麦季施用不同尿素的氮排水和渗漏损失

Nitrogen loss via runoff and leaching from soil as a function of types of urea applied in wheat season.

在太湖地区乌栅土的稻麦轮作条件下,利用大型原状土柱渗漏液采集器(monolithlysimeter),比较不同尿素品种和施肥量(普通尿素150、300kg·hm-2和包膜尿素100、150kg·hm-2)处理对麦季土壤氮随径流和渗漏损失的影响。结果表明:施用的包膜尿素当季氮不易随排水流失,但可能增加下季氮流失的风险。两麦季排水溶解氮均以NO-3 N为主,达76.7%以上,NH+4 N比例很小;麦季排水氮输出量年际差异明显,降雨产生排水与施肥时间间隔的不同是造成排水氮输出量差异的关键因素;施肥后20d内发生排水易产生较多的氮排放。渗漏液硝态氮浓度(最高为8.12mg·L-1)均未超过饮用水NO-3 N含量标准,但均已超过水体富营养化标准;对照处理麦季渗漏液量显著高于施肥处理;在150kg·hm-2的施N量水平下,普通尿素或包膜尿素均未显著增加氮的渗漏,但过量施用普通尿素则加大氮渗漏的风险。

An experiment using large-sized undisturbed monolith lysimeters was carried out to study nitrogen loss via drainage and leaching from Wushan soil in the Taihu Region under a rice-wheat rotation system with different types of urea fertilizers applied in wheat seasons in the years of 2001 to 2003.The results show that dissolved N(DN)in the drainage flow can be partitioned as NO^-_3-N representing more than 76.7% of the DN,and as NH^+_4-N accounting for less than (23.3%).N loss via drainage flow in the wheat seasons varied significantly from year to year.Interval between rainfall and fertilization was the key factor dominating nitrogen drainage losses.The NO^-_3-N concentrations in leaching from all the treatments(The highest NO^-_3-N concentration was 8.12 mg·L^(-1)) were lower than the criteria of NO^-_3-N concentration for drinking water,but were higher than 0.02 mg·L^(-1)(the threshold concentration of DN for inland water eutrophication).The amount of percolation in CK was higher than the other treatments.When N 150 kg·hm^(-2) was applied,the N loss via percolation was not significantly increased by N application no matter whether the fertilizer was common urea or coated (urea).But continuous N application with rates higher than the N demand by wheat will certainly increase the risk of N loss via percolation.