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Soil management principles in climate-smart conservation <BR>agriculture to halt and reverse land degradation (Communication session)
EUROSOIL2020CONT-2181
IMPACT OF FARMING PRACTICES ON SOIL QUALITY: INSIGHTS FROM A LARGE SCALE SURVEY IN SWISS JURA
Ophelie Sauzet* 1, Alice Johannes2, Adrien Matter1, Karine Gondret1, Saskia Leopizzi1, Pascal Boivin1
1Soils and Substrates Group, Institute Land-Nature-Environment, University of Applied Science of Western Switzerland Hepia, Geneva, 2 Soil Fertility and Soil Protection Group, Department of Natural Resources & Agriculture, Swiss Federal Research Station Agroscope, Zurich, Switzerland
Content: Effects of farming practices are often studied at annual or rotation scale and long-term impacts assessments are thus still expected. Long-term experiments, associated meta-analysis based on exhaustive literature review and modelling have generated relevant information about the long term effects of a given farming practice on soil properties. However, on-farm data incorporate responses to the ever-changing environment to which farmers need to adapt. The main objective of this study is thus to determine the on-farm long-term effects of farming practices on soil quality.
This survey was performed in the frame of the project « Terres Vivantes » launched in 2019. It is based on the volunteer participation of 90 farmers (3'000 ha of arable land). Farmers aim at improving their soil quality and mostly pointed out the need for improved structure quality and soil organic carbon (SOC) level. After having selected two fields in each of the 90 farms, the VESS spade test was used to assess soil structural quality while SOC:clay ratio was used to asses soil structure vulnerability[1]. Target values and sampling requirements of both indicators are already established[2]. In addition, air and water content at -100hPa (i.e. porosity>15µm) was determined on undisturbed soil samples to determine the soil structure quality index proposed by[3]. The general characteristics of the farms and the past 10 years practices on both fields were documented and organized according to 3 categories: vegetation intensity (main and cover crops diversity, soil cover), organic amendments (nature and quantity) and intensity of soil tillage practices. Principal component analysis and correlation tests were used to examine how the set of farming practices was related to the set of soil quality indicators.
The clay content of the soils ranged from 16% to 60% with half part of heavy clay soils. The median VESS score was 2.3 and 35% of the undisturbed samples presented air content at -100hPa below the acceptable limit of 0.068 cm3g-1, while bulk density values did not show compaction thus revealing a degraded soil structure, namely small fine structural porosity volumes. The median SOC:clay ratio of 8% revealed vulnerable structure. Surprisingly, neither the SOC:clay ratio nor the compaction level were influenced by high clay contents. The major soil improving practices were temporary pasture duration, number of organic amendments, and soil cover duration by main crops. Surprisingly, cover crops did not influence positively the soil quality due to inverse correlation with temporary pasture duration. Moreover, most farmers used mechanical weed-control in summer preventing cover crops biomass maximisation. The number of machinery passages for tillage and stubble cultivation, and the proportion of row crops showed negative impact on soil quality.
These results are to be discussed according to their combined effects at farm scale, potential antagonistic or indirect effects of some technical choices with respect to soil quality objectives, and can be relativized in regards to larger variety of practices, in particular conservation agriculture.
[1]V.Fell, A.Matter, T.Keller, et P.Boivin, 2018, doi: 10.3389/fenvs.2018.00134
[2]S.Leopizzi, K.Gondret, et P.Boivin, 2018, doi: 10.1016/j.geoderma.2017.11.003
[3]A.Johannes, P.Weisskopf, R.Schulin, et P.Boivin, 2019, doi: 10.1016/j.ecolind.2019.05.040
Disclosure of Interest: None Declared
Keywords: agricultural managenent practices, cropping systems, On-farm data, soil quality indicators, Soil structure