Effectof Soil Factors on Net N-Mineralization and Decomposition Rate of Organic Nutrient Sources

Abstract

Rate of Mineralization for Organic Nutrient Sources (ONS) depends on temperature, soil moisture, soil chemical, physical, biological properties as well as the chemical composition of the ONS. Erythrinaabyssinica (EA), Erythrinabrucei(EB) and Enseteventricosum(EV) (ONS) were randomly collected from Sidama and Wolaita zones of southern Ethiopia. Surface soil samples (0-20 cm) depths were also collected from Cambisols of Wolaita and Luvisol of Sidama areas. Physicochemical properties of the composite soils were analyzed following standard analytical methods. For the greenhousemineralization potexperiment, 21 treatments for each week were designed for EA, EB and EVin Luvisol and Cambisols. The treatments were arranged in a completely randomized design (CRD) with three replications. The incubation was carried out in green house for five consecutive weeks., the average TN contents of EA, EB and EV were 4.05, 3.35 and 2.56%, respectively. Based on the TN contents, the amount of ONS equivalent to 100 kg urea + 100 kg DAP ha-1, was calculatedand incorporated into 200g of each soil type separately. The pots were watered to field capacity every day or two.In general, the study was conducted to investigate the effect of soil chemical and physical properties such as pH, particle size, organic carbon and total nitrogen content on rate of mineralization of these ONS. Each week determination of OC and TN contents were conducted. The results of mineralization revealed that the TN concentration was highest in the first week and became low and constant at the third to fifth week. The same trend was followed by OC constant declining in both soil types. There was a reduction of C/N ratio in both soil types. The ONS had medium to high TN content and they decompose easily. Thus, the study reveals these ONS can be used as alternative or supportive fast decomposing organic sources of fertilizers.