Teaser

The travelling is done, and now so is the writing. At some point in the near future my report will be published – here’s the executive summary:

After a few years of working on our family farm, I noticed that some fields performed significantly better than their neighbours, even though the soil types were very similar. The histories of these fields were very different, with the better performing ones having been more recently used for growing grass and grazing livestock. In our case, we found that even after 25 years there could be as much as a 25% increase in yields in fields that had been more recently in pasture. Many farmers realise that these areas always grow the best crops, but there is a reluctance to understand why, or to try and harness those characteristics to improve the whole farm.

With my study I aimed to find out how to measure what makes some fields better than others, and then find out the best way to make these changes in an economic way, and in a sensible time frame. To do this I travelled to New Zealand, the USA, Canada, Denmark, Australia, Argentina, Uruguay and Brazil to look at no-till, cover and companion cropping, and livestock integration. I visited farmers which had decades of soil improvement experience and claimed they could increase organic matter levels by 1% every year, as well as researchers who said this was not possible.

I found that although varying climates in different countries meant the effects happened faster or slower, many modern farming methods are contributing to a decrease in productivity and Soil Health. Cultivations carried out by heavy machinery are causing structural damage and organic matter loss at the same time. Many farms in the first world have specialised towards crop-only production, and away from integrated livestock systems. This is causing Soil Health in general to be reduced as plant diversity is diminished, and the lack of perennial pastures means soil organic matter levels are significantly below their potential. The knock-on effect from impaired Soil Health is increased reliance on fertilisers as plants cannot form symbiotic relationships with microorganisms which help them access nutrients. In addition, this lack of soil fauna also allows plant pathogens to become dominant and cause yield-robbing diseases.

Some of the solutions to these problems are easy, such as changing machinery to allow farming with less soil disturbance, whereas altering crop rotations and growing cover crops may require some investment in the future by possibly sacrificing short term profitability. The most valuable change, integrating livestock, will be the hardest to accomplish in scale. Many have moved away from this type of farming in the last century for economic and lifestyle reasons, but it is only now that we are seeing what we have lost in the process.

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.

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Day 68 – Unrealised potential & realised potential

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One thing that I've noticed is that the plant spacing in Brazil does not seem to be very good. I've had a look at a couple of scientific papers on the subject, and there isn't a definitive answer, but some trials do find quite significant yield losses from poor spacing within the row. I do wonder whether this is an area with some room for improvement, and it's fairly low-hanging fruit.

One thing that I’ve noticed is that the plant spacing in Brazil does not seem to be very good. I’ve had a look at a couple of scientific papers on the subject, and there isn’t a definitive answer, but some trials do find quite significant yield losses from poor spacing within the row. I do wonder whether this is an area with some room for improvement, and it’s fairly low-hanging fruit. In one field I saw four plants on top of each other but I didn’t want to seem rude by photographing it on front of the farmer. No wonder I’m renowned for my diplomacy. 

My car is normally about this dirty, the difference being our mud is a boring browny/grey colour. I am obviously a lot less cool than this guy.

My car is quite often looks a bit like this, the difference being our mud is a boring browny/grey colour. I am obviously a lot less cool than this guy.

In the afternoon we visited another guy farming the usual suspects. What made it interesting was that he had a 50% pasture system, and his neighbour was entirely cropping. I like this sort of setup as you can jump over the fence and see if anything looks different. Here we have three slices of soil taken from very near each other. On the left is from the neighbour's farm (no-till & cover crops, but no grazing). In the middle was the farm I visited (no-till, same crops, but 50% pasture). On the right was from permanent grass on the roadside. It's a very unscientific test, but the samples did follow the pattern I expected. The left hand ample was the lightest of all, which is a basic indicator of lower SOM levels. It also did not crumble into as many pieces, and had more horizontal fracturing, maybe indicating a bit of compaction? The sample on the right was noticeably darker, and much more crumbly. The middle sample was in between the others (literally and figuratively!). What does this tell us? Possibly nothing at all, but it's interesting to see a difference in the soil that, maybe, was caused by a change in management.

