Shear Strength of Soil-Root Layer Formed on Degraded Soil Supplemented with New Zeolite Substrate

The aim of the study was to determine the shear strength of the soil-root layer obtained as a result of growth of cocksfoot (Dactylis glomerata L.) on degraded soil enriched with the addition of a new zeolite substrate Z-ion. Measurement of shear strength for soil-root layers formed as a result of growth of a grass species (on degraded soil alone and on degraded soil with added Z-ion) was performed in a direct shear apparatus. The measurement results allowed determining parameters of equations describing the dependence of shear strength of studied soil-root layers on normal stress e.g. cohesion and internal friction coefficient. Under the experimental conditions, application of 1% v/v substrate addition to degraded soil induced development of cocksfoot root system which resulted in the significantly increased cohesion of soil-root layer (by 30%) as compared to that formed on degraded soil alone. The enhanced cohesion of the soil-root layer formed on soil enriched with Z-ion resulted in its significantly increased shear strength as compared to that of soil-root layer obtained on soil alone. Further research using higher doses of the Z-ion substrate (greater than 1% v/v) is needed to obtain the information at what dose ranges of the substrate one can expect even more intensive development of plant root systems and, consequently, further significant improvement in the shear strength of the soil-root layers.