The experiment was conducted to assess the effects of nitrogen (N) rate and time of application on N use efficiency (NUE) of bread wheat, and their association with grain yield and protein content. Factorial combinations of four N levels, two bread wheat varieties and three timings of N applications were laid out in a randomized complete block design. N rate significantly influenced grain yield, protein content, N uptake efficiency, N biomass production efficiency, N utilization efficiency, N use efficiency for grain and N use efficiency for protein yield. Time of N application had highly significant effect on grain yield, protein content and NUE traits. Rate of N application and variety were significantly interacted to influence grain yield. Grain yield for Madda Walabu found sharply increase with each increase in N application rate. The improved variety provided significantly higher grain yield, N utilization efficiency and N use efficiency for grain yield (NUEGY) when N was applied 1/4 at planting, 1/2 at mid-tillering, and 1/4 at anthesis. Variations in NUEGY were explained more by the variations in N uptake efficiency. Harvest index contribution to NUEGY was higher for the local variety. Although NUE significantly decreased with increasing N rates, yield response of the varieties did not plateau out.

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The benefits of water-saving techniques such as alternate furrow and deficit irrigations need to be explored to ensure food security for the ever-increasing population within the context of declining availability of irrigation water. In this regard, field experiments were conducted for 2 consecutive dry seasons in the semiarid region of southwestern Ethiopia and investigated the influence of alternate furrow irrigation method with different irrigation levels on the yield, yield components, water use efficiency, and profitability of potato production. The experiment comprised of 3 irrigation methods: (i) conventional furrow irrigation (CFI), (ii) alternate furrow irrigation (AFI), and (iii) fixed furrow irrigation (FFI) combined factorially with 3 irrigation regimes: (i) 100%, (ii) 75%, and (iii) 50% of the potato water requirement (ETC). The experiment was laid out in randomized complete block design replicated thrice. Results revealed that seasonal irrigation water applied in alternate furrows was nearly half (170 mm) of the amount supplied in every furrow (331 mm). Despite the half reduction in the total amount of water, tuber (35.68 t ha−1) and total biomass (44.37 t ha−1) yields of potato in AFI did not significantly differ from CFI (34.84 and 45.35 t ha−1, respectively). Thus, AFI improved WUE by 49% compared to CFI. Irrigating potato using 75% of ETC produced tuber yield of 35.01 t ha−1, which was equivalent with 100% of ETC (35.18 t ha−1). Irrigating alternate furrows using 25% less ETC provided the highest net return of US$74.72 for every unit investment on labor for irrigating potato. In conclusion, irrigating alternate furrows using up to 25% less ETC saved water, provided comparable yield, and enhanced WUE and economic benefit. Therefore, farmers and experts are recommended to make change to AFI with 25% deficit irrigation in the study area and other regions with limited water for potato production to improve economic, environmental, and social performance of their irrigated systems.

Knowledge of optimal combinations of crop densities, herbicide dose and time of application could improve the effectiveness and net benefit of commonly used herbicides. A study was conducted at two locations in SARC on-station and farmer's field, South Eastern Ethiopia for two years from 2007 to 2008. The experimental design was randomized complete block (RCB) design with split-plot arrangement. Durum wheat (Triticum turgidum) seeding rates (recommended, 25% and 50% plus recommended rate) were arranged in the main plot. Four wild oat (Avena fatua) herbicide, Topik, doses (0, 25, 50 and 100 % of the recommended dose) and three timing of applications (14 DA, 32 DAE and 50 DAE) were used as sub-plot treatments. The treatments were compared to determine their effect on durum wheat yield, yield components wild oat densities and control efficacies. Durum wheat seeding rates significantly influenced grain and biomass yield, spike per unit area and kernel weight. Seeding rate of 225 kg ha-1 produced highest grain yield (3810.4 kg ha-1) while 150 kg ha-1 recorded the lowest. Mean wild oat density count before herbicide application timings varied over the two locations averaging 37 and 87 seedlings m-2. Increasing seed rate by 25 and 50% increased wild oat control efficacy by 16.9 and 21.5% respectively. Spraying the herbicide at later growth stages caused greater wild oat seedling density and reduced wheat yield at both locations. The highest efficacy (94.04%) was obtained in the second time of application (30 DAE) of 1 l lit ha-1. The highest reduction in population density was occurred in 100% herbicide rate. There was a general decline in wild oat density in the early application and as the herbicide dose increased, but the effect of seeding rate varied very slightly. In contrast to the wild oat control efficacy the highest grain yield ha-1 was obtained in the first application date (14 DAE). Durum wheat yield losses in the absence of herbicide application were increased by about 16%. Maximum yield (3870.73 kg ha-1) was obtained at 100% of the herbicide dose very closely followed by 50 and 25% of the recommended rate reducing durum wheat yield only by about 1.6 and 2% respectively. Durum wheat seeding rate, herbicide dosage and application timing had statistically no significant interaction effect.

The use of optimum seeding rate for the genotype may enhance productivity and grain protein content of durum wheat. Therefore, an experiment was conducted at two locations in south-eastern Ethiopia during the main cropping season of 2008 with the objective of elucidating the effects of seeding rate and genotype on agronomic performance and grain protein content of the crop. The experiment consisted of factorial arrangements of four improved durum wheat genotypes and five seeding rates, which were laid out as a randomized complete block design with three replicates. Seeding rates significantly influenced agronomic performances including number of fertile spikes m-2, plant height, number of seeds spike-1, and grain yield. Number of fertile spikes m-2 was increased proportionally with the seeding rate and the highest number (382 spikes m-2) was recorded in the highest seeding rate of 200kg ha-1. Inversely, the highest number of kernels spike-1 (29.8) was at the seeding rate of 100 kg ha-1. The highest grain yield (4341 kg ha-1) was obtained in response to seeding rate of 175 kg ha-1, which was in statistical parity with the yield obtained at the seeding rate of 150 kg ha-1. However, grain protein content was not influenced by the seeding rates. There were significant (P ≤ 0.05) variations among the genotypes for all the agronomic traits measured. The largest number of fertile spikes m-2 was recorded for the genotypes Oda (360 spikes m-2) and Bakalcha (345 spikes m-2). Genotype Illani produced the longest spike (6.9 cm). Oda and Illani produced the highest numbers of seeds spike-1, 38.8 and 36.9, respectively. The number of fertile spikes m-2, number of seeds spike-2 and kernels weight significantly contributed grain yield. The genotypes had exhibited less variation for grain protein content. Except for grain yield and harvest index, seeding rate x genotype interaction had no significant effect on other agronomic traits. Highest grain yields of 4938 kg ha-1 and 4774 kg ha1 were obtained from genotypes Ejersa and Bakalcha when sown at the seeding rate of 150 kg ha-1 and 175 kg ha-1, respectively. Grain protein response was significantly influenced by the interaction effect in which genotype Oda had the highest (12.9%) and lowest (10.5%) protein contents at the highest (200 kg ha-1) and lowest (100 kg ha-1) seeding rates, respectively.