Long-term biosolids land application influences soil health

Authors: IPPOLITO, JAMES - Colorado State University; Ducey, Thomas; DIAZ, KANDIS - Colorado State University; BARBARICK, KEN - Colorado State University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2021
Publication Date: 6/8/2021
Citation: Ippolito, J.A., Ducey, T.F., Diaz, K., Barbarick, K.A. 2021. Long-term biosolids land application influences soil health. Science of the Total Environment. 791. https://doi.org/10.1016/j.scitotenv.2021.148344.
DOI: https://doi.org/10.1016/j.scitotenv.2021.148344

Interpretive Summary: Improvements in soil health via the addition of amendments have mostly focused on looking either at manure or compost application. Biosolids, the nutrient-rich byproduct of the treatment of human sewage, is another source of organic material that can be used for soil improvement. However, biosolid application has been poorly studied in the context of soil health. The purpose of this study was to use a traditional soil health assessment test, measuring a total of eleven soil properties, to evaluate soils treated with biosolids as compared to inorganic nitrogen fertilizer. When analyzed, biosolids increased soil fractions of carbon and plant available nitrogen, both of which indicate soil health was improved by biosolids addition to the soil. These results indicate that the use of biosolids, for long term improvement of dryland agricultural environments may be a suitable practice.

Technical Abstract: Soil health assessments associated with organic amendment applications have primarily focused attention on manure or composts; quantifying specific changes in soil health associated with biosolids land applications has yet to be determined. Our objectives were to evaluate the changes in various soil indicators, and utilizing the Soil Management Assessment Framework, quantify changes in soil indicator scores and soil health indices as affected by either increasing inorganic nitrogen fertilizer (0 up to 112 kilograms nitrogen per hectare) or biosolids (0 up to 11.2 dry megagrams nitrogen per hectare) application rates. Soils were sampled (0 to 20 centimeter depth) following 22 years of nitrogen fertilizer or biosolids inputs to a dryland wheat-fallow (Triticum aestivum L.) rotation, 11 soil health indicators were monitored under Soil Management Assessment Framework guidelines, and indicators, indicator scores, and soil health indices were analyzed statistically. In general, increasing nitrogen fertilizer application rates had little effect on soil indicators, SMAF indicator scores or soil health indices. Increasing biosolids application rates increased soil organic carbon and potentially mineralizable nitrogen. The Soil Management Assessment Framework indicator scores showed upward trends for soil pH, soil organic carbon, potentially mineralizable nitrogen, and microbial biomass carbon associated with increasing biosolids application rates; discussing trends are important as these indicator scores are combined to provide soil health indices. Indeed, increasing biosolids application rates increased soil chemical and biological health indices, leading to an improvement in the overall soil health index. When comparing the overall nitrogen fertilizer to biosolids effect, biosolids applications significantly improved the soil biological health index. Results indicate that long-term biosolids land application to semi-arid, dryland wheat fallow rotations, similar to those studied, improve various aspects of soil health. These findings suggest that biosolids may play a pivotal role in dryland agroecosystem sustainability.