cover crops – Lee Reich

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COMPOST, LOOKING AHEAD, LOOKING BACK

September 9, 2021/4 Comments/in Soil/by Lee Reich

Spring Readiness

I’m frantically getting ready for spring. A large portion of that readying means making compost. Compost piles assembled now, while temperatures are still relatively warm, have plenty of time to heat up right to their edges, quickly cooking and killing most resident weed seeds, pests, and diseases.
My compost bins I like to think of my compost pile as a pet (really, many pets, the population of which changes over time as the compost ripens) that needs, as do our ducks, dogs and cat, food, water, and air. Today I’ll feeding my pet — my compost pet — corn stalks, lettuce plants that have gone to seed, rotten tomatoes and peppers, and other garden refuse. Plenty of organic materials are available to feed compost piles this time of year.

In case you’re wondering, no, I’m not taking a close look at each leaf, stalk, and fruit to make sure it’s free of pests before getting tossed on the growing pile, as is suggested by some people. Look closely enough, and you’d find that just about everything would have some hostile organism on it. But given some combination of time and heat, a well-fed compost pile will take care of such potential problems.
Compost, in the making Joseph Jenkins, in his excellent (and fun-to-read) book, The Humanure Handbook, quotes research showing complete destruction of human pathogens in humanure composts that reach 145°F for one hour, 122°F for one day, or 109° F for one week. The same should be true for plant pathogens and pests. For decades, I’ve tossed everything and anything into my compost piles and never noticed any carry over of pest or disease problems.

Heat and time also do in weed seeds. Survival depends on the kind of weed: Research shows that a couple of weeks at 114°F kills pigweed seeds, while only about a week at that temperature kills seeds of tomatoes, peppers and their other kin in the nightshade family. Generally temperatures of 131°F for a couple of weeks kills most weed seeds.

Heat and time aren’t the only threats faced by pathogens, pests, and weed seeds in the innards of my compost piles. In addition to heat, various antagonistic organisms — including friendly (to us) bacteria, fungi, and nematodes — stand ready to inhibit their growth or gobble them up.
Compost thermometer This time of year, my compost piles dial the heat up to around 140°F, and hold that temperature for a couple of weeks, or more, before slowly cooling down.

Weedy Revenge

Speaking of weeds, they also make excellent food for my compost pet. What sweet revenge I get tossing mugwort, creeping Charlie, and woodsorrel onto a growing compost pile and then get them back transmuted as dark, rich compost.

Other organic materials that go into my compost piles are a mix of goldenrod, bee balm, grasses, yarrow, and whatever else is growing in my south field. I cut parts of it with a scythe, let the scythings wilt for a day, then rake and pitchfork them up.
Haystacks and compost piles Also on the menu is some horse manure from a nearby stable, which I like mostly for the wood shavings that provide bedding for the horses. The manure itself furnishes nitrogen, which compost pets need for a balanced diet — 20 parts carbon to 1 part nitrogen but no need to be overly exacting because it all balances out in the finished compost. Lacking manure, soybean meal is another nitrogen-rich feed, as are grass clippings and kitchen waste.
Organic materials feed compost pile. Feeding a variety of compost foods provides a smorgasbord of macro- and micronutrients to the composting organisms and, hence, to my plants. Every few inches I also sprinkle on some soil, to help absorb nutrients and odors, and some ground limestone, to lower acidity of our naturally increasingly acidic soils, and to improve the texture of the finished compost.

The Annual Cycle of Compost Here

Compost made this time of year typically gets turned next spring, then, later in the growing season, pitchforked into the garden cart for spreading on vegetable beds.

Turning compost

A one-inch depth of ripened compost supplies all that bed needs to grow intensively planted vegetables there for the whole growing season. Spreading compost It was too late to plant a late vegetable crop in the bed I just cleared of old corn stalks, so I blanketed that bed an inch deep in compost. The same goes for a bed in which grew an early planting of zucchini.

Any beds that get cleared before the end of this month will get, before I lay down that blanket of compost, a dense sprinkling of oat seeds. The seeds will germinate and the seedlings will thrive in the cool weather of autumn and early winter.

Cover crop, 3 beds with cabbage

This “cover crop,” as it is called, protects the soil surface from pounding rain and insulates the lower layers. The oat roots latch onto nutrients that might otherwise wash down through the soil. And as the roots grow, they nudge soil particles this way and that, giving the ground a nice, crumbly structure that garden plants like so well.

Beds cleared after October 1st get only compost, no oats, which is almost as good. In all honesty, I’ve never noted any difference in the soil or in vegetable plant growth from using compost alone as opposed to compost plus a cover crop. That much compost, year after year, probably way overshadows the effect of a cover crop. The green cover does look nice going into winter, though.

