New Zealand Journal of Crop and Horticultural Science abstracts

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Effects of soil nutrient levels on leaf purpling in Hypericum

G. E. Clark

New Zealand Institute for Crop & Food
Research Limited
Pukekohe Research Centre
Cronin Road, RD 1
Pukekohe, New Zealand
email: clarkg@crop.cri.nz

G. K. Burge

New Zealand Institute for Crop & Food
Research Limited
Food Industry Science Centre
Private Bag 11 600
Palmerston North, New Zealand

C. M. Triggs

Department of Statistics
University of Auckland
Private Bag 92 019
Auckland, New Zealand

Abstract  Hypericum is developing as a significant export cut foliage crop in New Zealand, but of concern to growers has been a leaf purpling disorder. The effects of berry removal, four soil potassium (K) levels (0.42, 1.33, 1.89, and 2.59 meq/100 g), and 10 soil K/Mg ratios (from 0.26 to 1.78) on the leaf purpling disorder in hypericum were studied in three experiments. Leaves from a growers property with the disorder had higher K and lower magnesium (Mg) concentrations than leaves without the symptoms. There was no effect of berry removal or retention on the incidence or severity of the disorder. Increasing soil K levels increased leaf purpling scores. The leaves had significantly higher concentrations of K and lower levels of Mg. There is a strong relationship between leaf purpling and the soil K/Mg ratio, and this disorder can be reduced to acceptable levels at ratios less than 0.30.

Keywords  Hypericum; disorder; leaf purpling; nutrition; potassium; magnesium; K/Mg ratio

H03041; Received 17 April 2003; accepted 18 December 2003; Online publication date 15 June 2004
New Zealand Journal of Crop and Horticultural Science, 2004, Vol. 32: 201-207
0014-0671/04/3202-0201 $7.00 © The Royal Society of New Zealand 2004

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