Effect of urea pellet size and dicyandiamide on residual ammonium in field microplots

Abstract

Nitrification of urea can be slowed by adding a nitrification inhibitor or by fertilizer localization. The purpose of this research was to compare the effects of urea pellet size (0.01, 0.1, and 1.0 g) and level of dicyandiamide (DCD) addition (0, 1, 2, 5, and 10% of N as DCD‐N) on residual ammonium in field microplots. Trials were conducted at ten locations in North Dakota during 1988 and 1989. Adding DCD to 0.01 g urea pellets slowed nitrification at all locations and the lower rates of DCD (1–2% of N as DCD‐N) often performed as well as higher rates. Increasing urea pellet size to 1.0 g was more effective in inhibiting nitrification than adding DCD to 0.01 g pellets. Increased pellet size plus addition of DCD led to a very slow nitrification. A 1.0 g urea pellet containing 1–2% of N as DCD‐N should be a practical fertilizer formulation where a very slow nitrification is required.     

Evaluation of Two Products Recently Introduced as Nitrification Inhibitors

This study compared the relative effectiveness of two products recently introduced as nitrification inhibitors with other materials used to inhibit nitrification. Four soils were treated with 0, 0.2, 1, 5, and 25 mg kg^?1 of nitrapyrin (NP), a new microencapsulated nitrapyrin product (ENP), dicyandiamide (DCD), a new maleic-itaconic polymer product (MIP), and ammonium thiosulfate (ATS). The soils were also treated with 200 mg N kg^?1 as urea, and percent inhibition of nitrification determined after 2 or 4 weeks of incubation. After 4 weeks, similar levels of nitrification inhibition were provided by 1 mg kg^?1 of NP (72%), 5 mg kg^?1 of ENP (79%), and 25 mg kg^?1 of DCD (73%), averaged across soil. After 4 weeks with a sandy soil, the highest rate of MIP and ATS provided 15 and 36% inhibition, respectively. MIP and ATS were ineffective at inhibiting nitrification when added to the other three soils.

Abbreviations: ATS: ammonium thiosulfate; DCD: dicyandiamide; ENP: encapsulated nitrapyrin; MIP: maleic-itaconic polymer; NP: nitrapyrin; UAN: urea-ammonium nitrate liquid fertilizer     

Dicyandiamide (DCD) research in agriculture in the mid‐Atlantic region

Abstract

Numerous experiments have been conducted in Maryland and Pennsylvania since 1981 to determine if adding the nitrification inhibitor dicyandiamide (DCD) to an ammonium‐containing or producing N fertilizer source would increase the efficiency of that source with turfgrass, wheat, or corn. Greater yields per unit of fertilizer N were attained in three of eight experiments with wheat when DCD was included with an early spring application of N as urea or UAN. There was no significant beneficial effect of DCD on turf clipping yields or color in the 3 years of the turf study or on corn grain yields in the 22 field comparisons of N fertilizer with and without DCD. In five of the 22 comparisons with corn, there was a significantly lower grain yield with DCD than when it was not included. In three of these five cases, it was hypothesized that the lower yields with DCD were due to increased NH₃ volatilization from urea or urea‐ammonium nitrate solutions containing DCD that were surface‐applied to no‐till corn. It was concluded that there was little likelihood that the inclusion of a nitrification inhibitor such as DCD with N fertilizer would increase N fertilizer efficiency with corn or turf on the predominantly well‐drained silt loam soils in the two states.     

Can We Reduce Rainfed Maize (Zea mays L.) Nitrogenous Fertilizer Application Rate with Addition of Nitrapyrin?

