As the human population continues to grow, so has its effect on climate change. The impact of this increased human activity on urban soils has become the focus of researchers to determine if urban soils can be utilised for sustainable plant growth that can alleviate some of the effects of climate change.
Researchers are studying the cycle of nitrogen and carbon in the soil, water, vegetation and air. Urbanisation has hampered this cycle because of the unusual composition of many urban soils, resulting in an alteration of the storage capabilities and the release of nitrogen and carbon. Human activity has introduced industrial wastes such as oil, plastics, and building materials in the surrounding urban soils.
This results in urban soils that may be very acidic or alkalotic, compacted or deeply mixed, covered by tarmac or exposed. These differences can severely alter the cycling process.
Biosolids can offer a sustainable solution for the problems with urban soils because of its nutrient density and other beneficial properties making it ideal as a soil amendment.
Nitrogen is a key component in plant growth that is abundantly found in biosolids. However, there is only a portion of nitrogen that becomes available for plants. This portion is what is called bioavailable nitrogen.
A unique challenge for the biosolids industry is to determine how much nitrogen from different biosolids products become bioavailable when applied to urban soils. This is because these soils degrade in nature which may reduce the nitrogen availability for plants.
Nitrogen rich biosolids are what’s needed to help restore these urban soils. Biosolids are also moisture rich which can help reduce soil compaction. This makes soils easier to till and assists the plant roots to thrive. Biosolids are also able to increase water infiltration and retention in soils, which are beneficial for plant growth.
One of the main challenges faced when applying biosolids to urban areas is their high moisture content. The high moisture content of biosolids can make them more difficult to transport, handle, and spread.
Pure biosolids alone yielded more bioavailable nitrogen than when it was mixed with organic material. Urban soils have low organic matter and a higher clay content which contributed to the reduction of bioavailable nitrogen when the biosolids were applied. This also hampered the means of determining the nitrogen levels that were available.
Researchers are focusing on using a reliable method called the 7-day anaerobic incubation which became the best indicator of biosolids nitrogen availability. Finding the sweet spot for optimal nitrogen levels in degraded urban soils is the key. It is important to adjust biosolids application rates to match the degree of soil degradation. Once experts are able to dial-in on the right method for nitrogen bioavailability determination, the next step would be to develop quick tests that can replicate the results of the study.
In 2019, as much as 60% of biosolids produced by wastewater treatment facilities have been spread on farmland and gardens, as well as schoolyards and lawns in the US. It has been a great source of cheap organic fertilizer in many states.
If you are a municipality in Ontario and in need of a biosolids management solution, please feel free to contact us at 1 (877) 479-1388.