Mythbusting MOP

One of my favourite programmes finished recently, and to honour it here’s a special blog post.

The myth

The most common way of getting potassium, which is one of the big three nutrients, onto arable crops is to use a product called MOP – alternatively know as muriate of potash, potassium chloride or KCl. It’s the most concentrated and cheapest way of buying potassium. In the soil health world that I occasionally inhabit, there is a strong feeling though that MOP is bad for the soil fauna, and the reason given is that it contains chlorine. I always used to subscribe to this theory, it just makes sense. I even argued with people since I was sure it was right – until my mind was changed. What I’m going to examine here is the validity of this claim, which is what gets trotted out all the time by means of justification:

MOP is bad for the soil because it contains chlorine, which is also used in swimming pools to keep them sterile

The chemistry

The technique of chlorination has been used now for over a century; the first town in the world to have all its water treated was Maidstone, in 1897. There are several ways of getting chlorine (Cl2) into water. You could bubble the gas through the water, but it isn’t very practical. In home swimming pools people often use something like stabilised chlorine (sodium dichloroisocyanurate), which works by slowly and constantly releasing small quantities of Cl2. Public swimming pools and water treatment plants tend to use something like sodium hypochlorite. Wherever we start, we produce the same important acid:

Cl2 + H2is in equilibrium with HCl + HOCl
NaOCL + H2is in equilibrium with Na+ + OH + HOCl

What this means is that we put chlorine gas (Cl2) into water (H2O) and out comes hypochlorous acid (HOCl), and the result is the same when using sodium hypochlorite. This reaction and its products should be familiar to everyone, not just those with swimming pools.

It’s bleach.

Obviously it is very diluted, but it’s this hypochlorous acid that kill all the bugs in chlorinated water.

Now let’s take a look at the MOP (or KCl to use the chemical formula), and what happens when we put that in water.

KCl + H2is in equilibrium with K+ Cl + H2O

What we have here is MOP being added to water, and forming potassium and chloride ions.

As is obvious, there is a fundamental difference here in what is in the water: one of them is bleach, the other is the same as when you dissolve normal table salt. The important thing to realise is that although they are written with the same two letters, “Cl”, chlorine gas is not the same thing as a chloride ion. And to take the point further, it is not a valid comparison to say putting chloride ions into the soil is the same as chlorinating a swimming pool, because the chemistry at work is totally different.

I think it’s safe to say that this myth is

The biology

But hold on!

So dissolving MOP in water is the same as dissolving salt (NaCl) in water? Don’t we all know salt kills bacteria, which is why we use it to preserve food? Yes, that is true, so let’s find out what sort of concentrations of Cl ions we are introducing to our fields when we put on MOP. I’m going to work this out as I go along, with no idea what the result is going to be.

1 hectare of soil, 10cm deep, will have a volume of

10,000 x 0.1 = 1,000m3

We are told that an ideal soil is 45% minerals, 5% soil organic matter, 25% air and 25% water. If that’s the case we have 250m3 of water, which weighs 250,000kg

We now add 100kg/ha of MOP. The molecular weights of K and Cl are 39 & 35 respectively, so of that 100kg we have

100*35/(39+35) = 47.2kg of Cl ions

that means our concentration of Cl ions is

47.2/250,000*100 = 0.019%

What does that mean???

A grain of salt weighs 0.000064799kg, of which 60% is chloride.

So to get the same concentration of Cl ions from one grain of salt (compared to 100kg/ha of MOP), we would need to add

0.00003887*100/0.019 = 0.2046kg of water.

Or to put it another way, 5 grains of salt in a litre of water. To me, that does not sound like it’s going to inhibit much microbial life, but let’s just check if that’s true. This paper shows a much more concentrated (11.68g of salt in a liter of water) solution actually increases the rate at which bacteria multiply. So what do I think about the myth of the Cl ions causing a problem by themselves?

The physics

There is one final MOP myth that I should look at whilst we’re on the subject. It’s that MOP actually affects the soil texture, making it less workable. One common refrain is this:

They used MOP to firm up clay subsoils when building runways during the war

I’ve spent quite a bit of time on Google, and can’t find that particular use mentioned anywhere aside from here, which is where I took the quote from. I’ve also tried looking for articles talking about MOP and soil hardening/texture etc, but only found this one article that mentions the idea. Here is the full paragraph in question. If you don’t want to bother reading the whole thing, it basically says it’s technically possible, but unlikely to actually happen:

The next claim has to do with the idea that K “makes the soil hard” and damages structure. As a monovalent cation, K can, if added in large quantities and given time, displace some of the other cations on soil exchange sites. If most of these exchange sites carried monovalent cations such as K or sodium (Na), soils would tend to “puddle” and be difficult to manage. The number of exchange sites is measured as the CEC, which range from single digits to the 40s or higher, depending on soil texture and organic matter. Each CEC unit occupied by K translates to 780 lb of K in the top 7 inches of soil. The great majority of exchange sites carry divalent cations such as calcium and magnesium, and this will continue to be the case even if we add hundreds (and in many soils thousands) of pounds of fertilizer K per acre.

