If ammoniated nitrogen is applied on the soil surface the losses by volatilizationin alkaline soils are maximized. When nitrogen is incorporated into the soil the nitrogen as ammonium attachs to the clay or organic matter which have overall negative charge. In term of decreasing losses the nitrogen can be applied by being knifed into the soil and applied at the period of beginning of its optimized use. In a crop like maize the knifing of the nitrogen by injector knives are accompanied by till implement that seals the application slot. Going back to ability of clay and organic matter to help the ammonium adsorption the sandy soils might benefit from the utilization of amending soils with clayey and silt sediments which are strategically repatriated into farmer field. The levels of organic matter can be improved by using composts and the use of some fertilizer with compost can markedly reduce the toxicity issues associated with ammoniated products, In terms of losses of ammonia by volatilization the alkaline condition accentuate these losses. When a sulfur product is used strategically the pH in alkaline areas can be used to adjust pH to a 6.7 target level lowering ammonia losses. In alkaline sodic soils in need of Calcium the use of gypsum calcium sulfate can help ameliorate the sodic condition and improve soil permeability. In alkaline soils which high in carbonate liming is to be avoided as it can make issues worse.
Paul Reed Hepperly I thik oxidation of ammonia also responsible for N loss.
Professor Rajani You are probably right that volatilization and oxidation are sources of the losses. In the case of alkaline soils there is a product of sulfur coated urea which when incorporated might be good for lowering losses. In addition losses of nitrogen occur through water by the conversion to nitrate and in anaerobic environment by the denitrification where the nitrate is converted in nitrous oxide. Nitrogen oxide is greenhouse gas of some concern. These potential transformations which are mediated by bacteria can be inhibited by microbial inhibitor products one found commercially is N Serve.
All ammonium compounds in presence of alkali produces volatile ammonia. In alkaline soil, in sub-surface zone may become devoid of oxygen and all oxidised forms then converted into ammonia through microbial mediated reduction process. Depending on the exchange capacity as well as other physico-chemical properties of the soil, this reduced form of ammonia may be released.
Increase amount of organic manure which will hold more water, attract more base cations onto which the nitrate is bound and reduced soil temperature. Then increase moisture regime by irrigation
High moisture, temperature and the presence of large quantity of ammonium ion results ammonia volatolization. Nitrate source of fertlizer will restrict ammonia volatilization. In sodic soil, without alkaline earth carbonates, application of gypsum {recommended dose} and organic matter along with urea incorporation, will reduce volatilization, which is a surface phenomenon.
Management options may be as follows:
Incorporation of urea with equipments and irrigation.
Application of NBPT or an N fertilizer with lower volatilization potential.
Complete avoidance of urea broadcasting.
(For further study kindly refer Landresource dept., Montana University)
Complete avoidance of urea broadcasting, a very good option. Good answer Dr. Pramanick.
Secondly, not only in sodic soils, but a major loss through volatilization occurs in standing rice soils where prilled urea applied in mid August to mid September when temperatures of the standing water goes around 48-49 degrees C and pH of the flood water rises to 9.5 to 10 and even more. Managing standing water is an issue for reducing volatilization.
in continuation, if we look into sodic /alkaline soils, the organic matter is very less and under under strong alkalinity, dissolution of organic matter takes place. Lowering of soil pH with amendments along with long term organic matter additions, may be with bulky organic manures or green manure, specially Sesbania may results into lowering the rate of loss of N through ammonium volatilization, by increasing CEC and incorporation of fertilizer nitrogen.
- Badges
- Science topic
- Similar topics
- Engineering
- Modeling