Effect of management history and temperature on the mineralization of methylene urea in soil

A soil incubation and a greenhouse study on processing tomato were used to test the effects of soil temperature and the size and activity of the soil microbial biomass (SMB) on the degradation (mineralization) rate of a slow-release N fertilizer, methylene urea (MU), a condensation product of urea and formaldehyde. The mineralization rates of three MUs: Short (S), Medium (M), and Long (L) with different water solubilities were measured at two temperatures in a soil with low (fallow, F) and high (cover crop, CC) microbial activity. In the greenhouse study, the fate of fertilizer N was followed using ¹⁵N-urea and ¹⁵N-MU. The fertilizer N efficiency calculated for urea using the ¹⁵N mass balance approach was 93 and 85% compared with 65 and 67% for MU-S in F and CC soils, respectively. During six months of incubation, 52 and 63% of MU-S N was mineralized at 20 and 30 °C, respectively. The accumulated N data suggested that the degradation of all three MU types followed first-order reaction kinetics. The reaction rates were similar for all three MUs and increased with increasing temperature. However, fitting discrete, non-accumulated data revealed that MU mineralization is more complex and cannot be modeled with simple exponential decay equations. The size and activity of SMB did not affect the mineralization rate of MU-N under laboratory or greenhouse conditions. Interestingly, Activity Index (AI), defined as the slowly available pool of MU-N, was not a reliable indicator for the mineralization rate and plant availability of MU-N.     

Studies on depth of placement of urea on nitrogen recovery in wheat grown on a red-brown earth in Australia

Field and greenhouse experiments were carried out at the University of Sydneyto examine the influence of depth of placement of urea on crop nitrogen (N) uptake and N recovery in wheat grown on a red-brown earth in Australia. In the greenhouse, an ¹⁵N source of urea was used in examining the pattern of N availability, while field experiments using an unlabelled urea assessed the usefulness of deep placement of urea as a tool for improving N use by wheat.Placement at a depth of 15 cm slightly delayed the accessibility of N to the plant only in the early stages of growth, i.e., about 12 days after sowing. Large differences in N content and N concentration observed as a result of placement was only transient and disappeared later in the season. Total N recovery was 93.8% in the deep placement and 79.9% in the shallow placemen, but these differences were due to differences in soil N recovery, as crop N recovery was approximately 48% in both treatments.In the field, there was very little advantage in the deep placement compared with the shallow placement. Also, no residual benefit was observed as a result of increased depth of placement. Thus deep placement may not be an important strategy for increasing N uptake over a conventional shallow depth of 3–5 cm.     

Recent research on problems in the use of urea as a nitrogen fertilizer

Recent research on the NH₃ volatilization, NO ₂ ^- accumulation, and phytotoxicity problems encountered in the use of urea fertilizer is reviewed. This research has shown that the adverse effects of urea fertilizers on seed germination and seedling growth in soil are due to NH₃ produced through hydrolysis of urea by soil urease and can be eliminated by addition of a urease inhibitor to these fertilizers. It also has shown that the leaf burn commonly observed after foliar fertilization of soybean with urea results from accumulation of toxic amounts of urea in soybean leaves rather than formation of toxic amounts of NH3 through hydrolysis of urea by leaf urease. It further showed that this leaf burn is accordingly increased rather than decreased by addition of a urease inhibitor to the urea fertilizer applied. N-(n-butyl)thiophosphoric triamide (NBPT) is the most effective compound currently available for retarding hydrolysis of urea fertilizer in soil, decreasing NH3 volatilization and NO ₂ ^- accumulation in soils treated with urea, and eliminating the adverse effects of urea fertilizer on seed germination and seedling growth in soil. NBPT is a poor inhibitor of plant or microbial urease, but it decomposes quite rapidly in soil with formation of its oxon analog N-(n-butyl) phosphoric triamide, which is a potent inhibitor of urease activity. It is not as effective as phenylphosphorodiamidate (PPD) for retarding urea hydrolysis and ammonia volatilization in soils under waterlogged conditions, presumably because these conditions retard formation of its oxon analog. PPD is a potent inhibitor of urease activity but it decomposes quite rapidly in soils with formation of phenol, which is a relatively weak inhibitor of urease activity. Recent studies of the effects of pesticides on transformations of urea N in soil indicate that fungicides have greater potential than herbicides or insecticides for retarding hydrolysis of urea and nitrification of urea N in soil.     

