Sustainable Farming for Biologically Active Soils

Healthy soils are the foundation and future of sustainable farming. An abundance of beneficial soil microbes, such as symbiotic fungi and bacteria, is the cornerstone of this foundation.
The services rendered by soil microbes are critical to plant health. They include solubilisation, acquisition and transport of nutrients, protection from stresses such as drought and pathogens, as well as boosting the plants’ immune system and water use efficiency. One particularly important and well-studied group of microbes is that of arbuscular mycorrhizal fungi (AMF). This remarkable fungus associates with over 80% of all land plants and 90% of all crop plants. Fossil evidence proves the existence of this symbiosis for over 460 million years. By growing into the root, as well as accessing large areas of soil around the plant, the fungus effectively increases the uptake surface area of plant roots up to 700 times. Additionally, plant defence mechanisms are improved by the partnership. Put simply, plants colonised by AMF are healthier and significantly more efficient at collecting water and nutrients from the soil.
Plant Growth Promoting Rhizobacteria (PGPR) are another group of important soil microorganisms. This type of bacteria has the ability to fix atmospheric Nitrogen and unlock soil bound Phosphorus, allowing subsequent transport to host plants by AMF. Additionally, PGPR further support a robust plant immune system for healthier crops and produce phytohormones such as auxins and cytokinins, aiding growth and development of plants. Conventional farming techniques can disrupt ecosystem stability and deplete soils of beneficial biological components. Such detrimental techniques include soil disruption (ploughing), fallow periods and cropping with non-mycorrhizal plants, as well application of certain agro-chemicals.

Conservation Agriculture, which includes no-till practices, continuous crop cover and crop diversification is in direct support of the maintenance of a healthy balance of soil biology. But even within this system certain conditions can disrupt soil ecosystem balance and biodiversity. This includes the occasional need for ploughing to address for example compaction or problematic weed populations. Likewise it may be desirable or necessary to grow non-mycorrhizal plants, either as main cash- or cover-crops.
Plants that are unable to form the symbiotic relationship with AMF include those belonging to the families of Brassicaceae and Ameranthaceae amongst a few other minor groups. Oilseed rape is one important crop that falls into this category, along with mustard, a frequently used brassica cover crop. Other examples of commercially valuable nonmycorrhizal crops are all types of beet, which belong to the Goosefoot family of plants (Ameranthaceae). Some pesticides and in particular fungicides are known to negatively impact AMF.
To address these issues, PlantWorks Ltd, based at Kent Science Park have developed the SMART ROTATIONS range of biological inoculants to reintroduce and restore microbial balance in arable soils. The product range include UK grown AMF and PGPR. PlantWorks’ production is based around extensive research and all products are thoroughly evaluated in laboratory and field trials before launch. A significant discovery from the company’s research is that PGPR require careful selection and blending to suit specific crop types. This is in stark contrast to most other bacterial products, which claim beneficial effects from broad and generalist mixes of bacterial species.
When using AMF, inoculation should take place at time of planting and in combination with a suitable host plant. In order to gain the most benefits from this type of treatment, careful crop management is recommended. Crop rotations that support the maintenance of AMF should be planned along with the use of cover crops and minimal soil disturbance. As a general rule, using a wider range of plant species in cover crops will enhance microbial biodiversity. Cover crop mixes that include a number of different plant species, and particularly legumes, are most effective at building up and restoring AMF communities. The use of inoculation in cover crops can help to not only restore soils after fallow periods or non-mycorrhizal crops, but can also serve to build up soil biology for follow-on cash crops.

PlantWorks can offer expert advice on the best cover crop plant species to support mycorrhizal development and work in partnership with a number of seed companies, which can offer suitable seed mixes blended with AMF granular inoculum.
When planting a non-mycorrhizal crop is desirable or unavoidable, inoculation with a preparation of PGPR can help to maintain biological diversity as well as supporting crop growth and productivity. The mix of bacteria used should be tailored to the treated crops to give optimal support. To speed up recovery and re-establishment of AMF this should then be followed by a highly mycorrhizal crop, with the option of treating this with a mycorrhizal inoculum. PGPR can also be used in conjunction with AMF or by themselves on mycorrhizal crops to achieve improved plant health and yields. PlantWorks products are available for a range of arable and field vegetable crops.
Soil ecosystems with a large amount of microbial biodiversity are the best foundation for successful and sustainable farming. The use of considered farming techniques coupled with carefully planned crop rotations and quality inocula can help to maintain and build such balanced ecosystems.

Cavagnaro et al, 2015

Water and nutrient uptake effects of AM fungi. These benefits are further enhanced in the presence of plant growth promoting bacteria.

About PlantWorks:

PlantWorks is a leading horticultural and agriculture research company specialising in the manufacture of soil microbes for application in sustainable food production. The company has activities embracing the production of Arbuscular Mycorrizal Fungi, Plant Growth Promoting Rhizobacteria (PGPR) and various plant stimulating endophytes. Operating from two sites at Kent Science Park and East Malling Research the company works with many of the UK’s leading agronomy and academic partners to refine, demonstrate and ultimate make available to market the very best beneficial soil biology.
In 2014 PlantWorks commenced its farming programme that has seen it collaborate in joint research and trials programmes with the country’s leading agriculture research stations as well as many of the UK’s leading agronomy companies and directly with farming groups. This work has yielded the development of the SMART ROTATIONS programme, and associated products, that support the general concept of maintaining high levels of microbial activity in soil to increase natural plant efficiency, consequently reducing fertigation requirements and enhancing natural plant health and defences.

Jamie Stotzka, Consultant Bioagronomist T – 01795 411 527 M – 07990 042 473