15N标记水稻控释氮肥对提高氮素利用效率的研究

本文应用^15N示踪技术研究了水稻对空控释氮肥和尿素氮吸收利用效率的影响以及氮的去向,结果表明：施肥后11天内,水稻控释氮肥和尿素的NH3挥发损失分别占施入氮量的0.69%和1.81%,NH3的挥发损失在施肥后第5天时达到最大值,此后逐渐降低。水稻控释氮肥和尿素氮的淋溶损失分别占施入氮量的0.95%和1.02%,水稻控释氮肥氮的淋溶损失在水稻整个生长期间均比较平缓,施肥后40天时略有上升,此后又缓慢降低。用氮素平衡帐中的亏缺量和缺量扣除氨的损失量后计为硝化-反硝化损失量的结果表明,水稻控制氮肥氮的硝化-反硝化损失量占施氮量的3.46%,而尿素氮在硝化-反硝化损失量却高达37.75%,肥料氮在土壤中的残留主要集中在0～35cm的土层中,达91.4%-91.5%,残留在35cm以下土层中的氮甚微,水稻控制氮肥残留在土壤中的氮量略高于尿素处理。水稻控释氮肥利用率高达73.8%,比尿素高出34.9%,水稻控释氮肥氮利用率高的原因是因氮从颗粒中缓慢释放、受淋溶、氨挥发、尤其受硝化-反硝化途径损失的氮较少。在施等氮量的条件下,施用水稻控制氮肥的稻谷产量比尿素的增产25.5%,达到p=0.05的显著水平。     

Use of urease inhibitors to reduce ammonia loss following application of urea to flooded rice fields

Ammonia (NH₃) volatilization is an important mechanism for nitrogen (N) loss from flooded rice fields following the application of urea into the floodwater. One method of reducing losses is to use a urease inhibitor that retards the hydrolysis of urea by soil urease and allows the urea to diffuse deeper into the soil. The two chemicals that have shown most promise are phenylphosphorodiamidate [PPD] and N(n-butyl)thiophosphorictriamide [NBPT], but they seldom work effectively. PPD decomposes rapidly when the pH departs from neutrality, and NBPT must be converted to the oxygen analogue for it to be effective. Our field studies in Thailand show that the activity of PPD can be prolonged, and NH₃ loss markedly reduced, by controlling the floodwater pH with the algicide terbutryn. A mixture of NBPT and PPD in the presence of terbutryn was even more effective than PPD alone. It appears that during the time when the PPD was effective, NBPT was being converted to the oxygen analogue. The combined urease inhibitor-algicide treatment reduced NH₃ loss from 10 to 0.4 kg N ha^-1.     

The molecular processes of urea hydrolysis in relation to ammonia emissions from agriculture

Ammonia emissions from the agricultural sector give rise to numerous environmental and societal concerns and represent an economic challenge in crop farming, causing a loss of fertilizer nitrogen. Ammonia emissions from agriculture originate from manure slurry (livestock housing, storage, and fertilization of fields) as well as urea-based mineral fertilizers. Consequently, political attention has been given to ammonia volatilization, and regulations of ammonia emissions have been implemented in several countries. The molecular cause of the emission is the enzyme urease, which catalyzes the hydrolysis of urea to ammonia and carbonic acid. Urease is present in many different organisms, encompassing bacteria, fungi, and plants. In agriculture, microorganisms found in animal fecal matter and soil are responsible for urea hydrolysis. One strategy to reduce ammonia emissions is the application of urease inhibitors as additives to urea-based synthetic fertilizers and manure slurry to block the formation of ammonia. However, treatment of the manure slurry with urease inhibitors is associated with increased livestock production costs and has not yet been commercialized. Thus, development of novel, environmentally friendly and cost-effective technologies for ammonia emission mitigation is important. This mini-review describes the challenges associated with the volatilization of ammonia in agriculture and provides an overview of the molecular processes of urea hydrolysis and ammonia emissions. Different technologies and strategies to reduce ammonia emissions are described with a special focus on the use of urease inhibitors. The mechanisms of action and efficiency of the most important urease inhibitors in relation to agriculture will be briefly discussed.     

