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Can stockless organic systems really be sustainable?

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  • Richard Morris
    A very interesting article on stockless (i.e vegan) systems. Found on the veganorganic mailing list http://groups.yahoo.com/group/veganorganic/ the mailing
    Message 1 of 1 , Jun 6, 2004
      A very interesting article on stockless (i.e vegan)

      Found on the veganorganic mailing list
      the mailing list of the Vegan Organic Trust
      who are one of the main voices for vegan organic growing.

      Can stockless organic systems really be sustainable?

      Miles Gibson

      Organic Farming Diploma
      Scottish Agriculture College
      Year 1

      Soils and Nutrient Cycling


      The Bruntland report (WCED 1987) defined sustainable practice as that
      which 'meets the needs and aspirations of the present without
      compromising the ability of future generations to meet their own needs'.
      This is a commonly used but very broad definition that can encompass
      environmental, social and economic factors on anything from an
      individual farm-scale level to a global one. It leaves a great deal of
      room for debate and speculation, for example how to weigh the economic
      aspirations of a developing country against long term environmental well
      being. It is not suprising that Rigby and Woodhouse (2001) report that
      there is no consensus on sustainability's 'precise or operational
      meaning'. For the purposes of this essay therefore I will now briefly
      outline the elements of sustainability that I will be focusing on
      without any claim to be comprehensively covering every aspect and nuance
      of this multifaceted concept.

      In this essay I will be focusing on soil health, particularly nutrient
      budgeting; on what is practically sustainable which generally comes down
      to economics; and more briefly on environmental and social issues on a
      local and global level. All these aspects of sustainability are
      interconnected but for the sake of structure I will attempt to deal with
      them separately. My main concern is for what is operationally possible
      and organically principled on a farm scale level in this country. Which
      is also the arena in which I think it is possible to talk with the least
      speculation. The discussion will involve some comparison with livestock
      and mixed systems but the predominant focus will be upon the viability
      of stockless systems.

      Setting the scene

      For founders of the organic movement such as Lady Eve Balfour livestock
      were an integral part of any sustainable organic system. Without their
      manures a vital part of the nutrient cycle would be lost. To this day
      the majority of organic farming in UK is on mixed or livestock units in
      central and western areas, mixed units being closest to the original
      self-sufficient ideal. On mixed farms the grass-clover ley is expected
      to accumulate sufficient nitrogen for subsequent arable crops, while
      also supporting animal production. Grass clover leys typically occupy at
      least 50% of the mixed farm and the manure generated can be used to move
      nutrients around the farm within the rotation (Philipps, L 2001). The
      amount of ley required in such a rotation presents a challenge to
      stockless organic systems and indeed in arable eastern areas of the UK
      conversion to organic has been far less prevalent. Some stockless
      systems however have been developed using a one year nitrogen fixing
      green manure crop designated as set-aside within the rotation (Watson et
      al 2000). There are also a few pioneers such as the Vegan Organic Trust
      and Iain Tolhurst who maintain that through the careful management of
      rotations and green manures a closed system is achievable that scores
      more highly in terms of sustainability than any of the alternative

      Soil health and nutrient budgeting

      Achieving a balance between inputs and outputs of nutrients in a farming
      system is vital both for short-term productivity and long term
      sustainability (Watson et al 2000). In stockless farming green manures
      are at the heart of nutrient cycling. They take nitrogen (N) from the
      air and via soil bacteria recycle it so that it can be used as a source
      of fertility. The sustainability of this process has been a key focus of
      the research into stockless farming that has been carried out.

      In 1987 the Elm farm research centre (EFRC) established a stockless
      trial which ran until 1998. They compared 3 different 4 year rotations
      all of which used a one year red clover manure for fertility building
      (Philipps, L 2001). Rock phosphate was also applied to the maximum rate
      allowed by Soil Association during the green manure phase of the
      rotation. The red clover green manures accumulated approximately 300kg
      N/ha above ground which was considered enough to support the estimated
      nitrogen offtake. An N deficit recorded on a similar stockless trial
      conducted by ADAS at the Terrington Research Farm in Norfolk was
      attributed to poor germination and establishment of the red clover, and
      not an inherent failing in the system. The timing of incorporation and
      the N demand of subsequent crops is also considered critical to minimise
      N losses (Watson et al 2000)

      In the EFRC trial Phosphorous (P) needs were met by the rock phosphate,
      and levels of Potassium (K) were not affected. This led to the
      conclusion that soils with a clay content greater than 20% seem to be
      able to derive sufficient K from mineralization to sustain crop yields,
      although it was acknowledged that more research on sustainability for
      different soil types was needed. At Terrington although K was in
      deficit, there was no measurable change in available K or P. This may be
      because the less intensive nature of production mean lower soil P and K
      are acceptable (Fortune et al 2001)

      A potential problem was the significant decline that was observed in
      levels of Soil Organic Matter (SOM) by EFRC, particularly in the first 4
      years, although this may be explained by the change from grass to arable
      production. Any conventional system would also be likely to experience a
      similar drop in such circumstances. It should also be noted that changes
      in setaside regulations have allowed organic farmers to use setaside as
      a means of fertility building for up to 2 years, as opposed to the 1
      used in these trials this inevitably benefits SOM levels.

