Estimated NH3-volatilization losses from surface-applied urea on a wet calcareous Vertisol

Severe losses of NH₃ by volatilization are often reported when urea is surface applied to calcareous soils. Applications on wet soils may increase these losses. This study with N rates of 0, 20, 40, 80, 160, and 320 kg ha^?1 estimates the efficiency of urea application and predicts NH₃-volatilization losses when urea is surface applied on a wet calcareous soil. Placements consisted of three different methods of applying urea on or in the dry soil just prior to irrigation and a surface-broadcast treatment following irrigation. There were no significant yield differences between dry-soil placements, but all dry-soil placements gave significantly higher yields than did broadcast placement of urea on the wet soil. Thus, a second-order regression equation relating N rate and yield for dry-soil placements and another for wet-soil placement were used to determine the efficiency of wet- vs dry-soil applications of urea and to predict NH₃-volatilization losses from the wet soil. The efficiency was determined by three different procedures. The first compared the amount of N needed for wet- vs dry-soil conditions to produce discrete yields. The second compared the slope of the yield curves at discrete yield levels to determine the ratio of the amount of N needed to produce one additional increment of yield under wet- vs dry-soil conditions. The third was an estimation of the availability coefficient according to a method recently developed by HR Tejeda and others. Predicted NH₃ -volatilization losses were calculated from the efficiency values because loss of NH₃ from urea applied on or in dry soil followed very shortly by an irrigation should be almost nil. The efficiency factors averaged 55% for the first procedure and 51% for the second while the availability coefficient was 59%. Thus, the average estimate for efficiency of urea on wet vs dry soil was 55% and predicted losses of N by NH₃ volatilization averaged 45% when urea was applied to the wet surface of this calcareous soil.     

Agronomic effectiveness of urea deep placement technology for upland maize production

Nutrient Cycling in Agroecosystems - Effective fertilizer management is critical for sustainable maize production. Field trials were conducted in six locations in northern Ghana during the 2016 and...     

湿法磷酸制取磷酸脲工艺优化及杂质行为研究

二水法生产的湿法磷酸中存在大量的阴离子和阳离子,这些离子很难在磷酸净化过程中除去。用湿法磷酸直接制取磷酸脲时,杂质离子会影响介稳区宽度,进而影响产品的产率和质量。通过改变原料配比、反应时间、反应温度、降温速度、结晶温度和搅拌速度等因素探索了湿法磷酸直接生产磷酸脲的最佳工艺条件,并分析湿法磷酸中存在 的SO42-、SiF62-、Fe3+、Al3+和Mg2+几种主要杂质离子对磷酸脲的产率和产品质量的影响。实验发现,保持一定量的SiF62-浓度有利于提高产品产率,但是其浓度不宜太高。SO42-、Fe3+、Al3+和Mg2+等会降低磷酸脲的产率,并且 Fe3+和Al3+对产率影响较大。     

石灰性灰潮土水稻施磷效应及利用率

以通州区石灰性灰潮土为供试土壤,研究了不同施磷水平对土壤速效磷含量及水稻产量的影响,测定了水稻不同施磷水平下磷肥的利用率。结果表明,在中等含磷的土壤上,石灰性灰潮土的磷肥系数为1.72,磷肥临界值为6.0 mg/kg;水稻合理施用磷肥能显著增产,但产量只在一定的施磷水平下随着施磷量的增加而增加,其667 m2最经济施磷量为3.8 kg,最高产量施磷量为9.4 kg。磷肥利用率则随施磷量的增加而逐渐下降,平均利用率为8.5%。     

尿液喷浆造粒生产复合肥

我公司有50 kt/a和100 kt/a复合肥生产线各一条,另有150 kt/a的尿素生产能力.主要产品以高浓度、高氮复混肥为主,有15-15-15、16-16-16复合肥、20-17-11高效复混肥、21-12-7小麦专用肥、15-10-20生姜专用肥、25-10-0芝麻专用肥等.2000年底在100 kt/a复合肥生产线上,实施了尿液喷浆造粒生产复合肥的改造.该工艺运行初期,存在一些问题,我公司根据具体情况,针对存在的问题,制定了相应的对策和整改措施.整改后通过2001年至2002年5月份的运行,证明了该工艺是先进的,运行是稳定可靠的,制定的整改措施和对策是切实可行的.下面介绍改造情况.     

