On Climate Change Adaptation: SOIL Research Updates
As the devastating impacts of climate change continue to mount around us, especially in vulnerable frontline communities like the ones SOIL serves in Haiti, we’re more motivated than ever to grow SOIL’s climate-positive sanitation solution, which transforms a public health crisis facing cities around the world into a restorative solution for the planet. Visit this page to learn about how SOIL's regenerative sanitation service mitigates the impacts of climate change.
Scientists and land managers have discovered that compost can help mitigate climate change by enhancing the ability of ecosystems to pull carbon dioxide from the atmosphere and store it in the soil as organic carbon. Compost may also help agricultural ecosystems adapt to the impacts of climate change by buffering against drought and flooding, and by helping plants use nutrients more efficiently. SOIL's research partner Dr. Rebecca Ryals and her students, Kate Porterfield and Stephen Heisey, designed and conducted an experiment to explore how using SOIL’s compost as fertilizer impacts soil and crop health. They hypothesized that amending soils with the compost would boost yields and reduce nutrient losses by improving soil conditions and acting as a slow-release fertilizer compared to alternative fertilization practices.
How did they test this idea? With radishes! Six consecutive crops of radishes were grown in nutrient-poor tropical soil that was fertilized one time only with either SOIL’s compost, biosolids (the solid residue from wastewater treatment plants), a commercially available liquid bio-fertilizer, or synthetic fertilizer (urea). There was also a control group that received no fertilizer at all. They measured crop yields, water retention, nutrient loss via leaching, crop nutrients, and soil greenhouse gas emissions using specialized pots designed to capture nutrient flows in and out of crop systems. While much of the data analysis for this experiment is still ongoing, they already have some exciting results to share with the SOIL community.
Radishes grown in soils amended with SOIL’s compost produced larger crop yields than those grown in soils fertilized with the synthetic fertilizer, urea.
Increased Agricultural Yield
As we’ve seen in other studies, Dr. Ryals’ team found that fertilizers made from treated human waste demonstrated greater soil health and fertility benefits than synthetic fertilizer (urea) as well as compared to no fertilizer at all. In the first cropping cycle, SOIL’s compost increased crop yields 15-fold compared to no fertilization and nearly 3-fold compared to synthetic fertilizer. By the second cropping cycle, crop yields in the synthetic fertilizer treatment fell abruptly and were similar to those that received no fertilizer at all. This finding suggests that agricultural systems that use synthetic fertilizer depend on its use year after to year to sustain crop yields. In contrast, soil amended with SOIL’s compost – just once – maintained higher crop yields throughout the six cropping cycles of the experiment. This beneficial legacy is due in part to the nutrients in the compost that slowly release over time, and also due to the improvements in soil conditions that support healthy plant growth.
Radishes grown with SOIL’s compost are more productive than those grown with the same amount of plant available nitrogen in the form of urea, which is the most common synthetic fertilizer used around the world today. SOIL's organic compost has a long lasting positive impact on crop yields, even after only one application.
Building More Resilient Soil
SOIL’s compost also had other measurable benefits. Soil water retention increased, with compost-amended soils leaching less than half the amount of water compared to the other fertilizers. As the intensity of flooding and droughts is rapidly increasing in climate vulnerable nations like Haiti, the ability for the soil to store more water is critical.
One other exciting finding? The research team documented that radishes grown in organic fertilizers did not have elevated heavy metal concentrations, which can be a concern for crops fertilized with human waste.
Soils amended with SOIL’s compost lost the least amount of water through leaching, especially compared to inorganic fertilizer. Compost improved the structure of soil, allowing it to retain water more effectively and making more of it available for plant growth.
These findings suggest that transforming human waste into organic soil amendments can be an effective and safe strategy for improving soil health, tightening nutrient cycles, and promoting crop production that is more resilient to impacts from climate change.
As SOIL works to develop data-driven sanitation systems in Haiti that nurture human and planetary health, we want to extend our many thanks to our brilliant research partners at UC-Merced for their support in making this possible.