Soil mineral nitrogen and the rating of CaCl<sub>2</sub> extractable nutrients
Remigiusz, Łukowiak | Przemysław, Barłóg | Witold, Grzebisz
It was assumed that the determination of the mineral nitrogen (N<sub>min</sub>) content in the 0.01 mol/L CaCl<sub>2</sub> could rely on measurements of single form NO<sub>3</sub><sup>–</sup>-N, NH<sub>4</sub><sup>+</sup>-N or both, and even including other extractable nutrients. This hypothesis was verified based on some primary data from 17 fields: ten with oilseed rape and seven with maize as indicatory crops during three consecutive seasons in a production farm in Górzno, Poland. The contents of NO<sub>3</sub><sup>–</sup>-N, NH<sub>4</sub><sup>+</sup>-N, P, K, Mg and pH were measured in soil prior to the spring vegetation start and after a crop harvest (autumn). Phosphorus in spring and NH<sub>4</sub><sup>+</sup>-N in autumn, were variables discriminating against the number of clusters. It was higher in cropping sequences (CSs) with maize than with oilseed rape. The reliability of N<sub>min</sub> determination and distribution between clusters in spring based only on NO<sub>3</sub><sup>–</sup>-N was fully corroborated for maize CSs. In autumn, irrespective of the CS, the decisive factor in N<sub>min</sub> prediction and distribution over clusters was the NH<sub>4</sub><sup>+</sup>-N pool. This study resulted in the rating of CaCl<sub>2</sub> extractable nutrients, indicating their availability status, shortage or excess, on the background of the N<sub>min</sub> temporary rating.
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