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Building Healthy Soils Fred Magdoff [email protected] The Great Hunger of 2008 Rioting in response to soaring food prices recently has broken out in Egypt, Cameroon, Ivory Coast, Senegal and Ethiopia. In Pakistan and Thailand, army troops have been deployed to deter food theft from fields and warehouses. Soil Degradation Intensive tillage, soil erosion, and insufficient added residues Aggregates break down Soil organic matter decreases Increased erosion by wind and water Surface becomes compacted, crust forms More soil organic matter is lost Crop yields are reduced Hunger and malnutrition result Less soil water storage, less diversity of soil organism, fewer nutrients for plants … it is our work with living soil that provides sustainable alternatives to the triple crises of climate, energy, and food. No matter how many songs on your iPod, cars in your garage, or books on your shelf, it is plants’ ability to capture solar energy that is at the root of it all. Without fertile soil, what is life? —VANDANA SHIVA, 2008 Aggregates after stability test % of aggregates stable to 1.25cm rain/5mins: 2mm sieves Organic management ~70% - high Conventional management ~20% - low Add organic matter Increased biological activity (& diversity) Reduced soil-borne diseases, parasitic nematodes Aggregation increased Decomposition Humus and other Pore structure growth promoting Nutrients improved released substances Harmful substances Improved tilth detoxified and water storage HEALTHY PLANTS carbon dioxide (CO2) (0.04% in the atmosphere) photosynthesis crop and animal residues respiratio n in stems and leaves carbon in soil organic matter root respiration and soil organic matter decomposition crop harvest erosion Overall strategies of ecologically-based agriculture a) create soil & above ground conditions for healthy plants with enhanced defenses b) stress pests c) enhance beneficials Build internal strengths Prevention (of symptoms and consequences of weak into agricultural ecosystem) ecosystem Routine ecologically sound practices during season to keep plants healthy Reactive management Preventive management pre-season through planting time (building internal strengths into the system) 1. Crop/plant selection & planting management; habitat conservation & enhancement of field and surroundings create soil & above ground conditions for healthy plants with enhanced defenses stress pests 2. Build healthy soil (below ground habitat conservation & enhancement) enhance beneficials Building Healthy Soil 1. Add plentiful amounts of organic materials from crop residues (including cover crops) well as offfield organic materials such as animal manures and composts. vs. Building Healthy Soils 2. Keep the soil covered with living vegetation and/or crop residue. Use cover crops or perennial sod cover routinely. Reduce tillage intensity. • Supplies food and habitat for maintaining biodiversity (helps beneficials at expense of pests) • Suppresses weeds, insect, and disease cycles • Helps grow healthier plants because: a) development of better soil tilth b) supplies nutrients and soil holds water better c) lessens compaction d) etc. Building Healthy Soils 3. Use better crop rotations. Building Healthy Soils 4. Reduce tillage intensity. Many different reduced till systems — conservation till, ridge till, zone-till, no-till. Better planters help. Cover crops can help. Building Healthy Soils 5. Use other practices that reduce runoff and erosion. Building Healthy Soils 6. Reduce severity of compaction. Don’t travel on wet soils. A lasting injury is done by ploughing land too wet. S.L. Dana, 1842 Use controlled traffic lanes (“permanent” beds). Better load distribution. Increase organic matter. Etc. Building Healthy Soils 7. Use best management techniques to supply nutrients to plants without degrading the environment. Farm boundary farm-grown crops fertilizers, lime, organic amendment s crops crop residues soil Nutrient Cycles vs. Nutrient Flows leaching, runoff, and volatilizatio n Use Multiple Tactics Reduce tillage Reduce compaction Better nutrient timing, placement, and amounts Cover crops Healthier Crops Better rotations Add various sources of organic materials (crop residues, manures, composts, etc.) Control erosion