Short-term effects of urea amended with the urease inhibitor N-(n-butyl) thiophosphoric triamide on perennial ryegrass

The current study investigated the short-term physiological implications of plant nitrogen uptake of urea amended with the urease inhibitor N-(n-butyl) thiophosphoric triamide (nBTPT) under both greenhouse and field conditions. ¹⁵N labelled urea amended with 0.0, 0.01, 0.1 and 0.5% nBTPT (w/w) was surface applied at a rate equivalent to 100 kg N ha^–1 to perennial ryegrass in a greenhouse pot experiment. Root, shoot and soil fractions were destructively harvested 0.75, 1.75, 4, 7 and 10 days after fertilizer application. Urease activity was determined in each fraction together with ¹⁵N recovery and a range of chemical analyses. The effect of nBTPT amended urea on leaf tip scorch was evaluated together with the effect of the inhibitor applied on its own on plant urease activity.nBTPT-amended urea dramatically reduced shoot urease activity for the first few days after application compared to unamended urea. The higher the nBTPT concentration the longer the time required for shoot activity to return to that in the unamended treatment. At the highest inhibitor concentration of 0.5% shoot urease activity had returned to that of unamended urea by 10 days. Root urease activity was unaffected by nBTPT in the presence of urea but was affected by nBTPT in the absence of urea.Transient leaf tip scorch was observed approximately 7–15 days after nBTPT + urea application and was greatest with high concentrations of nBTPT and high urea-N application rates. New developing leaves showed no visual sign of tip necrosis.Urea hydrolysis of unamended urea was rapid with only 1.3% urea-N remaining in the soil after 1.75 days. N uptake and metabolism by ryegrass was rapid with ¹⁵N recovery from unamended urea, in the plant (shoot + root) being 33% after 1.75 days. Most of the ¹⁵N in the soil following the urea+0.5% nBTPT application was still as urea after 1.75 days, yet ¹⁵N plant recovery at this time was 25% (root+shoot). This together with other evidence, suggests that if urea hydrolysis in soil is delayed by nBTPT then urea can be taken up by ryegrass as the intact molecule, albeit at a significantly slower initial rate of uptake than NH₄ ⁺-N. Protein and water soluble carbohydrate content of the plant were not significantly affected by amending urea with nBTPT however, there was a significant effect on the composition of amino acids in the roots and shoots, suggesting a difference in metabolism.Although nBTPT-amended urea affected plant urease activity and caused some leaf-tip scorch the effects were transient and short-lived. The previously reported benefit of nBTPT in reducing NH₃ volatilization of urea would appear to far outweigh any of the observed short-term effects, as dry-matter production of ryegrass is increased.     

The effect of intermittent flooding on the growth and yield of wetland rice and nitrogen-loss mechanism with surface applied and deep placed urea

Summary Wetland rice was cultivated in pots of puddled soil under continuous and intermittent flooding conditions. The soil was either fertilized with the surface application of prilled urea in three split doses or once with urea supergranules applied at different soil levels.The grain yield, fertilizer efficiency and percent nitrogen recovery by the grains were increased by deep placement of urea supergranules independent of the water regime. Grain yield was always lower with intermittent flooding, particularly when the plants were fertilized with the surface application of prilled urea.Nitrogen loss by ammonia volatilization, measured in a closed cuvette system, was reduced from 24% with the surface application of urea prills and 20% with surface application of urea supergranules to approximately 2% with deep placement of urea supergranules. Intermittent flooding created conditions which promoted additional nitrogen loss by nitrification and denitrification processes. The total nitrogen loss, measured in an open cuvette system, was about 38% with the surface application of urea supergranules, whereas this loss was reduced to 10% with deep placement of urea supergranules. Furthermore, deep placement of urea fertilizer reduced the nitrogen loss irrespective of water regime.     

