engleski

Potassium status in soils of the Eastern Croatia

In general, K levels in soils of Croatia is estimated as satisfied. However, K deficiency is found on gleysols situating in Sava river lowland in the Eastern Croatia. By performed soil test, K deficiency is widespread in areas of former Zupanja and Slav. Brod communes. Also, it is widespread in area of Nova Gradiska commune, but probably because of inadequate soil test for these problem soil, soil K status is found as satisfied. Alkaline soil reaction and high Mg concentrations, as well as high clay contents, are additional problems of these soils. Growth retardation and chlorosis of maize and soybean plants were observed when these crops were grown on some drained gleysols. Four field trials (a, b, c and d) with increased K fertilization (in KCl form) to rates either 920 (a), 825 (b), 2220 (c) or 2125 (d) kg K/ha were conducted on soils which are known to produce K deficiency. In the first year of testing, maize grain yields of the control treatment (standard fertilization) were as follows: 4.98 (a), 2.48 (b), 1.75 (c) and 3.81 (d) t/ha, but they were considerably increased by application of the highest K rate (8.96, 7.62, 8.88 and 7.13 t/ha, respectively). The ear-leaf K and Mg status (% in dry matter at beginning of the silking stage: averages of the four trials) were as follows: 0.64% K and 1.82% Mg (standard fertilization), 1.60% K and 1.11% Mg (the highest rate of K application). K-fixation capacities of these soils (wet-fixation procedure; addition 100 mg K to 100 mg soil) were as follows: 71% (a), 76% (b), 81% (c) and 88% (d). K fertilization was very profitable, because the additional expenses were recovered in the first year of testing, but its effects were prolonged into next years. For this reason, under soil stress characterizing K deficiency, we recommend higher K application. Because of strong K fixation, we suggest band K application immediately prior to maize sowing.

potassium; soil; Croatia

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