Nitrogen Mineralization Under Saline Conditions

Abstract

The conversion of soil nitrogen (N) from its organic into inorganic forms has been the subject of several investigations, but information on N mineralization in saline soil is scanty. The study was therefore carried out to observe trends in N mineralization in saline soils amended with manure and urea. The electrical conductivity (ECe) of saline soils was 0.2 (S0), 4.1 (S1), and 11.4 dSm⁻¹ (S2). The N sources were applied at the rate of 300 kg N ha⁻¹ and incubated for 8 weeks at 25°C. The pattern of N mineralization was a function of both soil salinity and N sources. The amount of NH₄‐N released was significantly higher in S0 than S1 or S2, especially in urea treated soils. The NH₄‐N release varied in the order of urea>manure>control with a peak period of release at the 4th week of incubation. Nitrification of NH₄‐N to NO₃‐N was reduced by salinity treatments. Patterns of NO₃‐N release during incubation were opposite that of NH₄‐N. Total mineralized N was highest in the urea treatment. Manure application increased ECe of soil by 18%.

Keywords:

• Incubation
• manure
• N mineralization
• salinity
• urea

Acknowledgments

The authors are grateful to the Japan Society for the Promotion of Science (JSPS) for supporting the continuation of this research through the first author.