不同施氮量对两种茶园土壤硝化作用和pH值的影响

摘要

在土壤最大持水量60%和温度25℃的实验室培养条件下，对采自福建武夷山的两种类型土壤（黄壤和红壤）进行46 d的培养实验，研究了不同施氮量对茶园土壤硝化作用和pH值的影响。结果表明，两种茶园土壤中尿素的水解过程有明显差别，黄壤茶园土壤中尿素水解率高且较快（2~6 d），红壤茶园中水解过程达到了16 d；对照处理（N0）两种茶园硝化率分别为81.32%和73.48%，黄壤茶园土壤硝化作用显著高于红壤茶园（P<0.05）；无论施氮与否，两种茶园土壤 NO3--N 含量随时间的变化趋势呈“J”型，具有11~16 d 的延滞期，符合指数方程 N=N0ekt（P<0.01）；施氮后，两种茶园土壤的净消化量、净硝化速率和 k 值（P<0.05）均显著增加，且随施氮量的增加而增加，但土壤硝化率（P<0.05）显著降低；无论施氮与否，黄壤茶园土壤N2O排放速率在培养期间总体高于红壤茶园土壤，且前者累积排放量显著高于后者（P<0.05）；氮肥施用导致两种茶园土壤 pH 值下降，较对照分别下降了0.16~0.52和0.11~0.25，施氮量越大，pH 值下降越多。以上结果表明，研究中两种茶园土壤硝化作用较强，均存在硝化作用延滞期（11~16 d），有利于茶树对铵态氮的吸收利用；施氮导致土壤pH值降低，加速土壤酸化。%Two tea garden soils(yellow soil and red soil)derivedfromWuyishan Citywere incubated at25℃with a soil moisturecontent of 60% water holding capacity (WHC) for46 days.The dynamicsofnitrification andpHofsoil after urea applicationat different rateswere measured.The resultsshow thatureaishydrolyzedfast(2-6d)with a highnitrificationactivityin yellow soil.However,theureaishydrolyzedrelativelyslow(16d)inred soil.The nitrification rateintwo tea gardensoilsare81.32%and73.48%respectively, andthenitrificationactivityin yellow soilissignificantlyhigherthanthat inred soil(P<0.05).With or withoutnitrogenapplication,changing tendency of the contents ofNO3-Nintwotea garden soilsshow as‘J’typewith an obvious delaystep for 11-16days.The nitrification in theseteagardensoils followsthe exponential modelN=N0ekt(P<0.01).Compared with the control treatment,thenetamount of nitrified nitrogen, netnitrificationrate andkvalueincrease with the urea N application rates,however, thenitrification rates decreased withtheureaNapplication rates.With or withoutNitrogen Application, theN2Ofluxes fromyellowteagardensoilwere higher than those fromred tea garden soil(P<0.05). Compared with the control treatment, soil pH decreasedby0.16-0.52 and0.11-0.25pHunitswith the urea N application rates.These results indicatedthattwohighly acidicteagardensoilsshowedhighnitrification activity(delay stepwere 11-16 days),andbe conducive toabsorbNH4+-N.Urea application coulddecrease soil pH, and thenitrogen application rateisoneofthe main factors accelerating acidificationoftea gardensoil.