Claim: Climate change is affecting the dirt (but only in Europe)

Humus depletion induced by climate change?

Stagnating crop yields pose a threat to soil



The yields of many important crops in Europe have been stagnating since the 1990s. As a result, the input of organic matter into the soil – the crucial source for humus formation – is decreasing. Scientists from the Technical University Munich (TUM) suspect that the humus stocks of arable soils are declining due to the influence of climate change. Humus, however, is a key factor for soil functionality, which is why this development poses a threat to agricultural production – and, moreover, in a worldwide context.

In their study, which has been published in Science of the Total Environment (2015), scientists from the Technical University Munich (TUM) evaluated the crop yield statistics for EU countries compiled by the Food and Agriculture Organization of the United Nations (FAO) since the 1960s. The yields for the three most important cereal crops, wheat, barley, and corn, have been stagnating in Central and Northern Europe for 20 years. “The stagnation in yields has only been statistically verifiable for a few years,” explains Dr. Martin Wiesmeier from the TUM Chair of Soil Science in Freising-Weihenstephan and first author of the study. This finding coincides with those of other studies, which confirm that crop yields, particularly in the case of cereals, are falling throughout the world.

“Due to the strong link between crop yields and the input of organic substances into the soil, the stagnation in yields must also have an impact on the humus stocks in the soil,” says TUM scientist Wiesmeier, “particularly in the context of the steady rise in temperatures.” Given that rising temperatures cause higher levels of humus decomposition while, at the same time, the supply of organic substances is stagnating, a depletion of humus must be expected in the long term.

Climate change and changes in EU agricultural policy as possible causes?

The cause of the yield stagnation has not yet been explained but is probably due to a variety of factors: “Following the introduction of new priorities with the joint EU agricultural policy of the 1990s, among other things, less fertilizer was used and leguminous plants were often omitted from crop rotation cycles,” explains Wiesmeier’s co-author Dr. Rico Hübner from the Chair for Strategic Landscape Planning and Management, also in Weihenstephan. “Few authors have discussed this as a reason for the stagnation in crop yields,” he notes.

However, the changes in climatic conditions arising from climate change could represent a far more important factor here: i.e. temperatures that increasingly exceed the optimum level for plant growth, like those experienced this summer, shifts in the vegetation periods, and more frequent droughts. “This inevitably leads to stagnation in crop biomass production and reduced inputs of organic matter into the soil,” says Wiesmeier.

Moreover, livestock numbers in Europe have also declined significantly since the 1980s. “The spreading of organic fertilizer, another important source of organic matter, is also falling as a result,” adds Wiesmeier.

Early signs of a reduction in humus stocks due to the stagnating harvest yields can already be observed. Initial indications of humus depletion in arable soil have been observed in almost all EU countries in recent years.

Interdisciplinary research group

While many previous studies predicted a future increase in humus levels as a result of climate change, based on their current findings, the TUM scientists are critical of this assumption: If the input of organic matter stagnates, soil will lose some of its humus in the long term. “If this trend continues, it could have negative impacts on soil fertility and water storage capacity,” concludes TUM scientist Wiesmeier. “This, in turn, could ultimately result in poorer harvests – a vicious circle,” he adds.

To counteract the problem, agriculture needs to make far greater use of positive measures for the promotion of humus formation. “These include the diversification of crop rotation, the application of green manure and winter greening to reduce soil erosion, optimized soil cultivation, organic farming, agroforestry, and leaving crop residues on fields,” explains Hübner. The study authors also consider that interdisciplinary research on the causes of yield stagnation and humus depletion is essential, “as a single discipline alone cannot solve this problem.”


publication: Martin Wiesmeier, Rico Huebner, Ingrid Koegel-Knabner: Stagnating crop yields: An overlooked risk for the carbon balance of agricultural soils, Science of the Total Environment, August 2015. doi:10.1016/j.scitotenv.2015.07.064


124 thoughts on “Claim: Climate change is affecting the dirt (but only in Europe)

  1. If…could…might… then points out that the problem (if any) can be controlled by traditional farming methods, finishing with the usual, “send more taxpayers money” appeal. Why spend money the european taxpayer hasn’t got on research we don’t really need?

  2. Either that or protectionist trade policy on farm products and heavy farm subsidy rates leading to depletion. No, let’s skirt around the hard issues and go for climate. It’s the year of advocacy Olympic games in Paris anyway.

    • Do the Europeans understand the concept of crop rotation to keep the soil/dirt/earth/whatever viable ??

      • Oh they understand, or at least have had scientific articles and the benefits available for centuries, to enable understanding.

        “These include the diversification of crop rotation, the application of green manure and winter greening to reduce soil erosion, optimized soil cultivation, organic farming, agroforestry, and leaving crop residues on fields,” explains Hübner.

        Other than the Organic Farming, it’s all just standard sustainable, they just choose to be crappy farmers.

