*James D., **Suleiman I. T. and **Abdullahi, M. D.
*National Centre for Agricultural Mechanization (NCAM), Ilorin.
**Samaru College of Agriculture/Division of Agricultural Colleges, Ahmadu Bello University, Zaria.
Corresponding email: iliyas.tsuleiman@gmail.com
ABSTRACT
In the northwestern region of Nigeria, Samaru, Zaria, a season experiment was conducted to estimate yield response to water stress and derive the crop coefficient of cowpea using the single crop coefficient approach with a gravity drip irrigation system and mulch. The treatments comprised three levels of water application depths (50, 75, and 100% soil moisture deficit (SMD) and three types of mulching (Black polythene mulch (BPM), Rice straw mulch (RSM), and no-mulch (NM)}. The treatments were laid out in randomized complete block design (RCBD) and replicated three times. The result obtained from the research showed that the highest seed yield of 1499.8 kg/ha was obtained when the cowpea crop was irrigated at 75% soil moisture deficit with black polyethylene mulch (I75BPM). The lowest yield of 800.4 kg/ha was obtained when irrigation was done at 50% SMD and no mulch (I50NM). The highest seasonal water use was obtained at I100NM with 242 mm and the least is at I50BPM with 120 mm. The highest irrigation water applied is at I100NM with 283.15 mm and the least is at I50BPM with 133 mm. The crop response factor (Ky) values obtained were 0.83 for NM, 0.80 for RSM, and 0.79 for BPM. The crop coefficient factor (Kc) values range from 0.28-0.71 for initial stage, 0.36-0.97 for development stage, 0.27- 0.64 for mid-season stage, 0.23-0.58 for harvesting stage. The seasonal yield response to water stress as indicated above shows that cowpea exhibits a moderately sensitive and linear response to water stress. The results suggest that cowpea is likely to give significantly higher grain yield when a nearly optimal water supply is provided with Black polythene at 75% of soil moisture deficit.