Effect of Ca in the medium on root growth under low pH conditions

Abstract

The effect of Ca in the medium on root growth was studied by using 15 cultivars under low pH conditions. The results are summarized as follows.

1.	Soil culture—Root growth was analyzed by introducing the roots of each cultivar into two soils differently treated (combination of CaCO3-soil and — Ca-soil or CaSO4-soil and — Ca-soil). Roots generally grew well in the CaCO3-soil. Under similar soil pH conditions (4.3–4.6) and with a high content of exchangeable Al in the combination of CaSO4-soil and — Ca-soil, the root of many cultivars grew well in the CaSO4-soil. These results suggest that in acid soil the presence of Ca in the medium exerts a beneficial effect on root growth. However, peanut and soy bean grew better in the — Ca-soil.
2.	Solution culture—In the medium at a low pH (3.5) and/or at a low Ca concentration, the plants in which root growth was adequate usually contained large amounts of K in their roots. The relative root growth of all the plants improved with the increase of the Ca concentration in the medium at a low pH. The K contents in the roots generally increased with the increase of the Ca concentration in the medium at a low pH. In the medium at a low pH, the value of the relative root growth correlated with the index of the K content in the roots of the dicotyledons and with the index of the Ca content in the roots of the gramineous crops at the 0.1 and 5% levels, respectively.
3.	In both the soil and solution cultures under a low pH condition, the root growth of many plants was ameliorated by the increase of the Ca content in the medium, however, the roots of a few plants grew better in a medium with a low content of Ca

Key Words:

• root growth
• Ca concentration
• acid soil
• low pH.