REACTION OF ZINC WITH SOIL AFFECTING ITS AVAILABILITY TO SUBTERRANEAN CLOVER .2. EFFECT OF SOIL PROPERTIES ON THE RELATIVE EFFECTIVENESS OF APPLIED ZINC

The effect of moist incubation on the availability of applied zinc was examined on a range of Australian soils. Incubating soil with applied zinc decreased the uptake of zinc by subterranean clover and DTPA extractable zinc (ZnD) on all soils relative to freshly applied zinc. On soils where plant growth was increased by zinc application, prior incubation of the soil led to decreased plant growth responses to zinc. The relative effectiveness (RE) of zinc application for subterranean clover growth was measured by dry matter production, uptake of zinc by shoots and ZnD Values obtained by all three methods of determining the RE were closely correlated. The extent of the decline in availability with incubation differed among soils being greater in alkaline soils, in soils with high clay contents, in soils with high levels of organic carbon. and in soils with free calcium carbonate. A multiple linear regression model was used to explain the relationship between the RE and the soil properties (r2 > 0-87). © 1990, CSIRO. All rights reserved.