Producing more food for a growing world population is a huge challenge. There is no scope for solving these problems by increasing the agricultural land area. Agricultural land is being lost due to urbanization, soil degradation and climate change, and most of the agriculturally valuable land on this earth is already in use. Although agricultural land is increasing in some areas, the total arable land area of the world reached its maximum around 1990 (FAOSTAT) due to these processes. Any attempt to increase agricultural land into areas currently left to nature occur at severe environmental costs, and many developed countries, including Denmark, strive to increase the proportion of land in nature.
As we cannot increase the agricultural area, production has to increase through increased efficiency and intensification of production. Within this picture, we see the increased exploitation of subsoil resources by crops as one of the ways whereby we can increase food production in a sustainable way. It will allow us to increase production without having to add further resources.
Positive impact on environment
The use of deep rooting crops can potentially improve environmental performance and resilience of food production and maintain or even improve agricultural soil quality due to more permanent soil cover and higher organic matter input to the soil. These effects can also contribute to climate change mitigation through increased carbon storage in the soil, including increased storage in deeper soil layers where stored carbon may be more stable.
Limitations of current crops and systems
Current agricultural systems do not utilize subsoils efficiently. The maximum rooting depths of common crops range from 0.5 to 2.5 m, which is much less than the potential rooting depth of many plant species.
One of the main limitations arise from the short life span of crop plants giving them too short a time to develop deep rooting and their maximum rooting depths are only maintained through short periods at the end of the crop growth period.
During most of the year, soil in arable cropping systems is either without crop and without roots or covered by young crop with a shallow rooting.
Adapting cropping systems by inclusion of deep rooted cover crops or by growing more crops with longer growing seasons, may substantially increase the crop exploitation of deeper soil layers.