Crop response to amendments on two high manganese soils in southeast Queensland

Abstract

Although the existence of strongly acidic soils in Queensland has been recognised for some time there have been few reports of manganese (Mn) toxicity in the soils of the region. Laboratory and glasshouse experiments identified the existence of Mn toxicity at two sites (Alfisols) and field trials were established to evaluate selected amendments on a range of crops. Various rates of lime, and single rates of gypsum, dolomite and a calcium silicate were incorporated into the 0–10 cm soil depth. One site was cropped to barley and the other site was cropped successively with soybean, peanut, soybean and barley. Root growth bioassays indicated the absence of phytotoxic aluminium (Al) at each site, whereas both sites had high levels of extractable (0.01 M CaCl2) Mn in the 0–10 cm depth (52 and 24 mg kg-1). All amendments significantly (p > 0.05) increased the yield of crops at both sites. Relative grain yield of barley (both sites) was correlated (R2 — 0.89) with Mn concentration in whole tops and it is suggested that Mn toxicity was a limitation to yield at both sites.