Data presentation, interpretation, and communication

Abstract

K, Ca and Mg concentrations in tillering stage winter wheat (Triticum aestivum L.) shoot, as well as acidic (pH 4.65) ammonium‐acetate + EDTA ‐ soluble (LE‐, Lakanen and Erviö, 1971) and neutral ammonium acetate‐ exchangeable (Wanasuria et al., 1981) soil K, Ca and Mg contents were determined for a network of 28‐year‐old National Long‐term Fertilization Trials (NLFT) with different K fertilization rates at eight experimental sites representing various agro‐ecological and soil conditions of Hungary. All the sites had the same fertilization pattern. Correlation between the two soil Ca and the two soil Mg methods, between soil and shoot Ca, and Mg, as well as between shoot K and shoot Ca+Mg contents were evaluated. Close, linear correlations were found between NH₄OAc‐Ca and LE‐Ca and between NH₄OAc‐Mg and LE‐Mg on non‐calcareous soils (r = 0.95). Acidic LE‐extractant dissolved significant amounts of Ca and Mg from the Ca‐ and Mg‐carbonates in the calcareous soils. Neutral NH₄OAc‐Ca values increased with increasing soil calcium carbonate contents. Neutral NH₄OAc‐Mg values, however, were the lowest in the calcareous soils, probably due to the large quantities of Ca²⁺ more strongly adsorbed to the cation exchange sites of the colloids compared to Mg²⁺. Exchangeable K⁺ values were also small in the calcareous soils, although all of the soils were loams with medium clay contents. There was a positive logarithmic correlation between soil LE‐Ca and shoot Ca (R = 0.55), and a quadratic polynomial one between soil LE‐Mg and shoot Mg contents, resp. (R = 0.45). The positive logarithmic correlation between NH₄OAc‐Ca and shoot Ca was even closer (R = 0.60). However, there was no correlation between NH₄OAc‐Mg and shoot Mg values. A close negative, logarithmic correlation was found between wheat shoot K contents and Ca + Mg contents (R = 0.78).