Mineralization of urea,coated urea and nitrification inhibitor treated urea in different rice growing soils

Mineralization of urea, sulphur coated (SCU), neem cake coated urea (NCU) and N-Serve treated urea (NSU) was studied in four important rice growing soils of India, namely, an alluvial soil (Entisol-Fluvent), a black cotton soil (Vertisol-Ustert), two laterite soils (Oxisol-Acrothox) and an acid sulphate soil (Entisol-Sulphaquent) for a period of four weeks at a temperature of 30°C ± 2°C and a water tension of 1/3 bar. Hydrolysis of urea was faster in alkaline alluvial and black cotton soils than in acid laterite and acid sulphate soil. NH₄-N content in soil was the highest with N-Serve during the entire period of study. SCU maintained lower NH₄-N in soil than urea only during the first two weeks of incubation. N-Serve was much more effective in inhibiting nitrification than neem cake in all the soils. Inhibition of nitrification by neem cake was most at the end of first week in alkaline and at the end of second week in all other soils. Coating of urea with neem cake imparted both slow-release and nitrification inhibiting properties.     

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.     

Crop yield and soil nitrogen dynamics in an intermittently flooded rice field affected by nitrification inhibitors

A field experiment was conducted to study yield and soil N dynamics in an irrigated, intermittently submerged rice field at New Delhi, India, where chemically synthesized as well as neem derived urea coating nitrification inhibitors with prilled urea were applied. Rice (var. IR-32) was grown on a Typic Ustochrept alluvial soil. No nitrogen (control), prilled urea alone, prilled urea mixed with dicyandiamide (DCD), neem (powdered Azadirachta indica Juss. seeds) coated urea and Nimin (commercial derivative of neem) coated urea were tested for their efficacy in regulating yield and conservation of N. None of the inhibitors could increase biomass or grain yield over urea. But all the inhibitors were able to conserve soil ammonium and DCD was the most efficient nitrification inhibitor followed by Nimin coated urea. N-uptake, recovery, physiological and agronomic efficiencies were highest in urea treated plots. The performances of all the inhibitors were against the popular trend where crop yield and N-uptake were enhanced by their application. But, more studies are required on the performance of these inhibitors in rice fields to come to a stronger conclusion.     

Influence of rates and sources of nitrogen on growth,nitrogen uptake and yield of cotton (G. hirsutum L.)

Field experiments on cotton with different forms of urea applied at rates of 40 and 80 kg N/ha were carried out. The results indicated that application of nitrogen increased plant height, dry matter accumulation, number of bolls per plant, seed cotton yield and nitrogen uptake. The proportion of dry matter and nitrogen in the stem was increased and that in the leaves was reduced by N application. Sulphur coated urea (all applied at sowing) was about the same in effect as N-Serve treated urea and gave significantly more seed cotton yield than untreated urea, neem cake treated urea and sulphur coated urea (applied in two splits). Nitrogen efficiency as expressed by kg seed cotton production per kg N applied was greater with 40 kg N/ha rate than with 80 kg N/ha. Sulphur coated urea (all applied at sowing) gave the highest nitrogen efficiency followed by N-Serve treated urea.     

STUDIES ON THE MINERALIZATION OF UREA, COATED UREA, AND NITRIFICATION INHIBITOR TREATED UREA IN SOIL

A laboratory incubation study was conducted with a sandy clay loam soil (pH 7.8) at New Delhi to study the mineralization of urea, coated urea (sulphur-coated urea, shellac-coated urea), and urea treated with nitrification inhibitors (N-Serve, sulphathiazole) a general purpose microbicide (coal tar), and neem (a non edible oil-seed) cake. Coated fertilizers mineralized much slower than urea; urea-N from these materials remaining in soil after z weeks of incubation being two to three times that from untreated urea. However, most N from coated fertilizers was mineralized after 4 weeks. Nitrification inhibitors were quite effective in retarding the nitrification of urea; N-serve being much more effective than sulphathiazole. Neem cake and coal tar extract were less effective than sulphathiazole in controlling nitrification of urea but they did retard the nitrification of urea for z weeks.     

