Wheat Root Growth as Affected by Soil Strength

Soil compaction is a common problem that affects several soil properties and plant growth. In order to assess the effects of soil strength expressed by its mechanical resistance on roots, a growth chamber experiment was conducted at the Universidade Federal do Rio Grande do Sul, Porto Alegre, in 1994, during 35 days (530 GDD, 0oC base temperature) on a typical Paleudult soil. Treatments, using pots arranged in a completely randomized design, consisted of soil compactions that resulted in resistances of 1.0, 2.0, 3.5 and 5.5 MPa. A combination of soil gravimetric moisture and densities was used in order to minimize possible effects due to lack of water and oxygen supply to the roots under the treatments. As soil resistance increased, roots showed a reduced length, surface and dry matter, but a higher radius. As less soil was explored under high resistances, shoot and root dry matter decreased but the latter suffered the most. This study shows that soil mechanical resistance itself, is an important factor restricting plant growth, with its effects being detected very early in the plant development.