FARMYARD MANURE, LIME AND ZINC IMPROVE MAIZE (Zea mays) AND DESMODIUM (Desmodium intortum) RESPONSE TO MINERAL FERTILIZERS IN VIHIGA COUNTY

Abstract

Persistent food and fodder yield gaps witnessed in Vihiga County even with the application of recommended fertilizer are becoming an issue of concern to most smallholder farmers residing in the region. Closing these yield gaps may be achieved through blending of soil amendments that address several soil constraints such as acidity, macro and micronutrients deficiencies. Firstly, the study sought to identify the commonly used soil amendments by smallholder farmers in Sabatia and Hamisi Sub-counties of Vihiga County through a baseline survey. Secondly, in the same region, we evaluated the effect of adding farmyard manure (FYM), lime and zinc (Zn) to the recommended mineral fertilizers on maize and desmodium yields and on selected soil parameters. This was achieved through conducting four on-farm trials in two subsequent seasons; long rain (LR) and short rain (SR) seasons of 2015. Although the survey findings indicated that majority of the farmers apply both organic and mineral fertilizers to increase crop yields, maize yields were still below the regional production potential of 6-8 t ha-1. Results from the on-farm trials indicated that adding FYM, lime and Zn together with NPK (17:17:17) increased maize yields by 45% above the 4 t ha-1 obtained from the sole application of NPK fertilizer. On average, Maize yields during the long rains almost doubled those obtained in the short rains season. For Desmodium, biomass yields obtained from the first cutting regime during (LR) were significantly lower compared to those obtained from the subsequent cutting regimes in (SR); the second (180 DAP) and third cutting (240 DAP). Application of FYM at 3 t ha-1 in combination with P fertilizer at 30 kg ha-1 gave the largest desmodium biomass yields of 7.5 t ha-1 which was significantly higher than the other treatments irrespective cutting regime. The largest changes in soil pH and available P were observed when lime was combined with FYM irrespective of the application rate in both maize and desmodium plots. The control plot showed minimal increases. In all the amended plots, K and Zn concentrations increased significantly (P<0.05) in the soil apart from the sole application of mineral fertilizer. A significant (P<0.05) and positive correlation between maize yields and P uptake were reported for all the treatments with the treatment NPK + Zn (3 kg ha-1) + FYM (2 t ha-1) + Lime (2 t ha-1) giving the strongest correlation (r = 0.72). From this study, it can be concluded that the application of FYM at 2 t ha-1, Zn and liming the soils improves the use efficiency of mineral fertilizers and consequently increases maize yields. In addition, combining P at (30 kg ha1) with FYM either at 3 or 4 t ha-1 is the best bet for desmodium biomass production.