Application of nitrification inhibitor has potential to increase soil nitrogen (N) retention throughout the growing season and finally increase corn (Zea mays L.) yield. During the 2012–2014 growing seasons, on-farm field trials were conducted to determine the effects of nitrapyrin (Instinct) with two N sources, urea and urea ammonium nitrate, at two rates, 85% and 100% of recommended N, and side-dress on grain yield and soil inorganic N availability in the Red River Valley of the North Dakota. Preplant urea N at 100% recorded the greatest yield in 2 out of 3 years. At late sampling, the greatest soil inorganic N was observed with side-dress urea ammonium nitrate at 100% within 0–30 cm (last 2 years). For spring fertilizer N management, addition of nitrapyrin had no effect on yield and inconsistent effect on soil N availability. Our results suggest that fertilizer N management should be evaluated on a local scale and consider annual variability in weather.     

Effects of Fertilizer Additives on Ammonia Loss after Surface Application of Urea–Ammonium Nitrate Fertilizer

The purpose of this study was to measure the effect of additives on ammonia loss when used with urea–ammonium nitrate fertilizer (UAN). The fertilizer additives were ammonium thiosulfate (ATS), calcium thiosulfate (CaTS), N-(N-butyl) thiophosphoric triamide (Agrotain, AG), AG + CaTS, or a maleic-itaconic copolymer (Nutrisphere-N, NSN). Four greenhouse studies were conducted, with small fertilizer droplets applied to bare soil, large fertilizer droplets applied to bare soil, small fertilizer droplets applied to soil with 50% straw cover, and large fertilizer droplets applied to soil with 50% straw cover. Ammonia volatilizing from the soil surface was trapped in phosphoric acid and determined by steam distillation. Averaged across all four experiments, the percentage reductions of ammonia loss after 14 days, compared to unamended UAN, were 40% for UAN + ATS, 40% for UAN + CaTS, 51% for UAN + AG, 65% for UAN + AG + CaTS, and 11% for UAN + NSN.     

Laboratory evaluation of dicyandiamide as a soil nitrification inhibitor

Abstract

Laboratory studies to evaluate dicyandiamide (DCD) as a soil nitrification inhibitor showed that it is considerably more effective than several compounds that have been patented or proposed as fertilizer amendments for retarding nitrification of fertilizer nitrogen (N) in soil, but is considerably less effective than 2‐ethynylpyridine, nitrapyrin (N‐Serve), etridiazole (Dwell), 3‐methylpyrazole‐l‐carboxamide (MPC), or 4‐amino‐l,2,4‐triazole (ATC). Other findings in studies reported were as follows: a) DCD is more effective for inhibiting nitrification of ammonium‐N than of urea‐N; b) the effectiveness of DCD as a nitrification inhibitor is markedly affected by soil temperature and soil type and is limited by the susceptibility of DCD to leaching; c) DCD has very little, if any, effect on urea hydrolysis, denitrification, or seed germination in soil; d) products of DCD decomposition in soil (guanylurea and guanidine) have little, if any, effect on nitrification compared with DCD; e) in the absence of leaching, the persistence of the inhibitory effect of DCD on nitrification decreases with increase in soil temperature from 10 to 30°C, but the inhibitory effect of 50 μg DCD g^‐1 soil is substantial even after incubation of DCD‐treated soils at 20 or 30°C for 24 weeks.     