脲酶抑制剂和硝化抑制剂的协同作用对尿素氮转化和N2O排放的影响

根据培养试验,论述了脲酶抑制剂氢醌和硝化抑制剂双氰胺和碳化钙的不同组合在土壤正常水分和渍水的条件下对于土中尿素的水解及其释出的氨的吸附、氧化和挥发以及Ｎ２Ｏ生成的影响．文章指出,配合使用氢醌和双氰胺既能延缓土中尿素的水解并使水解后释出的氨在土中得以更多和更长时间的保持,还能减少土中硝酸盐的累积、氨挥发的损失及Ｎ２Ｏ的生成．这表明在脲酶抑制剂和硝化抑制剂间可能存在一定的协同作用．很好利用这一作用,将有益于提高尿素肥效和减少其Ｎ损失与环境污染．     

Nitrogen transformation processes in relation to improved cultural practices for lowland rice

Summary Inappropriate method and timing of N fertilizer application was found to result in 50–60% N losses. Recent nitrogen transformation studies indicate that NH₃ volatilization in lowland rice soils is an important loss mechanism, causing a 5–47% loss of applied fertilizer under field conditions. Estimated denitrification losses were between 28 and 33%. Ammonia volatilization losses from lowland rice can be controlled by i) placement of fertilizer in the reduced layer and proper timing of application, ii) using phenylphosphorodiamidate (PPD) to delay urease activity in flooded soils, and iii) using algicides to help stabilize changes in floodwater pH. Appropriate fertilizer placement and timing is probably the most effective technique in controlling denitrification at the farm level. The effectivity of nitrification inhibitors as another method is still being evaluated. With 60–80% of N absorbed by the crop derived from the native N pool, substantial yield gains in lowland rice are highly possible with resources already in the land. Extensive studies on soil N and its management, and an understanding of soil N dynamics will greatly facilitate the decrease in immobilization and ammonium fixation in the soil and the increase in N availability to the rice crop. Critical research needs include greater emphasis on N transformation processes in rainfed lowland rice which is grown under more harsh and variable environmental regimes than irrigated lowland rice.     

不同包膜控释尿素对农田土壤氨挥发的影响

为了探索包膜控释尿素土壤氨挥发损失规律特征和提高肥料氮素利用率,采用小麦玉米轮作田间试验,通过与普通尿素进行对比,运用土壤氨挥发原位测定方法——通气法系统研究了硫包膜和树脂包膜控释尿素的施用对小麦玉米轮作农田土壤氨挥发的影响.研究结果表明:在两种施氮量水平下(210 kg/hm2和300 kg/hm2),与普通尿素相比,硫包膜和树脂包膜控释尿素在小麦基肥期、小麦追肥期和玉米施肥期的施用均减少了土壤氨挥发的累积损失量,分别达35.1％-54.3％、59.6％-75.2％、65.6％-98.1％;有效降低了土壤氨挥发通量峰值且延迟其出现时间3-8 d,并能延缓土壤氨挥发主要阶段的时间分别为4-12 d、5-12 d.在小麦玉米轮作周年中,控释尿素土壤氨挥发累积损失量为28.39-43.35 kg/hm2,土壤氨挥发损失率为4.48％-5.63％,控释尿素时段土壤氨挥发通量比普通尿素降低了51.0％-70.8％;且树脂包膜控释尿素的施用降低小麦玉米轮作农田土壤氨挥发的效果优于硫包膜控释尿素.     

