Loss of Nitrogen from Soil: 4 Ways

This article throws light upon the four main ways by which nitrogen is lost from soil. The  ways are: 1. Volatilization Loss 2. De-Nitrification Loss 3. Leaching Loss 4. Used by Soil Microorganisms and Weeds.

Way # 1. Volatilization Loss:

In this chemical reduction process, nitrogen is lost in the gaseous form when urea or ammonium fertilizers are applied on the soil surface. Losses of nitrogen as ammonia is occurred, especially in alkaline soils. High concentration of ammonia (high dose of ammonical or amide fertilizers) is toxic to the nitrification process, resulting in an unusual build-up of nitrites.

Under acid conditions these nitrites are converted to gaseous elemental nitrogen or nitrous oxide, when brought in contact with certain ammonium salts or urea.

It may be represented in the following reaction:

Way # 2. De-Nitrification Loss:

The nitrates may change to gaseous form in the lack of air or by poor drainage. The biochemical reduction of nitrate-nitrogen to gaseous compounds by microorganism is called de-nitrification. The microorganism involved are common anaerobic forms.

Under field conditions, nitrous oxide is the gas lost in largest quantities, although elemental nitrogen is also lost under some conditions. Nitric oxide loss occurs most readily under acid conditions.

Way # 3. Leaching Loss:

The nitrate-nitrogen is lost in drainage or with percolating water. The amount of nitrogen lost depends upon the climate and cultural conditions. In humid region or a water- logged condition, losses of nitrate by leaching are significant. In arid and semi-arid regions, such losses are minimum.

Way # 4. Used by Soil Microorganisms and Weeds:

Soil microorganisms readily assimilate nitrate-nitrogen. If microbes have a ready food supply (organic matter) they utilize the nitrates more rapidly. This is one of the reasons, crops get about one-half the nitrogen added in forms of nitrogenous fertilizer. Weeds may also utilize the nitrate-nitrogen added to the soil (or present in the soil). Therefore, crops may not get nitrogen in full quantity.