Preparation for Polyvinyl Alcohol Hollow Microsphere and Its Sustained Release Effect on Urea

[Objective] The aim of this study was to discuss the optimizing preparation conditions of polyvinyl alcohol(PVA)hollow microsphere and its application in the production of slow-release urea fertilizer.[Method]PVA hollow microsphere was prepared by the emulsion chemical cross-linking method,while its composition,morphology and particle size was analyzed by technologies of FT-IR,SEM and TEM respectively.Thus,factors such as rate of emulsified speed,crosslink temperature and linking agent amount with effects on morphology and particle size of hollow microsphere were also discussed in this study.Furthermore,based on the optimizing preparation conditions,PVA fertilizer carrier microsphere was prepared by coating urea to investigate its sustained release effect on urea.[Result]The optimizing preparation conditions of polyvinyl alcohol(PVA)hollow microsphere were as follows:rate of emulsified speed 6 000 r/min,crosslink temperature 35 ℃ and linking agent amount 25 ml.PVA fertilizer carrier microsphere had significant sustained release effect on urea,and the optimal cross-linking time was 3 hours.[Conclusion]This study provides theoretical basis for the development of new slow-release fertilizer.

Study on Release Properties of Slow Release Urea Coated by Industrial Lignin

This study aimed to investigate the release properties of slow release ure- a coated by industrial lignin and the influences of temperature, pH and post-ripening period on the release of nutrients in coated urea. According to the experimental results, the release of nutrients in coated fertilizers showed an S-shaped curve; on the 28th d, the nutrient release rate reached 73.77%; the differential solubility was 1.83%, and the theoretical release period was 50.25 d. The release of nutrients was significantly influenced by temperature. As the incubation temperature rose from 25 to 40 ℃, preliminary solubility increased from 8.03% to 16.24%; differential solubility increased from 1.83% to 1.88%; theoretical release period was reduced from 51.25 d to 45.55 d. The release of nutrients was promoted by H＋ and OH-. After they were placed at room temperature within 30 d, coated fertilizers exhibited the optimal release properties.

Synthesis and Performance of Polyurethane Coated Urea as Slow/controlled Release Fertilizer

Polyurethane coated urea slow/controlled release fertilizer was prepared based on urea granules, isocyanate, polyols and paraffin. Isocyanate reacted with polyols to synthesize the polyurethane skin layer on urea granules surface. Paraffin serves as a lubricant during syntheses of polyurethane skin layers. The structure and nutrient release characteristics of the polyurethane skin layers were investigated by FTIR, SEM and TG. Urea nitrogen slow-release behavior of the polyurethane coated urea was tested. The experimental results indicated that compact and dense polyurethane skin layers with a thickness of 10-15 lam were formed on urea surface, the urea nitrogen slow-release time can reach 40-50 days. Paraffin proves to play a key role in inhibiting water to penetrate into urea, but excessive addition would decrease the polyurethane crosslinking density.

The Production of Organic-Inorganic Compound Film-Coated Urea and the Characteristics of Its Nutrient Release

The effect of different concentrations of natural macromolecular compound on the characteristics of nutrient release in the membrane materials of organic-inorganic compound film-coated urea was discussed, and the optimal concentrations for better nutrient release was proposed. The characteristics of nutrient release of film-coated urea were evaluated by soil column leaching experiment. Organic-inorganic compound film-coated urea showed good characteristics of nutrient release, which could be well simulated by Logistic curve. The two parameters in this curve, a and r, can be used to present nutrient release of film-coated urea, and followed the order of B 〉 C 〉 A and C 〈 B 〈 A, respectively, indicating that the release was stronger with the increasing concentration of natural macromolecular compound in the membrane, which implied better controllability of nutrient release. The concentration of 5% of natural macromolecular compound showed better characteristic of nutrient release and can be utilized as a membrane material combined with inorganic mineral powders to develop film-coated slow-release fertilizer.

