and PNT (5 per plant) with combination of 200 kg and 150 kg NPSB fertilizer respectively and reached days to heading and maturity earlier than Danda’a and Hidase. In general, the economic feasibility of the fertilizer over varieties combination indicated that application of 200 kg NPSB ha-1 to all varieties Hidase, Danda’a and Kakaba resulted in maximum marginal rates of return 640.14 %, 604.81% and 481.47%, with a net benefit of 97993, 88596, and 82996 ETB respectively. On the other hand, application of 200 kg NPSB ha-1 led to the highest MRR for the Hidase variety as compared to all other treatments and with about a total of 9397 ETB net benefit increment. Therefore, application of 200 kg blended NPSB in supplement of 92 kg N ha-1 fertilizer with Hidase variety was temporarily the best producing alternatives and economically profitable grain yield with acceptable grain yield of bread wheat production at the study area.