THE BIOLOGY OF SOIL HEALTH A PRIMER FOR FARMERS
Our Purpose Today This morning s webinar Introduction: What is soil health? The Biology of Soil Structure The Biology of Fertility The Biology of Disease Suppression The Biology of Soil Carbon Creating healthy soil ecosystems (concepts, principles, practices)
The Soil Food Web
The Soil Food Web is a Community Like our own communities, it organizes itself to optimize conditions for its members To do this, it uses the energy that comes from the above-ground ecosystem For example, the community organizes a soil structure similar to our community infrastructure
The Biology of Soil Diseases.what makes a disease-suppressive soil?
Plant Health Individual plant health dependent on the soil food web Adequate micronutrients Communications Microbial allies Still much still to learn in this area 6
Communications Yuan Yuan Song et al. 2010. Interplant Communication of Tomato Plants through Underground Common Mycorrhizal Networks. PLOS. Gilbert and Johnson. 2015. Plant-mediated apparent effects between mycorrhiza and insect herbivores. Current Opinion in Plant Biology.
Bacterial allies https://www.youtube.com/watch?v=ylsrmwph3gi - Pathogens also can slip through plant-leaf stomata and infect plants. However, this invasion is halted when the beneficial bacterium Bacillus subtilis is present in the soil where the plant is rooted. - The finding was based on tests of approximately 3,000 plants inoculated with a common foliar pathogen during a year-long period. - When a foliar pathogen attacks, the plant recruits Bacillus subtilis to help and also facilitates its multiplication. - The Bacillus subtilis bacteria bind to the plant's roots and invoke signaling pathways to close the stomata. Bais et al., 2012, University of Delaware
Latest Research: Plants Control their Microbiomes Haney and Ausubel, 2015: www.sciencemag.org Review entitled -- Plant Microbiome Blueprints The plant root system, where nutrients are taken up by the host and exposure to environmental microbes occurs, is functionally analogous to the animal gut. In essence: studies are showing that plants release chemicals designed to suppress some microbes and support others. The microbiome produced in this way helps the plant obtain nutrition, suppress disease, and fight off pests Of course, the beneficial microbes must be present in the soil for the plant to enlist their support
Disease Suppression it takes a team Researchers at found that an important fungal pathogen of sugar beets could be controlled by a consortium of 17 beneficial bacteria If all were present in reasonable numbers, the pathogen was not a problem If even one missing, soil was not suppressive The PhyloChip
The Biology of Soil Carbon and its connection to climate and resilience
Climate Regulation How do soils sequester carbon? Used to be thought that soil carbon came solely from organic residues Therefore, to sequester carbon in soils -- leave residues, add manure, compost Now understood that most of the C sequestered comes through plant roots (carbon trading system) Source: Soil and Water Conservation Society 13
Climate Regulation (2) How Fast Can Soils Sequester Carbon? IPCC estimates: 1.1 to 1.8 tonnes of CO 2e per ha per year 2007 study for central Canada: 0.36 to 1.1 tco 2e /ha/yr ECO report Ontario farmer: 4.75 tco 2e /ha/yr Similar (or higher) figures in anecdotal literature Why the difference? US EPA has stated that the average car generates 4.7 tco 2e /yr. Even at lowest IPCC estimate, a 500 ha farm would offsetting the GHG emissions of 117 cars annually. The 4.75 rate would offset the GHGs of 14 505 cars annually.
Compost and Soil Carbon Sequestration Dr. Whendee Silver, UC Berkeley Marin Carbon Project 4000 cu yds of food-waste compost on 100 acres of rangeland 50 per cent increase in forage production Increase of one tonne of C (3.7 t CO 2e ) per ha per year for three years after single application American Carbon Registry Developed offset protocol for application of compost to rangelands NOTE: Soil C not primarily from compost it comes from the SFW!