      • This has more to do with bureaucrats and business than anything the farmers are doing, they are told by “those that know best” what they can and cannot do to farm and improve the soil.
        One example is the Channel Island and Hebridean farmers who for years even centuries would put seaweed on the fields to improve the land but the EU said it was dangerous because of the Iodine and other trace elements in the seaweed so soil quality and productivity fell and the agrichemical companies just had to supply at great cost fertiliser to replace something they had got for free.
        James Bull

      • They suffer from a huge amount of EU regulation. I know I have worked on a system that deals with farming grants, and I truly pity the farmer in Europe. They have to toe the line.

      • Or the list of banned pesticides fertilisers etc they have imposed since then. As for crop rotation they have in the way they did the figures also ignored the subsidies for leaving fields fallow. The banning of burning the stubble is also a factor in declining yields of cereals.
        As for “….temperatures that increasingly exceed the optimum level for plant growth, like those experienced this summer..” if the Germans were not as insular and inward looking as they accused the UK of being they would know that the high temperatures were not global and we had enough cold to make the average temperatures for the area need the usual cooking if they want to use them to promote the warming myth.
        Perhaps it is time that the engineering signal analyst views on climate being regional changes not global were publicly examined instead of the concentration of climate science clap trap.

  3. So they blame rising temperatures despite acknowledging a reduction in fertilizer use from the 1990’s (there’s their 20 year decline, eh?)…and a reduction in livestock manure being spread on fields, and a reduction in legumes in the crop rotations?
    Nawwww….gotta be global warm….err…global climate chan……err….global climate disruption.

    • You are right on target. Any farmer in his right mind understands this; however, EPA and government policy makers have no idea of “cause and effect.” Just do it and later we will deal with the consequences.

      • “Just do it and later we will deal with the consequences”
        That’s how Asian Carp got to be a reality here in Illinois.

      • Just recently in our part of Canada we were disallowed from using COMPOSTED manures on our fruit trees, now that has to be taken to a landfill , go figure? We now have to supplement our soils and foliage with chemical sprays and fertilizers to grow fruit. The problems are already showing. Tree roots when examined are stunted, the slightest stress ( as in one hot day) causes problems like sunburn ( skins to weak to prevent it) and color in fruit is harder and harder to get. Couple that with the need to have perfect fruit on the super stores shelves and you see the plight of the industry. We are regulated to death. But to me a big thing is the attitude of the consumer, there is nothing wrong with an apple or pear ( any fruit for that matter) that has a slight bit of “blight “on it or a scar from some old bug bite. But that fruit actually can COST the growers to get it processed, imagine your family spends a season growing and working your farm and you get a bill from the processing plant just after Christmas!

    • Also add the decline or absence in conservation tillage wherein abut 30% cover is maintained by minimum tillage operations. This practice reduces soil erosion but also provides organic matter on the soil surface to help develop humus. Winter cover crops also provide organic material to be used as humus when spring tillage occurs. There are a myriad of reasons (poor agricultural practices foremost) why soil humus is decreasing. The colder winters and cooler summers in most of norther Europe during the last ~20 years have not raised soil temperature.
      There are a myriad of reasons, but none of them include climate change (i.e. ACGW).
      The farmers need to be encouraged to use conservation tillage, etc. and then be left alone. When yields increase, they will see (of course they know already but they do have the EU to mess up everything) that conservation measures in agricultural practices bring higher yields, and thus, profits.

    • changes in climatic conditions arising from climate change could represent a far more important factor here: i.e. temperatures that increasingly exceed the optimum level for plant growth, like those experienced this summer, shifts in the vegetation periods, and more frequent droughts. “This inevitably leads to stagnation in crop biomass production and reduced inputs of organic matter into the soil,” says Wiesmeier.
      So which causes the most reduction? The above statement or
      biomass is expected to make up nearly 2/3 of Germany’s renewable energy consumption by 2020. But serving as a source of energy is only one thing biomass does well
      Hard to increase soil levels when you burn them all up.

    • and remember the EU banned GMO, we can’t have anyone improving the crop yields that would be a bad thing

      • yeah?
        20 yrs of roundup = 20 years of killing soil biota
        and no till doesnt open land to oxygen or water..
        not having fallow years to rest soil isnt smart either.

      • Well I don’t know about y’alls “roundup” on the crusty side of the pizza, but over here, roundup is put on the weed leaves, not on the soil.
        We plant out crops in rows, so the fruit/vegetables are where the machine can find them to pick them.
        That means that any green thingie that is not in the crop row, must be a weed. And weeds drink water that is needed for the crop.
        But being a plant, weeds give off chlorophyll signals to spectrally sensitive detectors.
        Dirt doesn’t, so if it’s not in the crop row, and it doesn’t give a chlorophyll signal, it must be dirt, so we don’t spray it with roundup.
        If it is not in the crop row, and it does give a “green light” it gets a custom zap that minimizes the exposure of the soil to the herbicide.
        So roundup ain’t the problem.

