Methylene urea as a slow-release nitrogen source for processing tomatoes

The potential for improved fertilizer N use efficiency was tested using a slow release N fertilizer, methylene urea (MU), on processing tomato (Lycopersicon esculentum Mill.) in a 2-year field study in the Sacramento Valley, California. Fertilizer N use efficiency of urea and a (50:50, w:w) mixture of urea and MU (uMU) was determined in direct-seeded and transplanted tomato plots with winter cover crop (CC) or winter fallow (F) using ¹⁵N labeled fertilizers. Residual MU-N was estimated from tomato N uptake in the ¹⁵N microplots, and from residual ¹⁵N uptake of wheat grown after two tomato crops. No significant differences were found in the quantity and quality of tomato yields among fertilizer and management treatments during the first year. Total yields in transplanted FuMU plots were significantly lower in the second test year, suggesting slow mineralization of MU-N in the F treatment. On average, about 40% of added fertilizer N was taken up in both fertilizer treatments, and the recovery of ¹⁵N in plant biomass and soil was 75–96 and 50–74% in seeded and transplanted blocks, respectively. In the laboratory, mineralization of MU started faster in soils with past MU use, but the enhanced mineralization did not affect the plant N uptake in the field. MU is potentially an environmentally attractive fertilizer, but without an immediate increase in yield and N use efficiency compared to conventional fertilizers, its use on row crops may not be economically feasible unless the positive environmental factors like decreased leaching of N are considered.     

控释尿素与普通尿素配施比例对玉米产量及效益的影响

为推广缓控释肥在玉米上的应用,进行了控释尿素和普通尿素不同掺混比例的复混肥对玉米肥效的试验。结果表明,玉米施用控释氮比例为40%的控释氮肥时,玉米产量及其构成因素、叶面积、种植效益较高。     

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.     

Slow-release urea fertilizers — effect on floodwater chemistry,ammonia volatilization and rice growth in an alkali soil

In experiments with transplanted rice (Oryza sativa L.) at the Central Soil Salinity Research Institute, Karnal, India, two methods of application of granular urea, wholly as basal dose U(W) or in splits U(S) were compared with deep, point placement (8 cm) of urea supergranules and broadcast application of two slow-release sources, sulphur-coated urea (SCU) and lac-coated urea (LCU). Comparisons were made in wet season 1984 and 1985 on the basis of ammoniacal N concentration and pH of floodwater, ammonia volatilization, rice yield and N uptake.In 1984 the highest peak concentrations of ammoniacal N (AN) in the floodwater, > 12g m^–3, and ammonia volatilization losses 54% of applied N were produced in U(W). Application of N in splits U(S) reduced peak AN levels 5g m^–3 and losses to 45.1%. LCU was ineffective in reducing peak AN levels ( 7.5g m^–3) or losses (43.6%). However SCU and USG were effective in reducing peak AN levels to < 2g m^–3 and N losses to 16.9 and 3.4% respectively. Total ammonia volatilization losses as well as the initial rate of loss correlated very well with the peak levels (second day) of AN, NH₃ (aq.) as well as equilibrium vapour pressure of NH₃. Floodwater pH was between 9.5 and 10.0.Split application of granular urea was generally more efficient in terms of yield and N recovery (41.4%, average of two years) as compared to whole application (29.5%). LCU was ineffective in improving grain yields or N recovery (30.9%). SCU was ineffective in improving grain yields but improved N recovery to 57.9%., USG increased grain yields only in first year by 19% over U(S) and improved N uptake to 60.5%. A negative linear relationship was established between N uptake by rice at harvest and AN levels in floodwater two days after fertilization which can be used as an index to evaluate fertilizers.     

尿素在土壤中的转化与植物利用效率

尿素在土壤中的水解速率受土壤脲酶活性、p H值、温度、水分、质地、尿素起始浓度等因素的影响 ,以脲酶最为关键。当前控制尿素水解转化的有效技术措施有添加脲酶抑制剂、硝化抑制剂、尿素包膜以及表面膜技术的应用等 ,本文从新型脲酶抑制剂的使用、缓释尿素的研制以及尿素与其它肥料配合施用等方面探讨提高尿素氮利用率。     

Effect of band spacing of urea on dry matter and crude protein yield of bromegrass

Microplot experiments were conducted at two locations (Lacombe and Eckville) in central Alberta to evaluate methods of application of urea (60 kg N ha^–1) on established meadow bromegrass (Bromus biebersteinii L. cv Regar). Urea was surface broadcast and banded 4 cm deep into soil at four row-spacings (15, 22.5, 30 and 37.5 cm). The dry matter and crude protein yield were generally greatest in plots when urea was banded at 15 cm spacing. There was a general decrease in dry matter yield, particularly with the first cut at the Lacombe site when urea was banded at more than 15 cm spacing. The dry matter yield, crude protein yield and crude protein concentration were significantly greater in grass adjacent to the banded fertilizer than in grass from the area midway between the bands at the Lacombe site.     