不同氮肥在石灰性潮土中的转化及ATS对尿素氮转化的调控效应

根据氮肥施入土壤后的转化特性进行氮肥的高效调控和管理是提高氮肥利用效率、缓解氮肥污染的重要措施。为探究不同氮肥在石灰性潮土中的转化特性差异及硫代硫酸铵（ammonium thiosulfate，ATS）作为氮肥调控剂对尿素氮转化的影响，该研究采用室内土壤培养（土壤水分含量为田间持水量的60%，温度25 ℃）试验方法，以尿素、硫酸铵、氯化铵和ATS作为供试肥料，比较4种氮肥施入石灰性潮土后的转化特性差异，并以ATS作为氮素调控剂，以单施尿素作为对照，探究尿素配施不同用量ATS对尿素氮转化的影响。结果表明，4种供试氮肥在石灰性潮土中的转化过程明显不同。尿素在石灰性潮土中的水解速率最快，硝化作用强度也最高，硫酸铵其次；氯化铵由于Cl^-的硝化抑制作用，土壤表观硝化率在7～21 d显著低于尿素和硫酸铵（P＜0.05）；ATS施入土壤后，NH₄⁺-N转化为NO₂^--N的速率最高，而NO₂^--N转化为NO₃^--N的速率最低，NH₄⁺-N在土壤中的存留时间最长，出现峰值之后也一直保持最高的含量，表观硝化率最低。将ATS作为氮素调控剂与尿素配合施用，当其用量在60 mg/kg（含S量）以上时，既表现出了明显的抑制尿素水解的作用效果，也表现出了显著的硝化抑制作用（ P <0.05），且随着ATS用量的增加，抑制效应明显增强。这对于减少氮素损失，提高氮肥利用效率具有积极意义。但供试4种氮肥施入土壤后均出现了亚硝酸盐的累积，其中ATS处理的累积量显著高于尿素、硫酸铵和氯化铵（P＜0.05），累积持续时间也最长。ATS作为氮素调控剂调控氮素转化，也出现了类似的结果，且随着ATS用量增加，亚硝酸盐在土壤中存留时间明显延长，含量和峰值明显提高，出现峰值的时间也明显延后。     

Calcium chloride and ammonium thiosulfate as ammonia volatilization inhibitors for urea fertilizers

Abstract

Surface‐applied urea fertilizers are susceptible to hydrolysis and loss of nitrogen (N) through ammonium (NH₃) volatilization when conditions favorable for these processes exist. Calcium chloride (CaCl₂) and ammonium thiosulfate (ATS) may inhibit urease activity and reduce NH₃ volatilization when mixed with urea fertilizers. The objective of this study was to evaluate the effectiveness of CaCl₂ and ATS as urea‐N loss inhibitors for contrasting soil types and varying environmental conditions. The proposed inhibitors were evaluated in the laboratory using a closed, dynamic air flow system to directly measure NH₃ volatilization. The initial effects of CaCl₂ on ammonia volatilization were more accentuated on an acid Lufkin fine sandy loam than a calcareous Ships clay, but during volatilization periods of ≥ 192 h, cumulative N loss was reduced more on the Ships soil than the Lufkin soil. Calcium chloride delayed the commencement of NH₃ volatilization following fertilizer application and reduced the maximum N loss rate. Ammonium thiosulfate was more effective on the Lufkin soil than the Ships soil. For the Lufkin soil, ATS reduced cumulative urea‐N loss by 11% after a volatilization period of 192 h. A 20% (v/v) addition of ATS to urea ammonium nitrate (UAN) was most effective on the coarse textured Lufkin soil whereas a 5% addition was more effective on the fine textured, Ships soil. Rapid soil drying following fertilizer application substantially reduced NH₃ volatilization from both soils and also increased the effectiveness of CaCl₂ but not ATS. Calcium chloride and ATS may function as limited NH₃ volatilization inhibitors, but their effectiveness is dependent on soil properties and environmental conditions.     

