Role of organic amendments on enhanced bioremediation of heavy metal(loid) contaminated soils

Arbuscular mycorrhizal fungi and organic farming

Complex relationships exist between different components of the organic farm and the quantity and quality of the end products depend on the functioning of the whole system. As such, it is very difficult to isolate soil fertility from production and environmental aspects of the system. Crop rotation is the central tool that integrates the maintenance and development of soil fertility with different aspects of crop and livestock production in organic systems. Nutrient supply to crops depends on the use of legumes to add nitrogen to the system and limited inputs of supplementary nutrients, added in acceptable forms. Manures and crop residues are carefully managed to recycle nutrients around the farm. Management of soil organic matter, primarily through the use of short-term leys, helps ensure good soil structure and biological activity, important for nutrient supply, health and productivity of both crops and livestock. Carefully planned diverse rotations help reduce the incidence of pests and diseases and allow for cultural methods of weed control. As a result of the complex interactions between different system components, fertility management in organic farming relies on a long-term integrated approach rather than the more short-term very targeted solutions common in conventional agriculture.

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Managing soil fertility in organic farming systems

Arbuscular mycorrhizal fungi act as biostimulants in horticultural crops

Sustainable farming systems strive to minimise the use of synthetic pesticides and to optimise the use of alternative management strategies to control soil-borne pathogens. Arbuscular mycorrhizal (AM) fungi are ubiquitous in nature and constitute an integral component of terrestrial ecosystems, forming symbiotic associations with plant root systems of over 80% of all terrestrial plant species, including many agronomically important species. AM fungi are particularly important in organic and/or sustainable farming systems that rely on biological processes rather than agrochemicals to control plant diseases. Of particular importance is the bioprotection conferred to plants against many soil-borne pathogens such as species of Aphanomyces, Cylindrocladium, Fusarium, Macrophomina, Phytophthora, Pythium, Rhizoctonia, Sclerotinium, Verticillium and Thielaviopsis and various nematodes by AM fungal colonisation of the plant root. However, the exact mechanisms by which AM fungal colonisation confers the protective effect are not completely understood, but a greater understanding of these beneficial interactions is necessary for the exploitation of AM fungi within organic and/or sustainable farming systems. In this review, we aim to discuss the potential mechanisms by which AM fungi may contribute to bioprotection against plant soil-borne pathogens. Bioprotection within AM fungal-colonised plants is the outcome of complex interactions between plants, pathogens and AM fungi. The use of molecular tools in the study of these multifaceted interactions may aid the optimisation of the bioprotective responses and their utility within sustainable farming systems.

The potential role of arbuscular mycorrhizal (AM) fungi in the bioprotection of plants against soil-borne pathogens in organic and/or other sustainable farming systems.

From 1993 to 2001, a maize-vegetable-wheat rotation was compared using either 1) composts, 2) manure, or 3) synthetic fertilizer for nitrogen nutrient input From 1993 to 1998, red clover (Trifolium pratense L) and crimson clover (Trifolium incarnatum L) were used as an annual winter legume cover crop prior to maize production From 1999 to 2001, hairy vetch (Vicia villosa Roth) served as the legume green manure nitrogen (N) source for maize In this rotation, wheat depended entirely on residual N that remained in the soil after maize and vegetable (pepper and potato) production Vegetables received either compost, manure, or fertilizer N inputs Raw dairy manure stimulated the highest overall maize yields of 7,395 kg/ha (approximately 140 bushels per acre) This exceeded the Berks County mean yield of about 107 bushels per acre from 1994 to 2001 When hairy vetch replaced clover as the winter green manure cover crop, maize yields rose in three of the four treatments (approximately 500-1,300 kg/ha, or 

http://www.donlotter.net/CSU_CUT_Compost.pdf

Compost, Manure and Synthetic Fertilizer Influences Crop Yields, Soil Properties, Nitrate Leaching and Crop Nutrient Content

Effect of compost addition and crop rotation point upon VAM fungi

Arbuscular mycorrhizal (AM) fungi are potentially important tools in agricultural systems that reduce or eliminate chemical inputs common in modem agriculture. We tested the response of potato (Solanum tuberosum L. cv. Superior) to inoculation with AM fungi in a field with very high available P (375 μg g−l soil) in two growing seasons. Inoculation treatments included a commercially available inoculum containing Glomus intraradices, mixed species inocula produced on-farm in mixtures of compost and vermiculite, and a control treatment consisting of a freshly prepared compost and vermiculite mixture. In addition, two farming systems were imposed: conventional chemical fertilizers or dairy manure composted with leaves were applied to meet recommended nutrient requirements. Yields of tubers on a fresh weight basis in the first year were significantly increased by AM fungus inoculum, 33% under conventional fertilizer application and 45% with compost addition vs. controls in each system. The response to ...

Inoculation with Arbuscular Mycorrhizal Fungi Increases the Yield of Potatoes in a High P Soil

On-farm production of AM fungus inoculum in mixtures of compost and vermiculite.

Arbuscular mycorrhizal [AM] fungi are mutualistic symbionts that impart a number of benefits to host plants, any one of which can make them important contributors to productivity of alternative agricultural systems. Inoculation of vegetable seedlings prior to outplanting is economically feasible. One of three inoculation treatments was imposed upon Capsicum annuum L. cv. Camelot seedlings: (1) Glomus intraradices, (2) a mixed inoculum of Glomus mosseae, Glomus etunicatum and Gigaspora rosea, and (3) uninoculated controls. Plants were transplanted into high P soil field plots that received either composted dairy cow manure or conventional chemical fertilizer. There were no significant differences in yield between nutrient amendments, but inoculation with AM fungi significantly affected fruit yield. The mixed inocula increased yields relative to controls by 14 to 23% in plots amended with compost and 34% one year with chemical fertilizers. Glomus intraradices depressed seedling growth relative to c...

Carolyn Reider

Papers

Compost, Manure and Synthetic Fertilizer Influences Crop Yields, Soil Properties, Nitrate Leaching and Crop Nutrient Content

Effect of compost addition and crop rotation point upon VAM fungi

Inoculation with Arbuscular Mycorrhizal Fungi Increases the Yield of Potatoes in a High P Soil

On-farm production of AM fungus inoculum in mixtures of compost and vermiculite.

Inoculation with Mycorrhizal Fungi Increases the Yield of Green Peppers in a High P Soil