Evaluation of the Effect of Mavuno Phosphorus-Based Fertilizer and manure On Soil Organic Carbon and Maize Productivity in Vihiga and Siaya Counties of Western Kenya

Abstract

Low soil organic carbon in western Kenya can be attributed to low soil fertility. The soils are predominantly phosphorus (P) fixing making the applied P-based fertilizers not to benefit target crops fully. Efforts to improve and maintain soil fertility through fertilization has been ongoing in western Kenya for years, despite. this, soil degradation; the inability of soil to support plant growth associated with unfavorable soil conditions is still prevalent. Positive relationship between organic and inorganic fertilizers on soil properties has been suggested. Mavuno fertilizer provides more nutrients to plants than common fertilizers used in the region due to its additional chemical properties. Mavuno fertilizer has lO%N, 26%P20S, 1O%K20,4%S, 8%CaO, 4%MgO, B, Zn, Mo, Cu and Mn. The main objective of this study was to assess the effect of Mavuno P-based fertilizer and manure on soil physical and chemical properties on degraded soils in Nyabeda, Nyalgunga (Siaya) and Emusutwi (Vihiga) sub-locations, western Kenya. Specific objectives were to: determine seasonal effect of Mavuno phosphorus-based fertilizer and manure application on SOC levels; determine residual Olsen-P attributed to their seasonal application; measure maize grain and stover yield following their application and assess levels of soil pH and bulk density. The study was c!rried out on CIAT-TSBF fields where Mavuno P-based fertilizer (20 KgPha-1) and manure (2tha-1) has been applied for 6 years. A randomized complete block design (RCBD) was used in the study. Soils were sampled from; control, manure, Mavuno and manure+Mavuno to a depth of 20cm, from eleven farms; 4 in Emusutswi, 4 in Nyabeda and 3 in Nyalgunga during the last 3 seasons. One thirty two soil samples were analyzed using standard methods for C%, Olsen-P (mgl'kg"), soil pH and bulk density (g/crrr'), Mavuno P-based fertilizer and OM had no significant variation on SOC, Olsen-P and soil pH between treatments in both sites, however seasonal variation was observed; the soil bulk density was significant in Emusutswi and Nyabeda, but not in Nyalgunga. Mavuno resulted in remarkable increase in maize grain and stover yield, making it appropriate for low fertility and P-fixing soils. Mavuno has the potential of sustaining soil productivity, when adequate amount is applied thus managing soil acidity and lowering soil bulk density through improved SOM. Understanding the effect of continuous application of P-based fertilizers and manure is essential for sustaining soil productivity among small holder farms of western Kenya.