      • Weeds are a consequence of “organic” farming.
        California farmers use herbicides on the weeds, not on the crops, so “organic” just gets you more expense, but no better food.
        I don’t pay for organic food; it is just more expensive and no better than regular intelligently grown crops. Plus organic foods have carbon in them which the SCOTUS says is poisonous.

      • Hi george,
        Personally, I enjoy the spicy tang of Malathion on my fruit and veggies.
        I developed a taste for it back in the ’80’s when Gov. Moonbeam Brown sprayed the state for fruit flies.
        (Do I really need to add “/sarc”? ☺)

      • oz, roundup is neutralised on contact with the soil as it is readily broken down by the soil bacteria, it could be said that it improves the soil due to the added phosphate produced in the break down. There are a few chemicals used in agriculture that do not readily break down but Glyphosate (roundup) is not one of them

      • Oz
        Since others have responded to your nonsense about Roundup, I’ll skip that and deal with the rest.
        1. Crops don’t use oxygen, they use nitrogen.
        2.Opening up the land by tilling doesn’t let it gain moisture, it causes it to lose soil moisture by increasing evaporation. The primary selling point of no-till farming is moisture conservation.
        3.Cultivating land to keep it fallow is absolutely the most destructive farming practice. It not only causes a loss of soil moisture, it kills earthworms and micro-organisms that keep the soil healthy. It also causes soil erosion, as the topsoil blows.
        We quit summer fallowing a generation ago, and our organic matter has tripled. The only reason, when they farmed. dad and grandpa summer fallowed was for weed control, because in grandpa’s day there weren’t any herbicides, and in dads day there were only a hand full like 2-4-D. If we continued to farm the way grandpa did, in a couple of generations the land would be barren (I farm in Saskatchewan, and unlike the Midwest, we measure our topsoil in inches, not feet).
        I’m guessing from the number of misconceptions you have (everything you wrote), you must be a city person, as anyone with any kind of farming background would know better.
        I’m under no illusion that a farmer telling you about farming will have any effect , as it contradicts what you read on a blog or heard from your aroma therapist. I have friends and relatives in the city who say similar nonsense and can not be corrected, they just insist they are right and I am wrong (I’ll never understand why people who live in apartment buildings are convinced they know so much about agriculture).
        A few weeks ago, after we had finished spraying fungicide, the topic came up while I was talking to woman in the bar, and she commented that she ate healthy and would never feed her family something that had fungicide sprayed on it, she only ate organic foods. I pointed out that the fungicide is not toxic to humans, but the fungus is, so if you think that the crops from an organic neighbour who doesn’t spray for disease are healthier for you, you are incredibly mistaken. She insisted that the fungicide is a dangerous chemical (it isn’t, I read the spec sheet on all the chemicals we use, as I am the one loading the sprayer), and that organic farmers don’t get fungus problems (?????). It’s like talking to a wall!

    • Pay no attention to the proven, actual impacts of farming practices on the humus (or is that hummus?). It’s got to be the impact of those rising temperatures that are not actually rising.

  4. Some numbers would have been nice . Articles behind absurdly high paywalls have always been annoying. At any rate, sounds like the typical ‘everything is the primary fault of climate change’ even when they present facts like crop rotation & animal input changes being responsible.
    As it is, a non-trustworthy effort – more agitprop.

    • Exactly – ‘suspect’ – third line of the statement – thats conjecture not even hypothesis. After that the content is just so much junk. I was under the impression that cereal yields in Europe as expressed by t/ha had gone up significantly perhaps they are talking about total production but without any explanation of this or any figures in support or in fact any showing of agricultural knowledge at all one wonders how this even got to print

  5. This finding coincides with those of other studies, which confirm that crop yields, particularly in the case of cereals, are falling throughout the world.

    They missed the US, where yields in these crops have increased.

    • The quote is a misstatement. Yields are predicted to fall due to climate change, but I have seen no evidence of this actually occurring. In fact, every number I’ve seen has shown increased yields almost across the board planetwide.
      That is, unless you add in the increased acreage designated to “organic” farming with it’s notable lower yields. That could throw off the average, but it’s a deliberate choice, and those numbers cannot be averaged.

      • You are could be right about the “organic” farming. The ‘Green’ movement has been alive and well in Europe for quite some time now. It would not surprise me if agricultural yields are the latest thing they have screwed up. A quick check of our corn yields in the U.S. show a continuing increase year after year with the exception of drought years of ’93 and 2012 (

      • Thanks Ben. Cereal grain yields have been increasing for decades. Other crops are also producing more. Advances in plant breeding, agricultural conservation practices, fertilizer technology, improved pest control, etc. and rising CO2 have allowed the increases to grow and be sustained over decades. This increasing of food abundance has been a great blessing to the World in the 1900s and so far this century. Improved agricultural practices and cheap energy for mechanization and modern agriculture are vitally needed in the poorest countries.
        Declining yields in developed countries are entirely due to poor agricultural management practices and poor economic policies, over-regulation, more expensive energy (think renewable) and poor leadership (i.e. politically correct policies)–not global warming.