尿素高压甲铵冷凝器常见腐蚀分析

对尿素高压甲铵冷凝器在生产运行过程所出现的一些腐蚀情况进行分析,并对设备被腐蚀后的修复,减少和降低设备腐蚀提出一些建议。     

Effect of rate and method of phosphate placement on productivity of durum wheat in a Mediterranean climate

The authors demonstrated in part I that phosphate banded with the seeds of durum wheat (Triticum vulgare), L., cv. Sham 1) was generally superior to broadcasting in improving P uptake, especially at early growth. These results were confirmed for three consecutive seasons at three experimental sites with calcareous soils in Northern Syria (mean annual rainfall 281–471 mm). Two mechanisms have been postulated by various authors to explain the advantageous effect of banding on P fertilizer use efficiency: i) banding reduces soil to fertilizer contact resulting in less immobilization of P by fixation in the calcareous soils and ii) banding increases the root to P fertilizer contact and concentration, resulting in greater P uptake. The present work was designed to test these two hypotheses by measuring within the surface 20 cm of soil, i) the effect of method (banding vs. broadcasting) of P application (0, 17.5 and 52.5 kg P ha^?1 as triple superphosphate) on the change of NaHCO₃-extractable P with time and ii) the length and distribution of roots at tillering in relation to the distribution of available P in the soil. It was found that: i) The reduction in P availability with time was independent of the method of P placement and the residual NaHCO₃-P one year after its application was practically the same (for the same rate of P, whether banded or broadcast; and ii) the growth of roots was increased in the volumes of soil containing the P fertilizer, particularly where P was banded. It was concluded that, for wheat grown in calcareous soils in a Mediterranean climate, the greater uptake of P by crops where the fertilizer was banded was due to an increased probability of contact between roots and P fertilizer granules.     

Leaf phosphorus and sorghum yield under rainfed cropping of a Vertisol

Little attention has been devoted to the calibration of plant P tests for sorghum, especially under rainfed cropping although information is needed for developing an efficient P management strategy for increasing crop productivity. A field experiment was conducted for three years (1987–1989) to study the response of sorghum to fertilizer P (0, 10, 20 and 40 kg P ha-1) on a Vertisol, low in extractable P, at the ICRISAT Center, Patancheru (near Hyderabad), India. One sorghum crop was grown each year during the rainy season (June–September). Leaf tissue samples consisting of newest, fully-developed leaf, were collected at 50% flowering stage of the crop, for establishing relationship between leaf P concentration and grain yield. During the three years,sorghum grain yield and leaf P concentration increased in response to P application up to 40 kg P ha-1 and the leaf P concentration was linearly related to grain yield (r2 varied from 0.724 to 0.993). The critical leaf P concentration at 90% of the maximum grain yield was found to be about 0.25% P. Phosphorus content in the grain was not significantly correlated to yield.     

尿素熔融喷浆造粒工艺生产复合肥

在料浆法和团粒法制复混肥的基础上,推出尿素熔融喷浆造粒生产复混肥工艺。介绍其工艺流程、主要设备、主要工艺指标及如何防止尿液在管道、阀门、喷头中堵塞,防止缩二脲的生成,并进行了投资分析与经济效益测算。利用尿素熔融喷浆造粒生产复混肥,可显著提高生产能力,产品圆润光滑,不易结块,对原料适应性强,能全部以尿素为氮源。     

尿素熔融喷浆造粒工艺生产复合肥

介绍在传统转鼓造粒生产复肥的基础上 ,用尿素熔融液作为氮源及转鼓造粒的液相进行造粒 ,生产三元复肥的工艺路线、运行状况、工艺控制参数和产品指标。该工艺与传统转鼓造粒相比的最大特点是 :解决了传统法用尿素为氮源 ,使烘干温度和产品水分难以控制的困难 ,产量提高近 30 % ,成球率由 40 %～ 6 0 %提高到 70 %～80 % ,产品外观改善。但在生产中要妥善解决尿素浓溶液易结晶堵塞管道以及尿素在高温下易生成缩二脲的问题     

Urea release rate from a scoop of coated pure urea beads: Unified extreme analysis

Urea release from a scoop of coated beads in a given volume of a well stirred liquid has been investigated analytically and experimentally. A method for determining the fractional cumulative release and fractional release rate curves for the scoop without knowing particle number and radii is presented. The representative D/K_b for a scoop of urea beads spray coated with ethyl cellulose is near 3.5 × 10⁻⁸ cm²/s, and that with cellulose acetate phthalate is near 7 × 10⁻⁸ cm²/s.     

