Effect of rate and timing of K on three crops

In a glasshouse experiment, wheat (Triticum aestivum L.), lupin (Lupinus angustifolius L.), and canola (Brassica napus L.) were grown on a yellow sandy earth from the field site where K had never been applied. The Colwell soil extractable K was 26 mg/kg, a soil test level expected to be deficient for the growth and yields of wheat, lupin, and canola. Several levels of K, as sulfate of potash, were applied to give a range of K additions from deficient to an adequate supply of K for dry weight of shoots and grain (or seed yield). The K was applied at four growth stages through the season. The timing of application ranged from 2 to 3 leaves through to boot stage of cereal and bud formation for canola and lupin. ANZ-07