Assessment of the crucial factors influencing the responses of ammonia and nitrous oxide emissions to controlled release nitrogen fertilizer: A meta-analysis

Reducing ammonia(NH3) and nitrous oxide(N2O) emissions have great effects on mitigating nitrogen(N) nutrient loss and greenhouse gas emissions. Controlled release urea(CRU) can control the N release rate, which reduces reactive N loss and increases nitrogen use efficiency relative to conventional urea(CU). However, the crucial factors influencing the responses of NH3and N2O emissions to CRU relative to CU are still unclear. In this study, we evaluated the responses of NH3and N2O emissions to CRU based on collected field data with a meta-analysis. CRU reduced the NH3and N2O emissions by 32.7 and 25.0% compared with CU, respectively. According to subgroup analysis, CRU presented better mitigation of NH3and N2O emissions in soils with pH 6.5–7.5(–47.9 and –23.7%) relative to either pH<6.5(–28.5and –21.4%) or pH>7.5(–29.3 and –17.3%), and in the rice season(–34.8 and –29.1%) relative to the wheat season(–19.8 and –22.8%). The responses of NH3and N2O emissions to CRU increased from rainfed(–30.5 and –17.0%) to irrigated(–32.5 and –22.9%), and then to paddy(–34.8 and –29.1%) systems. In addition, the response of N2O emission mitigation increased with increases in soil total nitrogen(TN);however, soil TN did not significantly affect the response of NH3volatilization. The reduction in NH3emission was greater in sandy-textured soil(–57.7%) relative to loam-textured(–32.9%) and clay-textured(–32.3%) soils, whereas soil texture did not affect N2O emission. Overall, CRU was a good option for reducing the NH3and N2O emissions relative to CU in agricultural production. This analysis improves our understanding of the crucial environmental and management factors influencing the mitigation of NH3and N2O emissions under CRU application, and these site-specific factors should be considered when applying CRU to reduce reactive N loss and increase NUE.

Effects of controlled-release urea application on the growth, yield and nitrogen recovery efficiency of cotton

Field experiments were conducted to study the effects of the controlled release urea (CRU) application on growth yield and nitrogen recovery efficiency of cotton in the main cotton zone of the Yangtze River basin in 2010. Different nitrogen levels were set in order to determine the suitable dosage of CRU on cotton. The special purpose was to provide evidence for the CRU application in cotton fields. The results show that the application of CRU promotes the growth of cotton significantly and enhances the nitrogen supply in the whole period. Compared to the treatment with total N as base fertilizer (UB), the bod, flower, little bolls and total bolls are increased significantly. There are no significant differences in the yield between the CRU treatment and the treatment of controlled release urea and urea combined application (60%CRU + 40%U), but an increase by 12.38%-22.67% compared to the UB treatment, and an increase by 4.49%-7.23% compared to the treatments of total N split application (UD). The nitrogen uptake of CRU treatment was significantly increased by 13.01%-48.32% and 30.27%-13.01% than UB treatment and UD treatment, respectively. The nutrient recovery efficiency of CRU treatment is increased by 16.42-20.59, 5.92-11.29 and 4.22-12.59 percentage points compared to the UB treatment, UD treatment and 60%CRU + 40%U treatment, respectively. In this study, there was a good linearity relationship between the cotton yield and amount of CRU in Wuxue site. The yield of cotton response to amount of CRU could be described by the model of linear plus plateau in Jingzhou site.

Nitrogen deposition and release pattern of slow release fertiliser made from urea-impregnated oil palm frond and rubberwood chips

The fertiliser industry faces a continuing challenge to improve the efficiency of their products,particularly of nitrogenous fertilisers,and to minimise adverse impacts.Therefore,a new slow release fertilizer,ureaimpregnated woodchips from tropical plant biomass(oil palm frond and rubberwood),was developed.The morphology of the impregnated woodchips was investigated by scanning electron microscopy and the success of impregnation of urea and nitrogen deposition into the woodchips was confirmed by energy dispersive X-ray spectrometry.When nitrogen release patterns from impregnated woodchips fertiliser were simulated using a soil solution and distilled water as leaching solutions in a static condition for 768 h,release was slow and steady,although the release rate was lower in distilled water than in the soil solution.

