The improving effects of Platycladus orientalis

Robinia pseudoacacia and the two mixed plantations on soil fertility on the Loess Plateau were investigated.In the Loess Plateau area

planting plantation had much help for the improvement of the nutritional element content

such as soil organic matter

total nitrogen

total phosphorus

available nitrogen and quick-acting potassium

and different plantations had different enhancement degrees.Except total potassium and quick-acting phosphorus

every target in nitrogen fixation plantation was higher than that in non-nitrogen fixation plantation.In general

the enhancement of soil fertility in nitrogen fixation plantation is more remarkable than that in non-nitrogen fixation plantation.