Effects of Weeds on Morpho-ecological Traits of Selected Range Grasses in Southern Kenya

Abstract

The invasion of weeds into rangelands is a precursor for loss of biodiversity, enhanced soil erosion, loss of wildlife habitats, and decrease in carrying capacity for livestock. These weeds are ferocious competitors, often show characteristics of high seedling vigour and short life cycles. The study sought to explore the interactions Chloris roxburghiana (CHLORIS), Cenchrus ciliaris (CECI), and Eragrotis superba (ERASU) under weed infestation. Four treatments were applied during the study: Continuous weeding (W1), weeding on the 4th week after seeding (W2), weeding on 6th week (W3) and the control (no weeding - W4). The grass species morpho-ecological parameters: plant tillers, grass height, grass density and biomass yield were measured at the grass bloom stage. A comparison of the treatment means and post hoc test separation of means statistical analyses were performed. The results illustrated a significant difference (P≤0.05) in morpho-ecological characteristics of all the weeding regimes. A Pearson correlation analysis showed a positive correlation between biomass (DM) and grass cover, grass density, plant height and tiller density parameters. Continuous weed management and weeding at 4th week of establishment showed the highest biomass performance for Cenhrus ciliaris, Chloris roxhburgiana and Eragrostis superba species with 1,0651.0 and 8,498.0, 5,185.6 and 4,408.2, 7,364.5 and 5,711.1 Kgs/ha DM respectively. While none-weeding and weeding at 6th week management demonstrated the least performance with 3,604.0 and 6,664.0, 2,441.6 and 3,149.4, 2,257.3 and 4,537.2 Kgs/ha DM respectively. A germination test for seed validity showed an average rate of Eragrostis superba (41%), Cenchrus ciliaris (35%) and Chloris roxburghiana (26%). A farmer survey conducted to determine the cost-effectiveness of applied weed management regimes illustrated that farmers who weeded their pasture farms within the first 3 years since establishment, yielded an extra output of 3kgs seeds, 48kgs crop residual (3.2, 15kg bales) and 138kgs (9.2, 15kg bales) quality grass pasture per acre/season. However, a differential analysis illustrated that the marginal cost was higher than the marginal revenue for pasture weeding with an estimated net marginal loss of between Ksh. 3,726.40 and Ksh. 5,226.40. From the findings, weed management practices has the potential to increase rangeland productivity. Therefore, the national and county governments, through the relevant departments of agriculture and livestock departments should come up with effective range management policy framework that will promote rangeland governance, restoration, pasture production, and livestock production to enhance rangeland livelihoods and ecosystem integrity. Subsidisation of important inputs in pasture production will ease costs of weeding operations, thus, VIII increasing returns to farmers. Also, it is crucial for the agriculture and livestock departments to structure policies that will easily link livestock producers and pasture farmers to reliable markets for their pasture produce and animal products.