The effect of soil reaction on the growth of young citrus plants. II.

Abstract

Further studies of the effect of soil pH on the growth of young Unshu orange trees were attempted, applying two forms each of nitrogenous and potassium fertilizers.1. The favorable soil pH for the growth of trees based on shoot length, and total fresh and dry weights was 6.23-7.25 in the case of NH4-N and KCl, and 623-7.18 in the case of NH4-N and K2SO4. However, when NO3-N was applied, the growth was nearly the same in most of the plots except the plot of strongly acid soil (nearly pH 4), regardless of the soil pH and the form of potassium fertilizer.2. Total amounts of N, P2O5 and K2O contained in a tree increased as its growth became greater. MgO was however absorbed more abundantly in various plots of NO3-N than in corresponding plots of NH4-N. With lowering soil pH, the total amount of CaO decreased, while that of Mn increased evidently, independently of the growth. The absorption of N and P2O5 in plots of NH4-N was much promoted by an application of K2SO4 than that of KCl.3. A significantly positive correlation existed between the isoelectric point of root tissues, and their buffer capacity became greater with lowering soil pH.