EFFECTS OF ALUMINUM AND CALCIUM ON THE GROWTH OF SUBTERRANEAN CLOVER IN APPALACHIAN SOILS

Publisher Website
Google Scholar
Abstract
We assessed soil-acidity-related limitations to plant growth in limed and unlimed treatments of 13 major hill land soils from the Appalachian region [USA]. Subterranean clover (Trifolium subterraneum L. cv. Mt. Barker) shoot and/or root growth was significantly depressed in unlimed treatments in 9 of the 13 soils. Root and shoot growth was negatively correlated with soil and soil solution Al and positively correlated with soil pH and measures of soil and soil solution Ca. Unlimed soils with < 15% Ca saturation (exchangeable Ca .times. 100/CEC) and > 40% Al saturation (exchangeable Al .times. 100/CEC) generally displayed shoot and root growth that was < 70% of that found in limed treatments of the same soil. A significant inhibition of subterranean clover root growth occurred when soil solution Al3+ activity (.alpha.Al3+) calculated from the GEOCHEM program exceeded 3 .mu.M. The calculated .alpha.Al3+ in soil solution allowed a separation of the soils into toxic and non-toxic groupings, but did not serve as a good predictor of the extent of root growth inhibition. The summation of monomeric Al (Al3+ + hydroxyl-Al species + AlSO4+) activities (.SIGMA. .alpha.monomeric Al) was a better predictor of root growth than any of the individual Al species. Soil solution Ca2+ activity (.alpha.Ca2+) taken alone did not successfully explain subterranean clover shoot and root growth limitations in these soils. The ratio of .alpha.Ca2+/.SIGMA. .alpha.monomeric Al in soil solution offers promise as a means to estimate potential root growth limitations, but additional measurements are needed over a range of .alpha.Ca2+/.SIGMA..alpha.monomeric Al values. In the current study, subterranean clover root growth in unlimed treatment was < 75% of that in limed treatments of the same soil when .alpha.Ca2+/.SIGMA..alpha.monomeric Al was < 50.