Effect of plant mucilage on retention and flow of water in soils with different textures

Previous studies showed that mucilage extracted from chia seed enhanced retention and flow of water in dry conditions due to the intrinsic features of mucilage (increasing viscosity, water-holding capacity, and decreasing surface tension of the liquid phase). To date, there is limited information about the effect of mucilage from plant roots on the hydraulic properties of soils of different textures.

In this contribution, we aimed to evaluate the effect of plant mucilage in different contents (mucilage extracted from maize roots) on the retention and flow of water in soils with contrasting textures (coarse and fine-textured soils). To this end, soils were mixed with mucilage at different contents (0, 2.5, 5, 7.5 mg dry mucilage per gr dry soil) and were packed in aluminum containers (diameters of 1 cm and height of 8 cm) as follows: the control sandy soil (the content of zero) was packed in the first 4 cm of containers followed by a 1 cm layer of treated soils with mucilage. These containers were equipped with porous plates at the bottom allowing us to drain soil from the bottom by applying suction. In the case of fine-textured soils, a 1 cm layer of treated soils with varying mucilage contents was first saturated with water and then placed on top of a 4 cm layer of dry soil inducing a big suction to dry treated soils. During soil drying, we used a time series neutron radiography technique to monitor soil water content redistribution. We used the profiles of water contents during soil drying with a combination of modeling of water flow within soils (the Richard equation) to inversely estimate the hydraulic properties of soils treated with different mucilage contents.

Our data showed that maize mucilage affects the soil’s hydraulic properties. On the one hand, mucilage exuded by maize roots increased the water-holding capacity of both soils. Mucilage also impacted the hydraulic conductivity of both soils. In general, it decreased soil hydraulic conductivity of soils at the near saturation range, but it prevented a big drop in soil hydraulic conductivity as the soil dried compared to a sharper decrease observed in the control soils. Our findings showed that both effects are mucilage content dependent and the magnitude of the effects is soil texture dependent.