Response of sorghum to fertilizer phosphorus and its residual value in a Vertisol

The response of crops to added P in Vertisols is generally less predictable than in other soil types under similar agroclimatic conditions. Very few studies have considered the residual effects of P while studying responses to fresh P applications. Field experiments were conducted for three years to study the response of sorghum to fertilizer P applied at 0, 10, 20 and 40 kg P ha^–1, and its residual value in a Vertisol, very low in extractable P (0.4 mg P kg^–1 soil), at the ICRISAT Center, Patancheru (near Hyderbad), India. In order to compare the response to fresh and residual P directly in each season, a split-plot design was adopted. One crop of sorghum (cv CSH6) was grown each year during the rainy season (June-September).The phenology of the sorghum crop and its harvest index were greatly affected by P application. The days to 50% flowering and physiological maturity were significantly reduced by P application as well as by the residues of fertilizer P applied in the previous season. In the first year of the experiment, sorghum grain yield increased from 0.14 t (no P added) to 3.48 t ha^–1 with P added at the rate of 40 kg P ha^–1. Phosphorus applied in the previous year was 58% as effective as fresh P but P applied two years earlier was only 18% as effective as fresh P.     

Urea and formamide as a mixed plasticizer for thermoplastic starch

Mixtures of urea and formamide were tested as plasticizers for thermoplastic starch (TPS). The hydrogen bonding interactions between urea/formamide and starch were investigated by using Fourier‐transform infrared spectroscopy (FT‐IR). The thermal stability, mechanical properties and starch retrogradation behavior were also studied by thermogravimetric analysis (TGA), tensile testing and X‐ray diffraction (XRD), respectively. TPS plasticized by urea (20 wt%) and formamide (10 wt%) showed better thermal stability and water resistance than conventional TPS plasticized by glycerol. Moreover, the tensile stress, strain and energy at break, respectively, reached 4.83 MPa, 104.6 % and 2.17 N m after storing in an atmosphere of relative humidity (RH) of 33 % for one week. At the same time, this mixed plasticizer could effectively restrain the retrogradation of starch. Copyright © 2004 Society of Chemical Industry     

The effect of fertilizer placement on nitrogen uptake and yield of wheat and maize in Chinese loess soils

Field trials were carried out to study the fate of¹⁵N-labelled urea applied to summer maize and winter wheat in loess soils in Shaanxi Province, north-west China. In the maize experiment, nitrogen was applied at rates of 0 or 210 kg N ha^–1, either as a surface application, mixed uniformly with the top 0.15 m of soil, or placed in holes 0.1 m deep adjacent to each plant and then covered with soil. In the wheat experiment, nitrogen was applied at rates of 0, 75 or 150 kg N ha^–1, either to the surface, or incorporated by mixing with the top 0.15 m, or placed in a band at 0.15 m depth. Measurements were made of crop N uptake, residual fertilizer N and soil mineral N. The total above-ground dry matter yield of maize varied between 7.6 and 11.9 t ha^–1. The crop recovery of fertilizer N following point placement was 25% of that applied, which was higher than that from the surface application (18%) or incorporation by mixing (18%). The total grain yield of wheat varied between 4.3 and 4.7 t ha^–1. In the surface applications, the recovery of fertilizer-derived nitrogen (25%) was considerably lower than that from the mixing treatments and banded placements (33 and 36%). The fertilizer N application rate had a significant effect on grain and total dry matter yield, as well as on total N uptake and grain N contents. The main mechanism for loss of N appeared to be by ammonia volatilization, rather than leaching. High mineral N concentrations remained in the soil at harvest, following both crops, demonstrating a potential for significant reductions in N application rates without associated loss in yield.     

Fate of fertiliser N applied to winter wheat growing on a Vertisol in a Mediterranean environment

