Nitrogen is the most limiting nutrient in the production of maize in western Ethiopia with its favourable climate for this crop. This is because Nitisols inherently low in N are used for maize production by resource-poor farmers who cannot afford fertilizer application. ,An option in combating this constraint is planting of maize genotypes that are efficient in N use. Experiments were therefore conducted to evaluate different maize genotypes for grain yield, N uptake and use efficiency at five sites. At each site two experiments, viz. one with open-pollinated genotypes and the other with hybrid genotypes were laid out in a randomized complete block design with three replications. In each of these experiments either five open-pollinated genotypes or five hybrid genotypes were combined in complete factorial arrangement with six N fertilization levels ranging from 0 to 230 kg ha-1 at 46 kg intervals. The results indicated that only two genotypes qualified as N use efficient, viz. the open-pollinated Ecaval 1 and the hybrid CML373/CML202/CML384. On average they outyielded their respective local genotypes by 5.9% at a low N application and by 17.5% at a high N application. Both genotypes also showed consistently higher N agronomic efficiency, N recovery efficiency and N physiological efficiency at low and high N applications. The introduction of these two N use efficient genotypes into the farming systems of the resourcepoor farmers could be beneficial to them.

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Occasionally a herbicide that is considered safe to use at prescribed rates causes damage to crop plants at those same rates. Alachlor (Lasso EC®)is registered for use on sunflower at a rate of 1.5 to 1.92 kg ai ha-1 . Occasional injury to sunflower plants at these rates is usually caused by incorrect application or unsuitable weather conditions, but sometimes no explanation can be found. In many crops it has been shown that genetic differences can make specific cultivars more susceptible to alachlor injury. The objective of this study was to screen 22 of the available sunflower cultivars for sensitivity to alachlor in a glasshouse trial. Planting took place in pots filled with a sandy loam soil (20% clay). Five rates of alachlor (0,0.96,1.92,3.84 and 7.68 kg ai ha-1 ) were applied and leached into the soil with 100 ml of water. Pots were laid out in an air-conditioned glasshouse set to 28/18°C day/night in a randomised block design with three replicates. Plants were harvested 38 days after planting, at which stage plant height and mass were determined. The results indicated that cultivar differences with respect to alachlor tolerance were present. Plant height appeared to be the best predictor of alachlor activity in sunflower. Cultivars were divided into three classes (tolerant, intermediate and sensitive) based on their reaction to the herbicide.