施肥对羊草草原土壤氮素转化的影响

施肥是常用的草地管理方式之一,对维持草地生产力和草地生态系统健康至关重要。本文以河北沽源羊草草原为对象,设置了5种施肥处理,研究了施肥对半干旱羊草草原土壤氮素形态及转化特征的影响。结果表明:在牧草整个生长季,氮磷配施处理土壤铵态氮和硝态氮含量低于相应的单施氮肥处理。氮肥施入改变了草地土壤氮矿化模式。在5-8月氮素添加各处理的土壤硝化作用强烈,明显高于其他处理,氮素添加处理土壤净氮矿化量在5-7月较大,其矿化量占整个生长季的57.58%~68.97%。土壤铵态氮含量与土壤硝态氮含量、净硝化量、净矿化量、土壤温度和土壤水分均存在显著正相关关系(P<0.05),土壤硝态氮含量与土壤温度有极显著正相关关系(r=0.491,P<0.01)。高氮添加处理增加了硝态氮淋溶损失和污染环境的风险。

Influence of fertilizer use on nitrogen transformation in soils of the Leymus chinensis steppe

Fertilizer application is a common grassland management technique and plays an important role in the maintenance of grassland productivity and the health of its ecosystems.In this study,five kinds of fertilizer treatment were applied to determine their effects on soil nitrogen forms and transformations in the Leymus chinensis grasslands of Guyuan,Hebei Province.The results showed that,during the whole forage-growing season,the soil nitrate and ammonium nitrogen contents in grassland fertilized with both nitrogen and phos-phorus were lower than that in grassland fertilized only with nitrogen.The application of nitrogen fertilizer changed the process of soil nitrogen mineralization.Grasslands with nitrogen fertilization showed stronger soil nitrification than the other treatments during the period from May to August,and higher net nitrogen minerali-zation during the period from May to July,which accounted for 57.58%-68.97% of total net nitrogen miner-alization over the whole forage-growing season.Positive correlations were observed between soil ammonium ni-trogen content,soil nitrate nitrogen content,net nitrogen nitrification,net nitrogen mineralization,soil tem-perature and soil moisture (r =0.491,P <0.01 ).High levels of nitrogen fertilizer application could increase the loss of nitrate nitrogen by leaching and thus the risk of environmental pollution.