Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2002
Publication Date: 7/1/2002
Citation: ZHANG, R., WIENHOLD, B.J. THE EFFECT OF SOIL MOISTURE ON MINERAL NITROGEN, SOIL ELECTRICAL CONDUCTIVITY, AND PH. NUTRIENT CYCLING IN AGROECOSYSTEMS. 2002. V. 63 P. 251-254. Interpretive Summary: Nitrogen is needed by plants in large amounts and is supplied by the soil or as fertilizer. Application of the proper amount of fertilizer would be improved if rapid methods for determining the amount supplied by the soil were available. A laboratory study was conducted to determine if electrical conductivity could accurately and quickly detect changes in soil nitrogen concentration. Soil nitrogen concentration increased as soil water content increased. Changes in soil nitrogen concentration were accurately measured in the field with a hand held electrical conductivity meter and in the laboratory with a bench electrical conductivity meter. Electrical conductivity can be used to measure changes in nitrogen status when other salts are not present.
Technical Abstract: Inorganic N in the soil is the source of N for non-legume plants. Rapid methods for monitoring changes in inorganic N concentrations would be helpful for N nutrient management. The effect of varying soil moisture content on soil mineral N, electrical conductivity (EC), and pH were studied in a laboratory experiment. Soil NO3-N increased as soil water-filled pore (WFPS) increased from 0 to 80 cm3 cm-3. At soil moisture levels greater than 80 cm3 cm-3, NO3-N concentrations decline rapidly and NH4-N concentration increased, likely due to anaerobic conditions existing at higher WFPS levels. Soil pH did not change as soil moisture increased from 100 g kg-1 to 400 g kg-1 and increased from 6.2 to 6.6 at higher levels of soil moisture. Soil EC was correlated with soil mineral N concentration when measured in situ with a portable EC meter (R2 = 0.85) or in the laboratory as 1:1 soil water slurries (R2 = 0.92). Results suggest that EC can be used to rapidly detect changes in soil inorganic N status in soils where salts and free carbonates are not present in large amounts.