Effect of Water Stress and Phosphorus Fertilizer Rates on Growth and Seed Yield of Cowpea Under El-Arish Condition

Abstract

Two field experiments were carried out during summer seasons of 2014 and 2015 at Exp. Farm, Fac. Environ. Agric. Sci., El-Arish, North Sinai, Egypt, to study the effect of water stress and phosphorus rates on growth, yield and its components as well as water and phosphorus use efficiency on cowpea cv. '' Kafr-El Sheikh'' grown under sandy soil conditions using drip irrigation system. The experiment included 12 treatments, which were the combinations of three water levels; viz., 50, 75 and 100 % of irrigation water requirements (IWR) and four rates of phosphorus (0, 20, 40 and 60 kg P 2 O 5 / fed.). The results show that increasing irrigation deficit increased water saving and water use efficiency (WUE), however it reduce seed yield/fed. The highest value of water saving and WUE was obtained from 50% IWR treatment. However, the highest value of phosphorus use efficiency (PUE) was achieved by treatment received 40 kg P 2 O 5 /fed. as well as, significant differences among irrigation water levels and phosphorus rates and their interactions were detected for all studied traits in both seasons. The high level of IWR (100%) gave the best values for all traits under study without significant differences when compared with 75% of IWR for some traits, except protein % which increased with addition of the lowest level (50% IWR) in both seasons. Application of phosphorus at rates of 40 or 60 kg P 2 O 5 /fed. exhibited the highest results for all studied characters in both seasons. The best combinations treatments for growth and yield were supplying cowpea plants with 100 % of IWR and fertilizing the highest two rates of phosphorus (40 or 60 kg P 2 O 5 /fed. for all traits, followed by the medium level (75% of IWR) with the both high rates of P 2 O 5 .