控释尿素对小麦增产效果与提高氮肥利用率的研究

采用控释尿素和普通尿素两种氮素肥料进行优质小麦郑麦366肥效试验研究。两地试验结果表明：100％控释尿素处理产量最高,为7980kg／hm^2和8290kg／hm^2,与同等氮素用量的普通尿素相比增产12．0％、14．0％;产量随氮肥用量的增加而增加;用量70％控释尿素处理与用量100％普通尿素处理之间相比,产量差异不大,没有达到显著性差异,说明施用控释尿素可以比普通尿素减少1／3的纯氮用量。     

N2O and NO emissions from a field of Chinese cabbage as influenced by band application of urea or controlled-release urea fertilizers

A field experiment was conducted in an Andosol in Tsukuba, Japan to study the effect of banded fertilizer applications or reduced rate of fertilizer N (20% less) on emissions of nitrous oxide (N₂O) and nitric oxide (NO), and also crop yields of Chinese cabbage during the growing season in 2000. Six treatments were applied by randomized design with three replications, which were; no N fertilizer (CK); broadcast application of urea (BC); band application of urea (B); band application of urea at a rate 20% lower than B (BL); band application of controlled-release urea (CB) and band application of controlled-release urea at a rate 20% lower than CB (CBL). The results showed that reduced application rates, applied in bands, of both urea (BL) and controlled-release urea fertilizer (CBL) produced yields that were not significantly lower than yields from the full rate of broadcast urea (BC). The emissions of N₂O and NO from the reduced fertilizer treatments (BL, CBL) were lower than that of normal fertilizer rates (B, CB). N₂O and NO emissions from controlled-release urea applied in band mode (CB, CBL) were less than those from urea applied in band mode (B, BL). The total emissions of N₂O and NO indicated that applying fertilizers in band mode mitigated NO emission from soils, but N₂O emissions from banded urea (B) were no lower than from broadcast urea (BC).     

Parametric study of tumbling fluidized bed to evaluate nitrogen release characteristics of biopolymer-coated controlled release urea

To impede nitrogen loss due to leaching and NH₃ volatilization, pristine urea particles are coated with synthetic polymers such as poly(acrylic acid) and polyethylene for the controlled release of nitrogen. However, due to nonbiodegradability and environmental and economic issues, these synthetic polymers are replaced with cheap, biodegradable, and green coating materials. In this study, borax-modified starch biopolymer is used to produce controlled release urea (CRU) in a tumbling fluidized bed. Central composite rotatable design is used to study the interactive effect of process parameters on time and kinetics of nitrogen release. Nitrogen release in distilled water is monitored by the UV–Vis spectrophotometer and soil burial test is used to observe release in soil. The optimum values of process parameters and response objectives generated by the analysis of variance are validated by triplicates of confirmation runs and the % error is reported as a precision indicator. A mathematical model is used to determine the diffusion coefficient of nitrogen release. Biopolymer-coated urea results in much better release performance when compared with starch-based CRU reported in the literature. The most influential process parameter both for time and kinetics of nitrogen release appears to be the coating time. Release time increases linearly with coating time and the diffusion coefficient decreases with increase in coating time. The kinetic study reveals that some of the samples followed non-Fickian diffusion and others followed Case-II transport during the release of nitrogen.     

Ammonium bicarbonate used as a nitrogen fertilizer in China

This article reports a modified process for the production of synthetic ammonia, in which CO₂ in the converted water gas is removed by the synthesized ammonia itself, and the precipitated NH₄HCO₃ serves as the final product of the factory. NH₄HCO₃ pills weighing about 1 g are used to overcome the poor physical properties of the NH₄HCO₃ powder. Extensive field experiments laid down on various soil areas in China showed good crop responses when NH₄HCO₃ pills were deep dressed.A laboratory process for the preparation of coated NH₄HCO₃ pills as a slow-release fertilizer is described. The crop response to slow-release NH₄HCO₃ pills is discussed.     

