A Comparison of Calcium Carbonate Precipitation and pH Depression on Calcium‐Reduced Ammonia Loss from Surface‐Applied Urea

作者：L. B. Fenn, J. E. Matocha, Ellen L. Wu · 发表于：Soil Science Society of America Journal · 年份：1981 · DOI：10.2136/sssaj1981.03615995004500060023x · 被引用次数：38 · 研究领域：Plant nutrient uptake and metabolism、Soil Carbon and Nitrogen Dynamics、Clay minerals and soil interactions

Abstract The role of calcium (Ca) in reducing ammonia (NH 3 ) loss from soil by way of calcium carbonate (CaCO 3 ) precipitation and soil pH depression was investigated by applying increasing rates of urea with fixed ratios of Ca/N in the laboratory and greenhouse. Soil pH, Ca precipitation, and the rate of hydrolysis of added urea were related to reduction of NH 3 loss. Calcium/nitrogen ratios of 0.25 were equally effective in reducing NH 3 loss independent of N application rates. Higher ratios of Ca/N at at 55 and 110 kg N/ha application rates did not further depress NH 3 loss. At application rates of 550 and 1,100 kg N/ha, Ca levels above a Ca/N ratio of 0.25 resulted in additional large depressions of NH 3 loss. This additional effect was due to a depression in soil pH from increased Ca activity and a dramatically reduced rate of urea hydrolysis. The chemical reaction of Ca with urea was complete at a Ca/N ratio of 0.25. Additional Ca, if added with a high enough rate of urea (550 and 1,100 kg N/ha) remained soluble and reduced the soil pH and was responsible for one half of the total reduction in NH 3 loss. Greenhouse data showed that the addition of Ca with urea increased plant recovery of fertilizer N more than predicted from laboratory data. Nitrogen rates as low as 55 kg/ha, applied in a surface band or as large granules, resulted in improved plant recovery of added N. Broadcast applications at 165 kg N/ha also resulted in good fertilizer N recovery at Ca/N ratios of...