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Soil Organic Matter - Page 2
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  1. Default

    One article on microbes in soils, and the changes that might occur with warming.


  2. Default

    I found this more official view on carbon storage in soils relating to dairy farming, and while it's not so positive, it does give some confirmation on the science that needs to be used.


    A dairy farm is not greenhouse gas neutral
    The query “If cows eat pasture and recycle the carbon, why isn’t a dairy farm carbon neutral?” is
    often asked. A corollary question is “Why isn’t the carbon stored in pasture counted as a benefit
    to offsetting greenhouse gas emissions by farmers?” David Whitehead, Adrian Walcroft,
    Surinder Saggar and Warren Parker at Landcare Research address these issues in this article.

    Increasing concentrations of greenhouse gases in the atmosphere are related to global warming.
    The three most important greenhouse gases are carbon dioxide (mainly from burning fossil fuels
    and deforestation), methane (mainly from ruminant animals and waste management) and
    nitrous oxide (mainly from dung, urine and nitrogenous fertilisers). In contrast to most
    industrialised nations, 50% of New Zealand’s greenhouse gas emissions are attributable to
    methane and nitrous oxide, predominantly from agriculture. While the atmospheric
    concentrations of nitrous oxide (320 parts per billion) and methane (1.8 parts per million) are
    low compared with carbon dioxide (383 parts per million), on a mass basis their contributions to
    global warming, signified as ‘global warming potential’ (GWP) are much higher. Calculations
    show that over a 100 year time period, 1 kg of emitted nitrous oxide has the same greenhouse
    effect as 310 kg of carbon dioxide, while 1 kg of methane has the same greenhouse effect as
    21 kg of carbon dioxide.

    It is certainly true that carbon cycles through pastoral systems, and that farming ruminant
    animals does not add any ‘new’ carbon to the atmosphere. However, in the process of milk
    production some of the carbon in the atmosphere is transformed from a gas with a lower GWP
    (carbon dioxide) to a gas with a higher GWP (methane). For methane, the warming effect is
    much greater in the short term (over 20 years the GWP for methane is 72) and declines over
    time as the methane is converted back to carbon dioxide by natural processes in the
    atmosphere (about half the emitted methane is converted to carbon dioxide every 8 to 10

    Some dairy farmers believe that by increasing pasture production, this will lead to more carbon
    stored in the soil and that they may earn carbon credits or offset methane and nitrous oxide
    emissions. Is this possible?
    To answer this we need to consider how carbon is cycled and stored
    in pasture systems, how increased production will affect the carbon cycle, and also account for
    emissions of all three greenhouse gases.

    The average stocking rate for dairy herds in New Zealand is 2.8 cows per hectare. Carbon dioxide
    captured in the pasture biomass undergoes a series of cycles and overall, very little of this
    carbon is retained in the system. A hectare of pasture producing about 15,000 kg of dry matter
    per year above‐ground will also transfer an equal amount of carbon to root growth. So, in total,
    pasture growth will remove about 50,000 kg of carbon dioxide from the atmosphere annually
    (dry matter is 45% carbon and carbon dioxide is 27% carbon by weight). Almost all the carbon
    transferred below ground is gradually returned to the atmosphere as carbon dioxide as the
    roots respire and decompose. About 85% of the above‐ground pasture is consumed by the cows
    and the remaining 15% is left at the site as plant litter that rapidly decomposes, releasing the
    carbon back to the atmosphere as carbon dioxide. Over half (55%) of the pasture consumed by
    cows is breathed back to the atmosphere as carbon dioxide and about 30% is returned to the
    paddock as dung and urine that rapidly decomposes to carbon dioxide. About 12% of the
    pasture eaten by the cows leaves the paddock as meat and milk and about 3% of the pasture
    ingested is released as methane.

