In vitro effects of urease inhibitors on rate of urea hydrolysis in soils

We studied the effect of urease inhibitors on the urea hydrolysis in some Sundanese soils belonging to the orders of Vertisol and Entisol. The hydrolysis showed a lag period of about 3 days and its rate (Y) per unit time (t) could be described by a two constants exponential equation of the general form Y = K₁t^K ₂. Statistical analysis showed that the intercept K₁ (rate of urea hydrolysis) was significantly affected by soil type rather than treatment. It seems that K₁ is associated with the soils' initial urease activity as it closely correlates with the Michaelis constant (km).The gradient, K₂, being significantly affected by soil type as well as treatment is probably associated with the induced urease activity with time and it, therefore, varied with variations in soils and treatments. Of the so-called urease inhibitors used in this study Ca(OH)₂, p-benzoquinone (PBQ) and orthophosphoric acid (OP) only PBQ reduced urea hydrolysis while the other chemicals have effects possibly related to modifying the soil pH. Inhibitor treated soils had substantial amounts of unacounted for N which was believed to be present, presumably, in the form of carbamate.Contribution from the Department of Biochemistry and Soil Science, Faculty of Agriculture, Shambat, Sudan.     

ACES尿素装置高压设备腐蚀情况研究

介绍ACES尿素工艺的特点及其设备选材,重点阐述了渭化ACES装置高压设备腐蚀和失效的基本规律,分析了腐蚀产生的原因,从结构设计、钢材选用、设计加工、运行维护和设备管理等方面提出了防范措施。     

新型尿素产品的开发

介绍了国内外新型尿素产品（大颗粒尿素、涂层尿素、包膜尿素、长效尿素）的生产工艺和产品特点。     

Effect of nutrient seed coating on the emergence of wheat and oats

A series of experiments was conducted under controlled soil moisture and temperature conditions in a growth chamber to examine the effect of a range of nutrient seed coatings on the emergence to wheat (Triticum aestivum L. cv. Kite) and oats (Avena sativa L. cv. Blackbutt) sown in a coarse sandy loam soil. Final emergence of oats was not reduced by a coating containing 10 kg P ha^–1 (as monocalcium phosphate [MCP]) whereas the same coating reduced wheat emergence by 15%. The emergence of both wheat and oats was severely reduced by urea coatings (supplying 10 kg N ha^–1) to 33 and 13% respectively; this injury was lessened markedly by the inclusion of phenyl phosphorodiamidate (PPD) in the urea coatings at 1% (w/w) (emergence increased to 66 and 56% respectively).Low soil moisture (67% of field capacity [FC]) resulted in almost no emergence of wheat coated with urea (± bentonites of different pH). In soil at FC, the addition of bentonite of pH 5 (B5) to urea coatings permitted greater emergence (54%) than when bentonite of pH 9 (B9) was added (32%) which, in turn, permitted greater emergence than urea coating alone (10%). When PPD and bentonite (B5 or B9) were combined either singly or together with urea in seed coatings, PPD was more effective than either of the bentonites in reducing injury and masked the slight positive effect of B5.Coatings containing various combinations of N and P sources (at 3.6 and at 8 kg ha^–1 respectively) all reduced the emergence of wheat compared to raw seed (91% emergence). When applied alone, MCP was least damaging (74%); the combination of MCP with ammonium sulfate (AS) caused somewhat more injury (68%) whilst combination with calcium nitrate (CN) caused most injury (29%). In contrast, CN alone caused relatively little damage (73%) whilst AS alone was more damaging (50%). There was no significant regression found between percentage emergence and either the calculated partial salt index or the pH of the nutrient coatings. Further work is needed to examine the mechanisms of injury due to nutrient seed coatings so that safe but effective formulations can be developed.     

硫酸尿素系统化学反应的研究

研究了硫酸尿素系统在不同配比和不同温度的化学反应。结果表明，常温下硫酸与尿素的摩尔比为1：1．0和1：2．0时，可形成有固定熔点的晶体。其相变点温度在硫酸和尿素相变温度之间，相变热远远小于尿素。80～90℃时，硫酸尿素水溶液系统会发生水解反应，过程速率为二级，且水解速率远大于尿素水溶液系统；150℃以上时，硫酸尿素系统发生反应生成氨基磺酸硫酸铵。在工程设计和应用中，应严格控制硫酸尿素系统在80～90℃的停留时间，并保证系统温度不超过150℃。     

磷酰基(硫)脲类化合物的合成、性质及生物活性

综述了磷酰基（硫）脲类化合物的合成、性质及生物活性等方面的研究进展。     

流化床技术在提高尿素产品质量中的应用

应用尿素流化床装置有效解决了因造粒塔能力不足而造成的成品尿素温度偏高、粉尘含量较高、平均粒径偏小、存放易结块等问题，并且具有良好的经济效益。     

Influence of modified forms of urea and nitrogen levels on weed growth and grain yield of lowland rice

The growth of weeds and their subsequent reduction of rice yield as affected by N source neem cake coated urea (NCU), dicyandiamide coated urea (DCU), rock phosphate coated urea (RPCU), urea supergranules (USG) and prilled urea (PU) was studied on a clay loam soil at Coimbatore, India. Experiments were conducted in northeast monsoon (NEM) 1981, summer 1982, and southwest monsoon (SWM) 1982 seasons.The crop was associated with eleven weed species, and the dominant weeds wereEchinochloa crus-galli, Cyperus difformis andMarsilea quadrifolia. The weed flora varied between seasons. Deep placement of USG reduced the dry weight of weeds in NEM and summer seasons at 60, 90 and 120 Kg N ha^–1 whereas it increased the dry weight at 60 and 90 but not 120 Kg N ha^–1 in SWM season. The dry weight of weeds decreased with increased N rates for all N sources during NEM and summer seasons. In SWM season, dry weight of weeds increased with increased N rates for all N sources except USG. The grain yield of rice was drastically reduced with the deep placement of USG at 60 but not 120 Kg N ha^–1 in SWM season. The differential effect of the N sources between seasons was due to the change of the weed flora. Dominance ofE. crus-galli during SWM season had greater influence on weed dry weight and grain yield of rice.Nitrogen uptake by weeds was frequently greater in unfertilized plots, particularly in NEM and summer seasons. In SWM season, the apparent fertilizer N recovery by weeds was high for USG. It decreased from 53% for 60 Kg USG-N ha^–1 to 4% for 120 Kg USG-N ha^–1.Contribution from the part of Ph.D. work of the first author at Department of Agronomy, Tamil Nadu Agricultural University, Coimbatore-641 003, Tamil Nadu, India.     

尿素熔融喷浆造粒工艺在复混肥生产中的应用

介绍了在团粒法工艺的基础上,将尿素熔融成尿液进行喷浆造粒生产复混 肥过程中存在的问题,分析产生的原因并提出改进措施,对改造效果进行了总结。     

解吸水解装置存在问题分析及改进措施

分析解吸水解系统存在的工艺冷凝液流量及组分偏离设计值、塔盘吹翻、水解给料泵超负荷等问题，提出改进措施及建议。