The effect of stones and gravel on soil hydraulic properties

Abstract

The Canterbury plains are dominated by stony and well-drained areas which are highly drought vulnerable. The soil water storage and water flow characteristics are important for plants surviving in high stone and gravel content soils. Thus, it is necessary to define the effect of stones and gravels on soil hydraulic properties. In this study, saturated hydraulic conductivity and pore-size distribution in different binary mixtures (stones, gravel and mineral soil) was determined to identify the role of stones and gravels on soil hydraulic properties. Repacked binary mixtures with different composition of stones, gravels and mineral soils were collected from Eyrewell forest. Saturated hydraulic conductivity and pore-size distribution were carried out by using the constant head method and an infiltration under different tension. The saturated hydraulic conductivity was largely influenced by the volume loss and the distribution or pores sizes in the mineral soil. Soils with high stone content showed the lower saturated hydraulic conductivity than that in low stone contents. In stony soils, stones blocked the water path and creates a tortuous pathway for water to move through mineral soils only. This suggests the water limiting condition in stony soils is not because of rapid drainage but decrease of mineral soil volume which can capture and store water and the pore size distribution through the mineral soil from which water flows through. This result is meaningful for future water management with different land use on stony soils.