Influence of edaphic factors on the mineralization of neem oil coated urea in four Indian soils

The utility of neem (Azadirachta indica A Juss) oil coated urea as a value-added nitrogenous fertilizer has been now widely accepted by Indian farmers and the fertilizer industry. In the present study, the expeller grade (EG) and hexane-extracted (HE) neem oils, the two most common commercial grades, were used to prepare neem oil coated urea (NOCU) of various oil doses, for which mineralization rates were assessed in four soils at three incubation temperatures (20, 27, and 35 degrees C). Neem oil dose-dependent conservation of ammonium N was observed in NOCU treatments in all of the soils. However, a longer incubation period and a higher soil temperature caused depletion of ammonium N. Overall, the nitrification in NOCU treatment averaged 56.6% against 77.3% for prilled urea in four soils. NOCU prepared from EG neem oil was consistently superior to that derived from hexane-extracted oil. The performance of NOCUs was best in coarse-textured soil and poorest in sodic soil. The nitrification rate (NR) of the NOCUs in the soils followed the order sodic > fine-textured > medium-textured > coarse-textured. The influence of edaphic factors on NR of NOCUs has been highlighted. The utility of the present study in predicting the performance of NOCU in diverse Indian soils was highlighted through the use of algorithms for computation of the optimum neem oil dose that would cause maximum inhibition of nitrification in any soil.     

Efficiency of Coated Urea on Nutrient Uptake and Maize Production

A field experiment was conducted to study the effects of coated urea with urease inhibitor [copper (Cu) and zinc (Zn)], nitrification inhibitor (DMPP), biochar and geopolymer on ammonium, nitrate, Cu, Zn content and crop yield of maize. The treatments were composed of urea alone (control), urea coated Cu and Zn (UCuZn), urea coated with Cu, Zn, and DMPP (UCuZnDMPP), urea impregnated with biochar (Ubio) and urea coated with geopolymer (Ug2). Data showed that treatments with Cu, Zn, and DMPP produced lower ammonium (NH₄) and nitrate (NO₃) in UCuZn and UCuZnDMPP while they had the highest concentration of Cu and Zn in soil and plant tissues. Plots treated with UCuZn and UCuZnDMPP produced maximum N concentrations in grains and yield, with increases by 79.5% and 74.1%, respectively, as compared with urea (control). This finding demonstrates that by slow down the hydrolysis and nitrification process using urease and nitrification inhibitor were beneficial to increased N uptake, ultimately produced higher yield.     

Influence of physicochemical parameters of neem (Azadirachta indica A Juss) oils on nitrification inhibition in soil

The technology for the production of neem oil coated urea (NOCU) developed by the Indian Agricultural Research Institute is in the pipeline for adaption by several Indian fertilizer industries. Use of nitrification inhibitors is one of the methods of improving the nitrogen use efficiency (NUE) of nitrogenous fertilizers in agriculture. However, standard specifications for the neem oil as a raw material of NOCU are desired. Accordingly, the present study was undertaken to evaluate 25 samples of neem oils comprising 11 samples of expeller grade (EG) oils, 8 samples of cold-pressed (CP) oils, 3 samples of solvent-extracted oils, and 2 commercial formulations. NOCU was prepared using these oils (5000 ppm of urea-N). The soils fertilized with NOCUs (200 ppm of urea-N) were incubated at 27 degrees C and 50% water-holding capacity for a period of 15 days. Nitrapyrin (0.5% of N) coated urea served as the reference and prilled urea as control. Samples were analyzed for NH4+-N, NO2--N, and NO3--N using standard methods. The percent nitrification inhibition (NI) was calculated, and the results revealed that all of the neem oils caused NI ranging from 4.0 to 30.9%. Two samples of EG oils and two commercial formulations were found to be the best, causing 27.0-30.9% NI. Iodine, acid, and saponification values and meliacin content of all of the oils were analyzed and correlated with NI. The results revealed the direct influence of meliacin content of the neem oils on NI, which, however, was found to be negatively correlated with saponification and iodine values. There is, therefore, a need to introduce new Bureau of Indian Standards (BIS) specifications for neem oils as raw materials of NOCU.     

