Soil scientists are finally getting the message and are loudly extolling the virtues of no till agriculture. However so far only a few in the agriculture community are listening.   Until recently most of the soil scientists sided with the agriculturists.   They assumed that mixing the soil layers, or horizons, created by Nature as it produces soil increases crop production.

They also said tilling suppresses the “harmful”(apparently unnecessary?) anaerobic bacteria mostly deep in the soil. Research has shown otherwise – that the ethylene anaerobic bacteria produce is essential to plant health,  particularly in making  anemia-preventing iron available to plants. Ethylene is also critical in the creation of stable humus and keeping root pathogens in check. Incidentally the term anaerobic is misleading as such bacteria need oxygen, but they get it from CO2 instead of O2. This means that soil dense with CO2 needs to be cycled in from time to time and then phased out as more oxygen rushes in. Tilling disrupts this cycling in and out.

No, Nature did not err during its millions of years of soil creation, and purposefully established layers, each with a necessary function for soil and plant health. The surface layer is rich in fungi which holds soil together, helping to resist the potential eroding effects of wind and water, and consequent pollution of our streams. Commonly the boundary between soil layers is not distinct so that water, organic matter, microbes, air and nutrients can pass freely from one layer to the next. This has proven to be a much better system than the mechanical mixing we have assumed was an improvement. The surface topsoil layer suffers the most when mixed with lower layers. Even a single initial tilling compromises the soil’s integrity, requiring five years or so, depending on the climate, soils and so forth, to regain its original layered arrangement.

In starting a garden on ground that has been deeply compacted an initial chiseling might be called for, or, in relatively small gardens, “lifting” the soil to achieve the necessary loosening, followed by cover cropping, as advocated in Permaculture manuals. I have found that even with a degraded or chemically dependent soil chemical fertilization can be abandoned immediately with a nitrogen rich mulch like grass clippings.

Our need is for food that is palatable, which happens to be mostly annuals, but perennials dominate in wild Nature.  Annuals are very fast growing which gives them a big appetite, so a particularly deep mulch is needed to supply the necessary nutrients. Wide plant spacing helps in applying thick mulch, which must be added in increments to avoid the matting that occurs with a deep nitrogen-rich mulch. At first the plant roots will not venture far from the mulch layer but in time, with cover cropping and earthworm activity they will forage deeper.

A common criticism of no till gardening is that it would require us to go back to “hunting and gathering”, which is obviously not a possibility with the present large population. Some radical changes are required however. No one needs to go hungry but many of us will go hungry if long-distance transportation of food is not ended.. I feel much greater care would be given to the soils in one’s own country than soils in a far off land. Another change that I see would be in growing more vegetables and fruits and fewer grains, which means a more vegetarian diet. This change would result in increased health and even  reduce the gap between the rich and the poor.

When humankind becomes serious in saving the planet and atmosphere no till agriculture and planting more trees, will become the norm as they are the most feasible way of sequestering carbon.

Nature welcomes each new species since species diversity provides ecosystem stability (self-correcting, self-organising capacity). So She has been heartbreakingly patient and even forgiving in our clumsy (read destructive) attempts to find a home here. It has been suggested, with great urgency, that the reason finding a constructive or creative niche has been so difficult  for us is because of ego-interference, which divides the world into self and not-self.  In Reality however everything arises within Nature, with no such division. Could it be true that saving civilization and the planet is primarily a Spiritual matter in the non-religious sense of transcending the ego? It has been reported that when such transcendence is complete there is not even a separate God.

Abandoning old and deep habits is not one of our species’ strong points in my observation. In most cases there must be compelling reasons to change. So what could compel gardeners and farmers to switch from till to no-till?

It doesn’t seem likely that chemical agriculture will ever switch – finding it so difficult to change to eminently more sensible organic agriculture –until the cost of phosphorus can no longer be passed on to the food consumer, at which point it will die a natural death. Considering the dwindling supply of mined phosphorus in the world this is not too far in the future.

