Browsing by Subject "Arbuscular mycorrhiza"

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  • Pakarinen, Aku; Fritze, Hannu; Timonen, Sari; Kivijarvi, Pirjo; Velmala, Sannakajsa (2021)
    Arbuscular mycorrhizal fungi (AMF) enhance plant phosphorus uptake, increase soil water holding abilities, reduce soil erosion and can protect their hosts from soil-borne pathogens. Hence, AMF play an important part in improving sustainable agricultural practices, and information about the effects of different preceding crop species on the following crop's AMF well-being is crucial for designing crop rotations. We studied onion root and soil microbial diversity and onion root AMF colonization rates after being preceded by three AMF hosting and one non-hosting green manure crop species in a boreal climate organic field. One-season cultivation of different preceding green manure crops did not have a strong effect on AMF colonization or microbial diversity in onion roots nor in the surrounding soil. Onions had high AMF colonization and microbial diversity after all four preceding crops. The overall fungal and bacterial populations of the soil reacted more strongly to seasonal variations than preceding crops. The study suggests that one season is a too short time to influence the AMF community in boreal climate organic fields with conventional tillage. Thus, non-host preceding crops can also be used in rotations, especially together with AMF host crops.
  • Westerling, Kim (Helsingfors universitet, 2011)
    In Finland most of the accumulated phosphorus in the agricultural soils is underutilized and at the same time excess phosphorus in soil is susceptible to leaching. Arbuscular mycorrhiza (AM) has the potential to promote plant phosphorus nutrition and growth, and reduce nutrient leaching. The aim of this study was to investigate the effect of mycorrhizal symbiosis on plant growth and phosphorus nutrition with three different fertilization management practices. The influence of fertilization management history on field AMF population was also studied. To relate the impact on AM to impacts on other soil quality aspects, the effect of the fertilization rates on crop growth and indicators of soil functioning was evaluated. Long term field experiments established in 1965-66 on three sites in Northern Sweden were utilized. Six years’ rotation either with five grass years and a barley year or barley monoculture was treated with recommended (NPK) and double the recommended (2NPK) rate of mineral fertilisation or with farmyard manure (FYM) with a nutrient amount corresponding to the NPK –treatment for 32 years. The effect of three long term practices on the potential AM contribution to crop phosphorus nutrition and growth was studied in a bioassay. To study the impact of longterm management practices on functional properties of AMF, the sterilised soil from the field plots of NPK and FYM treatments was re- and cross-inoculated (5 v-%) with untreated field soil from each of the same treatments. Crop yields were measured in the field and field soil quality was assessed. Benefit from AM in terms of crop phosphorus nutrition and growth was greatest when manure was applied while there were no differences among the mineral fertiliser treatments. There were no statistically significant differences in the bioassay with re- and cross-inoculations. Grass and barley yields were highest when mineral NPK fertiliser was applied at double the recommended rate. Crop performed equally well or better in terms of yield with manure compared to a corresponding nutrient amount in mineral fertilizers. Manure applications seemed to increase soil carbon and nitrogen contents relative to the recommended amount of NPK, yet keeping the plant-available phosphorus concentration liable for leaching at a similarly low level. Thus, enhanced recycling of nutrients through use of farmyard manure to replace mineral NPK fertilisation favoured reliance on AM in phosphorus nutrition of crops with no trade-off in yields, simultaneously enhancing soil quality.
  • Kilpeläinen, Jouni; Aphalo, Pedro J.; Lehto, Tarja (2020)
    Arbuscular mycorrhizal (AM) plants and fungi associate with lower soil organic matter, higher pH, lower phosphorus and higher nitrogen than ectomycorrhizal (EM) ones. However, soil conditions correlate with climatic factors, and we suggest that temperature and humidity have also direct roles in the success of mycorrhiza types. The hypothesis here is that EM perform better at low temperatures than AM, and AM resist drought better than EM. Narrowleaf cottonwood (Populus angustifolia E. James) forms both AM and EM. We grew seedlings in soil at 14, 20 and 26 °C in factorial combinations with adequate watering and a cyclic mild drought for 4 and 7 weeks. As hypothesized, the percent of EM root tips was largest at 14 °C, while the proportional root length with AM was largest at the two higher temperatures. However, unlike expectations, drought increased EM formation slightly, while the AM colonization was lower in the dry treatment. Plant growth was reduced more by low temperature than drought. Root branching was more prominent at low temperature and root length and mass growth at higher temperatures. Soil nutrient availability did not provide a direct explanation to the results, as both soluble soil N and P were the same in 14 and 20 °C, while the change in mycorrhiza colonization took place between these temperatures. Differences in root morphology (root branching vs length) may affect the proportions of the mycorrhiza types at different temperature regimes. The most likely explanation to the differential colonization is that temperature affects AM and EM fungi in a different way. In nature, temperature and humidity regimes are tightly correlated, and temperature as such may be a stronger determinant for the success of mycorrhiza types than has been previously considered. The poorer performance of AM in low-temperature and drought conditions may reflect stress avoidance rather than stress tolerance by AM fungi.