Effects of combined application of phosphorus and sulfur fertilizers on agronomic traits and protein content of supplementary irrigated haricot bean (Phaseolus vulgaris) varieties in Raya Valley, Northern Ethiopia

Haricot bean is primarily grown in Ethiopia for human consumption and export earnings. A market demand for haricot bean, both in the domestic and export market, has triggered the production of haricot bean in selected areas of Ethiopia though its production is constrained by several factors such as poor soil fertility and erratic rainfall. This study was carried out to investigate the combined effect of phosphorus and sulfur fertilizers on yield, yield related traits and protein content of haricot bean (Phaseolus vulgaris) varieties at the research field of Mekoni Agricultural Research Center during 2016/17 cropping season. The experiment was laid out in split plot design where varieties were assigned to the main plots and fertilizer rates to the sub plots in three replications. Three phosphorus (P) rates (10, 20 and 30 kg ha-1) were combined with four sulfur (S) rates (15, 30, 45 and 60 kg ha-1) and applied in combination to Melka Awash-98 and Nasir varieties. Data on phenological, agronomic and quality traits were collected and determined. Partial budget analysis was carried out to assess the profitability of the applications. P-S fertilizer treatments were  significantly affected by varieties. Treatments were significantly affected by varieties and the imposed P and S rates. The interaction effect due to variety by fertilizer the two factors significantly affect days to flowering, plant height, hundred seed weight and protein content. Tallest plants, fewer days to flowering and maturity, many pods/plant, heavier seeds, higher grain yield ha-1 and better protein content were recorded where the fertilizer application rate was 20 kg ha-1P and 30 kg ha-1 S for both varieties. Grain yield ranged from 1520 to 3000 kg ha-1 depending on P-S fertilizer rates and varieties. Nasir variety seems to be superior over Melka Awash-98 for most traits except protein content. However, production of Melka Awash-98 under 20 kg ha-1P and 15 kg ha-1 S fertilization tend to be more economical as it resulted in highest net benefit return. Although not profitable, planting Melka Awash-98 using an application rate of 20 kg ha-1P and 30 kg ha-1 S could be suggested for use in the area to ensure earliness and high grain yield.