Effect of Deficit Irrigation on Dry Matter Yield and Water Productivity of Young Harerghe Coffee Genotypes at Jimma, Southwest Ethiopia

Coffee plays an important role in Ethiopia's economy; it is a major source of revenue, accounting for almost 70% of total export earnings. However, the recurrent drought and seasonal moisture deficit impacted the coffee production. Therefore, the experiment was conducted to investigate the performance of Harerghe coffee genotypes under different deficit irrigation levels at Jimma (Malko) in rain shelter. Six Harerghe coffee genotypes seedlings with age of eleven months were subjected to three deficit irrigation levels (40, 80 and 120% of ETc) with randomized complete block design, which replicated three times. It was observed that different deficit levels significantly affected water productivity, dry mater yield production and growth traits for all genotypes. Based on mean values of total dry matter production, genotype H-823, H-957 and H-981 were classified as more productive than H-929 and H-979 under 80%ETc irrigations, while H-929 found to be less productive in terms of dry matter production. The 40%ETc of irrigation significantly improved water productivity, but, 120%ETc considerably reduced the water productivity of most genotypes. As supply of irrigation increased the water productivity was linearly decreased and opposite trend is observed for dry mater yield and plant growth. Regardless of genotypes, almost all genotypes differentially responded to irrigation amounts, the highest and lowest water productivity had produced from H-823 and H-929, respectively, but similar values was observed among H-857 and H-981. The genotype X irrigation interaction significantly impacted all measured plant traits. Among genotypes, H-823 produced highest water productivity under 80%ETc and followed by H-674, H-857 and H-929 under 40%ETc, while the lowest had from H-981 and H-674 with 120%ETc. In contrast, the 40%ETc significantly reduced dry matter production as well as inhibit plant growth. But, under 80%ETc coffee seedlings gave medium water productivity, maximum dry matter and promoted vegetative growth. However, this finding should further proofed with replicated field experiments under different agro-ecological conditions.