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Saturday, August 26, 2017

Restoring our soils

This is a book review of David R. Montgomery's book, Growing a Revolution; Bringing our soils back.  I highly recommend the original.  Besides being a real eye opener, it's a good read.


If you prefer, here is the author talking about the book on Youtube
https://www.youtube.com/watch?v=c4p-kQ6D8aA

Prof. Montgomery has traveled the world and documented the work of farmers far and wide who are using these techniques with amazing results.  Even more amazing is that when there is one of these farms right beside another which uses "conventional methods" and the difference in production is blindingly obvious  even at a casual glance, these so called conventional farmers who are using large inputs of agricultural chemicals, very often  stick with their methods.  Prof Montgomery suggests why this is.

In his book you won't find reports of great research done by the agricultural departments of universities.  No university can afford to do the research that has led to these methods.  As the world becomes more and more of a corporatocracy, and multinationals find ever more inventive ways to avoid taxes, government funds have dried up and almost the only source of funding remaining is from these same tax avoiding companies.

No company is going to fund research that leads to less  of their products being used.  If, for instance, a university's agricultural department is being funded by a producer of Phosphate, they will think twice before even having an independently funded research project on site that will show that you can reduce or dispense (for a time) with more additions of phosphate.

Let me quote a small section from the book.  It regards Rattan Lal, a researcher who went to Africa and worked out methods to improve the agriculture of subsistence farmers.  These methods are right in keeping with what is described in Montomery's book.

"Within two years of his departure from Africa, trees were growing through his experimental plots.  The grand experiment was over.  He'd figured out something that would work for subsistence farmers .  So why were his findings all but ignored?

Funders and aid agencies alike wanted breakthroughs and rapid revolutions, not gradual improvement of the soil.  Commercial interests pushed to develop solutions that could be commodified, they wanted petrochemical products, not practices that anyone could adopt for free,  No modern, forward-looking foundation or agency wanted to hear about mulching or growing a diversity of crops.  Such simple answers did not - and still don't - fit the technophilic narrative of progress."

What is needed is demo farms in as many districts as possible run by farmers who are willing to try out these methods, on at least  one of their fields and keep at it for at least three years.

The type of farming mentioned in the book, leads to  a greatly reduced use of fertilizer, pesticides, herbicides and fuel. Note I said reduced, not eliminated.

What is reported in Growing a Revolution is the work of many farmers around the world, usually with no connection with each other.  These farmers would qualify, by any definition, as true scientists, trying things and recording their results and trying again.  There are variations on a theme but what is also amazing is that all these farmers, farming in widely diverse climate and soil types  have converged on the same basic realizations.  It has taken many of these farmers decades to come to these methodologies.  Mr Mongomery's book is an attempt to smooth the way for other farmers so they don't have to go through the same lengthly process.

What then does Mr Montgomery claim that this sort of farming achieves.  Actually, I should rephrase that.  What has he observed that farmers around the world are achieving with these methods.  And notice the emphasis on methods in the plural.  While each method shows some positive results, these methods only truly revolutionize farming when used together. First the results of this type of farming.

Results of this 'new'  type of farming


#  Reduced  inputs including diesel, chemical fertilizers pesticides and herbicides resulting in greater profits even if yields only match "conventional*" farming.  In fact, yields more often than not, rapidly (in a few short years), exceed those of chemical farming.  Profit equals production minus inputs.

* We now think of farming with chemical inputs as conventional since we are used to seeing this type of farming but it is actually a very new way of farming. When we get on to methods, you will see that many of the methods are very old school but modified by recent insights into the biology of soils. So called conventional farming necessitates large amounts of fossil fuel just to produce the materials used in farming.  Add to this the fuel to run the tractor and you are right in the middle of unsustainability.  Reducing these inputs has to be a good thing from a number of points of view.

#  Increased infiltration of water into the soil and the  corollary, reduced or eliminated  surface run off, thus stopping the export of our soils into the ocean. The other corollary of more infiltration, especially with reduced evaporation is less dependence on irrigation and in the case of dry land farming (farming without irrigation) the difference between a crop and no crop.

# Greatly reduced export of  soil into the streams if there is a "weather bomb" and runoff does occur.

# Elimination of wind erosion

#  Greater drought resistance since rain has infiltrated and soils are always protected by a cover crop and/or mulch, which decreases evaporation.

