Effect of brick sand on the soil water balance in permeable soils

In the course of climate change, the framework conditions for agricultural production will change significantly. The ability of the soil to absorb water quickly and efficiently while at the same time storing as much water as possible for plants to use is a prerequisite for maintaining future agricultural production potential.

The aim of this study was to investigate the application of recycled brick sand in agricultural soils with regard to its water absorption and storage capacity and thus to improve the efficiency of water utilisation. The influence of different precipitation intensities on the water storage capacity was analysed.

In order to determine the influence of brick sand on the soil water balance, an experiment was carried out with nine small lysimeter systems. The lysimeters were all filled with soil samples from a vineyard in eastern Austria, whose soil has a high sand fraction and low clay mineral content. Three lysimeters were used as a reference and contained no brick sand. In three others, a mixture of soil sample and 10 % brick sand was used and in three others a mixture of soil sample and 30 % brick sand was applied. A 3-phase test was then carried out. The first phase was used to set a volumetric water content that was as constant as possible in all samples. The second phase was the simulation of a 10-millimetre precipitation event, followed by the third phase, the simulation of a 20-millimetre precipitation event. During the precipitation simulation, the amount of water corresponding to the precipitation intensity was applied to the lysimeter systems and the volumetric water content of the samples was recorded. Control values were determined using soil moisture sensors.

The results showed that the addition of brick sand enabled the soil to store more water over time than the sample without brick sand. The simulations also showed that the amount of brick sand added made a difference in how the water storage capacity changed. Shortly after the rainfall simulation, the lysimeters with 30 % brick sand were able to store the water better. Towards the end of the precipitation simulation, the difference in stored water between the lysimeters with 30 % brick sand content and those with 10 % brick sand content became smaller, and in the 20 millimetre rainfall simulation, the lysimeters with 10 % brick sand content stored more water from halfway through the observation period. The results showed that the use of brick sand as a measure to improve the soil water balance has a high potential, however, the amount of brick sand applied must be adapted to the soil to be treated. These adjustments concern parameters such as grain size distribution and pore distribution, as these have a decisive influence on the water storage capacity.