Fertilization strategy can affect the estimation of soil nitrogen mineralization potential with chemical methods

Abstract

Our objective was to evaluate if the relationship between quick indices of mineralizable N and soil N mineralization potential (No) is affected by long-term fertilization with inorganic fertilizers (IF) and/or poultry litter (PL). Samples from four long-term research sites that were fertilized with IF, IF+PL, or PL (>10 years) were aerobically incubated for 24 weeks to determine No. Soil No was then related to the results from the Illinois soil test analysis (ISNT), extractions with hot KCl, NaOH, or phosphate-borate (PB), and an anaerobic incubation (Nan). All evaluated chemical methods were correlated with No (R2 > 0.59). However, the models to describe the association between the chemical methods and No differed depending on the fertilizer treatment, due to the inability of chemical indices to estimate the No increase observed in some PL-amended soils. In contrast, the relationship between Nan and No was not affected by fertilization strategy. Chemical indices can lead to the underestimation of soil N mineralization potential in PL-treated soils when the indices are calibrated in IF-amended soils, whereas the biological method Nan predicted No independently from the field’s fertilization history.