不同硝化抑制剂组合对铵态氮在黑土和褐土中转化的影响

【目的】添加硝化抑制剂和氮肥增效剂是提高氮肥利用率的有效方法。研究不同硝化抑制剂和氮肥增效剂组合对不同性质土壤中铵态氮转化特征的影响,为科学合理选择抑制剂提供理论依据。【方法】供试生化抑制剂包括2-氯-6 (三氯甲基) -吡啶 (Nitrapyrin,CP)、3,4-二甲基吡唑磷酸盐 (DMPP)、1-甲氨甲酰-3-甲基吡唑 (CMP)、3-甲基吡唑 (MP)、2-氨基-4-氯-6-甲基嘧啶 (AM)、N-guard、二氰二胺 (DCD)。供试土壤为黑土和褐土,以氯化铵为氮肥,按照常用量添加各生化抑制剂制备稳定性肥料,用于室内恒温、恒湿土壤培养试验。试验设不施肥 (CK)、氯化铵 (N)、N + CP、N + CP + AM、N + CP + DCD、N + CP + N-guard、N + CP + DMPP、N + CP + CMP、N + CP + MP等9个处理。在培养第1、4、7、11、15、22、30、45、60、75、90、105、120天取土样,测定土壤含水量、土壤NH₄+-N和NO₃–-N含量,并计算硝化抑制率。【结果】在黑土和褐土两种类型土壤中,铵态氮转化特征具有显著差异,在弱酸性黑土中硝化反应速率显著低于碱性褐土。在黑土中,不同硝化抑制剂组合N + CP、N + CP + N-guard、N + CP + DMPP、N + CP + DCD、N + CP + CMP、N + CP + AM、N + CP + MP都表现出较好的硝化抑制效果,可以维持黑土中较高的铵态氮含量超过4个月以上。其中N + CP、N + CP + DCD、N + CP + N-guard处理在120天时,其硝化抑制率为37%～40%。而N + CP + AM、N + CP + MP、N + CP + DMPP为32%～36%,N + CP + CMP为26%。在褐土中,N + CP + DCD组合硝化抑制效果最大,在培养120天,其硝化抑制率为20%;其次是N + CP、N + CP + AM,其硝化抑制率在培养第105天时分别为23%、12%,在培养第90天时分别为63%、60%;N + CP + N-guard、N + CP + DMPP、N + CP + MP、N + CP + CMP在培养第75天时硝化抑制率分别为43%、42%、37%、35%,有效硝化抑制作用时间可维持75天左右。【结论】在黑土和褐土2种不同类型土壤中施用氯化铵氮肥,应添加专一硝化抑制剂或组合制成高效稳定性铵态氮肥。在湿润地区pH较低的酸性土壤上,例如黑土,适宜的硝化抑制剂较多,其中N + CP或N + CP + N-guard、N + CP + DCD组合的硝化抑制效果显著且持续时间长。在干旱半干旱的碱性土壤上,例如褐土,N + CP + DCD组合的硝化抑制效果和持续时间优于其他组合,可用于褐土上施用的高效稳定性氯化铵氮肥的生产。     

Effects of nitrification inhibitors on transformations of urea nitrogen in soils

The effects of three patented nitrification inhibitors on transformations of urea N in soils were studied by determining the effects of these compounds (10 μg/g of soil) on urea hydrolysis, ammonia volatilization. and production of ammonium, nitrite, and nitrate in soils incubated under aerobic conditions (30°C, 60% WHC) after treatment with urea (400 μg of urea N/g of soil). The inhibitors used (N-Serve, ATC, and CL-1580) had little, if any, effect on urea hydrolysis, but they retarded nitrification of the ammonium formed by urea hydrolysis and increased gaseous loss of urea N as ammonia. They also decreased the amount of (urea + exchangeable ammonium + nitrite + nitrate) — N found in urea-treated soils after various times.Two of the soils used accumulated substantial amounts of nitrite(> 160 μg of nitrite N/g of soil) when incubated under aerobic conditions after treatment with urea. Addition of nitrification inhibitors to these soils eliminated or substantially reduced nitrite accumulation and greatly retarded nitrate formation, but had little, if any, effect on the recovery of urea N as (urea + exchangeable ammonium + nitrite + nitrate + ammonia) — N after various times. This finding and other observations reported indicate that the “nitrogen deficits” observed in studies of urea N transformations in soils may not largely be due to gaseous loss of urea N through chemodenitrification and are at least partly due to volatilization and fixation of the ammonium formed by urea hydrolysis in soils. The work reported also indicates that N-Serve and other nitrification inhibitors may prove useful for reduction of the nitrite toxicity problems associated with the use of urea as a fertilizer but that application of such inhibitors in conjunction with fertilizer urea, when surface applied, may promote gaseous loss of urea N as ammonia.     