In the afternoon we visited another guy farming the usual suspects. What made it interesting was that he had a 50% pasture system, and his neighbour was entirely cropping. I like this sort of setup as you can jump over the fence and see if anything looks different. Here we have three slices of soil taken from very near each other. On the left is from the neighbour’s farm (no-till & cover crops, but no grazing). In the middle was the farm I visited (no-till, same crops, but 50% pasture). On the right was from permanent grass on the roadside. It’s a very unscientific test, but the samples did follow the expected pattern. The left hand sample was the lightest of all, which is a basic indicator of lower SOM levels. It also did not crumble into as many pieces, and had more horizontal fracturing, maybe indicating a bit of compaction? The sample on the right was noticeably darker, and much more crumbly. The middle sample was in between the others (literally and figuratively!). What does this tell us? Possibly nothing at all, but it’s interesting to see a difference in the soil that, maybe, was caused by a change in management.

Day 67 – Integrating livestock in Mato Grosso do Sul

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Who doesn’t want to fly two sides of a triangle to get to the right place? It’s even better when there’s a nice drive in the dark, rain and traffic at the other end. Still, we only nearly died once. This morning all the clouds had gone and it was a short drive to Fazenda Boa Vista. Lucio Damalla is one of the pioneers of no-till around here, he started doing it 39 years ago and is now heavily involved in all of their industry associations. In the afternoon I visited the local Embrapa centre, and met a couple of guys who are working on livestock integration.

Both visits had the same message, which was that having grass and animals in a rotation is going to be better for your soils, and give higher crop yields. The Embrapa guys had done the most work on systems which are 50% pasture (2 years pasture, 2 years crop). I don’t think there is much doubt that this is going to be a more efficient way of farming, the question really then just comes down to economics: can the livestock phase make enough money to be economically viable? I don’t think it can in the UK, not in the good arable areas anyway.

Maize & Brachiaria grass germinating simultaneously

Maize & Brachiaria grass germinating simultaneously

Lucio is more of a crop farmer than a cowboy. He does not breed any cattle, he just buys them in at certain times of year to do some grazing. There are no permanent pastures here, he just uses the Santa Fe system, as discussed on Day 65. Quick refresher – that’s when Brachiaria is planted at the same time as maize in the second crop slot. After harvest, the grass is ready to go, and can be grazed during the winter.

This idea is pretty similar in principle to how we use cover crops, so it’s interesting to see it in action. The benefits are the same as in the 50% pasture system, but just not as pronounced. Lucio has increased SOM from 2-3% in the 10 years that he’s been doing it, which compares to levels of around 4% in the trial rotations with permanent pastures. They both see significant yield increases in following cash crops, due to both the increased SOM, and also the changed physical soil properties. The grass roots open up the soil profile, allowing the cash crop roots to go down further, whilst also improving water infiltration. Although the rainfall here is ~2,000mm, they still suffer from small droughts in the summer, and it’s in these periods that the crops after grass show their real advantage.

The Brachiaria seed rate is important - too much and it will compete with the maize, too little and the grazing benefits are limited. I don't think many agronomists in the UK would be happy with a maize crop that looked like this

The Brachiaria seed rate is important – too much and it will compete with the maize, too little and the grazing benefits are limited. I don’t think many agronomists in the UK would be happy with a maize crop that looked like this

I’ve long had the debate in my mind and with other people about whether it’s best to graze cover crops or not. It seems obvious that by grazing you’re going to lose some carbon (meat & methane), but is it a significant amount? The researchers at Embrapa are certain that it’s better to graze. They say you will get a measurably better crop afterwards (I think most would acknowledge this anyway), but also that it’s better for the long term soil fertility as well. The theory is that soil biology is stimulated by what comes out of the animal (both ends), and they also share Kris Nichols’ opinion that the physical act of grazing a plant causes some (as yet unquantified) beneficial soil effect, maybe by releasing a burst of root exudates. So far so good, that’s basically what I believe. I was really hoping though that thy would have some data on this particular situation, but it seems to be more of a hunch.

