CROP WATER USE, GROWTH AND YIELD OF FADAMA-GROWN PEPPER (Capsicum annuum L.) AS INFLUENCED BY MULCHING AND IRRIGATION IN AKURE, NIGERIA

Abstract

Inland valley swamps (inland floodplains/fadama) are characterized by shallow water table depths. The shallow water table can supply important fraction of crop water use (ET) via capillary rise (upflows), this may constitute a significant component in the root zone water balance of crops. The pattern of water use, growth and yield of pepper (Capsicum annuum L. variety Tattasai) grown in the dry season in an inland valley swamp was investigated in Akure, a humid zone of Nigeria. The study involved two sets of experiments, which separately determine the effects of mulching and controlled gravity-drip irrigation system. In the first experiment (November 2008 to February, 2009), the effects of mulching materials (transparent and black polythene sheets and dry grass) on soil moisture regimes and plant water extraction, growth and fruit yield of Pepper were evaluated. Plots size was 5 x 4m and seedlings were transplanted at a spacing of 60 x 60 cm. Treatments were assigned to field plots using randomized complete block design with three replications. The second experiment, which was conducted between January and April, 2009, examined the effects of water application once or twice weekly using gravity-drip irrigation system on the pattern of water use, growth and fruit yield of pepper. From both experiments, data were collected on pattern of pepper water extraction and agronomic parameters of root and shoot biomass, leaf area, flowering and fruiting characters of pepper. Mulching significantly reduced soil temperatures which under grass and polythene mulch were lower compared with unmulched plots. Mulching considerably enhanced soil moisture conservation at 10cm depth compared with the control. There were changes in soil water potential (moisture tension) during pepper growth. Soil moisture tension varied within the crop root zone, increases down the soil profile, and varied within the crop root zone: surface soil (0 – 20 cm) and subsoil (20 – 60cm). The values ranged from -11 to -26 KPa and -2 to -16 KPa for the respective seedling establishment (1 to 7 WAT) and reproductive phase to crop maturity (7 -12 WAT). Values ranged from -43 to -54 for surface soil and -30 to -41 at subsoil depths. In general, soil water potentials (tension) ranged between -11 to -54 KPa and -2 to -41 KPa at surface and subsoil depths respectively. The sequence of depletion and replenishment of soil moisture differed between the irrigation regimes. Under once and twice weekly irrigation regimes, moisture contents varied within the crop root zone and increased downward within the profile depths. Soil moisture contents were lowest for plots that were irrigated once weekly compared with twice weekly irrigation. Soil moisture contents within the crop root zone ranged between 14.7 and 11.8% for surface soil and 14.9 to 14.5% at the seedling stage. It reduced to as low as 10.8 and 11.9% respectively at flowering and fruiting phases. Application of mulch significantly (P<0.05) increased root and shoot biomass and fruit yield over bare ground. The total fruit harvested from mulched pepper were greater than in unmulched plants. Irrigation regimes involving variable rates of water application (once and twice weekly) affected growth and yield characters of pepper. The values of roots and shoot dry weights as well as leaf area were higher in twice weekly irrigation. Irrigation twice weekly delayed the onset of flowering and this translated to higher efficiency of water use for fruit production. Higher number and weights (g) of fruits harvested were obtained for pepper plants irrigated twice per week. In mulching and irrigation experiments, pepper plants subsisted on residual soil moisture storage in the root zone and capillary rise/upflows from the water table. The use of mulch and drip irrigation improved growth, fruit yield and water use efficiency of pepper in the dry season.