Release Kinetics of Urea from Polymer Coated Urea and Its Relationship with Coating Penetrability

Four kinds of polymer coated urea(PCU)were put in distilled water at 30℃ to determine the variation of coating penetrability and give a precise description of the urea release kinetics. The urea release from PCU could be divided into four stages: lag stage, swell stage, steady stage and decay stage. The release rate coefficient K, a measure of coating penetrability, was linearly increased at swell stage, but almost not variable at steady stage. At decay stage, the relation of X to time t could be described by the equation K= mtn-1where m and n are the coefficients). When n>1, the coating penetrability was gradually increased, and the urea release from PCU was accelerated; when n=1, the coating penetrability was steady, and the urea release from PCU obeyed the first-order kinetics; and when n<1.the coating penetrability was gradually decreased, and the urea release from PCU was delayed, resulting in a significant 'tailing effect'.

Study on Membrane Microstructures and Characteristics of Infrared Spectra and Nitrogen Release of Solid-Liquid Reaction Coated Urea

The membrane microstructures and the mechanism of two coated ureas formed through solid- liquid reaction were observed by scanning electron microscope and infrared spectra, the relation of the structural characteristics with the nitrogen release feature was also discussed by combining with nitrogen dissolution in water. The results showed that the membranes were made of solid particles tightly connected to each other and were piled up layer by layer through liquid glue. Porosity and aperture of membrane were determined by compactness of piled layers and the particles in a single layer and also related to the characteristics of coating materials. Research of the infrared spectra of membrane, made of a solid powder and a liquid glue, proved that O-H on the solid surface was bonded with the double bond of the liquid glue, thus forming membrane and keeping it stable. It was found that the two coated ureas showed obvious differences in nitrogen releasing due to their membrane structures, the porosity and aperture of membrane were the critical factors for nitrogen releasing.

Used for the Study of Nitrogen Fertilizer Slow-Release Carrier Life Sludge

After the sewage treatment, putting the wet sludge in which the heavy metal content is extremely low, corrupt and broken straw, bentonite, urea in proportioning according to the certain ratio, mixing well-distributed, taking the shape of Nitrogen slow-release fertilizers, doing the dynamic bioleaching test by the method of Artificial rainfall simulation, researching the slow-release characteristic, water retention. When the mass ratio of the wet sludge whose water content is 82.5%: bentonite: corrupt and broken straw: urea is 62.5: 12.5: 12.5: 12.5, drip washing the 10g Nitrogen slow-release fertilizers by the 80ml distilled water after 48h, the residue rate of urea is 29.63%; Under the room temperature of 25 ℃, 77%RH, moisture evaporate 46.32% after 60 h. The results demonstrate that the slow-release fertilizer has a good release-effect of nitrogen and water conservation effect. It provides the basic for the development and application of the sewage in the aspect of Nitrogen slow-release fertilizers.

控释尿素与普通尿素配施对橡胶树叶片和胶乳养分及产量的影响

为了明确控释尿素与普通尿素配施在橡胶树上的应用效果,通过2年田间试验,研究了减氮条件下控释尿素与普通尿素不同比例配施对橡胶树产量、叶片和胶乳矿质养分及土壤氮含量的影响,为橡胶树栽培管理中合理施氮提供技术支撑。结果表明:控释尿素与普通尿素配施可提高橡胶树干胶产量和叶片氮含量,与常规施肥相比,橡胶树干胶产量增幅为16.28%~39.13%(2021年)和7.94%~9.69%(2022年),叶片氮含量增幅为10.54%~19.17%(2021年)和10.24%~21.50%(2022年),控释尿素与普通尿素配施处理叶片氮含量均处于正常值以上。控释尿素与普通尿素配施还能够增加胶园肥穴土壤碱解氮含量,较常规施肥增加了11.27%~80.36%。控释尿素与普通尿素配施比例为50∶50时,橡胶树干胶产量(2022年)、叶片氮含量(2021—2022年)和土壤碱解氮含量(2021—2022年)均显著高于常规施肥。综上所述,在本试验条件下,控释尿素与普通尿素配施比例为50∶50能够获得较高的干胶产量,可改善叶片营养状况,维持土壤氮水平,有利于实现橡胶树施肥管理的绿色协同增效。