The effect of nitrogen source and crop rotation on the growth and yield of processing tomatoes

Four crop rotation and management systems were studied in 1994 and 1995 in relation to growth and yield of irrigated processing tomatoes (Lycopersicon esculentum Mill.). The four treatments were three four-year rotation systems [conventional (conv-4), low input and organic] and a two-year rotation system [conventional (conv-2)]. The four-year rotation was tomato-safflower-corn-wheat(or oats+vetch)/beans, and the two-year rotation was tomato-wheat. Purple vetch (Vicia sativa L.) was grown as a green manure cover crop preceeding tomatoes in the low input and organic systems. Nitrogen was supplied as fertilizer in the conventional systems, as vetch green manure plus fertilizer in the low input system and as vetch green manure plus turkey manure in the organic system. Tomato cv. Brigade was direct-seeded in the conventional systems and transplanted to the field in the low input and organic systems. In both years the winter cover crop was composed of a mixture of vetch and volunteer oats with N contents of 2.2% in 1994 and 2.7% (low input) or 1.8% (organic) in 1995. In 1994 yields were higher in conventionally grown tomatoes because a virus in the nursery infected the transplants used in the low input and organic systems. In 1995 tomatoes grown with the low input and conv-4 systems had similar yields, which were higher than those of tomatoes grown with the conv-2 and organic systems. N uptake by the crop was greater than 200 kg N ha^–1 for high yield (> 75 t ha^–1) and uptake rates of 3 to 6 kg N ha^–1 day^–1 during the period of maximum uptake were observed. The lower yield with the organic system in 1995 was caused by a N deficiency. The main effect of the N deficiency was a reduced leaf area index and not a reduction of net assimilation rate (NAR) or radiation use efficiency (RUE). Nitrogen deficiency was related to low concentration of inorganic N in the soil and slow release of N from the cover crop + manure. A high proportion of N from the green manure but only a low proportion of N from the manure was mineralized during the crop season. In the conventional systems, the estimated mineralized N from the soil organic matter during the crop season was around 85 kg ha^–1. A hyperbolic relationship between N content and total dry weight of aboveground biomass was observed in procesing tomatoes with adequate N nutrition. Lower yields with the conv-2 than with the conv-4 system were due to higher incidence of diseases in the two year rotation which reduced the NAR and the RUE. Residual N in the soil in Oct. (two months after the incorporation of crop residues) ranged between 90 and 170 kg N ha^–1 in the 0–90 cm profile.Department of Vegetable Crops.     

Effects of sulfur-coated urea fertilizer regimes on production of processing tomatoes on a sandy loam

An initial broadcast application of sulfur-coated urea (SCU) fertilizer or 75% SCU — 25% ammonium nitrate (AN) provided no additional benefit over a similarly applied AN application in promoting vine growth or fruit yield of tomato (Lycopersicon esculentum Mill.). Additionally, AN alone promoted a significantly lower fruit pH. Irrigation effects did not interact with those of fertilizer treatments, but irrigation did significantly increase ripe yield 31% and vine dry weight 41%. The only effect of irrigation on fruit quality was a decrease in fruit soluble solids.     

以尿素为氮源的高氮复合肥生产技术

笔者根据多年的实践经验 ,阐述以尿素为氮源 ,生产高氮〔w(N)≥ 2 0 %〕复肥的现实意义及生产技术要点 ,具体介绍 2个高氮复肥 (2 30 7)、(2 0 10 15 )的配方实例及操作要点     

Recovery of nitrogen by spring barley from ammonium nitrate,urea and sulphur-coated urea as affected by time and method of application

The objective of this study was to increase the efficiency of fall-applied N either by placement in bands or by using a slow-release fertilizer. Four field experiments were conducted in north-central Alberta to determine the influence of N source, time of application and method of placement on the recovery of fall-applied N as soil mineral N in May, and on yield and recovery of N in grain of spring-sown barley. The recovery in soil of mineral N by May from the fall-applied fertilizers varied among treatments. More specifically, the recovery was lowest with topdressed application, highest with banding, and tended to be less with incorporation application as compared to banding. Recovery of mineral N was least for sulphur-coated urea (SCU) compared with A.N. and urea, regardless of method of application. The loss of fall-applied N was substantial, but leaching did not go beyond 60 cm deep.Yield and recovery of N in barley grain were much greater with spring application than with fall application at the 4 sites for ammonium nitrate (A.N.) and at 3 sites for urea. The SCU treatments were inferior. The A.N. and urea had greatest yield and N recovery with banding, followed by incorporation and then with topdressing for both fall- and spring-applied N. Method of application had little effect on yield and N uptake with SCU. In all, the greatest yield or crop N uptake was obtained with spring banding of A.N. or urea, while SCU did not function well as a fall- or spring-applied N fertilizer.(Contribution No. 680)     

Effect of lime nitrogen on the efficiency of urea and other ammonium nitrogen fertilizers