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。     

Effect of levels and sources of nitrogen on concentration and uptake of nitrogen by a high yielding variety and a hybrid of rice

Field experiments were made on a sandy clay loam soil at the Indian Agricultural Research Institute, New Delhi to study the effect of levels and sources of nitrogen on concentration and uptake of nitrogen by a high yielding variety Pusa 834 and a hybrid PRH3 of rice. Nitrogen concentration in hybrid PRH 3 remained lower than in Pusa 834, but N uptake was significantly more in the hybrid PRH 3. Nitrogen fertilization increased N concentration as well as N uptake by rice. At 30 days after transplanting (DAT) N uptake was more in Pusa 834, but at 60 DAT and at harvest hybrid PRH 3 recorded significantly more N uptake than Pusa 834. Use of neem oil blended urea (PNGU) and neem coated urea (NCU) increased N concentration and uptake by rice in both Pusa 834 and hybrid PRH 3. Use of neem coated/blended urea is recommended for rice.     

Coating of essential oils onto prilled urea retards its nitrification in soil

Increased use of nitrogenous fertilizers in agriculture has led to the increased pollution of ground water and atmosphere. Certain plant products can be used as coating materials onto urea to reduce the N losses. We evaluated the effectiveness of citronella and palmarosa grass oils as nitrification inhibitors in a soil incubation study. The treatments (14) were combinations of 4 N sources (neem, citronella and palmarosa oil coated prilled ureas, and uncoated prilled urea), 2 coating thicknesses of oils (500 and 1000 mg kg^?1) and 2 N levels (75 and 150 kg N ha^?1), replicated thrice in a randomized block design. N levels at 75 and 150 kg ha^?1 were equivalent to 34 and 68 mg N kg^?1 soil, respectively. Results showed that N sources citronella (CCPU₁₀₀₀) and neem oil (NCPU₁₀₀₀) coated prilled ureas at 1000 mg kg^?1 coating thickness with 75 kg ha^?1 released similar amount of ammonical-N to uncoated prilled urea at 150 kg N ha^?1, suggesting the beneficial effect of coated ureas. The highest nitrification inhibition (%) was recorded with NCPU₁₀₀₀, the reference nitrification inhibitor, which was significantly greater to all the other N sources at 7 days after incubation (DAI), and at par to CCPU₁₀₀₀ at 14 and 21 DAI.     

尿素与缓释尿素配施添加DMPP对砂姜黑土氮素转化的影响

研究尿素与缓释尿素配施添加硝化抑制剂3,4-二甲基吡唑磷酸（DMPP）对砂姜黑土氮素转化的影响，为田间速效与缓释氮的合理配施提供理论依据。采用室内恒温、恒湿培养试验方法，试验设不施肥（CK）、单施尿素（N）、单施缓释尿素（S）、60%尿素+40%缓释尿素（NS）、尿素+DMPP（ND）、缓释尿素+DMPP（SD）、60%尿素+40%缓释尿素+DMPP（NSD）共七个处理，通过测定不同处理土壤中不同形态氮素含量，探究添加DMPP在单施尿素、单施缓释尿素及尿素与缓释尿素配施上对土壤氮素转化的不同影响。ND处理在培养第1~35 d内铵态氮含量均显著高于N处理（P<0.05），并有效延缓了铵态氮向硝态氮转化的时间。SD处理较之S处理在显著提高土壤中铵态氮含量的同时（P<0.05），也能有效抑制硝化作用，其硝化抑制有效作用时间在49 d左右，并且在此期间内能降低表观硝化率，提高硝化抑制率。与NS处理相比，NSD处理不仅能够显著提高土壤铵态氮含量（P<0.05），使铵态氮半衰期延长至18.6 d，硝化抑制率显著提高（P<0.05），表观硝化作用有效抑制时间延长了32 d左右。综合分析表明，尿素与缓释尿素配施添加DMPP在抑制氨氧化作用中效果明显，显著提高硝化抑制率（P<0.05），降低表观硝化率，有效延长了铵态氮在土壤中停留的时间，该措施为有效阻控农田氮素损失提供了科学依据。     

FIELD AND LABORATORY STUDIES COMPARING NUTRISPHERE-NITROGEN UREA WITH UREA IN NORTH DAKOTA,ARKANSAS, AND MISSISSIPPI

Nitrification and ammonia volatility are two important impediments to nitrogen (N) use efficiency and crop uptake around the world. Nutrisphere® is a relatively new product whose manufacturer claims both nitrification and urea volatilization inhibiting properties. Urea coated with Nutrisphere is and the resulting fertilizer is called Nutrisphere®-N urea, or Nutrisphere-N (NSN). Eight field studies on spring (Triticum aestivum L.) or durum [T. turgidum L. subsp duram (Desf.) Husn.] wheat in North Dakota, three field studies in Mississippi/Arkansas on rice (Oryza sativa L.), four laboratory experiments in North Dakota and one in Arkansas were conducted to determine the nitrification and urea volatilization inhibiting ability of NSN compared with urea alone. Results of field and laboratory experiments revealed that the product has no nitrification or urea volatilization inhibiting properties at the recommended rates and spring wheat and rice did not benefit from the application of NSN to urea.     

