Decomposition and Nutrient Release from Various Tree Litters in a Sandy Soil of a Semi-arid Tropics

Abstract

A field experiment was carried for 16 weeks in western Omdurman, in a soil vulnerable to wind erosion, to monitor decomposition and nutrient release from residues of Mesquite (Prosopis spp), Mahogany (Khaya senegalensis) and Neem (Azadirachta indica). Fresh leaf litters were placed inside litterbags and buried into the top 25cm depth of an Aridisol. Samples were drawn at intervals of 1, 2, 4, 6, 8, 10, 12, 14, and 16 weeks and were analyzed to determine remaining dry matter weight (DMW), N, P, K, Ca, Mg, and total C. Results showed that, Neem decomposed significantly faster than both Mesquite and Mahogany with a rate constant (k) of 0.25 week-1 (Neem) and 0.12 week1 for each Mesquite and Mahogany. However, content of lignin and cellulose were best indicators, especially for Neem residues. All litters examined in this work were good sources of K for sandy soils which are low in this element, as 80% of the initial content of K was released in the first 2 weeks of incubation. The pattern of nutrient release gave reliable guidance for synchronizing these nutrients with demand of subsequent crops. This study suggests that, Mesquite and Neem constitute comparatively readily available sources of N, and they could be suitable for short-term nutrient correction. However, incorporation of residues from Mahogany caused noticeable N immobilization. With the slow decay of the mahogany litter, it is worthy to be used for organic matter build up in arid soils.