用于黑土的稳定性氯化铵的适宜硝化抑制剂和氮肥增效剂组合

【目的】本文研究添加不同种类硝化抑制剂的高效稳定性氯化铵氮肥在黑土中的施用效果，旨在筛选出适合旱作黑土的高效稳定性氯化铵态氮肥。【方法】在氯化铵中分别添加硝化抑制剂3,4-二甲基吡唑磷酸盐 (DMPP)、双氰胺 (DCD)、2-氯-6-三甲基吡啶 (Nitrapyrin，CP)、氨保护剂 (N-GD) 和1种氮肥增效剂 (HFJ) 及其组合，制成9种稳定性氯化铵氮肥。以不施氮肥 (CK) 和施普通氯化铵 (CK-N) 为对照，以9种稳定性氯化铵为处理进行了等氮量盆栽试验。在玉米苗期、大喇叭口期、灌浆期和成熟期测定了土壤中铵态氮和硝态氮含量，在玉米成熟期测定植株生物量、籽粒产量和氮素含量，计算铵态氮肥的表观硝化率、硝化抑制率、氮肥农学效率、氮肥偏生产力。【结果】1) 与CK-N处理相比，9个处理均显著提高玉米的产量，HFJ的效果均为最显著，可增加玉米籽粒产量3.99倍，提高氮肥吸收利用率4.98倍，显著高于8个硝化抑制剂处理 (P < 0.05)。CP + DMPP和CP + DCD处理提高玉米籽粒产量1.90～2.11倍，两个处理之间无显著差异；CP + DMPP玉米生物量显著高于CP处理，而与DMPP和DCD处理无显著差异；CP + DMPP玉米氮肥吸收利用率显著高于CP和DMPP处理，显著提高3.71倍 (P < 0.05)；2) CP + DMPP和CP + DCD土壤中铵态氮含量提高2.09～2.42倍，且显著高于CP、DMPP和DCD处理 (P < 0.05)，而硝态氮含量和土壤表观硝化率均显著降低24%和66%～68%，与CP和DCD处理存在显著差异 (P < 0.05)；苗期CP + DMPP和CP + DCD硝化抑制率高达23.9%～24.3%，显著高于CP和DCD (P < 0.05)。【结论】在黑土中，氯化铵中添加硝化抑制剂组合的硝化抑制率显著高于添加单一抑制剂，能够有效减缓土壤中铵态氮向硝态氮的转化，减少土壤中氮素损失，降低环境污染。CP + DMPP组合玉米的氮肥吸收利用率显著高于CP + DCD组合。氮肥增效剂HFJ显著增加玉米的氮素吸收量，提高氮肥利用率，从而使玉米获得高产并获得较高的收获指数和经济系数。因此，综合考虑产量和抑制硝化作用等因素，黑土区氯化铵作为玉米生产用氮肥时，建议首选添加氮肥增效剂HFJ来保证作物的高产和氮肥高利用率，也可以添加硝化抑制剂组合CP + DMPP，或者CP + DCD制备稳定性氯化铵来提高氯化铵的增产效果和氮肥利用率，减少氮素损失，降低环境污染。     