What might compel organic gardeners and farmers to tweak their practices to no-till? Increased cost effectiveness of no-till would certainly be a compelling reason considering our mercenary tendencies, but it is yet not decisively proven to be true. The fact that no-till is much friendlier to the planet – less CO2 outgassing, less water pollution, and so forth – is compelling only to a few.

For me the most compelling reason was a deepening trust, over decades, in Nature’s way – that by an invisible hand Nature is self-organizing and self-correcting, provided she is not interfered with. Through the study of soil I saw that tilling was such an interference.

Nature created different layers, called horizon zones, in producing soil which we in our mechanical tilling disrupt. There is of course the benign mixing by earthworms, bringing nutrients down from the mulch layer and aerating the soil in the process. With that mixing the horizon layers retain their fundamental integrity. Mechanical tilling results in over-aeration and over-mixing, confounding the soil’s integrity. Each layer of soil, including the mulch layer, consists of a different biology (different organisms) and a different color, smell and feel. These layers will re-establish themselves in time once mechanical tilling is stopped and a mulch layer applied. If the mulch layer is tilled in mechanically it decomposes too rapidly for plants to fully utilize the nutrients released, which nutrients may be lost through leaching.

Tilling also destroys many of the proper tillers – earthworms. Further, fungi which are surface organisms are diminished, which organisms play a vital role in plant nutrition and tilth (crumb structure). Some gardeners use compost as the mulch layer but I prefer undecomposed organic matter in a proper carbon:nitrogen ratio. Finished compost is not worm food and also much of the carbon and nitrogen is lost to the atmosphere and through leaching during the heat cycle.

Concerning the fertilizing, must all fertilizers be avoided? In most cases high production is needed before the soil has regained its natural state with horizons clearly defined. What is important is finding a fertilizer that is not overly concentrated and is balanced. The plant itself accomplishes this balancing when such nutrients are derived from those held on clay and humus colloids by exchanging carbohydrates for the particular nutrient needed.

However a plant, in taking in water, must accept whatever nutrients may be in the water, balanced or not. This is why hydroponic gardening is a non-starter. In rainwater minerals are in the proper balance, including nitrogen, though in very small amounts, which gives only a slight boost to plant growth.

Sea water is also mineral balanced however, along coastlines and lakes it has become polluted with certain trace elements in excess, like boron that impairs plant growth. Soils high in humus can buffer this excess to some degree. My suggestion is, if one is going to use seawater, make it infrequent as boron will accumulate in the soil over time. Meanwhile keep building the soil until mineral supplements are no longer needed.

Ocean water requires diluting at a ratio of 30 gallons of tap water to 1 gallon of seawater. I apply this water via a hose end sprayer, the kind where the mixing of ocean and tap water occurs in the cap, not in the jar. My sprayer, even at the highest dilution, mixes at a 40:1 ratio.

For extra nitrogen I sometimes add 1/3 urine to the jar – urine being a reasonably balanced fertilizer and is sterile. For those not having access to ocean water sea salt could be used, though the dilution rate would need to be many times that of ocean water. I don’t have that figure.

Rather than ingesting organic matter that is already in the soil they prefer organic matter at the surface and bring it down deep through vertical tunnels, mixing it with subsoil which provides the grit for shredding the organic matter. Like other earthworms they prefer partially decomposed organic matter that provides them with digesting microorganisms. These tunnels also transport oxygen and water, essential for the survival of both worms’ and plants. Surface mulch, therefore, is needed to keep the worms constantly fed. Even cover crops would need to be mulched, otherwise the earthworms may spend too much time hibernating at the bottom of their tunnels.