      On the subject of SOM and green manures it is worth mentioning recent
      work done at the Rodale institute (Drinkwater et al 1998) which showed
      that the rate of accumulation of SOM when farmyard manure was used as
      fertiliser was double that of when leguminous green manures was used.
      This seems to point to an advantage that livestock or mixed systems have
      but more research needs to be done on the relationship between organic
      matter content of the soil and soil structure and crop yields to really
      prove this.

      A slightly different approach to balancing the nutrient budget and
      maintaining soil health has been adopted by Iain Tolhurst in his
      stockless field vegetable and market garden enterprise in south
      Oxfordshire. He points to the importance of his rotations and operates
      far longer ones, 7 years for field vegetables and 9 years in his market
      garden. Regular soil analysis has shown steadily improving fertility
      particularly phosphate and potash due to the deep-rooting foraging of
      the legumes. The soil fauna has improved as has health of the more than
      70 crops grown. (Tolhurst 2004). Tolhurst is a powerful advocate of
      under sown green manure (ugm) as a way of reducing time needed in the
      fertility-building phase. Ugm will not only add nitrogen and organic
      matter to the soil but even more importantly according to Tolhurst
      (2003) it ensures the soil is covered prior to the winter period when
      the loss of nutrients to leaching is even greater than the nutrient loss
      in crop off-take. The vital emphasis is on making sure that the more
      modest level of inputs is balanced by reducing outputs. Deep rooting
      green manure also helps to recycle nutrients that may have been lost to
      lower soil levels during previous cropping.

      In terms of general soil health deep rooting of green manures also
      improves soil structure. Their cover also benefits earthworm and soil
      fauna populations. Tolhurst does stress however that the Ugm should not
      be seen as way of eliminating the need for a fertility break in the
      rotation as a resting period when the soil is not being cultivated at
      all is the best possible condition for earthworms to flourish.

      Economic and Management considerations

      EFRC stockless trials reported that over an 11 year period yields have
      been maintained, there have been insignificant disease levels and due to
      clover allowance for organic fields in setaside, there has been a
      healthy financial return. A critical factor in determining yield has
      been crop establishment. Similarly the ADAS research recorded impressive
      potato and cereal yields with good price premiums and lower variable
      costs giving favourable gross margins. This held true when projected to
      a national farm size and allowance was made for the Set Aside and Arable
      Area Payments, although it was noted that price premiums for organic
      produce cannot always be relied on (Watson et al 2000). This projection
      is also open to question on lighter soils where organic cereal yield is
      less impressive (Cormack 1999). Although the already mentioned new set
      aside regulations that make a 2 year ley viable would boost fertility
      and therefore yield.

      The issue of ratio of fertility building to cash crop may also be
      addressed by careful planning of rotations and under sown green manures
      as has been done by Iain Tolhurst. He currently has cash crops at a
      level of 70% while maintaining fertility levels and is running an
      economically viable operation (Tolhurst 2004). Although he is aware with
      some crops ugm may compete for nutrient and moisture with the main crop.
      He believes it is acceptable to take a lower yield in order to build
      adequate fertility for future cropping (Tolhurst 2003). He also points
      to the greater costs involved in keeping livestock and claims that at a
      small farm scale it is mixed and livestock systems that are not
      economically viable.

      The management issues in stockless systems centre mainly on weeds and
      pests. The EFRC trial reported no sign of weeds, pests and disease
      increase (Bulson 1996) and noted that some crop sequences were
      particularly effective in suppressing weeds. A build up of perennial
      weeds was reported in the ADAS and CWS trials (Leake 1999) however.

      Iain Tolhurst sees as vital the timely establishment of ugm to smother
      weeds, although concedes that a high degree of management is required as
      there is only a narrow window of opportunity for pre-sowing weed control
      and subsequent sowing of green manure (Tolhurst 2003) He also points to
      the benefits of green cover between rows that can confuse some pests
      while also attracting beneficial insects, although he does stress the
      need to chose crops carefully in order to avoid slug problems. Jean Paul
      Cortens (Cortens 2004) of Roxbury farm adds to the debate by describing
      how insects will migrate to cash crops when cover crops are cut and many
      diseases and pests like aphids increase when too much raw fertility is
      applied. His suggested solution is to never mow all cover crops at once,
      and to have another crop available for insects to migrate to.