改性尿素硝酸铵溶液调控氮素挥发和淋溶的研究

为了提高肥料的利用率,以尿素硝酸铵溶液为原料、聚氨酸为保护剂,复合抑制剂NBPT(N-丁基硫代磷酰三胺)和DMPP(3,4-二甲基吡唑磷酸盐)为材料,开发出改性尿素硝酸铵溶液(YUL1和YUL2),研究其对华北平原夏玉米追肥过程中的氨挥发和淋溶损失的调控效果。田间试验设置6个处理:不施氮肥(CK)、农民习惯追施尿素(CN)、优化追施尿素(CNU)、优化追施尿素硝酸铵溶液(UAN)、优化追施改性尿素硝酸铵溶液(YUL1)和优化追施改性尿素硝酸铵溶液(YUL2)。采用扫描电镜和能谱仪分析相关指标变化,在夏玉米喇叭口期追施氮肥后15d内进行田间原位连续动态观测氨挥发和土壤铵态氮和硝态氮变化,并在玉米成熟期测定产量,计算经济效益。结果表明,改性尿素硝酸铵溶液清澈无杂质,流延后成膜表面光滑、致密,抑制剂在膜表面分布均匀;能谱测试膜层表面磷硫含量增高,证明复合抑制剂与尿素硝酸铵溶液达到有效融合。在同等优化施氮量下:与CNU相比, YUL1氨挥发总量显著降低19.3%, YUL2增加9.6%;与UAN相比, YUL1、YUL2分别显著降低57.3%和42.0%。与其他施氮处理相比, YUL1和YUL2夏玉米季生长中后期0～20 cm土层依然保持相对较高的氮素含量水平,夏玉米收获后土壤硝态氮含量分别比CNU高46.0%和43.4%,比UAN高45.6%和44.7%;180～200cm土层硝态氮含量显著低于其他处理。在保证产量和净收益的同时,改性尿素硝酸铵肥料显著降低了氮素的氨挥发和淋溶损失浓度,尿酶抑制剂含量相对较高的YUL1抑制氨挥发的效果更好,硝化抑制剂含量相对高的YUL2硝态氮向下淋失的风险更小。     

Response of Kentucky bluegrass turf to fertilizers containing dicyandiamide

Abstract

Nitrogen fertilization is of major importance in maintaining turfgrass stands. Although rates and sources of N may vary on different turfgrass areas, efficient utilization of N applications is always important. This research was conducted in the field to determine the value of dicyandiamide (DCD) as a nitrification inhibitor and as a slow‐release N source in turfgrass fertilization. The inhibitory effect was studied by applying ammonium sulfate (AS), urea, and a complete fertilizer alone and with 10 and/or 15% of the N replaced with DCD‐N to stands of Kentucky bluegrass. Single and split rates totaling up to 196 kgN/ha/yr were used. Soil NO₃‐N and NH₄‐N analyses sometimes indicated decreased nitrification; however, turfgrass yield and color were essentially unaffected by these rates of DCD. To assess the slow‐release effect of DCD, various ratios of AS‐N or urea‐N to DCD‐N were used to fertilize turf in two experiments. Initial response decreased as the proportion of DCD‐N increased, and in one experiment, a residual effect was noted a year after application when DCD comprised 80 or 100% of the N. Severe, but short‐lived, phytotoxicity from DCD was noted in the other experiment when more than 40% of the N was from DCD. Under the conditions of this research, DCD appeared to have little value in increasing the efficiency of N fertilization.     

双氰胺对不同质地红壤中碳酸氢铵的硝化抑制作用研究

通过室内好气培养试验,研究了双氰胺(DCD)对施入不同质地红壤中碳酸氢铵的硝化抑制作用。结果表明,添加DCD明显提高了相应处理的铵态氮含量,降低了硝态氮含量。无论加入DCD与否,砂壤土中碳酸氢铵的硝化时间大约都需7周;轻粘土中碳酸氢铵的硝化时间为35.d,加入硝化抑制剂后硝化时间可延长2周;而中壤土中至培养结束时仍有较高的铵态氮,故铵的硝化时间有待进一步研究。DCD对碳酸氢铵的硝化抑制效果中壤土优于砂壤土、轻粘土;在砂壤土和轻粘土中,DCD对低浓度铵态氮处理的硝化抑制效果好;而在中壤土中对高浓度的抑制效果好。     

3,4二甲基吡唑磷酸盐和双氰胺在黑钙土中对尿素氮转化的作用效果

采用室内培养试验,以普通尿素为对照,研究双氰胺(DCD)、3,4-二甲基吡唑磷酸盐(DMPP)和缓释尿素在东北黑钙土中对尿素氮转化的作用效果。结果表明,缓释尿素对尿素水解有一定的限制作用。0.5%DMPP对抑制氨氧化作用效果最好,保持低表观硝化率时间最长,硝化抑制率最高,有效作用时间最长,最佳有效抑制时间为42 d,有效作用时间可达63 d,显著好于2%DCD;2%DCD也有显著的抑制效果,保持低表观硝化率时间较长,硝化抑制率较高,最佳抑制时间为35 d,有效作用时间超过56 d,缓释尿素最佳作用时间为7 d,有效作用时间可达35 d。作用效果为添加0.5%DMPP+尿素添加2%DCD+尿素缓释尿素普通尿素。     