Five pot experiments were conducted with wheat and rice in a net house to study the effect of lime nitrogen (LN, contains about 55% calcium cyanamide) amendment rates on the efficiency of urea, the recovery urea-¹⁵N, the efficiency of the three nitrogen fertilizers(NF), on the efficiency of urea in the three soils, and on NO ₃ ^- -N leaching from a flooded soil. A rate of LN-N of 5–8% of applied fertilizer N increased the recovery of labeled urea-N by 9.42%. The effect of LN on the efficiency of NF was urea > ammonium sulfate > ammonium chloride. Under flooded conditions, LN decreased NO ₃ ^- formation and leaching.Responses of several crops to LN amended fertilizers were also studied in field experiments. At equal NPK applications, the efficiency of basal applications to rice, wheat, corn, potatoes, soybean, peanut, grapes, peaches, melon and watermelon were bette r with LN than without. Efficiency with a basal fertilizer for rice or wheat with LN were the same as with the same fertilizer without LN applied in split applications.     

Melamine and ammeline as nitrogen sources for turfgrasses

Melamine (2,4,6-triamino-1,3,5-triazine) and ammeline (4,6-diamino-1,3,5 triazine 2(1H)-one) were tested in a field study for N release characteristics, and response of Kentucky bluegrass to one and two applications of 98 kg N ha^–1. Melamine was also evaluated in combination with urea in a granule and in a liquid suspension. Mineralization of N from melamine and ammeline was slow. Soil concentrations of NH₄ and NO₃ in the surface 7-cm were less than 5% of the total N applied after 56 days. Recovery of N in the tissue was 5 and 11% of added melamine-N and ammeline-N respectively, during four months of sampling. Poor overall turf quality and number of dates of unacceptable quality also reflected the low mineralization of N from melamine and ammeline. The addition of urea to melamine improved plant N uptake, yield and turf quality. However, after the initial response to the urea component, little evidence of N release from melamine was observed over a four month period.Paper No.10 597 of the Journal Series of the Purdue Experiment Station, W. Lafayette, IN 47907.     

Relationship between electroultrafiltration (EUF) extractable nitrogen,grain yield,and optimum nitrogen fertilizer rates for winter wheat

The objective of the investigation was to examine whether there exist relationships between the optimum nitrogen fertilizer rate for winter wheat and soil nitrogen fractions extracted by electroultrafiltration (EUF) from autumn samples of the upper soil layer (0–30 cm). Optimum nitrogen fertilizer rates were derived from grain yield curves of field trials carried out with increasing nitrogen fertilizer rates on 19 different sites in 1985/86 and 1986/87. Most soils were luvisols derived from loess, two soils were brown earths and one a pararendzina. Total Nitrogen fertilizer rates were 0, 40, 80, and 120 kg N/ha applied twice before ear emergence. The final nitrogen rate at ear emergence was the same for all treatments, namely 60 kg N/ha.Optimum nitrogen fertilizer rates were derived from the grain yield curve fitted to a modified Mitscherlich equation. The optimum nitrogen fertilizer rates were correlated with the nitrogen fractions extracted by EUF. The regression equation thus obtained showed that NO ₃ ^- , the organic N fraction (EUF Norg), and the EUF Norg-quotient each had a highly significant impact on the optimum nitrogen fertilizer rate. The higher the amounts of EUF-N extracted the lower the optimum nitrogen rate. Substituting the EUF Norg-fraction for total nitrogen concentration in the upper soil layer gave a poorer relationship between the optimum nitrogen fertilizer rate and the soil data. In absolute terms the EUF Norg-fraction had by far the greatest impact on calculating the optimum nitrogen fertilizer rate. The investigation shows that the EUF method is a suitable technique for the determination of available soil nitrogen from which optimum nitrogen fertilizer rates can be derived for winter wheat cultivated under soil and climatic conditions typical for cereal growing areas in central Europe.     

复合氮素缓释剂的缓释机理与防结块作用

介绍复混肥料缓释与防结块处理的一种新技术。利用熔融尿素液代替机械油作为复合氮素缓释剂(由硝化抑制剂和尿酶抑制剂构成)与防结块剂(由石蜡和阴阳离子表面活性物质构成)的载体,其熔融液喷涂在复合肥颗粒表面可短时间在肥料颗粒表面固化,形成坚固的复合包膜层,经防结块测试,6个月的防结块率达94.6%,氮素利用率提高13%。     

Kinetic and thermodynamic investigation of Arthrospira (Spirulina) platensis fed‐batch cultivation in a tubular photobioreactor using urea as nitrogen source

