increasing organic matter – Sustainable Market Farming

Book Review: Soil Science for Gardeners, by Robert Pavlis

Book Review: Soil Science for Gardeners, by Robert Pavlis, New Society Publishers, 2020. 228 pages, with charts and diagrams, $18.99.

I recommend this book to all gardeners who have hesitated to open a soil science text for fear of dry incomprehensible overloads of numbers. Robert Pavlis explains how your garden grows, and dashes cold water on false myths that may have been wasting your time and limiting your success for years! He leads us to a better understanding, including on a microscopic level, of soil biology, chemistry, physics, geology and ecology and to a place of wonder and curiosity at the everyday functioning of crops and soils.

This new comprehension can lead us to do right by our plants and our gardens, leading to healthier plants and higher yields. Robert writes in plain language, as a gardener with over 45 years of experience. He is the author of those Garden Myths books you might have seen. Perhaps, like me, you paid them little attention, thinking your own knowledge was fact-based. Even so, like me, you might find you had been holding onto some anti-facts (mine was that I believed compost is acidic – not so!). This book aims to have us understand real soil and make real improvements, via a Soil Health Action Plan at the end of the book.

The three sections of the book are Understanding Soil, Solving Soil Problems, and A Personalized Plan for Healthy Soil. A satisfying, logical sequence. Read the sections in the order presented! Robert says it’s very easy to grow plants if you understand the soil which anchors them, feeds them and provides the air and water they need to survive. With a solid understanding of what’s going on, you won’t need to memorize rules.

The 2016 definition of soil, by the Soil Science Academy of America is “Soil is the top layer of the Earth’s surface that generally consists of loose rock and mineral particles mixed with dead organic matter.” A rather bland underselling of what soil accomplishes. Here comes myth-bust #1: “Soil is not alive. It does not need to eat or breathe.” “The whole idea that soil is a living organism that requires similar attention to animals is completely false and leads to many poor recommendations for managing soil.” No, don’t give up here! It’s not the soil but the ecosystem of the soil and all the living organisms in and on it that holds the life. The ecosystem contains life, but is not itself alive.

Air and water are critical for good plant growth, about 25% of each. A simple, startling truth. The sand, silt and clay we might worry about make up another 45%, and 5% organic matter might fill out the total. A large tree can remove up to 100 gallons (400 liters) of water a day, discharging most of it into the air as water vapor. As the water leaves the soil, air is pulled in to fill the spaces. Roots pull the oxygen in, day and night, to convert sugars into energy. Were you also lead to believe that plants photosynthesized by day and respired only by night?

Did you know (I hadn’t thought about it) that “soil pH” is really an average of the pH of the water in the soil, and a spot with organic matter and lots of bacterial activity will have a very different pH from a spot with less organic matter? The rhizosphere (the area right around a plant’s roots) can have a very different pH from the soil solution further away. Plants can grow in alkaline soil because their roots are actually growing in acidic conditions. The nitrogen-fixing bacteria on legume roots cause the plant to release hydrogen ions, making the rhizosphere more acidic. To some extent, our efforts to change the soil pH can be undone by our crops and weeds! A soil property called buffer capacity lets the soil absorb materials at different pH and maintain its same level. Peat moss is acidic, but it does not acidify alkaline soil. The soil in the rhizosphere can be 2 pH units different from the soil around. This is usually written about in rather magical terms, but here it is in plain language.

Roots grow just fine where there is enough phosphorus. Adding more at transplanting doesn’t help, and can hinder. Visual plant symptoms can predict possible deficiencies, but are not a reliable diagnosis. Purple leaves may indicate phosphorus deficiency or cold temperatures, high light intensity, pest damage or lack of water. Or a nitrogen shortage reducing the plant’s ability to absorb phosphorus. There’s much that we don’t know!

Pay attention to the Cation Exchange Capacity – the measure of the soil’s ability to hold cations – because many plant nutrients are cations. You can increase the CEC by increasing the clay content, increasing the OM or increasing the pH. Read more in this book.

Have you ever thought about the “free” nitrogen from legume root nodules? Rethink of it as “homegrown” or “solar” rather than simply magic and free, because the leguminous plant may use up to 20% of the sugars produced during photosynthesis, to feed the bacteria.

