Effect of short-term grazing exclusion on herbage species composition, dry matter productivity, and chemical composition of subtropical grasslands

Abstract

Grazing exclusion (GE) is a useful management technique for restoring degraded grasslands. The herbage mass productivity and chemical makeup in the grazing-excluded subtropical grassland environment has, however, received little attention. A subtropical riverine grassland was selected to determine the effect of GE on herbage mass productivity and chemical composition in Nepal. In three successive harvesting times from September to November 2020, the herbage was sampled along the six randomly selected transects of 100 m length and at two treatments (GA: Grazing-allowed and GE: Grazing-excluded plots) at three different times of harvest from a 1,000-ha grassland. A total of 108 herbage cut samples were collected from the individual 1 m × 1 m quadrats at the three harvests, respectively, from the GA and GE plots. Fences were used to maintain the GE plots to avoid grazing to prevent the vegetation altered by grazing. Day before herbage sampling, the functional groups, cover-abundance within the sampling quadrats were investigated. By cutting the fresh herbage 5 cm above the ground and subjecting it to oven drying for laboratory examination, the herbage mass productivity within each quadrat was measured. Using established laboratory procedures, the chemical analysis of herbage was evaluated for its proximate, fibre, and mineral contents. The results of the study demonstrated that GE significantly increased grass species than other-forbs, other-graminoids, and legumes, respectively, and increased dry matter productivity, which could be seen by an increase in leaf stem ratio, tiller productivity, increased coarseness (fibrous content), total ash, calcium (Ca), and phosphorus (P), but with a decreased nonstructural carbohydrate, and the concentrations of ether extract and crude protein. Research results also confirmed that GE increases herbages’ fibrousness and productivity, though the herbage quality, intake, and digestibility decline. It further demonstrates that grazing is a crucial biological component for maintaining pasture quality in subtropical grasslands and that managing grasslands through livestock grazing would make grasslands more stable and nutrient-enriched. The findings of this study can be useful in the long-term monitoring of grazing livestock in the subtropical grasslands when considering further investigations with the multiple factors in future.