Case Study Experiment - increasing or maintaining soil organic matterThe RECARE researchers tested the effectiveness of various measures to increase or maintain soil organic matter. The main experiment involved grass undersowing in maize. Other experiments included the use a manure separator that differentiates between crops and fields with different soil quality and the application of humic acid.
|Grass undersowing in maize
- Grass undersowing in maize fields is expected to result in 0.5% extra soil organic matter (SOM) after 30 years, and also a little more production of grass in years with grass cropping. But since the measure was only started in 2014, the result is still unknown. Conversations with four farmers revealed that the SOM content has remained stable or slightly increased, and that the bearing capacity of the soil has improved.
- Average nitrate concentration in the upper groundwater in the area fluctuated around the EU-standard of 50 mg/l: in 2014 and 2017 it was above and in 2005 and 2016 below the standard.
- Farmers experienced variable results from grass undersowing, depending strongly on the weather, with good growth of the grass cover in wet years, but competition for water with the maize crop and no grass growth in dry years. Farmers frequently experienced poor grass cover.
- Drawbacks of the measure mentioned by farmers are that the undersowing may cause damage to the standing maize crop and in the headlands of the fields and that the sowing is a difficult task since it needs to be done at the right places and in the right period. It is difficult to perform in small parcels, and the weed control is more difficult.
- Farmers also indicate that grass undersowing is not effective in a grain maize crop, where only the maize cobs are harvested and the rest of the plant is frittered, thereby suffocating the undersown grass.
- Grass undersowing was evaluated by farmers and residents to foster regulating ecosystem services, namely the increase of the buffer function for organic matter and nitrogen and the bearing capacity of the soil. Also, cultural ecosystem services were found to be improved when fields remain green after the harvest of the maize crop, instead of showing brown stubble.
- However, the provisioning ecosystem services that were foreseen as a result of this measure (increase in feed crop yield and groundwater production) were not mentioned by the farmers as a benefit.
The Case Study area is located in the eastern part of The Netherlands. In general, soils are sandy to loamy in the region. The groundwater table varies between 0.5 to 2 m below surface in summer time. The area has two intake points of drinking water. Levels of Betazon, methylchlorophenoxypropionic acid (MCPP) and sulfite have risen in the intake water over the last decade. Land use is mixed with agriculture combined with hedges, small forests and small streams. Agriculture, in general, is small scale but relatively intensive in terms of livestock densities.
Main soil threat
The case study area 'Olden Eibergen' is characterized as a multifunctional rural area with a combination of agricultural and natural land use, and two drinking water intake areas. The main soil threat in this area is the gradual loss and decline of soil organic matter stocks. According to farmers on average agricultural fields have lost 10 to 30 tons of organic matter in the last 10 years. This threatens the agricultural quality of the soil as well as the potential of the soil to buffer leaching of nutrients and residues of crop protection. In the long term, agricultural productivity will fall, costs of agricultural inputs such as manure and crop protection will increase and the extra upstream costs for cleaning drinking water following intake of water will rise.
The loss of soil organic matter is due to a combination of factors, such as long-term and continued monocultures of maize on specific parcels, intensive seed potato cropping in the area, strict(er) manure legislation directed at minimizing nitrogen and phosphorus application to fields and limited inputs of exogenous organic matter. Some farmers try growing green fertilizer crops after the harvest of maize, whilst others try adopting alternative tillage techniques. Yet, farmers have only recently been confronted with the impact of decreasing organic content of their fields and have started to fully realize the implications of this for future production and income. Since the 1980's, enough organic matter was applied to fields with abundant animal manure. Now, the challenges of the Case Study area are to secure clean drinking water intake for the long term in combination with sustained agricultural production in the region. Knowledge gaps have been identified and include: how to better plan and disperse the manure at: i) farm level, or ii) regional level by exchanging manure or organic matter between different farm types (arable, goat, pigs, cow farms). Other ways to combat soil deterioration include introducing new varieties of crops such as highly productive grass species or early ripening maize that can be combined with post-harvest (second) catch crops. Technical solutions such as manure processing (thickening), or applying concentrated soil organic matter by-products from the drink water intake and cleaning (humine acids) will be considered.
