Response of irrigated tomato (Solanum lycopersicum Mill) to mulch application rates

Rapid decline in available water for crop production has led to the adoption of irrigation schedules for meeting water supply throughout cropping seasons. Nonetheless, the loss of water from soil often results in spells of water stress between schedules, which adversely affect crop yield. Hence, the use of mulch in conserving soil moisture in irrigated farming is becoming popular among farmers. In this study, a two-year screenhouse pot experiment was conducted to evaluate the effects of Pennisetum purpureum (Pp) mulch on tomato (Roma variety) grown in daily irrigation (IF_daily), irrigation at 3-days interval (IF₃), and irrigation at 5-days interval (IF₅) conditions. The Pp mulch was chopped to 5 cm and applied on the soil surface of each experimental pot at 1 t ha^-1 (Pp₁), 2 t ha^-1 (Pp₂), 3 t ha^-1 (Pp₃), and 4 t ha^-1 (Pp₄). These rates were compared against a bare soil as control (Pp₀). The treatments were laid in a completely randomised design with four replicates. Tomato yield decreased by 53.6% and 26.6% in IF₃, and 86.2% and 65.0% in IF₅ compared with IF_daily in years 1 and 2, respectively. Among mulch rates, Pp₄ and Pp₃ increased tomato yield respectively by 107.5% and 99.9% compared with Pp₀, while Pp₂ and Pp₁ were similar in year 1. In year 2, mulch increased tomato yield by 84.1% (Pp₁) - 215.3% (Pp₄) and contributed substantially to tomato yield in IF_daily (R² = 0.99; p < 0.01); IF₃ (R² = 0.93; p < 0.01); and IF₅ (R² = 0.25; p < 0.05). However, withdrawing irrigation at 5 days interval was detrimental to tomato yield production.