Maintaining a certain level of moisture in the partially decomposed litter is important, since earthworms breathe by taking in oxygen dissolved in water through their skin. Not so incidentally perpetual mulch helps stabilize soil temperatures. The organic matter brought deep into the soil, after being mixed with mineral-rich subsoil, is brought to the surface for deposit, keeping the tunnels open. Nightcrawler deposits (castings) contain about 70% humus. Rain washes some of these deposits, or castings, back into the tunnels. Where nightcrawlers exist it’s imperative that tilling is avoided since tilling closes off the vertical tunnels and few nightcrawlers will be found.

Where I live, and in the tropics in general, only shallow-feeding and dwelling earthworms exist. Therefore deep soil is found only on bottom land, where soil has accumulated via erosion from upper lands. Obviously, therefore, bottom land should be preserved for market gardening and never built upon. The challenge I have taken on in my tropical paradise is in finding ways to deepen topsoil, though bereft of the advantage of deep-dwelling nightcrawlers.

Subsoil penetrating roots of cover crops is the primary way of converting subsoil into topsoil. Where there is a hardpan layer deep chiseling may be necessary  initially. Deep roots, upon decomposing, provide humus. The deeper range of such soils will contain less oxygen than the upper layers, therefore less microbial activity, and a more stable type of humus. This humus receives and holds nutrients that may be leached from above. As an end product of decomposition the most stable humus is derived from organic matter containing fibrous materials like lignans, waxes and silica. No humus remains stable, however, under conditions of excess oxygen caused by repeated mechanical tilling.

It is useful to note that tropical soils do not contain as fertile a type of clay as is found in temperate zones (hold fewer nutrients on their surfaces).  Humus can compensate for this weakness as it has a much higher capacity to hold nutrients on its surfaces than even the most fertile type of clay. Deeper topsoil invites deeper roots, which sequester carbon and nitrogen, meaning less CO2 and NO2 in the atmosphere and also results in more drought-resistant plants. All-in-all deep topsoil helps purify the air, puts food in more mouths and, for market growers, more money in their pockets. When the true value of earthworms of all types becomes widely acknowledged surely we will establish a National Earthworm Week?

Fortunately the lower quality topsoil that remains can be upgraded quickly, but not by turning under large quantities of organic matter, as such tilling depletes the key ingredient of inherently fertile soils – stable humus. Through the decomposition of cover crop roots subsoil will also become part of the topsoil complex. In this manner the original depth of topsoil can eventually be achieved. Food can be produced during this soil building process, using high nitrogen mulch.. Applying natural fertilizers and amendments (surface application) can assist the production of food while such supplements are still affordable and/or available.

Soil loss is not only caused by tilling but tilling in combination with subsoil compaction via heavy machinery. Unable to penetrate compacted subsoil much of the rainfall exits the land, taking valuable topsoil with it, often contributing to river flooding. This water is lost for future use, failing to reach underground storage, which capillary action can bring upwards when needed. Oddly this is a commonly overlooked fact, though extremely important, after all you can’t grow plants, even in fertile soil, without water.

To look at the larger picture, industrial agriculture, by exhausting its resource base, proved unsustainable.  Nature has been patient while this lesson is being learned, but now she is telling us that learning time is over and it’s time to apply the knowledge learned. Fortunately we are gaining a lot of information, using computer models to tell us what we must do to keep the planet alive and healthy.  Actually we knew a lot about this before accumulating computer data, but apparently we need computer confirmation. The gathered  information all points towards returning much of our agricultural land to perennials (grassland and forest) that require no tilling or greenhouse gas-emitting nitrogen fertilizers. Perennials, through photosynthesis, pull in carbon dioxide, storing it in its branches (trees and shrubs) and soil (in the form of stable humus), -  the only feasible way to sequester large quantities of carbon. At the present time two-thirds of all arable land is used to grow monocultures of annual grains, resulting in an increase in carbon emissions. Until perennial grains enter the picture diets would need to become more vegetable based. Growing annuals (vegetables) comes closest to the soil building feature of perennials if the soil is not tilled. An increase in large, contiguous areas of unspoiled Nature, with its great diversity of flora and fauna, is needed to stop the now occurring imploding of the earth’s ecosystem Once much of our farmlands are thus converted and balance restored in our air and oceans, agriculture can concentrate on food production.

