Journal articleAgroforestry tree species producing high quality litter may enhance post-fallow soil nutrient availability and crop yields through mineralization of soil organic matter and green manure. A split-plot field experiment was used to evaluate maize yield and soil N and P status after fallowing indigenous and exotic tree species of contrasting litter quality. Responses were compared with recommended inorganic fertilizer use. The objective was to assess efficacy of 5-year tree fallows in improving soil productivity to screen species for increased crop yield under rotational woodlot culture, an agroforestry system mainly used for on-farm fuelwood production in semi-arid Tanzania. Post- fallow maize yield and soil nutrients differed significantly among tree fallows. Low C:N and L:N ratios enhanced nutrient release from slash. Acacia polyacantha (indigenous) and Gliricidia sepium fallows doubled maize yield compared to the natural fallow probably due to high soil N and P levels resulting from net release by high quality foliage. First season maize yield was similar to that from combined N and P fertilizers indicating high capacity of the fallows to improve crop yields and reduce fertilizer inputs usually unaffordable to small-scale farmers. Comparatively low maize yield and soil N and P levels after exotic Acacia crassicarpa and Acacia mangium fallows were attributed to net N immobilization by poor quality litter during growing seasons. This study suggests that rotational woodlot systems utilizing tree species with high litter quality can improve both post-fallow maize yield and soil fertility as well as produce sufficient fuelwood. In this aspect, A. polyacantha would be the most appropriate species.