Humus depletion induced by climate change?
Stagnating crop yields pose a threat to soil
From the TECHNICAL UNIVERSITY OF MUNICH (TUM)
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.”
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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 http://www.sciencedirect.com/science/article/pii/S0048969715304071
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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.
http://www.usask.ca/agriculture/plantsci/winter_cereals/winter-wheat-production-manual/chapter-10.php
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
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/364157/structure-jun2013prov-UK-16oct14.pdf
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
http://www.fwi.co.uk/arable/photos-world-record-wheat-yield-harvest.htm
Turning to Germany and using more valid statistics we find that wheat yields are up by 19% from 1985
http://www.bmel.de/SharedDocs/Downloads/EN/Publications/GermanAgriculture.pdf?__blob=publicationFile
And this in spite of a long term cooling trend – the increased temperature in 2014 was accompanied by increased yields of cereals.
http://notrickszone.com/2015/04/29/german-dwd-weather-services-own-data-contradict-its-alarmist-claims-of-uninterrupted-warming/
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:
http://ec.europa.eu/agriculture/ricaprod/pdf/cereal_report_2012.pdf
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.
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.
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.
Mann made, of course.
If your Auntie had testicles she would be your Uncle.
Or Brucette Jenner?
(Wait a minute. Never mind.)
“‘Balls!’ said the queen, ‘if I had to, I’d be king.'”
Schweinerei.
This is research?
Climate Destruction is degrading Northern Europe’s sense of humus.
Ouch!
Global Warming is a cereal killer.
We are on a pathway to Total destruction.
Can we expect a Cap’n crunch?
Fed back by Froot loops?
Will we lose our Lucky Charms?
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
http://2.bp.blogspot.com/-nicWiURng5o/UoBu3RaPdII/AAAAAAAAAvM/9vGueBMz2ss/s1600/WIZARD+OF+ID+YIELD+FC.jpg
Breakfast will be toast.
Erosion of Familia values.
Our children won’t know what Mike’s Nature Trix is.
Protego delenda est!
As the Wheat thins.
And the Rice crisps.
And the Corn flakes.
Gaudeamus igitur,
Juvenes dum sumus;
Post jucundam juventutem,
Post molestam senectutem
Nos habebit humus.
[New Yorker, 2/14/53]
Humus is especially good with pita bread.
Which is a cereal, after all.
Perhaps overlooked by all those cereal murderers.
More’s the pita. More’s the pain. “For though it rises in the yeast, it should be better bred.”
You. my brother, are incorrigible. Or something equally Latinate.
Vini veni vidi vici.
When you’re on a roll, you’re on a roll.
Until it stales.
Just a glutin for punnishment.
Very punny!
Some breakfast rolls are nutty.
(I hope that comment didn’t get you frosted.)
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.
But does peer review separate the wheat from the chaff?
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
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.
If you bake your bread you must lie in it.
Munich (TUM) evaluated the crop yield statistics for EU countries
Munchen bein’ Universal.