尿素与有机肥配施对棕红壤氮素转化的影响

Effect of Interaction Between Manure and Urea on Transformation of Nitrogen in Brown Red Soil

为了解析尿素配施有机肥对土壤氮库活动的影响,通过室内恒温培养试验研究尿素(225kg N·hm^(-2))分别与低量(30 t·hm^(-2))、中量(60 t·hm^(-2))及高量(120、150 t·hm^(-2))有机肥配施条件下棕红壤有机氮库、无机氮库的动态变化。结果表明,配施有机肥土壤的有机氮含量较单施尿素增加16.3%~85.6%。中、高量配施显著提高土壤氮素矿化速率(p<0.05),加剧无机氮转化强度,与单施尿素相比,无机氮最大矿化量增加52.9~246.0 mg·kg^(-1),有效矿化持续时间延长5 d,转化量增大2.3倍~8.7倍;配施有机肥提高土壤氨化强度,加快铵态氮(NH_4^+-N)转化速率。与单施尿素相比,配施有机肥处理NH_4^+-N含量峰值增加2.6~42.6 mg·kg^(-1),平均氨化速率提高7.8 mg·kg^(-1)·d^(-1),转化速率增加1.4倍~8.8倍。一定量配施有机肥(30~120 t·hm^(-2))对土壤的硝化过程无显著影响,但过高量配施有机肥(150 t·hm^(-2)),强化土壤硝化作用,硝化速率较单施尿素提高4.2倍,引起土壤硝态氮(NO-3-N)大量累积。氮素表观平衡结果表明,中、高量配施有机肥显著增加培养体系氮素表观损失,60、90和120 t·hm^(-2)处理氮素损失量分别较单施尿素增加2.2倍、2.8倍和2.3倍,占总输入氮的27.5%~34.5%,其中,NH_4^+-N转化损失是体系氮表观损失的主要途径。本研究结果为棕红壤合理培肥提供了理论依据。

In this study, the effect of different amount of manure （30, 60, 90, 120, 150 t·hm^-2） with urea （225 kg N·hm^-2） on soil organic nitrogen pool, mineral nitrogen content and nitrogen balance was analyzed in brown red soil using laboratory incubation method. The results showed that the soil organic nitrogen content increased by 16.29%~85.64% with mixing manure in comparison with the single application of urea. In the medium and high manure application treatments, soil nitrogen mineralization potential （p〈0.05） and transformation intensity of inorganic nitrogen increased significantly. Besides, the amount of soil mineral nitrogen increased by 52.9~246.0 mg·kg^-1; soil nitrogen mineralization peak was delayed by 5d and the transformation amount of mineral nitrogen was 2.3~ 8.7 times higher than that in the urea-only treatments. Moreover, mixing with organic fertilizer could also promote the soil ammonification intensity and the conversion rate of NH4^＋-N. In mixing manure treatments, the peak values of soil N H4^＋-N content increased by 2.6~42.6 mg·kg-1; the average ammonification rate increased by 7.8 mg·kg^-1·d^-1, and the conversion rate was 1.4~8.8 times higher than that of the urea-only treatments. Although the manure application at the range of 30 to 120 t·hm^-2 could not make significant impact on soil nitrification, the nitrification rate of the high manure application （150 t·hm^-2） increased by 4.2 times higher than the urea-only treatment, which also resulted in a lot soil nitrate （NO3^--N） accumulation. The apparent nitrogen loss was increased significantly in the medium and high manure application treatments. In combined application of urea and manure （60, 90 and 120 t·hm^-2） treatments, the apparent nitrogen loss was 2.2, 2.8 and 3.3 times higher than that of the urea only treatment, which accounted for 27.5%~34.5% of the total input nitrogen content. Additionally, the conversion loss of N H4^＋--N was the main approach in the apparent nitrogen loss system. This study provided a theoretical basis for effective fertility manner of brown loam.