Chris Thoreau March 3, 2012
Introducing Soil Cultivation What is cultivation? Cultivating Machines Hand Tools Cultivation for Small-Scale Farmers Consistency and Plasticity Mycorrhizal fungi Effect of Cultivation and Loss of Soil Structure Challenges in Cultivation Reduction No-till soil management
Soil Cultivation: Any intentional mechanical disturbance of the soil using machinery or hands tools With a broad range of implements: Digging Fork Broad Fork Rototiller Plough For a broad range of purposes: Weeding Bed Prep. Cover Crops Break Ground
Soil Cultivation: Any intentional mechanical disturbance of the soil using machinery or hands tools Our Focus: Soil conditioning implements which Condition soil for planting Incorporate cover crops Alleviate compaction
Why Do We Cultivate? Breaking ground Incorporate manure, compost, plant residues, amendments Building soil tilth/structure Reduce compaction Seed bed preparation Weed/vegetation control
Cultivation needs change over time and space Cultivation changes throughout the season Cultivation changes through the life of a farm Change in cropping area Change in crops Change in growing methods Cultivation changes with farmer experience
Cultivation Considerations Cultivation is a tool to manage and improve soil conditions Structure Drainage Soil Depth Cultivation methods need to correspond with sustainability goals No cultivation activity does just one thing Cultivation goal: reduce cultivation!
Cultivation Considerations Cultivating for one purpose can be counter productive towards another Seed bed tillage can increase compaction and affect drainage All cultivation can increase weed pressure by bringing weed seeds to the soil surface to germinate
Mouldboard/Furrow Plow Inverts the soil Discing Slices/Inverts the soil Rotovator Grinds up the soil Chisel Plow Deep cultivation Spading Tool Gentler cover crop incorporation
These implements require a machine/tractor to power them so choose the implements that are best for your scale of operation Not sure what is best? Hire someone to do your primary cultivation (breaking ground/incorporating cover crops) for you.
Methods are often used together Mouldboard Plow Discing Spading Rotovator Mouldboard Plow Chisel Plow Disc/Rotovator Rotavator/Spading Roller
Small-scale farmers tend to use: Spading machine on tractor Rotavator on tractor Walk behind tractor Rototiller Hand tools (e.g., Broadfork) Often combine machines with hand tools for prepping seed bed A small tractor is a very versatile machine that can perform a multitude of tasks, but can be pricey and require care! The rototiller and walk-behind tractor are popular machines for small-scale farmers due to their smaller size and lower cost
Rototiller Front and rear tine models Rear tine models preferred for larger scale
Walk-behind Tractor Larger version of rototiller But has variety of implement attachments
Hand Tool Cultivation Low cost soil cultivation solution Effective but physically demanding Time consuming Less impact on soil structure Less risk of compaction Only practical on smaller scale
Digging Fork
Broad Fork
Mattock Great for breaking new ground; compact soil
Considerations when choosing tools/machinery Budget Overall farms needs Physical capability of operator This changes as you age! Effect on soil Effect on environment Ease/cost of repair and maintenance
Consistency Strength with which soil particles are held together Related to texture and water content Plasticity Describes the response of a soil to change in moisture content. Both are very important when considering soil cultivation
Cultivating soil when too dry Breaks aggregates into small pieces De-aggregates Can result in dust Very damaging to soil structure The drier the soil the more it acts like powder
Cultivating soil when too wet Where to start?! Compaction Risk and depth of compaction increases in wet soil
Cultivating soil when too wet The wetter the soil - the more it acts like water
When to Cultivate? Soil moisture needs to be just right Should be able to handle soil without water dripping out Should be friable and plastic feeling (if not too sandy) Soil water levels need to be considered at greater depths Dry Soil clodding; lost nutrients through dust Wet Soil compaction, loss of structure Decomposition time needs to be considered Sowing or transplanting to follow?