Other soil threats
Other soil threats result from high input levels of nutrients due to intensive livestock farming in the area. Phosphate and nitrogen levels are in general high, due to a historically high input of animal manure (RAAP, 2008; Gelders Genootschap, 2012). However, due to reduced soil productivity as a result of low soil organic matter content, the farmer is sometimes forced to compensate stress periods in the growing season (dry or wet periods) with external inputs such as additional fertilizer, crop protection or irrigation. This exerts additional pressure on the system. Other soil threats include moisture deficits, contamination of groundwater and soil compaction.
Location and Digital Elevation Model (DEM) of Olden-Eibergen (SourceSRTM).
Geology & Soils
The soils in the Olden-Eibergen Case Study area are developed in cover sands and clayey and loamy sediments deposited by the small stream of Berkel (Figure 13.2). Most soils are podzols or cambisols; nutrient-poor soils developed in sand. The area also has patches of anthroposols, soils enriched in Medieval times with manure and organic residues. Phosphate and nitrogen levels in these soils are in general high.
Soil types in the Olden-Eibergen Case Study area (left); (right, source: Stiboka, 1979)
The Case Study area “Olden Eibergen” is a multifunctional rural area with a combination of agricultural and natural land use. The area is around 1,000 ha, of which 700 ha are used for agriculture with rotations consisting of potatoes, wheat and maize crops. The remaining surface is in use for small patches of forest, tree-lined field borders, recreational spaces and the homesteads of houses and farms. 40 agricultural enterprises own land in the area, as well as several 100 ha outside the area. The agricultural enterprises are small compared to the Dutch farms in the western part of the country (in terms of productivity and acreage), but the livestock density is large compared to the Dutch average.
Left: typical land use in the Case Study area of Olden-Eibergen: pasture with grazing cows and maize fields, intersected by tree-bordered roads. Picture: S. Verzandvoort;
right: Podzolic soil in pasture land. Picture: S. Verzandvoort
Climatological information on the study site is derived from the meteorological stations of Hupsel and Borculo, at respectively 2 and 15 km distance from the Case Study (Figure 13.4). Mean monthly temperature varies between 2 and 17°C. The long-term mean annual precipitation is between 800 and 825 mm, with the lowest amounts in spring, and the highest in autumn. The long-term average annual precipitation deficit is between 200 and 240 mm.
Average annual (left, source Royal Netherlands Meteorological Institute – KNMI at Twenthe)
Mean monthly (right) precipitation (meteorological station Borculo) and temperature (meteorological station Hupsel).
The groundwater table varies between 0.5 to 2 m below surface in summer time. The area has two intake points of drinking water (Figure 13.5, left). Levels of the pesticides Bentazon and MCPP have incidentally exceeded the norms for drinking water production between 1985 and 2009 in the water abstracted from the groundwater over the last decade (Vitens) (Provincie Gelderland, 2011).
Drivers and Pressures
The loss of soil organic matter in the area is caused mainly by the following drivers and pressures: long term monocultures of maize, intensive seed potato cropping, strict manure legislation directed at minimizing nitrogen and phosphorus application to the fields, and limited inputs of exogenous organic matter. This has caused a decline in production levels, problems with too dry and too wet soils, and rising nitrate concentrations in the groundwater.
Monoculture of maize is performed on fields located on podzolic soils low in soil nutrients (‘veldpodzolgronden’), at larger distance of the homesteads. The use of pig manure on these fields (low in organic matter compared to other types of manure) contributed to the decline in organic matter compared to other fields. The stricter manure legislation since January 2014 derives from the European Nitrates Directive. This legislation forces farmers to process or export the manure produced on their farms above the threshold.
