How to Minimise Leaching Losses of Nitrogen in Soil?

This article will guide you about how to minimise leaching losses of nitrogen in soil.

Various experimental evidences show that leaching losses of N may be minimised in different soils by following various methods and sources of nitrogen application. Besides, in order to overcome leaching or de-nitrification losses of N, various nitrification inhibitors may be used.

The main function of these inhibitors is to block the oxidation of ammonia to nitrite (NH₃→ NO₂^–) carried out by species of Nitrosomonas, Nitrosocystus, and Nitrosospira.

However, some of the most important inhibitors and their formulae are appended below:

1. Nitrapyrin (2-Chloro-6-[trichloro methyl]) pyridine = N serve

2. ST (2-Sulphanilamide thiazole)

3. Terazole (5-ethoxy-3 trichloro methyl-1, 2, 4 thiazole)

4. AM = 2-amino-4 Chloro-6-trimethyl pyrimidine.

5. KN3 (Potassium azide)

6. Dicyandiamide,

7. Dichlorophenyl succinic amide,

However, among all these inhibitors, the efficiency and behaviour of nitrapyrin in soils in reducing nitrification has been thoroughly studied. Nitrapyrin is rather immobile in the soil and is especially attached to the organic matter.

The degradation of nitrapyrin depends on the degree to which it is adsorbed by soil colloids. The degradation rate is higher in a sandy soil low in organic matter as compared to clay loam soil rich in humus.

Nitrapyrin degradation occurs at a higher rate in soils of neutral pH than in moderate to strong acid soils. The half-life period of nitrapyrin degradation is about 28 days, but this may vary depending on nature of soils and conditions and microbial activity.

Soil accumulations of nitrapyrin and its main metabolic product (6 chloro-picolinic acids) should be avoided as both products can be taken up by the plants and may be toxic to plants. AM (2-amino 4-chloro-6-trimethyl pyrimidine) is soluble in water and liquid ammonia but not soluble in organic solvents. It can be applied @ 5-6 kg ha^-1 and can be adsorbed by soil colloids.

Recently natural inhibitors have been found such as neem which occurs in seeds of Azadiracta indica and Karanjin which is in seeds, leaves and barks of Pongam’a glabra. These natural inhibitors may be very important in India where costs of agro-chemicals are very high.

The losses of N through leaching is less from the split application than that of the N applied entirely as based application under flooded soil conditions.

Besides, the use of slow release nitrogenous fertilizers like urea-super granules, other coated urea fertilizers like sulphur coated, lac coated, neem coated etc. combination of organic materials with inorganic nitrogenous fertilizers, use of nitrification inhibitors etc. may be useful in reading losses of nitrogen.

The basal application of neem coated urea is more effective in controlling the leaching losses of both NH₄⁺ and NO₃—N than the split application of uncoated urea. The presence of sulphur rich fatty acids in neem cake has nitrification inhibition property which ultimately decreased the loss of N through leaching.