Abstract:

This experiment adopts the PVC tube cultured in situ. By planting the alfalfa（Medicago sativa‘Zhaodong’）and Siberian wildrye（Elymus sibiricus）between the fruit trees，studied on the characters of net mineralization rate of different grass species in different phenological period. And further analyzed the relationship between net nitrification and net ammonification and soil factors. The results indicated that nitrification dominated in the orchard soil mineralization，ammonification proportion was small. During the test period，in the 0–15 cm soil layer，the net nitrification rate of wild grass soil was 0.30 mg · kg-1 · d-1，the Siberian wildrye soil was 0.68 mg · kg-1 · d-1，the alfalfa soil was the minimum 0.28 mg · kg-1 · d-1. The conversion rate of nitrogen in the orchard soil was mainly occurred in the blossom period，during blossom period the soil net mineralization rate of alfalfa treatment was 3.4 times and 1.6 times than that in vegetative and fruiting period，respectively. And of siberian wildrye treatment were 1.8 times and 3.0 times than that in vegetative and fruiting period，respectively. The nitrification ability wasdetermined by C/N ratio in Siberian wildrye soil，the soil net mineralization rate of soil layer（15–30 cm）is weaker. The soil nitrogen transformation was significantly improved after planting Siberian wildrye，but the nitrification rate of alfalfa treatment reduced.

Key words: apple, grass growing in orchard, grass species, soil net nitrogen mineralization rate