Evaluation of a nitrogen availability test

Abstract

To evaluate a N availability test, we plotted corn (Zea mays L.) silage yields and N contents from several sites in Pennsylvania and Vermont against the total estimated available N (TEAN). Field N mineralization was estimated by using an empirical laboratory‐derived relationship between mineralized‐N (N_m) and the NH₄‐N released by autoclaving (N_i). TEAN was calculated by summing estimated mineralized‐N of soil samples taken to 15 cm plus added inorganic‐N. By using a statistical procedure, we divided the data into two response populations with the critical value of 13.3 kg TEAN/ton maximum yield. Further field testing of the autoclaving N availability index is needed.