In millions of years huge amounts of organic matter were stored in the soil as organic matter or fossil energy carriers as oil, gas and coal. We make use of these stocks to supply us with energy and to be able to grow plants for our needs. However what has been stored in our soils for millions of years we now are depleting in a few hundred years. The amount of organic matter we return back to the soil is in general too low to maintain its capacity for plant production on the long term. Various studies show there is a decrease of organic matter in arable soils all over the world

Sukkel, W.

English

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Organic and conservation agriculture, the best of both worlds?

Wageningen Yield 

The 5th International Scientific Conference on Sustainable Farming Systems                  E C O M I T  
 
 
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ORGANIC AND CONSERVATION AGRICULTURE, THE BEST OF BOTH 
WORLDS? 
 
Wijnand Sukkel 
Wageningen University and Research Centre, Department of Applied Plant Research (PPO-agv), P.O. 
Box 430, 8200 AK Lelystad, The Netherlands. 
 
Plant use solar energy, carbondioxide, water and nutrients to make long chains of 
carbon. These carbon chains are used for the production of carbon hydrates 
proteins, fats and other organic substances. We use these for our human and animal 
food, for fibers, building materials and as an energy resource. Part of this organic 
material is returned back to the soil to make it capable of growing these same plants.  
In millions of years huge amounts of organic matter were stored in the soil as organic 
matter or fossil energy carriers as oil, gas and coal. We make use of these stocks to 
supply us with energy and to be able to grow plants for our needs. However what has 
been stored in our soils for millions of years we now are depleting in a few hundred 
years. Thus blowing the stored carbon back in the air as CO2 which is generally 
considered to be the main cause of climate change. The amount of organic matter 
we return back to the soil is in general too low to maintain its capacity for plant 
production on the long term. Various studies show there is a decrease of organic 
matter in arable soils all over the world. The depletion of organic matter in our soils 
and the way we cultivate it, is causing susceptibility to physical influences such as 
erosion and run off and is disturbing the water household.  
There are different strategies to cope with this decrease of soil organic matter. They 
come down to returning more organic matter to the soil or decreasing the speed of 
respiration of organic matter. Thus preserving soil organic matter at a level on which 
the soil can fulfill its various beneficial functions. But what level of soil organic matter 
should we strive for, considering the different functions to be fulfilled?  What is the 
minimum necessary, what is the maximum? Too high organic matter levels can also 
have adverse effects like leaching of nutrients and emissions of methane or laughing 
gas emissions. Agricultural science has until now not given very clear answers to 
these questions.  
 
Winning energy from organic substances as plant oils, wood, organic waste material 
and crop residues is considered to be partly an alternative for the use of fossil 
energy. Here the discussion arises if we should win energy from organic materials or 
we had better use them as food, fibers or building materials or use it to maintain our 
soils. The authors’ opinion is that in general we should focus on developing other 
sources of energy for our daily needs. The world will already have enough trouble to 
feed itself in the future and moreover the plant is not very efficient in storing the 
energy of the sun. We should rather use organic substances dominantly to feed us, 
to give us clothes and building materials. Only the residues that serve no other 
purpose could be used to win energy from. Agriculture should rather use its space for 
winning energy in another way. By placing windmills or solar panels on the roofs, to 
at least provide in its own energy needs. In due course also tractors could run on 
home made electricity instead of on fossil or plant derived fuels. The developments in 
storage of electricity in batteries and in electro traction are going fast. 
Should organic residues be returned back to the soil instead of winning energy from 
it? Another question on which research could try to give answers is for example what 
should we do better, compost organic residues and manure or should we turn it back 
directly to the soil or maybe first win energy from it and turn the leftovers back to the 
The 5th International Scientific Conference on Sustainable Farming Systems                  E C O M I T  
 
