Effect of 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. Erythrina abyssinica (EA), Erythrina brucei (EB) and Ensete ventricosum (EV) (ONS) were collected from Sidama and Wolaita, southern Ethiopia. Soil samples (0-20 cm) depths were collected from Cambisols and Luvisols areas. Physicochemical properties of the two soils were analyzed following standard analytical methods. For the greenhouse mineralization pot experiment, 21 treatments for each week were designed for EA, EB and EV in Luvisols 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. The pots were watered to field capacity every day or two. 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 that these ONS can be used as alternative or supportive fast decomposing organic sources of fertilizers. Key words: C/N ratio, incubation, total nitrogen, organic carbon, organic nutrient sources. INTRODUCTION