Conclusion: Creating healthy soil ecosystems --- concepts, principles, practices
Three Important Requirements of a Living Soil Ecosystem Sufficient food/energy A safe home (habitat) Diversity
Above and Below Symbiosis on a Grand Scale Most diagrams show the below-ground ecosystem as a black box put wastes in, get nutrients and CO2 out However, as we have seen, it is much, much more complex (and interesting!) than that These ecosystems NEED each other As land managers (the top dogs up above), we need to guide our upstairs team of organisms to PARTNER EFFECTIVELY with the downstairs team of creatures beneath our feet
Giving and Getting What Healthy Soil Gives Us: Water management Nutrient management Disease & pest suppression What Soil Needs From Us to be Healthy: Energy/Food management Habitat protection Diversity management
Ecological Succession Level of diversity rises until climax stage, then decline slightly
Important Changes During Ecological Succession NPP up or down? Nutrient availability up or down? Nutrient-use efficiency up or down? Soil food web balance? Bacteria Fungus
Important New Findings on Compost, F:B Ratio, and Soil C New scientific support for the idea that we can use compost to improve F:B balance of SFW Dr. David Johnson, University of New Mexico, good results from increasing F:B ratio in compost
Soil Health Principles and Practices How to get the most out of natural systems
Principles NRCS: Keep the soil covered Maximize diversity Minimize soil disturbance Keep live roots in the ground Plus. (from NRCS & other sources) Integrate livestock Use organic amendments wherever possible 24
Principle: Keep the Ground Covered Why? To prevent erosion & topsoil loss To maintain good conditions for the SFW, which include: Moisture Temperature Food for microbes!
Principle: Minimize Soil Disturbance Why? Reduces SOM Damages soil structure by breaking up soil aggregates Disrupts SFW, particularly fungi (lowers F:B ratio)
Principle: Keep Live Roots in the Ground Why? Optimize photosynthesis Feed the SFW Support survival of mycorrhizal fungi
Principle: Maximize Diversity Why? - Crop rotations disrupt pest cycles - Different root lengths improve soil at all depths - Above-ground biodiversity increased leading to better natural pest management, pollination services, etc. Photo Credit: Stefan Zehetner, Huron County, ON - Different plants have different root exudates, leading to greater biodiversity in SFW & greater range of soil functions
Principle: Use Organic Amendments Whenever Feasible How? Use manure, compost Why? Add and protect organic matter Feed the SFW Protect the environment (compost, particularly) 29
Bob Wilt Compost and Compost Tea
Bob Wilt - Blueberries 65 acre blueberry farm near Corvallis, Oregon (Sunset Organics) Conventional until 2004, when he met Elaine Ingham Yield was dropping, disease pressure rising, so he tried her methods on a small area
Bob Wilt (cont d) Then added compost tea Spring a soil drench Every two weeks applied to leaves Compost added every fall to base of plants Tea made from his own partially finished compost after it is fed to worms to make worm castings Virtually no disease or pest pressure, good yields (especially when weather is bad for other growers) High Brix levels (19-20) make his fruit healthier and tastier very high demand for his product
Bob Wilt (cont d) If I talk to anybody, I ll tell them I m a biological farmer, he said. I just get paid to call myself an organic farmer. If you re a good true biological farmer, you re going one to two levels above what most organic farmers do because you re so involved in what s good for the soil, in what the nutrition of the soil is or the life of the soil. http://sunsetvalleyorganicberries.blogspot.ca/2016/03/bob-wiltstalk-from-profitag-winter.html
Town of Wolfville, NS Municipality had previously made decision for parks and recreation department to go organic Making own compost from yard waste, applying to soccer fields Using corn gluten meal to control weeds expensive and mixed results Lots of compaction, bare ground, broad-leaved weeds
Wolfville (cont d) Started using methods to increase ratio fungi in compost Also introduced use of compost tea Used one soccer field as a trial F:B ratio of soil went from 0.1 to 0.6 over two seasons Weed pressure dropped considerably Penetrometer showed significant reduction in compaction Grass grew better, no bare spots Went city-wide with this approach around 2008
Thank you! gmunroe@compost.org