      • they obviously forgot to add ‘according to climate models’ so that we can be assured of the total accuracy of their incredibly well informed and accurate report /sarc

    • This is just appalling research/reporting. Crop yields are are increasing everywhere, just the rate of increase has slowed for the cereal crops. There are many confounding factors in this, not least the large differential in the investment in breeding between cereal crops and corn (which has more commercial developers than the cereals which have tended to be more in the public sector).
      In addition the bald statement:
      “Due to the strong link between crop yields and the input of organic substances into the soil, the stagnation in yields must also have an impact on the humus stocks in the soil,”
      which is made with no support and is completely at odds with all the other evidence of crop improvement over the past 40 years. It was the large change in crop architecture which changed the harvest index (ratio of grain to vegetative matter) that is the basis for the green revolution and which effectively separated yield from the rest of plant growth. Coupled with active soil nutrient management, through specific fertiliser application, stem and root growth have very little relationship to yield and it is the root and stem matter that provide the organic input into the soil.
      The biggest impact on soil organic matter was the switch to annual cereal crops from pastures that took place in the 50’s. This reduced the organic matter significantly as so much of the crop was harvested compared to being left behind. This is changing once again as soil management is now incorporating a lot more reduced tillage – leaving the crop stubble behind and using a lighter harrow as opposed to a deep plough. The impact of this on soil organic matter is so extensive that the organic Carbon sequestered by this approach is calculated as part of the spin-off environmental benefits of agricultural development projects and was even used to garner Carbon credits back in the day when there was an actual Carbon market.
      I worked in legume research in the 90’s and there was a lot of interest in getting them back into the rotation in Europe (they were dropped in the drive for increased cereal production from the 50’s onwards) so to suggest that they were lost due to EU policy changes concerning nitrate run-off in the 90’s is complete rubbish.

      • Also dont forget that stubble burning is all but banned in the UK and elsewhere which has lead to combine harvesters being fitted with choppers to spread and return the chaff and straw evenly to the field. The resultant cry of how stubble burning ‘cleansed’ the field has not really been borne out due to the benefits of an healthier soil flora and fauna

    • Yes, North America was not mentioned and appears to be omitted from the non-posted data to have reached the aforementioned conclusions.
      Also conveniently missing was correlation of soil samples forestland and undisturbed grasslands, bush, savannah etc. to show that this phenomenon is not linked solely to agricultural practices. More likely, the shorter periods of soil thaw produce less humus annually of late.

    • How long to Paris again? You all are going to see an article a day like this for a few months to come 5 minutes to get all over the net and weeks to refute (if ever).

  6. There’s no stagnation of crops in Shropshire so how can it be a global problem? (presumably climate change is not limited to Germany) And what is the optimum temperature for plant growth? Do plants only grow in Europe? I need to study agriculture more, since, having been to every continent, except Antarctica, I seemed to notice not only that England is a green and pleasant land, but most of the world is – deserts aside. The planet is a healthy place – its just that some politicians bribing bogus scientists want to take it over and we want to keep it for real people. Science is about observation and evidence and I do the first and have the second, so this report is like its subject – dirt. Only more like compost, but less useful.

  7. Where I live in the East of England crop yields are tending to increase albeit at a slower rate than they used to. Farmer on TV last night was talking figures of over 12 tonnes per hectare
    What is not taken into account perhaps is that a lot of land has been switched to growing oil seed crops to satisfy EU demand for bio fuels, wheat and other cereal crops seem to me to be shorter in height than they used to be so there is less material to be ploughed back into the soil and there are some farms that sell all the cereal straw to biomass power stations in any case.
    I reckon there must be less muck spreading as well because I certainly don’t experience the good old country smell as often as I did in the past.
    Another recent trend is to leave the fringes of the fields uncultivated to a width of 7m or so to encourage wild plants and provide a refuge for wildlife. I would guess that there has not been any allowance for this reduced area of cultivation. Then there is the matter of solar arrays being installed on crop land because with subsidies etc the return is higher.

  8. Humus depletion – now there is a new one!! I admire their inventiveness. If I were a climate scientist I would apply for funds for research on worms. I fear that by year 2100 the worm number will be dangerously low!

    • Soil depletion is almost always due to poor land management. Not properly rotating crops or allowing excessive erosion and runoff. It doesn’t make for as good a story, but it gives actual reasons and solutions instead of pointing fingers.

    • Actually, no it isn’t a joke. Organic carbon in US soils is decreasing due to intense use, not due to climate change. This has the effect of decreasing the amount of water the soils can absorb and retain. The added runoff carries nutrients to the streams and to the Gulf. Worm health is an important part of the system.
      I do have my own little project in increasing the absorption of water into soil, though it’s in an urban area rather than rural.

