By Rafiat K. Egberongbe and Rasheed O. Awodoyin
Sown fallow and green manure plants when integrated into the soil and decompose enhance the soil health by increasing organic matter content and possibly involved in the biological nitrogen fixation. Sesbania pachycarpa is a woody low-growing legume that can be used innovatively as sown fallow plant in conservation agriculture. The fallow potentials of S. pachycarpa were investigated in Ibadan in 2010 and 2011, by studying the germination biology, longevity of acid-scarified seeds in storage and effect of depths of sowing on seed germination and rate of biomass accumulation, in two trials and in a completely randomized design. Sesbania pachycarpa seeds were acid-scarified for durations ranging from 0-60 minutes and later up to 120 minutes. Acid-scarified seeds were tested for longevity of storage at ambient temperature for up to 12 weeks, and were sown at varying depths up to 16 cm. Seedlings of S. pachycarpa were raised in pots, with three pots randomly selected for the assessment of seedling performance at 2-week intervals for 14 weeks. The seed germination increased with duration of acid scarification, reaching the peak (about 96.67%) at 50 minutes, which was maintained up to 120 minutes. Acid-scarified Sesbania seeds stored for 4 weeks and the seeds lost viability at 12 weeks. The seeds did not germinate at depth more than 4 cm. The plants were fast growing, nodulating, not precocious and accumulated about 55.90 g/plant over 14 weeks. The tolerance of seeds of Sesbania pachycarpa for 120 minutes’ acid treatment may indicate its tolerance of acid soils. The plant will enhance soil biomass and fix atmospheric nitrogen into the soil, thus increasing carbon sequestration and reducing input of inorganic nitrogen fertilizer into the soil. Therefore, the plant may be ideal to establish sown fallow and green manure to restore fertility to degraded farmlands.