Effects of mixed cropping, earthworms ( Pheretima sp.), and arbuscular mycorrhizal fungi ( Glomus mosseae) on plant yield, mycorrhizal colonization rate, soil microbial biomass, and nitrogenase activity of free-living rhizosphere bacteria

• Published in: Pedobiologia 2009-05, Vol.52 (4), p.223-235
• Main Authors: Zarea, Mohammad Javad, Ghalavand, Amir, Goltapeh, Ebrahim Mohammadi, Rejali, Farhad, Zamaniyan, Mohammad
• Format: Article
• Language: English
• Subjects: Earthworm; Glomus mosseae; Mixed cropping; Mycorrhiza; N-uptake; Soil microbial biomass; Trifolium alexandrinum; Trifolium resupinatum
• ISSN: 0031-4056; 1873-1511
• DOI: 10.1016/j.pedobi.2008.10.004

Sustainable agriculture uses nature as the model in designing agricultural systems. Because nature consistently integrates her plants and animals into a diverse landscape, a major tenet of sustainable agriculture is to create and maintain diversity. The effects of earthworm inoculation ( Pheretima sp., Ew), arbuscular mycorrhizal fungi ( Glomus mosseae, AMF) and mixed cropping systems on forage yield, mycorrhizal colonization rate, nitrogenase activity (NA) of free-living rhizosphere bacteria, soil microbial biomass (SMB) carbon, and the growth of clovers were studied at various mixed cropping ratios of berseem clover ( Trifolium alexandrinum L., B) to Persian clover ( Trifolium resupinatum L., P) (B:P=1:0, 3:1, 1:1, and 1:3). The effects of AMF and Ew on plant yield were positive. Mixed cropping gave more stable yields than monoculture. The greatest mycorrhizal colonization rate was observed at a B:P ratio of 1:1 with a combined AM+Ew inoculant. With the AMF+Ew inoculant, the greatest NA of free-living rhizosphere bacteria was observed with B:P=3:1. Although Ew had no significant effect on SMB, AMF increased SMB from 256 to 444 mg carbon kg −1. The greatest SMB (379 mg kg −1) was observed at B:P=1:1. The greatest nitrogen accumulation in the aboveground biomass, 31.5 mg g −1 forage dry matter, was obtained with mixed cropping (B:P=3:1) in the presence of the AMF+Ew inoculant. A combination of AMF, Ew, and mixed cropping increased the yield, mycorrhizal colonization rate, SMB, and nitrogen uptake of the clover plants, confirming the positive effects of diversity on an agriecosystem.