      • If we were to stop ethanol subsidies in the US, much of the good agricultural conservation practices would return to the corn belt (the region with most negative impacts)

      • Leonard: Ethanol subsidies disappeared a couple years ago, and those went to the blenders (petroleum companies) not the ethanol producers. There may be some remaining subsidies for cellulosic ethanol which is a tiny part of the market, there are none for corn ethanol. What ethanol has is an assured market, but no subsidy.
        Before you can return to good conservation practices you have to have followed them in the past. No-till has just caught on in the last 10 to 20 years: after being pushed since the 1960’s. Planting winter cover crops is only beginning to make a dent.

  9. If only the “climate research” B/S could be ploughed into the land… Maybe the papers could be recycled into fertilisers?

  10. The diversion of straw from cereal crops (which used to be returned to the soil) for processing into “renewable” ethanol “biofuel” couldn’t possibly be relevant could it? No of course not!
    Now imagine the degredation of the vast areas of the US where 40% of the new corn crop is used to replace the old stored solar power of fossil fuels.

    • The use of corn for ethanol leaves the stalk of the plant in the field to decay and reenter the soil as humus. Cellulosic ethanol removes that stalk from the field, leaving the soil unprotected from soil and wind erosion and further contributing to the loss of the organic content of the soil.

  11. “The yields of many important crops in Europe have been stagnating since the 1990s. As a result, the input of organic matter into the soil – the crucial source for humus formation – is decreasing. ”
    Seems to me they have the cause/effect relationship mixed up

    • Could be. But they also provide free advice to farmers, which is highly valued by them. I can’t imagine how they greet with deep joy all this new information.

      To counteract the problem, agriculture needs to make far greater use of positive measures for the promotion of humus formation.

      Captain obvious is around.

  12. Humus formation and depletion in an agricultural system is controlled by so many operational variables (type of crop, number of harvests, timing of activities, winter fallow condition, rotations, re-spreading residues, etc.) there is no basis to assume climate is a primary driver. I’m not willing to pay for access, so it is hard to evaluate, but the press release sounds like this is not a proper analysis but an opinion piece based on conjecture from a couple factoids and calculations. The final recommendations are not necessarily bad ones, and are just repeats of good soil management principles that have been around for decades, which leads me to conclude this is just another case of pimping oneself to the AGW money machine to pay the rent.

  13. “This finding coincides with those of other studies, which confirm that crop yields, particularly in the case of cereals, are falling throughout the world.”
    Not true, it’s the exact opposite. They start with a false assumption in order to get where they want to go in this study.
    Question is not whether they are wrong but whether they are doing it intentionally or somehow oblivious regarding the actual facts about climate change and crop yields?

    • It should be noted that crop yield is different than production. Yield is typically on a per area basis. It is plausible that total production could go up, while yield “stagnates”, if more area was put into production each year. I have no idea if that is the case here.

      • MJB,
        You make a good point. I don’t have a global crop yield or global acreage graph handy but for sure a crop like soybeans has had increases in acreage planted the last few decades, especially in South America, with Brazil leading the way.
        I do have a yield graph from US grains, this one of corn going back 30 years. Yields have clearly been increasing(trend line yield in a steep incline).
        You can note the bad yielding year 1988-drought 1993-flooding 2012-drought.
        You should also know that the period between widespread, severe Cornbelt droughts from 1988 to 2012 was the longest period(of consecutive years) in recorded history for that region……….a case for the best weather and climate since we could measure accurately.
        However, the 1993 flooding from excessive June/July rains(one of those 100 year old excessive rain events), caused enough damage so that, at least in the 1980’s/90’s crop growing weather was not that good. We had droughts in 1980 and 1983, just prior to the start of this graph.
        If you want to sort of cherry pick or just take the most recent 16 years, you could say that growing conditions, other than 2012 have been almost like a greenhouse.

      • certainly in the UK area under tillage has gone down, the increase is due to increase in actual crop yield of 2t/ha pre 1940 to the already mentioned 12t/ha now

    • Thank you Mike, I was looking around the internet for that very graph. This study starts with a false premise and it’s not clear to me that they followed it up with any empirical research. i.e. they didn’t get their hands ‘dirty’ so to speak.

      • As Lincoln remarked about Gen. Pope’s “HQ in the saddle”, their headquarters are where their hindquarters ought to be.

