Effect of fertiuzers on soil pH and apple trees grown in different soils in the greenhouse

Abstract

The effect of various fertilizers and rates on soil pH, tree growth and mineral uptake has been a concern for fruit tree production. In this study, two acid soils, one nearly neutral soil, and two alkaline soils were used to determine the effect of nitrogen (N) and phosphorus (P) fertilizers on soil pH and tree response in the greenhouse. All of the above soils, except one, contained low levels of available soil phosphorus (5 to 13 ppm) as determined by the sodium bicarbonate test. The moderate and high rates of fertih'zers induced lower soil pH in all soils tested. In one soil of moderate acidity, ammonium sulfate reduced soil pH more than the other N and P fertilizers tested whereas calcium nitrate reduced soil pH only slightly. In most cases, mono‐ammonium phosphate (MAP) fertilizer reduced soil pH slightly more than the other N and P fertilizers tested. Uptake of N and P in apple leaves was higher with increased rates of N and P fertilizers (MAP), but tree growth was not always significantly improved. This indicates a possible reduction of growth with lower pH or high salt concentrations in the soil.