BACKGROUND: Fed‐batch culture allows the cultivation of Arthrospira platensis using urea as nitrogen source. Tubular photobioreactors substantially increase cell growth, but the successful use of this cheap nitrogen source requires a knowledge of the kinetic and thermodynamic parameters of the process. This work aims at identifying the effect of two independent variables, temperature (T) and urea daily molar flow‐rate (U), on cell growth, biomass composition and thermodynamic parameters involved in this photosynthetic cultivation. RESULTS: The optimal values obtained were T = 32 °C and U = 1.16 mmol L^?1 d^?1, under which the maximum cell concentration was 4186 ± 39 mg L^?1, cell productivity 541 ± 5 mg L^?1 d^?1 and yield of biomass on nitrogen 14.3 ± 0.1 mg mg^?1. Applying an Arrhenius‐type approach, the thermodynamic parameters of growth (ΔH* = 98.2 kJ mol^?1; ΔS* = ? 0.020 kJ mol^?1 K^?1; ΔG* = 104.1 kJ mol^?1) and its thermal inactivation ( kJ mol^?1; kJ mol^?1 K^?1; kJ mol^?1) were estimated. CONCLUSIONS: To maximize cell growth T and U were simultaneously optimized. Biomass lipid content was not influenced by the experimental conditions, while protein content was dependent on both independent variables. Using urea as nitrogen source prevented the inhibitory effect already observed with ammonium salts. Copyright © 2012 Society of Chemical Industry     

超级杂交晚稻缓释氮肥最佳用量研究

采用集成栽培模式和农民习惯栽培模式,在5个施氮量的处理下,研究了缓释氮肥不同用量对超级杂交晚稻生长发育和产量的影响,并建立了产量与纯氮施用量的数学模型。结果表明：超级杂交晚稻的最佳施纯氮量和较经济的施纯氮量均为180kg／hm^2,此时2种栽培模式的产量均最高,分别为8．76和7．59t／hm^2,     

A nitrogen and phosphorus herbage nutrient index as a tool for assessing the effect of N and P supply on the dry matter yield of permanent pastures

In order to propose consistent decision rules for fertilizer supply, a study was made on the effect of additions of N and P fertilizers and of their interaction on the above-ground dry matter yield of pastures during spring. The interaction between N and P could occur through nutrient acquisition or nutrient efficiency for growth. We therefore characterised the herbage N and P status (N and P index) from previously established critical curves of herbage mineral content according to above-ground dry matter. First we studied the effect of N and P addition on herbage nutrient status. Secondly, we expressed the above-ground dry matter as a function of the herbage nutrient status. This study consisted of four treatments applied to four permanent pastures which had a low phosphorus availability. The results showed a positive effect of P supply on the herbage nitrogen status, which may be due to an increase of organic matter mineralization or root growth. The P herbage status decreased only if N was supplied without P. The dry matter yield was positively related to the herbage nitrogen status, but a low P herbage status reduced the slope of the relationship. For the pastures studied, the indirect effect of P supply on above-ground dry matter, revealed by an increase in N index, was greater than its direct effect. This methodology allows us to distinguish the direct and indirect effects of N and P addition on herbage growth at field level. It could be used to propose consistent rules to manage jointly both N and P supplies.     

Use ofLeucaena leucocephala (Lam. de Wit) leaves as a nitrogen source for crop production

Field and pot trials were conducted to determine optimum management practices for usingLeucaena leucocephala (Lam. de Wit) leaves as a N source for crop production. Field trials with maize showed no benefit from split application of leucaena leaves or from application of fresh as opposed to dried material. Field trials also failed to show any difference between incorporation as opposed to surface application of leucaena leaves. This may be attributed to the low nitrogen response observed. Pot trials however, showed that soil incorporation of leucaena leaves was more effective than surface application in increasing plant dry weight.Leucaena leaves were not as effective as inorganic N in increasing maize grain yield (field trials) or dry matter production (pot trial). Unlike inorganic N, leucaena leaves had a significant residual effect on the succeeding maize crop. In decomposition studies, buried leucaena leaves decomposed more quickly than surface-applied leaves, and fresh leaves decomposed more rapidly than dried leaves.     

100kt／a尿素熔融喷浆造粒复合肥装置运行中的问题和处理

介绍盘锦中润化工有限责任公司100kt/a尿基复合肥喷浆造粒装置工艺设计的基本情况(流程及主要设备规格),工艺特点;开车运行中出现的筛分、成球率低、冬季操作难度大等问题及解决措施.