Effects of Tillage Methods, Residue Retention, and Cropping Systems on Water Use Efficiency and Yield of Green Gram in Machakos County, Kenya

Abstract

Conservation agriculture is considered an effective practice of crop production in arid and semiarid lands (ASALs). Nonetheless, not much publication on the influence of conservation agriculture on green gram (Vigna radiata) in Kenyan ASALs has been documented. Against this backdrop, a field experiment was conducted to evaluate the effect of tillage methods, residue retention and cropping systems on green gram yield and water use efficiency. The experiment was laid out in a randomized complete block design with a split-split plot arrangement and replicated three times. The main plots were tillage methods: conventional tillage, no-till, and tied-ridges. Sub-plots were residue retention at 3 t/ha plant straw and bare ground. Sub-sub-plots were two cropping systems: intercrop and sole crop. Data collection and analysis were done on plant height, shoot biomass, root biomass, number of active nodules, nodules biomass, number of seeds per pod, number of pods per plant, thousand seed weight, and seed yield. Soil moisture content was determined by sampling soil from each plot at sowing and at physiological maturity and water use efficiency was computed. Tied-ridge recorded the highest green gram seed yield (1.359 t/ha) while the lowest (0.388 t/ha) was recorded under no-till. Residue retention recorded a higher (60.21%) green gram seed yield. Intercropping suppressed green gram yields significantly (p<0.05) by 44% compared to sole crops. Green gram grown as sole crop under tied-ridge and residue retention reported increased seed yield by 21.6%. Sole cropping system under tied-ridges with residue retention increased soil moisture content by 40.4%. Use of tied-ridges increased water use efficiency by 5.1 kg-/mm in comparison with conventional tillage and no-till. Residue retention increased water use efficiency by 3 kg/mm compared with bare ground. Sole crop had significantly higher water use efficiency (9 kg/mm) compared with intercrop (7.5 kg/mm). The results implies that sole green grown under tied-ridges with residue retention improved soil moisture content hence increasing water use efficiency. Consequently, leading to improved green gram growth and yield. Sole cropping system under a tied-ridges with residue retention emerged the most effective combination for higher green gram yield. Thus, the study concludes that combination of tied-ridges, residue retention and sole crop is potential to improve soil water storage, leading to increased water use efficiency and ultimate yield increase. Integrated approach is recommended toward practicing conservation agriculture in arid and semi-arid environments.