Finally, I asked a friend (thanks James) to search the academic literature, but he couldn’t find any papers talking about this effect. So for this final MOP myth, I’m going to have to say there’s a bit of a lack of evidence one way or the other, and go for this verdict:

If anyone out there has more evidence on any of this, please do let me know.

The expert

As this isn’t my area of expertise (what is?) I thought it would be best to get the science checked out by someone cleverer than myself. What could be better than finding an academic from one of the top two universities in the country to give it the OK? No one from Hull was available, and since I live close to Cambridge it seemed like a good bet. So I must thank Dr Céline Merlet for her help in making sure my chemistry was good, and for also going out of her way to check my maths on the concentration calculations. It’s much appreciated.

Day 69(ish) – Some data & final thoughts

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This is roughly speaking where I’ve travelled. It’s a little abbreviated in Brazil since that got too complicated to map easily. My time in South America is almost up, but there are a few more things to say, and random pictures to insert.

This lunch on my first visit was exceptional. Why don't we cook beef ribs?

This lunch on my first visit was exceptional. Why don’t we cook beef ribs?

I met a guy from Embrapa yesterday who is running a program near Brasilia where they are comparing conventional and Organic dairy grazing systems. It’s only been going for three years, and I haven’t seen the data (he will email it to me apparently), but they are finding hugely more efficient fertiliser use under Organic management. At the start of the trial both treatments were given the same amount of NPK fertilisers. In the conventional system these came from urea, triple super phosphate and potassium chloride. The Organic sources were animal manures and soft rock phosphate.

"Old town" Montevideo, Uruguay

“Old town” Montevideo, Uruguay

In each of the three years there has been a 20-30% yield penalty (measured by tonnes of dry matter produced per hectare) with the Organic management. However, the critical point is that every year the conventional fertiliser must be reapplied in the same amounts, whereas the Organic field is maintaining its yields with only what was put on at the beginning of the trial. How long will that go on for? Who knows, but already after three years it’s a very interesting result. Whether it could be more profitable to grow crops like this, even without an Organic premium, I couldn’t say; it’s going to depend a lot on the value of the land you’re farming. But it does make you wonder how much of the artificial fertiliser we apply is just being wasted.

Do you ever get the feeling you're missing something?

Do you ever get the feeling you’re missing something?

At a previous Embrapa meeting I was given some scientific papers to take home, and have only just had a chance to read them. One is particularly worthwhile, it’s called “Integrated crop-livestock system in Brazil: Toward a sustainable production system”. The data comes from a 16 year experiment comparing these treatments,

  • CSConventional System using disc cultivation, growing soybeans with a winter cover crop
  • NTSNo-Till System, growing a soya and maize rotation with winter cover crops
  • ICLSIntegrated Crop-Livestock System growing two years of soya & cover crop and two years of pasture
  • PPPermanent Pasture
Lack of water isn't normally a problem in Brazil (lack of power to move it can be though)

Lack of water isn’t normally a problem in Brazil (lack of power to move it can be though)

Here are some of the results that I think are notable. I’ve tried to keep it slightly readable.

