Effect of Potassium Supplies on the Nutritional Status of Maize (Zea mays L.)

The effect of soil potassium (K) supplies on the yield and nutritional status of maize and on interactions between the nutrients was examined in a long-term mineral fertilization experiment on maize. The experiment was set up in 1989 in Hungarian Great Plain, Szarvas on chernozem meadow soil calcareous in the deeper layers, with four levels each of nitrogen (N), phosphorus (P) and potassium (K) supplies. The present paper describes the results of K fertilization in the 7–19th years of the experiment, from 1996 to 2008. The ammonium (NH₄)-lactate (AL) potassium oxide (K₂O) content of the ploughed layer ranged from 200 to 550 mg kg^–1 depending on the K fertilization level. No significant yield surpluses were recorded in any of the 13 years in response to the better K supplies ensured by K fertilizer. The results of leaf analysis indicated that the K concentrations representing satisfactory K supplies at a grain yield level of 10–14 t ha^–1 were 2.3–4.3% at the 5–6-leaf stage and 1.5–2.6% at the beginning of tasselling. When the AL-K₂O content of the soil was above 200–320 mg kg^–1, K– calcium (Ca), K–magnesium (Mg) and K–copper (Cu) antagonism was observed in the nutrient concentrations of the maize leaves in most years. The limit values of satisfactory nutrient supplies for maize in the 5–6-leaf stage and at the beginning of tasselling were 0.25–0.60% for Ca, 0.15–0.40% for Mg, and 7–11 mg kg^–1 and 2–11 mg kg^–1, respectively, for Cu. In dry years the iron (Fe) and zinc (Zn) concentrations of maize leaves declined at higher soil K supply levels.