Effect of different potassium soil levels and forms of potassium fertilizers on micro-elemetal nutrion status of apple trees in early fruition period

Abstract

The experiment was established in the spring of 1999 on grey brown podsolic soil formed from boulder clay. Apple trees of cv. Golden Delicious were planted on rootstock at 3.5×1.2 m (2381 trees⋅ha -1 ). The first factor in the experiment consisted of the levels of potassium in the arable soil layer: 120, 160 and 200 mg K⋅kg -1 of soil d.m., on the basis of annual chemical analyses and determined by universal method. The second factor comprised three forms of potassium fertilizers: potassium chloride (KCl-60%), potassium sulphate (K 2 SO 4 ) and potassium nitrate (KNO 3 ). Each year the analyses of macro- and microelements in the soil and leaves were made. The increase in available potassium levels from 120 to 200 mg K⋅kg -1 of soil d.m did not have influence on the content of available forms of iron, manganese, zinc, copper and boron in the herbicide fallow strips in the tree rows or in the arable (0-20 cm) and subarable (20-40 cm)soil layers. Application of potassium sulphate fertilizer caused a significant increase in the content of zinc in herbicide strips in both soil layers compared with potassium chloride and potassium nitrate. Different potassium fertilizer forms did not cause any significant changes in amounts of available forms of iron, manganese, copper and boron.