The influence of soil type, salinity and sodicity on ammonia volatilization in soils fertilized with urea [electronic resource].

Includes references.

A laboratory experiment was conducted to study the influence of different soil types, different levels of salinity (3, 20, 40, 100 and 200 meq. L⁻¹.) and sodicity (SAR= 0, 5, 15 , 25 and 50) on ammonia volatilization rates from soils fertilized with urea and incubated at 3±2°C. The soils were an Entisol, Vertisol and Aridisol collected from Sudan. The soil type was found to have a marked effect on ammonia volatilization from the applied urea. However, at all SAR values studied; soil samples have shown an erratic increase or decrease in ammonia volatilization with in creasing salinity level. This was attributed to conflicting effects of salinity and sodicity on ammonia volatilization. High Ca ++ concentration at low SAR and high salinity may cause high displacement of exchangeable ammonium. thus make it vulnerable to volatilization. On the other hand; pH at these conditions was found to be relatively lower as compared to pH of high SAR. a condition that retards the volatilization process. High salinity may also negatively affect the microbial growth and decrease urea hydrolysis to ammonium carbonates which may decrease the overall process of volatilization. Although pH increased with increase in SAR in all soils, this increase seems to have been associated with poor displacement of NH/ by Na + and hence in little ammonia volatilization, with exception of Entisol which showed a significant decrease of NH3 volatilization with increase in SAR. The resolution of the contrasting effect of salts on urea hydrolysis, pH and NH/ adsorption-desorption processes will probably determine the degree of ammonia volatilization from applied urea in saline or saline sodic soils.

Summary in Arabic.

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