Management and nutritive evaluation of Mucuna pruriens and Lablab purpureus-maize intercrops in the sub-humid highlands of northwestern Kenya.

摘要

Declining soil fertility and inadequate and low quality feed resources limit smallholder crop yields and dairy production in Kenya. Herbaceous legumes can provide an alternative to the use of commercial N sources for cereal crops and livestock production in these low external-input farming systems. Research reported in this dissertation was conducted to (1) determine the N contribution from relay-cropped mucuna [Mucuna pruriens (L.) DC. Var. utilis (Wright) Bruck] and lablab [Lablab purpureus (L.) Sweet cv. Rongai] to succeeding maize (Zea mays L.)-common bean (Phaseolus vulgaris L.) intercrop when part of the legume biomass is removed for fodder and (2) evaluate the nutritive value of these legumes when used as supplements for lactating cows fed napiergrass [Pennisetum purpureum (K. Schum) cv. Bana].;Relay-cropped mucuna and lablab survived the dry season producing a total biomass yield of 4 and 2.7 t ha−1 on the research station, and 2.3 and 0.75 t ha−1 on farmers' fields, respectively. The N contribution from mucuna and lablab residues were 78 and 57 kg ha −1 on station, and 49 and 12 kg ha−1 on farmers' fields. Defoliation of the legumes to a 10-cm stubble removed 52 and 76% of the above-ground herbage of mucuna and lablab, and the residue quality of the remaining stubble was lower (higher lignin and lower N concentration) than that of whole above-ground biomass.;Inclusion of the green manures in the maize-bean intercrop increased subsequent bean and maize yields compared to the natural fallow control, but crop yields were relatively low on farmers' fields where soil fertility was lower than on station. Defoliation reduced the nutrient contribution from the legume residues; the impact of defoliation was greater on lablab, which has a more upright growth habit than mucuna. The mean N recovery by maize across all sampling dates ranged from 21% for the cattle manure control to 52% following undefoliated lablab. The N recovery after defoliated mucuna was 45% compared to 35% for undefoliated mucuna. After 2 yr of consecutive residue application, yields of subsequent maize were greatest under defoliated mucuna and undefoliated lablab, possibly due to their lower quality (more stem and lignin) residue which may have improved synchrony of N release with N requirement of the crops.;Defoliation of relay-cropped mucuna and lablab to 10 cm provided 1 to 1.8 t ha−1 yr−1 of high quality livestock fodder. Supplementing mucuna hay and lablab hay to dairy cows fed a basal diet of napiergrass increased total dry matter intake, apparent DM digestibility, and daily yield of 4% fat-corrected milk compared to napiergrass alone. Utilization of the high nutritive value upper canopy of mucuna and lablab as livestock feed and soil incorporating the remaining stubble has potential for improving maize yield and performance of livestock in smallholder systems in Kenya.