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 System¹

Abstract

The effect of NH4NO3 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 CaC12 method. The amounts of acidity were measured by determining the quantities of CaCO3 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 CaCO3 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.

Processes of soil acidification during nitrogen cycling with emphasis on legume based pastures

“…4). Thus the amount of acidity entering and remaining in the soil from ammoniacal N sources depends largely on the relative magnitudes of these two processes (Pierre et al, 1971). One mole of H + ions are consumed per mole of NO 3 reduced to N 2.…”

Comparison of Physicochemical Properties of Soils under Contrasting Land Use Systems in Southwestern Nigeria

“…In general, N fertilizers affect soil acidity because of the preferential uptake of nitrate-N to bases by most crops and the excretion of hydroxide ions to balance the charge reduces acidity (Jolley & Pierre 1977, Pierre et al 1971. Juo et al (1995aJuo et al ( , 1995bJuo et al ( , 1996 reported soil acidification followed by a considerable decline of exchangeable Ca in the topsoil horizons of the Egbeda series under continuous maize-based systems, which would arise from nutrient removal by crop harvest (Jaiyeoba 1995, Sharma et al 2009), application of ammoniacal fertilizers and nitrification of applied N (Stumpe & Vlek 1991).…”

No‐till liming effects on soil‐pH, corn grain yield and earleaf nutrient content

“…Analysis of variance confirmed that this soil-pH change could be attributed to liming (Table 3). Since soil acidity penetrates soil very slowly (18), the most intense acidity would be expected to be on or near the soil surface. Due to the very rapid increase in pH within the 0-5 cm interval, surface liming appears to have corrected the intense surface acidity within two months.…”

“…Timely broadcasts of limestone onto the soil surface will raise surface soil-pH to acceptible levels and will maintain these levels despite annual applications of ammonium fertilizers (4). If high rates of fertilizers are applied onto continuous corn without accompanying lime applications, surface acidity can become severe and acidity may penetrate deeper than five cm (18).…”