#  Greater flood resistance for the whole catchment since the soils can take up much more water without sending it straight down into the nearest water way.  If a whole catchment of farmers adopted these methods, flood peaks down stream would greatly decrease and with it, the damage to downstream property.  Once the water is underground, it flows much more slowly toward the sea. Not only are peak  flows  reduced but low water flows are increased as this water slowly percolates back into the river systems.

# Water purified before flowing into the streams.  When water flows through a rich organic soil containing reduced carbon*, the fauna of the organic soil scavenges nutrients from the water, reducing the amount of P and N entering the streams.  In addition, pathogens don't have a chance when they enter a rich soil ecology.

* Reduced in the chemical sense as opposed to oxidized.  Reduced carbon is an energy source which plays the same role in the soil that sunshine does above ground. Note that for most crops, the part that we utilize is only a fraction of the whole.  For a grain crop, for instance, we utilize the seeds.  The rest of the plant is a store of solar energy now in the form of chemical energy.  If this store of chemical energy is incorporated into the soil, it powers the whole soil ecology.  If incorporated by using it as mulch on the surface of the soil, it cools the soil, hugely reduced evaporation, and greatly increases infiltration of rain.  The soil organisms at the interface of the mulch and the soil utilize this energy source and pass it on into the soil.

#  Nutrients are held in the soil in a form which is accessible to the next crop in a slow release form rather than a highly soluable form.  This stops the export of nutrients to the nearest stream via the ground water. Streams flow clear again and if adopted widely, dead zones at the mouth of rivers from eutrophication would be a thing of the past. As a result, aquatic life in the streams recovers.  Salmon and trout prosper.

#  Weeds are much less of a problem despite  the use of no-till agriculture and reduced or eliminated use of herbicides.  Weeds are the bane of a farmer's existence.  Montgomery describes how farmers have solved this problem.

#  It is believed here in New Zealand that on well drained soils, when a cow urinates, the urine goes right through the soil into the water table and hence into nearby streams. Organic material is a sponge which will soak up liquid, whether water or urine.  If the organic material increases, not only at the surface but also at deeper and deeper levels of the soil, so much the better.  The following methods increase organic material throughout the soil, both shallow and deep.  Once the liquid is held in the soil, the fauna in the soil scavenges the nutrients from it.

So what are the methods David has observed which are creating this revolution.

Methods

You may have noticed that I have called this a new way of farming.  As I mentioned it is not new methods but the adaptation of methods which were used before the advent of chemical inputs but  with a modern twist in light of modern knowledge. These farmers still use chemical fertilizer where necessary.  This so called 'Conservation Agriculture' is not a religion but a pragmatic approach to farming.

Crop rotation
Sound familiar??  .  No surprises here except he has observed farmers who are using a better way of crop rotation.  If you only plant wheat, this is the worst case scenario.  If you rotate wheat and, a legume in alternate years, this is better.  If you adopt a three way rotation of, say wheat, corn, soy beans, better still but the best system is to rotate as many different crops as is practical and in random time patterns.  This type of rotation confounds the pests.  For instance use wheat barley and oats as your grain crops interspersed with soya, corn and peas.

Note  Corn is a C4 plant and hence produces a lot of organic material which can be cycled onto the soil for the soil organisms.

Most pests are crop specific.  Planting the same crop in the ground year after year allows them to build up in the soil.  Even alternating crops in a two crop system will cause the pests to adapt to this simple system.  You develop a nematode or stem weevil, for instance, that can hold out for a year until the favored crop is returned to the field. A more random schedule of rotation and longer times between the same crop is very hard on crop pests. 

Cover crops
As soon as the summer cash crop is harvested, a cover crop is sown.  The stover from the cash crop is left in the field, preferably rolled into the ground.

In locations where there are harsh winters, the cover crop will be killed by the frost.  In warmer climes, it is rolled into the soil before it sets seeds*.  The frost killed cover crop is rolled into the ground in the spring in the same pass in which the cash crop is planted (direct drilled) into this bed of mulch. The best candidate for a cover crop is a mix of 8 or more different species including:

   * The most effective roller he has seen has projecting steel flat bar in a chevron or diamond pattern.  It chops up and pushes the cover crop into the ground.  It all can be done with one pass of the tractor as the cover crop is rolled into the ground and the next cash crop sowed right into the mulch layer created. The cash crop comes up and shades the soil and any weeds that remain. As the years go by, weeds become less and less of a problem.  The organic matter from both cash and cover crops is left in the field on the surface of the soil.
 