棕壤地区玉米和水稻施用聚合物包膜尿素效应初报

通过一年田间小区试验,研究了棕壤地区施用MEISTER热塑性树脂包膜尿素对玉米和水稻生物性状、产量以及田间土壤NH+4-N和NO-3-N一直保4-N和NO-3-N的影响。结果表明,施用MEISTER包膜尿素能使土壤NH+持在较高水平,并且使玉米和水稻产量分别增加了5.1%和15.1%。当MEISTER包膜尿素施用量减少20%时,玉米和水稻产量与尿素追施处理相当,但玉米根和叶中氮的含量以及水稻秸杆和根中氮含量明显降低。MEISTER包膜尿素配施DCD没有进一步增加玉米和水稻的产量,DCD抑制土壤硝化作用的效果不稳定。     

Comparison of Conventional and Polymer Coated Urea as Nitrogen Sources for Lowland Rice Production

Nitrogen (N) is one of the most yield limiting nutrients in lowland rice production. Improving N use efficiency is essential to reduce cost of crop production and environmental pollution. A greenhouse experiment was conducted with the objective to compare conventional and polymer coated urea for lowland rice production. Grain yield, straw yield, panicle density, maximum root length, and root dry weight were significantly increased in a quadratic fashion with the increase of N rate from 0 to 400 mg kg^?1 soil. Nitrogen source X N rate interactions for most of these traits were not significant, indicating that lowland rice responded similarly to change in N rates of two N sources. Based on regression equations, maximum grain yield was obtained with the application of 258 mg N kg^?1 soil and maximum straw yield was obtained with the addition of 309 mg N kg^?1 soil. Nitrogen use efficiency (grain yield per unit of N applied) was maximum for polymer coated urea compared to conventional urea. Root length and root dry weight improved at an adequate N rate, indicating importance of N fertilization in the absorption of water and nutrients and consequently yield. Polymer coated urea had higher soil exchangeable calcium (Ca) and magnesium (Mg), Ca saturation, Mg saturation, base saturation, and effective cation exchange capacity compared to conventional urea. There was a highly significant decrease in soil exchangeable potassium (K) with increasing N rates at harvest of rice plants.     

黏土矿物混合生物炭包膜尿素的制备及其氮素污染减排潜力

为促进氮肥高效利用,实现氮素污染减排,选用膨润土和生物炭作为包膜材料,结合硝化抑制剂制备包膜尿素。设置包膜尿素淋溶模拟试验收集淋溶液,结合静态箱法收集N₂O,通过分析NH₄⁺-N,NO₃^--N淋失量和N₂O排放通量对包膜尿素氮素污染减排潜力进行了评估。结果表明:（1）膨润混合土生物炭包膜尿素（F₄）NH₄⁺-N淋溶损失率最低,较纯化肥尿素（F₁）NH₄⁺-N淋溶损失率降低19.76%。（2）硝化抑制剂型膨润土生物炭包膜尿素（F₅）NO₃^--N淋失率最低,较F₁降低16.74%。（3）F₅同时具有最优的N₂O减排效果,N₂O排放量较F₁降低77.8%。F₅氮素减排效果最优,其减排机制在于一方面硝化抑制剂可以从化学过程控制硝化和反硝化进程,延缓尿素酰胺态氮的水解和铵态氮的硝化,在降低NO₃^--N淋失的同时可以实现N₂O减排。另一方面F₅的包膜材料膨润土和生物炭可以通过吸附作用将更多的NH₄⁺-N富集在土壤表层,从而显著降低NH₄⁺-N淋失。综上所述,硝化抑制剂型膨润土生物炭包膜尿素氮素污染减排潜力最优,可使NH₄⁺-N,NO₃^--N和N₂O分别减排15.24%,16.74%和77.8%。     

Urea N uptake efficiency of ryegrass (Lolium perenne L.) in the presence of urease inhibitors