Don’t justify your adherence to organic gardening by falsely claiming that synthetic fertilizers kill bacteria. Bacteria feed on both synthetic and organic fertilizers. This book challenges us to find the factual basis for choosing to grow organically, making us stronger advocates.

Hoophouse bed broadforked to aerate the soil without inverting.
Photo Pam Dawling

The bacteria chapter is followed by a chapter on fungi. Fungal spores are everywhere, even the Antarctic. Fungi are crucial for cleaning up plant litter on the soil surface. They grow above-ground hyphae which can penetrate dry leaves or wood chips and move the nutrients deep into the soil. Bacteria can’t tackle such tough stuff! 150 species of fungi capture and digest nematodes.

Why is organic matter important? This chapter explores the chemical and biological effects of organic matter on soil. Soil contains three forms of organic carbon: the living (15%), the dead and the very dead (stable humus and charcoal). Increasing the level of organic matter in the soil can increase aggregation, improve water infiltration (reducing runoff), increase aeration, increase water-holding capacity, improve tilth of clay soils, reduce crusting, and improve the size and distribution of the pore spaces. Those are just the physical effects. It will also increase the cation exchange capacity, increase the availability of nitrogen, boron, molybdenum, phosphorus and sulfur, and increase the microbial activity and diversity.

Often we think about adding partially decomposed OM such as compost and manure. We should face the reality that compost tends to have low levels of nutrients (maybe 1:1:1). The big value of these is in providing food for microbes, short-lived beings that provide a constant supply of fresh OM, multiplying its value. Partially decomposed compost takes about five years to finish decomposing, during which time it slowly releases nutrients. This gradual steady supply is what crops need. The humus left at the end is a complex molecular mixture of carbon, hydrogen and oxygen, resistant to further decay.

The initial effect of adding fresh OM (not composted OM) is an explosion of microbial reproduction, feeding and death. The microbes use nitrogen, which can cause plants to suffer a shortage. It takes time for a new balance to be achieved, providing adequate N for the plants. The needs for the N can encourage gardeners to add so much compost that the P level is too high, which can bring death to mycorrhizal fungi, leading to roots driving deeper to access their own P from the soil directly. We have very high soil P, a result of misunderstanding soil test limits. I have worried about it, then read more and stopped worrying. Soil P is pretty stable. If you are not leaching P into a waterway, it just stays in your soil until a plant need it. We switched to using less compost and more cover crops where we could. We were already using a lot of cover crops – it’s not like we were slouches in that department! After more time, I settled on accepting our situation, and as the plants show no sign of P-caused problems and our soil is bursting with earthworms, it doesn’t affect us much.

I mentioned at the beginning that I learned that finished compost is alkaline, not acidic. In the initial composting stage, acidity happens. Then fungi thrive, and decompose the tough lignin and cellulose, causing the pH to rise and bacteria to take over. Compost-making has lots of myths! Poorly understood science makes them grow, I suppose. Bokashi composting, for example (more of a fermentation than a composting process) is based on the idea that fermented material decomposes faster, although it’s unclear if this is really true. “The best method of composting is the one that you do and continue to do because you like doing it. Any form of composting is better than taking yard waste to the curb.”

The Rhizosphere chapter is fascinating! Root exudates can restrict the growth of competing roots, attract microbes into symbiotic relationships, Change the chemical and physical properties of the soil solution and the soil, and make nutrients more available. Bacteria make explosive population growth as they feed on exudates. Then their predators, nematodes and protozoa, join the party. The soil water around the roots becomes a nutrient soup. By photosynthesis, the plants produce the attractive exudates that the soil food web turns into plant nutrients right where the roots can efficiently hoover them up. Plants are active in seeking nutrients, not passive recipients. Not to say they have knowledge, or think and plan. It’s a matter of chemical reactions controlled by enzymes with the capacity to change their activity based on the presence or absence of chemical triggers. Let’s marvel at the reality! We don’t need fairy stories!