 
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soil? For example, compost is considered a very valuable soil improver. However 
composting is a process where organic matter partly breaks down. In this process 
warmth is produced and mostly lost. Also a part of the organic nitrogen is turned into 
gaseous nitrogen compounds and is lost. Shouldn’t we rather use the energy that is 
lost in the composting process? Or should we better use closed anaerobic 
fermentation in which the produced methane is used for energy and the nitrogen is 
not lost. And what is the value of residue of fermentation (digestate) for soil 
improvement? Research on this topic has only recently started but there is no clear 
answer yet. There are many reports on the positive value of compost although not 
often compared with adding the same material directly to the soil before the 
composting process. Also the effect of using the digestate as a fertilizer and soil 
improver hasn’t been very well compared and evaluated. From digestate the fluid 
fraction has a high content of nitrates which can be used in a similar way as a 
chemical nitrogen fertilizer. The solid fraction contains a quite stable form of organic 
matter. At least it would be worth while to consider fermentation of organic matter 
instead of composting.  
 
I would like to go back to strategies to cope with the degradation of our soils. Two 
major strategies are conservation agriculture and organic agriculture. From both 
strategies there is a great deal of evidence that they are able to maintain or improve 
soil quality. 
Conservation agriculture focuses on minimal soil mechanization and on returning 
fresh crop residues to the top soil or to the soil surface. The rejection of intensive soil 
cultivation also reduces the use of fossil energy. 
Organic agriculture has it focus more on (re-)using organic materials such as 
compost and manure for fertilization and soil improvement. In most cases this 
manure and compost is incorporated in the soil with a mechanical soil treatment. Also 
the rejection of the use of synthetic pesticides and fertilizers is considered to be 
beneficial for the soil. Another important effect of the rejection of synthetic nitrogen 
fertilizer is a strong reduction of fossil energy use and emission of laughing gas, both 
caused by the production of synthetic nitrogen fertilizers.  
Both strategies have in common the focus on the use of cover crops and green 
manures thus cover crops serve as protection of the soil and as input of organic 
matter in the soil. 
The claims of both strategies for a higher soil organic matter level in the soil have 
been proven to be right in many experiments and studies. Although in some case 
studies no differences were found between organic and conventional or conservation 
and conventional systems. The result of the strategy strongly depends on the way it 
is applied and on the environmental circumstances and soil status. But in general, 
both strategies showed to have positive effects on the soil quality.  
There are also claims from both strategies to reduce laughing gas emissions 
although the evidence for these claims is fragmented and sometimes contradicting.  
So what if both strategies could be combined? Is this possible and would this give an 
additional positive effect? Theoretically there could certainly be additive effects.  A 
lower energy use for soil cultivation would be additional for organic agriculture. The 
decrease of energy use and laughing gas emissions because of the zero input of 
synthetic nitrogen fertilizer would be additional for conservation agriculture, but what 
about soil organic matter?  None or very few long term experimental results are 
available for this combination.   
 
The 5th International Scientific Conference on Sustainable Farming Systems                  E C O M I T  
 
 
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Several organic and conservation farmers already are using part of each others 
strategies. Organic farmers tend to reduce their intensity of soil cultivation. There are 
also farmers who are successfully combining conservation and organic agriculture. 
Most examples however, deal with systems with only mowing crops in the rotation. 
The main challenges for the combination of the organic and conservation strategy 
are in growing root crops, in the control of weeds, in preventing a decrease of soil 
structure by compaction and in a sufficient soil temperature in spring. Part of the 
solution might lie in the application of modern techniques, like GPS for controlled 
traffic systems and to be able to mechanically control weeds very close to the plant, 
sensors to recognize weeds from culture plants followed by mechanical removal of 
the weed. 
There are also a lot of other effects of the combination we don’t know of. What about 
yields, pests and diseases, biodiversity etc?  
Considering the possible additive effects of combining both strategies it would be 
worth while to explore this combination under different conditions, with different crops 
and making use of what modern techniques have to offer. The first step would be to 
bring the organic and conservation movement together and to exchange knowledge, 
experiences and ideas. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 


Organic and conservation agriculture, the best of both worlds?

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