  • “the ICLS system treatment yielded soybean production that was greater than or equal to that of CS and NTS. This higher efficiency of ICLS system may be related to availability of P in organic form” – this tallies with the experimental results found by Embrapa Cerrados
  • “Systems with livestock grazing had significantly greater MWD [this is a measure of how stable the physical soil structure is] compared to other systems (ICLS: 4.12mm, PP: 4.93mm, CS: 2.19mm, NTS: 3.18mm) … Ultimately, soils with greater aggregation characteristics are considered of better quality than similar soils with weaker aggregation, mainly because TOC [Total Organic Carbon] becomes physically protected in stable aggregates.” – see the famous Slake Test
  • “Concentration of TOC, TOC storage, and POC stock were increased under grazing by livestock at the following order: CS<NTS<ICLS<PP … The labile fraction of organic matter was also greater in ICLS and PP, than in NTS indicating greater energy flux in the soil system. Greater SOM lability was attributed to the presence of the forage, which adds a greater amount of organic matter to the soil than cropping alone. Moreover, there is a continuous exudation of substances from grass roots to the soil during growth which is stimulated during grazing.”Not very surprising. But it must be noted that of all the systems, it was the NTS which actually lost the most carbon overall. CS was stable, and the other two increased.
  • Total microbial activity was greater in the order you would expect, PP>ICLS>NTS>CS – I’m paraphrasing here a bit.
  • “Density and taxonomic richness of the invertebrate macrofauna [i.e. worms, beetles etc] community in soil differed among management systems. Lowest values were observed in CS, while ICLS was equivalent to that of NTS and PP and greater than that of CS … Soil macroinvertebrates perform numerous essential functions, including decomposition, nutrient cycling, SOM mineralisation, soil-structure modification, atmospheric-composition regulation, and biological control of pests and diseases.”I think it’s fairly obvious by this point what direction this paper is heading in…
  • Hold on, this is a long one: “Weed community analysis showed that areas without pasture and grazing generally accumulated more weed mass than areas that were periodically or continuously grazed. The area of soil covered by weeds was 87% greater in CS compared to the average of the other treatments. Generally, areas that were continuously or periodically grazed by livestock had fewer weeds than areas where only grain crops were grown. Livestock grazing also affected seed germination: weed seedlings from treatments that included grazing took longer to germinate and emerge from from the soil surface. Regardless of the presence or absence of tillage, crop-only systems exhibited larger areas of soil covered by weeds.” – Phew. I’ve never actually seen this information in a scientific context, and the figure they come up with (87%) is huge. Very interesting.
  • “Occurence of Rotylenchulus reniformis [a parasitic nematode pest] differed significantly among management systems, with a much larger population in CS [1500x more than the next highest]”
  • “In years with ample rainfall, soybean production was equal in the three grain-production systems. In years with poor rainfall distribution, with water deficits, ICLS and NTS exhibited smaller productivity losses compared to CS. In 2010/11, for example, CS yielded only 60% of crop production in other systems.” – No big shock here, there’s a reason all the really dry places in the world have gone to no-till. Although it’s amazing they get droughts here when it rains perhaps 1500mm in the growing season. In the tropical heat it doesn’t take long for it all to evaporate.
I'm not usually a big fan of visiting churches, but these two in Brasilia are easily the best I've ever seen

I’m not usually a big fan of visiting churches, but these two in Brasilia are easily the best I’ve ever seen

I’ve found this to be a useful paper, and to me it suggests that the oft-heard fear that having animals in a system is a drain on nutrients/soil fertility is not just unfounded, but actively wrong. Now who wants to lay some water pipe?

I seem to remember there was a cat photo in the last Australia blog too?

I seem to remember there was a cat photo in the final Australia blog too?

It’s certainly been an interesting trip, but I think I’ve run out of steam. The problem is that I’ve seen enough of the details – just look at how different the first blog posts from NZ are – and it is becoming increasingly difficult to find novel concepts. Particularly here in South America, the diversity in farming methodologies seems very limited, and largely defined by what area/climate you happen to be in. There could be two explanations for this: lack of imagination, or perhaps the farmers are more switched on to the research, and unlike back at home, they are all doing the “right” things already. It’s difficult (impossible) to tell, but I haven’t found the Gabe Brown/Coin Seis sort of guy who is trying something totally different… Well I do actually know one, the problem was that he refused to let me visit! The others are probably hiding somewhere not telling anyone about it. That’s a job for a future traveller.

It’s been great fun, but this may be the last Nuffield post. Ciao.


Day 50 – Liquid delivery & snakes

Screen Shot 2014-11-17 at 11.42.05It’s the third time in three days that I drove this road, in hindsight I should have stayed out here really. First of all this morning I had a quick visit to Liquid Systems, who live in an industrial estate in the Adelaide suburbs. They are a small company, started by serial engineer Pete Burgess.

The testing bench

The testing bench

He claims to have developed the world’s best system for delivering liquids fertilisers into a seed trench. Actually it doesn’t have to be fertilisers, they can also put down fungicides, inoculants, acidifiers etc etc. One of the main distinguishing features is how the whole setup is under positive pressure, not gravity fed like a lot of the competitors. This means blockages are less likely, and the flow can be started and stopped much more quickly and accurately. It isn’t quite as quick as an air cutoff sprayer, but not far away; there’s maybe a 1-2 second delay from flicking the switch. The other claim to fame is a much higher working speed range, and all whilst keeping a constant stream as well. John Deere have measured the coefficient of variation between nozzles at 5%. This compares to 75% with some other machines.IMG_4088Section control is available – this means that instead of turning the whole drill off and on, there can be up to 8 different sections, which allows more precise control. Perhaps more interestingly, they are also developing a direct injection system, so that up to 6 different chemicals could be independently applied with variable rates. I suspect this could also have an application with sprayers?

Of course, the bigger question is what chemicals do we want to put down the drill?

My second visit was back out towards the coast again, to see 6th generation farmer Rich McFarlane. He’s another one who has gone away from arable and tilted towards livestock. Again, it was to get away from the spiralling arable input costs, and the very uncertain returns they were making.

