Growth and Yield of Cowpea as Influenced by Changes in Arbuscular Mycorrhiza in Response to Organic Manuring

Abstract

We studied spore populations of arbuscular mycorrhizal (AM) fungi, mycorrhiza formation, and the growth and yield of cowpea [Vigna unguiculata (L.) Walp] grown in soils amended with sunnhemp (Crotalaria juncea L.), pongamia [Pongamia pinnata (L.) Pierre], cow dung and sheep manure. Spore populations and colonization of cowpea roots by AM fungi were higher in soils amended with organic manure than in non‐amended soils. The effects of organic amendment on cowpea growth, nutrient uptake and yield varied with the type of organic amendment. These responses to organic amendment were strongly related to changes in AM colonization levels and spore populations. Cowpea growth and yield were positively related to spore populations of Glomus aggregatum, G. geosporum and Scutellospora calospora, but were negatively correlated to spore populations of Acaulospora scrobiculata and G. sinuosum. We suggest that changes in the growth and yield of cowpea in response to organic amendment are a result of the differential effects of the types of amendment on the proliferation of different AM fungi within the community.