The productivity and quality of malting barley were evaluated using factorial combinations of four preceding crops (faba bean, field pea, rapeseed, and barley) as main plots and four nitrogen fertilizer rates (0, 18, 36, and 54 kg N ha −1 ) as sub-plots with three replications at two sites on Nitisols of the Ethiopian highlands in 2010 and 2011 cropping seasons. Preceding crops other than barley and N fertilizer significantly improved yield and quality of malting barley. The highest grain yield, kernel plumpness, protein content, and sieve test were obtained for malting barley grown after faba bean, followed by rapeseed and field pea. Nitrogen fertilizer significantly increased yield, protein content, and sieve test of malting barley. All protein contents were within the acceptable range for malting quality. Inclusion of legumes in the rotation also improved soil fertility through increases in soil carbon and nitrogen content. We conclude that to maximize yield and quality of malting barley, it is critical to consider the preceding crop and soil nitrogen status. Use of appropriate break crops may substitute or reduce the amount of mineral N fertilizer required for the production of malting barley at least for one season without affecting its quality.

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Barley (Hordeum vulgare L.) is a major food crop in Ethiopia. A high inter-annual rainfall variability, concomitant variable planting dates and unpredictable drought stress at any time during the rainy season are severe constraints to barley production in Ethiopia. To study genotype by environment (G x E) interactions and grain yield stability, 18 barley genotypes (three landraces and 15 improved cultivars) were evaluated for yield and flowering time in two locations (Ambo and Jimma) and four staggered sowing dates over two years (2012-2013) giving a total of 16 environments. It was observed a wide phenotypic variation over environments for both grain yield (677-2,944 kg ha-1) and days to 50% flowering (63-82 days). Considering the 18 genotypes and 16 environments, both genotype (G) and G x E interaction variance components were highly significant for grain yield, with a ratio of approximately 1:1. The G x E analysis revealed that the first two interaction principal component axes (IPCA1 and IPC2) in an additive main effect and multiplicative interaction (AMMI) model explained 66.1% of the total G x E interaction for grain yield (P < 0.001). Of the 16 environments, 12 grouped into two clusters which largely corresponded to test locations. The tested genotypes revealed a wide variation for both static and dynamic yield stability measures. Compared to improved cultivars, farmers' landraces displayed higher average static stability (e.g. IPCA1; P = 0.017) and similar superiority indices (dynamic stability). These landraces are therefore a source of germplasm for breeding resilient barley cultivars. Staggered planting proved to be a useful method for evaluating genotype stability across environmental factors beyond location and season.

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