Influence of Soil pH on the Availability of Added Boron

Abstract

AbstractA Plano silt loam (Typic Argiudoll) with five relatively constant pH levels (4.7, 5.3, 5.8, 6.3, 7.4) was used to study the influence of soil pH on the availability of added B. A greenhouse study was conducted using tall fescue (Festuca arundinacea Schreb. Cv. ‘Kentucky 31’) with five soil pH levels, and four rates of applied B essentially equivalent to 0, 5, 10, and 20 kg/ha, and five herbage harvests. Herbage yields of tall fescue were not affected by either soil pH or B treatments; however, tissue B concentrations ranged from 8 to 739 ppm for the five harvests. Boron uptake by tall fescue was relatively uniform for soil pH levels of 4.7, 5.3, 5.8, and 6.3 within each level of B availability. Recovery percentages of 30 to 50% of the added B by five cuttings of forage indicate a soil fixation of B. Highest recovery percentage was associated with the highest rate of added B. A 2.5‐fold drop in B uptake occurred at pH 7.4 as compared with the other soil pH levels indicating substantial fixation of B. Hot‐water‐soluble B content of the soil generally increased with an increase in pH and with added B. The soluble B test did not predict the low recovery of B at pH 7.4.