Potency of nitrification inhibitors following their repeated application to soil

Summary Nitrification inhibitors were applied to a field experiment on loamy sand soil each autumn for 4 years, immediately prior to sowing winter cereals. Laboratory experiments demonstrated that repeated application of the inhibitor dicyandiamide (DCD) to a soil had little effect either on the rate of DCD decomposition or the ability of DCD to inhibit nitrification. Repeated field application of the inhibitors DCD, nitrapyrin or etridiazole resulted in increased sensitivity of ammonium-oxidizing bacteria to nitrapyrin or etridiazole, but not to DCD. The rate of decomposition of etridiazole was unaffected by four annual applications of this inhibitor, but decomposition of nitrapyrin was somewhat slower in soil that had received nitrapyrin annually for 4 years than in soil that had never been treated with an inhibitor.     

几种新型氮肥对叶菜硝酸盐累积和土壤硝态氮淋洗的影响

应用土柱模拟试验的方法,研究了在高肥力菜田土壤条件下,施用几种新型氮肥对两茬叶菜硝酸盐积累和土壤硝态氮淋洗的影响。结果表明,在高肥力菜田土壤上,施用几种新型氮肥都未能明显提高第一茬油菜的生物量,硫硝铵（A SN）却降低了生物量,而第二茬菠菜不施肥处理生物量下降。尿素＋硝化抑制剂DM PP（En tec46）、尿素＋硝化抑制剂DCD（U＋DCD）和有机无机复混肥（OIF）3种氮肥显著降低了油菜硝酸盐含量。尿素＋玉米秸秆（U＋M S）和硫硝铵＋硝化抑制剂DM PP（En tec26）减少了土壤NO3^--N的向下淋洗,而尿素＋保水剂（U＋SAP）增加土壤NO3^--N的向下淋洗。     

三种硝化抑制剂抑制土壤硝化作用比较及用量研究

【目的】硝化抑制剂是调控土壤氮素转化与硝化作用微生物群落结构的有效途径。本文通过室内模拟试验对3种硝化抑制剂在不同剂量下的硝化抑制效果进行研究,旨在筛选出效果最佳的剂型与剂量,为石灰性土壤硝化抑制剂的合理应用提供依据。 【方法】培养试验在生长箱内进行,25℃黑暗条件培养;盆栽试验在温室内进行。供试硝化抑制剂为双氰胺（DCD）、3,4-二甲基吡唑磷酸盐（DMPP）和2-氯-6-三氯甲基吡啶（Nitrapyrin）,DCD和DMPP用量均设定为纯氮（N）量的0（CK）、1.0%、2.0%、3.0%、3.5%、4.0%、4.5%、5.0%、6.0%和7.0%;Nitrapyrin用量分别为纯氮量的0、0.1%、0.125%、0.2%、0.25%、0.3%、0.35%、0.4%、0.45%和0.5%,三种硝化抑制剂均设10个水平,每个水平3次重复。盆栽试验氮加入量为每公斤风干土0.50 g,三种硝化抑制剂用量分别为纯氮用量的5%、1%、0.648%。调查比较了三者的硝化抑制效果及对土壤氮素转化的影响及其对小青菜鲜重的生物学效应;采用变性梯度凝胶电泳（DGGE）法分析了不同硝化抑制剂对土壤AOA、AOB群落结构的影响。 【结果】DCD、DMPP、Nitrapyrin均可显著抑制土壤硝化作用（P＜0.05）,各硝化抑制剂处理土壤的NH₄+-N含量分别较对照提高了46.2~256.1 mg/kg、291.8~376.7 mg/kg、3.68~372.9 mg/kg。DCD与DMPP处理的硝化抑制率分别为49.3%~79.4%和96.4%~99.4%,DCD表现出明显的剂量效应,但DMPP在1%~7%浓度范围内的剂量效应不明显。Nitrapyrin在0.1%~0.2%浓度范围内有明显的剂量效应。0.25%~0.5% Nitrapyrin的硝化抑制率为98.9%~99.9%,其硝化抑制效果与DMPP处理相同。DCD、DMPP、Nitrapyrin处理的小青菜地上部分鲜重分别比氮肥处理（ASN）提高了12.7%、11.1%、17.6%。施用硝化抑制剂可改变土壤AOA和AOB群落结构,且对AOA群落结构的影响大于AOB,不同硝化抑制剂之间对AOA和AOB群落结构的影响无差异。 【结论】3种硝化抑制剂的硝化抑制效果表现为Nitrapyrin≥DMPP>DCD,均对AOA与AOB群落结构产生明显影响。各硝化抑制剂处理均可提高小青菜地上部鲜重、叶片Vc含量及可显著提高小青菜叶片氨基酸含量（P＜0.05）。综合比较,Nitrapyrin硝化抑制效果好于DMPP,DCD效果最差,推荐用量为基于纯氮0.25%的Nitrapyrin添加量。     

