Mineralization Rates of Soil Forms of Nitrogen, Phosphorus, and Potassium as Affected by Organomineral Fertilizer in Sandy Loam

Farmers tend to use organomineral fertilizers as a result of inadequacies embedded in the sole use of organic and mineral fertilizers. A laboratory incubation study to determine the rate of the forms of N, P, and K released by organomineral fertilizer was conducted at Adeyemi College of Education, Ondo, southwest Nigeria, in 2013. Organomineral fertilizer (OMF) at the rates of 0, 0.125, 0.25, 0.5, and 1.0？g/100？g soil to represent 0, 2.5, 5, 10, and 20？t ha？1 OMF, respectively, was incubated for ninety days. The treatments were replicated three times and arranged in a completely randomized design. The determined forms of N were total N, NH4–N, and NO3–N; the forms of P were total P, solution P, and available P while the forms of K were total K, solution K, and exchangeable K. Organomineral fertilizer significantly increased N, NH4–N, NO3–N, total P, solution P, exchangeable P, solution K, and exchangeable K at all rates with different values. The rate of ammonification of N was higher than the rate of nitrification of NH4 + N to NO3 + N especially at 10 and 20？t ha？1 OMF. Application of 5 and 10 t ha？1 OMF could be used to increase soil forms of N, P, and K. 1. Introduction The aim of a farmer is to have bumper harvest and to get it depending on soil productivity. This leads to the philosophy that emphasises the need to apply fertilizers when economic yield is likely to occur. The essential nutrient elements are N, P, K, Ca, Mg, and S. Among these nutrient elements, N ranks first in plant requirement and phosphorus (P) ranks second followed by potassium (K). N, P, and K are referred to essential nutrients because nearly all plants use them for growth and development. Their deficiencies cannot be corrected by another element and are needed by the plants before they can complete their vegetative and reproductive cycles. Many plants require them throughout their life cycles. The nutrients are expected to be present in the soil in proper form and in proper balance. Their misuse can pose threats to water quality and can also cause nutrient antagonism which may result in low crop yield. Farmers are in the habit of improving soil fertility through the addition of mineral fertilizers and organic manures, but the sole use of either fertilizer has not solved the problem of nutrient deficiencies. This necessitates research into the use of combined organic and inorganic fertilizers [1]. Organomineral fertilizers are produced by fortifying agro wastes with mineral fertilizer. The interest in organomineral fertilizers arose from the demerits of organic and mineral