Field amelioration of acidic soils in south-east Queensland. II. Effect of amendments on the yield and leaf nutrient composition of maize

Abstract

The yield of maize, grown on acidic soils with various rates of lime, was measured inreplicated field trials at each of 19 sites in south-east Queensland. Treatments comprising single rates of gypsum, phosphogypsum, and calcium silicate (as Portland cement) were incorporated into the trialde sign at selected sites. At 12 of the sites, lime significantly (P < 0·05) increased grain yield. Because Ca was applied as a basal nutrient the lime responses were attributed mainly to the amelioration of Aland/or Mn toxicities and this was supported by the observation that 90% maximum yield was attainedat pH_w values of around 5·0-5·5. Soil pH_w values of around 5·5 would appear to be adequate for optimal maize growth in the region and there was little evidence to support liming to higher pH values.

High lime rates resulted in significant (P < 0·05) grain yield reduction relative to the maximum yield at 3 sites with concomitant soil pH_w values of 6·7, 7·1, and 7·2, but leaf analysis did not provide a conclusive explanation for the yield reductions.

Lime significantly (P < 0·05) increased leaf tissue P concentrations at 6 sites, whereas Zn and Mn concentrations were decreased at 7 and 10 sites, respectively. Across all sites, there were no consistent trends with respect to the effect of lime on N, K, S, and Mg concentrations.

Although gypsum and/or phosphogypsum increased grain yield at 3 sites, there was little evidence that amendments other than lime or dolomite type products would have widespread potential for ameliorating soils where Al and/or Mn toxicities are limiting crop growth in the region.