Critical potassium concentrations in Trifolium balansae, Medicago murex and Trifolium subterraneum as affected by sampling date

Pinkerton, A.; Randall, P.J. . Div. of Plant Industry

Critical potassium concentrations in Trifolium balansae, Medicago murex and Trifolium subterraneum as affected by sampling date

1994

Pinkerton, A. | Randall, P.J. (Commonwealth Scientific and Industrial Research Organisation, Canberra (Australia). Div. of Plant Industry)

Critical concentrations of K for the diagnosis of K deficiency were derived for tissues of balansa clover (Trifolium balansae) cv. Paradana, murex medic (Medicago murex) cv. Zodiac, and subterranean clover (T. subterraneum) cv. Karridale. The legumes were grown for 2 seasons at 2 sites to which 7 rates of K fertiliser were applied in each season. In all species, critical K concentrations in dry matter were initially high but decreased steadily as the season progressed. Critical values were highest for youngest open leaves (YOL) petioles, and similar for YOL blades and for whole shoots, with good discrimination between deficient and adequately supplied plants for K concentrations in these tissues. The decline in critical K concentrations in DM was related to date and was unaffected by rainfall before sampling, temperature, or sodium concentrations. Critical concentrations in DM of subterranean clover were similar to those in the literature for other cultivars. Critical concentrations in balansa clover agreed with those derived previously from glasshouse experiments. The test for K in petiolar sap was less satisfactory: the decline in critical concentration in sap was less consistent than that in DM, and the critical values for subterranean clover did not agree with published results.

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