Mycorrhizal fungi stimulate clover growth in New Zealand hill country soils

Abstract

VESICULAR-ARBUSCULAR mycorrhizal fungi infect most higher plants and usually increase plant growth and phosphorus uptake, especially in infertile soils¹. Mosse^2–4 has shown that the indigenous mycorrhizal fungi in some soils are very infective but much less efficient in stimulating phosphorus uptake and plant growth than selected mycorrhizal fungi maintained in glasshouse pot culture. New Zealand soils have a short history of pastural agriculture (<150 yr) and still range in fertility from very phosphorus-deficient podocarp–broadleaf forest soils to well developed and highly fertile pasture soils. Most hill country pastures consist of introduced grasses and legumes which are invariably mycorrhizal^5,6. These pastures have been developed within the past 100 yr from infertile forest soils in which nearly all plants were mycorrhizal⁷ and many were completely dependent on mycorrhizal infection for phosphate uptake and plant growth^8,9. Many forests are still being cleared and brought into pasture by oversowing with white clover and spreading heavy dressings of superphosphate. It is important to know whether the indigenous mycorrhizal fungi adapted to these infertile forest soils are as effective at stimulating clover growth in highly fertilised pastures as an efficient mycorrhizal fungus such as E₃ (ref. 10), a Glomus species from Mosse's Rothamsted collection.