II. Responses to rock phosphates

Abstract

Mycorrhizal and non-mycorrhizal clover plants were grown in a sterilised phosphorus-deficient soil, and fertilised with either pelleted Christmas Island ‘C’ grade phosphate rock or with powdered or pelleted Chatham Rise phosphate rock at eight rates ranging from 0 to 2.8 g fertiliser per pot. In a second experiment, ryegrass plants were fertilised with pelleted Chatham Rise rock phosphate. Mycorrhizal inoculation greatly increased shoot growth and phosphorus uptake compared to that of non-mycorrhizal plants at fertiliser rates up to 1.4 g per pot. The recovery of phosphorus fertiliser from soil was generally low with maximum values of 11.3% and 17.2% in soil fertilised with pelleted Christmas Island and Chatham Rise rock phosphates and a maximum of 48.0% in soil fertilised with powdered Chatham Rise rock phosphate.

Keywords:

• mycorrhizal fungi
• Glomus fasciculatus
• Glomus tenuis
• white clover
• rock phosphates
• growth stimulation