  14. The perils of monocausal attribution!
    This comes from my Alma Mater. 🙁 They have been talking about this for the past 40+ years, and they have been talking about this when I was a student of Ag Econ there. The mention of climate change keeps the funding flowing, certainly the most important goal of any study. /sarc off
    Beta pug makes a very good point in addressing the fact that many farmers use crops or crop residue for bio fuel production.
    To be fair, the study mentions several factors affecting humus depletion. IMHO climate change is really only a significant factor as far as misguided public policies cause the removal of biomass from the fields in the first place.
    What seems not to be mentioned in the study or emphasized enough is how generational change and the consequent change in the structure of the farms have affected this. Old farmers farm until they retire, but especially on small farms their children do not take up farming. They go into other jobs, especially in the former West Germany where unemployment is low and farm sizes are small and they rent out land to larger farms.
    Between 1960 and 1990+ the level of professionalism in farm management has risen, as have crop yields, as smaller farms went out of business. Once the majority of the farmers are professional farmers (and not moonlight farmers as those whose paycheck mainly comes from factory work are called) the yields start to level off as improved cultural practices no longer have an outsize effect.
    The number of farms declined dramatically throughout the EU, as did the livestock numbers per acre, while farm size in acreage terms increased.
    Smaller farms are by law allowed a higher number of animal units per acreage than are larger farms to give them higher income per acre. The problem was too much manure was affecting ground water quality. Larger farms = less livestock per acre.
    In the 1970s and 1980s the European Union spent most of its funds on subsidizing crop prices, a policy that turned out to be unaffordable. The two oil crises in the 1970’s dramatically increased fertilizer prices and Diesel prices. The increase in Input prices and the lowering of crop price subsidies, replaced by direct subsidies directed to smaller farms to keep the voters of the conservative parties happy, created a downward pressure on yields, one of MANY factors influencing yields.
    There are many more relevant factors but I feel I have already taken up too much space.

    • Yes, that is entirely too much space for a comment. I must insist you write up a full piece for Anthony to post as it’s own article. You seem to know far more about this than those who somehow made it past peer review.

  15. I want to do a study to see if “humus depletion” correlates in any way with the “hubris depletion” of the CAGW group…👍

  16. Ironically, in the US, we use 35 million acres of the most fertile soil in the world to grow corn to be used for biofuel/ethanol.
    Turns out, that it pollutes far worse than any other energy source. Fertilizers, pesticides, herbicides that run off…………and uses up billions of gallons of fresh water.
    Unless of course, you want to call CO2 pollution. Then, fossil fuels pollute the most.
    Sunshine +H2O + CO2 +Minerals = O2 +Sugars/Food
    So, do we actually have:
    Sunshine +H2O +(Beneficial gas) +Minerals = O2 +Sugars/Food
    Or is it:
    Sunshine +H2O +(Pollution) +Minerals = O2 +Sugars/Food
    The planet greening up, provides a powerful, objective response to CO2 in our world to point us in the right direction.
    Humans making up stuff about cereal crop production and speculating about the future using models from a broken theory provide us with a powerful, SUBJECTIVE response to CO2 in our world to point us in the WRONG direction.

  17. The main reason wheat and barley yields/ hectare have stagnated is that the ‘green revolution’ cultivars have reached full penetration, and in Europe other inputs (fertilizer, pesticides) have been optimal for decades. Reason for declining humus is stover used for biofuels rather then plowed back in. Half a degree C has zip impact on soil biology in temperate Europe where it snows in the winter and is hot in summer.
    The main reason maize (corn) yileds have stagnated in Europe is opposition to GMO.
    Both facts amply illustrated graphically not just for Europe but for the globe in ebook Gaia’s Limits.

  18. It was in the early 1980s that I first came across studies of German (and I believe other European) policies which had ended stubble burning and ensured the reincorporation of stubble by ploughing or disking back in.
    At that time the studies showed that the quality of the topsoil after some 12-15 years of this had improved dramatically. Humous and organic levels were significantly higher as were resuting nutrient levels along with better water retention and a looser structure which helped root structure establishment.
    I seem to recall they also projected that it would be a further few years before the Maximum soil improvement benefits from this would be seen – partly because of the depletion in organic material that stubble burning over many years had caused that it would take a long time to replace – and partly because the rate of decomposition of organic material was strongly linked to the nitrogen levels of the soil; as the organic material decayed it would initially take more nitrogen from the soil but after time this would balance out.
    The UK was just about to adopt similar policies (EU intervention) and around 1984 or 1985 banned stubble burning.
    Seems to me that with a timescale of 15-20 years for the maximum Increase in Humus to be achieved it would be around the end of the study period in the article above.
    Without looking backwards to understand or appreciate why Humus levels had been Increasing then it is perfectly possible for these researchers to mistake the levels reaching their maximum and not increasaing further as a sign that they are in or about to decline.
    A number of other agricultural factors and practices (including reduced nitrogen input) will also affect the humus levels and others have written of these above.
    Aside from all of that every report has shown a steady Increase in cereal and other crop output on a global level.
    There is every likelihood if not absolute certainty that this Increase in Crop Yields has been greatly assisted by higher CO2 levels which are so beneficial to all plant life.