缓控释肥配施脲铵运筹对水稻产量、氮素利用效率和土壤养分的影响

通过田间试验,以传统配方肥+尿素一基两追施肥模式(CG)为对照,研究了以脲甲醛类缓控释肥(NC)和木质素类缓控释肥(MC)为基肥、脲铵为分蘖或穗分化追肥的缓控释肥+脲铵一基一追施肥模式对水稻产量、氮吸收累积、氮素利用效率以及土壤养分的影响。结果表明:缓控释肥+脲铵一基一蘖施肥模式水稻产量与CG处理相比无明显差异,但脲甲醛类缓控释肥+脲铵(NC-S)和木质素类缓控释肥+脲铵一基一穗(MC-S)处理分别比CG处理明显增产3.96%和6.01%,主要原因为NC-S和MC-S处理每穗粒数分别比CG处理明显增加16.7%和17.6%;与CG处理相比,脲甲醛类缓控释肥+脲铵(NC-F)和木质素类缓控释肥+脲铵一基一蘖(MC-F)处理成熟期地上部氮累积分别比CG处理增加2.50%和5.89%,NC-S和MC-S处理分别比CG处理明显增加10.0%和11.6%;NC-S和MC-S处理氮素利用效率(NUE)分别比CG处理高3.96%和6.01%。缓控释肥+脲铵一基一追施肥模式增加了水稻氮吸收效率(NupE)和表观氮肥回收效率(ANR),其中MC-S处理的NupE明显比CG处理高11.6%,NC-S和MC-S处理的ANR分别比CG处理明显高25.4%和29.3%。缓控释肥+脲铵一基一追施肥模式土壤碱解氮含量明显比CG处理增加6.58%~10.7%,其中,一基一穗施肥模式增加比例更大;另外,土壤有机质含量比CG处理增加1.11%~7.56%。由此可见,缓控释肥+脲铵一基一穗施肥模式更有利于提高水稻产量和氮素利用效率,增加土壤肥力。

控释尿素和有机物料添加提高黄壤冬油菜产量及养分吸收利用

利用田间试验探讨控释尿素和不同有机物料添加对黄壤冬油菜产量、养分吸收及利用的影响,为贵州黄壤地力改善以及冬油菜丰产提质提供科学依据。于2018—2022年连续4年在贵州省贵阳市开展控释尿素和不同有机物料添加长期定位试验,以冬油菜为试验材料,分别设置不施氮肥(U0)、控释尿素(CRU180)、普通尿素(U180)以及在普通尿素施用下配施3种有机物料[秸秆(U180+S)、生物炭(U180+B)和商品有机肥(U180+O),均为3000 kg/hm^(2)],在冬油菜收获后,分别测定不同处理冬油菜产量、产量构成因子、生物量、养分吸收和利用。结果表明,与U0处理相比,CRU180和U180处理冬油菜产量分别提高732.5和588.8 kg/hm^(2),配施有机物料后,U180+S、U180+B和U180+O处理冬油菜产量较U180处理分别增加516.9、662.6和622.0 kg/hm^(2),其中以U180+B处理冬油菜产量最高,为2646.8 kg/hm^(2)。与U0处理相比,CRU180和U180处理冬油菜地上部生物量显著增加;与U180处理相比,配施有机物料显著提高冬油菜地上部生物量,4年均以U180+B处理最优,但与U180+S和U180+O处理差异不显著。冬油菜氮磷钾累积量均以U180+B处理最大,4年平均值分别为164.7、31.9和139.1 kg/hm^(2)。CRU180处理氮素农学效率(AEN)、偏生产力(PEPN)和吸收利用效率(REN)高于U180处理;配施有机物料后,U180+S、U180+B和U180+O处理冬油菜AEN、PEPN和REN较U180处理均呈现增加的趋势,其中以U180+B处理最高,分别为6.95 kg/kg、14.70 kg/kg和38.43%,高于其他处理。U180+S处理冬油菜经济效益为7109.9元/hm^(2),高于其他处理。综上所述,控释尿素和有机物料(秸秆、生物炭和商品有机肥)添加均能提高冬油菜产量和养分吸收及利用,且以配施生物炭冬油菜产量最高,但配施秸秆冬油菜经济效益最优,建议在贵州黄壤区冬油菜生长季,正常肥料施用量情况下,可施用控释尿素替代常规尿素,且适当增施外源有机物料以保证冬油菜的产量和养分吸收利用效率。

