Geographical description

The study site is located near Frauenfeld (47° 34’ N, 8° 52’ E), the capital of the canton Thurgau, in the northeastern part of the Swiss Midlands. The main river is the Thur, a tributary to the Rhein. The soil, situated on a wide valley bottom at 385 m above sea level, is a calcaric fluvisol (alluvial deposits). The topsoil is a sandy loam. Layers of coarser material are found in the subsoil. The organic carbon content varies between 5x10-3 and 0.5x10-3 kg kg-1. The bulk density is 1.4 kg l−1 and the pre-consolidation load is 80 kPa. The experimental area of 1 km2 is situated in the plain of the river Thur with a surface area of about 15 km2

Pedo-climatic zone
The site is under two predominant influence climates: the continental and the Alpine South climates. Annual average temperature is about 11.2 °C and precipitation is abundant (906 mm year-1) due to the proximity of the prealpine relief in the South. The study site situated in low sloping land has low risk to surface runoff generation but filed inundation is not excluded, while it has high susceptibility to leaching (fluvisol, draining soil structure until the ground water table at about 1.5 m depth).

Cropping system

Cropping intensity

In Frauenfeld site, both conventional and conservation cropping systems are used. Depending on the soil moisture conditions and the rut depth after the harvest, rotary cultivator or plow (furrow wheel) are used, especially before sugar beet and potato crops. All produced animal excreta (pig liquid manure, rotted manure including straw from beef fattening), straw residues of maize and beet leaves will be returned or incorporated to the soil. Minimum soil tillage (harrow) is used after potato. The rotation constellation including artificial meadow and special cultures (strawberries) is not favorable for controlled traffic farming (CTF).

Types of crops
The rotation includes the following crops: corn as starter crop, then sugar beet, potato and cereal (winter wheat or spring barley). In the case of annual artificial grassland or annual strawberries, sowing or planting occurs after cereal.

Management of soil, water, nutrients and pests
The management has to be done according to the proof of ecological requirements of FOAG, Federal Office for Agriculture. The root and tuber crops occupy an important place in the rotation (between 60% and 75%) weakening soil structure of the topsoil. In summer, when the crops suffer from drought, irrigation overcomes this deficiency for root, tuber crops and strawberries and helps to establish artificial grassland in August. Water used for irrigation is provided from the water table with a level of about 1.5 m from soil surface. Except for the strawberries, the organic fertilizers in form of liquid manure (from pig production) or rotted manure (from fattening cattle) will be applied directly after harvest for the nitrogenous, phosphate and potash needs. Additional drilled mineral nitrogen fertilizers are reserved for cereals (ammonium nitrate), potato (ammonium sulfate) and corn (urea). For the fight against weeds, selective herbicides will be applied: corn, sugar beer, strawberries (soil and foliar herbicide) and cereals (contact herbicide). Fungicide and insecticide are used especially for potato: between 7 and 10 applications for potato blight (Phytophtora infestans), and 1 application for Colorado beetle (Leptinotarsa decemlineata).

Soil improving cropping system and techniques currently used
Soil cropping systems and techniques used in the site are: soil tillage, reduced plowing, combination seed drill for cereals after potato, flotation tires on traction vehicle. The precision by sowing and planting is ensured by mean of GPS. Trickle irrigation is used for strawberries.

Flotation tyres topspoil degradationtopspoil degradation
Flotation tires by seeding with a combination seed drill (Photo of the Etudy site, 14.10.2010) Effect of topsoil degradation due to heavy machines in corn field (Photo of the study site, 22 Sept. 2000)

Problems that cause yield loss or increased costs
Yield loss is closely linked to soil properties, climatic conditions, selected crops in the rotation and the peak workload over the year. Although the water reserves are abundant, soil suffers from drought during summer months when rain becomes rare due to its high infiltration capacity and low organic carbon content. In autumn, depending of the precipitation intensity, the risk of compaction is high. Yield loss in the corn is about 20 % in the ruts of heavy propelled harvester. Due to the peak workload during September and October, the harvest of silage maize and sugar beet is often delayed. The compaction risk under wet soil conditions causes crop loss. There is, also, not enough time remaining for cover cropping and green manuring in autumn. Stubble and organic residues are hardly decomposed and nitrogen mineralization remains blocked prejudicing the next culture. The structure degradation associated with rainfall regime and the harvest calendar is generally limited on the topsoil and disappears in the short or medium term.

External drivers and factors

Institutional and political drivers
While agricultural and environmental policies of Switzerland have been defined autonomously with regard to Europe, basic features of the respective European and Swiss policy frameworks are rather similar (e.g., high degrees of protectionism, direct payments for ecological and other services, strong presence of public regulation). The national ordinance on direct payments contains a clause that farmers who intend to receive direct payments must take suitable protection measures against soil degradation and water contamination. Subsequently, cantonal authorities, such as soil protection agencies and agricultural offices, began to develop different approaches to implement these regulations: they devised special control systems using soil erosion risk maps and agricultural inspectors. They are also conducting training courses, producing information leaflets, and implementing financial support programs for no-tillage.

Societal drivers
Public opinion: there is an increasing demand of local and biological products in Switzerland. There is also a real competition with European products that offer equivalent but cheaper products. These facts create a food system in which the buyers influence the prices, and farmers must comply. Biological products take an important place in the demand, since they have become part of conventional markets (from farm gate sales to major retail chains).

Bio-physical drivers
Based on regional climate models, future summers are likely to occasionally favor more frequent extreme events that result in catastrophic flooding, despite a general trend toward drier summer conditions. These changes will have significant impact on crops in many ways (e.g., delay in harvest and increase in the peak workload during some months). In addition, soil degradation and deficient soil aeration will be caused by the use of heavy agricultural machinery.