ABSTRACT
A field experiment was carried out from Feb-May 2012 at the irrigation Research Farm, Institute of Agricultural Research, Samaru, to determine the yield and water use response of watermelon under Deficit irrigation and mulch. The experiment consisted of four levels of irrigation water application depth of 100% (I100), 75% (I75), 50% (I50) and 25% (I25) replacement of moisture depleted and three mulch types (Rice straw mulch MRS, Black polyethylene mulch MBP, and No mulch MNO) giving a total of 12 treatments laid in a randomized complete block design(RCBD). Water was applied to each basin using a calibrated short length PVC pipe serving as an orifice installed in each basin. The soil moisture was monitored throughout the crop growing season with gypsum block installed at three different depths (0 -15, 15 - 30 and 30 - 45 cm) below the soil surface. The experimental crop was watermelon, which was harvested at maturity, and then the fruits were counted and weighed. The yield obtained ranged from 7.38 t/ha to 58.49t/ha. The least yield value was obtained from the treatment with irrigation at 25% replacement of moisture depleted and No mulch (I25MNO) while the highest yield value was obtained with irrigation at 50% replacement of moisture depleted and black polyethylene mulch (I50MBP). The seasonal crop evapotranspiration ranged from 119 to 373 mm with the least value obtained at I25MNO while the highest value was obtained at I100MNO. The highest crop water use efficiency and irrigation water use efficiency is at I50MBP with 347.39kg/ha-mm and 268.55kg/ha-mm respectively while the least was at I25MNO for crop water use efficiency with 33.56kg/ha-mm and at I100MNO for irrigation water use efficiency with 32.09kg/ha-mm. The Ky values for the total growing season obtained were 1.3895 for MNO, and no relationship for MRS and MBP was observed. The Kc values ranged from 0.42 to 0.55 for initial stage, 0.5 to 1.01 for development stage, 0.69 to 1.09 for mid season stage, 0.41 to 0.87 for late season stage respectively. Irrigation at 50% replacement of moisture depleted with black polyethylene mulch gives higher yield, thereby reducing the volume of water and increasing efficient use of water which is the major limiting factor during dry season farming in the region.