The largest vegetable growing “farms” in the US are in drought prone areas where water sources are dwindling. Such lands will not be suitable much longer for growing water-hungry vegetables. There is sufficient land to meet all our food needs around and within our cities and towns, thus minimizing  transportation costs and food spoilage. Though our major food-producing areas would come from lands surrounding our towns, even suburban yards could be food-producing, with gardeners hired to do the gardening, as many home-owners now hire out yard maintenance. If these “edible landscapes” were gardened the no-till way mowed lawns would remain to produce needed mulch, though some shrubs and trees might have to be sacrificed. To make one’s yard available for gardening would overcome a major stumbling block for young gardeners – finding affordable land. During the winter season in temperate zones fresh vegetables would still need to come from warmer climes.

The question is what will initiate the shift from industrial agriculture to agroecology, which adapts the principles of Nature to farming systems?  Perhaps climate change and mass extinctions, foreshadowing our own, will wake us up. However maybe even staring into the face of these realities will not wake us up. A common idea is that we must somehow quickly evolve, meaning improve our egos, to save civilization. There is another view coming from someone appearing recently who is seated in Reality. He tells us that evolution of the ego is a false notion and this false view has created an ego-culture which, He says, will ultimately not be survivable.  All of us are, in fact, and always have been, already seated in Reality. We are simply asleep to that fact and it is the ego that is responsible for our asleep state. Thus a life purposed to transcending the ego, rather than ego-aggrandizement or fulfillment, is what must be understood and acted upon. This wise one tells us, when awake, the essential unity of existence and intrinsic value of all life forms will be our everyday experience. This is His Reality and He has given Himself as our Resource in this matter of self-transcendence.

Soil compaction for us no-till gardeners takes a bit more ingenuity to address effectively. More attention needs to be given to maintaining tilth. Tilth is critical, even at the very surface of the soil, as it helps the soil  absorb water to be stored deep in the ground and accessed via capillary action. In my experience watering has been reduced a great deal since I quit tilling and cultivating. With a deep mulch I have not had to water at all, other than the initial watering in of certain plants like tomatoes and squash. My mulch material is limited so I have only one garden bed under deep mulch. Since I don’t need a heavy mulch for weed control I mulch only enough to keep the ground shaded and in a water-absorbable condition. Using cover crops is my way of maintaining the organic matter in the soil, with my main cover crop season being during the winter, so I can free up more beds for garden crops in the long summer days.

Nature has many ways of relieving soil compaction, some commonly known but some not so well known. For example anaerobic bacteria obtain oxygen directly from the organic matter it decomposes, and even oxygen locked into clay particles. This oxygen is released into the soil when the anaerobic bacteria die, promoting aerobic activity.

In general our knowledge of soil is still in the beginning stage. One reason for this is that little can be learned when studying microbes apart from their environment. The vast majority of microbe species cannot live in a Petri dish, which is why only a few microbes have been studied or even known. What is being realized is that cooperation rules in the soil community, and this understanding could rightly be applied to the human community: we too will not survive as independent units of existence. There will always be more to learn about life in the soil community but we know that tilling has a disruptive effect in that soil community. And we know that stable humus is what gives the soil strength (backbone) and inherent fertility. The study of biodynamic agriculture is expanding and should now rightly be called bio-chemical-electromagnetic dynamics. With this expanded version we are on the cusp of learning more about restoring depleted soils and that it can be done much faster than previously thought.

