Monitoring the temporal evolution of soil structure of three innovative production systems in the field

Alternative agricultural practices emerge to provide more sustainable productions systems and to meet
tomorrow's diets. These practices and varying climatic conditions will have impacts on soil structure and
thus, on soil hydraulic properties. However, most models do not consider the temporal variability of soil
hydraulic properties, which can lead to poor decision making. Thus, quantifying the temporal evolution of
hydraulic properties is essential to better understand the impact of emerging agricultural practices on soil
structure (Chandrasekhar et al., 2018).

In most studies, temporal variation of soil hydraulic properties is investigated using punctual
measurements in the field or in the laboratory (Alskaf et al., 2021; Geris et al., 2021). Results are often
inconsistent between studies due to the timing and type of measurement performed (Chandrasekhar et
al., 2018; Strudley et al., 2008). In addition, most research focuses on the topsoil layers and does not
consider the longer term effects on the deeper layers of the soil (Wahren et al., 2009).

In this research, temporal evolution of the hydraulic properties of three innovative production systems is
continuously monitored up to 90 cm depth. The three systems are designed to disrupt current agronomic
trials and aim to produce the ingredients of tomorrow’s diets. They are pesticide-free and have long-term
rotations of 8 years with intercrops. These systems are implemented on 8 parcels of the University of
Gembloux Agro-Bio Tech on a typical loamy soil in Belgium.

The innovative systems were instrumented with 24 Teros 12 water content and 24 Teros 21 water
potential sensors from MeterGroup. Both types of sensor are robust and highly accurate. The Teros 12
probes also measure soil temperature and salinity. Potential probes can measure potential over a wide
range of values from -9 to -2000 kPa. All probes are connected to MeterGroup's ZL6 data loggers which
allow real-time data collection. The water content and potential probes are placed in parallel in the first
three soil layers at 30, 60 and 90 cm depth in 8 plots. Intact soil cores are also taken every two months to
determine bulk density and total soil porosity.

The simultaneous determination of both water content and water potential over time under natural
conditions allows the temporal evolution of the hydrodynamic properties to be captured at the level of
the first three horizons. This monitoring will make it possible to quantify the temporal evolution of the
structure of a loamy soil under the effect of alternative agricultural practices and varying climate
conditions. The first two years were contrasted in climatic conditions with a wet and a dry year. In addition,
a diverse range of agricultural practices with different crops such as beet, camelina, corn, rapeseed and
winter wheat were grown in both years. The results of these first two years of monitoring will be presented
at the EGU 2023 General Assembly and compared to theoretical properties that would be obtained using
classical PTF.