Studies on the soil fertility of apple orchard

Abstract

The study was conducted to find the relationship between the incidence of bitter pit and the exchangeable cations in soil of apple orchards which divided into three groups; (group A), severely affected, (group B) slightly affected, (group C) unaffected by bitter pit. Results were as follows;(1) Low exchangeable calcium, particularly low calcium saturation was associated with increased bitter pit, and calcium saturations in 20cm-40cm depth of group A, B and C were 7.4, 22.2 and 31.0 per cent, respectively.(2) The characteristics of ability of cation exchange measured as selective adsorption of NH4 and Ca, releasing Ca by 0.002N-acetic acid and decline of CEC by lowering pH were different in each soil, but no relations were found between the occurrence of bitter pit and the characteristics of the soil in three groups.(3) From these results, the following indication would be applied to soil survey of apple orchards which was fertilized nitrogen at the rate of 15kg per 10 ares.i) The orchard soil contained lower calcium than 10 per cent of calcium saturation.……Very favorable to occurrence of bitter pit.ii) The orchard soil contained higher calcium than about 20 per cent of calcuim saturation, and than two or three times as much as the total of magnesium and potassium.……Unfavorable to occurrence of bitter pit.iii) The orchard soil contained same or lower. quantity of the calcium than the total of magnesium and potassium, though calcium saturation is above 10 per cent.……Favorable to occurrence. of bitter pit with dependent on other factors.