Lucerne is pretty much the only bit of greenery around now, aside from a few native perennial grasses that are starting to come back

Lucerne is pretty much the only bit of greenery around now, aside from a few native perennial grasses that are starting to come back

Rich has been rotationally grazing his herd of Angus for the last three years, and is just starting to see some of the native grasses coming back. Amazingly, pretty much all of their pasture is made up from annual, cool season, species. I guess that speaks a lot to how the grazing has been managed in the past. The result is that over summer, the only thing that really grows is lucerne.

They use an interesting variation on rotational grazing that I haven’t heard of before, called the Drewes system. The idea is to vary the intensity of grazing that each field gets each year, to try and increase the overall biodiversity. At the start of year 1, the most productive field becomes the “Primary” grazing field, and the least is the “Sabbath” field. The animals start on the Primary, and then move onto the next in line, and the next,  always moving towards the Sabbath. However, whenever the Primary has recovered enough, the animals are immediately sent back there – and it all starts again. Unless conditions are very bad, they will never reach all the way to the Sabbath, and that field will have an entire year’s rest. The following year, the Primary become the Sabbath, and a new Primary is selected. I’m not sure that is an entirely good idea, but it will be interesting to see how it goes anyway.

Compost extractor

Compost extractor

In the last few years of cropping, Rich had started to use a liquid injector in his drill, similar to the ones I saw this morning (not sure if it was made by the same guys or not). He had been putting down liquid calcium, and phosphate – these apparently don’t mix very well, and often used to block up, but the results had been generally positive. Anyway, in the final year they had started to add into this an extract of compost. It is similar to a compost tea, but without the added bacteria. Basically a few buckets of compost are agitated with water, and out it comes – brown liquid bug food. This went down the drill at 100l/ha, to apparently satisfactory results. No data though, and the next year all the machines went and more cows arrived. End of experiment.

I haven’t see any, but it’s real snake country in this part of the world. Especially next to the lakes, where Tiger snakes like to live. In honour of that, I thought I would just park this amusing video here for some light relief.

Day 45 – More Pasture Cropping

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Reality check.

Angus Maurice is a friend of Colin Seis, and spent over 5 years training people how to implement Pasture Grazing on their own farms. He also taught “No Kill” farming, which is similar to Pasture Cropping, but more extreme. It uses no chemicals at all, and also stipulates the cash crop must be drilled with a disc opener machine, so that there is minimum disturbance.IMG_3991The problem is, he now doesn’t really believe that it works. You can’t say he hasn’t tried, after 7 years of continuous Pasture Cropping and a field that he has left in the system now to see what happens in the even longer term. What Angus finds is that crop yields are just too badly effected – he reckons on average they will produce only 50% of a conventional system. This is obviously a huge drop, and the slight increase in grazing income, plus the reduction is crop growing costs, does not get anywhere near to making up the difference.

As I mentioned, there is one field that has been left in Pasture Cropping, and this year it is growing spelt. It had been attacked by insects earlier in the season and had some pretty big bare patches; however Angus did not believe that was due to the cropping system. But there was no denying that this field looked significantly worse than his conventionally cropped land. It was uneven, and looked at least 3 weeks behind. he is anticipating it will yield half as much as the other fields. It must be said that one difference here is that the fields were drilled with a cash crop every year, rather than once every 4-7 years as at Colin’s farm. Angus says he has tried all different techniques – high inputs, low inputs, but nothing makes it work. He puts this down to competition from the “dormant” grasses for moisture and nutrients.

Angus no longer works as a Pasture Cropping educator.

Angus grows spelt, which yields around 40% less than wheat, but sells for twice the price. It also gives good grazing for his sheep in the winter

Spelt yields around 40% less than wheat, but sells for twice the price. It also gives good grazing for sheep in the winter

My second visit of the day was to the NSW Department of Primary Industries to meet one of their soil scientists, Warwick Badgery (great name!). He too is not a great believer in Pasture Cropping, and has done quite a lot of research into it. I should also mention that both Warwick and Angus do not know of anyone else who has managed to make Pasture Cropping work as well as it does with Colin Seis. Warwick puts this down to the unusual soil Colin has, which is very drought prone, and also very low in nutrients.

[It was plain to see when I visited Colin that the ground was made up almost entirely of granite, not dissimilar to some wine growing regions I have seen. The results of his soil tests did also show very low levels of total P, of around 850kg/ha.]

Warwick does not rubbish the idea of Pasture Cropping completely, he thinks it is a good technique to be able to use opportunistically when conditions are favourable and a cash crop looks like it may be profitable. This whole situation really shows up the fine line between the “it won’t work on my farm” conservative mentality, and the reality that conditions are different on each piece of land. It’s a tricky one.

Warwick has done a lot of work into farmland carbon sequestration rates, and how to maximise them. Apparently in Australia 70% of the nitrogen used by cash crops comes from SOM (Soil Organic Matter) mineralisation. This means that the organic matter is effectively burnt; the carbon leaves as CO2, and the nitrogen (and other nutrients) are left behind to be used by the crop. Obviously this is not sustainable in the long term unless there are recovery periods being used – which is where mixed farming comes in to play. A lot of farms over here incorporate grazing pastures into their cropping land, and this is how they can get away with it.

