温带果园护土生草鼠茅草的腐解和养分释放

鼠茅草是适合于温带果园的越年生护土生草,有助于防止水土流失,然而果农担心鼠茅草可能与果树争肥,不利于果树生产。本研究在青岛地区温湿气候条件下测试鼠茅草的腐烂分解及养分释放特征。2012年6月底采集枯死鼠茅草,将其埋在10 cm深的土壤中,使土壤含水量分别稳定在田间持水量的65%,75%和85%,7－10月份每隔10 d抽检其腐解程度和碳、氮、磷、钾元素的释放速率。结果表明,鼠茅草的腐烂分解是比较快的,自初夏枯死后经80 d大约分解30%;伴随鼠茅草的腐烂,碳、氮、磷和钾会释放出来,快速释放期集中在前20－40 d,钾的释放速度最快,其次为磷,碳、氮的释放速度较慢;土壤含水量影响鼠茅草的腐解过程,当土壤含水量由65%田间持水量提高至85%时,鼠茅草的腐解和养分释放加快。据此可断,7-10月是鼠茅草分解的主要时期,可为果树生长提供营养而非争夺养分。在青岛等温湿地区,以鼠茅草作为果园护土生草是可行的,它们同苹果等落叶果树在养分利用上可形成互补关系,有益于果园的养分循环和持续生产。

Decay and nutrient release in Vulpia myuros grasses,a species suitable for soil con-servation in temperate zone orchards

The grass species Vulpia myuros has a September-to-June growth period and can enhance orchard soils and prevent water loss and soil erosion. However, orchard managers are often concerned by the species’ presence as a competitor for nutrients with fruit trees. This paper reports an investigation of the decomposition and nutrient release rates of V. myuros in the Qingdao area of northern China, which has a humid climate. Dead V. myuros was collected in late June 2012 and buried at the depth of 10 cm in soils with three moisture content levels (65%, 75% and 85%). Decay rates and the release rates of carbon, nitrogen, phosphorus and potassium were measured every ten days between July and October. Results showed that V. myuros has a very fast decay rate, with approximately 30% decomposed within 80 days. This decay releases carbon, nitrogen, phosphorous and potassium, principally during the first 20-40 days. Potassium had the fastest release rate, followed by phosphorous, while nitrogen and carbon were the slowest. Soil moisture had a significant effect on decomposition. The decay rate is accelerated when moisture levels are raised from 65% to 85%. The study concludes that V. myuros can supply nutrients to fruit trees and does not compete with them, as previously thought. Thus V. myuros can be used in the temperate hilly regions in northern China in order to enhance nutrient cycling in orchard ecosystems.