Plants in the cover crop mix include:

# a deep rooter to scavenge nutrients from down deep and to provide a root system that as it decomposes, leaves passage ways for water and air to reach deeper levels.  This decomposing organic material will also hold water better than pure mineral soil, making it available to future crops.  If cows are grazed on the fields, there may be a problem with their large urine output.  If it goes down into the soil and into the ground water it can flow to the nearest stream.  With lots of organic matter, both shallow and deep, the liquid is soaked up giving the soil organisms time to convert this source of Nitrogen* into biomass.

* We had a major kerfuffle here in New Zealand about indoor dairy farms.  As usual the greenies went off half cocked and dismissed them out of hand.  I don't say that indoor farms are always good for animals.  Some can be really horrific.  The devil is in the detail.  One advantage of wholly or partial indoor farms is that you have almost complete control of the waste products that can then be applied to the soil when and in what quantities are most effective and hence least polluting.  When applied this way there is little or no pollution since the pasture takes up the nutrients.  In this connection see Composting barns.

# a shallow rooter to provide a root network holding the surface soil together and a source of organic carbon and nutrients as it slowly decomposes.

# a nitrogen fixer to add nitrogen to the soil

# a nitrogen user (as  all plants are).  They scavenge the left over nitrogen to be released gradually next season as they decompose.  Here you have a slow release fertilizer instead of a soluble chemical that can be washed into the ground water.

# a tuber (radish for instance) which as it decomposes leaves large tunnels  for water to percolate down into the soil.  The decomposing tubers feed the soil life and adds structure to the soil.  Many tubers have very deep roots as well.

A common function of most cover crops (not brassicas apparently)  is that they exude high energy materials from their roots into the soil.  These feed the saprophytes.  Saprophytes not only give structure to the soil but  are able to mobilize nutrients that are not available to plant roots and convert them into a form that the plants can use (notably P). They also act as root extensions, bring nutrients from outside the root zone of the plant. (another reason not to plow and disrupt this system)

The exudates also feed the microbiome which are in turn consumed by earth worms.  The worms themselves are a link in mineralizing* nutrients into a form that can be used by plants.  In addition, they make burrows which  increases water infiltration and allow oxygen** to reach the roots of the plants.

Green plants don't use organic matter.  It must be broken down into a soluble, mineralized form that dissolves in the soil water.  Plant scientists call this process mineralization.

** With a few notable exceptions, plants do not pass oxygen from their leaves down into their roots.  Most need air around their roots to survive.  Worms also provide this service.  Incidentally, if you dig in soil that has been regularly plowed for years, you will be hard pressed to find any earth worms.  After a few years of the type of farming, mentioned in Montomery's book, worms will be back in force.

Different climates and soil types will need different mixes of cover crop species.  This is a rich area for research in working out the best mix of species for specific areas.

No Till
David observes that the plow back into antiquity has probably been a major cause of the destruction of soils.  This is very visible in areas where the Greeks and the Romans held sway.  Much of this land is bare rock.

More recently the plow destroyed the soils of America from the eastern seaboard to the great plains.  We mustn't be too hard on the plow, though.  It may be part of the reason that we haven't already headed into a new glacial period due to the huge amount of carbon that was released from the soil into the air*.
 *See the fantastic book by William F. Ruddiman, Plows, Plagues and Petroleum

Now we have found another way of keeping atmospheric carbon up and can afford to adopt methods that return the carbon to the soil.  We are now in great danger of going too far the other way and putting far too much carbon into the air for our own good. Sequestering some of this into the soil would be a good thing.

No plowing is done.  Seeds are planted by direct drilling.  At most a very shallow groove is made in the soil to plant the seeds and if chemical fertilizer is used, it is placed in small doses near the seeds, not broad-casted over the whole field.  Farmers who are adopting these methods are finding that much less or sometimes, no chemical nutrients are needed. 

Phosphorous, for instance, in their fields is mobilized from the locked up P in the soil by saprophytes and Nitrogen is scavenged by the cover crops and held in a slow release form (their bodies) for the next cash crop. It is also supplied by the nitrogen fixer in the cover crop.

 This doesn't mean that no chemical fertilizers are ever used but they are used as needed.  If, for instance, your soil was found to be deficient in, say, cobalt, clearly you would apply a  cobalt fertilizer to provide for your plants and/or animals.  This is not organic farming.  It is not so called 'conventional' farming.  It is Conservation Agriculture*.  It is not a religion but a  science in which you do what works.

