Comparison of Soil Tests for Predicting Nitrogen Minearlization in Southern Idaho Soils.

The development of soil testing methods to accurately determine fertilizer management strategies has led to improvements in agricultural crop production. Soil testing research dates back over 150 years where rapid improvements occurred as advancing chemical instrumentation was developed and used to measure soil nutrients. However, an accurate rapid soil test for nitrogen (N) mineralization has long alluded researchers. This work will largely focus on the resurgence in efforts to determine a rapid soil test to determine N mineralization in soil. Approximately 30 irrigated field sites were sampled in southern Idaho at multiple depths. Rapid soil tests, CO₂ burst and direct steam distillation (DSD), were compared to a 7-d anaerobic incubation. Preliminary results indicate both tests were correlated to N-mineralization but the CO₂ burst had a lower r² ranging from 0.32 to 0.39 in comparison to the DSD (r² ranged from 0.59 to 0.70). Additionally, Pearson correlation coefficients indicated greater correlation using the DSD (r = 0.77-0.84) as compared to the CO₂ burst (r = 0.57-0.62).While the DSD was well correlated to the 7-d anaerobic incubations in southern Idaho soils, the test must be correlated and calibrated with crop response parameters to be useful in Idaho crop production.