Biomass production of hairy vetch and Egyptian clover as affected by sowing dates under warm and hot semi-arid conditions

Abstract In Southern Africa, feed gaps towards the end of the cool–dry season are a challenge that needs addressing by the timely growth of suitable forage species. Therefore, we assessed the adaptation of the species vetch ( Vicia villosa Roth) and Egyptian clover ( Trifolium alexandrinum L.) with one cultivar of each. A fully irrigated experiment consisting of a factorial combination of species, sowing dates (early, late) and sites (warm and hot environments) was conducted across two separate cool–dry seasons. Data were collected at successive harvest dates (hd1, hd2 and hd3) i.e. about 50, 70 and 90 days after sowing, respectively. The accumulated aboveground biomass was affected by the effect of site × sowing date irrespective of harvest date. At hd3, aboveground biomass was further affected by the effect of site × species. Site-specific sensitivity to temperature, photoperiod and soil type influenced the vegetative development of the selected species. Early sowing compared to late sowing achieved about 60% higher biomass accumulation. The species effect was major with higher vetch biomass than clover (2943 v. 961 DM kg/ha), and (1459 v. 1066 DM kg/ha) at the warm and hot sites, respectively. Moreover, clover showed a lower DM response to irrigated water (4.7 against 13.5 kg DM/ha/mm) as compared to vetch. Thus, vetch was the better-adapted crop providing adequate biomass across harvest dates and under different environments. Adoption of these species to alleviate feed gaps is possible when irrigated; however, implementation of the genetic variability of cultivars should also be assessed.