  19. Bah, you guys are missing the big picture… Once again you demonstrate you just don’t “get” climate change.
    There is a strong correlation between humus produced and the number of earth worms present in the soil. Climate Change is obviously causing a mass migration of earth worms out of Germany and into bordering countries. In fact, I heard on the news that Hungary might be building a wall to stem this illegal Annelida migration.
    England may be safe, that is until earth worms learn to build rafts…

  20. The FAO has a different take on EU cereal production. Production is rising slightly, but yields are up over the last 20 years. I have not looked at the other crops, but cereals at least are increasing in yield.
    Data here.

  21. Cereal yields are dependent on the many factors, but especially soil moisture and the heat units during the growing season, such that both Winter and Spring wheat are very dependent on the winter weather and the timing of the start of Spring. If there is a severe Winter or Spring frost there will be winter kill that then requires reseeding or patching the crop. The conditions at tillering and flowering are important too and especially the timing and accuracy of nitrogen fertilizer and agrochemical sprays.
    If weather conditions are favourable, the Laloux tramline system combined with precision equipment using GPS allows the most efficient farmers to achieve high yields. This is seen in the UK where the average farm wheat yield has increased from 7.4 te/ha in 2013 to 8.6te/ha in 2014 – hardly stagnation
    But the most efficient farmers using precision methods commonly achieve yields of c.a. 12 te/ha and the record is currently 16.5 te/ha
    Turning to Germany and using more valid statistics we find that wheat yields are up by 19% from 1985
    And this in spite of a long term cooling trend – the increased temperature in 2014 was accompanied by increased yields of cereals.
    Finally, farmers do not go for maximum yields but attempt to maximize their gross margins, such that if they determine that prices will be low they reduce the inputs, especially of fertilizer and agro chemicals with a resulting drop in yields. This accounts for much of the variability in annual yields:
    That is not to say that soil organic matter is not important, it is, but other factors than climate are involved, especially the short length of straw of the high yield varieties now grown and the ban on burning the stubbles such that straw is removed from the fields. Add to this the switch of the more fertile wheat areas into maize for the production of biogas and it is no surprise that there has been a fall off in the rate of increase in yields. But as the UK record shows the better countries in the EU are operating at the moment at only half of the yield potential and others at much lower levels.

  22. The cause of the yield stagnation has not yet been explained</blockquote
    Perhaps we have a new proxy for The Pause 🙂

  23. Cherry picking? This study appears to be a BOWL of cherries.
    SOME countries show a stagnation of SOME crops, but only since about 1996. If one takes all the EU (or even all Europe), and all cereal crops, there is an increase in yields. If one changes the year to 2005, then there is a noticeable INCREASE in yield,(except the UK).
    From the dates and inflections in the curves (notably 1990 and 1996), it appears the breakup of the Soviet union is driving most of the trends. yields fell about 1990, then picked up quickly by 1996.

  24. It is obviously down to the concentration of organic waste in the research departments of certain universities. That would explain a lot of other recent degradation in quality of yields in all sorts of areas including, and certainly not the least, public administration.
    Bovine manure in particular seems to have been very largely diverted to the academic market.

  25. Yield is different from production. Production is a function of several factors including yield level, irrigation, area under cultivation, fertilizer use, etc. I presented an article — a chapter — in a book wherein I showed the paddy yield steadily increasing with chemical fertilizer use. This was 2000 kg/ha and due to seed improvement 500 kg/ha over the traditional ones of 1300 kg/ha. All these are under irrigation. Since 1983-84 the yield level presented a more or less plateau. This is due to soil degradation as well seed’s ineffectiveness beyond certain limit of fertilizer use. No new technology was invented afterwards. Though Genetically Modified seed was introduced, the yield is not improved as the seed and chemical fertilizer and irrigation are the same as the seed is same as earlier seed — only a trait to control pests was introduced but other pests affected the yield. The chemical input mono crop technology severely affected animal husbandry and thus security to farmers was reduced resulting more economic losses, nutrient losses. We need organic traditional agriculture that links animal husbandry to improve nutritional security along with economic security. We are wasting food to the tune of more than 30% of what we produce.
    Dr. S. Jeevananda Reddy

  26. Gaudeamus igitur,
    Juvenes dum sumus;
    Post jucundam juventutem,
    Post molestam senectutem
    Nos habebit humus.

    [New Yorker, 2/14/53]