Effect of the nitrification inhibitor nitrapyrin on the fate of nitrogen applied to a soil incubated under laboratory conditions

The aim of this study was to examine the effect of the nitrification inhibitor nitrapyrin on the fate and recovery of fertilizer nitrogen (N) and on N mineralization from soil organic sources. Intact soil cores were collected from a grassland field. Diammonium phosphate (DAP) and urea were applied as N sources. Cores were equilibrated at –5 kPa matric potential and incubated at 20 °C for 42 to 56 days. Changes in NH₄⁺‐N, accumulation of NO₃^–‐N, apparent recovery of applied N, and emission of N₂O (acetylene was used to block N₂O reductase) were examined during the study. A significant increase in NH₄⁺‐N released through mineralization was recorded when nitrapyrin was added to the control soil without N fertilizer application. In the soils to which N was added either as urea or DAP, 50–90 % of the applied N disappeared from the NH₄⁺‐N pool. Some of this N (8–16 %) accumulated as NO₃^–‐N, while a small proportion of N (1 %) escaped as N₂O. Addition of nitrapyrin resulted in a decrease and delay of NH₄⁺‐N disappearance, accumulation of much lower soil NO₃^–‐N contents, a substantial reduction in N₂O emissions, and a 30–40 % increase in the apparent recovery of added N. The study indicates that N recovery can be increased by using the nitrification inhibitor nitrapyrin in grassland soils at moisture condition close to field capacity.     

炭输入及生化调控对设施菜田土壤N_2O排放的影响

本研究以河北永清蔬菜基地设施菜田土壤为研究对象,控制温度(25±1)℃和土壤含水量(70%WFPS),采用静态培养方法,通过监测培养期间土壤N_2O排放通量、无机氮含量及土壤中酶活性的变化情况,研究炭输入及生化调控对设施菜田N_2O排放及氮素转化的影响。结果表明,土壤添加尿素后,N_2O排放峰值达到644.11μg N·kg~(-1)·d~(-1),添加双氰胺(DCD)和石灰氮(CaCN_2)的土壤N_2O排放峰值分别为101.47μg N·kg~(-1)·d~(-1)和36.74μg N·kg~(-1)·d~(-1),对于N_2O减排效果好,且能有效抑制亚硝态氮的产生;施用控释尿素、添加黑炭或有机肥能减少N_2O排放,而添加石灰氮闷棚显著增加了N_2O排放。控释尿素、秸秆、黑炭、DCD和CaCN_2均对铵态氮向硝态氮的转化有一定抑制作用,施加石灰氮或有机肥有助于减少硝态氮向亚硝态氮的转化。相关分析表明,土壤中硝态氮和亚硝态氮含量增加,有助于反硝化过程的进行,增加了N_2O排放的风险。