How to Boost Soil Health Using John Kempf’s 6 Principles: A Guide to Thriving Soil Biology
This Article Is About How to Boost Soil Health Using John Kempf’s 6 Principles Because Healthy Soils Feed Healthy, Productive Plants.
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Healthy soil is the foundation of a thriving garden, and in the UK’s varied climate, nurturing soil biology is key to success. Here’s how you can create the ideal environment for soil microbes to flourish, ensuring your plants get the nutrients they need to grow strong and healthy according to John Kempf‘s 6 Principles.
Kempf is an Amish farmer from Ohio. He is often presented as a visionary entrepreneur, sought-after speaker, and podcast host renowned for his expertise in regenerative agriculture. As a leading crop health consultant, he designs cutting-edge soil and plant management systems that redefine modern farming.
In 2006, Kempf founded Advancing Eco Agriculture (AEA), a pioneering organisation dedicated to sustainable agricultural solutions. Today, he serves as its Chief Vision Officer and Executive Board Chairman, driving innovation in ecological farming practices worldwide.
Kempf empowers farmers to achieve optimal plant health, productivity, and ecosystem resilience—bridging the gap between science and practical application.
A lot of what Kempf preaches makes sense to me. But he works in American agriculture and that doesn’t translate 100% into gardening in the UK or Europe.
Below I present Kempf’s principles as headlines and have then added my own comments based on my past experience as a UK farmer and market gardener.
1. Create the Right Physical Environment for Soil Biology
Kempf says think of your topsoil as a laboratory petri dish – it needs the right conditions to support abundant and active microbial life. To achieve this:
Keep it covered: Use mulch or cover crops to regulate soil temperature, retain moisture, and protect against erosion.
Manage moisture: Ensure proper drainage to prevent water-logging, which can harm soil biology. Techniques like shallow drain tiling can help in heavy clay soils, common in many parts of the UK.
Avoid compaction: Minimise walking on garden beds to maintain soil structure and allow air and water to circulate. Ditto, keep machinery off the soil when it is wet. Compaction is a soil killer .. and that means a plant killer as well.
Green manuring and cover cropping include the use of crops such as clover.
2. Replenish Lost Biology
Over time, soil biology can become depleted. To restore it:
Add high-quality compost: Home made compost, vermicompost (worm compost) and Johnson-Su compost are excellent choices for reintroducing beneficial microbes. You can also use trench composting and cut and drop.
Use compost teas: These liquid extracts are rich in microorganisms and can be applied directly to the soil or as a foliar spray. BUT don’t depend on compost teas to feed plants all the nutrients they need. Compost tea can add biology but is unreliable in terms of available nutrients with very small quantities.
Consider microbial inoculants: Purchased products containing beneficial bacteria and fungi can allegedly help kickstart soil biology. I have reservations about this however as soil is rarely short of microbes IF it is composted. It isn’t an absence of microbes that tis the issue, it is the lack of nutrients for them to feed and increase in numbers. See below
3. Feed Soil Biology with Mulch or Cover Crops
Soil microbes need a constant food source to thrive.
You can provide this by:
Mulching: Apply organic mulch like straw, wood chips, or leaf mould to feed microbes and improve soil structure.
Growing cover crops: These are the preferred method as they continuously release sugars through their roots, promoting faster soil aggregation and microbial activity. In the UK, options like clover, vetch, and rye work well, as do legumes. In fact anything growing is vastly superior to bare soil.
4. Provide Balanced Mineral Nutrition
Soil biology helps release nutrients for plants, but it can’t create minerals that aren’t present in your soil. In a garden situation adding compost and organic fertilisers will usually provide all that is needed. But commercial grower and farmers should consider the following.
To ensure your soil has what it needs:
Test your soil: Use commercial soil testing labs to measure pH and identify the level of each important nutrient.
Add missing minerals: Based on your soil test results, amend your soil with natural mineral sources like rock dust or lime.
5. Boost Photosynthesis with Foliar Nutrition
Kempf says we should maximise photosynthesis as it is the secret to a high-performing farm. He argues that plants that photosynthesise efficiently produce excess sugars, which they share with soil biology through their roots.
To enhance photosynthesis Kempf says:
Use foliar sprays: Apply nutrient-rich sprays directly to plant leaves for quick absorption. Effective foliar sprays often combine:
Compost tea
Microbial inoculants
Seaweed extract
Plant nutrients
Trace minerals
I am not convinced that gardeners routinely need foliar feeds. Even on high yielding crop on my market garden I didn’t regularly use foliar feeds. Their use was very rare. I only recall one occasion when I resorted to this and I’m not convinced it made any difference. It was on a crop of toms that was flowering on its ninth truss and I did it as a belt and braces measure .. and probably wasted my time.
The thing is, I believe soils that have plenty of compost or organic matter added will nourish the microbial life and that will provide adequate levels of nutrients to the plants. A lack of available nutrients is rarely the limiting factor in plant growth in gardens and allotments. Read my article on Liebig’s Law for more information on this.
6. Avoid Excess Nutrients
While nutrients are essential, Kempf says that too much can cause problems. He is right about that but some of the advice I see on excess nutrients makes little sense.
Before going in to that let me explain one of the excess nutrient issues I am very aware of.
Where tomatoes are grown and provided with a lot of nutrients excess nutrients can build up in the soil. This is measured by a conductivity test. It measure excess “salts” (not salt, that is a different thing). Excess salts can cause damage to successive sensitive crops such as lettuce. Our solutions was simple. These excess salts are soluble so the solutions was to “flood” the soil and wash them away. Several hours of overhead irrigation in a greenhouse washed away excess “salts” and the lettuce crop was undamaged. The damage if the conductivity was high was root burn which resulted in poor growth or .. more likely .. plant death.
To maintain balance:
Avoid animal manure-based compost: It can lead to excessive nitrogen, phosphorus, and potassium (NPK) levels, which may attract pests and diseases. That is common advice in this situation BUT it’s not my advice. I suggest animal based manures are composted until odourless and crumbly. Problem solved.
Opt for plant-based compost: This is less likely to create nutrient imbalances and is better suited to most UK gardens. See above .. but also read my comment above.
Why This Matters for UK Gardeners
The UK’s diverse soils and unpredictable weather make soil health particularly important. By following these steps, you can:
Improve soil structure and drainage, especially in heavy clay or sandy soils.
Enhance plant resilience to pests, diseases, and extreme weather.
Boost yields and grow healthier, more vibrant plants.
Getting Started with Kempf’s 6 Principles
Test your soil: Start with a soil test to understand its current state.
Experiment with cover crops: Try growing clover or vetch over winter to protect and nourish your soil.
Make your own compost: Start a compost heap or worm bin to recycle garden and kitchen waste into rich, microbial-filled compost.
By nurturing your soil biology, you’ll create a thriving ecosystem beneath your feet, leading to a more productive and sustainable garden. Happy gardening!
My Kempf’s 6 Principles Conclusions
There is a certain logic in a lot of Kempf’s 6 principles but I don’t think they all apply to gardens and even professionals need to use them as a guideline rather than rule.
