几种硝化抑制剂和包硫尿素(SCU)对土壤N素形态和小麦产量的影响

采用土壤盆栽法,研究了双氰胺(DCD)、硫脲(THU)和硫脲甲醛树脂(TFR)以及包硫尿素(SCU)对土壤氮素形态和小麦产量的影响。试验共设不施氮(CK)、单施尿素、包硫尿素(SCU)、以及尿素分别与DCD、THA、TUF的3个浓度梯度(分别按尿素用量的0.5%、1%、2%)配合施用共12个处理。结果表明:随添加浓度的增加,硝化抑制作用逐渐增强,高剂量硝化抑制剂显著降低土壤NO-3-N含量,在2%添加浓度下,DCD、THU、TFR的土壤NO-3-N浓度分别比单施尿素降低29%、22%和14%,对土壤表观硝化率的抑制强度也是2%DCD2%THU2%TFR;SCU处理与2%DCD作用强度接近,且在施用早期就体现抑制效果,并在追肥后第74 d土壤表观硝化率显著低于使用硝化抑制剂的处理(P0.05);硝化抑制剂和SCU都可以使土壤NH+4-N含量稳定在较高的水平,抑制剂用量越多,土壤NH+4-N含量越高;与单施尿素相比,尿素+DCD模式,均可提高小麦产量,且在0.5%、1%、2%添加浓度,都达到显著水平(P0.05);THU在1.0%和2.0%添加浓度,小麦产量显著高于单施尿素,但增产效果次于DCD。总体上,包硫尿素(SCU)比硝化抑制剂在控释氮素方面效果更持久,而3种硝化抑制剂中,在控制土壤NH+4-N转化、土壤硝化抑制方面,DCD和THU优于TFR;作为外源添加物的抑制剂长期应用可能对土壤环境造成潜在的危害,不同硝化抑制在土壤中的形态归趋和长期作用还有待进一步研究。

Effects of Nitrification Inhibitors and Sulphur Coated Urea(SCU)on Different Nitrogen Sources and Wheat Yield

Nitrogen is essential for plant growth and health, and it is also a limiting factor for the growth in most agricultural systems. Intensive N fertilizer application has become the traditional habit for agricultural producers in China because of its importance to plant productivity and agricultural land profitability. But some problems have appeared with the increase of the amount of nitrogen fertilizer applied, urea used in crops is easy to lose from volatilization or leaching. Therefore, current crop management practices lead to a highly nitrifying soil environments. Nitrogen emission is the main source of soil acidity and environmental pollution. Several methods for the use of slow controlled release urea have been reported to be used to control the pollution and to enhance nitrogen use efficiency. There is a growing interest in the formulations ofcoated chemical fertilizers with both urease inhibitor and nitrification inhibitor. Urease inhibitor and nitrification inhibitor may improve urea N-use efficiency and minimize N losses by gaseous emissions of ammonia(NH3)to the atmosphere and nitrate(NO-3)leaching into the surface and ground water. Dicyandiamide(DCD)is a nitrification inhibitor that has been studied for many years, it can effectively inhibit nitrification and N2O emission in many agricultural ecosystems. However, limited information is available on the use of the combination of nitrification inhibitor and urease inhibitor applied with urea fertilizer, especially for thiourea(THU)and thiourea formaldehyde resin(TFR)applications. Therefore the purpose of this study is to investigate the effect of urea with different inhibitors to improve the efficiency of nitrogen utilization. A field pot experiment was conducted to explore how to increase the concentration of DCD/THU/TFR/sulfur-coated urea(SCU)to affect the transformation of soil nitrogen and wheat yield. The experiment was designed for twelve treatments which included no nitrogen(CK), only urea, SCU and the combination use of DCD, TFR, THU three concentration gradients(0.5%, 1%, 2%of urea dosage)with urea respectively. The results showed:the inhibition of nitrification was gradually enhanced with the increase of its concentration, high dose nitrification inhibitor decreased the content of soil NO-3-N significantly, the soil NO-3-N concentration with DCD, THU, TFR at the 2%dosage were lower than that with only urea by 29%, 22%and 14%respectively, and the inhibition effect of soil apparent nitrification rate was also 2%DCD>2%THU>2%TFR. The SCU treatment effect was close to the 2%DCD function strength, and it reflected the inhibition effect in the early stage of application, the soil apparent nitrification rate in the seventy-fourth days after fertilization was significantly lower than that of using the nitrification inhibition(P<0.05). Both of nitrification inhibitor and SCU could make the soil NH+4-N concentration at a higher level, and the more inhibitor dosage, the higher the content of NH+4-N in soil. Compared with the single application of urea, urea+DCD model could all increase wheat yield at 0.5%, 1%, 2% concentration and reached a significant level(P<0.05). When THU was added at 1% and 2%coucentration, wheat yield was significantly higher than that of the single application of urea, but the increase yield effect was lower than that of DCD treatment. On the whole, the effect of SCU on the control and release nitrogen was more lasting than that of nitrification inhibitor, among three nitrification inhibitors, TFR and DCD were better than THU in controlling soil ammonia nitrogen transformation, soil nitrification inhibition and urease inhibition. The study can provide scientific basis for the screening of nitrification inhibitors and coated fertilizers, but the long-term use of exogenous additives may cause potential harm to soil environment, so it need to be further studied about the morphological transformation and long-term role of different nitrification inhibitors in the soil.