I find it useful to look at industrial agriculture in general as it helps inform even the way I garden in my back yard. We have seen that cheap fossil fuels gave rise to the industrial revolution, which in turn gave rise to the globalization of the economy and the transporting of food crops long distances. I see a different relationship with Nature:  a relationship of greater trust as we strive to adapt more to her ways and away from the present relationship of manipulation and exploitation. There will be a return to a more agrarian society with its typically low unemployment. There will be a move away from machine labor toward more hand labor. Plant diversity will replace monocultures. We will likely need to change our diet away from grains and meat toward vegetables, fruits, nuts, seeds, roots and vegetable oil – in other words the typical Stone-age (Paleolithic) diet. This does not mean going back to Stone Age living since we will be planting our food crops, not just gathering them!

Though cooperation as mentioned will come to rule we know that such cooperation must come from within, from a changed disposition, born out of necessity and not mandated from without. Us soil lovers will no longer be considered weird. Soil will seem more precious than gold.

Just Dirt?

There is a recent study that puts together statistics on soil erosion from more than 125 sources. It says “the US is losing soil ten times faster than the natural replenishment rate while China and India are losing soil 30-40 times faster than the natural replenishment rate”. The study goes on to say “worldwide, as a result of wind and water erosion in the past 40 years 30% of the world’s arable land has become unproductive”. The study also says that the soil that is washed away harms other ecosystems, including our oceans and atmosphere. Obviously a food crunch is on the horizon.

Food production has been artificially propped up by the use of concentrated fertilizers which will soon be priced out of the market as critical fertilizer elements are nearing exhaustion. Not so incidentally, such fertilizers predispose the soil to erosion and eventually soil collapse. The organic agriculture movement addresses soil loss by calling for the increase of the organic content in soils, which helps hold the soil against wind and water erosion. However only 1% of the farms in the US are organic farms. Unfortunately organic agriculture has not yet shaken the practice of tilling which exposes even carbon supplemented soil to the ravaging effects of wind and water, as it destroys stable humus which is the most erosion-resistant organic faction.

To rebuild our soils so they are inherently fertile (not requiring supplemental fertilization) will require huge subsidies difficult to obtain in these economic times. For some time there has been a program in the US to pay farmers to plant the most eroded soils (collapsed in many cases) to native soil-building grasses and forbs and leaving them untilled. But it is the soils not yet fully degraded that can respond much faster to restoration measures and there is no program  of soil restoration for this group. Instead of serious soil restoration programs we have focused on finding new lands to bring into production and of course proceed to degrade via tilling and fertilizing. 80% of these new lands are presently being carved out of tropical forests. This deforestation has huge implications regarding global warming.

We need to replace status quo agriculture with an agriculture that keeps the soil intact and perpetually covered. The steel we pull through soils is not sensitive to the myriad life forms it encounters but we who pull that steel must become sensitized. For cover crops, legumes have particular value in fixing nitrogen but need to be widely spaced for best root growth and nitrogen fixing. Grasses are best to provide maximum organic matter and can in many cases rely on free nitrogen-fixing organisms for their nitrogen needs. Other cover crops, particularly those in the brassica family, are good for root penetration of the subsoil and suppression of soil pests. In terms of spacing they fall somewhere in between legumes and grasses. I see no benefit in using a cover crop mix (with exceptions) due to the need for different plant spacing.

One cannot garden well focusing on these matters alone. The larger environment must also be managed in a fashion that Nature demonstrates. Predator habitats are needed within or surrounding the gardens and in these habitats plant diversity is essential. Frogs have always been an integral part of my gardens and I have provided habitat for them (miniature ponds and bogs) in my temperate zone gardens. Here in the tropics they seem to do quite well on their own.

We need a change in how we study ecosystems. Our conventional approach has been to find the thing that causes problems and then fix it. Recently, however, a new approach is being made that studies systems that are working well and learning about the various interactions that make them work in a balanced manner. Of course it is up to us gardeners to apply this knowledge.

In studying working systems it becomes ever more evident that Nature is on our side. This is in fact a planet perfectly suited for human habitation. We are protected here but Nature cannot protect us from ourselves.

