Effect of dicyandiamide on the form and recovery of 15N‐labeled urea in the delayed flood soil system

Abstract

Dicyandiamide (DCD) is a nitrification inhibitor that has been proposed for use in drill‐seeded rice. Immobilization of fertilizer NH₄ ⁺‐N by soil microorganisms under aerobic conditions has been found to be significantly enhanced in the presence of a nitrification inhibitor. The objective of this laboratory study was to determine if DCD significantly delayed nitrification of urea‐derived N, and if this enhanced immobilization of the fertilizer N in the delayed‐flood soil system inherent to dry‐seeded rice culture. Nitrogen‐15‐labeled urea solution, with and without DCD (1: 9 w/w N basis), was applied to a Crowley silt loam (Typic Albaqualf) and the soil was incubated for 10 weeks in the laboratory. The soil was maintained under nonflooded conditions for the first four weeks and then a flood was applied and maintained for the remaining six weeks of incubation. The use of DCD significantly slowed the nitrification of the fertilizer N during the four weeks of nonflooded incubation to cause the (urea + DCD)‐amended soil to have a 2.5 times higher fertilizer‐derived exchangeable NH₄+‐N concentration by the end of the fourth week. However, the higher exchangeable NH₄+‐N concentration had no significant effect on the amount of fertilizer N immobilized during this period. Immobilization of the fertilizer N appeared to level off during the nonflood period about the second week after application. After flooding, immobilization of fertilizer N resumed and was much greater in the (urea + DCD)‐amended soil that had the much higher fertilizer‐derived exchangeable NH₄ ⁺‐N concentration. Immobilization of fertilizer N appeared to obtain a maximum in the urea‐amended soil (18%) about two weeks after flooding and for the (urea + DCD)‐amended soil (28%) about four weeks after flooding.     

Effect of ammonium thilosulfate and dicyandiamide on residual ammonium in fertilizer bands

Abstract

Ammonium thiosulfate (ATS, 12–0–0–26S) and dicyandiamide (DCD, 66–0–0) are fertilizer products that also inhibit nitrification. It has also been proposed that ATS can improve the nitrification inhibition properties of DCD. The purpose of this research was to compare the effects of ATS, DCD, and ATS/DCD mixtures on the nitrification of banded urea solution or urea‐ammonium nitrate (UAN) under laboratory, field microplot, and field conditions. The laboratory study demonstrated that adding 8.7% (vol vol^‐1) ATS to a urea solution inhibited nitrification by 68%. Inhibition of nitrification was greater with ATS + DCD than with DCD alone. Some nitrite accumulated when ATS was added, but little or no nitrite accumulated when both ATS and DCD were present In field microplot studies, the addition of ATS to urea solution significantly (P ≤ 0.10) increased residual soil ammonium levels over urea alone at six of 11 trials. ATS was usually a less effective nitrification inhibitor than was DCD, and ATS + DCD outperformed DCD at only one of 11 trials. In all three field trials, adding ATS to banded UAN solution led to increased residual ammonium levels. Again, ATS was less effective than DCD or nitrapyrin as a nitrification inhibitor, and no ATS/DCD synergism was observed. It was concluded that the use of ATS as a sulfur fertilizer in fluid fertilizer bands can lead to measurable inhibition of nitrification, but ATS was not as reliable as DCD or nitrapyrin.     

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.     

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.     

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.     

Dicyandiamide (DCD) as a nitrification inhibitor for rice culture in the United States

Abstract

Efficient nitrogen (N) fertilizer management for paddy rice production is difficult because of potentially high N losses from denitrification, NH₃ volatilization, and leaching. The use of a nitrification inhibitor, by slowing the rate of nitrification of NH₄ ⁺‐N sources prior to flooding, offers the potential to reduce denitrification losses that occur after flooding. Dicyandiamide (DCD) is one such nitrification inhibitor. The objective of this series of studies was to evaluate DCD for its effectiveness as a nitrification inhibitor in paddy rice production across an array of soils, management systems, and climate conditions.

