Relationship between mineralizable N and hot KCl extractable NH4-N – variability at one site

Abstract

To characterize the N supplying capacity of the soil at a site where a new long-term experiment was being initiated at Scott, Saskatchewan, we soil sampled the site in a systematic manner, taking 160 cores. We used these cores to measure mineralizable N in the 0-7.5 and 7.5-15 cm depths, by a 24-week laboratory incubation at 35°C and optimum moisture. We also extracted NH4-N from the soils by digesting with hot 2M KC1 at l00 C for 4 hr, followed by distillation. Using a geostatistic procedure, and correlation and regression analysis, we demonstrated the existence of a close association between the N supplying power of the soil, estimated by biological vs chemical extraction techniques. Kriging was used to show that these variables were similarly distributed in space over the landscape of the experimental site, and was also closely associated with total soil organic N. We concluded that the hot KCl extracted NH4-N should prove to be a useful index for use in quantifying the N supplying capacity of soils. Further, it may allow more accurate estimates of fertilizer N requirements to be made by soil testing laboratories. As well, this new index may prove useful to scientists interested in researching precision farming because it offers a quick laboratory method of quantifying N supplying capacity of soils and its distribution in the field.