Soil Fertility Management and Impact on Sweet Potatoes - Soybeans Growing in Makunga (Kakamega) and (Kibargoi) Elgeiyo Marakwet Counties

Abstract

Sweet potato is a perennial storage tuber crop grown as a food and/or cash crop. Soybean is a multipurpose crop grown for human food, livestock feed, soil fertility improvement, income generation and oil production among the smallholder farmers. Production of sweet potatoes in Kenya is however low due to various factors and constrains low soil fertility inclusive. This paper addressed soil fertility management and its effect on rotational cropping and the use of inorganic fertilizers on soybean - sweet potatoes production. The study was carried out in two regions of Kenya; Kakamega County (Makunga sub County) and Elgeiyo Marakwet County (Kibargoi sub County). The study incorporated 147 respondents from the two regions with 42 in Kibargoi and 107 in Makunga. Sweet potato growing was important to 85.2% of respondents as food crop and 79.8% as a cash crop. The sweet potatoes varieties grown in the areas were dominated by Yellow fleshed, Purple fleshed, Vita and Kabode. Soybeans were grown by 7.1% in Kibargoi and 48.6% in Makunga. The common varieties included local, SP3, SP24 and SP25. The soybeans was consumed by 30.9% and grains used as alternatives to milk. The results indicated that farms where sweet potatoes were grown and organic fertilizers used, the relationship was relatively significant (r=0.158). Soybeans had a negative correlation with organic fertilizers with an r=-0.223, this interprets that the application of inorganic fertilizers to soybeans does not affect its output or yield. The fertility of soils were rated moderate by 81.2% while 8.7% rated fertility high (Kibargoi only). The loss of fertility is attributed to soil erosion 45.6% and previous growing of sugarcane in Makunga was cited as a challenge. Application of fertilizer on crops for fertility management was done by 65.1% (97) of the total respondents with 89.7% (96) from Makunga applying fertilizers and 2.4% (1) applying fertilizers to farms in Kibargoi, a pearsons correlation was conducted and an. r=0.216 in Makunga was obtained (significant positive impact of fertilizers on soil fertility), in the use of organic fertilizers was insignificant and not attached to land fertility and a Pearson correlation r=-0.087 was attained. This indicates that farming in Kibargoi is not dependent of organic fertilizers as opposed to farming in Makunga where fertilizers dictate land fertility. It was therefore observed that the use of organic fertilizers do have an impact on land fertility as compared to the use of inorganic fertilizers.