A laboratory incubation experiment was conducted to compare the mineralization of N from 15N-labelled soybean (Glycine max L.) tops, vetch (Vicia villosa Roth.) tops and corn (Zea mays L.) stover in six Mollisols from Illinois, and to study the interaction of the applied residue N with the native soil N. From 13 to 41% of the applied N was mineralized during the 4-week incubation (25°C), the proportions decreasing in the order, vetch > corn > soybean, in accordance with their total N content. Mineralization of N from soybean and corn was most rapid in the soil having the highest content of mineral and potentially mineralizable N, whereas mineralization of N from vetch was slowest in this soil. Higher values for the amount of N mineralized were obtained by the difference method than by the isotopic method. However, the values were highly correlated (r = 0.92**), which suggests that the difference method is a satisfactory alternative to the isotopic method in assessing the mineralization of N from applied organic materials. The three plant materials had different effects on the mineralization of soil N, resulting in either a positive or negative added nitrogen interaction (ANI). Negative ANIs were more common with soybean and corn than with vetch, and were attributed to greater immobilization of native mineral N during early stages of decomposition, and to enhanced denitrification of native NO-3 following organic amendment.
ASJC Scopus subject areas
- Soil Science