缓释尿素减施对冬小麦产量和氮素利用效率的影响

为优化旱地小麦高效施氮管理,实现高效生产目标,通过2 a(2019—2020年度和2020—2021年度)田间试验,设不施肥(CK)、不施氮(T1)、300 kg·hm^(-2)尿素N(T2,常规施氮处理)、300 kg·hm^(-2)缓释尿素N(T3)、195 kg·hm^(-2)缓释尿素N(T4)和90 kg·hm^(-2)缓释尿素N(T5)6个处理,分析不同缓释尿素减施量对农田土壤硝态氮分布及累积、氮素吸收与转运、冬小麦产量和氮素利用效率的影响。结果表明,缓释尿素减施处理(T4和T5)显著降低收获期0~200 cm土层的土壤NO-3-N累积量,同时提高0~40 cm土层NO-3-N占比。施用缓释尿素显著提高冬小麦氮素转运量和花后氮素吸收量,T3处理较当地常规施氮处理分别提高12.9%和13.6%。氮素转运对籽粒的贡献率随缓释尿素减施比例的增加呈先增后降的变化趋势,T4处理最大,较其他施氮处理提高0.2%~50.0%。施用缓释尿素可不同程度地改善冬小麦产量构成因素和提高产量;T4处理两年产量分别为8 434、9 060 kg·hm^(-2),2019—2020年度较T2和T3处理分别提高19.7%和13.9%,2020—2021年度分别提高17.3%和10.4%,其经济效益2019—2020年度较T2和T3处理分别提高33.3%和34.0%,2020—2021年度分别提高26.8%和23.2%。缓释尿素减施显著降低氮素表观损失,提高了氮素利用效率和氮肥偏生产力。通过拟合分析发现,缓释尿素施用量为208.7 kg·hm^(-2)时,两年产量分别为8 054、8 806 kg·hm^(-2),净效益分别为6 890、8 475 CNY·hm^(-2),NHI分别为78.2%和78.9%,可实现西北旱区冬小麦高产高效。

不同增效氮肥的制备及缓释性能研究

尿素添加增效剂,采用圆盘造粒法制备增效氮肥,考察了增效剂种类、增效剂添加量、黏结剂种类及黏结剂添加量对增效尿素产品缓释性能的影响。借助于SEM、FTIR等表征技术,结合颗粒平均强度等性能测定分析产品的构效关系。实验结果表明,在静水环境中,增效剂选用质量分数为5%的硼酸、黏结剂选用质量分数为5%的CaCl_(2)制备出的肥料样品缓释性能最佳,在7 d内尿素态氮缓释率仅为81.54%;SEM显示,最优条件下所制备的肥料样品内部形成了三维网络结构;FTIR显示,样品中引入了钙离子,增效剂和黏结剂双重作用,使得尿素结构发生变化,提升了样品的氮缓释性能。

