Tachenhausen, Germany (48°38’57” N, 09°23’04” E). The experimental site is located 360 m above sea level.
Atlantic Central climate with average annual temperature of 10.2 °C and an average annual precipitation of 856 mm. The soil type is classified as Luvisol with a silty loamy texture and with the following characteristics: 1.4 mg P and 1.6 mg K kg-1 dry soil (extractable in calciumacetate-lactate solution) indicating sufficient phosphorous and potassium supply, pH (CaCl2) 6.8.
Types of crop
Maize, wheat, soybean, maize
Management of soil, water, nutrients and pests
Long-term non inversion, no irrigation, application of nutrients according to official recommendations (VDLUFAmethod) and expected yield, pests according to decision support systems, such as proplant or isip, etc.
Soil improving cropping system and techniques currently used
No tillage and conservation tillage as a means to improve soil biology, rootability, aggregate stability, and to reduce erosion and run-off from the field.
Cover crops compiled of at least 5 species are sown before a following spring crop, to improve soil biology and chemistry, to control weeds and to protect the soil from erosion and water losses. The cover crops are established as soon as possible after harvest of the pre-crop and kept on the field over winter. As the species are not winter-hard, they are expected to die off over winter and to produce a mulch layer on the soil until sowing the following crop.
Problems that cause yield loss or increased costs
The yields of winter wheat and winter oilseed rape are not as high as expected at this site: 7.4 t/ha winter wheat (8.5 – 9.5 t/ha should be possible), 3.5 t/ha oilseed rape (4.0 – 4.5 t/ha should be possible). The reasons are not fully understood. Suboptimal soil structure and soil biology may be one of the reasons.
External drivers and factors
Institutional and political drivers
Since 2015 Common Agriculture Policy (CAP) requires greening measurements. Additionally, national agrienvironment schemes, e.G. FAKT in Baden-Württemberg, support means to improve soil fertility and the agroecosystem in total. These means should enable the farmers to adopt conservation agriculture more easily than in the past. Conservation Agriculture (CA) consists of soil conservation by zero-tillage, an adequate crop rotation and permanent plant cover using cover crops.
The society is not aware of the problem of soil erosion and water pollution by run-off of agricultural sites. Production systems without soil tillage or very litte tillage that reduce erosion and run-off, imply a higher demand for adequate weed control, hereby making a clearance of the field necessary to count for omitted tillage. The usage of additional herbicides, in particular non-selective herbicides such as glyphosate or glufosinate is seen as most problematic by the public. Recently, glyphosate was evaluated as potentially cancerogen. So, it will be a great challenge to create non inversion or even zero-tillage systems without using non-selective herbicides. The aim of Conservation Agriculture is to control weeds by fast growing cover crops instead.
Conservation Agriculture has the potential to improve yields and especially to enhance yield stability under conditions of climate change. Climate change for most parts in Germany, particularly the south west, is predicted to result in increased rainfall in the winter and decreased rainfall in summer. At the same time temperatures are expected to rise and the probability of extreme weather events is assumed to increase as well. So, in the future systems are needed which can withstand heavy rainfall as well as longer drought periods. Permanent plant cover fulfils both functions. It protects the soil against erosive rainfall and it reduces unproductive evaporation during the vegetation period. Additionally, soil structure and biological activity may be enhanced due to additional C-input via plant material and root exsudates which have the potential to enhance soil life.
The content of fusarium toxins in wheat kernels 2014 is shown in Table 1. Apparently, the concentration of fusarium toxins was reduced in plots where cover crops had been grown two years before (after wheat 2012, before maize 2013). In addition, microbial biomass was increased in plots where cover crops had been grown 2012 and 2014. These preliminary results show that there may be effects that need further elucidation. Presumably, also nutrient availability will be affected by cover crops growth.