(I deal more in-depth with composting, using compost, and cover crops in my book Weedless Gardening.) Oat cover crop

COVER CROP CONFUSION

August 4, 2021/11 Comments/in Soil/by Lee Reich

How Much Soil Organic Matter?

In last week’s blog I kept jumping the fence about cover crops. First I extolled their benefits. Then I wrote that they’re probably unnecessary in my heavily composted ground and possibly to blame for poor growth of some corn and tomatoes. Finally, I wound up stating that I do grow some cover crops anyway. No wonder I caused some confusion.
Oat cover crops All this prompted one reader, Peter, to comment with some specific questions that might also be of interest to some of you. I will now try to answer them.

His first question was: “How is percentage of organic matter in the soil determined.” “Organic matter” is carbon compounds; as such they can be oxidized, and when this happens they are lost from the soil as carbon dioxide and water. Microorganisms do this naturally in any soil as they feed on organic matter, in so doing releasing minerals associated with the organic matter in forms that plants can use for nourishment.

The way to test the percentage of organic matter in the soil is to weigh a sample, oxidize the organic matter, then weigh it again to measure the loss. Oxidation can be done by burning the sample at high temperature. Another way is to chemically oxidize a weighed sample using potassium dichromate and then measure how much dichromate is left after the reaction. (The latter reaction is more accurate than burning because carbonates in a soil will also lose carbon dioxide when heated, affecting the final weight.)

Peter, I suggest against determining the percentage organic matter of your soil in your kitchen. Soil labs generally include percentage organic matter along with other test results. (I cover soil testing in my book Weedless Gardening.)

Peter also reported that his soil tests very high in phosphorus, potassium, magnesium, and calcium. Soils to which have been added lots of organic matter typically test very high or excessive levels of phosphorus and potassium. That doesn’t present a problem, possibly because, as I wrote last week, “Conventional soil tests are for mineral soils, not soils that are very high in organic matter.”

As far as the high levels of calcium and magnesium, I’m not sure about that. Excessive applications of dolomitic limestone would cause that, and that would also be reflected in a high pH.

To Cover Crop or Not to Cover Crop, That is the Question

Now for a more difficult question. Why do I plant cover crops if I don’t think they’re of benefit in my soil? I guess that’s because I’m aware of the known benefits of cover crops. If nothing else, the cover crop obviously protects the ground’s surface from the pounding of raindrops and wide swings in temperature. Even if I don’t notice any positive impact, they may be there, more subtly. And then there are the still unknown benefits of cover crops.
Cover crop, 3 beds with cabbage The major, consistent negative impact of my late summer of fall planted oat cover crops has been to increase the number of weeds the following spring, specifically henbit (Lamium amplexicaule). For the past couple of years I’ve dealt with that problem by tarping those beds in spring for a couple of weeks or more. Or, not as good, just pulling out the henbit.

Because I only cover crop beds that are no longer needed for vegetable plants towards the end of the growing season, growing the cover crops doesn’t take up space in which I could otherwise grow vegetables.

Buckwheat cover crop in greenhouse

It’s also almost no trouble to sprinkle the oat seed over the bed before laying down the inch of compost each bed gets every year.
Sprinkling oat seed
And finally, I have to admit that I like the lush green look of the oat leaves, the leaves maintaining that look almost until the first day of winter. And even after that, they flop down on the ground, dying, but then hiding the brown compost beneath a tawny blanket.

Rye cover crop at Chanticleer Garden

Timely Planting

Last question: “When is the latest time to plant the cover crop?” Cooler weather and diminishing sunlight dramatically slow plant growth in autumn. Oats like that cool weather, and will germinate and sprout pretty late in the season. But there comes a time when so little growth will ensue that oats or any other cover crop is not really worth planting.
Oat cover crop sprouting
Here, about half way up New York’s Hudson Valley (USDA Hardiness Zone 5), I figure on the latest date to make planting a cover crop worthwhile is about October 1st.
Oat cover crop in October

CLOTHE THE GROUND

July 28, 2021/9 Comments/in Soil/by Lee Reich

Something Good for the Soil

Soil has been called “the skin of the earth.” That “skin” nourishes much of life here, so let’s take care of it. Which is one reason for cover crops, that is, plants grown not directly for us, but specifically to maintain or improve soil health. Typical cover crops include rye, oats, buckwheat, clovers, and other mostly grains or legumes.
Oat cover crop The most obvious benefit of a cover crop is the protection it affords the soil from wind and rain, either of which can carry away the most fertile surface layer. Also protection from temperature extremes. Another benefit is that cover crops can suppress weeds. Less obvious is cover crop plants’ ability to grab onto and bring back up to the surface layers nutrients that rain might otherwise wash beyond roots into the groundwater.