A field study using 15N was conducted on a Vertisol in semi-arid Morocco to assess the fate and efficiency of fertiliser N split applied to winter wheat (Triticum aestivum L.). Splitting of fertiliser N is highly crucial in semi-arid regions, considering the increased moisture stress towards the end of the growing season. A N fertilisation rate of 100 kg N ha-1 was split according to two schemes: i) 25% at planting, 50% at tillering and 25% at stem elongation; or ii) 50% at tillering and 50% at stem elongation. The application of 100 kg N ha-1increased the vegetative dry matter production with more than 2000 kg dry matter ha-1 in comparison with the control treatment. Nitrogen fertilisation had no significant effect on the grain yield production. Moreover, the 1000 grain weight decreased from 32 to 26 g due to N fertilisation. Total N uptake was about 50 kg N ha-1 higher for the fertilised plants in comparison with the unfertilised plants, but it was not affected by the splitting pattern of the fertiliser N. Recoveries of 15N-labelled fertiliser by the plant (above-ground plant parts plus roots from the upper 20 cm layer) were low (31% and 24% for the 3-split and 2-split application, respectively). More N in the plant was derived from fertiliser when applied early in the growing season than when applied late in the season. About 13% of the N in the plants was derived from the 50 kg N ha-1 at tillering, while only 5% was derived from the N application (50 kg N ha-1) at stem elongation. At harvest, a high residual of fertiliser-derived N was found in the 0–90 cm profile (62% and 72%, for the 3-split and 2-split application, respectively). Less than 10% of the applied N could not be accounted for, the amount being highest for the application at tillering. This N not accounted for was mainly ascribed to denitrification after an important rainfall event. The application of fertiliser N led to an increase of about 20 kg N ha-1 in soil N uptake by the crop (positive ANI). The results suggested a dominant influence of moisture availability on the fertiliser N uptake by wheat.     

缓释和控释尿素的研究与开发综述

分析了尿素利用率低对环境的影响和尿素在土壤中的释放过程，阐述了各种缓释和控释尿素的产品设计，缓释机理和制备方法以及国内外对缓释和控释尿素尤其是包膜尿素的研发进展，对提高尿素利用率，研究高效控释包膜尿素进行了展望。     

尿素过磷酸钙的新工艺研究

通过一系列的实验室试验和小型中间连续试验,明确了宜昌磷矿制尿素过磷酸钙的可行性。通过与先前实验的比较,可以认为在制尿素过磷酸钙时,宜昌磷矿的反应活性介于摩洛歌磷酸与开阳磷矿之间。通常,较低的熟化温度对尿素过磷酸钼产品的品质有利,研究表明,尿素过酸酸钙新工艺较“固化无机酸工艺更适合我国国是值得应用。     

造粒机性能对塑料生产率的影响

针对某厂塑料挤出机生产能力降低的问题 ,引用有关挤出理论 ,就影响挤出机生产率的原因作了分析 ,提出了解决问题的措施     

CD在某硅钙质胶磷矿选矿中的应用

某硅钙质胶磷矿正—反浮选工艺流程中,采用CD作为碳酸盐抑制剂,在正浮选作业中能较好地脱除一部分碳酸盐杂质,使得精矿脱镁率由6.49%提高至21.98%,反浮选药剂用量减少,且反浮选作业的泡沫性质得到改善,有利于工业化生产。     

Fertilizer recommendations for maize production in the South Sudan and Sudano-Guinean zones of Benin

The present study aims to determine fertilizer (N–P–K) recommendations for maize (Zea mays L.) on Acrisols (south Benin) and Ferric and Plintic Luvisols (centre Benin). Two years (2011 and 2012) experiment was conducted at Dogbo and Allada districts (southern) and Dassa (centre Benin). Six on-farm experiments were carried out to validate fertilizer rates simulated by the DSSAT model. The experimental design in each field was a completely randomized bloc with four replications and ten N–P–K rates: 0–0–0 (control), 44–15–17.5 (standard fertilizer recommendation for maize), 80–30–40, 80–15–40, 80–30–25, 80–30–0, 69–30–40, 92–30–40, 69–15–25 and 46–15–25 kg ha^?1. Treatments 44–15–17.5 and 46–15–25 showed the lowest grain and stover yields. The observed maize grain yields were highly correlated with the estimated grain yields (R² values varied between 80 and 91% for growing season 2011 and between 68 and 94% for growing season of 2012). The NRSME values varied between 12.54 and 22.56% (for growing season of 2011) and between 13.09 and 24.13% (for growing season of 2012). The economic analysis for the past 32 years (1980–2012) including the current experiment showed that N–P–K rates 80–30–25 (at Dogbo), 80–15–40 (at Allada) and 80–30–0 (at Dassa) were the best fertilizer recommendations as they presented the highest grain yields and the best return to investment per hectare. Nevertheless, 80–30–25 is advised for Dassa considering that sustainable maize production will require regular inputs of potassium. The 2 years of field experiments were not sufficient to derive biophysically optimal fertilizer recommendation rates for each site.