Long-Term Trials – What We Can Read Between the Lines
Agroscope maintains and supervises several long-term trials in Switzerland to enable the investigation of longer-term changes in soil quality and in the soil functions that depend on these. Long-term trials are conducted over several decades in order to gain an understanding of slowly unfolding processes that take place over these periods of time and cannot be evaluated in shorter trial periods. The experimental plots are managed with various approaches in order to determine how agricultural management practices such as crop-rotation, fertilisation, tillage, field traffic or farming system influence soil quality and soil functions over the long term, as well as whether side-effects for other ecosystem components are involved. This is the precondition for the proper assessment of the impacts of slowly unfolding processes and for ensuring that management practices are truly sustainable.
An adequate and balanced supply of nutrients is essential for yields and yield quality. In six crops cultivated in parallel, the Demo trial vividly demonstrates the effects of different organic and mineral fertilisers as well as deficiency symptoms under inadequate supplies of nitrogen, phosphorus and potassium.
Originally designed as a comparison of conventional and organic farming systems, today the DOK trial serves as a platform for a wide variety of scientific studies. Biodynamic (D), bioorganic (O) and conventional (K; German: konventionell) treatments are used to study aspects of soil fertility, productivity, climate impact and the resilience of agricultural systems.
Must agricultural intensification necessarily entail higher pressure on the environment? The FAST long-term experiment deals with this issue by investigating the impact of conventional and organic farming combined with tillage of varying intensity and intercropping on productivity and ecosystem services.
Tillage and fertilisation are crucial for the quality and functionality of soils. The Oberacker trial demonstrates the effects of no-till and ploughing, combined respectively with the GRUD/PRIF and Kinsey fertilisation concepts, on six crops cultivated in parallel. In addition to a focus on crop performance, there is a strong emphasis on the investigation of chemical, physical and biological soil properties.
Trafficking agricultural soils with increasingly large and heavy machines has a negative effect on the quality of these soils. The Soil Structure Observatory was set up to study the behaviour of compacted soils and their regeneration processes. A network of sensors measures how various soil status parameters react to soil compaction.
Besides fertilisation, the nutrient supply of arable crops depends strongly on soil and climate conditions. The STYCS trials are designed to investigate the influence of site characteristics on the soil nutrient content necessary for optimal yields on seven sites in Switzerland. The findings contribute to the improvement of fertilisation recommendations.
Since 1949, the influence of mineral and organic fertilisation and their combination on yields and yield quality as well as on soil quality parameters has been investigated in Switzerland’s longest-running experiment. The time series covering more than 70 years of measurements permit the evaluation of the sustainability and climate impact of different fertilisation approaches.
Studying infiltration and leaching processes in soil is an intricate matter. The two lysimeter facilities in Zurich-Reckenholz contain 12 and 72 vessels in which soil bodies can be studied from every angle. They shed light on the percentage of precipitation that re-evaporates, and the amount of water, nutrients and pollutants that enter the groundwater.