CALCIUM DEFICIENCY OF WHEAT GROWN IN ACIDIC SANDY SOIL FROM SOUTHWESTERN AUSTRALIA

Abstract

Calcium (Ca) deficiency has been associated with acidic very sandy soils that are widespread in Southwestern Australia (WA). There are no documented reports of Ca deficiency of cereals grown in the field. However, there is a possibility that Ca deficiency could be observed on the acidic very sandy soils of WA, particular where fertilizers low in Ca concentration are used. For previously unfertilized sandy soil collected from under indigenous remnant vegetation in WA, there was no effect on yield of dried shoots of wheat (Triticum aestivum L.) due to addition of fertilizer Ca (0 up to 480 mg Ca/pot) to either the topsoil (top 10 cm of soil, pH 4.6) (1:5 soil 0.01 M CaCl2, w/v) or subsoil (10–20 cm soil, pH 5.1). However, application of fertilizer Ca increased grain yields, by about 12% for the topsoil and up to about tenfold for the subsoil. For the subsoil, no grain was produced on the nil Ca treatment; about 0.16 g of grain was produced per plant at the second level of applied Ca (60 mg Ca/pot), and about 1.6 g of grain produced per plant at the highest amount of Ca (480 mg Ca/pot), a ten-fold increase in grain production. For the topsoil, grain yield for the highest level of Ca (480 mg Ca/pot) applied was about 1.8 times the amount of grain produced for the nil Ca treatment. The Ca concentration (% Ca) in dried shoots and grain increased with the addition of Ca to both the surface and subsoil. The Ca concentration in the dried tops declined with age of the wheat for both soils. For example, % Ca declined from 0.3% at GS25 to 0.1% at maturity. The highest Ca concentration in dried shoots at harvest always produced the largest amount of grain. There was no grain yield plateau reached in our study so critical concentrations of Ca within the plant tops for grain yield could not be determined.