Diagnosis of maize yield response to lime in some weathered acidic soils

Abstract

The grain yield of maize (Zea mays L. cv Pioneer 3270) grown with various rates of lime at each of 18 sites was measured in replicated field trials throughout southern Queensland, Australia. All of the soils were acidic (pHw range 4.2 to 6.1), Al saturation ranged from >1 to 57%, and extractable Mn (0.01 M CaCl2) ranged from 1 to 112 mg kg-1. At 12 of the 18 sites lime significantly (p=0.05) increased grain yield. Plant analysis suggested that Mn toxicity was present at a number of sites. Results from a short-term root growth bioassay for Al toxicity in soil solution were well correlated with relative yield when one low-Al, high-Mn site was excluded. The results indicate that, at responsive sites, either Al toxicity or Mn toxicity or a combination of both was limiting yield. Across all sites, a combination of 0.01 M CaCl2 extractable Al and Mn accounted for 71% of the variation in relative grain yield. Of the single index measurements, soil and soil solution pH were the most highly correlated with relative grain yield. It appears that pH integrates the combined effects of Al and Mn toxicities.