In Australian conditions, the absolute maximum amount of carbon that can be sequestered is 1t/ha/yr, which works out as roughly 0.3% of SOM. To get this figure a field must be a perennial pasture, and it must have high levels of inputs (nitrogen and phosphorus particularly). Interestingly, he claims that although it is possible to capture carbon without the inputs, it will remain in an unstable form that is easily lost again. On a similar note, I’m told that there are indeed bacteria that will fix phosphorus from the soil, but they only work when the levels are so low already that it would not be possible to grow a profitable crop.

Grazing system trials in Orange NSW

Grazing system trials in Orange NSW

One of the trials that is just finishing now is comparing different grazing methods, and different stocking densities. There are treatments ranging from low intensity set stocking, through to high intensity, long rest systems. The longest rests are around 120 days, which Warwick used to check the claims that this would allow better nutrients cycling and availability. He thinks they are wrong; 120 days appears to be too long for this climate, which is much more temperate than that at any of the other farms I have been to in the last few days.

One of the trials had severe over grazing last year, it was set stocked at a high animal density. The big surprise is that for some reason this year it has come back with incredible productivity, much higher than most of the other treatments. It looks as if either better nutrient cycling (through the sheep numbers), or a plant response to being grazed so heavily, has kicked them into overdrive. Not so surprisingly, the results are showing that with longer rests and higher stocking rates, feed quality and animal performance goes down. This is mitigated though by more efficient plant growth, so more animals can be farmed on a given area. Swings and roundabouts? But more animals and more plant matter must also mean more carbon going into the soil?

There’s no point living in an echo chamber and only speaking to people who agree with everything you already think. I think today was an good one, and although I didn’t hear what I “wanted” to, it has to be better to get the full picture. Even if it does make things more complicated. Excellent.

Days 41 & 42

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Google wouldn’t let me draw a line from Hong Kong to Sydney, which was sad: you will have to imagine that bit. Hong Kong airport is great because if you take the very quick train from the centre of the city to the airport, you can actually check your bags in at the station and then not have to worry about carting them on and off the train. At least it would have been good if my pea-sized brain had not forgotten after half an hour that I had done this: when the train arrived at the airport I spent 10 seconds getting panicked as I genuinely thought someone had stolen my bag.

I have known Cam McKellar since I was 9, as he spent a lot of time at my parents’ house when he was doing a Nuffield Scholarship. Until recently he was an intensive arable farmer with a few cattle, but 2 years ago he made a big switch, and became a big cattle farmer with a bit of arable.

Cam still has some irrigated land, which has to have the pipes moved manually twice a day. I think I would prefer a pivot

Cam still has some irrigated land, which has to have the pipes moved manually twice a day. I think I would prefer a pivot

On his last farm Cam was heavily into home made compost. It was such a big operation that he actually had a full time employee just to make it. The ingredients were simple; straw, manure (cattle and chicken) and water. Within 24 hours the mixture, laid out in strips, will reach 70C. From here on the moisture and CO2 emissions were measured daily, and it was managed to certain tolerances by either adding water or turning it over. After 3 weeks a special blend of microbes is added, and then by 10-12 weeks it is done. Simple.

The finished compost

The finished compost

Although the traditional chemical analysis won’t show a lot of nutrients in here, Cam is convinced that as it is all in a plant available form, then it produces a disproportionately large effect. By spreading 4t/ha he could cut bagged nitrogen inputs by 30%, whilst maintaining or increasing yields. Of course, there is a lot more than just NPK in this sort of thing, and these micronutrients could be what is making the difference. I didn’t see any trial data, but it is still an interesting idea, especially if you have access to cheap straw and muck. After moving farms Cam has stopped producing compost, but he did bring 2,500t with him, which is going on to his new land, mixed with chicken muck, to kickstart the soil biology.

As I alluded to earlier, there has been a big change in mentality, and the core farm business. Although Cam still farms about 750ha of arable land (400 dry, 350 irrigated), the main business now revolves around cattle. There are actually two farms, separated by a 30 minute drive. Both are on what they call black ground, which is some of the best farmland in the country. It is a very heavy, 80% clay, high magnesium soil. This means that although it is very moisture retentive, the plants can have a hard time actually getting hold of the water. This was pretty clear by how brown and dry the landscape is, but then you do not have to dig deep to find moist soil. It’s a little counter intuitive.

These high magnesium clays set very hard when they get dry

These high magnesium clays set very hard when they get dry

Cam has decided that he is going to graze in small cells, with long rest periods. This may sound familiar. The big problem with this, as anyone who has considered it will say, is water infrastructure. They are working hard to put in enough extra troughs to allow cells small enough for daily moves, but it’s a multi-year project to get the entire acreage up and running like that.

