Effect of cutting frequency on productivity of five selected herbaceous legumes and five grasses in semi-arid tropical Kenya

Abstract

Growth and effect of harvest intervals on dry matter (DM) production of 5 herbaceous legumes ( Chamaecrista rotundifolia cv. Wynn, Macroptilium atropurpureum cv. Siratro, Stylosanthes guianensis cv. Cook, S. hamata cv. Verano and S. scabra cv. Fitzroy) and 5 grasses ( Brachiaria decumbens cv. Basilisk, Cenchrus ciliaris cv. Gayndah, Chloris gayana cvv. Callide and Katambora and Setaria sphacelata cv. Narok) were evaluated for more than 3 years in the semi-arid tropics. Plant numbers, height, spread and plot cover were monitored for the initial 12 weeks following seedling emergence. Subsequently, in addition to monitoring plant numbers, both legumes and grasses were harvested twice in 15 weeks at different intervals (3 then 12 weeks, 6 then 9 weeks, 9 then 6 weeks and 12 then 3 weeks) in the wet seasons to assess DM production. Plant numbers at 12 weeks were good for legumes (9‐19 plants/m 2 ). Over time, Wynn and Verano showed a marked increase in numbers while plant numbers of Siratro, Cook and Fitzroy remained fairly stable in most seasons and declined towards the end of the study. For the grasses, Basilisk and Narok had the highest plant numbers (11‐12 plants/m 2 ) at establishment while no seedlings of Katambora emerged until the second wet season [long rains (LR) 1994]. Plant numbers of all grasses tended to decline with time. Among the legumes, Siratro displayed the best spread and plot cover while Basilisk had the highest spread and consequently the highest plot cover among the grasses. Harvesting sequence had no significant effect on DM yield of legumes but there were differences between species in all seasons. Siratro had the highest DM yield throughout, while Wynn and Verano had the lowest. There was a significant (P < 0.05) interaction between species and harvest interval for the grasses. Basilisk out-yielded all grasses for most harvest intervals during LR 94, SR 94 and LR 95 and was more productive at the 12/3 weeks cutting interval. Callide had the lowest yield in these seasons, but improved towards the end of the study. For both legumes and grasses, DM yield was closely related to rainfall, being highest during SR 94.