As an aside, one of the Embrapa guys, Julio Cesar, had the usual researchers’ habit of answering questions with “it depends”. I teased him a bit about it, and said he was fully qualified to come and work as a scientist in the UK because he wouldn’t give a straight answer or opinion. But it then occurred to me afterwards that when he did say what he thought (grazing cover crops is better), I said I needed to see the data. Maybe they just can’t win?

Day 66 – Coffee

Don’t hold your breath, this is a short post. I’ve never seen Coffee plants before, so this is a very brief description of how they work.

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The young plants are grown in a nursery field until they are 6 months old. They then get transplanted to a pivot irrigator which has been modified to put water on the on the plant rows, spaced about 3m apart. This plant is 7 or 8 months old

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Flowering time can be carefully controlled by starving the plant of water for two months during the dry season. When the irrigation is finally turned back on, the relieved crop sends out all its flowers at once. It takes around nine months for the flower to become a fruit ready for picking. The first harvest is done by hand when the plant is a year and a half old, and the yield will be very small. These plants are two and a half years old, and will soon be harvested with a mechanical picker

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After four or five years the coffee bush reaches 3m in height. At this point it will be cut to stop it growing any taller, because the harvesting machines won’t fit over the top, and the sprayers don’t work as well. Yields in this irrigated land should average about 4.5t/ha, but will go from 3t on year to 6t the next. This farm will soon have 900ha of bushes, which is about half of the entire state’s Coffee area. They also have a pretty substantial factory for colour sorting and grading the harvested beans

Day 65 – Bokashi bacteria brews

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Fazenda Malunga is the biggest producer of Organic lettuce in the whole of Brazil. There are 200m people here, but I don’t think many of them are into Organics just yet. Still, the farm is a big operation, with about 120ha of land in total, 45ha of which is the main, original, block. As well as growing lettuce, which accounts for around half of their production, they also have tomatoes, beetroot, cucumber, coriander, okra, bell peppers, radish (plus some more, I didn’t take notes, oops).

American lettuce - aka Iceberg

American lettuce – aka Iceberg

Because it is an organic farm, they need to get nitrogen from somewhere. [I don’t get this about the Organic movement: it’s fine to mine phosphorus from the soil – rock phosphate – but mining nitrogen from the air – urea – is forbidden.] Some of this comes from leguminous green manures that are grown as every second or third crop, and the rest is comes as compost from the farm’s 70 cow milking herd.

Organic farming does not use chemicals (?). Sulphate buildup can be a problem in these soils, as all of the nutrients they use come in sulphate compounds

Organic farming does not use chemicals (?). Sulphur buildup can be a problem in these soils, as all of the nutrients they use come in sulphate compounds

So although I don’t agree with some of the principles of Organics, [or for that matter think it represents what the customer believes the are getting], we should still be able to learn from how they farm. The over-riding philosophy here is that a healthy plant will fight off disease by itself, with less need for artificial inputs. I’ve written before that farmers are often reactive rather than proactive, and this is made much easier by the way a lot of problems can be solved, in the short-term at least, by opening a bottle. This type of farming is the complete opposite.

These tomatoes are ready to harvest 10 weeks after planting

These tomatoes are ready to harvest 10 weeks after planting. One of the major problems is too much heat; the greenhouse have very little ventilation so that insect pests don’t get in, but this makes them HOT. Brazilians seem to like their tomatoes a bit greener than we do

The main plant nutrition comes from the green manures, home made compost and bought in peat, all of which act on the soil. In addition, they use a lot of foliar sprays, and fertigation (mixing small amounts of fertiliser with irrigation water) to add trace elements. The foliar potions are Bokashi recipes, ranging from straight mineral blends to some which have molasses added to stimulate microbial life. One particular additive, called Compost Aid, is used when they have lost the bacteria off the plant leaves (I don’t know what might cause this). It gives a quick boost to get the bugs back colonising the leaf surface, which doesn’t allow space for too many bad ones to come in and cause problems.

Native microbe powder

Native microbe powder

One of the most interesting things they were doing was living in a sealed plastic barrel, which was full of a damp sandy mixture, smelling a bit like fermenting beer. It was made by taking some of the native soils from out in the bushland, and adding extra carbohydrates as a food source. The top is then sealed and it sits around for a couple of months stewing, before being put into big tea bags and bubbled around in a water tank to extract the goodies. Now it’s ready to be sprayed on to the plants.