Using nitrogen fertilizers suppresses these free nitrogen-fixing organisms and tilling destroys mycorrhizae fungi that also supplies nitrogen obtained through its decomposition of organic matter, as well as a vital companion to nitrogen – phosphorous.

This brings up the matter of the stewardship of the basic renewable resources – soil, air and water. Although in my articles my focus has been on soils, these three resources cannot be effectively addressed apart from each other. Degraded soils (loss of carbon) result in degraded air (excess carbon) which in turn degrade our oceans – warming and acidifying them, causing climate aberrations worldwide. It is important to notice that the degradation of soils came first, so the secret to restoring balance in the atmosphere and oceans lies not only in reducing fossil fuel emissions but also in sequestering carbon in our agricultural soils where it is critically needed, and not in underground or under water pools where it is concentrated and made highly toxic.

Excess carbon loss from the tilling of soils has contributed as much to the spike in atmospheric CO2 as the burning of fossil fuels. There is a  moral obligation involved in initiating a no-till agriculture, but a study of human nature suggests that people are not in general moved by moral pronouncements unless it involves what is perceived to be one’s self-interest. Of course sequestering carbon is obviously in our self-interest but the information about the best way of doing this needs to be disseminated. And we need those gardeners who already have this knowledge to demonstrate it  to others. There is a learning curve involved in shifting to no-till gardening which must be acknowledged.

My feeling is we can no longer wait for someone to come up with a way to sequester carbon in humus while at the same time tilling the soil!

Perhaps this might indicate that simply mulch gardening would suffice and no cover-cropping would be necessary. However humus resulting from the decomposition of mulch material is relatively short-lived. It is the plant roots that provide the more stable humus, if not, in certain situations, permanent humus. Carbon sequestration is commonly thought of as permanent, not short-term, carbon storage. Roots, of course, add carbon much deeper than just in the topsoil, and over time increase the depth of topsoil. This latter point is very important because most roots, particularly the feeder roots, occur in the topsoil, so the deeper the topsoil the greater the root branching to forage for nutrients and water. Also it is of course important to minimize competition from weed roots. It has been found that early weeding is most critical as it gives the food crop a chance to get the jump on the weed, suppressing it. The best weed control, other than providing a light barrier (mulch) would be to cultivate no deeper than one inch. Below that most weed seeds remain dormant, not having enough light to germinate. Such weed seed may remain dormant for many years so the soil is full of them! It is better to outwit weed seeds rather than try to eliminate them. A shallow (very shallow) cultivating machine I often used in the past is a de-thatcher with flail knives, using it as a seeder, or over-seeder, it puts fine seed in good contact with the soil while grinding up cover crop stubble, leaving a fine layer of mulch. For the control of annual weeds it would be advisable to use it a couple of days before seeding, or refrain from watering a day or two after seeding. Though not cost-effective on small gardens for market gardeners it might provide the courage to exchange it for the rototiller – one of our most soil-destroying inventions.

Sudan grass is becoming a favorite cover crop of mine, sometimes mixed with vetch. It grows fast and deep, likes warm humid weather, and suppresses nematodes. After the first mowing much root die-off occurs which feeds the second growth. It is my common experience that the second growth is more robust and darker green than the first. After the second growth goes to seed the grass conveniently dies. With most of the nutrients in the roots relocated into the seed such roots make for a more stable humus (less tasty to decomposing micro-organisms). The nutrients can be returned to the soil by using the top growth as mulch. Some mulch lifting would need to be done from time to time to keep the seeds from rooting deeply.

Those who make calculations on methods to reduce atmospheric carbon seem totally oblivious to the immense carbon and nitrogen sequestration that would result from a no-till agriculture revolution. The bio-engineering methods of sequestration periodically being floated require vast sums of money, and even if such monies were available, which they are not, are environmentally problematical and in some cases, like dumping excess carbon deep in the ocean, would have consequences that would make our recent oil spill seem like a minor inconvenience.

