2017 Volume 63 Issue 2 Pages 74-80
To elucidate the effects of the silk tree, Albizia julibrissin Durazz., a pioneer legume tree, on chemical characteristics of soil and grasses, I compared the nutritional contents of surface soil and aboveground grass biomass beneath and beyond the canopies of isolated silk trees. Nitrate-N, MgO, and the phosphate absorption coefficient in the surface soil were significantly higher, and total N, CaO, and cation exchange capacity were marginally higher beneath the canopy than beyond it. Crude protein, Mg, net energy maintenance, organic cellular content + organic a fraction, and crude fat in grasses were significantly higher beneath the canopy. Fibrous components were significantly higher, and dry matter ratio and phosphate were marginally higher beyond the canopy. Chemical components which were higher in the soil beneath the canopy, such as N and Mg, were also higher in grasses beneath the canopy. However, phosphate in grasses was only marginally higher beyond the canopy in spite of the significantly higher phosphate absorption coefficient in the soil beneath the canopy. These results suggest that A. julibrissin contributes to fertilization of soil through N fixation by root nodule bacteria and the uptake of minerals by the deep roots from the subsoil and their return in litter to the surface soil, thus improving the feed characteristics of grasses growing beneath its canopy.