I like the idea of this – the native microbes are obviously going to be the best adapted to the local conditions. I’m not so sure about sealing the lid and making the whole thing anaerobic, as that’s not a condition generally associated with healthy plants. At least not the type that we want to grow. The other problem might be that they seem to be thinking almost exclusively about bacteria, and not much about fungi. That could easily be a case of local conditions being different to ours, but if you believe Elaine Ingham, most of our soils are severely lacking in fungal biomass.

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After a quick carbo-loading session (rice, cassava, beans, pasta & potato on the same plate) it was off to a different farm for the afternoon. It is run by a father and son team of Japanese Brazilians, and until three years ago they were a crop-only operation. But then compaction and soil borne disease problems started to appear, and they thought it would be a good idea to experiment with some cattle and rotational pastures. But this is Brazil, and a small trial means 100ha of irrigated Mombasa grass, and 1,200 head of cattle. It’s too soon to draw any conclusions from what’s happening here, but it’s safe to say that grass grows a bit faster here than at home:

A two month old catch crop of Brachiaria grass

A two month old catch crop of Brachiaria grass

Day 64 – How no-till soils are different in Brazil

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Sao Paolo airport has four terminals. In the hour and a bit I spent trying to find a sim card, some reasonably priced Brazilian currency, and a bus to the Ibis hotel, I visited them all, some more than once. It’s a fun way to end the day, especially at 11pm. The next morning I had to fly out early to Brasilia, and luckily I set my alarm as the hotel forgot the wake-up call.

In the afternoon I visited the Embrapa Cerrado centre for a very quick but still useful couple of hours. Embrapa is the Brazilian government run agricultural research organisation, which is apparently very well thought of by the farmers – probably a world first?

The distinct stripes on the left hand plant are due to a Sulphur deficiency. The soil that grew the right hand plant has been treated with gypsum (calcium sulphate) and does not show the same signs

The distinct yellow stripes on the left hand plant are due to a sulphur deficiency. The soil that grew the right hand plant has been treated with gypsum (calcium sulphate) and does not show the same signs

The land here has come out of what they call Cerrado, which is a type of scrub land, but with some tall trees as well. The soil is very deep (they have found roots going down over 4m) and physically well structured. However it is naturally pretty low in fertility, with a natural SOM level of 3-3.5%, and very little in the way of nutrients. It’s also got a pH of 4, and some problems with aluminium toxicity. As a result of this, there are large responses to the standard NP&K fertilisers, and gypsum also has a large beneficial effect both on soil structure & rooting, as well as feeding the plant sulphur. If you ignore these chemical inputs, and farm with tillage, it’s possible to drop the SOM to under 0.5% within five years.

They’ve done quite a bit of work on no-till, which has produced an average yield benefit over the long term of 10%. In some years, growing soya, it has been as high as 40%. They put this difference down to the increased SOM levels under no-till; after 11 years, the tillage plots have 25% less carbon per hectare. This makes a difference with nutrient uptake efficiency in general, but they have specifically tested what happens to organic phosphorus levels – this is the type of phosphorus that is easily utilised by the plant. After 10 years of no-till the organic P is 6% higher, and after 17 years that goes up to 26%.

When this trial started, 17 years ago, it was given 240kg/ha of phosphate. Since then it has had none, and each year the crop has become worse and worse. At this point it is hardly produced any plant at all, let alone a harvestable crop. As a side effect, the organic matter is rapidly disappearing because there is so little plant residue being returned to the soil

When the trial started, 17 years ago, this plot was given 240kg/ha of phosphate. Since then it has had none, and each year the crop has become worse and worse. At this point it is hardly produced any plant at all, let alone a harvestable crop. As a side effect, the organic matter is rapidly disappearing because there is so little plant residue being returned to the soil

