Soil strength and root growth relationships depend on both soil and plant properties. Soil physical properties can be manipulated through mechanical, chemical, and biological methods to create an environment suitable for plant root growth. Each plant species has its own root growth characteristics, which can be substantially modified by the plant’s environment. The penetrating ability of roots also varies among plant species, with sods and perennial plants having a greater ameliorative effect on soils developing layers of high strength. Strategic selection of one or more physical, chemical, or biological manipulation system allows cropping systems to be adapted to site-specific conditions. Although soil modification practices have been used for centuries, we still lack sufficient understanding of the specific effects of a given practice on soil properties and subsequent root growth. Most studies have assessed soil modification effects on aboveground plant growth. This approach has not always uncovered the cause-effect relationship of the observed plant response. The lack of integrated studies stems from the complex and dynamic nature of the plant-soil interface. When explaining plant-environment relationships, factors to consider include details about specific tillage and management practices, plant growth stage, root competition, immediate plant microclimate, rooting zone depth, and adequacy of soil physical, chemical, and microbiological conditions throughout the soil profile. Soil strength has been found to be a function of bulk density, soil water content, texture, organic matter content, and the presence or absence of cementing agents. Recent approaches have emphasized nondestructive methods of measuring temporal changes in root growth as related to changes in soil physical, chemical, and biological properties.