    If pasture productivity was increased by 3000 kg dry matter per hectare per year by adding
    nitrogen as fertiliser, this would remove an extra 10,000 kg of carbon dioxide from the
    atmosphere per hectare per year.
    However, an extra half a cow per hectare would be grazed to
    utilize the extra feed. This would increase the rate of carbon cycling in the system (more cow
    respiration, more dung deposition, greater product removal and increased methane emissions
    per hectare), but have very little effect on carbon stored in the system. Increasing fertility can
    reduce root growth as the plants do not need to explore as much soil volume to obtain the
    required nutrients.
    Increased fertility also increases the decomposition of soil organic matter,
    returning carbon dioxide from the soil to the atmosphere at a faster rate. Recent data have
    shown that increases in dairy farming intensity have reduced soil organic carbon levels at some
    By international standards, New Zealand intensive pastoral soils have high soil organic
    matter levels because of the relatively recent conversion from native forest to permanent
    Only a small area of land is under continuous cropping which depletes soil carbon.

    The potential for significant, permanent increases in soil organic matter in intensive pasture systems
    is therefore limited.

    Emissions of methane and nitrous oxide must be considered in addition to the cycling of carbon
    dioxide. Ruminant digestion by a dairy cow produces about 80 kg methane per year or 220 kg
    per hectare. This is a small amount but, when multiplied by the GWP for methane, is equivalent
    to 4600 kg carbon dioxide emitted per hectare per year. Furthermore, a cow excretes about
    120 kg of nitrogen per year in dung and urine. A very small proportion of this (about 1%) is
    converted to nitrous oxide, amounting to about 5 kg per hectare per year, but this emission is
    equivalent to 1600 kg of carbon dioxide per hectare per year because nitrous oxide is an
    extremely potent greenhouse gas. As an indication in terms of costs, at $25 per tonne for
    carbon dioxide these emissions amount to a potential liability of about $160 per hectare per
    year. However, this is likely to change by 2013 when liabilities for agricultural emissions start to
    take effect in the present Emissions Trading Scheme.

    To offset these emissions by an increase in soil organic matter would require the soil to absorb
    and permanently store 6200 kg of carbon dioxide per hectare per year.

    This is over half of the extra carbon dioxide removed by the
    potential increase in pasture productivity following fertiliser application, without considering
    that most of the carbon dioxide will be recycled back to the atmosphere anyway. Clearly, it is
    not possible to offset methane and nitrous oxide emissions by increasing pasture productivity.
    Even if an increase in pasture productivity resulted in a permanent and measurable increase in
    carbon storage, under the current set of rules in the Kyoto Protocol that New Zealand adopted,
    this would not be eligible for credits.
    Carbon credits to offset emissions can only be recognised if
    a land‐use change after 1990 results in a measurable and verifiable increase in carbon storage,
    such as afforestation of land that was previously in pasture. Storage of carbon in soils and
    vegetation that does not meet particular criteria cannot be counted for allocation of carbon
    credits. [B]These criteria could be changed in future negotiations, but they stand at present.[/B

    In summary, carbon moves into and out of the farming system in a continuous cycle with little or
    no new carbon added to or removed from the atmosphere by grazed pastures (we have not
    considered carbon dioxide emissions from transport, energy use, waste management or other
    on‐farm activities in this article). Dairy farms contribute to greenhouse gas emissions because of
    nitrous oxide and methane emissions. Further, it is not possible to offset these emissions by
    improving pasture productivity because the extra carbon gain will be balanced by increased
    carbon loss, resulting in no observable change in net soil carbon storage. Dairy farming provides
    many economic benefits but also contributes substantially to New Zealand’s greenhouse gas
    liabilities. Modifying farm management practices to minimise gaseous nitrogen losses, e.g., the
    use of stand‐off pads or herd homes during wet periods in winter, and storage of carbon in
    regenerating shrubland or planted forests are the most promising ways to reduce farm
    greenhouse gas emissions at present. Investment in research to develop cost‐effective ways to
    reduce methane and nitrous oxide emissions is a high priority for the dairy industry.

    Contact for further details:
    David Whitehead, Landcare Research, PO Box 40, Lincoln 7640
    Tel: 03 321 9862 Email: whiteheadD@landcareresearch.co.nz
    © Landcare Research, 2009. Article prepared for DairyNZ.
    There is one common theme in many articles written by scientists: we urgently need more research done (read: more funding please).