The second section of the book, Solving Soil Problems, starts with identifying the problems, and works through techniques affecting the soil, chemical and microbe issues, increasing organic matter and structural problems. We are not feeding plants, we are replacing missing nutrients in the soil, so they can take the nutrients they need. The solution will depend on your soil, so a “tomato fertilizer” is not going to be what tomatoes need in every soil. If you plan to top up the missing nutrients, get a soil test to learn what those are. But if you plan to apply manure or compost everywhere as your only amendment, your money is wasted on a soil test. If you add compost every year and return cover crops, organic mulch and your plant debris to the soil, and your plants are mostly growing well, you probably don’t need to add any other fertilizer to your garden. This alarmed me a bit. What about boron shortage, which happens here? Yes, if you are a farmer or market gardener, yields do matter and soil tests (free for commercial growers in Virginia) will be worthwhile. But for a home gardener, or a landscape gardener, yields might not be at the top of your list. Robert explains various tests, and gives his take on how useful they are. The information here can save a lot of confusion and wasted effort.

Photo by NCSU Crop Soil Undergrad course

In the techniques chapter, the author explains the dramatic difference in available nitrogen in a cultivated garden and a no-till one. No-till can supply up to five times the nitrogen, because tilling adds more air into the soil, increasing the microbial activity, burning up the OM. There is a useful chart comparing the effects of fertilizer, compost and wood chips on the soil. We’ve all learned not to bury wood chips in the soil, where they use up the nitrogen while decomposing. But on the surface they can do wonders.

Crop rotation has come under scorn recently from commercial growers who are focused on maximizing yield and profit for their time on small areas of land. Sure, salad mix and baby spinach can rake in the money. But generations of farmers have learned to grow different types of crops each year in a particular spot. This can increase yields 10-25%, even though we are not sure why. Studies have shown it’s not simply nutrient availability. It could be pH changes freeing up more nutrients, or microbe biodiversity, or differing root growth granting access to more depth than the current crop alone can achieve. Rotated crops are more drought resistant and make better use of nitrogen. Research is needed.

As I was happily digesting this book I was brought short by this mnemonic that still puzzles me: “If you have trouble remembering whether P stands for phosphorus or potassium, remember that these nutrients are listed in alphabetical order. Phosphorus comes before potassium in the alphabet, and so P comes before K.” Um, K comes before P, last time I looked. Confusing.

Does rock dust add nutrients? No evidence, says Robert. Do not be beguiled by mineral products claiming to add 74 minerals to your soil. Plants might only use 20 of them. More is not better! Beware fad products such as biostimulants and probiotics. Plants cannot use vitamin B1. What about compost tea? Yes, it adds nutrients, but claims that the included microbes work wonders are not supported by science: test results are very mixed, including worse. Sometimes we are too gullible! Milk, molasses: they add nutrients but no special magic. Fermenting something cannot add nutrients – it could make some more available, although that isn’t proven either. The fungal and bacterial populations increase, but are the species nutritious ones or pathogenic ones?

The gardener’s goal is to farm healthy microbes, even though they are too small to see. Use the state of the soil and the health of the plants as indicators of the health of the microbes. Supply OM, water and you’re on the right track. It has been proved useful to add rhizobium legume inoculant if you haven’t grown legumes for some years. Fungal inoculation of soybeans in low phosphorus soil will be effective. Not otherwise.

The author’s general practice is to improve the soil environment to help existing microbes. There is a list of 7 general ways to do that. There is a whole chapter on increasing OM, using what’s local and cheap. Coir is a waste product, but its production causes environmental damage to local water supplies (large amounts of sodium have to be leached out).

Biochar, one of the new “Garden Wonders”, has claims to make big improvements to the soil food web. Most of the biochar studies have been conducted in labs, not on farms. Even then, 50% of the studies report higher yields, 20% report no change, and 30% report a decrease. There are probably better ways to spend your money!

What about gypsum? I believed the common advice to use it to break up clay soils. Mostly this myth is not supported by evidence. Gypsum can have some negative effects. Add more OM instead. Likewise for improving sandy soils: add more OM.

The final section of the book is a set of worksheets and instructions to help gardeners improve the soil health where they are. This is a slow process, so start soon! Robert has also made the forms available on his website www.gardenfundamentals.com/soil-book-forms. First assess your soil, then make an action plan, then record your progress.

