不同施氮水平对再生水灌溉土壤释氮节律的影响

土壤供氮能力是影响土壤氮素利用效率的一个重要指标,再生水灌溉和施氮水平均影响着土壤供氮能力,研究不同施氮水平对长期再生水灌溉土壤氮素的转化特征可为合理施肥及农产品增产增效提供理论依据.本研究选择河南新乡洪门试验站温室大棚内长期再生水灌溉和清水灌溉土壤,试验共设8个处理:A(N200)(施氮量200 mg·kg-1)、A(N160)(施氮量160 mg·kg-1)、A(N140)(施氮量140 mg·kg-1)、A(N100)(施氮量100 mg·kg-1)、A(N0)(施氮量0 mg·kg-1)、E(清水灌溉常规施氮)、CK(清水灌溉不施氮)、Re CK(再生水灌溉不施氮),采用实验室内常温培养法,分别在培养的7、14、21、28、35、42 d测定土壤铵态氮、硝态氮及全氮含量,并分析了土壤氮素矿化量和氮素矿化速率的变化,通过Freundlich线性等温吸附模型及一级动力学方程拟合了土壤吸附参数Kd和氮素矿化势N0.结果发现,培养前期土壤氮素矿化较快,释放的氮量较高,中后期变化较慢,土壤供氮平稳,同一时段不同处理间土壤累积矿化氮量存在显著差异(p0.05),表明不同外源氮肥输入对土壤氮素的矿化能力影响显著,A(N160)处理的供氮能力最强;同时,在培养前期Re CK处理的土壤氮素矿化累积量显著高于CK处理,表明再生水灌溉较清水灌溉促进了土壤氮素的矿化,显著提高了土壤氮素活性;土壤氮素的矿化速率随着培养时间的增加而逐渐降低,但降幅依次减小并趋于平稳,且不同施氮处理再生水灌溉土壤氮素矿化速率显著高于清水灌溉;不同土壤肥力水平(B0)、外源施氮A(N160)调控,土壤氮素矿化潜势可表达为N0=B0+117.5072t-0.1062.因此,外源氮肥输入显著影响了土壤氮素释放节律,再生水灌溉辅以适宜的施氮量可促进土壤氮素矿化,提高土壤氮素活性.

Influence of nitrogen rate on nitrogen release pattern in soil irrigated with reclaimed wastewater

Both reclaimed wastewater irrigation and different nitrogen rate influence the soil nitrogen supplying capacity, which is closely related to nitrogen efficiency of soil. Soil nitrogen transformation process was studied under different nitrogen rate with long-term reclaimed wastewater irrigation, which would be helpful to provide theoretical basis for reasonable wastewater fertilization guidelines and to obtain high yield of agriculture product. This experiment was conducted at Chinese academy of agricultural sciences key laboratory of high-efficient and safe utilization of agricultural water resources. The experimental soil consisted of conventional fertilization soil long-term irrigated with reclaimed wastewater (A) and tap water (E) at Hongmen test station in Xinxiang, Henan. The test was carried out in 8 parallel treatments, including A(N200)(nitrogen amount 200 mg·kg^-1), A(N160) (nitrogen amount 160 mg·kg^-1), A(N140) (nitrogen amount 140 mg·kg^-1), A(N100) (nitrogen amount 100 mg·kg^-1), A(N0)(nitrogen amount 0 mg·kg^-1), E(conventional nitrogen fertilization with tap water irrigation), CK(no fertilization with tap water irrigation), ReCK(no fertilization with reclaimed wastewater irrigation). Using the method of indoor thermostatic incubation, soil ammonium nitrogen, nitrate nitrogen and total nitrogen of the samples were measured in 7, 14, 21, 28, 35 and 42 days, respectively. The changes of soil nitrogen cumulative mineralization and nitrogen mineralization rate were analyzed. Freundlich linear isothermal adsorption model and first-order kinetic model were applied to fit soil adsorption parameter and nitrogen mineralization potential. Soil nitrogen mineralization was faster at the early stage of incubation, and the release of nitrogen was higher than those in the middle and later periods. The significant difference was found among soil N cumulative mineralization of different treatments in the same period. The result showed that exogenous nitrogen input had significant effect on soil nitrogen mineralization ability, and the nitrogen supplying capacity of A(N160) (nitrogen amount 160 mg·kg^-1) treatment is the strongest. In addition, soil N cumulative mineralization of ReCK treatment was significantly higher than that in CK treatment at the early stage of incubation, indicating that compared with tap water irrigation, reclaimed water irrigation promoted the soil nitrogen mineralization and significantly increased the soil fertility. Soil nitrogen mineralization rate involved certain regularity. The mineralization rate gradually decreased to a stable state. The linear fitting of soil NH₄⁺ adsorption of different treatment was not very satisfactory, and a large amount of solute was kept in the soil solution. A coupled model (N₀=B₀+117.5072t^-0.1062) was developed based on A(N160) treatment to describe the mineralization potential of different soil background values. Exogenous nitrogen input significantly affected the soil nitrogen release rhythm. This indicated that appropriate nitrogen amount with reclaimed wastewater irrigation could promote soil nitrogen mineralization and hence improve soil nitrogen supplying capacity.