Comparing Soil and Tissue Testing of Copper for Early Growth of Wheat

Abstract

About 40% of soils used for agriculture in southwestern Australia (SWA) were acutely copper (Cu) deficient when first cleared, and Cu fertilizer needed to be applied to grow the first wheat (Triticum aestivum L.) crop, the major crop in the region. Tissue testing rather than soil testing is used in SWA to indicate when fertilizer Cu needs to be reapplied to wheat crops. In a glasshouse study using six Cu‐deficient soils from SWA, we compared four Cu soil test procedures as possible alternatives to tissue testing to predict Cu deficiency for wheat. Different critical values were obtained for different soils for all four soil test procedures, indicating separate soil test calibrations would be required for the four procedures for different soils in SWA. By contrast, critical tissue test values in plant parts (young leaves and rest of shoots) were unaffected by soil type. Developing soil Cu test calibrations would be time consuming and costly, and tissue testing has resulted in most deficiency being corrected by fertilizer applications, so there are few Cu‐deficient soils in SWA available to develop the soil test calibrations. Therefore, tissue testing using young leaves is likely to remain the most reliable method for diagnosing Cu deficiency for wheat in SWA and determining when reapplication of fertilizer Cu to soil is required.

Keywords:

• Tissue testing for copper
• soil testing for copper
• youngest leaves

Acknowledgments

Technical assistance was provided by K. G. Adcock. The Chemistry Centre (WA) measured soil properties and soil test Cu. The experiment was done in a glasshouse at the University of Western Australia. Funds for this research were provided by the Western Australian Department of Agriculture.