不同管理方式下橡胶林土壤氮动态特征

对西双版纳割胶、未割胶条件下橡胶林种植带土壤及其保护带土壤氮素动态变化特征进行了研究,并比较了不同保护带种植方式(距瓣豆绿肥覆盖与野生杂草覆盖)对土壤氮素动态的影响。结果表明,橡胶林种植带土壤全氮、碱解氮和硝态氮含量低于保护带。橡胶林土壤全氮、碱解氮、铵态氮、硝态氮均呈现明显的动态变化,种植距瓣豆绿肥覆盖与野生杂草生长覆盖的橡胶林土壤氮变化趋势一致。土壤全氮随时间逐渐下降,碱解氮含量先升后降,铵态氮和硝态氮含量变化幅度较大。橡胶林土壤全氮和碱解氮含量呈现表层(0～20cm)>中层(20～40cm)>底层(40～60cm)的趋势,且未割胶处理全氮和碱解氮含量>割胶处理,而保护带为距瓣豆绿肥覆盖的割胶橡胶林>杂草生长覆盖的橡胶林。距瓣豆绿肥覆盖的保护带土壤硝态氮含量高于杂草生长覆盖。碱解氮与铵态氮含量呈显著的负相关、与硝态氮呈显著正相关。割胶橡胶林土壤氮养分含量最低。橡胶林土壤种植豆科距瓣豆绿肥能够改善土壤氮素肥力。

Variations of soil nitrogen in rubber plantations under different managements

During July 2009-December 2009,a study was conducted on the dynamic variations of soil nitrogen forms in the rubber plantations under different managements(rubber tapping and no rubber tapping) and in the protection areas of the plantations,which covered with Centrosema pubescens Benth green manure or weeds,in Xishuangbanna.In the rubber plantations,the soil total nitrogen(TN),alkali-hydrolysable N,and nitrate nitrogen(NO3--N) contents were lower than those in the protection areas.The soil TN,alkali-hydrolysable N,ammonium nitrogen(NH4+-N),and NO3--N in the rubber plantations had obvious dynamic variations,while the soil nitrogen forms in the protection areas whether covered with green manure or weeds had the same variation trends.The soil TN decreased with time,soil alkali-hydrolysable N decreased after an initial increase,while soil NH4+-N and NO3--N varied significantly with time.In rubber plantations,the soil TN and alkali-hydrolysable N contents presented a trend of decreasing with soil depth,i.e.,surface layer(0-20 cm) > medium layer(20-40 cm) > bottom layer(40-60 cm),and were higher under no rubber tapping than under rubber tapping.In the protection areas,the soil TN,alkali-hydrolysable N,and nitrate N contents were higher under green manure covering than under weed covering.Soil alkali-hydrolysable N had a significant negative correlation with soil NH4+-N,but a significant positive correlation with soil NO3--N.Rubber tapping decreased the soil nitrogen content,while planting C.pubescens green manure could improve the soil nitrogen fertility.