Phosphorus availability as affected by the application of organic amendments in Ultisols

Abstract

The adequacy and availability of phosphorous (P) in the soil during the organic matter decomposition are important for plant growth, especially in the early stages since most organic matter slowly release plant nutrients. Therefore, this study was conducted to determine the availability of P during organic amendment s in Ultisols . The incubation experiment used a completely  Randomized Design (CRD) for 7 treatments which consisted of vermicompost, chicken, and cattle manure at the rate of 15 and 30 Mg ha -1 . Soil and organic amendment s were incorporated in to a 5 kg polybag and the mixture was incubated for 7 weeks. The soil was sampled at the 2, 3, 4, 5, 6, and 7 weeks, and analyzed for P availability and pH . Also, the Total Soil Organic Carbon (TSOC), Total Soil Nitrogen (TSN), exchangeable Al, and Cation Exchange Capacity (CEC) were analyzed from the soil sampled either at week 4 or 7. The result showed that P increased slowly in the first 3 weeks of incubation, followed by a drastic continuous increase in week 4. The experiment also confirmed that chicken manure released  the highest  and fastest amount of P to the soil as compared to vermicompost, and cattle manure. On average, the increment of P was 2.28, 1.71, and 1.97 mg kg -1 week -1 for chicken manure, vermicompost, and cattle manure respectively . Furthermore, the improvement of soil chemical properties was achieved using amendment as indicated by the increase in TSN, soil pH, and a decrease in exchangeable Al. The result was significant for P organic fertilization to en sure its availability for plant growth, leading t o improved productivity, especially in organic farming systems .