*We always seem to need a label.  In fact it is useful as a short hand once we understand the term so we don't have to go into the whole explanation each time we mention it.  This is it. Conservation Agriculture.

Clearly, if you are continually removing crops from your land, you will need, at some point, an input of the removed elements.  There is nothing wrong with using chemical fertilizers but you don't want your  nutrients to be continually locked up by the soil in a form that the plants can not get at.  That is expensive.

You also don't want your nutrients to seep down below the root zone and be washed into the nearby stream.   Nitrogen can be provided from the air by a nitrogen fixer.  Your input of chemical fertilizer is  reduced and is applied only as it is needed and this shows in your bottom line.

Often, in soils where super phosphate has been used over the years, the soil has a huge reserve of Phosphate but it is all locked up.

The above are the three main methods, namely A)no till, B)cover crops and C)random crop rotation.  In addition there are two more where appropriate.

Grazing
Again not a new system but an old system with a new twist. It is used by some of these farmers. Both crop stubble and cover crops can be grazed and turned into manure and urine which is very good for the soil.  If grazing is used, no roller is needed.  Some of the vegetation is trampled into the surface of the soil which acts as mulch and provides food to feed the soil organisms. The rest is deposited as droppings and urine.  The system that seems most successful is to graze very hard, very infrequently.

Cows, for instance are put on a paddock at a density that finishes all the fodder in in one day and then this area is not grazed again for a year.  This system may have been inspired by a TED talk by Allan Savory on his work in Africa.  This TED talk is a revelation in itself.

No farm, however, can afford to break the farm into 365 small paddocks with fences.  Instead mobile electric fences work very well to allow grazers access to a limited area and exclude them from both the as-yet-to-be-grazed area and the already-grazed area.  One uses a front and a back electric fence.

Many farmers in New Zealand already use this method.  There are probably cases where you would want to let the grazers in more than once per year but the same principle still holds.  Very heavy grazing very infrequently.

Terra Preta 
In warm areas with soil above about 25 degrees C, humus which holds nutrients and gives structure to the soil, breaks down and goes into the atmosphere. Unless nutrients are taken up rapidly by, say, an overlying jungle the nutrients are rapidly lost to the system.  When a tropical jungle is cleared, at most a couple of crops can be grown before the soil is exhausted and the farmer than resorts to chemicals which  finish the damage.

It has been observed, though, that there are exceptionally good soils in some tropical areas, often along major rivers.  These are areas where the locals have incorporated char into the soil from partially burnt bones and plant material.  Char has a three functions.  It has no nutritive value to the plants what so ever but it does provide niches  where the microbiome can live*.

* The organisms in the micro-fauna of a soil usually live in colonies attached to a substrate.  They are not free living like, for instance, phytoplankton in the oceans.  Charcoal provides ideal surfaces and hidy-holes for such organisms and lasts for centuries in the soil.

If you raise chickens you may be familiar with something similar.  If you have a lot of chickens in a yard, before long they will have eaten every bit of green that they find at all palatable.  So you set up a bunch of cages and plant their favorite green inside.  They can only get to the outside leaves so as the plant grows, the chickens crop off the outside but the plant itself is protected and continues to provide greens for the chickens.  Charcoal is very porous and in the soil serves a similar function.

Charcoal, though, has another function.  It can adsorb nutrients on its surface when they are available and release them when in low concentrations in the soil.  Char with respect to nutrients is a little like the hemoglobin in our blood with respect to Oxygen.  In both cases the substance(s) in question is/are taken up easily when available and released when not.  In cooler climes, humus serves this purpose.

Char is probably not a practical option in commercial farming until  and unless we start producing it in large quantities at a feasible price.  One good thing, though about char is that it lasts for a very very long time in the soil.  In a home garden, it is very practical.  All you need to produce char is a 45gal drum.


Note:1  I have just read an article on composting barns by Keith Woodford. This technology would fit in exceedingly well with what Prof Montgomery has reported on.  Composting barns capture all the nutrients, including nitrogen, contained in the poop and piss of the animals,  when they are in the barn. This includes whatever the cows produce at night and when sheltering from inclement weather. When spread on the land it reduces the amount of bought fertilizer needed, and is applied when, and at a rate that most benefits the pasture and hence causes the least pollution (like zero). Compost also provides reduced (in a chemical sense) carbon which provides energy for the soil organisms.

