Unraveling the Effects of Pruning Frequency on Biomass Productivity, Nonstructural Carbohydrates and Nitrogen Fixation Rates of Sesbania sesban

Tree pruning is a management tool in agroforestry systems for reducing shade, enhancing nutrient cycling or providing fodder. However, little information is available on the effect of pruning management on plant growth, nonstructural carbohydrate (NSC) levels in the roots and N-2 fixation of Sesbania sesban. A glasshouse experiment was conducted to assess the effect of pruning frequency on biomass production, NSC levels and N-2 fixation of Sesbania sesban. Pruning treatments consisted of a control (PF0), one pruning at 3 months after transplanting (MAT) (PF1), two successive prunings at 3 and 6 MAT (PF2), and three successive prunings at 3, 6 and 9 MAT (PF3), with each pruning removing shoot biomass above 50% of the initial height. The experiment was laid out in a completely randomized design (CRD) with four replications. Results showed that increasing pruning frequency resulted in decreased nodulation and nonstructural carbohydrate levels in the roots. Above and below ground biomass, root length, percentage N derived from the atmosphere and amount of N-2 fixed were decreased in a similar manner whether plants were successively pruned twice or thrice. It can be concluded that two or three successive prunings in nine months significantly reduce nonstructural carbohydrates, DM productivity and N-2 fixation of S. sesban, and might result in supply of insufficient biomass required for improving soil N fertility and livestock production.