Mineralization of Nitrogen in Organic Soils
1982
Reddy, K. R.
The effect of fluctuating seasonal temperatures on the release of soluble NO⁻₃-N, NH⁺₄-N, soluble organic N (SON), and solube organic C (SOC) into drainage effluent during soil organic matter mineralization was measured on organic soil profiles obtained intact from various locations in Florida. Soil columns were leached once every 25 days, followed by applying a suction of 100 cm. Soil columns were flooded for 25 days each in the months of July and August to simulate normal agronomic practices. Leachate was analyzed for NO⁻₃, NH⁺₄, SON, and SOC. The amounts of N mineralized ranged from 410 to 938 kg N·ha⁻¹·year⁻¹ for cultivated soils and 874 to 1,250 kg·ha⁻¹·year⁻¹ for virgin soils. Nitrate accounted for 48 to 81% of the total N in the effluent, while SON accounted for about 16 to 45% of the total N. Remaining 2 to 7% of the total N in the effluent was NH⁺₄. Soluble organic C in the leachate accounted for about 1,795 to 3,516 kg C·ha⁻¹·year⁻¹. Seasonal fluctuations in temperatures had minimal effects on the release of SON, SOC, and NH⁺₄, but the release of NO⁻₃ was increased with an increase in average daily temperature (9.4 to 30°C) with Q₁₀ values ranging from 1.3 to 1.9. Flooding the organic soils increased the SON and SOC release into the effluents by about two-fold, compared to drained conditions. Total N loss in 1 year as a result of organic matter mineralization was about 1.3 to 4.2% of the total soil organic N.
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