Studies were conducted on fine‐ and medium‐textured soils in Arkansas, California, Louisiana, Mississippi, and Texas. Dicyandiamide was coated onto or formulated with urea (7 or 10% of total N as DCD‐N) and applied either broadcast pre‐plant incorporated or broadcast as a topdress application prior to flooding at the 4‐ to 5‐leaf development stage of the rice plant. These treatments were compared with urea applied either pre‐plant incorporated or in multiple applications timed to the peak N demand periods of rice. An array of N rates were used to model the yield response to levels of N. Similar studies utilizing ¹⁵N‐enriched urea were also conducted.

The studies indicated that use of DCD delayed nitrification and tended to result in rice grain yield increases as compared with urea applied pre‐plant without DCD in drill‐seeded rice; however, proper application of urea in split applications gave more consistent results. In water‐seeded continuously flooded rice culture, use of DCD was advantageous only if the flood was delayed for more than 14 days after urea application. The ¹⁵N‐enriched studies indicated that highest N fertilizer recovery was associated with split topdress urea applications; however, addition of DCD resulted in increased immobilization of fertilizer N and release of soil N.     

Dicyandiamide increases the fertilizer N loss from an alkaline calcareous soil treated with <Superscript>15</Superscript>N-labelled urea under warm climate and under different crops

Using an alkaline calcareous soil, experiments were conducted to elucidate the effects of nitrification inhibitor dicyandiamide (DCD) on the fate of ¹⁵N-labelled urea applied to cotton, maize, and wheat under greenhouse conditions. Combined effects of DCD and two levels of wheat straw (applied to cotton) and of fertilizer application method (conventional broadcast vs. point injection in maize and wheat) on the recovery of the fertilizer N were also studied. High soil temperatures prevailed under cotton and maize, whereas the soil temperature was relatively moderate during the wheat growing season. The fertilizer N loss under cotton was lowest (44% of the applied) when urea was applied alone; the loss increased due to DCD (54%) or wheat straw (50–54%) and was highest (63–64%) when DCD and wheat straw were applied together. Under maize also, DCD increased the loss of the fertilizer N applied by the conventional method (51% without DCD vs. 66% with DCD) or by point injection (26% without DCD vs. 42% with DCD). With the conventional method under wheat, DCD had no effect on the fertilizer N loss (34–37% of the applied). The fertilizer N loss under wheat was least (16%) when urea solution was point-injected but increased (24–26%) due to DCD or/and when pH of the urea solution was reduced to 2. Besides, DCD significantly reduced the fertilizer N uptake and increased the fertilizer N immobilization in soil under cotton and maize. However, DCD applied in combination with a higher level of wheat straw significantly increased the cotton dry matter and N yields due to increased N availability from sources other than the fertilizer. The results suggested that the use of DCD may not be beneficial in alkaline calcareous soils and that point injection of urea solution without any amendment is more effective in conserving the fertilizer N as compared to the conventional broadcast method.     

Nitrification and utilization of fertilizer nitrogen by highbush blueberry

Nitrification rates and nitrogen (N) recovery by 3 year‐old highbush blueberry ( Vaccinium corymbosum L. cv. Bluecrop) were compared following applications of ammonium sulfate with or without the nitrification inhibitor dicyandiamide (DCD) on a sandy loam soil with pH 4.8. Ammonium sulfate solutions containing 7.9 grams N (10.2 atom % ¹⁵N), with or without 0.6 g DCD, were applied to the soil surface beneath bushes. Concentrations of fertilizer derived nitrate were significantly lower in DCD treated soils 2 weeks following application, but DCD had no effect on total nitrate levels or fertilizer derived nitrate later in the season. Uptake of fertilizer‐N by blueberry plants was observed by collecting fruit during the growing season and assessing N partitioning within whole plants at the end of the season using ¹⁵N as a label for fertilizer N. The DCD had no effect on fertilizer derived or total N levels in plants. Plants recovered an average of 3% of applied N by the end of the season.     

