Fertilizer consumption has increased three fold during the past 30 years. It reached one million nutrient tones in 1980/81, two million tons in 1992/93 and three million tons in 2002/03. Urea, today, is made in approximately 75 factories worldwide with a total capacity approaching 100,000,000 tons annually. Urea hydrolyzed by urease. Sodium Thiosulfate (ST) has been reported to inhibit nitrification and urea hydrolysis and thereby reduces volatilization of urea nitrogen as ammonia from soils fertilized with urea. A laboratory experiment was carried out by adding ST to urea (10 % by volume). We evaluated ST as a soil urease inhibitor by studying its effects on urea hydrolysis. Encouraging results were found in reducing NH3 losses when ST was applied it reduced NH3 losses in cotton 35.13%, 31.65% and 35.35%, 32.77% in Rice soils in first and second experiment respectively. It functions as urease and nitrification inhibitor.

Symposiumverslagen over: de omvang van ureum als meststof op de wereldmarkt; bodem-, milieu- en beheersfactoren die de ammoniakvervluchtiging beinvloeden; factoren die de ureumhydrolyse beinvloeden; de chemische balans m.b.t. de ammoniakvervluchtiging; modelmatige weergave voor het voorspellen van de vervluchtiging; vergelijking van methoden voor ammoniakmetingen; ontwikkelingen omtrent de toepassing van remstoffen bij de urease-vorming; mechanismen bij de urease-vorming; ammoniakvervluchtiging van ureumfosfaatmeststoffen

The purpose of our present work is to review the fundamental studies on inhibition of soil urease activity and the applied studies on improving efficiency of urea fertilizers by inhibition of soil urease activity. The general literature on these topics covers 65 years, and the patent literature comprises a period of nearly 40 years. Studies related to inhibition of soil urease activity were performed in a great number of countries' well representing all the continents. Full texts of the papers describing these studies were published in one of 18 languages·'. The literature data reviewed are structured into 10 chapters, 81 subchapters, and 224 sections. The bibliographical list consists of 830 papers cited. ·In alphabetical order: Argentina, Armenia, Australia, Austria, Belgium, Belorussia, Brazil. Bulgaria, Canada, China, Costa Rica, Cuba. Czech RepUblic, Egypt, Estonia, France, Georgia (Gruzia), Germany, Hungary, India, Iraq, Ireland, Israel, Italy. Japan, Kazakhstan, Lithuania, Malaysia, Moldova, Netherlands, New Zealand, Pakistan, Philippines, Poland, Romania, Russia, Saudi Arabia, Slovakia, South Africa, South Korea, Spain, Sri Lanka. Sudan, Sweden, Thailand, Turkey, Ukraine, United Kingdom, United States of America. Uzbekistan .