Buckwheat cover crop at Chanticleer

Some effects are even more subtle. Substances oozing from plant roots feed microbes and also bind soil particles to create small and large pores to create a good balance of air and water in the ground. Cover crops also can increase levels of all-important soil organic matter, which benefits plants and soils nutritionally, physically, and biologically in both known and unknown ways.

But Does My Ground Need It?

Despite the benefits of cover crops, you’ll rarely see them in my vegetable garden. Mostly, that’s because the beds are usually packed full of growing vegetables from very early to very late in the growing season. There’s nowhere to plant a cover crop! The vegetable plants themselves provide the same benefits as would a cover crop, especially since I plant at very close spacing, close enough, usually, to hide bare ground.

Bed of broccoli & endive

Planting cover crops in my garden to increase soil organic matter would be like taking coals to Newcastle. For decades, every year I’ve laid a one-inch blanket of compost over all my vegetable beds. (My book Weedless Gardening describes the whole system of soil care.) The result is soil organic matter levels, last time I tested, at about fifteen percent. No need for cover crops to boost my soil’s organic matter content.

Fifteen percent organic matter is very high. A typical, very good agricultural soil, such as the virgin Midwest prairies, was about five percent organic matter.

Then again, could fifteen precent be too high? Very high levels of organic matter lead to soil tests registering excessive levels of phosphorous and potassium. Traditionally, phosphorus was thought to be so tied up chemically in the soil that it would stay put, but some recent research indicates that water can push some phosphorus into the groundwater if phosphorus levels are high enough.

Conventional soil tests are for mineral soils, not soils that are very high in organic matter. A soil with around fifteen percent organic matter would better be called a “growing medium” rather that a “soil. Soils naturally this high in organic matter are classified as histosols, commonly called bogs, peats, or moors. Such soils, in contrast to my garden soil, are typically low in plant nutrients.

An obvious way to assess soil management is — duh — to look at the plants and their growth. Everything looks fine.

Problem? Maybe, Maybe Not

Except for a couple of strange goings on in one of my two vegetable gardens. In one bed, planted this year to early turnips and lettuce, now in corn, the corn in half the bed is stunted. (The turnips and lettuce did fine.) Stunted corn In another bed, tomatoes are doing fine, but are not as vigorous as they should be as compared with another bed of tomatoes in that garden.

Weakly & vigorous tomato beds My notes indicate that both beds received their annual blanket of compost, just like all the other beds. Last fall, when the compost was applied, I also sowed cover crops in those beds. Rather than my usual oats cover crop, which winter-kills so integrates well with my no-till system, I sowed crimson clover along with the oats. Why crimson clover? Because it’s pretty when it blooms in spring.

Crimson clover is allelopathic. Allelopathic plants can biochemically suppress growth or germination of nearby plants; the clover could have adversely affected growth of tomato and corn. Of course, only half the corn bed is stunted but clover germination, if I remember correctly, wasn’t uniform in that corn bed. I’ll file all this in the back of my head for future investigation.

Then again, oats, is also allelopathic, as are rye, sunflower, sorghum, and many other plants, including, most famously, black walnut. Allelopathy is often very specific, an allelopathic plant inhibiting the growth of only some species of plants. Said allelopathic plant might even promote growth of other plant species. Time, usually a couple of weeks, after an allelopathic plant is killed or removed, usually rids the soil of any allelopathic effect.

For completeness, I should mention that the corn and tomato bed problem could be traced to erratic behavior, this year, of my drip irrigation system, which has now been corrected.

I’m going to continue occasionally planting cover crops and will monitor more closely any positive or negative effects — in my garden. As they say in so many arenas: “Your results may differ . . .”

COMPOST, FERTILITY, & SUSTAINABILITY

October 24, 2014/13 Comments/in Gardening, Soil, Vegetables/by Lee Reich

Compost and/or Living or Dead Organic Material = Sustainable Fertility

Maple leaves already dapple the ground in red and yellow (early this year), one morning showed off what was to come with frost on the windshield, and each day the sun each hangs lower in the sky, yet I’m getting ready for spring planting. Really! Yes, I’d rather do it now than in spring.

Beds of spent vegetables have been cleared. Okra plants, in this cool weather, just sat in place, hardly producing any new pods. So out went the plants. I severed the main roots with my hori-hori knife (www.oescoinc.com) and yanked out each stem. When corn is finished, it’s finished. Beds of early corn got replanted with endive, lettuce, and other late vegetables, but the latest beds of corn were harvested too late for replanting. Clearing away old vegetable plants not only clears the deck for next spring but also takes offsite some pests and diseases that might otherwise lurk around next year to do their evil work.

