Effects of animal dung deposition on grassland nutrients and botanical composition in mixed Lolium perenne and Trifolium repens pasture in Guizhou plateau

The mineral elements of soils and herbages, nutritional values, botanical composition and herbage defoliation in dung deposition and control plots in mixed Lolium perenne and Trifolium repens pasture in Guizhou plateau were quantitatively monitored and systemically analyzed in August 2011. The results indicated that the difference of mineral elements contents between soils and herbages was great and varied with different elements and excretion types. The dung deposition of grazing animals decreased or eliminated the positive correlation between soils and herbage in Na, K, and Mn contents, whereas the dung deposition promoted positive correlation between soils and herbage in Cu and Zn contents. The effects of grazing animal dung deposition on botanical composition of grassland in plant population and community levels varied with patch types and different decomposing stages. Grazing animals dung deposition could promote tiller and growth of L.perenne of D.glomerata, inhibit growth of T.repens, increase height and biomass of herbage and reproductive shoots of L.perenne, and decrease the nutritional values of herbages. The effect of cow dung on botanical composition was more obvious than that of sheep dung. The defoliation of grazing animals for L. perenne and D.glomerata in dung deposition plots was lower than that in controls. The rejected defoliation level of cow in dung deposition plots was higher than that of sheep. The results suggested that the mixed grazing with sheep and cattle could reduce the herbage waste in dung deposition sites and improve the utilization rate of grassland in grassland practical management.