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。     

Effect of dicyandiamide on growth and nutrient uptake of cotton

Abstract

The nitrification inhibitor dicyandiamide (DCD) offers potential for improving efficiency of N applications to cotton grown on sandy soils of the southeastern Coastal Plain. Research has indicated that cotton is sensitive to DCD. The purpose of this greenhouse experiment was to investigate the effect of DCD on growth and nutrient uptake of DPL 90 cotton grown for 73 days in pots containing a typical Coastal Plain soil (Norfolk sandy loam, Typic Paleudult). Nitrogen (50 mg kg^‐1) as NaNO₃ or urea, and DCD (0, 2.5, 5, 10, 15 and 20 mg kg^‐1) were applied to the soil at first true leaf and plants were harvested 58 days later. Sodium nitrate increased leaf dry weight and total dry weight of plants 9.1 and 6.0%, respectively, over urea fertilized plants. Leaf area, dryweight, and stem dry weight were reduced linearly with DCD. Fertilization with urea increased concentrations of leaf P, K, and Mn and reduced the concentration of Mg in leaf tissue. Dicyandiamide increased leaf N, P, and K concentrations but reduced concentrations of Ca, Mg, and Mn. Uptake rates (μg^‐1 g^‐1 fresh root day^‐1) of Ca and Mg were increased 7.5 and 13.7%, respectively, with NaNO₃ vs. urea, while P uptake rate was 15.5% greater for urea‐fertilized plants vs. NaNO₃‐fertilized plants. Dicyandiamide reduced Ca and Mg uptake rates. Phosphorus uptake rates were increased by DCD when urea was the N source. The effects of DCD on cotton growth and nutrient uptake generally resulted from the compound itself and were not an indirect result of nitrification inhibition. Although significant reductions in plant growth did not occur unless DCD exceeded that normally applied with recommended N rates on this soil, these results suggest a need for caution when applying DCD to cotton grown on sandy soils.     

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。     

Dicyandiamide effects on nitrification and total inorganic soil nitrogen in sandy soils

Abstract

Inhibition of nitrification in soil results in a decreased ratio of nitrate‐nitrogen (NO₃‐N) to ammonium‐nitrogen (NH₄‐N). If the conditions for NO₃‐N loss by leaching or denitrification exist, nitrification inhibitors should increase concentrations of total inorganic soil nitrogen (N) (TISN) (NH₄‐N + NO₃‐N). This can then result in plants taking up more N and developing more crop yield or biomass. This study examined whether inhibition of nitrification by dicyandiamide (DCD) would result in increased concentrations of TISN under field conditions. The effects of DCD on soil N were evaluated in hyperthermic sandy soils planted to potato (Solanum tuberosum L., cv. Atlantic). Treatments were factorial combinations of N as ammonium nitrate (NH₄NO₃) at 67, 134, and 202 kg N ha^‐1 and DCD at 0, 5.6, and 11.2 kg DCD ha^‐1. Soil NH₄‐N, NO₃‐N, and TISN concentrations were determined for up to five potato growth stages at two locations for two years for a total of 16 determinations (cases), i.e., four were not determined. The N form ratio [NO₃‐N/(NH₄‐N + NO₃‐N] x 100 was decreased in 10 of 16 cases, indicating that nitrification was inhibited by DCD. With two of these 10 cases, TISN concentration increased, but with four others, TISN concentration decreased with at least one N rate. With four of these 10 cases, inhibition of nitrification had no effect on TISN concentration. Under the conditions of these field studies, DCD inhibited nitrification more often than not. Inhibition of nitrification was, however, more likely to reduce TISN concentration than to increase it. This may have been due to DCD effects on immobization of applied NH₄‐N.     

Can Nitrogen Source and Nitrification Inhibitors Affect In-Season Nitrogen Supply?

