Plant biomass and seed production of the legumes Aeschynomeme histrix and Stylosanthes hamata and the potential of endozoochory by cattle and sheep in semi-arid native pastures

Abstract

Endozoochory is a substantial vector for seed dispersal and plays an important role in vegetation dynamics, mainly in colonisation processes through seed input to the vegetation and soil seed bank. We investigated the endozoochorous seed input by cattle and sheep on a pasture located in the western region of Burkina Faso. Through germination experiments, we assessed viable seed content of the dung of these grazing animals to estimate their suitability and efficiency for seed dispersal of fodder legumes. Cattle and sheep were daily fed seeds of Sthylosanthes hamata and Aeschynomene histrix, mixed with cotton seed cake. Faeces containing seeds of both legumes were collected 24 h after feeding. One part of faeces samples was spread in buckets of soil for direct germination in the greenhouse to evaluate germinating seed content. To improve pastures, a randomized completed design with 6 replications was conducted with both legumes and phosphorus fertilization (0 and 100 kg/ha of P2O5) and year as experimental factors. Recovery of A. histrix seeds was better than that of S. hamata with cattle (18 and 9%, respectively) compared to sheep. Seed recovered from faeces had higher germination with sheep than cattle. Thus, S. hamata seed recovered from faeces germinated well (12 and 45% with cattle and sheep, respectively, than fresh seeds used as control. However, A. histrix's seeds recovered from faeces germinated less than control (P < 0.001). The findings confirmed that ruminants could be used for targeted legume seed dispersal in natural pastures. A. histrix and S. hamata have high potential for plant biomass and seed production when phosphorus is applied. Seed ingestion by ruminants should be undertaken for improving natural pastures in semi-arid zones as lower cost practice.