Like in Argentina & Uruguay, here in Brazil they are just starting to wake up to the idea of cover crops. One trial compared a standard tillage and summer fallow method (the traditional way) against using no-till and a winter cover crop. The traditional method required 25t/ha of carbon to be put onto the surface to retain 1t/ha in the soil. No-till with a millet cover crop needed 12t/ha to retain the same 1t/ha, and using mucuna (a legume you will no doubt remember from Day 61) meant that number dropped to 7t/ha. The theory here is that because the creation of SOM needs nitrogen, the process is more efficient when there is a legume in the ground. However, the millet produced over double the biomass of the mucuna, so although it is less efficient, if you want to build SOM fast, that (and probably added fertiliser) would be the way to go. It might seem fairly obvious that trying a mix of the two plants might be a good idea, but I’m not sure South America is ready for that concept just yet.

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Eucalyptus trees with an understory of Brachiaria, a widely used type of C4 grazing grass

That was the first half an hour outside, the second was spent looking at an interesting agroforestry scheme. Some of the land has been very badly degraded by over-grazing and poor pasture management, to the point where it is hardly productive any more. One of the solutions Embrapa is looking at is to use crops, grass and trees to turn it around. Also, since us Europeans chopped all our trees down long enough ago that it doesn’t count, we’ve told the Brazilians they can’t do the same to the Amazon. Now they need to find other ways to make their flat pack furniture, and this might be a solution.

Eucalyptus are planted in rows, and for the first two years they can grow three crops per year between the trees: first comes soya, and then maize, both of which can go from planting to harvest in 100 days. A cover crop is planted into the standing maize, so it is ready for grazing immediately after harvest. The same thing happens the second year, except the cover crop then becomes a permanent pasture, as in the photo above. Cattle will graze this for 10-15 years, by which time the trees are tall enough to cut. Eucalyptus has two characteristics which make it ideal for this application. It is very fast growing (in this climate it can average 6m per year), and it will also regrow after the wood has been harvested. Man-sized-cut-and-come-again. Now that the shade has been temporarily removed it’s possible to get in another year or two of cash crops before the trees are too big, and it turns back in to grazing. So the cycle continues…

On a different subject, if you’re looking for something cheery to watch, don’t go and see I Am a Girl, although it is a good documentary. If you do see it, and still feel a bit too upbeat, maybe try Once Were Warriors.

Day 63 – How to make money from farming

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This is going to be a short post, as once again a South American quantity of overnight rain meant that we could not get out into the field. Okara is a company which specialises in using data, both Big and small, to inform land buying decisions for its investors. The idea is to find farmland that is under-valued, or under-utilised, and snap it up for a cheap price.

White is poorly drained, unproductive land. It will only be used for cattle grazing. Blue is marginal crop land, orange is average, and red is good

White is poorly drained, unproductive land. It will only be used for cattle grazing. Blue is marginal crop land, orange is average, and red is good

The first step is to use aerial photos, satellite data, weather recording etc etc to zone the potential land into discrete areas which they think should be similar soil types. This then allows them to go and take soil samples out of these representative zones. This should give a good idea as to the land’s potential, without having to sample everywhere, which would be prohibitively expensive.

In the example picture above, the entire farm (6,000ha or so) was being used for extensive cattle grazing, and was valued accordingly: $4,000/ha. Having performed an analysis, and come up with this map, they found that over half of that ground was actually good or very good for cropping, so their investor bought it.

And the value of cropping land in that area…$7,000/ha

Day 62 – Pasture rotations & SOM

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Today was another INIA day, but at their HQ, with a researcher called Andres Quincke. Here they have been running a trial which is now in its 52nd year, they are looking at the effect of rotations on SOM levels. There are three continuous cropping treatments. Two use the same rotation: maize – barley/sorghum – wheat/sunflower – maize. The difference is that one has been run in a conventional system, and the other without using any fertiliser at all. The third continuous cropping rotation contains soya, sunflower & wheat, with cover crops every other year. This is new though, so there are (I hate saying that) no data yet.

