Assessing chemical methods for estimating mineralizable nitrogen in Saskatchewan soils
An experiment was conducted to correlate the potentially mineralizable nitrogen (NO) in Saskatchewan soils with chemical extractant. An array of soils (129) representing all soil zones, soil textures and crop management practices and varying in soil organic C from 1.0 to 6.3% and pH from 5.1 to 7.8 were used in this study. The two chemical solutions used to extract ammonium (NH4 ) in soil were, hot 2 M KCI and phosphate-borate buffer at pH 11.2. The NH4 extracted with the hot KCI method provided a better index of available N in soil than the phosphate-borate buffer method. The KCI method was highly correlated with net N mineralized over 24 weeks under aerobic conditions at 35 °C. Although, the KCl method was significantly (P < 0.001) correlated with NO (r2 = 0.53**) it was better correlated with the product of No, and the rate constant (k) (initial potential rate of N mineralization) (r2 = 0.80***). The KCl method may not be a good indicator of NO for some soils in the Black soil zones and soils recently fertilized with farmyard manure. Because several studies have shown that N,k is a very good index of the N-supplying power of soils and is closely related to grain yields, we believe that the KCl method may have great potential for use in soil testing labs to make more precise N fertilizer recommendations to producers. This is particularly true for more humid environments where the NO3 test is not appropriate.
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