Effect of plant roots on soil strength

Roots of plants have been shown, under some circumstances, to increase soil strength. To test whether this applies to rice-growing soils, a pot experiment was conducted using a soil from East Java, Indonesia, to which a series of puddling-irrigation treatments was applied consistent with rice-growing soils and preparation techniques in the East Java region. Plants were grown in half of the pots. Measurements included the bearing capacity and shear vane resistance of soil 45 and 70 days after emergence, and root weight and plant height at Day 70.

The results showed that in most cases rice roots increased both the bearing capacity and shearing resistance. A linear relationship between bearing capacity and shearing resistance was found, and agreed with published data for dry soils. The implication of the results for traffic in wet soils is discussed.