Soil Moisture and Temperature Effects on Nitrogen Mineralization from Soil with or without Crop Residue.

Soil moisture and temperature effects on nitrogen mineralization from soil with or without crop residue

The rate at which nitrogen is released from soil organic matter and crop residue is controlled by the soil environment, especially temperature and moisture. High tunnel vegetable production is increasing in popularity because of the price premiums possible with season extension. However, there is little relevant research and practical information about nitrogen availability from soil organic matter and amended organic fertilizer in high tunnel agricultural systems. Soil samples were collected from northern West Virginia (mapped as Gilpin silt loams) and amended with ground alfalfa (100mg kg^-1) and incubated at four temperatures (2°C, 10°C, 20°C, 30°C) and five gravimetric water contents (GWC) (15%, 20%, 25%, 30% and 35%) in a completely randomized factorial design with three replications. Net cumulative mineralized nitrogen was measured by determining ammonium-N and nitrate-N periodically over 12 weeks. A first-order exponential model was fit to the measured mineral N versus incubation week for each temperature/water content combination. Results showed that net nitrogen release from soil organic matter ranged from 0.1% to 7.46% of total N (2.1 to 162.31 mg kg^-1) and from soil organic matter and crop residue ranged from -0.35% to 7.33% of total N (-8.49 to 177.1 mg kg^-1). A rather good fit was obtained under most incubation conditions. The sensitivity to temperature was maximal at 35℃ of Q₁₀ Arrhenius model and at 10℃ of modified Q₁₀ Arrhenius model. Three models used (parabolic, semi logarithmic and Gaussian function) fit well for most treatments. The optimal soil water content for nitrogen mineralization was between 25% and 35% GWC. Maximum nitrogen mineralization rate of this high tunnel agriculture system could be obtained at 35℃ and 25% to 35% gravimetric water content. The model and resulting nitrogen fertilization decisions could be improved by considering soil bulk density and the use of undisturbed soil samples.