Colonisation of wheat by VA-mycorrhizal fungi was found to be higher on a farm managed in an organic manner than on a conventional neighbour

Abstract

Levels of colonisation by vesicular-arbuscular (VA)-mycorrhizal fungi were compared between adjacent farms, one operated in a conventional manner and the other run according to organic farming principles. Wheat grown on the organic farm was found to have VA-mycorrhizal colonisation levels consistently 2 to 3 times higher than wheat on the conventional farm. Glasshouse and field trials indicated that the lower colonisation levels on the conventional farm were due to continual use of fertiliser containing soluble phosphorus (P). The fertiliser appeared to have an immediate negative effect on the rate of colonisation, and also appeared to have a long term negative effect through maintaining higher levels of soluble P in the soil, and by decreasing inoculum levels. Use of the relatively insoluble reactive rock phosphate fertiliser on the organic farm did not decrease levels of VA-mycorrhizas. Colonisation levels did not vary between wheat varieties, and herbicides and seed dressings were also not found to be having any significant effect on levels of colonisation.

Field Application of the Mycorrhizal Fungus <i>Rhizophagus irregularis</i> Increases the Yield of Wheat Crop and Affects Soil Microbial Functionalities

“…1) Field survey of wheat soils predicted that AMF would have the ability to colonize wheat roots at early stages of crop development [35] [36]. The positive effect of R. irregularis inoculation on wheat development is in accordance with previous studies where it has been shown that this fungal isolate was very efficient on the growth of other plant species in controlled conditions [31] [37] [38] and in field conditions [13].…”

Six-year fertilization modifies the biodiversity of arbuscular mycorrhizal fungi in a temperate steppe in Inner Mongolia

“…The importance of AMF pathway in assimilating P for host plants could be decreased when soil P availability is high, which is universally accompanied with a decline in AM colonization (Smith and Smith, 2011). Several evidences have proved that the extractable soil P concentration increases with a reduction in the percentage of root length colonized by AMF (Jensen and Jakobsen, 1980;Ryan et al, 1994;Kahiluoto et al, 2001). However, we did not find a significant effect of P fertilization on the AMF phylotypes and species compositions.…”

Relation between Soil Health, Wave-like Fluctuations in Microbial Populations, and Soil-borne Plant Disease Management

“…Especially chlorinated pesticides have had negative impacts on microbial diversity (Mas et al, 1996). Although some authors found no differences in soil microbial diversity between organically and conventionally managed soils (Lawlor et al, 2000;Franke-Snyder et al, 2001), most researchers reported a higher biological diversity for organically than for conventionally managed soils with respect to various taxa, namely bacteria (Sivapalan et al, 1993;Drinkwater et al, 1995;Ma¨der et al, 2002;van Diepeningen et al, 2005), arbuscular mycorrhizal fungi (Ryan et al, 1994;Oehl et al, 2003), nematodes (Mulder et al, 2003;van Diepeningen et al, 2005), earthworms (Ma¨der et al, 2002), and arthropods (Drinkwater et al, 1995;Ma¨der et al, 2002). Also, a higher microbial activity (Workneh et al, 1993;Ma¨der et al, 2002) and microbial biomass (Workneh and van Bruggen, 1994;Ma¨der et al, 2002;Mulder et al, 2003) were found in organically managed soils.…”

“…Regular addition of fairly stable organic matter, including solid animal manure, composts of plant and animal origin, and lignified roots of deep-rooted plants such as alfalfa, rye or grass-clover would enhance microbial biomass, activity, and diversity, and food web complexity in soil (Sivapalan et al, 1993;Ryan et al, 1994;Workneh and van Bruggen 1994;Ma¨der et al, 2002;Schjønning et al, 2002;van Diepeningen et al, 2005). It would also enhance suppression of many soil-borne pathogens (van Bruggen, 1995;van Bruggen and Termorshuizen, 2003).…”

“…Reducing the amount of easily available mineral nutrients and soluble carbon compounds by reducing fertilizer applications and the addition of stable carbon sources, would lead to oligotrophication. This promotes mycorrhizal infections, which can also suppress various root diseases (Sharma et al, 1992;Ryan et al, 1994). Whether mycorrhizal infections also occur in wave-like patterns along the roots is not known.…”