SOM levels in different treatments. Green is 50% pasture, red is 66%, white is  33%. Black is continuous cropping, and white is continuous with no fertiliser

SOC (multiply by 1.7 to get approximate SOM) levels in different treatments. Green is 50% pasture, red is 66%, white is 33%. Black is continuous cropping, and white is continuous with no fertiliser

The remaining treatments use the same cash crops (maize, sorghum, sunflower, wheat, barley) but have differing amounts of pasture – 33%, 50% and 66%. The results are clear and interesting, but perhaps not entirely surprising. Any rotation with pasture will have significantly more SOM than continuous cropping. As you can see from the graph above, the 50 and 66% rotations are getting on for double the SOM compared to continuous cropping, and the trend is still upwards.

These are soil profiles taken from the trial. On the left is a core from the continuous cropping/no fertiliser field, and in the middle is one from the 50% pasture rotation. Although both soils naturally crack vertically, only the pasture rotations showed organic matter going deep in to the profile. It may be fluke that the samples were taken in these places, but it was consistent across all five cores they had on display. On the right is a close up of the higher organic matter soil from about a meter deep

These are soil profiles taken from the trial. On the left is a core from the continuous cropping/no fertiliser field, and in the middle is one from the 50% pasture rotation. Although both soils naturally crack vertically, only the pasture rotations showed organic matter going deep in to the profile (it is very clear, but the lighting was not very good for photographing). It may be fluke that the samples were taken in these places, but it was consistent across all five cores they had on display. On the right is a close up of the higher organic matter soil from about a meter deep. It was also found that soils which had pastures on them were less compacted at depth than those which did not

We’re often told that adding artificial nitrogen fertiliser destroys organic matter, and I’m sure that’s true. In a lab. But in the field it is clear in this experiment that the opposite happens. That’s because with the fertiliser there is hugely more crop residue going back into the soil. That benefits not only the SOM levels, but also massively increases resistance to soil erosion. The photo below was taken in one of the plots with no fertiliser: this happens every year, and does not happen in any of the other treatments. “We have shown now that this rotation does not work, perhaps it is time to change it to something new” says Andres. This has further repercussions too – if tillage creates crops with more biomass, it’s feasible that these systems will produce more organic matter than no-till ones. Something to think about.

Soil erosion in a bad rotation

Soil erosion in a bad rotation

The other striking thing came from a trial within the trial. They decided to look at whether the pasture phases (which all contain legumes) meant there was more available nitrogen for the following cash crops. To test this they have made small plots within the main ones, and have treated a maize crop with zero, half, normal and double nitrogen rates (0, 60, 120 and 240kg/ha). In the continuous cropping plot (with fertiliser), the difference was huge, and the plants with no fertiliser were very yellow and sick looking. In contrast, in the 50% pasture rotation, there was no visible difference between any of themThis was pretty amazing really, but of course you’ve got to wait until harvest to see what has really happened. This is definitely our situation at home; we are addicted to nitrogen.

Top: continuous cropping. Bottom: 50% pasture rotation. In both photos, the plants on the left had 60kg/ha of N, on the right they had none

Top: continuous cropping. Bottom: 50% pasture rotation. In both photos, the plants on the left had 60kg/ha of N, on the right they had none. The colours in the two photos are slightly different as I was facing north in one and south in the other, so the light was not the same

So far so good, but I have two main problems with this trial. The first is with the pasture phases. They have no animals involved. This is an issue because they actually have to bale and remove the residues sometimes, which will obviously reduce, at least slightly, the potential to cycle carbon back in to the soil. Another problem is that grazing can possibly (so says Kris Nichols) actually have an extra beneficial effect on soil fertility, which goes beyond the simple addition of what comes out of the back end of a cow. So although the trials show a significant benefit from pasture, perhaps the effect would be even greater with grazing added in as well?

And there is the elephant in the room…money. They have measured SOC, which goes up. Hooray – but how many farmers, outside the hard core fanatics, are willing to farm just for this? Yields also go up, when taken in isolation. I.e. in the same year, a crop of maize/sorghum etc will yield more in a pasture rotation than in a continuous cropping one. However, they have not modelled overall profitability. Of course this is very hard to do, just choosing what numbers to put in for the value of the crops and beef has a massive effect. But what farmer is going to be convinced to change their system when the researcher cannot tell them if they will make more money?