Correction of dual phosphorus and zinc deficiencies of linseed ( Linum usitatissimum L.) with cultures of vesicular-arbuscular mycorrhizal fungi

Abstract

A glasshouse experiment demonstrated that cultures of vesicular-arbuscular mycorrhizal fungi (VAMF) can correct dual phosphorus and zinc deficiencies of linseed ( Linum usitatissimum L.) that are typical of long-fallow disorder. Linseed was grown in pots of steamed vertisolic soil from a field site with a history of long-fallow disorder. The soil was inoculated with cultured sppores of several VAMF species in factorial combinations with or without P and Zn fertilizers. Linseed plants without VAMF in steamed soil grew very poorly unless supplied with both P and Zn fertilizers. Inoculation of soil with cultured spores of local VAMF isolates of Glomus mosseae, or a mixture of isolates of G. mosseae and G. etunicatum, markedly improved P and Zn uptake and dry matter accumulation of linseed. Inoculation with spores of an isolate of G. macrocarpum resulted in slower VA-mycorrhizal colonization and poorer shoot growth and seed yield. Non-mycorrhizal plants responded poorly to either P or Zn alone but showed a marked synergistic response to the combination of both elements. My study demonstrates that VAMF are responsible for substantially improving uptake of both P and Zn and increasing growth and seed yield of linseed (99% mycorrhizal dependency). Long-fallowing, which markedly reduces VAMF populations in the soil, can result in dual P and Zn deficiencies in crops that are highly mycorrhizal-dependent. Farming practices that maintain VAMF populations will result in more efficient use of both P and Zn from soil.