      Environmental and social considerations

      On a global level there have been substantial losses in SOM during the
      last 100 years, this is associated with changing patterns of land use
      driven by population increase (Rees R 2001). There has never been a
      greater pressure on the world's ecosystems to provide for human needs,
      and there are many who believe that the answer to this challenge is to
      be found in a significant reduction in livestock farming and an increase
      in stockless systems. Currently the combined weight of cattle in the
      world exceeds that of human beings to support this ΒΌ of earth's surface
      is used as livestock pasture. The destruction of Brazilian rainforest
      has been driven by the desire to grow soya for animal feed (Sams2003).
      It has also been estimated that the only way Europe could feed itself
      organically would be for the proportion of grain legumes grown to be
      increased at the expense of livestock production (Stockdale, E et al
      2000). European livestock farming currently relies on feed grown in
      developing countries which ties up resources that could be used to meet
      their own domestic food needs. It is highly questionable whether this is
      a sustainable way of feeding the world's population.

      This imbalance also exists domestically, where more than 65% of cereal
      crops in England go to feed animals on top of the huge additional
      quantity imported from all over world. Despite the organic ideal of a
      closed system all livestock systems and the vast majority of mixed
      systems buy in feed or bedding from elsewhere thereby depriving somebody
      else of their fertility. This compares unfavourably in terms of
      sustainability with stockless systems such as Iain Tolhurst's vegetable
      farm that operates a self-sufficient nutrient budget. There are also
      many more environmental and social dangers such as pollution and
      zoonotic diseases from using farm yard manure and slurry as fertiliser
      than green manures.

      Concluding remarks

      Although stockless organic farming remains relatively untried and
      unresearched in this country, what has been done so far looks
      favourable. Alastair Leake of C.W.S Agriculture in a review of stockless
      experiments at EFRC, ADAS and CWS concluded "all arable organic farming
      is economically viable and technically feasible" (2001). There are also
      pioneering techniques being developed through practice by the likes of
      Iain Tolhurst with his long rotations, use of ugm and balancing of the
      nutrient budget by compensating for less input by ensuring there are
      less losses. It seems that these ideas are generating momentum in the UK
      with the Vegan Organic Trust set to launch the first ever stock free
      standards under the wing of the Soil Association. On a global scale it
      is hard to disagree with those who argue that a significant increase in
      stockless systems would be the most economical, sustainable and least
      harmful use of the Earth's increasingly pressured food producing
      resources. Evidence also suggests that the less meat rich diet this
      would entail might even see us all sustained in good health a little
      longer with lower risk of heart disease, obesity and cancer!


      Bulson H (1996) Is there life without livestock? New Farmer and Grower,
      Winter 1996.

      Cormack W (1999) Testing a stockless arable rotation on a fertile soil.
      In Designing and Testing crop rotations for Organic Farming pp 115-123.
      Eds Olesen J et al. DARCOF Report No 1

      Cortens J (2004) Fertility a management at Roxbury Farm. A case study.
      SAC Blackboard

      Drinkwater L et al (1998) Legume-based cropping systems have reduced
      carbon and nitrogen losses. Nature, vol. 396, 19 Nov. 1998

      Fortune, S et al (2001) N, P, K Budgets for some UK Organic Farming
      Systems Implications for Stability. In Soil Organic Matter and
      Sustainability pp 286-293. CABI Wallingford

      Leake A (1999) A report of the results of CWS Agriculture's organic
      farming experiments 1989-1996. J. Roy. Agric. Soc. Eng, vol. 160, 1999

      Leake A (2001) Performance of arable organic farming: a UK experience.

      Philipps, L (2001) The Effects of All-arable Organic Rotations on Soil
      Organic Matter Levels and the Phosphorous and Potassium status over the
      Period 1987-1998. In Sustainable Management of Soil Organic Matter. CABI

      Tolhurst I (2004) Vegetable Farm. Organic Gardening January 2004

      Tolhurst I (2003) Under Sowing Green Manures in Vegetable Crops. VON

      Rees R Ed (2001) Sustainable Management of Soil Organic Matter. CABI

      Rigby D and Woodhouse P (2001) Constructing a farm level indicator of
      sustainable agricultural practice. Ecological Economics 2001, Vol 39, No
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      Sams C (2003) The Little Food Book. Alastair Sawday Publishing

      Watson C et al (2000) Agronomic and Environmental implications of
      stocked and stockless organic rotations. Aspects of Applied Biology 62,

      WCED (1987) The Bruntland Report. Our Common Future. OUP

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