    There are a few holes in the arguments above, for example most NZ cows are underfed for most of the year relative to their biological capability, and so in a pure grass-based system as discussed, the number of cows per hectare could be held or lowered if more good quality pasture was available.

    I still think that in many NZ soils, the water-holding ability is limited by lower than average SOM, and hence production is limited. Rolling and alluvial country would be cases in point. In my maths further up the thread I just looked at pastoral soils bringing our net emissions to zero, so the numbers were less. But I was in the ball-park.

  3. Default Methane research short-circuited

    Now I know that there have been some major research funds going into methane reduction from ruminants in NZ. I wonder if this article is worrying some scientists.

    Alexander Hristov, Penn State: Oregano suppresses methane cow belches

    September 13, 2010

    Cow belches, a major source of greenhouse gases, could be decreased by an unusual feed supplement developed by a Penn State dairy scientist.

    In a series of laboratory experiments and a live animal test, an oregano-based supplement not only decreased methane emissions in dairy cows by 40 percent, but also improved milk production, according to Alexander Hristov, an associate professor of dairy nutrition.

    The natural methane-reduction supplement could lead to a cleaner environment and more productive dairy operations.

    "Cattle are actually a major producer of methane gas and methane is a significant greenhouse gas," Hristov said. "In fact, worldwide, livestock emits 37 percent of anthropogenic methane."

    Anthropegenic methane is methane produced by human activities, such as agriculture.

    Compared to carbon dioxide, methane has 23 times the potential to create global warming, Hristov said. The Environmental Protection Agency bases the global warming potential of methane on the gas's absorption of infrared radiation, the spectral location of its absorbing wavelengths and the length of time methane remains in the atmosphere.

    Methane production is a natural part of the digestive process of cows and other ruminants, such as bison, sheep and goats. When the cow digests food, bacteria in the rumen, the largest of the four-chambered stomach, break the material down intro nutrients in a fermentation process. Two of the byproducts of this fermentation are carbon dioxide and methane.

    "Any cut in the methane emissions would be beneficial," Hristov said.

    Experiments revealed another benefit of the gas-reducing supplement. It increased daily milk production by nearly three pounds of milk for each cow during the trials. The researcher anticipated the higher milk productivity from the herd.

    "Since methane production is an energy loss for the animal, this isnít really a surprise," Hristov said. "If you decrease energy loss, the cows can use that energy for other processes, such as making milk."

    Hristov said that finding a natural solution for methane reduction in cattle has taken him approximately six years. Natural methane reduction measures are preferable to current treatments, such as feed antibiotics.

    Hristov first screened hundreds of essential oils, plants and various compounds in the laboratory before arriving at oregano as a possible solution. During the experiments, oregano consistently reduced methane without demonstrating any negative effects.

    Following the laboratory experiments, Hristov conducted an experiment to study the effects of oregano on lactating cows at Penn State's dairy barns. He is currently conducting follow-up animal trials to verify the early findings and to further isolate specific compounds involved in the suppression of methane.

    Hristov said that some compounds that are found in oregano, including carvacrol, geraniol and thymol, seem to play a more significant role in methane suppression. Identifying the active compounds is important because pure compounds are easier to produce commercially and more economical for farmers to use.

    "If the follow-up trials are successful, we will keep trying to identify the active compounds in oregano to produce purer products," said Hristov.

    Hristov has filed a provisional patent for this work.
    40% is a massive decrease. We're not told under what conditions this result occurred, but maybe a start would be to have herbs including oregano interspersed in pasture. Does this sound like biological farming? Yes.