AMT及其复配剂对青铜合金的缓蚀机理研究

青铜文物是国之瑰宝,其组织成分主要是青铜合金,本工作以青铜合金为研究对象,对合金表面的缓蚀效率及机理进行实验探索,为青铜文物保护材料的性能研究提供实验支持。采用失重法和电化学极化测试研究了2-氨基-5-巯基-1,3,4-噻二唑(AMT)复配尿素和三聚氰胺作为青铜合金缓蚀剂的缓蚀效率。失重实验结果表明,随着AMT浓度的增大,试样在三组实验腐蚀溶液中缓蚀效率均上升,其中1%AMT复配尿素组在NaCl溶液中的缓蚀效率为最大。电化学分析结果表明,随着加入电解液中AMT浓度的增加,1%AMT复配尿素组的腐蚀电位比1%AMT组上升了0.08 V,缓蚀效率为89.8%。采用SEM和XPS对试样表面含Cu的AMT缓蚀膜进行了分析,并对缓蚀机理进行探讨,结果表明,铜离子与AMT反应生成Cu(I)-AMT络合物,吸附在青铜表面起到缓蚀作用。

缓释尿素对育肥牦牛生产性能和屠宰性能的影响

试验考察了在饲粮中添加缓释尿素对育肥牦牛生产性能、屠宰性能以及血液生化指标的影响。选择健康体重相近[(277.9±10.4)kg]麦洼公牦牛24头,分为3个处理组,分别为对照组:饲喂原场全混合饲粮(代谢能11.03 MJ/kg,CP 10%);0.5%组:添加玉米干酒糟及其可溶物(DDGS)替代部分粗饲料,降低饲粮中粗料水平,并添加0.5%缓释尿素(TMR的代谢能11.35 MJ/kg,CP 12.77%);1.0%组:利用玉米DDGS替代饲粮中的豆粕和菜粕,并添加1.0%缓释尿素(TMR的代谢能11.42 MJ/kg,CP 12.77%)。牦牛预试期10 d,正试期60 d,在第60天晨饲前收集血清进行指标测定。结果表明:①0.5%组平均日增重高于对照组(P<0.05)。②0.5%组和1.0%组的谷丙转氨酶活性高于对照组(P<0.05),1.0%组高于0.5%组(P<0.05);1.0%组的谷草转氨酶活性高于对照组(P<0.05);1.0%组的血氨浓度高于对照组(P<0.05);1.0%组血浆尿素氮浓度高于0.5%组和对照组(P<0.05)。③0.5%组屠宰率和净肉率分别比对照组高1.1和1.4个百分点(P>0.05)。④0.5%组和1.0%组经济效益较对照组分别提高24.03%和29.96%。联合运用1.0%缓释尿素和玉米DDGS可以完全替代育肥牦牛日粮中的豆粕和菜粕并提高养殖经济效益。

一次性施肥对不同生态区夏玉米产量和氮肥效率的影响

为研究一次性施用缓(控)释肥对黄淮夏玉米产量、氮肥利用率和经济效益的影响,于2021年在河南省6个试验点开展一次性施用控释尿素或缓释尿素配施普通尿素的田间试验。共设置9个处理:不施氮肥(CK),单施普通尿素(U1),农民习惯施肥(U2),控释尿素与普通尿素配施(CRU)包括3∶7(CRU1)、5∶5(CRU2)、7∶3(CRU3)3种比例,缓释尿素与普通尿素配施(LCU)包括3∶7(LCU1)、5∶5(LCU2)和7∶3(LCU3)3种比例。研究控释尿素或缓释尿素配施普通尿素对夏玉米产量、氮素利用和经济效益的影响。结果表明,施氮处理较不施氮增产11.6%~49.1%,平均产量表现为CRU>LCU>U(U1、U2),CRU和LCU平均产量较U分别提高23.3%和9.7%,其中CRU2产量最高,为9444.0 kg·hm^(-2),较其他施氮处理提高8.0%~33.6%,LCU2产量次之。CRU和LCU干物质积累量、穗粒数、千粒重较U均显著提高。CRU2氮肥表观利用率最高,为36.9%,LCU2次之,为33.2%。与U相比,CRU和LCU 0-40 cm NO_(3)^(-)-N含量较高,深层土壤(40-100 cm)NO_(3)^(-)-N含量明显降低,分别平均增收2186和995元·hm^(-2)。夏玉米产量可持续性指数与产量高低、变异系数均相关,CRU2和LCU2产量较稳定,可持续性较好。综合产量、氮素利用和经济效益,推荐控释尿素与普通尿素5∶5配施的施肥模式在黄淮夏玉米生产上一次性施用。研究结果可为夏玉米轻简化生产和氮肥高产高效提供依据。