I recommend this book for all sustainable/regenerative/organic gardeners and small-scale farmers, and even large-scale farmers who realize there are gaps in their understanding of soil science. This book is very accessible, user-friendly and full of soil-based common sense. Winter is a good time to make new plans!

Robert Pavlis has two websites: www.gardenmyths.com and www.gardenfundamentals.com as well as a YouTube channel www.youtube.com/Gardenfundamentals1

Book Review: The Organic No-Till Farming Revolution: High Production Methods for Small-Scale Farmers, Andrew Mefferd,

The Organic No-Till Farming Revolution: High Production Methods for Small-Scale Farmers,

Andrew Mefferd, New Society Publishers, January 2019, $29.99

Organic No-Till has been an unachievable goal for many of us, but there’s no need to feel guilty or ashamed! We may understand the biology, and even the physics and chemistry of it, and why it’s a Good Thing. We can see how it can be done on a domestic scale, especially by those who can grow or buy lots of mulch, and especially if there’s no need to account for time and money invested. There is equipment (roller-crimpers and no-till planters) that makes large scale organic no-till possible and efficient. But for those of us growing food in the middle scale, it’s proving harder. Giant equipment works for acres of soybeans but not for market farming. How to keep the weeds away while tending forty sowings of lettuce? The Organic No-Till Farming Revolution provides very practical information for those who want to increase the amount of no-till growing on their small-scale farm.

Andrew Mefferd says in the introduction, “No-till is as much about climate change as it is about soil health as it is about farm profitability.” Work on all three at once with this book. 50-70% of the world’s carbon in farm soils is off-gassed due to tillage (according to a Yale study). This decreases soil fertility at a time when we need to grow more resilient crops to cope with climate change. Global food production could be reduced by up to 17% by 2100 due to climate-induced crop failures. All steps in a good direction are worth taking.

Andrew is not a proselytizer and this is not a religion. You don’t have to commit to permanent no-till everywhere to benefit from some very practical new skills, enabling you to increase the area in no-till practices. Different strategies work for different farms and different crops. Not inverting the soil layers is important. Any reduction in tillage is a good step; shallower is better than deeper; less often is better than after every crop. The tilther and power harrow on a shallow setting are used by some no-till farmers. One last tilling before setting up permanent beds is OK if that’s what you need to do! Think in terms of doing more no-till and take away any pressure to feel bad if you continue to do some tilling. One step at a time towards healing the earth, the climate; improving your soil and your crops.

The first part of the book explains the concepts and presents various methods: mulch grown in place; applied cardboard, deep straw or compost; occultation (tarping) and solarization (clear plastic). The main section consists of in-depth interviews with seventeen farmers about what works for them. After reading the first part, you can dive into the chapters with the methods that most appeal to you. The book is written so it doesn’t have to be read sequentially to make sense.

Andrew worked at Virginia Tech’s Kentland Research Farm on organic no-till vegetable production, using roller-crimpers and no-till drills. The next year he moved to a 3 acre farm and temporarily forgot about no-till because the methods he’d seen were not applicable to that scale. Ten years later, in 2016, he read articles in Growing for Market magazine, and attended conference workshops by farmers who were succeeding with organic no-till on smaller farms. These growers were using various different methods, and Andrew decided to visit them and write up the interviews.

“Want to build organic matter and soil biology because of the way you grow, instead of despite it?” Andrew asks. Increasing the organic matter in the soil will help the soil hold more water, suffer less from run-off and need less applied water per year (1″ (2.5 cm) of water saved per 1% increase in OM has been quoted). Carbon is stored in the soil, keeping it out of the atmosphere. Paying attention to the soil biology and feeding the soil is the heart of organic farming. We must farm more ecologically if we want to survive. At the same time, small-scale farms must be profitable to sustain the farmers. This book has many examples of farmers that started small with limited resources, and are able to make a decent living. Avoiding the need to buy heavy machinery is a big saving.

