Influence of pH, exchangeable aluminium and 0.02 M CaCl2-extractable aluminium on the growth and nitrogen-fixing activity of white clover (Trifolium repens) in some New Zealand soils

The effects of soil acidity on the growth and N2-fixing activity of white clover in seven acid topsoils and subsoils of New Zealand were investigated using a glasshouse experiment. The application of phosphate (Ca(H2PO4)2) to the soils resulted in very large increases in white clover growth on all soils. The application of phosphate, as well as increasing P supply, also decreased 0.02 M CaCl2-extractable Al levels, but had little effect on exchangeable Al levels. Where adequate phosphate was applied, increasing rates of lime (CaCO3) resulted in increased plant growth on most soils. N2[C2H2]-fixing activity was increased by the first level of lime for one soil, but generally remained approximately constant or declined slightly at higher rates of lime. Up to the point of maximum yield, white clover top weight was more highly correlated with 0.02 M CaCl2-extractable soil Al than with exchangeable Al or pH. At pH values greater than 5.5, plant yield declined on some soils, apparently because of Zn deficiency. The data suggest that white clover is unlikely to be affected by Al toxicity at 0.02 M CaCl2-extractable Al levels of less than about 3.3 μg g^-1. However, there were differences between soils in apparent plant tolerance to 0.02 M CaCl2-extractable Al, which appeared to be caused by differing C levels in the 0.02 M CaCl2 extracts. © 1988 Kluwer Academic Publishers.

Duke Scholars

Author James F. Reynolds Environmental Sciences and Policy