A soil test that predicts N mineralization has long been needed. The first objective was to compare proposed analytical procedures with the N mineralized after an anaerobic incubation. The methods of interest were: i) applying an acid oxidation, ii) analyzing a 1 M KCl extract in the ultraviolet (UV) range before and after NO3 removal, iii) the Illinois soil N test (ISNT), and iv) analyzing near-infrared reflectance (NIR) spectra of soil. The ISNT and UV measurements at 210 and 260 nm after NO3 removal failed to estimate N mineralization. The acid oxidation procedure and the UV measurement at 260 nm before NO3 removal produced acceptable results with R2 values of 0.58 and 0.56, respectively. The NIR procedure performed the best of all methods (R2=0.67). In conclusion, the three aforementioned methods display promise in predicting N mineralization. The second objective was to evaluate if hydrolyzable amino sugar-N (HASN)and methods that estimate HASN predict N mineralization by comparing them with an anaerobic incubation. Methods evaluated to predict HASN were the ISNT, and 2, 5, and 10 M NaOH distillation procedures. Even though the relationship between HASN and anaerobic incubation method was significant there was not a good correlation (R2=0.38). Significant relationships were observed between the ISNT and distillation procedures to predict HASN. In addition, the 2, 5, and 10 M NaOH procedures displayed significant correlations (R2=0.68, 0.67, and 0.76, respectively) with N mineralized during anaerobic incubation, which were better than those, obtained by the ISNT (R2=0.55). When ISNT values were compared to the three distillation techniques highly significant relationships were observed. However, the 10 M NaOH distillation procedure displayed a slope of about one and an intercept near zero. Thus, the 10 M NaOH distillation procedure may be substituted in testing facilities for the ISNT method.
See more of Soils Posters/Reception
See more of The ASA Southern Regional Branch (June 19-21, 2005)