Agronomic assessment and 15N recovery of urea amended with the urease inhibitor nBTPT (N-(n-butyl) thiophosphoric triamide) for temperate grassland

Three field experiments were undertaken concurrently at one site to evaluate a range of surface-applied nBTPT-amended urea products (0.01, 0.05, 0.1, 0.25 and 0.5% nBTPT w/w) on NH₃ volatilization, grass yield and ¹⁵N recovery in the plant-soil system. Each experiment was repeated on five separate occasions over the 1992 growing season to cover a range of weather conditions. Total NH₃ loss from unamended-urea ranged from 5.5% in early May to 20.8% in June. The inhibitor was highly effective in reducing ammonia volatilization and delaying the time at which maximum rate of NH₃ loss occurred. Over all time periods the % inhibition was 50.4, 82.8, 89.0, 96.5 and 97.0% at the 0.01, 0.05, 0.1, 0.25 and 0.5% nBTPT levels respectively. There was no significant difference in the overall % inhibition in ammonia loss at different times suggesting that the effectiveness of the inhibitor was not dependent on climatic conditions.Over all times incorporation of nBTPT at the 0.05% level increased dry-matter yield by 9% compared to urea alone and increased the shoot recovery of N from 66.7% to 80.9%. Nitrogen saved from volatilization was taken up by the plant, however, the subsequent translation into dry-matter yield appeared to be adversely affected at the high inhibitor rates.There was no significant effect of inhibitor on ¹⁵N recovery in soil at any depth down to 15 cms. nBTPT significantly increased (p < 0.001) the % N derived from fertilizer (% N dff) in the shoot compared to unamended-urea and increased (p < 0.01) the shoot recovery of ¹⁵N from 32% up to 39%. Total ¹⁵N recovery in the soil-plant system was increased by up to 17% by amending urea with nBTPT. This urease inhibitor has been shown to improve the efficiency of urea however, its potential for the European market will be dependent on economic factors.Faculty of Agriculture and Food Science, The Queen's University of Belfast     

Control of urea hydrolysis and nitrification in soil by chemicals—Prospects and problems

Summary A review is made of the recent work to assess the prospects of regulating urea hydrolysis and nitrification processes in soils by employing chemicals that can retard urea hydrolysis and nitrification. The possible benefits from control of nitrogen transformations in terms of conserving and enhancing fertilizer nitrogen efficiency for crop production and the problems associated with their use with regard to N metabolism of plants have also been discussed with examples. Prospects of using cheap and effective indigenous materials and chemicals for control of urea hydrolysis and nitrification under specific soil situations appear eminent in improving the fertilizer nitrogen efficiency. Urease inhibitors may be helpful in reducing problems associated with ammonia volatilization if this is not offset by leaching of urea. On the other hand retardation of nitrification appears useful in reducing losses that accompany nitrification due to leaching and denitrification, and with the plants that metabolize equally well with relatively higher amounts of NH₄–N may be more effective in improving the utilization of fertilizer N under these situations.     

生物炭配施硝化/脲酶抑制剂对亚热带水稻土活性氮气体排放的影响

探究施用生物炭和脲酶抑制剂/硝化抑制剂对亚热带水稻土氮素硝化过程的调控作用、氨挥发和N₂O排放的温室效应潜能的影响,确定生物炭与硝化和脲酶抑制剂的最佳组合,可为削减施用氮肥带来的活性氮气体排放对环境的负面风险提供理论依据。本研究采用室内好气培养试验方式,以单施尿素(N)为对照,设置7个试验处理[尿素+生物炭(NB),尿素+硝化抑制剂(N+NI),尿素+脲酶抑制剂(N+UI),尿素+硝化抑制剂+脲酶抑制剂(N+NIUI),尿素+硝化抑制剂+生物炭(NB+NI),尿素+脲酶抑制剂+生物炭(NB+UI),尿素+硝化抑制剂+脲酶抑制剂+生物炭(NB+NIUI)],观测生物炭与脲酶抑制剂(NBPT)/硝化抑制剂(DMPP)配施下土壤无机氮含量、N₂O排放及氨挥发的变化动态。结果表明: 1)培养期间,与N处理(5.11 mg N·kg^-1·d^-1)相比,NB处理的土壤硝化速率常数显著增加33.9%,N+NI处理显著降低22.9%;NB处理显著提高了氨氧化细菌(AOB)丰度,增幅达56.0%。2)与N处理相比,N+NI和NB+NI处理的NH₃累积排放量均显著增加约49%;N+UI处理降低了NH₃累积损失量,NB+UI处理抑制效果更明显。3)各处理的N₂O排放速率高峰均出现在施肥后前10 d;NB处理的N₂O排放高峰出现最早,N处理排放速率最高(5.87 μg·kg^-1·h^-1);硝化抑制剂与脲酶抑制剂配施减少土壤N₂O排放的效果最佳。综合计算各处理直接N₂O和间接N₂O(NH₃)排放产生的温室效应潜能(GWP)发现,N+NI和NB+NI处理较N处理分别增加了34.8%和40.9%,而NB和NB+UI处理的GWP显著降低了45.9%和60.5%。因此,生物炭与脲酶抑制剂配施对降低土壤活性氮气体排放所产生的温室效应潜能效果最佳。     