  4. Default

    Here's a page from the FAO on soil organic matter:http://www.fao.org/docrep/009/a0100e/a0100e02.htm

    It mentions soil water retention being improved by more SOM. A lack of rain during periods of the year is the major limitation in grass growth of NZ pastures. Too hot, no moisture left, and the grass virtually dies. Not much of a crop at that stage. It has been shown by scientists that the theoretical maximum tonnage from a ryegrass/clover mix is about 20-25tonne DM/Ha/year. Nearby Ruakura grows about 16tonne, many farms in the North Island obtain about 11-16 tonne (no extra Nitrogen or irrigation). Pioneer state that it's possible to grow a maize crop and follow it with the winter crop, to grow 38tonne DM/Ha/year. Fairly intensive of course, but this is well over twice the output from a well-managed dairy farm.

    If you were to obtain 25tonne DM/Ha/year from clover/ryegrass, you'd need 68kgDM production average on each day of the year (6.85grams per square metre). Waikato paddocks can grow over 110kg/Ha on a good day. But not every day.

    Getting back to water retention: loamy sand holds about 1/4 of the water that silt loam holds. We can't easily fix temperature extremes outdoors, but over time we should be looking to improve soil moisture retention. Biological farming, anyone?

  5. Default

    A wider mix of species in the paddock will help with SOM, because there will be longer and higher volume root structures, in theory. DairyNZ is working on this area indirectly, across the road from our workshop, on Scott and Lye Farms. One of the interesting results was to do with potential nitrogen leaching reductions.


    These paddocks included some Lucerne, which in turn helped the ryegrass get through the drought in better condition. The cows ate less in general on the mixed forage, but produced more milksolids. All data was compared with the control of a standard ryegrass/clover mix.

    Australia's DairyNews has more insight into the trial. About a one-third reduction in nitrogen in urine from the cows fed mixed pasture was observed. The next set of work will try to figure out which of the pasture species helped in this area the most. Overall farm production on such a system might not be a lot higher, although animal health costs might drop (not mentioned by the researchers) and the mixed pasture is more drought tolerant, even three years after establishment.

    Wednesday, 22 May 2013 04:01
    Mixed pasture trials boost milk solids

    A THREE-YEAR experiment with mixed pastures could have big implications for future management of environmental impacts.

    Results showed cows in the trials fed on mixed pasture excrete half the amount of nitrogen (N) in their urine compared to cows on standard pasture, the recent DairyNZ Farmers Forum in Whangarei heard from senior scientist Sharon Woodward.

    Milk solids production was also boosted 15-20% in late summer and autumn when cows grazed mixed pastures.

    “The big thing for the future is that feeding mixed pastures has had a major impact on reducing urinary N losses from the cows,” Mrs Woodward said. “This has implications for greenhouse gas emissions and nitrate leaching.”

    In the experiment both the standard and mixed pastures were sown with perennial ryegrass and white clover. The mixed pastures were also sown with prairie grass, lucerne, chicory and plantain.

    All pastures were set up three years ago on the Scott Research Farm in Hamilton, NZ and all received the same treatment for maintenance fertiliser, urea application, grazing and cutting for silage.

    Mrs Woodward says over the three years the total cumulative dry matter yields were the same for both pasture types. In the summer/autumn there were advantages in feed availability from the mixed pastures, but these were lost in winter.

    Indoor and outdoor trials were used to assess milk production and nitrogen partitioning. “When you feed cows indoors in metabolism stalls you can measure the intake of each cow and also collect all the urine and faeces,” Mrs Woodward says.

    “The cows were fed either mixed or standard pasture. The cows on the mixed pasture ate less but they did produce more milk, and of course that meant more milk solids, not only because of the increase in volume but because we didn’t get a change in the milk fat concentration, but we got an increase in the milk protein concentration.

    “But the key reason for using the metabolism stalls was to look at nitrogen partitioning within the cow. This was important from an environmental perspective because we get a feeling of what’s happening in terms of greenhouse gas – that’s your nitrous oxide and ammonia emissions and what’s going to happen in terms of nitrate leaching.”

    Cows on the mixed pasture partitioned about 23% of their daily nitrogen intake into the milk, about 39% went into the faeces and 29% went into the urine. Cows on standard diets put a lot less nitrogen (15%) into the milk and much more (43%) into their urine. “And it’s that urine that’s a big problem from an environmental perspective.