When we consider the whole matter of human adaptability in Nature there is much we can learn from the non-humans. We observe that their survival depends on whether or not they make a contribution to the ecosystem as a whole. Fortunately we now have credible testimony from a wise, non-egoic Being, that since non-humans have relatively little mind overlay, they are able to see their survival as directly related to the survival of the whole ecosystem. Therefore, for us humans to contact this deep intelligence we must look elsewhere than in the ego mind..

“Converting from conventional plough tillage to no-till practice is among the most cost effective ways to reduce the build-up of carbon dioxide in the atmosphere.” said Atul Jain, a University of Illinois Professer of Atmospheric Sciences.

“When looking at the long-term effects of continuous no-till farming from zero to 14 years, we find a steady increase in carbon levels at the surface.” – Mark Alley (the W.G. Wysor Professor of Crop and Soil Environmental Sciences)

1)    Do not disturb the soil by tilling

2)    Recycle via mulch a minimum of one-third of organic matter produced.

3)    Never leave the soil bare

4)    No concentrated fertilizer amendments

5)    Never leave the soil without living roots

This fifth point has not been given adequate emphasis and there is a way that we can use annuals to behave somewhat like perennials.

Perennials, by continually occupying the soil with roots, provide a constant source of humus. In the case of annuals, after the plant dies there is a gap when no roots are being produced. A mulch gardener hopes to keep a steady supply of organic matter available to the decomposing micro-organisms, but a mulch is not a sufficient substitute for the organic matter produced by dying roots.. For one thing a mulch only provides organic matter in quantity in the surface layer while roots add organic matter much deeper down.

There is another feature of roots generally overlooked:  soil micro-organisms not only feed on dead organic matter, but are also fed by living roots in an exchange process. Roots provide carbon for the micro-organisms’ energy needs in exchange for minerals for plant needs. If there are no living roots to provide this carbon micro-organisms will turn to humus for their carbon needs once the dead organic matter has been exhausted. Mycorrhizae fungi depend entirely on live roots for their carbon needs and provide phosphorous and some nitrogen to the plant.

I see three ways of maintaining live roots in our annual vegetable gardens: One way is to maintain a few weeds at all times, and it has been discovered that this method increases production even though there is some weed competition. Another approach would be to sow a cover crop into the producing crop towards the end of its productive life. Perhaps even the next food plant could be planted before the existing crop has expired. This works best if the crops are planted in rows. And finally there is the Fukuoka method of planting in a living mulch. I’ve tried it with success using white clover in corn and tomatoes.

Though a mulch provides very little humus it still helps in preventing humus loss by keeping micro-organisms properly distracted from attacking the humus. The kind of mulch used has a bearing on humus retention. Mulches high in nitrogen prevent the draw down of nitrogen from the soil but such mulches cannot be applied at a weed suppressing thickness since they tend to mat down. One of the best mulches to my thinking is wood shredded from prunings of the current season’s tree growth. This material has some nitrogen in it to feed the microbes and, having lots of fiber, decomposes relatively slowly, which allows time for “free-living” nitrogen bacteria to proliferate. With the fiber you also get some humus production in the surface soil layer.

Shredding  prunings of course requires a machine as well as material to shred. If such prunings are not available an area would need to be set aside for planting trees for coppicing. Such trees could be planted closely in rows with grass between them providing both wood and grass mulch material. After five years or so this would make an excellent area for a new garden plot. As for a shredding machine, a chipper/shredder would be necessary for a market garden while   home gardeners could put their lawn-mowers to work shredding prunings one half-inch diameter or less. The best mower in general, I feel, is a mower with high rear wheels and good bagging like the low-emission Honda mower which exceeds EPA standards, and is not self-propelled. Self-propelled mowers are more emission-producing, costlier and need more frequent repair.