Not a pedigree herd

Not a pedigree herd

This herd is not going to win any beauty prizes, and I doubt the meat that comes out of it will be too exciting either. But the system must be about as good as you can get for grazing management and soil improvement. There is no breeding herd, everything is bought from the local market, normally from an east coast farmer who has run into drought problems (“It’s always dry somewhere on the east coast”). They tend to be old cull cows, which then stay on the farm for 60-90 days to put on a bit of weight, before being shipped off to the abattoir.

This has two major advantages. Firstly, because they are there for such a short time, it is possible to say with certainty that they will not run out of food. Cam is not afraid to have an empty farm if either the market isn’t right, or the weather means he does not have forage. Secondly, it retains ultimate flexibility. Pastures can be hit hard, with high grazing intensity, when there is a lot of food, but without any risk of over grazing because de-stocking is an easy and acceptable thing to do. If you subscribe to Gabe Brown’s idea that “cows are a tool” then this must be the gold standard.

I can’t imagine many big arable farmers in the UK switching to the dark side and becoming graziers, but according to a quick-and-dirty calculation Cam did, he is better off now that he was before. That’s in cash terms too, and does not take into account how he is now regenerating rather than degrading his soil. It’s an exciting project.

Day 40

Screen Shot 2014-10-27 at 20.44.45Just a quicky today, whilst en route from Copenhagen to Legoland. A couple of years ago I went to visit a Danish farmer called Søren Ilsøe, who imports and sells Canadian drill openers made by GEN. Although I was impressed by the hardware I never ended up getting them, but that’s another story.

Oil radish and vetch

Oil radish and vetch

Søren reckons he is the only farmer in Denmark who is 100% no-till, and now he has moved on to cover cropping as well. Denmark is interesting as they are very politically sensitive to nitrate leaching, and there are a lot of regulations. For a starter, the maximum amount of nitrogen that can be applied to a wheat crop is 138kg/ha – some people in the UK use double this. It is also a mandatory requirement to have a minimum of 10% of the farm in cover crops every winter, or else you lose another 50kg/ha of N off next season’s allowance. The government is also totally prescriptive on what the cover crop can consist of: there are two choices, neither of which I asked Søren about today, but if my memory serves me correctly from 2 years ago, one is ryegrass, the other is a brassica. No legumes are permitted, which seems a bizarre oversight if you are worried about artificial N getting into water supplies.

Cover crop trials

Cover crop trials

The first field we walked in to had a border of a legume rich cover crop. It was made up of vetch, phacelia, crimson clover, and one plant that I didn’t know, but looked like a very small leafed vetch. It turns out that it was in fact Serradella – a plant that I had been told about, but found impossible to get hold of in the UK. It is a small seeded legume (good), but according to Søren, quite slow to get going (not so good). I will try to buy some off him to try at home next season.

In the middle of this field were several strips of different cover crop mixes that Søren was experimenting with. The plots were

  • Oil radish
  • Winter vetch
  • Summer vetch
  • Black oats & summer vetch
  • Oil radish & summer vetch

Spring barley will be going in as the cash crop, and then the yields measured from each individual treatment. It looks an interesting experiment.

The neighbouring field was drilled on August 6th with a mix of oil radish, peas (a small seeded German variety) and vetch. I was complaining to Søren that our cover crops were seriously lacking in nitrogen this year after the wheats yielded so heavily. Given that they use less N than us, and also got good yields, I had expected the same problem here. I think the best indicator of low nitrogen is a brassica: they just don’t seem to grow when it is lacking.IMG_3805I think it is fair to say that’s not a problem here! How can he get plants like this??? It’s a real head scratcher, but there is obviously excellent fertility in the soil.

Day 37

Screen Shot 2014-07-04 at 07.42.57The last day, and another hastily arranged appointment. I’ve mentioned the Haney soil test in previous blogs, and today I visited Ward Laboratories to see how they do it.

The Haney test has some overlap with conventional soil tests, but it is designed to determine more precisely how much nitrogen and phosphorus will be made available to growing plants through biological activity, not just what is physically present. One of the ways this is accomplished is by using a weaker acid solution to extract the nutrients, which is supposed to be closer to the conditions roots grow in, compared to conventional tests, like Olsen P.

Total carbon, nitrogen and phosphate are measured, as well as their inorganic fractions. When you subtract inorganic from total, you end up with the organic fraction. Inorganic nitrogen is easily leachable, and so if there are high levels they would recommend grass based cover crops to try and capture some of it.