Hyphal soil fungi Forms symbiotic relationships with plant roots 80-90% of terrestrial plants Improves plant uptake of phosphorus and water in return for sugars Acts as expansion of plant root zone Contribute to soil aggregation and improved soil structure
Cultivation destroys hyphal networks Some species are killed by tillage Redistribution of fungal spores to lower soil profiles reduces root infection And
The loss of soil structure limits regrowth of the fungi Reduction pore space Fungi require air and water Reduced pore space limits air and water movement Compaction makes hyphal regrowth difficult
Fungal loss = Disadvantage for plants Less P uptake Less water uptake Reduced Disease immunity Loss of microbial diversity Reduces aggregation
Remember: goal is to reduce cultivation over time Reducing cultivation is difficult Difficult to manage large areas; especially organically Most low-till systems herbicide dependent Disease pressure can be higher in some no-till systems
Strategies to Reduce Cultivation Impact on Soil Choose methods carefully! Use spader over rotovator for cover crops Slow down rotation speed on rotovator Separate growing beds and paths Reduces compaction risk in growing areas Tractor wheels can go in pathways Design beds around tractor width
Strategies to Reduce Cultivation Impact on Soil Stay on top of weeds Reduces temptation to cultivate Reduces weed pressure less weed seeds Incorporate no-till methods into your system Easier to do at smaller scale
No-till goals: Maintain overall integrity of soil Reduce risk of compaction Reduce risk of structure damage Promote sustained biological presence Reduce use of machinery Mimicking natural soil processes
No-till goals in relation to why we cultivate : Why Do We Cultivate? Improve soil tilth/structure Weed control Reduce compaction
Rodale Institute developed crimping method Effective for cover crops Perennial wheat Use of winter killed cover crops No-till is a viable small-scale option
Most cultivation happens early in season Often gives instant results Main cultivation uses: Breaking ground Add amendments at this time Follow with cover crop Incorporating cover crops Weed/vegetation control Effcieitn vegetation control Seed Bed Prep Ensures fine soil texture for ease of seeding
Early Season Most cultivation happens early Incorporating winter cover crops Prepping seed beds Be patient! Watch soil water levels Season length depends on soil and location Assess need for cultivation Can you utilize no till methods? Transplanting into winter killed stubble If using no till methods get an early start
Mid-Season Cultivation more about weed control Could be incorporating cover crops Could be incorporating amendments for later crops Good time for no-till cover crop management Warm weather = rapid decomposition
Late Season Cash crop growing usually priority Cover crops can be more easily sown into less-than-ideal conditions no cultivation needed If no cover crop being sowed, or it s too late to sow, beds should be mulched Makes early season prep easier Remove mulch, add compost, sow or transplant
No Till Cropping Sequence Small Scale Starting with: Fall Rye cover crop well established due to early sowing
No Till Cropping Sequence Small Scale 1. Cover crop cut in mid-late February 2. Mulched Heavily with organic material Synthetic material Mulch smothers the crop reducing light, encouraging biological activity
No Till Cropping Sequence Small Scale 3. Mulch removed in April - May Cover crop absent Area now ready to plant 4. Top with compost, transplant: Tomatoes Long season in ground until September Undersow with legume
No Till Cropping Sequence Small Scale 5. Tomatoes removed in September/October Manage weeds carefully to keep soil clean Mulch lightly in summer to reduce evaporation 6. Amend bed with compost plant garlic Mulch garlic heavily with straw/leaves If planted early may be able to interplant Asian greens
No Till Cropping Sequence Small Scale 7. Harvest garlic in following July Remove mulch and amend with compost 8. Transplant overwintering broccoli and mulch 9. Harvest broccoli in early spring
No Till Cropping Sequence Small Scale 10. Summer cover crop buckwheat, phacelia, legume
Cultivation can both improve and damage soil Soil water is indictor of when to till Using appropriate method Like all human activity: Tillage does more than just one thing No-till is feasible on smaller scales Limited examples of sustainable, large-scale, no-till systems Though reduced tillage is possible New no-till methods need to be developed Perennial crop development and expansion reduces soil impact
The future or the past?