Magnesium nutrition of apple trees I. Preliminary studies

Symptoms of Mg deficiency on apple trees in the Warsaw district, Central Poland are described and illustrated. Results of soil and leaf analyses of deficient and healthy trees and factors affecting Mg deficiency in apples are discussed. Mg deficiency was found mainly in young trees grown on light, sandy or sandy loamy grey-brown podsolic soils; an old trees it was very rare, because of deep root penetration and utilization of Mg from illuvial horizons rich in Mg. Severe Mg deficiency symptoms appeared on old trees, vigorously growing after topworking with Bancroft scions. Low soil and leaf of Mg content a high available potassium to magnesium ratio in the soil and high ratio in the leaves are suggested to be important factors promoting Mg deficiency symptoms. A three years' experiment run on old Bancroft apple trees showed that 400 kg of MgO applied in epsomite to the soil were as effective as 4 sprays of 2% epsomite. Soil or foliar Mg fertilization did not have any significant effect on tree growth, yields, fruit drop and fruit quality