The ratio of organic carbon to organic nitrogen is important, as if it is above 20:1 then no nitrogen or phosphorus will be released through microbial activity. In this situation they would recommend cover crops with higher proportions of legumes to bring the ratio down to between 15:1 and 8:1.IMG_3302

Another novel part of this regimen is the Solvita CO2 burst test. This measures the amount of CO2 produced by 40g of soil in a 24hr period. The idea is that more CO2 = more microbial activity & biomass. They claim that this is highly correlated with overall soil fertility.

All of these tests are combined to come up with a “Soil Health Calculation” score. For completeness, here is the formula: (Try and remember it, there’ll be a test next week)

Solvita CO2 / organic C:N + (organic carbon/100) + (organic nitrogen/10)

The score goes from 0 upwards. A conventionally tilled soil with little or no crop rotation, cover crops, livestock etc may score as low as 2. At the other end of the scale, Gabe Brown’s soil is normally in the high 20s, and they have had a few results in the low 30s. The printout for each sample includes what the results would have been from a conventional test, which in the case of nitrogen is usually less as it has not accounted for the organic forms. This should supposedly allow the application of less nitrogen (if your soils are fertile), and therefore save money.

Interestingly, they claim that with cover crops, the scores are significantly increased as the mixes become more diverse. It does make sense, as presumably different root exudates will feed different microbes, and the total quantity will increase. They also warned that there is normally a 6-12 month lag in seeing improvements after cover cropping, as it takes this long for the biology to work its magic, and make the nutrients available. This would confirm our experience, as well as backing up Fredric Thomas, who sees a gradual decline in the amount of nitrogen he has to apply on his farm in France.

Does is work? Rick Haney, who invented it, is currently analysing yield data from farmers all over the US and trying to correlate it to actual crop performance. I think it is an interesting idea, and may be a useful management tool to at least show that one is moving in the right direction. The test costs $49.50, and I’m going to send in some samples in due course. If anyone else is interested, get in touch and we could maybe combine a shipment.

But that’s it for now, I’m due at the airport in a couple of hours.

Days 26 – 29

I’ve been at the World Congress on Conservation Agriculture for most of this week, hence no blog. It started off with a long and uneventful drive from Bismarck ND where road is so straight and empty that the main problem is resisting the temptation to surf the internet on my phone.Screen Shot 2014-06-27 at 09.06.02The congress was OK, but not great. The talks were pitched fairly low, so didn’t come up with anything particularly groundbreaking. It was good to meet a lot of interesting guys from around the world though, especially some guys doing no-till sugar beet in Switzerland, whom I plan to go and visit.IMG_3208

Soil microbiologist Jill Clapperton gave an interesting talk where she pointed out that intensively tilled soils tended to have a higher ratio of inorganic:organic nitrogen, and it seemed like this favours weed species. I wonder though if by changing this you will just change the weed spectrum, rather than the overall quantity? Another of her stats is that 52% of microbial biomass is associated with roots. If microbes are the real driver for organic matter increases then it underlines the importance of constant soil cover with growing plants.

Another talk from a Brazilian worm specialist (the only one in existence, according to her) showed that we don’t do worms properly – theirs are more like snakes. A few of the panellists that day thought worm numbers were a good indicator of soil health, as they feed on soil microbes, as well as show that there is the “right type” of organic matter present. Some brief Googling shows that perhaps the best way to count worms is to douse the soil with mustard infused water. This should appeal to the inner hippy in everyone.

New Holland branded Quadtrak

New Holland branded Quadtrak

After a fairly poorly attended “Gala Dinner” one evening, there was a panel discussion about cover cropping from 3 American farmers. One of them farmed in what he called the “Mud Belt” – they get 38″ of rain a year and have heavy clays soils. He suggested that it was important to not sow cover crops too thick, otherwise the soil could not dry out quickly enough come springtime. This seems a good idea to me for people in the UK who are worried about exactly this problem. It would probably be easiest to achieve by using wide rows, with the added bonus of less diesel use.

One thing I have learnt is that within this little section of people there are plenty of zealots who know that they are right and everyone else is wrong – just the same as people who know that no-till doesn’t work etc etc. Conditions are different around the world and not all principles are applicable in all locations. Must remember to keep an open mind!

Here are a few quotes that I liked, but probably misremembered a bit:

“Increasing SOM from 1 to 3% doubles water holding capacity” – Dwayne Beck

“If a farmer applies 150kg/ha of N, that uses 3 times more energy than the tillage, seeding and harvest operations combined” – Dwayne Beck

“If you’re operating on the cutting edge then sometimes you’re going to bleed” – Dan Forgey

“If tillage controlled weeds they would all be gone by now” – Dwayne Beck

“If common sense worked all the time, we wouldn’t need science” – a lady on the R4 Food Programme podcast

Day 25

Today I met with a couple of researchers from the Agriculture Research Service. One of them was Kris Nichols, a well known soil microbiologist who specialises in mycorrhizal fungi. The other was Mark Liebig, who is also a soil scientist, but more in the physical rather than biological sphere. I can’t be bothered to structure this as an article, so I will go through the areas that I thought were interesting, point by point.