Ammonia volatilization losses from prilled urea,urea supergranules (USG) and coated USG in rice fields

Summary About 8.4 per cent of applied nitrogen was lost as ammonia during a week after application when prilled urea was broadcast or banded and incorporated in soil 20 days after sowing of rice. Ammonia volatilization was reduced to 3.3 per cent when urea supergranules (USG) were used. Coating of USG with DCD or neem cake showed no advantage. Ammonia volatilization was only 0.7 to 1.6 per cent when fertilizer was applied at panicle initiation stage of rice; highest values were again obtained with prilled urea. The experiments were carried out in closed cages.     

控释尿素条施深度对鲜食玉米田间氨挥发和氮肥利用率的影响

为提高鲜食玉米一次性施肥的氮肥利用率并降低氮肥的环境影响,通过田间试验,以不施氮处理为对照(CK),研究了控释尿素不同条施深度(0、5、10、15、20 cm)对鲜食玉米田间土壤氨挥发特征、鲜穗产量和氮肥利用率的影响. 结果表明: 玉米种植带和宽行非施肥带的土壤氨挥发主要发生在施肥后的前2周,而窄行施肥带的土壤氨挥发在施肥后持续约1个月. 与CK相比,控释尿素表施(0 cm)处理不仅大幅度地提高了窄行施肥带的氨挥发损失量,同时也显著增加了玉米种植带和宽行非施肥带的氨挥发损失量. 不同深度施肥处理全生育期土壤氨挥发损失总量差异较大,为3.1～25.5 kg N·hm^-2,占施氮量的1.7%～14.2%.其中控释尿素条施10、15和20 cm深度处理的全生育期土壤氨挥发损失总量相差不大,分别较表施(0 cm)和浅施(5 cm)处理显著降低了85.9%～87.8%和67.0%～71.6%. 在一定范围内增加控释尿素条施深度有利于提高鲜穗产量、植株氮积累量以及氮肥偏生产力、氮肥农学利用率和氮肥表观利用率,各指标均以15 cm深度处理最高. 综上所述,控释尿素合理深施可以显著降低氨挥发损失,提高鲜穗产量和氮肥利用效率,本研究条件下控释尿素的最适宜施用深度为15 cm.     

Molecular Modeling and docking of Wheat Hydroquinone Glucosyl transferase by using Hydroquinone,Phenyl phosphorodiamate and n-(n butyl) Phosphorothiocic Triamide as Inhibitors

In agriculture high urease activity during urea fertilization causes substantial environmental and economical problems by releasing abnormally large amount of ammonia into the atmosphere which leads to plant damage as well as ammonia toxicity. All over the world, urea is the most widely applied nitrogen fertilizer. Due to the action of enzyme urease; urea nitrogen is lost as volatile ammonia. For efficient use of nitrogen fertilizer, urease inhibitor along with the urea fertilizer is one of the best promising strategies. Urease inhibitors also provide an insight in understanding the mechanism of enzyme catalyzed reaction, the role of various amino acids in catalytic activity present at the active site of enzyme and the importance of nickel to this metallo enzyme. By keeping it in view, the present study was designed to dock three urease inhibitors namely Hydroquinone (HQ), Phenyl Phosphorodiamate (PPD) and N-(n-butyl) Phosphorothiocic triamide (NBPT) against Hydroquinone glucosyltransferase using molecular docking approach. The 3D structure of Hydroquinone glucosyltransferase was predicted using homology modeling approach and quality of the structure was assured using Ramachandran plot. This study revealed important interactions among the urease inhibitors and Hydroquinone glucosyltransferase. Thus, it can be inferred that these inhibitors may serve as future anti toxic constituent against plant toxins.     

