EFFECT OF SOIL AMENDMENTS ON THE PERFORMANCE OF SELECTED AFRICAN INDIGENOUS VEGETABLES IN UASIN GISHU AND TRANS NZOIA COUNTIES

Abstract

African Indigenous Vegetables (AIVs) have high nutritive value, require less inputs and can be a reliable source of income to resource challenged families. However, their production in western Kenya is hampered by limited information on their soil nutrition requirements. To meet these needs two studies (Agronomic trial and soil pH study) were conducted during the rainy season and dry season, which was between July 2013 and March 2014 under drip irrigation. The studies aimed at determining the best fertilizer-variety combination and ideal soil pH level in the two regions for growing AIVs. The experiments were laid out in a Randomized Complete Block Design in a split-split plot arrangement for the agronomic trial and a split-plot for pH study. Both experiments were replicated three times. In the agronomic study, three vegetable types formed the main plot treatments which included Spider plant (Cleome gynandra), African Nightshade (Solanum scabrum) and Amaranthus spp. Varieties formed the sub plot treatments which were Local variety, UG-SF-15 and ML-SF-29 for spider plant; Local variety, UG-AM-40 and Ex-Zim for Amaranthus spp and Local variety, BG-16 and SS-49 for African nightshade. Fertilizer treatments formed the sub-sub plots and include Mavuno fertilizer, poultry manure and the control. In the soil pH study, species (African nightshade, Amaranths & Spiderplant) formed the main plot treatment while the lime rates formed the sub plot treatment. Data were collected on cumulative fresh yield, soil pH trend and characterization, biomass and nutrient concentration, root biomass and root length density and chlorophyll content at flowering. Data were subjected to ANOVA using SAS version 9.3. In the agronomic study, the results exhibited that fertilizer application significantly (p=0.05) increased cumulative fresh yield of all selected varieties of the three AIVs. In African nightshade, developed variety BG-16 with mavuno fertilizer had the highest mean cumulative yields in Eldoret (9,980 kg/ha) and Kitale (13,880 kg/ha). In Amaranths, developed variety UG-AM-40 with poultry manure recorded the highest yields in Eldoret (4,490 kg/ha) and Kitale (6,060 kg/ha). In spiderplant, local variety (LV-SP) and developed variety (UG-SF-15) recorded highest yields with mavuno fertilizer while developed variety ML-SF-29 had highest yields in Eldoret (2600 kg/ha) and Kitale (3830 kg/ha) with poultry manure. In the soil pH study, acid soils responded to liming, whereby all the liming rates were significantly different at P=0.05. A mean pH of 6.33 for liming rate 4.1625 t/ha , 5.78 for liming rate 2 t/ha and 5.18 for the control were achieved. Generally, in all the species, fresh biomass at floweing was highest at lime rate 2 t/ha with a target pH of 5.5. For dry biomass mixed response was exhibited with Amaranth recording highest biomass at lime rate 2 t/ha (2370 kg/ha), spiderplant at zero liming(1350 kg/ha) and African nightshade at lime rate 4.16 t/ha with a target pH 6.5 (1340 kg/ha). In all the vegetable species, %N and % P in the plant tissue increased tremendously in the rainy season though no significant differences (p=0.05) were exhibited. Root biomass increased with increase in lime applied. In all the species zero lime treatment had the lowest dry root biomass. There were significant differences in spider plant and amaranthus (P=0.05) whereby, treatments with zero lime (NL0 and AL0) were significantly different from the other lime rates. However, in spiderplant there were no significant differences (p=0.05) between the lime rates. Overall, the studies concluded that yields of AIVs will greatly increase with utilization of improved germplasm, use of appropriate fertilizer and maintaining ideal soil pH through liming of acid soils.