Status of soil threat
The Province of Gelderland is currently implementing a sustainable resource management policy, and supports projects on nutrient use efficiency, like the project Gezond Zand (2010-2014) (Rienks and Leever, 2014). All farmers participating in the Gezond Zand project collected information on the organic matter content of their fields in 2000 and 2010. The soil organic matter content decreased in this period on the fields with continuous maize cultures or other arable cultures, mostly situated on the “field podzol” soils, that are inherently poor in nutrients, and that mainly receive pig manure. The decrease was up to 5% in some fields (below right) (Rienks and Leever, 2014).
Left: Areas with protected groundwater for drinking water supply. The purple line depicts the outline of the study area. Source of data: ROM3D, Gezond Zand.
Right: Soil organic matter decline between 2003 and 2010. Source data: ROM3D and the farmers participating in the Gezond Zand project.
Maps on the current state of land use, soil degradation and soil conservation in the case study area have been produced using the WOCAT (World Overview of Conservation Approaches and Technologies) methodology
The steps of this process are as follows:
1) The area to be mapped is divided into distinctive land use systems (LUS). 2) The team gathers the necessary data on soil degradation and conservation for each LUS using a standardised questionnaire, in close consultation with local land users, and supported where possible by remote sensing or field data. 3) For each LUS, the soil degradation type, extent, degree, impact on ecosystem services, direct and indirect causes of degradation, as well as all soil conservation practices, are determined. 4) Once collected, the data is entered in the on-line WOCAT-QM Mapping Database from which various maps can be generated.
Following the principles of all WOCAT questionnaires, the collected data are largely qualitative, based on expert opinion and consultation of land users. This allows a rapid and broad spatial assessment of soil degradation and conservation/SLM, including information on the causes and impacts of degradation and soil conservation on ecosystem services.
More details about the methodology used to produce these maps and their interpretation can be found here.
Land Use (click on maps to expand)
The degree of degradation reflects the intensity of the degradation process, whilst the rate of degradation indicates the trend of degradation over a recent period of time (approximately 10 years).
The "effectiveness" of conservation is defined in terms of how much it reduces the degree of degradation, or how well it is preventing degradation. The Effectiveness trend indicates whether over time a technology has increased in effectiveness.
RECARE data repository
Data collected from the case study area for the project are held in a repository on the European Soil Data Centre (ESDAC) website hosted by Joint Research Centre (JRC). Below is a list of the data held.
To access the data click HERE (currently only accessbile with EUECAS login details)
Effects of soil threat on soil functions
The table below summarises and ranks the effects of soil organic matter decline on the soil functions in Olden-Eibergen.
|Functions of soil
|Decline of feedstock production (hay, maize, grass)
|Leaching of nitrate and pesticides to groundwater
|Gene reservoir/ Biodiversity pool
|Source of raw materials
|Decline due to soil organic matter decline
|Patterns of SOM development inform about the cultural history of the area. The effect is moderate since the enriched soils are depleted at a smaller rate than the soil without historical enrichment.
Effects of soil organic matter decline on soil functions. (L: Low; H: High; N: None)
Administrative and socio-economic setting
“Olden Eibergen” is located in Achterhoek (NUTS3: COROP14), in the Province of Gelderland (NUTS 2: NL22). The farmland in the area is owned or rented by farmers. The most important policy and legislation that influence farmers’ choices in land management include the national manure legislation, resulting from the EU Nitrogen Directive. This legislation limits the amount of manure that farmers may apply to their field to a maximum per enterprise. However, manure availability is unevenly distributed among farmers. The ambition of the sustainable land management approach taken by the farmers and the Foundation HOEDuurzaam is to enable the exchange of manure between farmers.