Hydroponics versus field lysimeter studies of urea, ammonium and nitrate uptake by oilseed rape(Brassica napus L.)

N-fertilizer use efficiencies are affected by their chemical composition and suffer from potential N-losses by volatilization. In a field lysimeter experiment, (15)N-labelled fertilizers were used to follow N uptake by Brassica napus L. and assess N-losses by volatilization. Use of urea with NBPT (urease inhibitor) showed the best efficiency with the lowest N losses (8% of N applied compared with 25% with urea alone). Plants receiving ammonium sulphate, had similar yield achieved through a better N mobilization from vegetative tissues to the seeds, despite a lower N uptake resulting from a higher volatilization (43% of applied N). Amounts of (15)N in the plant were also higher when plants were fertilized with ammonium nitrate but N-losses reached 23% of applied N. In parallel, hydroponic experiments showed a deleterious effect of ammonium and urea on the growth of oilseed rape. This was alleviated by the nitrate supply, which was preferentially taken up. B. napus was also characterized by a very low potential for urea uptake. BnDUR3 and BnAMT1, encoding urea and ammonium transporters, were up-regulated by urea, suggesting that urea-grown plants suffered from nitrogen deficiency. The results also suggested a role for nitrate as a signal for the expression of BnDUR3, in addition to its role as a major nutrient. Overall, the results of the hydroponic study showed that urea itself does not contribute significantly to the N nutrition of oilseed rape. Moreover, it may contribute indirectly since a better use efficiency for urea fertilizer, which was further increased by the application of a urease inhibitor, was observed in the lysimeter study.     

控释肥料与普通氮肥混施对春白菜产量、品质和氮素损失的影响

在京郊露地生产条件下,研究了控释肥料与速效化肥混配施用对春白菜产量、品质、氨挥发、土壤硝态氮累积和淋失的影响.结果表明：与习惯施肥处理（施N 300 kg·hm^-2）相比,控释肥料与普通化肥按纯氮比2∶1混配施用（共施N 150 kg·hm^-2）没有造成白菜减产,并显著降低了菜叶中硝酸盐和有机酸含量;与半量施肥处理(施N 150 kg·hm^-2)相比,控释肥与化肥混施处理产量和叶片硝酸盐含量无显著差异.控释肥与化肥混施处理提高了白菜氮肥利用率,减少了N₃-N淋失量和氨挥发总量.白菜收获后,控释肥与化肥混施处理在20～40、60～80、80～100 cm土层的NO₃^--N含量显著低于习惯施肥处理.     

控失尿素对稻田氨挥发、氮素转运及利用效率的影响

通过田间试验,以普通尿素分次施用处理(CU)为对照,研究了控失尿素分次施用(LCUS)和一次施用(LCUB)对水稻田土壤氨挥发特征、水稻氮素营养状况、稻谷产量及氮肥利用效率的影响. 结果表明: 普通尿素分次施用、控失尿素分次施用和控失尿素一次施用条件下,生育期氨挥发总量占总施氮量的比例分别为15.8%、13.4%和19.7%. 与普通尿素分次施用处理相比,控失尿素分次施用处理可降低土壤氨挥发损失量4.4 kg N·hm^-2,降幅达18.0%,而控失尿素一次施用处理稻田土壤氨挥发总量却增加了7.2 kg N·hm^-2,增幅达24.7%. 与普通尿素分次施用处理相比,控失尿素分次施用处理的水稻叶片叶绿素、籽粒和茎叶氮含量与氮素积累量、稻谷产量均有不同程度提高,氮肥利用率显著提高了7.6%,但氮素转运量、转运率和对穗氮贡献率均显著降低,而控失尿素一次施用处理的水稻叶片叶绿素、籽粒和茎叶氮含量与氮素积累量以及氮肥利用率均显著降低,氮素转运量、转运率、对穗氮贡献率以及稻谷产量无显著差异. 综上所述,控失尿素分次施用处理可以在保证稻谷稳产的同时,有效降低稻田土壤氨挥发损失,改善植株氮素营养状况,显著提高氮肥利用效率.     