Summary A greenhouse experiment was conducted to study the comparative efficiency of urea as an N fertilizer with and without the addition of different urease inhibitors. Ryegrass (Lolium perenne L.) was used as the test plant and the N balance technique with ¹⁵N was applied. Three urease inhibitors, hydroquinone, phenyl phosphorodiamidate (PPDA), and N-(n-butyl) phosphorothioic triamide (NBPT), were evaluated for their effects on urea-N uptake as well as on grass yield. The addition of urease inhibitors, except for hydroquinone in the later growth period, did not significantly influence the dry matter weight. Throughout the whole growth period, only NBPT significantly increased the total urea-N uptake. In the uninhibited system, the major fertilizer N loss occurred during the first period of grass growth, presumably via NH₃ volatilization, since the environment did not favour the other pathways of N loss. However, an appreciable amount of urea N was lost during the later growth period in all inhibited systems, especially in the hydroquinone-treated system. This indicates that the application of urease inhibitors could not eliminate the urea N loss. The greater N loss in the hydroquinone-treated soil appears to be related to the inhibition by hydroquinone of nitrification.     

控释尿素不同施用条件下冬小麦产量和氮素利用效应

采用田间试验方法研究了控释尿素不同施用条件对冬小麦产量、氮素利用和经济效益的影响。试验共设7个处理,即CK(空白处理,不施氮肥)、100%PU10/0(普通尿素全量基施,N 240 kg·hm-2)、100%PU6/4(60%的普通尿素基施、40%的普通尿素于拔节期追施,N 240 kg·hm-2)、80%PU6/4(60%的普通尿素基施、40%的普通尿素于拔节期追施,N 192 kg·hm-2)、100%CRU(全量树脂包膜控释尿素基施,N 240 kg·hm-2)、80%CRU(80%树脂包膜控释尿素基施,N 192 kg·hm-2)和40%CRU+40%PU(40%树脂包膜控释尿素+40%的普通尿素基施,N 192 kg·hm-2)。结果表明,无论是产量效应还是氮素利用效应,树脂包膜控释尿素(CRU)处理总体优于普通尿素(PU)处理,尤其树脂包膜控释尿素和普通尿素配施(40%CRU+40%PU)效果最佳,以7 709 kg·hm-2的产量、36.44%的氮肥吸收利用率、15 946元·hm-2的相对净收入达到处理间最高水平。该处理在减少氮素投入量的情况下,不仅促进了冬小麦增产,而且显著提高了肥料的利用率,拥有较高的产投比。因此,树脂包膜控释尿素和普通尿素的配施处理(40%CRU+40%PU)是本试验条件下最优的氮肥处理。     

包膜尿素的养分释放特征及其肥效

应用固-液反应包膜工艺，采用4种改性的无机包膜材料，试制出了成本较低的包膜缓释尿素，用水中溶出率法测定了包膜缓释尿素的养分释放特征，应用盆栽水稻评价了包膜缓释尿素的肥效，并与国外的有机缓释氮肥（Methylene Urea）和高聚物包膜复合肥（Osmocotte）进行了比较，表明固-液反应型包膜尿素具有较好的养分缓释效果，4种包膜尿素与等氮和等重常规尿素相比，栽培水稻都有一定的增产作用，并提高了肥料利用率，其中LU增产最显著，比等氮和等重尿素处理分别增产41．5％和35．7％，肥料当季利用率达到43．9％，好于国外的有机缓释氮肥和高聚物包膜复合肥。养分释放特征与水稻氮素营养特征较为接近，可为水稻一次性施肥所用。     

Urea transformation in some tropical soils

The effects of incubation at 20°, 30° and 40°C and urea concentrations of 0, 50, 100 and 200 μg N/g soil on urea hydrolysis and nitrification were investigated in three Nigerian soils. At constant temperature urea hydrolysis and rate of NO₃^? accumulation increased with increasing rate of urea addition. Urea was rapidly hydrolyzed within 1 week of incubation. Nitrification in Apomu soil increased with increasing incubation temperature. Nitrification was slow in acid Nkpologu soil (pH 4.7). Texture, cation exchange capacity and C:N ratios of the soils were not related to urea hydrolysis or nitrification. Nitrite accumulation in these soils was insignificant. Soil pH was decreased by nitrification of hydrolyzed urea-N.