Urea transformations - Urea is the most commonly used N fertilizer in the world. When applied to soil, it is first sub- ject to breakdown by a naturally occurring enzyme (urease) into ammonium. The ammonium is subsequently converted to nitrate through nitrifying bacteria. Understanding these transformations helps with management decisions to use urea most efficiently. Ammonia volatilization - In alkaline soil, ammonium in fertilizer and manure is chemically transformed into ammonia gas which can be lost to the atmosphere. This is not only an economic loss of a valuable nutrient, but can be detrimental for air quality. A number of practical management techniques Nitrogen N O T E SNUMBER 1Nitrogen Notes is a series of bulletins written by scientific staff of the International Plant Nutrition Institute (IPNI). This series was supported by a grant from the California Department of Food & Agriculture and through a partnership with the Western Plant Health Association. This series is available as PDF files at www.ipni.net/publications.Managing Nitrogenare available to minimize ammonia loss and maximize its re- covery by crops. Nitrate leaching - An adequate supply of nitrate is critical for supporting plant growth, but it is vulnerable to leaching through soil. Minimizing nitrate leaching from the root zone requires simultaneous management of two essential factors for plant growth; N and water. Careful nutrient management planning and irrigation techniques are required to minimize nitrate- leaching losses.
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