Due to the intrinsic diversity of soils and the need to collect an appropriate number of field observations, which are particularly useful for the parallel research trials run at the Soil Hydrology Laboratory of IAMB, a specific device for the field determination of hydrologic parameters in porous media has been developed, as shown in the figure below.
The apparatus uses a double-comb network of dripping lines, constituted each by three overlapping lines supporting 2.5 m spaced self-compensating drippers with a flow rate ranging between 2 and 12 l/h. The parallel monitoring of water contents and of soil water pressure potentials will be ensured through TDR probes and tensiometers, respectively.
Soil hydrological properties will be estimated from three-dimensional flow fields under the drippers in different monitoring sites.
The experimental trials run at CIHEAM Bari are described below.
The study area covers 462m2 and includes three transects of 30mx4.2m. The trial is illustrated above.
Unlike empirical models, inversion models are physically based and are more reliable in returning specific electrical conductivity at different depths.
The experimentation has proposed an innovative approach in the study of the mechanisms influencing water and/or salt stress in the plant. The study is directed not only to survey each single site but is aimed to identify the spatial scale that determines plant response to salinity.
Plant water storage is mainly related to the soil hydrological properties. Therefore, defining irrigation uniformity on the surface is not sufficient to determine the soil available water. The uniformity determined on the surface takes into account only the hydraulic properties of the irrigation system (e.g. flow rate, pressure). The trial is intended to identify an indicator quantifying soil uniformity. On this basis, three experimental trials have been set up and are shortly described below.
A four-sprinkler system has been set up over an area of 16mx16m (256m2). Three TDR probes 15cm long have been installed at three different depths (10, 20 and 30cm) every 3m covering the entire study area. Irrigation uniformity has been determined at three different pressures (4, 3 and 2 bars). The objective of the trial is to assess surface uniformity at three different pressures and determine soil uniformity indicators (e.g. Application Efficiency, AE, Soil Water Storage Efficiency, SWE).
A uniformity trial is conducted over an area of 150m2. Drippers are placed 1m apart from each other on three rows corresponding to three different flow rates (2, 4, 6 l/h). Irrigation is managed applying conventional water to bring the soil moisture profile to field capacity. Soil hydraulic parameters are monitored by means of a TDR probe of 25cm inserted vertically on the soil surface to monitor the temporal evolution of water contents.