The benefits of trees in urban areas are now well established, with urban greening high on the agenda for councils across Australia. Of course, enabling trees to thrive in cities has always been challenging, with hardscaping, underground infrastructure, overhead obstacles, and pollution to contend with.

Another challenge that is only now emerging is the importance of good quality soil, and enough of it. Warwick Savvas writes, “Urbanisation historically involves a process of removing topsoil and replacing it with sub-soil and concrete. Sub-soil does not have the necessary chemical and physical properties to support plant growth. Plants need the correct structure to not only physically support them, but also allow essential biological processes to occur.

This includes air gaps in the soil, sufficient availability of water, and the presence of minerals. Healthy soils also need to have organic matter and other elements such as nitrogen and phosphorus to provide nutrients for growth. Then there are the active microbial constituents of top soil. These are the fungi and other living biological creatures that synergistically interact in the soil with the plants to enable exchanges between the soil, water, nutrients, and roots. Sub-soil does not have these properties and will not support plant growth.”

Recent research conducted by Tree Preservation Australia concluded that the standard specified topsoil does not have all the necessary properties to promote healthy trees. Furthermore, soil health is deteriorating further because of compaction, low moisture, toxicity, pollution, and root zones devoid of microbiology.

Matthew Daniel, of Tree Preservation Australia, believes we need to take a new approach to urban soils, stating, “Plants play a pivotal role providing energy to the microbial life in the soil and indirectly to all other life forms. The soil‐plant root associations are based on the complex interactions of uncountable microbes. Each go to ensuring the plant can continue its important role of maintaining healthy growth to then in return provide the nourishment the soil biological network needs to flourish.”

Considerations include enough microbes in the soil, balancing the correct ratios of air space, water, minerals, and organic matter, and lastly ensuring that trees are not planted too closely together.

Daniel concludes, “Understanding and better managing soil and plant microbiology represents a powerful tool which people can learn to apply to great advantage in building healthier soils, plants, animals, people and landscapes.”

To find out more about urban soil solutions, click here.

Source: Sourceable

Image Source: Cornmeal Parade