稀土元素对土壤中尿素水解及其水解产物行为的影响

Influences of rare earths on the hydrolysis of urea and its hydrolyzed product in soil

以潮土为供试土壤进行土培试验 ,研究了农用稀土对同时施加的尿素在土壤中形态转化过程影响 .当稀土施用量增至 10mg·kg-1烘干土以上时 ,土壤中尿素水解后所形成的铵态氮含量显著增加 .在不同培养时间内 ,土壤中源自尿素的硝态氮和亚硝态氮含量随稀土施用量增加呈降低趋势 ;当施用量增至 5 0mg·kg-1烘干土时 ,与对照相比的降低程度达显著水平 .施加稀土元素后 ,土壤有效氮含量明显增加 ,主要由于土壤铵态氮增加所致 .结合土壤 pH变化 ,表明稀土施用量高于 10mg·kg-1烘干土时 ,可明显延缓尿素在潮土中水解进程并抑制水解产物铵态氮的氧化 ,利于土壤对尿素氮固持 .

By incubation experiment with luvisol,the influences of rare earths on the trans formations of simultaneously applied urea in the soil were studied.When the dosa ge of applied rare earths was more than 10mg·kg -1 oven dried soil,the co ncentration of urea derived exchangeable NH\++\-4 N in the soil significantly increased and the increase appeared the dose dependent relationship.During diff erent periods of soil incubation,the concentration of soil urea derived (NO\+-\-3+NO\+-\-2) N decreased with increasing dosage of applied rare earths.In addi tion,at the dosages more than 50mg·kg -1 oven dried soil,a significant r ed uction of this N form in the soil appeared.Applying rare earths could cause an i ncrease in the concentration of soil available nitrogen,mainly due to a substant ial NH\++\-4 N pool available in the soil. Considering the variation of pH valu es in the soil,it is concluded that the application of rare earths at a dosage h igher than 10mg·kg -1 oven dried soil,can retard the hydrolysis of simult aneously applied urea in the soil and inhibit the oxidation of its hydrolyzed NH + 4 N.This indicates that a joint application of urea and rare earths can be beneficial to the retention of applied urea in soil.