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Switzerland: does organic farming enhance soil fertility?


For what will it profit a man if he gains the whole world and forfeits his soil?”

Edward Goff, organic dairy farmer, with acknowledgment to Matthew 16:26

Switzerland has been at the forefront of the organic farming movement from Bircher Benner and his whole and raw food diet (muesli) developed in the latter part of the 19th century through to the appointment of Prof Hardy Vogtmann as the first director of the Swiss Research Institute for Organic Farming (FIBL) in 1974. One legacy of Hardy’s tenure is the worlds longest running farming systems trial, the DOK-trial, set up in 1978, comparing non-organic, organic and biodynamic farming systems. That alone was enough to take me to Switzerland in my quest for robust information on soil analysis, soil management and its impact on food quality and the environment.

While organic farming has clearly led the way, just as in many other countries non-organic farming has been inspired, cajoled or forced to adopt more sustainable farming methods. Switzerland has for many years had a policy of only providing grant support to “integrated” and more “sustainable” farming systems, it has a unique national programme monitoring soil status and hosts one of only three trials world wide undertaking comparison of Albrecht soil analysis and management methods.

FiBL and the DOK trial

The Research Institute of Organic Agriculture (FiBL) https://www.fibl.org/en/homepage.htmlundertakes research, provides advice and information and facilitates the adoption of organic farming through market development, reflected in it’s Activity Report https://www.fibl.org/fileadmin/documents/en/activity-report/FiBL-Activity-report-2016.pdf My hosts, Urs Nigli, Robert Obrist, Else Brunemann-Konig and gave me a fascinating insight into the work of FiBL and a visit to the DOK trial site.

The DOK-trial, now it’s 40th. year has shown that not only is organic farming based on crop rotations possible from a practical perspective, including soil fertility and weed and disease control, but that it delivers on important aspects of food quality and environmental impact. Even the yields are reasonable and 5,000 Swiss organic farmers show that it is financially viable too.

The latest report from FiBL of the key findings of the trial are available https://okologi-kongres.dk/wp-content/uploads/2017/12/G2-Fliessbach_DOK_Kolding2017.pdf

The replicated trial follows the same 7-year crop rotation for the conventional, organic and biodynamic systems, based on a 2-year grass-clover ley and including wheat, potatoes and currently soya and maize. The soil nutrient management includes the use of FYM or compost and slurry together with standard fertiliser applications and permitted mineral fertilisers where needed on the organic and biodynamic. The conventional used standard fertiliser inputs with a split treatment, with and without manure. Input of N, P and K was nearly 50% less on the organic systems, which produced yields only 20% less than the conventional: nutrients appear to be much better utilised in the organic systems due to the root symbiosis with soil rhizobia and mycorrhizae. The organic systems showed a deficit in P and K; the fact that available soil levels had stabilised and not declined to a critical point indicates that for the foreseeable future the systems are able to draw on the very large reserves of P, which are otherwise not available to crops. In fact under organic management reserve K even increased while remaining at a constant level under conventional. This is more a process of “soil creation” rather than soil mining, making best use of soil reserves and avoiding the environmentally damaging process of mining finite reserves of rock fertilisers. It does of course mean that organic farmers should at least continue to monitor soil levels carefully and be prepared to make adjustments to cropping and provide additional use of inputs if necessary.

The key findings and lessons from a soils perspective are:

  1. Soil nutrient levels have held up under organic management with only occasional permitted mineral fertiliser inputs. There was some initial decline in P but subsequently they have stabilised at non-critical levels.

  2. Crop yields have been maintained. The relatively small difference (73%) between organic (5.5 t/ha) and conventional (7.5 t/ha) wheat may be partly due to the routine use of cattle slurry on the growing organic crop.

  3. The organic resulted in slightly higher SOM levels than the conventional, but both showed a small decline over 30 years. The Biodynamic showed a small increase, which may be due to the use of composted rather than fresh manure.

  4. Biodynamic appears to improve the N availability early in the spring, possibly due to compost stimulating free-living N fixing organisms.

  5. The organic systems result in greater soil microbial diversity than conventional farming, primarily as a result of the use of manure, although it is not clear if that is acting as an inoculum or as a substrate.

  6. Organic systems increase water percolation and soil stability and hence reduces erosion risk

  7. The organic systems increase soil surface arthropods (double) and earthworms (40%).

The role of Soil organic Matter (SOM) and the effect of different farming methods on organic matter quality and quantity I have covered in some detail elsewhere on my blog.

FiBL is involved in a number of other interesting projects:

Use of human waste

The principle of nutrient recycling and return of human waste to the soil should by now be basic to all societies. But, as in Germany, human waste is prohibited on all farmland in Switzerland. In the UK of course it has always been permitted https://www.gov.uk/government/publications/sewage-sludge-in-agriculture-code-of-practice/sewage-sludge-in-agriculture-code-of-practice-for-england-wales-and-northern-ireland except for organic farming where the EU Regulation prohibits it. There is a ground swell of opinion in the UK to relax the rules for organic farming, but strictly on the basis that it is free from all chemical and biological contaminants. At FiBL they are experimenting with techniques that might be acceptable in Switzerland; these are almost certainly potentially useful to UK conventional and organic farmers including the use of urine from separation schemes, Phosphate recovery and “double loop “systems, which were also discussed on my visit to Denmark. Struvite, a high Phosphate granule produced from urine, is currently being considered for organic production.

