苜蓿和老芒麦生草对苹果园土壤氮素矿化的影响

采用PVC管原位培养法，研究了苹果园行间生草，肇东苜蓿（Medicago sativa‘Zhaodong’）和老芒麦（Elymus sibiricus）对土壤氮素净矿化作用及物候期间的变化特征，并进一步分析净硝化作用和净氨化作用特征及其与土壤因素之间的关系。结果表明：土壤氮素矿化作用主要以硝化作用为主，氨化作用比重很小。测试期间，0 ~ 15 cm土层中，自然生草土壤的氮素净硝化速率为0.30 mg · kg-1 · d-1，老芒麦土壤为0.68 mg · kg-1 · d-1，苜蓿土壤最低，为0.28 mg · kg-1 · d-1。不同草种的氮素矿化主要在开花期完成，苜蓿土壤中开花期的土壤氮素净矿化速率分别为营养期和果实期的3.4倍和1.6倍，老芒麦则分别为1.8倍和3.0倍。老芒麦土壤中C/N比影响着氮素硝化能力，15 ~ 30 cm土层土壤的氮素矿化相对较弱。种植老芒麦后土壤氮素矿化能力明显提高，而苜蓿土壤中硝化速率降低。

The Effects of Different Grass Species on Soil Nitrogen Mineralization in Apple Orchard

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.