长期施用控释尿素对潮土土壤酸碱缓冲体系与土壤肥力的影响

[目的]为探究长期施用控释尿素对北方石灰性潮土土壤酸度、酸碱缓冲能力及肥力的影响。[方法]基于自2008年开始的长期定位小麦玉米轮作施肥试验,设计掺混控释尿素和普通尿素2种氮肥类型及不施氮[N 0 kg/(hm^(2)·a)]、常量[N 540 kg/(hm^(2)·a)]和增量[N 810 kg/(hm^(2)·a)]3个施氮水平,于2022年玉米季成熟期采集0—80 cm土层土壤样品,测定土壤酸碱缓冲容量、土壤碳酸钙含量与土壤养分。[结果](1)控释尿素减缓了因施氮导致的土壤缓冲容量和pH下降,缓解了土壤酸化过程。常量掺混控释尿素、增量掺混控释尿素处理的缓冲容量分别较普通尿素处理常量普通尿素、增量普通尿素升高5.22%和11.17%,常量掺混控释尿素、增量掺混控释尿素处理的pH分别较常量普通尿素、增量普通尿素升高0.17和0.08个单位。(2)控释尿素提高了土壤阳离子交换量与交换性钙镁含量,提高了耕层土壤的活性碳酸钙含量,常量掺混控释尿素和增量掺混控释尿素处理活性碳酸钙含量分别较常量普通尿素和增量普通尿素处理升高52.08%和45.31%。同时,控释尿素减缓了土壤深层次土壤碳酸钙含量损失。(3)控释尿素提高了土壤全氮、有机质、硝态氮和铵态氮含量。[结论]长期施用控释尿素缓解了因施用氮肥导致的土壤酸化,提高了土壤活性碳酸钙含量,提高了土壤肥力。

不同灌水定额下缓释氮肥与尿素混掺对玉米生长和产量及水肥利用效率的影响

为旱区建立玉米种植的高效水肥管理技术提供理论依据。通过玉米盆栽试验,设置3个灌水定额(W1:2 548 m^(3)/hm^(2),W2:1 911 m^(3)/hm^(2),W3:1 433 m^(3)/hm^(2))和3个氮肥类型(U:尿素,UNS:尿素与缓释氮肥以纯氮含量比3∶7混掺,SRF:缓释氮肥),以不施氮肥W3灌溉量为对照(CK),研究不同灌水量和氮肥类型对玉米生长指标、产量及构成、灌溉水分利用效率(IWUE)及氮素利用效率(NUE)的影响。结果表明,氮肥类型与灌溉量及两者交互作用对玉米生长指标、单株干物质累积量、产量及产量构成要素、IWUE和NUE有显著影响(P<0.05)。不同氮肥类型处理下,W1水平下的平均玉米株高、叶面积、叶绿素含量、净光合速率、单株干物质累积量、产量及产量构成和NUE均显著高于W2和W3。同一氮肥类型在不同的灌溉量下对玉米生长的响应有所差异。W1灌溉水平下,SRF的平均产量较UNS和U分别提高2.01%和12.71%,但在W2和W3灌溉水平下,产量的整体趋势表现为UNS>SRF>U。处理W3UNS的IWUE最高,处理W1UNS的NUE最高。通过整体差异组合评价模型分析得出排名前两名的处理为W1SRF和W1UNS。综合分析,灌溉量2 548 m^(3)/hm^(2)的前提下,缓释氮肥或缓释氮肥与尿素混掺一次性基施,可同时兼顾玉米生长、产量和水肥利用效率。