果园生草对氮素表层累积及径流损失的影响

为了正确认识生草覆盖对果园面源污染的防控作用和推进生态果园建设,采用模拟试验的方法,研究了果园生草覆盖、生草刈割和清耕3种管理措施对氮素表层累积及其流失特性的影响。结果表明:鼠茅草大量腐解时期(9月)生草覆盖处理土壤表层(0—1cm)矿质氮含量分别是生草刈割和清耕处理的2.6倍和4.5倍,与此同时,果园生草覆盖处理径流液中矿质氮浓度相比刈割和清耕处理分别提高42.6%和20.9%;与清耕相比,生草覆盖使降雨地表径流量显著降低88.3%~98.7%,渗漏量增加42.1%~97.6%。综合3次降雨,生草覆盖使矿质氮的径流损失比清耕降低90%,并且增加深层(25cm)渗漏89.6%。综上可见,虽然果园生草覆盖增加快速降解时期矿质态氮表层累积数量,但减少径流水损失效果显著,进而明显减少氮素径流损失,提高果园土壤的保水保肥能力,对解决坡地果园面源污染问题意义重大。

Effects of Cover Crop (Vulpia myuros) on the Accumulation and Runoff Loss of Nitrogen in Orchard

In order to correctly understand the control effect of grass cover on non-point source pollution and promote the construction of ecological orchard,a research was carried out to study the effects of cover crop (Vulpia myuros) on the accumulation and runoff loss of nitrogen.Three management modes,including grass cover on soil surface until withering (Cov),grass removed (Rem),and cleaning tillage as control (Cle).The results showed that the content of mineral nitrogen in the soil surface (0-1 cm) of the Cov treatment was 2.6 and 4.5 times as high as that of the Rem and Cle treatments when the withered grass degraded quickly (in September),respectively.At the same time,the Cov treatment increased the concentration of mineral nitrogen in the runoff by 42.6 ％ and 20.9％,respectively.The Cov treatment decreased the rain runoff by 88.3％-98.7％,and increased the rain leakage by 42.1％-97.6％ when compared with the Cle treatment.The results of three rainfall events showed that the runoff loss of mineral nitrogen was 90％ lower than that of the clean tillage,and deep layer (25 cm) leakage was increased by 89.6％.In conclusion,planting grass and covering it on the soil surface in orchard is an advantageous management to prevent non-point source pollution by reducing nitrogen loss through runoff.