Note:2  Finally,* (Oct 2017) one of our farms has installed a biogas generator to utilize the effluent the cows drop in the milking shed.   The biogas is used to run a motor connected to a generator.  More than enough power is produced to run the milking shed.  Instead of wasting the heat from the cooling of the motor, it is used to heat the water needed in the milking shed**.  A biogas generator only removes C and H from the effluent so, as with composting barns, the effluent from the biogass generator contains all the nutrients in the original poop, piss and spilt milk and can be spread on the pasture when, and at the appropriate rate that benefits the grass and causes no pollution.

*  John Fry of Rodesia sorted out biogas generation from animal waste back in the 1950's.  It is time we learned from the past instead of continually re-inventing the wheel.

 **  When you utilize the heat from a motor/generator running on biogas,, as well as producing more electricity than you use in the shed,  efficiencies of around 75% are achieved.

Note 3  If you were to incorporate sawdust into your soil, and then plant your vegies, you would find that your plants would hardly grow at all.  What is happening here.

The cellulose in wood is simply a chain of sugar molecules which are linked in such a way to make them unavailable to multi-cellular animals.  On the other hand there are many bacteria which produce cellulaze, the enzyme that can break down cellulose and hence, can access this supply of energy and carbon.

With an input of sawdust, soil organisms will flourish but the nutrients will be locked up in the biomass (bodies) of the soil organisms.  As soil organisms eat each other, they incorporate around 10% of the biomass into their own bodies and excrete the rest.  As long as there is reduced cellulose around, the primary producers (in the soil, this is the microfauna that produces cellulaze) will utilize the waste and build it up into their bodies.

As the source of cellulose runs out, the various soil organisms continue to eat each other and release nutrients. At this point your vegies would do just fine.  Soil organaisms  are giving back the nutrients they captured and there isn't enough reduced carbon in the soil now for the mineralized nutrients to be recaptured by the primary producers.


Addendum

Carbon credits

If the government is playing fair with farmers, the farmer should be able to receive a nice carbon credit for switching to this type of farming.  What is first needed is a survey of your farm to determine what is the carbon content of your soil before you change your methods.  You can do this yourself at home if you have a reasonably sensitive balance.  Of course you need an official analysis if you want to pressure the government to play fair.   If I remember my chemistry, the procedure is something like this.


You take a sample of soil, preferably with a corer or a post hole digger that goes down to mineral soil.  You note the depth to which you took the sample and the area of the surface of the core.  A = πr2   (pi r squared)

Thoroughly mix the soil and take an appropriate size sample.

Treat the soil with an acid such as HCl or H2SO4 (battery acid).  This converts carbonates to Chlorides or Sulphates.  Otherwise, when you heat the soil later, the carbonates convert to oxides and it looks as if you have more organic matter than is actually in the soil. When you treat the soil with acid it will likely bubble.  This is the lime giving off it's carbon dioxide.

You dry your sub sample to constant weight at just over 100 degrees C.  ie, you dry it, weigh it, and dry it again.  If the weight remains the same, you go to the next step.  If not, dry again until two subsequent weights are the same.

Put your sample in a porcelain type container that has been dried and fired to constant weight and heat it in the oven to about 500 degrees C.  Start in a closed container but finish with the container open.  You can get appropriate containers from any chemical supply shop.

Burn to constant weight.  The difference between the start and the finish is the amount of dry organic matter in your soil. Very close to 50% of this is carbon You can then calculate the amount of carbon in the upper level of soil down to the depth you cored.  You can also work out the percentage in your soil and the carbon content per hectare.  If you want, you can convert this to the Carbon dioxide equivalent by multiplying the carbon by 44/12 or the weight difference (total dry organic matter) by 22/12.   This is the amount of Carbon dioxide you have sequestered from the air.

1 comment:

Trlahh said...

Hi Hugh, I just saw your comment to Keith's post on composting barns. Looking back, you posted on biochar a couple of times in 2010/11. Nice to see you maintain interest in this, related to NZ farming. We are planning a NZ biochar workshop tour in May next year.
If you are interested in engaging on biochar in NZ, then take a look at http://soilcarbon.org.nz/ and
https://www.facebook.com/allblackearth/
Regards, trevor
http://sea-biochar.blogspot.my/