ABSTRACT

This study sought to identify whether piggery effluent-derived nitrogen sources can be formulated with urea and nitrification inhibitors to better synchronize nitrogen (N) supply with crop demand than conventional urea fertilizer alone. A 288 pot pasture growth and leaching growth accelerator trial (5 pasture cuts) was completed with a factorial treatment structure of three N sources (2.63 g N [kg soil]^?1 applied as 100% urea-N, 8% struvite-N + 92% urea-N, and 8% piggery pond sludge-N + 92% urea-N), five rates of three nitrification inhibitors (including 3,4-Dimethylpyrazole phosphate, DMPP; limonene+ethanol; and dicyandiamide, DCD), and matrix encapsulated forms of these inhibitors. Applying a combination of piggery sludge with urea increased N uptake during the first 4 weeks of plant growth (by 65%), though total N uptake throughout the trial (22 weeks) did not differ across the N-sources. The microbial community of the soil to which the sludge was added was significantly different from the un-amended soil at the conclusion of the trial. All inhibitor formulations significantly decreased leaching losses of mineral-N relative to the control (by 14 to 61%). The use of DMPP decreased initial nutrient uptake, deferring uptake until later in the experiment. Inhibitor addition resulted in microbial community effects that persisted throughout the trial. The study demonstrated that a piggery-derived N-source and a nitrification inhibitor can be used to manipulate plant N uptake to occur later or earlier in a growing period with equal cumulative uptake, achieving an 11% increase in residual N store, and decreased N leaching losses.     

Effects of a nitrification inhibitor on efficiency of nitrogen utilization by wheat and millet

Abstract

Preliminary soil incubation studies established that the nitrification inhibitor, Dicyandiamide (DCD), could maintain the ratio of NH.‐N to NO₃‐N at predetermined levels. When one part DCD was mixed with 10 parts of the ammonium fertilizer prior to incorporation with the soil, nitrification was inhibited for at least six weeks. In a greenhouse experiment, wheat was grown to maturity and millet to the flowering stage in pots containing nitrate and ammonium fertilizers treated with DCD. Soil analyses during the plant growth period indicated that ammonium oxidation in soil was effectively inhibited. Plants of both species exposed to ammonium only with DCD produced lower yields than those exposed to a mixture of nitrate and ammonium nitrogen with DCD. Plants supplied with nitrate‐only gave somewhat lower yields than the mixtures. The nitrate‐only treatments resulted in the lowest accumulation of reduced nitrogen compounds in shoots of both species. Magnesium uptake by millet and calcium and magnesium uptake by wheat were reduced as the proportion of ammonium in soil was increased.     

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。     

Nitrification Inhibitor,Fertilizer Rate,and Temperature Effects on Nitrous Oxide Emission and Nitrogen Transformation in Loamy Sand Soil

An incubation study investigated the effects of nitrification inhibitors (NIs), dicyandiamide (DCD), and neem oil on the nitrification process in loamy sand soil under different temperatures and fertilizer rates. Results showed that NIs decreased soil nitrification by slowing the conversion of soil ammonium (NH₄⁺)-nitrogen (N) and maintaining soil NH₄⁺-N and nitrate (NO₃^?)-N throughout the incubation time. DCD and neem oil decreased soil nitrous oxide (N₂O) emission by up to 30.9 and 18.8%, respectively. The effectiveness of DCD on reducing cumulative soil N₂O emission and retaining soil NH₄⁺-N was inconsistently greater than that of neem oil, but the NI rate was less obvious than temperature. Fertilizer rate had a stronger positive effect on soil nitrification than temperature, indicating that adding N into low-fertility soil had a greater influence on soil nitrification. DCD and neem oil would be a potential tool for slowing N fertilizer loss in a low-fertility soil under warm to hot climatic conditions.     