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。     

Ammonia volatilization from urea nitricphosphate and urea applied to the soil surface

Urea nitricphosphate (UNP) is an N-P fertilizer prepared by solubilizing phosphate ore with nitric acid and conditioning the product with urea. The product is acidic, and its nutrient analysis is 23-12-0. Urea makes up 74% of the N component of this material and the remainder comes from the nitrate added as nitric acid. In volatilization trials, UNP lost significantly less N than did urea in a noncalcareous soil (13 and 31% respectively). In calcareous soils the urea-N component of UNP exhibited loss patterns similar to those of urea. Soil pH remained stable at the center of the granule placement site during UNP hydrolysis, thereby reducing NH₃ loss, whereas the pH of the same soil treated with urea rose almost 1.9 units. The urea component of UNP appeared to diffuse from the center of the acidic microsite allowing hydrolysis to take place and permitting limited NH₃ volatilization to occur. UNP appears to be an attractive NP fertilizer in terms of nutrient analysis and resistance of the N component to volatile N losses as NH₃.     

Solubility of metallic-salt in acid nutrients in acid fertilizer solutions of urea phosphate,urea sulfate and urea nitrate

Solubilities of individual metallic-salt micronutrients were determined at 0°C in saturated acid fertilizer solutions of urea phosphate, urea sulfate, and urea nitrate. By using the acid pH mechanism, less expensive metallic salts can be used with drip irrigation applications to supply specific micronutrient needs to crops.Solubility of the sulfates of Cu, Fe, Mn, and Zn varied with each acid solution. Solubility of the above sources in the urea sulfate solutions also varied with the amount of sulfate in solution. The solubility of molybdenum decreased with the acidic conditions of the urea nitrate acid solution but appeared to increase for the urea phosphate and urea sulfate acid solutions. Boron was only slightly soluble in all the acid solutions.     

Effect of soil bulk density on hydrolysis of surface-applied urea in unsaturated soils

In situ hydrolysis of broadcast urea occurs in unsaturated soils with different bulk densities. The effect of increasing soil bulk densities on the hydrolysis of urea was studied in open and in covered unsaturated soil columns incubated at 30°C. An increase in bulk density from 0.8 to 1.4 Mg/m³ markedly increased the hydrolysis of surface-applied urea in soils containing water > 6% up to near field capacity. Increased diffusion of urea to sorbed soil urease with an increase in bulk density may have enhanced formation of urease-urea complexes and therefore increased the hydrolysis. As urea diffused farther in more dense soils, the retarding effects of high urea concentration gradients on the hydrolysis probably decreased. In light-textured soils, increases in the bulk density had no apparent effect on the hydrolysis of surface-applied urea when evaporation occurred.     

硫酸脲复合肥对玉米生长指标及产量的影响

通过田间试验方式研究硫酸脲复合肥、普通缓释肥、硫基肥、BB肥对玉米生长和产量的影响。结果表明,4种肥料处理均能促进玉米植株茎粗、穗粗和穗行数的增加,特别是硫酸脲复合肥处理,较CK分别增加了3.8%、3.6%和18.2%;而且4种肥料处理对玉米也有不同程度的增产效应,其中硫酸脲复合肥处理增产率最高,为21.09%。     

Effects of initial soil calcium content on ammonia losses from surface-applied urea and calcium-urea

Ammonia loss from surface-applied urea occurs because urea hydrolysis increases the pH of the placement site microenvironment. Addition of Ca-salts with urea will control or reduce the microsite pH, thus reducing NH₃ losses. The degree of Ca-saturation of the cation exchange sites may influence the ratio of calcium:urea required to control ammonia loss. A laboratory study was conducted to determine if adsorbed Ca or CaCO₃ additions (acid soils only) had a measureable impact on Ca control of NH₃ loss from surface applied urea at various Ca:urea ratios.With urea alone applied to the soil surface varying the adsorbed Ca content of the treatment soil did not influence NH₃ loss. The addition of CaCl₂ with urea on the same pretreated soils generally resulted in NH₃ losses reflecting the initial pH of the soil. The Ca-saturated acid soils and those acid soils receiving CaCO₃ had higher NH₃ losses than untreated soils in the presence of urea with soluble CaCl₂. It was noted that increasing the calcium:urea ratios progressively depressed the NH₃ loss from all soils. Increasing the percent Na-saturation of the calcareous Harkey soil to 25 and 50% (ESP) reduced Ca control of NH₃ loss due to Ca being exchanged for Na on the cation exchange sites.Inclusion of CaCl₂ with the urea mixture on the surface of the pretreated acid soils resulted in stepwise differences in NH₃ loss concuring with the increases in pretreatment soil pH values (differing exchangeable Ca content). Other parameters that influence the amount of NH₃ loss, such as acidic buffer capacity and CEC, appeared more important than anticipated for control of NH₃ loss with the calcium:urea mixture. On Ca enriched soils the calcium:urea mixture was only slightly less effective in its ability to control NH₃ losses than on untreated soils.Contribution from the Texas Agric. Exp. Sta., Texas A&M University System, College Station, TX 77843, USA     

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).     

