Urea is an organic compound that occurs naturally. Synthetic Urea is the most widely used nitrogen fertiliser in the world.
The wide acceptance of Urea is due to its agronomic acceptability and its low relative cost. Granular Urea is tailored for easy handling, even spreading and blending.
Plants take up nitrogen from the soil in the mineral forms of nitrogen, both ammonium and nitrate before converting it to plant protein nitrogen. Plants vary in their preference to utilise either form of nitrogen. Nitrate is considered the main source because it is mobile in the soil. On addition to the soil, Urea dissolves into the soil solution and is converted to ammonium and then to nitrate.
Conversion is favoured by:
- Temperature – the activity range is wide, varying from -20°C to 37°C with the optimum >20°C.
- Organic matter – activity is enhanced in soils high in organic matter which favours microbial activity.
- The time for Urea to be converted to ammonium will depend on the conditions of moisture and temperature. The reaction will begin to occur 24 hours after application and be complete within 2 to 5 days. The reaction time is slowest in cold, waterlogged conditions.
- It is these biological processes in the release of nitrogen from Urea to plants that gives Urea its main characteristic of a slower release form of nitrogen. Urea has longer availability for uptake by plants and release rates that are more closely related to plant growth.