Clearing bed of all weeds and plants in preparation for its layer of compost.

With spent vegetable plants cleared away — tomatoes and peppers are still yielding fruits, so they remain for now — I remove weeds. Ideally, all of them. Left in place, annual weeds spread seeds and roots of perennial weeds grab more tenaciously and deeper into the soil. A single pigweed plant, for instance, can drop 120,000 seeds, poised and ready to invade next year’s garden. That, and the 36,000 seeds on every plantain plant, the 39,000 seeds of each lamb’s-quarter plant, and the 8,000 seeds clustered in a crabgrass seedhead prompts me to pull these weeds now, before more seeds mature.

Of course, some weeds escape my notice, so the final step in preparation for spring is to suffocate these: I slather each planting bed with a one inch depth of mostly weed-free compost. A temporary 2X4 at each edge of the bed keeps the compost neatly in place until patted down firmly.

The compost does more than snuff out overlooked weeds. Its biotic life helps protect plants against pests and diseases. It helps soils hold water and air. And it feeds plants a smorgasbord of nutrients.

On a Garden, Farmden, or Small Farm, Fertility Simplified

Did I mention spreading fertilizer, “organic” or otherwise, in getting the soil ready for spring planting? No. A one-inch depth of compost supplies all the nutrients needed to grow vegetables, even in beds with closely spaced plants. Paraphrasing the Beatles lyrics, “All you need is . . .compost, da, da, da-da da.”

Bed in middle has been lathered with an inch depth of compost, left on surface.

A garden is not Mother Nature left to her own devices; nonetheless, I try to emulate her as much as is practical. She does not spread fertilizer. Plants are naturally nourished as organic materials, such as leaves, stems, wood, roots, and dead animals, decompose to release whatever nutrients gave them life. I enjoy making compost and make enough to spread that required one-inch depth over all the beds.

Next best would be to spread some concentrated source of the most needed nutrients, that is, “fertilizer,” on the ground and supplement it with a mulch such as wood chips, straw, hay, or other organic material. Here, an organic fertilizer, such as soybean or alfalfa meal, has the advantage over a chemical fertilizer in that nutrients become available over a long time and are made so in response to temperature and moisture, in synch with plants’ needs.

Two advantages of maintaining fertility with compost rather than mulch plus fertilizer are that seeds are more easily planted directly in the compost and compost, if made from a variety of feedstuffs, provides a wider spectrum of nutrient for the plants.

Cover Crops, Used Correctly, for Even Large Farms

A wheat farmer in Montana is not going to be spreading an inch of compost on his 1,000 acres, or even soybean meal and a mulch of straw. Agriculture is a balancing act, again, not Mother Nature but not disrespecting her either. In the case of a wheat farmer, or any large scale farm, cover crops are a practical route to healthy soil.

Cover crops are plants grown specifically to maintain or improve a soil. Cover crops may occupy the ground for part or for the whole season. As they grow, their roots push through the soil to break it up and, upon their death, leave channels for air and water. Roots exude natural compounds that stimulate a a wide population of beneficial microbes and release nutrients from the soil’s rocky matrix. Leguminous cover crops garner nitrogen from the air into a form that plants can gobble up. And once dead, deliberately or with age, cover crops can maintain or increase all important soil organic matter.

Oat cover crop in one of my beds.

The devil is in the details. Killed too young, while still lush and green, a cover crop adds nothing in the way of soil organic matter (but does protect the soil surface from erosion). Tilling a cover crop into the soil, a common practice, might burn up more organic matter, by giving the ground a big burst of oxygen, than is added by the cover crop, whether the cover crop is young or old. And then there is the choice of cover crop itself for regional adaptability, for shading out weeds, or for beefing up a poor soil.

How about this? Set aside a separate area for cover cropping each year. Or set aside a separate area for cover cropping, but mow the plants one or more times through the growing season to provide mulch or feedstuff for compost. With enough land and suitable mix of cover crops, including legumes for nitrogen.

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“Sustainability” is a buzzword these days. Nourishing the ground with nothing more than annual sprinklings of chemical fertilizer not sustainable in terms of long-term soil health and because synthetic fertilizers require fossil fuels in their making. At he other end of the scale, primitive slash and burn agriculture, where land is cleared and burned, crops planted for a few years, then the site abandoned for a new site, is sustainable. But you need enough land to be able to leave time for the soil to naturally regenerate before another slashing and burning. In our “advanced” culture, recycling organic materials back to the land is also sustainable. It’s just a matter of getting the materials back into the soil, as compost or more directly, but not to a landfill or an ethanol (gasahol) factory.