玉米滴灌栽培条件下尿素与氢醌、双氰胺配施方法及效果

本研究通过在滴灌栽培条件下将脲酶抑制剂氢醌(简称HQ)、硝化抑制剂双氰胺(简称DCD)和尿素在玉米盆栽试验中进行配施,以探求HQ和DCD在滴灌施氮肥条件下应用的可行性。试验共设17个处理。试验结果表明:在滴灌施尿素条件下,加入0.3%HQ、0.5%HQ和5.0%DCD于溶液中,尿素的氮素利用率分别为74.8%、75.8%和75.3%,均显著高于单独施用尿素处理;当将HQ和DCD进行土壤施用并配合滴灌浇水时,HQ对提高氮肥利用率无显著作用,但DCD的施用能显著提高尿素氮的利用率;HQ和DCD在滴灌施肥条件下的施用效果要好于土壤施用效果。     

不同硝化抑制剂的复配施用对尿素转化及土壤中氮的影响

通过室外模拟田间培养试验,研究不同硝化抑制剂及其复配后的硝化抑制效果。结果表明:不同硝化抑制剂,明显抑制了NH4+-N向NO3--N的转化。硝化抑制剂1-甲胺酰基-3,5-二甲基吡唑(CMP)有明显的抑制效果,优于4氨基-1,2,4-三唑盐酸盐(ATC)、双氰胺(DCD);硝化抑制剂CMP与DCD复配的抑制效果显著,硝化抑制率为35.6%。为了结合生产实际获得最优性价比,在硝化抑制剂复配比率方面尚需进一步研究。     

Reducing nitrous oxide emissions from a maize‐wheat sequence by decreasing soil nitrate concentration: effects of split application of pig slurry and dicyandiamide

Pig slurry (PS) is a valuable nitrogen (N) source for agricultural crops but the simultaneous supply of readily decomposable carbon and mineral N can result in large soil nitrous oxide (N₂O) emissions. Our objective was to determine the individual and combined effects of split PS application and addition of a nitrification inhibitor (dicyandiamide, DCD) on N₂O emissions and soil mineral N concentration in southern Brazil. Soil N₂O fluxes were measured from November 2010 to November 2011 from a maize (Zea mays L.)‐wheat (Triticum aestivum L.) sequence under various fertilizer treatments: no‐N control, PS applied in a single pre‐plant dose with or without DCD, PS split‐applied with or without DCD, and urea split‐applied. Cumulative N₂O emissions increased linearly (R² = 0.73) with increasing soil nitrate (NO₃^?) exposure, indicating that management practices aimed at reducing soil NO₃^? concentrations can decrease soil N₂O emissions. In total for the two crops, splitting PS reduced N₂O emission factors (EF) by 33%, whereas the addition of DCD reduced EF by 60 and 41% when PS was applied in single and split doses, respectively. However, splitting PS or adding DCD failed to reduce N₂O losses more than a single pre‐plant PS application in maize where background soil NO₃^? concentrations were large. The addition of DCD to PS applied as a single pre‐plant dose resulted in the largest reduction in soil N₂O emissions, whereas splitting PS with and without DCD resulted in significantly smaller abatements. Consequently, we concluded that adding DCD to PS in a single pre‐plant application is a better option than splitting PS applications for reducing soil N₂O emissions in no‐till cereal cropping systems in southern Brazil.     

The effect of dicyandiamide and neem cake on the nitrification of urea-derived ammonium under field conditions

Summary Dicyandiamide (DCD) and neem cake were evaluated for their efficiency in inhibiting nitrification of prilled urea-derived NH ₄ ⁺ –N in a wheat field. Prilled urea was blended with 10% and 20% DCD-N or 10% and 20% neem cake and incorporated into the soil just before the wheat was sown. Both DCD and neem cake partially inhibited nitrification of prilled urea-derived NH ₄ ⁺ ; DCD was better than neem cake. The nitrification-inhibiting effects of DCD lasted for 45 days, while that of neem cake lasted for only 30 days. Blending the prilled urea with DCD (20% on N basis) was most effective in inhibiting the nitrification of urea-derived NH ₄ ⁺ , both in terms of intensity and duration, and maintained substantially more NH ₄ ⁺ –N than the prilled urea alone and 20% neem-cake-blended urea for a period of 60 days.