控释氮肥减量对糜子产量、氮素利用及土壤氮含量的影响

针对黄土高原旱作区糜子生产中氮肥种类单一、肥料利用效率低的问题,本试验以当地习惯施氮尿素N 120kg/hm²(TN)为对照,设置控释氮肥N 120kg/hm²(T1)、108kg/hm²(T2)、96kg/hm²(T3)、84kg/hm²(T4)、72kg/hm²(T5)和不施肥(T0)七个处理,探究不同控释氮肥处理下土壤全氮、微生物量氮、硝态氮和铵态氮含量的变化规律,分析糜子成熟期氮素积累分配、氮素利用效率及产量对控释氮肥的响应,以期为建立旱地糜子控释氮肥一次性基施轻简栽培技术提供支撑。结果表明：与施用尿素相比,等量控释氮肥可以提高糜子抽穗期和成熟期土壤全氮、微生物量氮、硝态氮和铵态氮含量分别达0.38%~5.51%、1.76%~7.63%、5.41%~11.80%和4.04%~14.77%,其中硝态氮和铵态氮含量两年均显著高于TN,随着控释氮肥减量糜子田各形态氮素均呈降低趋势,减氮量达20%以上时土壤硝态氮和铵态氮含量均显著低于TN处理。施用控释氮肥可以提高糜子成熟期氮素积累量1.97%~3.21%,增加糜子氮素向籽粒中的分配比例0.55%~1.18%,控释氮肥减量20%以上时糜子氮素积累量显著低于尿素全量基施处理。与普通尿素相比,控释氮肥提高了糜子氮肥表观利用率、氮肥偏生产力及氮肥农学利用率,增幅分别为3.29%~4.59%、3.88%~4.14%和5.01%~7.63%,其中氮肥偏生产力处理间差异达显著水平,随着控释氮肥减量糜子氮肥表观利用率、氮肥偏生产力及氮肥农学利用率均呈上升趋势。施用控释氮肥通过增加单位面积穗数和穗重显著提高了糜子产量两年分别达3.88%和4.47%,控释氮肥减量20%以下时糜子产量与尿素差异不显著。相关性分析结果表明,糜子氮素积累量与产量呈极显著正相关,氮素利用效率指标与土壤硝态氮含量相关性最强。综上所述,施用控释氮肥较尿素可显著提高糜子生育中后期土壤供氮能力,促进糜子对氮素的吸收利用进而增加产量,且在适量减氮20%时并未显著降低糜子产量,因此控释氮肥在糜子生产中有较大的应用前景及减氮潜力。

Effects of Controlled-release N Fertilizer Reduction on Prosomillet Yield, Nitrogen Utilization and Soil N Content

To address the problems of single type of N fertilizer and low fertilizer utilization efficiency in millets production in the dry crop area of Loess Plateau, this experiment was conducted with local customary N application of urea N 120kg.hm^-2(TN) as the control and controlled-release N fertilizer N 120kg.hm^-2(T1), 108kg.hm^-2(T2), 96kg.hm^-2(T3), 84kg.hm^-2(T4), 72kg.hm^-2(T5) and no fertilizer(T0), to investigate the changes of soil total nitrogen, microbial nitrogen, nitrate nitrogen and ammonium nitrogen contents under different controlled-release nitrogen fertilizer treatments, and to analyze the nitrogen accumulation distribution, nitrogen utilization efficiency and yield response to controlled-release nitrogen fertilizer during the maturity of millets, in order to provide support for the establishment of dryland millets controlled-release nitrogen fertilizer one-time base application and light cultivation technology. The results showed that compared with urea application, the equal amount of controlled-release N fertilizer could improve the soil total N, microbial N, nitrate N and ammonium N contents at the tassel and maturity stages of millets by 0.38%~5.51%, 1.76%~7.63%, 5.41%~11.80% and 4.04%~14.77%, respectively, among which the nitrate N and ammonium N contents were significantly higher than TN in both years, and with the controlled-release fertilizer reduction in millets, the soil N accumulation efficiency was significantly higher than TN in both years. N fertilizer reduction in millets showed a trend of decreasing all forms of nitrogen, and the soil nitrate and ammonium nitrogen contents were significantly lower than TN treatment when the nitrogen reduction amount reached 20% or more. The application of controlled-release nitrogen fertilizer could increase the nitrogen accumulation of millets at maturity from 1.97% to 3.21%, and increase the distribution of millets nitrogen to seeds from 0.55% to 1.18%, and the nitrogen accumulation of millets at 20% or more reduction of controlled-release nitrogen fertilizer was significantly lower than that of the full base application treatment of urea. Compared with normal urea, controlled-release N fertilizer increased the apparent N fertilizer utilization, N fertilizer bias productivity and N fertilizer agronomic utilization of millets by 3.29%~4.59%, 3.88%~4.14% and 5.01%~7.63%, respectively, among which the difference between treatments of N fertilizer bias productivity reached a significant level, and with the reduction of controlled-release N fertilizer the apparent N fertilizer utilization, N fertilizer bias productivity and N fertilizer agronomic utilization of millets showed an increasing trend. The trend of N fertilizer bias productivity and N fertilizer agronomic utilization rate were all increasing. The application of controlled-release N fertilizer significantly increased the yield of millets by increasing the number of spikes per unit area and spike weight by 3.88% and 4.47% in two years, respectively, and the difference between millets yield and urea was not significant when the controlled-release N fertilizer was reduced by less than 20%. The results of correlation analysis showed that the nitrogen accumulation of millets was highly significantly and positively correlated with yield, and the nitrogen use efficiency index was most strongly correlated with soil nitrate nitrogen content. In conclusion, the application of controlled-release nitrogen fertilizer can significantly improve the soil nitrogen supply capacity and promote the nitrogen uptake and utilization of millets compared with urea in the middle and late stages of millets fertility, thus increasing the yield, and it did not significantly reduce the yield of millets at a moderate nitrogen reduction of 20%. Therefore, controlled-release nitrogen fertilizer has a greater application prospect and potential for nitrogen reduction in millets production.