Irrigation Scheduling Effects on Components of Water Balance and Performance of Dry Season Fadama-Grown Pepper in an Inland-Valley Ecosystem in a Humid Tropical Environment

Abstract

This study examined the contribution of water table via capillary rise and irrigation, to soil moisture storage and water use of pepper (Capsicum annuum var. Tatase), grown in an inland valley swamp (flood plain) in the dry season in a humid zone of Nigeria. The contribution of water table (capillary rise/upflows: Cg) to root zone moisture was quantified based on the soil water balance. Capillary rise was taken as the difference between estimated crop evapotranspiration (ETa) and measured soil water depletion (SWD). Irrigation regimes consisted of water application at weekly (7-day) and fortnight (14-day) interval using gravity-drip system. In the respective 7-day and 14-day irrigation intervals, shoot biomass were 153 and 141g plant-1 while fruit yields were 8.6 and 7.9 t ha-1 which constituted about 8.2% yield reductions were obtained under 14-day compared with 7-day irrigation. Capillary rise ranged from 2.3 to 5.2 mm which amount to 81 and 124% of pepper evapotranspitaion (ETa) across the sampling periods. The results showed that the weekly and fortnight irrigation intervals produced seasonal ET were 109 and 83 mm, soil moisture contents of 201 and 164 mm within crop root zone and water use efficiencies of 0.14 and 0.19t/ha/mm. Soil moisture storage and its depletion, Cg, crop evapotranspiration (ETa) and relative water use (ETa/Eo) differed in the growth stages of pepper, were influenced by irrigation regimes, groundwater table depth, and the prevailing weather conditions (vapour pressure deficit, temperature, thermal time) during pepper growth. Seasonal trends of the relative water use indicate the inability of soil moisture storage to satisfy pepper water requirements (ETa). Weekly irrigation offered the best compromise in the circumstance of declining water table depths and high climatic demand of the dry season in the site of study. Results show that irrigation regimes imposed optimized the contribution of groundwater to soil moisture storage and water use of pepper.