    “The key point here was the cows fed the mixed diet were excreting only half the amount of nitrogen in the urine than the cows on the standard diet.”

    In her summing up Mrs Woodward said the biggest finding of the study was that feeding mixed pastures had a major impact on reducing urinary N losses. This was achieved with no loss of milk production and a 15-20% boost in late summer/autumn. She asked farmers to consider what putting a portion of their farm into mixed pasture might mean for their profitability and their ability to reduce nitrogen losses on-farm.

    The work was funded by DairyNZ and the Ministry of Business, Innovation and Employment.

    Mrs Woodward later said an application had been made for funding for a much bigger programme of work over the next six years investigating use of various forage species to reduce nitrate leaching. If successful, one aspect will be more indoor work controlling the composition of mixed diet to try to pinpoint which species might have the major effects on production and reducing N loss.

    They would also look at the on-farm situation – in the trials so far cows were fed a 100% mixed diet but it was unlikely on-farm that all paddocks would be sown in mixed pasture, which also takes a few years to get established.

    So mixed pastures were not the “silver bullet” to reduce nitrogen leaching, but increasing pasture species diversity could certainly provide part of the solution, she believes.

  6. Default

    This research (above) was also covered in the Farming pages of the Waikato Times this week.

  7. Default

    A very interesting article from the Element Magazine, inside the NZ Herald this week.


    One excerpt:

    Mineral balance, inexpensive microbial inoculums and compost are three keys to improving profitability, plant resilience, stock health and our health.
The microbe most missing in most soils around the world is actually the most important creature of them all at this point in time.

    Mycorrhizal fungi burrow into the plant roots and then create a massive root extension that effectively provides ten times more root surface area. These symbiotic fungi allow the plant greater access to key minerals like phosphorus, potassium and calcium and they produce immune supporting bio-chemicals for their host. They also produce a sticky substance called glomalin that is now known to be the triggering mechanism for 30% of the humus in the soil.

    Extractive agriculture has done more than increase our likelihood of growing substandard, chemically contaminated food, it has also knocked out 90% of the all-important mycorrhizal fungi in our soils. These creatures can be reintroduced for as little as ten dollars per hectare and we need to initiate this repopulation exercise, yesterday.

  8. Default

    Roger Martyn from GrazeTech in Australia sent me this fascinating video today. Cell grazing, holistic grazing, and the basic thought processes behind it, could literally help save the planet. Allan Savory has been working in this area since the 60s.


  9. Default

    I'm working on preparing a test plot in the paddock beside our workplace. It's only 5m x5m, but is taking a while to dig over by hand. I am not going to use herbicide to kill off the existing grasses and weeds, because I want to encourage worms and fungi etc, and I don't want to increase any local toxicity. This article on glyphosate is interesting.


    All around the Waikato at the moment, some paddocks are being sprayed off to the tell-tale brown colour, ready for new tilled grass seed. What if Prof Don Huber is right, and the glyphosate sticks around to semi-damage the new grasses in future? And what about the newly discovered pathogen associated with glyphosate-ready crops?

  10. Default

    The plot has been prepared for the fert application, with half of the 5mtr x 5mtr space having the sods and contained worms and topsoil overturned on top of the subsoil layer, with remaining topsoil placed on top. The other half had the topsoil removed to the subsoil layer, two bales of hay and 10x 40litre bags of compost placed on top of the subsoil, then the overturned sods and topsoil as before.

    We have picked up some of the fertilizer from farm and garden supply stores, and today the difficult small quantity trace minerals like Borate and Selenium from Ballance in Morrinsville. Many thanks for that - they were very obliging.

    As far as the original plot is concerned, this was in generally a poor part of the paddock, and it's low in a few trace elements, the pH is low, there are not many worms per spadeful (about 1 perhaps) and the topsoil is compacted, but still friable when pushed. The topsoil layer appears to differ in depth from about 70mm to 300mm, and the subsoil is pumice ash, very light and free draining in nature.

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