I love this surprise quote: “Tilling the soil is the equivalent of an earthquake, hurricane, tornado and forest fire occurring simultaneously to the world of soil organisms.” Which outspoken radical farming group made this proclamation? The USDA-NRCS! Taking care of the soil biology reduces the urge to compensate with chemistry. The less tillage, the better-off we can be. OM levels can rise quickly when tillage is reduced. Cover-cropping, adding compost and organic mulches are all ways to achieve this. The churning of tillage burns up OM. As Bryan O’Hara of Tobacco Road Farm, Connecticut, says, “Tillage is a nutrient flush from all the death you just wrought on the soil…Tillage doesn’t give nutrient balance, it gives you nutrient release.” More OM must be added every year just to maintain levels that were there before tilling.

Tarping is a rediscovered method that lets the soil digest the plant material without any tilling. This is especially useful when you have several weeks to spare after a harvest, but not enough time to grow a cover crop. The soil biology breaks down the residue, weed seeds germinate then die. The soil is left ready to replant.

After listing all the many benefits of no-till, Andrew explains the disadvantages. Weed control without cultivation is the main issue, especially perennial weeds. The slowness of mulched soil to warm in the spring is another. A third is that high OM can lead to more slugs. If you mulch with tree leaves, you might find squirrels and chipmunks rummaging for acorns. Grass creeps in from the edges. These problems are all addressed in the book.

The Overview of Organic No-Till Techniques is a summary of methods, biodegradable mulches and plastic sheet materials.

Biodegradable mulch grown in place is the method we used for many years for our large planting of paste tomatoes. We sowed winter rye, hairy vetch and Austrian winter peas in early September, following our spring broccoli and cabbage. At the beginning of May we mowed down the cover crop with our hay cutting machine and the next day dug holes and transplanted the tomatoes. We used a small shovel for our big transplants. Shawn Jadrnicek suggests using a stand-up bulb planter. The legumes provided all the nitrogen the crop needed, and the long-cut cover crop kept the weeds at bay for maybe 6 weeks. By then we had trellised the tomatoes and were able to unroll big round bales of spoiled hay between the rows. This dealt with the weeds for the rest of the season. One year in ten in our row crops rotation was no-till. We tried a few other applications of this method but generally they didn’t work as well. We were unable to direct-seed into cut mulch, for instance. Our watermelons didn’t like the cold soil, and we wanted watermelons in August, not October! To grow big enough cover crops for this to work, the food crop has to be planted no earlier than late April in central Virginia. Paste tomatoes worked well because we didn’t need an early harvest. Transplanted Halloween pumpkins and winter squash work. Fall cabbage and broccoli (on German millet and soybeans) can also work.

Bringing in biodegradable mulch (hay, straw, cardboard, paper, compost, tree leaves, wood chips, spent brewers’ grains) is the second method. The material needs to be spread thickly, usually 3″ (7.5 cm) or more and used appropriately (don’t switch plans and till in raw wood chips!). Straw can cost $750 per acre covered. A round bale covers about 200′ by 5′. We use hay bales or biodegradable plastic on annual crops, cardboard and wood chips around our fruit plantings. The existing weeds and crop residues will need to be removed first. Flaming works for small weeds, otherwise use one of the sheeting methods. Read the book to get the all-important details on how to be successful.

The non-biodegradable mulch methods are tarping (occultation) and solarizing. Tarping was introduced to most of us by Jean-Martin Fortier in The Market Gardener. For annual no-till crops, first tarp the soil using an opaque material such as silage tarps (or solarize in hot weather). After killing the weeds, uncover, spread mulch and transplant into it. Tarps will not kill docks or nut-sedge. Tarping takes from 3-6 weeks, (the shorter time in hotter weather). Allow longer if you’re bringing new land into production. Plan ahead, and tarp all winter. Silage tarps warm the soil for early spring plantings, and also prevent soil moisture from evaporating.

Solarization uses clear plastic (old hoophouse plastic is ideal). In a summer hoophouse, solarization can be as quick as 24 hours, Andrew says. When we’ve done this, one of our goals was to kill nematodes and fungal diseases, not just weeds, so we waited a few weeks. Outdoors it takes several weeks. You can see when the weeds are dead. Bryan O’Hara poked a thermometer probe through solarization plastic and found a 50F degree (28C) difference between the outside air and the soil immediately under the plastic; a 10F (6C) difference at 1″ (2.5 cm) deep and little temperature gain lower than that. Solarization does not kill all the soil life!

