Response of Selected Green Gram (Vigna Radiata) Varieties to Varying Moisture Regimes and Adaptation to No-tillage With Residue Retention

Abstract

Green gram (Vigna radiata L.) is a hard pulse well adapted to marginal areas. Moisture stress is considered the most limiting factor in green gram production resulting to low yields experienced by farmers. With climate change bound to worsen the situation, soil moisture conservation strategies with minimum soil disturbance, for instance, no-tillage system could be adopted by farmers to ameliorate the situation. Despite breeding advances to adapt green gram to drought, mechanisms regulating responses to moisture stress are only partially understood. In addition, evidence on the adaptation of green gram to no-tillage and residue retention systems is limited. In the backdrop of the existing gaps in knowledge, both greenhouse and field experiments were conducted to: (a) evaluate response of selected green gram varieties to varying moisture regimes, and (b) determine the response of selected green gram varieties to no-tillage system. Greenhouse trials were conducted at University of Nairobi, Kabete field station. Treatments comprising five selected green gram varieties N26, KS20, Biashara, Karembo and Ndengu Tosha and four moisture regimes of 40%, 60%, 80% and 100% field capacity (FC) were laid out in randomized complete block design. Field experiments were conducted in Machakos county of Southern Kenya at KALRO Katumani and in a farmer’s field in Kikesa village. Treatments consisting of two tillage systems (no tillage and conventional tillage) and five selected green gram varieties (N26, KS20, Karembo, Biashara and Ndengu Tosha) were laid out in randomized complete block design with a split plot arrangement. Tillage systems were assigned to main plots while varieties formed the subplots. In the first objective, days to 50% branching, flowering, podding and maturity were determined, as well as corresponding number of nodules, active nodules and nodules dry mass. Plant height and leaf greenness were measured at branching and flowering. Root length, root angle and root dry mass were also measured at branching and flowering. At physiological maturity number of pods per plant were recorded. At harvesting, data on number of seeds per pods, pod length and seed yield were measured. In the second objective, crop phenology and crop growth traits of selected green gram varieties under the two tillage systems were measured. Generally, the five selected green gram varieties varied significantly (P<0.05) under four moisture regimes and tillage systems. Variety N26 was late maturing while the other four varieties were intermediate in number of days to maturity. Additionally, N26 also had the highest number of total nodules and active nodules under four moisture regimes and no tillage system. Green gram varieties grown under 60%, 80% and 100% FC were greener and produced a greater number of pods and yield compared to crops in 40% FC. xiv While the varieties did not show any significant difference in root length and root angle, significant differences P<0.05 in seed yield were recorded among the varieties as well as the moisture regimes. In objective two, selected varieties varied significantly P<0.05 in phenology, crop growth traits and yield. However, no significant differences were recorded between conventional tillage and no tillage systems; this ascertains that breeding of green gram varieties in Kenya has not selected for response of green gram varieties to no tillage system. Although N26 performed better compared to other varieties in both experiments, more attention should be focused on the recently released varieties with early maturity trait. Results of this study imply that evaluation of released green gram varieties to varying moisture regimes and no tillage system could facilitate adoption of soil moisture conservation measures by farmers to achieve higher yields and curb climate change challenges