Phosphorus and Sulfur Effects on Growth and Physiological Parameters of Snap Bean (Phaseolus vulgaris L.) Under Different Irrigation Regimes on Andosol in the Central Rift Valley of Ethiopia

Abstract

Snap bean is a leading exportable vegetable crop and an important source of nutrition for consumers in many parts of Ethiopia including the  Central Rift Valley. However, it’s growth and physiology parameters are very stunted and poor due to inadequate moisture and poor soil fertility  effect. Lack of phosphorus and sulfur fertilizers and irrigation regime are stunted and poor growth and physiology of snap bean. Therefore; field  experiment was conducted at Melkassa Research Center off season in 2017 and 2018 to evaluate the effect phosphorus and sulfur fertilizers  application under different irrigation regimes on growth and physiology of snap bean. The experiment was laid out in split-plot design with three  replications. Four drip irrigation regimes (100, 85, 70 and 55% ETc) were assigned to the main-plots. Four fertilizer types (0 kg both P and S ha^-1, 21  kg P ha^{- 1}, 30 kg S ha^-1 and 21 kg P ha^-1+30 kg S ha^-1) were randomly assigned to the sub-plots. The analysis of variance revealed that the  interaction effect of irrigation regimes and fertilizers application had a significant (P<0.05) effect on LAI and CGR. The highest LAI of snap bean was  recorded from interaction of 100% ETc with control and S30 kg ha-1 with 3.32 and 3.18, respectively. Whereas, the lowest LAI was obtained from  interaction of 55% ETc with S30 kg ha^-1 and control with values of 1.44 and 1.46, respectively. The highest CGR of snap bean was recorded from  interaction of 100% ETc with S30 kg ha^-1 (17.45 g m^-2 day^-1) followed by the control (15.66 g m-2 day^-1) and with P21 kg ha^-1+S30 kg ha^-1 (14.46 g  m^-2 day^-1). The lowest CGR was obtained from interaction of 55% ETc with control (3.33 g m-2 day^-1). The main effect of various irrigation regimes  had a significant (P<0.05) effect on NDVI, IPAR and stomata conductance parameters. On the other hand, application of different fertilizers types  had no significant effect on all the parameters. The best growth and physiological parameters of snap bean was recorded from the interaction effect  of 100 and 85% ETc with different fertilizers types. Therefore; 85% ETc irrigation regime without P and S fertilizers where scarcity of irrigation  water is limiting and 100% ETc irrigation regime without P and S fertilizers where there are no water shortages, in the rift valley area with similar soil  properties.