Nitrogen (N) losses in the form of ammonia volatilization limit the efficiency of urea-based fertilizers world-wide. Urease inhibitor, N-(n-butyl) thiophosphoric triamide (NBPT) is a promising additive to reduce this N loss. Studies were conducted to test the efficacy of a relatively new NBPT formulation, ARM U (18% NBPT m/v), containing a proprietary polymer that allows for a low NBPT application rate in reducing ammonia volatilization from urea-based fertilizers. The results showed that ARM U reduced ammonia volatilization by an average of 85% across three soils and its effectiveness was not significantly different from other commercial NBPT formulations whose NBPT concentrations were 33-67% greater than ARM U. Further studies showed that delaying N fertilizer application until late-fall, as recommended on the Canadian prairies, did not stop ammonia volatilization from urea-based fertilizers. Across 4 site-year, total ammonia volatilization (% of applied N) from untreated urea-based fertilizers applied in the fall and spring were 14 and 16%, respectively. We found that the reduction of ammonia volatilization by NBPT was significantly greater in the fall (65%) than in the spring (40%) across 4 site-year and the addition of NI with NBPT (double inhibitor, DI) reduced the efficacy of NBPT in decreasing ammonia volatilization from spring-applied urea by 27%. The conserved N by NBPT and DI improved the crop N use efficiency at one of the two sites in this study. Investigation on the interaction between NBPT and NI on urea hydrolysis in five soils at 21 oC and six soils at 5, 15, and 25 oC showed that while NBPT reduced the rate of urea hydrolysis across soils and temperatures, the addition of NI reduced the inhibitory effect of NBPT on urea hydrolysis. Hence, reduction in ammonia volatilization is less with DI than only NBPT. Overall, the research shows that (i) NBPT effectively reduced ammonia volatilization even at a low concentration (ii) significant ammonia volatilization could occur from urea-based fertilizers even at soil temperature below 3 oC (iii) use of NBPT to bridge crop urea use efficiency is site-specific (iv) NI impaired the effectiveness of NBPT in suppressing urea hydrolysis and ammonia volatilization.

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 .

This book addresses basic and applied aspects of two nexus points of microorganisms in agro-ecosystems, namely their functional role as bio-fertilizers and bio-pesticides. Readers will find detailed information on all of the aspects that are required to make a microbe “agriculturally beneficial.” A healthy, balanced soil ecosystem provides a habitat for crops to grow without the need for interventions such as agro-chemicals. No organism in an agro-ecosystem can flourish individually, which is why research on the interaction of microorganisms with higher forms of life has increasingly gained momentum in the last 10-15 years. In fact, most of plants’ life processes only become possible through interactions with microorganisms. Using these “little helpers” as a biological alternative to agro-chemicals is a highly contemporary field of research. The information presented here is based on the authors’ extensive experience in the subject area, gathered in the course of their careers in the field of agricultural microbiology. The book offers a valuable resource for all readers who are actively involved in research on agriculturally beneficial microorganisms. In addition, it will help prepare readers for the future challenges that climate change will pose for agriculture and will help to bridge the current gaps between different scientific communities.

When fertilizer nitrogen (N) is applied to soil it is not used efficiently and plant N uptake is seldom greater than 50% of the N applied. One of the reasons for poor N use efficiency is high losses from the plant-soil system by ammonia (NH3) volatilization, during nitrification and by leaching, erosion, surface runoff and denitrification. The loss of N represents an economic loss to farmers and has environmental implications for water quality and greenhouse gas emissions. Stabilised N fertilizers (urease and nitrification inhibitors) have received considerable attention recently due to their potential to lower N losses to the environment and increase crop yields. However, the efficacy of urease and nitrification inhibitors can be quite variable depending on the crop, soil properties, climatic and management factors. Many compounds have been evaluated as urease or nitrification inhibitors however, few meet the requirements of being effective at low concentrations, non toxic, stable, inexpensive and compatible with standard N fertilizers. Urease inhibitors delay the rate of urea hydrolysis to ammonium-N (NH4+-N) and hence prevent localised zones of high pH and NH4+-N concentrations in soil, which are conducive to NH3 volatilization. They are expected to be most beneficial on soils where NH3 volatilization from urea fertilizer is high. The urease inhibitor N-(n-butyl) thiophosphoric triamide (trade name Agrotain(r)) is the most successful commercially, where it has been shown to lower NH3 volatilization from surface-applied urea and increase yields on a wide range of crops. Agrotain is now licensed or sold in over 70 countries worldwide, in both agricultural and amenity markets.

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

It is the aim of this book to present reviews on a wide range of aspects of bacterial respiratory systems. Because the on-going publication elsewhere of reviews on bacterial respiration, ablanket coverage of the field has not been attempted. Rather, a range of topics have been selected, either because they are of special current interest, they have not been reviewed recently, or they have never been reviewed.