The growers interviewed explain which methods they use and why, helping readers weigh the pros and cons for the various crops we are growing, and our resources, climate and soils. Andrew offers some pointers on which methods are likely to work best for which situations. Several farmers tell how they transitioned into organic no-till for various crops, for instance buckwheat, compost and Weed Guard Plus paper mulch for a garlic crop, followed by two crops of lettuce. Mossy Willow Farm in Australia has a designated area for direct-seeded crops, where they use sprinklers, and the tilther if needed. The rest of their farm (transplanted) uses drip irrigation, but the soil does get too clumpy for direct seeding, and is slower to improve.

Farmers also address the things that went wrong while they were learning (thin stands of cover crops, cover crops not dying, getting the timing wrong on seeding or roll-crimping, weed seeds blowing in from elsewhere). They describe equipment they found helpful (drop-spreaders to lay down even layers of woodchips or compost, landscape fabric, the stand-up bulb planter, Tilther, Jang seeder, paperpot transplanter, broadfork). They also address timing of cover crop sowing to avoid warm-season and cool-season weeds; extending the weed suppression period of cut or crimped cover crops by adding tree leaves; pre-irrigating before digging transplant holes; and many other tips to success. A strategy for tall crabgrass is to mow it down, cover with newspaper and compost. A border of comfrey plants all-round the garden does a great job of keeping grass out. You can quickly see how this book will pay for itself many times over!

No-till beds are ready for early spring crops, even in wet regions, if the beds are mulched overwinter. Because no-till builds soil upwards, it is a good technique for land that is very rocky or with shallow topsoil. Another advantage of no-till is that you can install fairly permanent irrigation (drip or sprinklers). And you can farm intensively on small areas without needing to cater to the turning radius of large machinery. Getting high productivity from small areas is becoming an essential factor to consider.

Potatoes are a soil disruptor, and can bring up new weed seeds, so it’s worth covering the beds as soon as the potatoes are harvested. At Four Winds Farm in New York State, they plant garlic in the fall after potatoes, then mulch over the top of the garlic with a thick layer of compost. In their bigger plan, they only plant garlic in every other bed (although composting all). The following spring they plant winter squash in the empty beds, which can take over all the space after the garlic is harvested.

As I read the interviews, I started to worry: were none of these farmers having a problem using such high amounts of compost? The first problem is making or buying the sorts of quantities they are using, but the second is a build-up of phosphorus, which we have experienced on our farm. Singing Frogs Farm has studied this, testing the water run-off in the ponds at the low-point of their land. The phosphorus stays in place in their system, it does not leach. Nor does the nitrogen. The soil biology sponges up the nutrients, the 3-8 crops they grow in a year absorb them. They don’t rely on compost for fertility, but now use pelleted feather meal, calcium and rock dusts. Their compost use is 0.5″ (< 1 cm) per year, very different from the many farmers using much more.

Daniel Mays at Frith Farm in Maine believes cover crops provide a more active kind of organic matter, which is tailored to the soil. He is seeing better results than with compost. Roots in the Ground! Hedda Brorstrom, of Full Blossom Flower Farm, Sebastopol, CA is trending in the other direction. She points out that a lot of the compost for sale is made with lots of animal manures, which does send the phosphorus levels way up. Because growing cover crops was not working for her, she researched available composts carefully. High-carbon compost is a way to avoid sending the phosphorus levels up too much. She has used 4-8″ (10-20 cm) of compost per year.

Neversink Farm in New York’s Catskill Mountains point to intensive production (“the greenhouse mentality writ large”), 5 people working on 1.5 acres of permanent (not-raised) beds, and direct sales to customers, as factors in their success. As Conor Crickmore says proudly, “Our farming practices may be radical but they have resulted in our farm being one of the highest production farms per square foot in the country.” Close to $400,000 gross on 1.5 acres!

The collected wisdom and experience in The Organic No-Till Farming Revolution can save newer no-till farmers from a lot of frustration and wasted time, money and mental and emotional energy.