Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/4/2004
Publication Date: 11/4/2004
Citation: Avila, M., Barak, P., Posner, J.L., Laird, D.A. 2004. Comparative rates of acidification of Midwestern agricultural systems [CD-ROM]. ASA-CSSA-SSSA Annual Meeting Abstracts. Madison, WI.
Technical Abstract: Acidity inputs to soil vary according to nitrogen (N) source and quantity of N received by crops. Reported net acidity inputs of agroecosystems such as legume-based pastures, continuous corn, wheat, and barley, vary from less than 1 to greater than 10 kmol H+/ha/yr. The objectives of this study were: a) quantify and compare the acid/base balance of continuous corn (CS1), corn-soybeans (CS2), and alfalfa-corn (CS4) agroecosystems of Midwestern United States; and b) identify practices that increase or decrease the net acidity inputs to soil in CS1, CS2, and CS4. Total acidity inputs to CS1, CS2, and CS4 averaged 17.5, 10.7, and 13.0 kmol H+/ha/yr. Of this, only ~0.5 kmol/hectare/year was from atmospheric deposition. Net acidity inputs in CS1 and CS2 averaged 4.5 and 4.7 kmol H+/ha/yr when crop residues were harvested while CS4 produced 7.6 kmol/ha/yr. However, crop residue return to soil decreased net acidity inputs to 0.8, 1.3, and 6.5 kmol H+/ha/yr for CS1, CS2, and CS4, respectively. Acidity input by legumes was also dependent upon nitrification of fixed N remaining in the soil after harvest. Use of dairy manure in CS4 provided alkalinity and plant-available nitrate thus limiting biological-N fixation and excess cation uptake commonly observed in N-fixing crops. Lower net acidity inputs resulted from the use of spring pre-plant nitrate-N credits that allowed for reduced N-fertilizer use in corn crops.