猪场废水与氮肥水平对土壤氮矿化特性影响研究

The Impact of Nitrogen fertilizer and Irrigation with Piggery Wastewater on Nitrogen Mineralization

土壤氮素利用效率与土壤供氮能力密切相关,而猪场废水灌溉和外源氮肥的施入都会影响到土壤的供氮能力,研究猪场废水灌溉条件下土壤氮素的释放规律可为合理施肥及提高氮素利用效率提供理论依据。试验设5个处理:猪场废水高氮处理(PWH,目标含氮量(以纯氮计)为105 mg/kg),猪场废水低氮处理(PWL,目标含氮量(以纯氮计)为66 mg/kg),清水高氮处理(CKH,目标含氮量(以纯氮计)为105 mg/kg),清水低氮处理(CKL,目标含氮量(以纯氮计)为66 mg/kg),CK为清水不施氮处理,每个处理重复3次。通过室内常温培养试验,分别在培养的第7、14、21、28、35、42天测定土壤铵态氮、硝态氮及全氮量,研究了等氮量投入猪场废水与清水(自来水)相比氮素矿化及其影响因素差异。培养期间,各处理土壤全氮和铵态氮呈逐渐下降的趋势。硝态氮随培养期延长呈逐渐上升的趋势。猪场废水高氮PWH处理铵态氮和硝态氮量在培养末期均为最高,分别达40.12 mg/kg和152.32 mg/kg,清水高氮CKH处理在培养末期全氮量最高,为0.43 g/kg。培养前期土壤氮素矿化较快,中后期变化较慢,土壤供氮平稳,同一时段不同处理土壤累积矿化氮量存在显著差异(P<0.05),表明不同外源氮肥输入对土壤氮素的矿化能力影响显著。PWH、PWL、CKH、CKL处理最大累积矿化氮量分别为59.69、31.07、24.26、23.49 mg/kg。土壤氮素的矿化速率随着培养时间的增加而逐渐降低,且等氮投入的猪场废水培养处理土壤氮素矿化速率显著高于清水处理。综上所述,猪场废水高氮PWH处理的供氮能力最强,该处理有利于土壤微生物数量及脲酶、蛋白酶活性的增加。

Nitrogen input into soil influences nitrogen cycling and is closely related to nitrogen use efficiency. A laboratory experiment was conducted in this paper to investigate the change in ammonium nitrogen （NH＋4-N）, ni- trate nitrogen （NO3-N） and total nitrogen （TN） in soil samples （0, 7, 14, 21, 28, 35 and 42 days） irrigated by pig- gery wastewater and clean water （running water）under conditions that the nitrogen input in all treatments were the same and that the nitrogen input in each treatment was set at a high level and a low level. The results showed that TN and NH＋4-N gradually decreased over time under different treatments, while NO3-N increased. At the end of the incubation, the content of TN, NH＋4-N and NO3-N in high N treatment was higher than those at low N treat- ment. The maximum TN content was in CKH treatment （clean water with high nitrogen）, while the maximum contents of NH＋4-N and NO3-N were both in the PWH treatment （irrigating with piggery wastewater plus high nitrogen application）. There was a significant difference in cumulative mineralized nitrogen among different treatments （P〈0.05）. The results also demonstrated that nitrogen input impacted cumulative mineralized nitrogen in two ways, and the cumulative mineralized nitrogen was the highest in the PWH treatment with a value of 59.69 mg/kg. The nitrogen mineralization rate decreased with the incubation time, and the nitrogen mineralization rate under piggery wastewater treatments were significantly higher than that under clean water treatments despite their different nitrogen managements. It is not difficult to conclude that the PWH treatment has the greatest nitrogen supplying capacity, due to the high microbial biomass and enzyme activity of nitrogen mineralization.