Soil properties after twenty years of fertilization with different nitrogen sources
1991
Darusman. | Stone, L.R. | Whitney, D.A. | Janssen, K.A. | Long, J.H.
Increased use of N fertilizers during the past 30 yr has been accompanied by a growing concern about their possible negative influence on soil properties. In 1969, research plots were established with fertilizer-N source the treatment variable (NH3, NH4NO3, urea, urea-NH4NO3 Solution, and a no-N check). In October 1988, we sampled the field plots and then examined the status of selected soil physical and chemical properties. Our objective was to determine if differences existed in soil properties between the N-fertilized plots and the no-N check or among the four N-source treatments after 20 annual applications of N. For the soil properties evaluated, we found no significant difference among the four N-source treatments. The 20 yr of N fertilization reduced soil pH significantly, compared with the no-N check, in the surface (0.06-0.14-m) soil layer (pH 5.2 vs. 6.2). Nitrogen fertilization caused an increase in micronutrients (Fe, Cu, and Mn) and a decrease in available P and exchangeable bases (Ca, ML and Na). Compactibility analyses revealed no significant difference in either maximum bulk density or optimum water content for compaction among treatments. Our results show the primary effects of 20 yr of N application have been increased soil acidification and associated changes in nutrient availabilities and increased concentrations of NO3-(-N) and NH4+(-N).
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