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Quantitative Effects of Nitrogen Fertilizer on the Development and Downward Movement of Soil Acidity in Relation to Level of Fertilization and Crop Removal in a Continuous Corn Cropping System 1
Author(s) -
Pierre W. H.,
Webb J. R.,
Shrader W. D.
Publication year - 1971
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1971.00021962006300020028x
Subject(s) - chemistry , leaching (pedology) , fertilizer , nitrogen , soil water , agronomy , soil ph , zoology , cropping system , crop , nutrient , environmental science , soil science , biology , organic chemistry
The effect of NH 4 NO 3 in a continuous corn cropping system on the depth distribution and amount of soil acidity produced was studied on four medium‐acid, prairie‐derived soils. To avoid the confounding effect of soluble salts, pH determinations were made after preliminary leaching of the soils and also by the 0.01 M CaC1 2 method. The amounts of acidity were measured by determining the quantities of CaCO 3 required to bring the N‐treated plots to the pH of the No‐N plots. With amounts of N ranging from 1,525 to 2,626 kg N/ha no pH changes were found below the 15‐25‐cm layer. However, after a total of 5,600 kg N/ha had been used within 5 years pH changes were found at a depth of 30 to 45 cm. The total amount of acidity developed averaged 35% of the theoretical (3.57 kg CaCO 3 per kilogram N) in the three experiments that received N ranging from a total of 1,525 to 2,626 kg N/ha over 13 to 15 years. In the experiment where 1,120 kg N/ha were used annually, the acidity developed was 60% of theoretical. This larger amount of acidity developed per unit of N with excessive N applications is explained by the lower percentage of fertilizer N recovered by the crop and the higher percentage remaining in the soil or leached as nitrates. With all additions of N, the development of much less than the theoretical amount of acidity is explained in part by the low excess base compared with N in the corn grain and cobs harvested. It is also, evidently, due to relatively large losses of N from the soil without an equivalent loss of bases, and it seems likely that such losses are due largely to denitrification.