RESPONSE OF BREAD WHEAT (Triticum aestivum L.) VARIETIES TO NITROGEN FERTILIZER RATES AT MEKDELA DISTRICT, SOUTH WOLLO, ETHIOPIA

This study was initiated to assess the effect of N fertilizer rates on growth, yield, and quality of newly released bread wheat (Triticum aestivum L.) varieties and identify the optimum N fertilizer rates and appropriate bread wheat variety. A field experiment was carried out in 2019 main cropping season at Mekdela, South Wollo, Ethiopia. Factorial combinations of two wheat cultivars Lemu (ETBW 6861) and Wane (ETBW 6130) and five rates of N (0, 46, 92,138 and 184 kg N ha(-1)), were laid out in a Randomized Complete Block Design with three replications. Pre planting soil analyses results revealed that soil textural class was clay, medium in total N (0.2%), slightly acidic reaction and medium in organic matter (4.3%). Though the interaction of N rate and variety exhibited fewer effects, the soil analyses after harvest showed that N rate had residual effect on the soil. The variety Lemu had higher values for effective tillers, spike length, plant height, number of seeds spike(-1), grain and straw yield, hectoliter weight and grain N uptake. On the other hand, Wane variety exhibited greater values for thousand seed weight, dry and wet gluten, and with short phenological period. Although the difference was non-significant in HI, straw and total N uptake agronomic and physiological efficiency and grain protein content between varieties, Wane had greater agronomic and physiological efficiency, straw N uptake and HI. However, Lemu variety had higher total N uptake and protein content than Wane variety. Days to maturity, effective tillers, plant height and straw yield were consistently increased in response to N rates. The highest values of seed spike-1(57.4), thousand seed weight (44.5 g), grain yield (7415 kg ha(-1)), HI (36.3%), hectoliter weight (82.53 kg hl(-1)) and physiological efficiency (45.48 kg kg(-1)) were recorded at 92 kg N ha(-1); whereas the highest agronomic efficiency (48.65 kg kg(-1)) was obtained from 46 kg N ha(-1). Though inconsistent increments of grain and straw N uptake, dry and wet gluten increased with increased N rates, the highest values recorded from 184 kg N ha(-1). The longest spike length was obtained from 92 kg N ha(-1) for Lemu (9.33 cm) and138 kg ha(-1) for Wane (7.13 cm). The longest days to grain filling and highest grain protein was recorded from 184 kg ha(-1) for both varieties. The partial budget analysis results revealed that the highest marginal rate of return was 980% at 92 kg N ha(-1).In nutshell, based on grain yield, net benefit, MRR, better quality traits, N rate of 92 kg ha(-1) could be recommended for both Lemu and Wane variety production around Mekdela area. However, as the experiment was conducted only for a single season, we suggest the repeat of the study for more seasons around Mekdela area and similar agroecology.