几种控释氮肥减少氨挥发的效果及影响因素研究

采用“静态吸收法”和“土柱淋溶法”、室内模拟试验,研究几种控释氮肥施入土壤后的氨挥发损失情况、N溶出速率、土壤脲酶活性及pH值变化的关系．结果表明,施氮450mg·kg^-1土时,3种控释氮肥氨挥发损失氮总量分别比普通尿素减少49．7％、28．0％和71．2％;施氮600mg·kg^-1土时,3种控释氮肥氨挥发损失氮总量分别比普通尿素减少34．6％、12．3％和69．9％．控释氮肥能显著降低土壤氨挥发量,减少因施肥而引起的大气环境污染．控释氮肥氨挥发量与不同氮肥引起的土壤脲酶活性、pH值、土壤中氮溶出速率密切相关．土壤的氨挥发总量与肥料在土壤中溶出总量的相关系数达到0．9533,在肥料施入的前期土壤氨挥发量同土壤脲酶活性、pH值的相关系数达到0．9533和0．9908。     

育秧箱全量施肥对水稻产量和氮素流失的影响

采用育秧箱全量施肥技术,通过2年田间小区试验,研究中量控释氮肥(80 kg N·hm-2)、高量控释氮肥(120kgN·hm-2)和常规施肥(300 kg N·hm-2)处理对水稻产量和氮素流失的影响.结果表明:与常规施肥相比,高量控释氮肥处理的水稻产量未显著降低.常规施肥处理2年平均氮素利用率为33.2％,中量和高量控释氮肥处理的平均氮素利用率分别比常规施肥处理提高26.2％和20.7％.常规施肥处理田面水的总氮含量在施肥后1～3d达最大值,中量和高量控释氮肥处理的高峰期为施肥后7～9d,全生育期内,中量和高量控释氮肥处理田面水的总氮含量均显著低于常规施肥处理.常规施肥处理的氮素渗漏流失主要在分蘖期,中量和高量控释氮肥处理的氮素渗漏流失后移至分蘖-开花期.各处理硝态氮流失量占总氮流失量的59.7％～64.2％,高量控释氮肥处理的总氮净流失量比常规施肥处理减少51.8％.     

施肥对巢湖流域稻季氨挥发损失的影响

采用通气法对巢湖流域稻季土壤氨挥发原位监测,研究了不同施肥量及秸秆还田处理对稻季氨挥发的影响。结果表明,氨挥发峰值发生在施肥后的第1-3 天,氨挥发损失主要集中于施肥后的1周。2010年整个稻季氨挥发净损失量为7.22-14.20 kg/hm²,占氮肥施用量的4.59%-6.64%,基肥期是主要的氨挥发时期,约占总氨挥发量的60%,穗肥期氨挥发总损失量最小。常规施肥处理氨挥发总损失量最大,与常规施肥相比,优化施肥、减量化施肥均能减少稻田土壤氨挥发损失1%-2%,氮磷肥减量同时秸秆还田处理氨挥发量最小,其总氨挥发量占常规处理的54%。施肥后的1-2d内田面水中的NH₄⁺-N浓度达到最大值,且各施肥处理的氨挥发量与同期田面水中的NH₄⁺-N浓度呈线性正相关。结合经济效益和环境效应分析发现,秸秆还田处理可减少氨挥发损失,同时获得较高的经济效益,适宜在巢湖流域水稻季推广。