The Common Agricultural Policy also influences the choices of the farmers, since due to the disappearing of the milk quota as off 1-4-2015, the production will be increased. Nevertheless, the recent abolishment of the milk quota has not driven the decline of organic matter during the period considered. The SLM measures currently implemented by the farmers are eligible for subsidy from the CAP for good agricultural practices under pillar III, because of the foreseen impacts on water quality, soil quality and climate. The Water Framework Directive is also influential since better functioning soils will lead to reduced impact on local and regional water systems.
Based on the environmental and sustainability policy of the Province of Gelderland, farmers also receive subsidies for the land management measures.
Population of the municipality Berkelland, The Netherlands (left, Source: STATLine, Central Statistics Agency of The Netherlands);
GDP per capita trends for the Euro Area, the Netherlands and the regional economy (Sources: EUROSTAT, STATLine, Central Statistics Agency of The Netherlands (accessed 6-4-2015))
The land management measures currently implemented in response to declining organic matter include the growing of green fertilizer crops after the harvest of maize. Other farmers try adopting alternative tillage techniques. Yet, farmers only recently have been confronted with the impact of decreasing organic content of their fields and have started to fully realize the implications of this for future production and income. Since the 1980’s, enough organic matter was applied to fields with abundant animal manure. Now, the challenges of the Case Study area are to secure clean drinking water intake for the long term in combination with sustained agricultural production in the region. Knowledge gaps have been identified and include: how to better plan and disperse the manure at: i) farm level, or ii) regional level by exchanging manure or organic matter between different farm types (arable, goat, pigs, cow farms). Bridging these gaps will provide additional solutions to the users. Other ways to combat soil deterioration include introducing new varieties of crops such as highly productive grass species or early ripening maize that can be combined with post-harvest (second) catch crops. Technical solutions such as manure processing (thickening, separation) or applying concentrated soil organic matter by-products from the drink water intake and cleaning (humic acids) are in the experimentation phase.
Relevant end-users and local stakeholder groups include;
20 to 30 farmers in the area
Vitens drinking water company
Local sustainable energy company using biomass as green energy input
Municipality of Berkelland
Regional Water Board Rijn & IJssel
ROM3D advising company
The farmers will be asked to look up field samples they have available of their soils. For each farm a soil organic content map will be made of the current and historical situation. Based on these maps, a plan will be discussed between farmers and ROM3D consulting on how to improve on the longer term. For each parcel of land, measures will be agreed upon with the farmers and monitoring will start. Vitens drinking water company, the Municipality of Berkelland and the regional Water Board will make available organic matter from their own land such as mowed grass and reeds. These will be processed into organic matter for the farmer's fields. Furthermore, farmers will implement measurements such as adapting their crop rotation, zero tillage, and make use of green fertilizers. Not only at parcel level but also at farm and regional level, better dispersion of available organic material will occur.
Rienks, Willem en Leever, Henk, 2014. Gezond Zand. Met een verbeterde bodemkwaliteit naar een betere waterkwaliteit Haarloseveld en Olden Eibergen. Stichting Marke Haarloseveld Olden Eibergen en omstreken. HOEduurzaam, www.hoeduurzaam.nl
Gelders Genootschap, 2012. BERKELLAND BESCHREVEN – Cultuurhistorische gebiedsbeschrijving. 162 pp.
Provincie Gelderland, 2011. Gebiedsdossier Haarlo - Olden Eibergen. Aequator and Royal Haskoning BV. 56 pp.
RAAP, 2008. RAAP-rapport 1748, P 28-29.
W.A. Rienks en H. Leever, 2014. Gezond Zand – organische stof als sleutel voor een vruchtbare bodem en schoon water. ROM3D en Stichting Marke Haarlose Veld Olden Eibergen.
Stiboka, 1979. Bodemkaart van Nederland schaal 1 : 50 000 - Toelichting bij de kaartbladen 34 West en 34 Oost Enschede - 35 Glanerbrug. Wageningen, Stichting voor Bodemkartering