How Management of Plants on Constructed Rootzones Influences Root Growth and Plant Competition

Constructed root zones provide unique challenges for plant growth in that we often desire to grow species of plants not suited for the conditions of the constructed rootzone. Plant roots evolved to maximize the survival of plants growing in natural soils and often respond in less than desirable ways when grown on constructed rootzones leading to reduced root growth, increased need for foliar fertilization and increased invasion of undesirable species. Nutrient and water availability in sand based rootzones is often limiting requiring frequent applications of both supplemental irrigation and fertilizers. Frequent fertilization events often are applied as foliar fertilizers and there is evidence that this may lead to less desirable shallower rooted species such as annual bluegrass to become more competitive. In addition frequent watering to provide consistent playing conditions on golf course putting greens has created an environment that favors invasive species without roots, leading to an increase in silvery thread moss invasion. The constructed rootzones also may create different nutrient cycling issues within the rootzone that may inhibit the adoption of more environmentally friendly lower impact grasses such as velvet bentgrass by influencing the form of nitrogen available in the rootzone. The inclusion of certain nutritional amendments into the rootzone such as phosphorus bounded to alumina can alter root growth, encouraging deeper root growth. When developing and evaluating constructed rootzones, it is important to evaluate how the management of plants on that root zone may lead to a less competitive environment for the desired species.