Mark showed me around the research farm, which has been operating since 1916, and currently has a few trials going on rotations and cultivations. It is not located in a terribly suitable place, as the soils are incredibly resilient, fertile, 2m deep, silt loams. This means that both positive and negative changes to the soil structure and makeup take a long time to manifest. Some of the trials have not yet shown significant results, even after many years, or sometimes decades. Here are some of the things I learnt.

  • Tillage vs no-till trials showed that in most years there was no yield difference. However, in drought years, no-till performed better. I would take from this that there is no point in performing tillage in this location. Mark pointed out that another interpretation was that tillage was generally not harmful, and if it was needed, say in an organic system, then it would not be a big problem.
  • One trial compared continuous wheat with the straw being chopped against continuous wheat with straw removed. Over a period of time (I think 10 years), the field with the straw removed had higher SOM than when the residue was kept. This is obviously counterintuitive. Mark’s explanation was that when the straw was removed, weeds would germinate and grow, before being killed in the spring. This is effectively a free cover crop, and shows the potential benefits that covers can bring.
  • They use a tool called SMAF to measure soil quality. It is “not farmer friendly” and is really a research tool that measures physical characteristics. Often, but not always, the results correlate to SOM levels. The same can be said for humus testing when compared to traditional SOM tests.
  • The fields were last cultivated in 1983, with a chisel plough. Even now, after 31 years of no-till, there is still a compaction pan in some plots. The more diverse the rotation, the less obvious the pan. However, Mark does not think that this compaction is enough to significantly effect rooting, or yield.
  • In a set-stocking grazing system, lower animal density generally results in more native species being lost from the pastures.
  • As in the rest of the world, researchers in the US are uncomfortable giving direct recommendations to farmers!
This is a soil library, with over 5000 samples dating back almost 100 years

The ARS soil library, with over 5000 samples dating back almost 100 years

Now on to Kris Nichols.

  • SOM testing is a useful, but basic metric. It is probably just as good as testing for humus, but neither method actually measures the most useful forms of organic matter. The Haney test is probably the best currently available.
  • Mycorrhizae can link the roots from different species of plants together. For example, a legume and grass growing next to each other can share nitrogen fixed by the nodules on the roots of the legume. This has been scientifically proven using labelled nitrogen, and some 50-70% of the nitrogen present in these grass plants can originate from the legume. She does not know if this means that the grass has any more nitrogen in it that it would have done without the legume present. This lends support to the idea of growing leguminous cover crops in with a cash crop, and then reducing nitrogen applications. I am still skeptical.
  • Crops with higher levels of mycorrhizal associations are more tolerant of drought. This is because nutrients are available in the fungal hyphae, so the plant roots do not have to exude water to extract them from the soil.
  • Plants which are not under stress do not form as many mycorrhizal associations, as there is a cost to doing so, and little benefit. Also, microbes that unlock a particular nutrient are unlikely to thrive if that nutrient is freely available in high concentrations, such as when it is applied as fertiliser. This means that in order to build up the soil life, and therefore increase nutrient efficiency of the plants, it may be necessary to go through a period of plant stress that results in lower yields. This may be 2-3 years in duration. It could be possible to mitigate this either through the use of cover crops, or by weaning off fertiliser rather than going cold turkey.
  • There seems to be a benefit through using livestock to graze plants cover crops, rather than either mowing or drilling directly into them. Experiments have shown that this is not due to microbes coming from the saliva, urine or dung. Kris believes it is due to the grazing action of cattle (and perhaps sheep too?) which rips the leaves in a way what stimulates the plant to produce a burst of root exudates. These in turn kickstart microbial activity in the soil. As long as soil temperatures are above freezing then the effect can be seen. This theory could explain why mob grazing can provide such quick results in soil improvement.
  • Plants take 3 weeks to start forming mycorrhizal associations. Do not skimp on starter fertilisers if reducing total fertiliser applications, so that establishment is not compromised. She also thinks that for this reason it is always valuable to plant a cover crop; even if it does not create a lot of biomass then it will still be feeding the microbes.
  • It is possible that varieties are being bred which make less use of microbial assistance, as they are designed to achieve maximum yields in situations where nutrients are easily available. This may reduce their efficiency of nutrient use.
  • She is ambivalent about glyphosate. Although it becomes inactive in the soil as far as the plants are concerned, she thinks it feasible that there may be an effect on microbial life. The same is true of fungicides, which do not harm mycorrhizae directly, but may do so to the other organisms that are associated with them.

So, once again, no real concrete pieces of research that make anything definitive, but perhaps some more pieces to the puzzle?

One quick fact to end on: a field of oilseed rape in flower produces 100l/ha of nectar. That’s a lot of pollinator food.