Ultimately of course it is necessary for domestic waste to be separated from industrial waste and for households to stop using pollutants. Removal of residues from medicines may remain and issue.

Biogas digesters: As in Denmark there is great interest in Biogas digesters in Switzerland and use of the liquid and solid digestate on organic farms.

Soil Analysis

Switzerland has a national requirement that farmers analyse all fields at least once every 10 years, a basic pH, P, K, Mg analysis. A standard analytical approach is followed by both conventional and organic farmers but there are no guidelines for organic farmers reflecting the higher level of biological activity and the lower yield expectations. A useful guidebook http://www.organicresearchcentre.com/manage/authincludes/article_uploads/4002-soil-fertility.pdf provides the basics of soil management but does not consider the use of external sources of mineral fertilisers. This reflects the fundamentally different approach to that taken in the US and those closely following the Albrecht analysis and management system.

In practice both FiBL in its research work and commercial farmers are using a standard analysis service, with the addition of SOM in some cases. There is little use of trace element analysis or inputs and only recently has thought been given to monitoring Sulphur levels, which are known to be dropping to critical levels in many countries.

My interest in Albrecht soil analysis took me to the agricultural school and university at Oberacker, where the 20-year plough v direct drilled, rotational, conventional trial has been subdivided for the last 10 years to study the impact of following the Albrecht system, an explanation of the Albrecht analysis is given here

https://www.midwestlabs.com/resource/interpreting-soil-analysis

The trial has yet to be written up, which is disappointing given that its one of only three such trials in the world looking at the performance of Albrecht system. Matthias Stettler and Andreas Chervet, my hosts and the researchers involved, are very clear that there are significant differences in performance in certain crops such as barley as a result of the Albrecht management and their observation is that Albrecht is more effective under direct drilling than under ploughed systems, where the standard Swiss soil analysis and management regime is more effective. I could certainly see that the plots looked different, there is little that can said at this stage about the impact of Albrecht on yield, plant health or cost effectiveness.

The original and principle investigation of the Oberacker trial is into direct drilling v ploughing. Details of the project are available here https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=0ahUKEwjsvpWpzIDcAhXFe8AKHc92ASgQFghNMAc&url=https%3A%2F%2Fwww.landbrugsinfo.dk%2FPlanteavl%2FPlantekongres%2FFiler%2Fpl_plk_2015_show_06_Wolfgang_G_Sturny.pdf&usg=AOvVaw0LAwHlJ30i85lftZwHbuYs

and results here: https://www.researchgate.net/publication/303867929_Two_decades_of_no-till_in_the_Oberacker_long-term_field_experiment_Part_I_Crop_yield_soil_organic_carbon_and_nutrient_distribution_in_the_soil_profile

Table 1. Location of soil nutrients in the profile: A and B Ploughed, C and D Direct drilled

It should be noted that this trial is conducted under conventional farm management and that it uses a diverse rotation with beans and inputs are generally less than in the UK. The principle results of the trial are:

  1. Total carbon (organic matter) is similar for both the direct drilled and the ploughed plots

  2. Although the yields of some crops were favoured by either direct drilling or ploughing there was no significant difference in yield of all crops together, averaged over 20 years.

  3. The soil nutrient and carbon distribution in the soil profile was very different between the two treatments, Table 1. with direct-drilled soils having much higher levels near the surface. This may have implications for soil sampling depth.

  4. Earthworm populations were much higher (40%) in the direct-drilled plots.

My visit to Agroscope, near Zurich was kindly hosetd by Andreas Gubler and Ana Hug. In Switzerland Agroscope operates one of the most comprehensive national soils monitoring programmes that I have come across: 110 sites, mainly conventional, monitored every 5 years, covering all crops and including deep soils. Some sites monitored annually.

https://www.agroscope.admin.ch/agroscope/en/home/topics/environment-resources/soil-bodies-water-nutrients/nabo/alle-publikationen.html

The key lessons over 30 years are:

  1. SOM levels are relatively stable, an insignificant 3.5% drop is observed

  2. An increase in copper and zinc contamination levels due to use of pig slurry, even with strict legal limits. Lead and mercury contamination is declining.

  3. Soil bacterial (2000-3000) and fungi (300-600) numbers are not significantly different between grassland, arable and forest soils.

  4. The biological diversity is substantially different between soil uses.

  5. Subsoil structure damage at depth (i.e. 20 - 40cms.) is increasing due to the total weight of the machines used; subsoil structural damage is not a factor of ground pressure (kg/m2).

  6. Pesticide (75%) and antibiotic contamination of soils is increasing.

The use of penetrometer depends on soil moisture; at Agroscope they have developed a soil moisture correction factor.

Their view is that the Solvita CO2 respiration test is not precise as it is affected by temperature and moisture but it remains a useful indicator if samples are taken at the same time each year under similar temperature and moisture conditions.

Finally from my trip to Switzerland I should mention a useful technical leaflet produced by FiBL and the Organic Research Centre: The Basics of Soil Fertility http://www.organicresearchcentre.com/?go=Information%20and%20publications&page=Basics_Soilfertility


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