  27. From what I’ve seen of farming, and that is a LOT of it, in Europe it is far more common to harvest whole-crop than to leave material on the field. This means wheat leaves no chopped straw, corn is usually chaffed and the large production of potato and sugar beet will deplete soil rapidly. There are fields in Europe that have been cultivated for so long that through soil depletion they’ve become the bottomlands in their area, literally farmers growing themselves into holes.
    Compare that to the US with little current reliance on chaffing for feed, higher use of hay than chaff in fact. Spreading chopped straw on fields, fields forced fallow and fields paid to be fallow by the federal government and you’ll see a slowly developing difference.
    Now, this Humus depletion is something I am EXCEPTIONALLY familiar with: I spray yards in Central Florida. Due to the average household agronomy and the way St Augustinegrass grows we have a common situation in which the original sod will deplete its installed mass of humus and sub-thatch over a period of a decade and the newer rolled sod starting out with even less humus and sub-thatch lasts an even shorter time; sometimes only two years.
    To combat this I have the customers do one thing: mow higher. This allows the soil to be protected from sunlight and wind. (St Augustinegrass actually prefers 4″ for lawngrass and 6″ for best management coverage) When they mow higher I can use a moisture management compound to help the ‘soil’ that remains – mostly just sand and dust – start to retain biological material. Over a period of years this increases the biological material load of the sand and dust until it starts to resemble topsoil again. Something on the tune of two years to start the capture and retention then a developing topsoil layer of about 3mm per year after that. 3mm may sound small but it has a MASSIVE result in the nutrification, moisture retention, positive biome development and downright terraforming of most lawns down here. I have yards I started on this six years ago that are able to go up to ten months without nutrification and fertilizer with NO retardation of coverage. Coverage is the important one.
    Now I *DO* add micronutrients to my spray mixture as well as potassium and nitrogen (the fertilizer is more to offset the selective herbicide’s effect on lawngrass and to keep the weeds pumping up so they die faster). A glucose based chelate containing eighteen components which is foliage absorbed and reduces the lawn’s need to digest soil. We used to use either Iron or Manganese chelates and all these did was super-green the grass and cause it to consume the ground quicker.
    So what I see year round is fields that nobody lets go fallow. Fields that are constantly sprayed with herbicides, fertilizers, pesticides, micronutrients and other compounds as needed. They’re never allowed a year off and they’re constantly harvested. And their topsoil humus depletes as fast as a root vegetable crop’s does.
    Somehow care for the land has become less important to Europe’s agriculture community and I’m afraid they’re gonna learn the lesson we learned from Texas to Kansas in the 1930s.

    • I’m sorry thats just not true, however farmers find their jobs considerably harder when ignorant politics is involved. Having said that the change in policies and the restriction of inorganic fertilisers and dangerous chemicals has definitely improved farming practise and reduced harm to the environment whilst continuing an upward direction of yields. Most farmers become comfortable with the practises they have become used to and probably inherited from their parents, however once forced in to an unfamiliar method they find a way of working with it to maintain productivity. In my experience it is price control that generally produces the most environmentally detrimental effect. Ie subsidies for wheat/milk/linseed/smallfarms etc these invariably skew balanced agricultural production and pure ‘chasing the bottom line’ causes environment and good agricultural practise to become secondary to profit

  28. As inorganic fertiliser increases humus and organic matter reduce as the urea exploit the organic matter. No till farming can change that slowly bt surely but it takes a lot of courage to let the weeds grow and only spray at flower stage. It works in Australia because most rain events are very small, so that the weeds can be sprayed after rain.
    While the above ground part of the plant is important for mulching purposes, it is the roots that cause the most beneficial improvement. As they die, they leave air pockets in the soil for water penetration and as they then decompose, they release organic matter to feed the soil microbes.
    Humus itself is mostly useful for creating air pockets to let rain soak in and for the layer of air underneath it that reduces evaporation and keeps a fairly even temperature. Basically, humus is a blanket for soil microbes and insects to be protected as they go about their business.
    As inorganic fertilisers are applied, the soil and fertility microbes are reduced. Try putting your hand in a mix of urea and water and you will see why.
    As humus increases, then more water is absorbed by percolation into the soil. A benefit is that run-off into streams should then be better filtered.
    Climate change has nothing to do with it.
    In fact the warmer the better. I know nothing about snow country.

  29. Before we humans began organizing information and using scientific method to explore cause-effect relationships, we used to blame everything bad on evil spirits, or witches and such. Now everything bad that happens is a result of the anthropomorphic component of any change—in climate. It seems we’ve gone backwards.

  30. Having escaped from the socialist utopia of the eu I would say the ban on spreading the contents of septic tanks, the ban on burning stubble and such like is the greater factor remember this is the brilliant irgabisation that banned straight bananas, banned mri machines and forces fishermen to dump tones of the wrong fish ( now dead)every trip

  31. Yet Phoenix Arizona and Texas have increasing yields and great soils… Hint: It is not 1 C that is the cause of any problem. I would check for stupid government regulations…
    In my youth, Dad, from Iowa, showed me how to build up humus in soils. This was in California in a seasonal desert with 3 months of summer often called out as “110 F in the shade, and there aint no shade.” IIRC, thats well over 40 C, so unless Europe has suddenly gotten hotter than Phoenix Arizona, it is not the heat.

    • E.M.Smith
      August 28, 2015 at 10:41 pm
      , it is not the heat.

      It’s the humidity. 😎
      A year or two of bad weather does not a “Climate” make.
      (Especially when it wasn’t as bad as you were told it was.)

  32. Weismeier and friends work out the reasons for the stagnation in crop yield then ignores them and says it’s climate change
    There are none so blind as those who will not see.

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