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.     

Effect of urea granule size on ammonia volatilization from surface-applied urea

Urea powder and granules of varying size (1 to 8 mm diameter) were surface applied to a ryegrass/white clover pasture. Evolution of NH₃ was measured using a continuous air flow enclosure method. At 30 kg N ha^–1, the percentage of urea-N lost as NH₃ from powder or granules of 1–2, 3–4, 5.6 and 8 mm diameter was 18, 17, 20, 22 and 32 respectively. As the particle size increased, the rate of urea hydrolysis decreased and delayed the time at which the maximum rate of volatilization occurred. Mineral-N and soil surface pH measurements confirmed that during the period of volatilization, urea moved less than 30 mm from the application point.For the powder and 3–4 mm granule treatments, when the application rate was increased from 30 to 300 kg N ha^–1, the percentage of urea-N volatilized increased, but at any particular rate there was no significant difference in percentage loss between the powder and 3–4 mm granules.     

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.     

腐植酸尿素对冬小麦增产效果及氮肥利用率的影响

以冬小麦为试验材料,研究腐植酸尿素对其产量构成因素、产量及氮肥利用率的影响。试验结果表明:腐植酸尿素能显著提高冬小麦产量、千粒重及氮肥利用率。施用腐植酸尿素I型和腐植酸尿素II型与农民习惯施肥相比,冬小麦产量分别增加753.2、756.9 kg/hm~2,千粒重分别提高1.3、1.4 g,氮肥利用率分别提高11.97、11.60个百分点;与普通BB肥相比,冬小麦产量分别增加897.7、894.0 kg/hm~2,千粒重分别提高0.5、0.6 g,氮肥利用率分别提高10.11、9.74个百分点。     

松香包膜尿素的释放特性研究

以松香为成膜物质,制备了一系列的包膜尿素,利用扫描电子显微镜研究了包膜尿素的表面形貌,用浸泡溶解法表征了所得包膜尿素的释放特性,讨论了包覆量与操作条件对包膜尿素释放特性的影响。结果表明,松香是一种优良的尿素包膜材料,包覆量在5%以上时,松香包膜尿素具有显著缓释性能,包覆量越大,缓释效果越好。     

Plant response to the management of fluid and solid N fertilizers applied to furrow-irrigated corn

The use of fluid fertilizers has increased in recent years. Plant response to field management practices of fluid and solid N fertilizers in furrow-irrigated field studies has not been well-documented. This research studied the response of corn (Zea mays L.) to several field management practices of fluid and solid N fertilizers applied at several rates. Corn grown with sidedressed applications of the fluid fertilizers, urea ammonium nitrate (UAN) and 18-0-0+7Ca, generally had higher grain yields, higher yield efficiencies, higher ear populations, larger seed size, more kernels per ear, and a higher ear leaf N concentration than corn grown with preplant broadcast treatments of urea, ammonium nitrate (AN), and UAN. In 1988, corn grown with 280 kg N ha^–1 of AN applied preplant broadcast had a lower grain yield, yield efficiency, kernels per ear, and ear leaf N concentration, while ear population and kernel size were unchanged, in comparison to split applications of UAN at 224 kg N ha^–1. In 1989, corn grown with three split applications of UAN at 280 kg N ha^–1 had a higher grain yield and produced more kernels per ear without affecting yield efficiency, ear population, kernel size, or ear leaf N concentration compared with treatments at the 224 kg N ha^–1 rate. Use of split, side-dressed N management practices in furrow-irrigated corn should eliminate the need to use excessive N rates while maintaining grain yields and other plant responses, resulting in more efficient N use than traditionally achieved.     

Effect of surfactant on zeta potential and rheology behavior of methylene bis(thiocyanate) suspension concentrate

Methylene bis(thiocyanate)(MBT) is insoluble in water, so suspension concentrate(SC) of MBT is extremely relied on surfactants. In this paper, SC of MBT was prepared with wet-grinding technology, and the effect of surfactants,such as Morwet D425(D425) and Morwet EFW(EFW)(two kinds of dispersant), on the Zeta potential and rheology behavior of MBT SC were investigated. The results showed that the Zeta potential absolute value of MBT SC increased with the increasing content of D425, and it decreased with the increasing content of EFW at acidic solution(pH = 4.5). In the combination system of D425 and EFW, Zeta potential of MBT SC decreased first and then increased with the increasing content of EFW. The relationship between shear rate(γ) and viscosity(η) was studied according to Herschel–Bulkley model: η = η0+ k/γ, and the relationship between shear rate(γ) and shear force(τ) was investigated according to:τ = τ0+Kγ~n. It was revealed that the mixed fluid belonged to Yield Pseudoplastic Fluid.