Microbes in soil: Degraded land recovery
Nested along the Brazilian Paraná river, beside a 1 195 km2 large dam, flanked by small vegetable plots and much less-small patches of fallow land and sugar cane lies Ilha Solteira. This 30’000 people town began as housing for workers building the Ilha Solteira hydroelectric power plant and dam 45 years ago.
Between 1967 and 1973 topsoil was removed from the neighboring land to construct an embankment dam on the Paraná river. With a capacity of 21.2 km3, this dam feeds the 3’444 megawatt Ilha Solteira hydroelectric plant. The amount of topsoil removed from the land varied, reaching up to 8 m depth in certain areas. A layer of clay forms a film which prevents water infiltration but encourages erosion.
Degraded soil and erosion damage.
The soil which now makes up the surface is at best poor cropping substrate, and at worst, heavily eroded land continuously contributing sediment to local waterways. This degraded soil is an on-going reminder of how decisions on land use can have consequences many years down, and in ways not immediately visible.
The agronomy department at Sao Paolo State University (UNESP) in Ilha Soleira has a research station covering part of this degraded land and has researched on recovering this degraded soil using two locally-sourced organic amendments: ash and macrophytes. Ash is a residue from the burning of cane biomass during sugar cane processing. On another side, macrophytes are aquatic plants that grow spontaneously on the surface of the hydroelectric dam and need to be removed periodically.
To different degrees, recovered soil can be used to farm and grow plants that reduce erosion. It also serves as carbon storage and reduces sediment build-up in rivers. The improved soil and fishing for local farmers increases food security and best uses local resources for food production.
Soil improvements brought by organic amendments in soil like these can take years to build up. During this process, the soil microbial community plays a crucial role. Methods that can quantify the impact of different amendments and practices are necessary to evaluate on-going transformation and support evidence-based management recommendations and ultimately policy development.
Thanks to the Mercator Foundation Ambassador Program, I spent time at Sao Paulo State University, Ihla Solteira, with a colleague from ETH to exchange experiences and teach a course on molecular biology methods applied to soil microbiology.
A part of the workshop was related to soil microbial diversity measures. Higher microorganism biodiversity can provide alternate microorganism composition which in turn can maintain soil functions critical to food security (e.g. plant nutrient supply) in response to disturbances. Thereby the resilience of these processes is increased, and this translates into long-term maintenance of processes essential to food security.
Thaís busy in the lab.
One of the participating students was Thaís Boni, a masters student of Agronomy focusing on Soil Management and Conservation. For her masters thesis she is studying the soil microbial community in the ash and macrophyte restoration site to evaluate soil recovery progress. She had been trying to extract DNA from the soil, however, without much success due to a challenging soil make-up.
As with many of the students, she quickly assumed hands-on responsibility over the lab practical. After discussing approaches to tackle the particularities of her research area and equipped with new experience, she has renewed energy to plow on with her project and become a professional to manage Brazilian land in favor of food security.
In her own words: "The course and the tests that we made were very clear and show us how improve our analyses and comparisons about restoration sites.”
ABOUT THE AUTHOR
Viviana Loaiza is a PhD candidate at ETH Zurich, Switzerland. Her current research focuses on nitrogen cycling in organic cropping systems, although current interests include open access publishing and Swiss hiking/biking trails.
“In and out of the laboratory, we discussed about working with organic amendments in different environmental conditions, reflecting on the factors that influence successful use and brainstorming ideas to overcome limitations. Through this whole experience I grew in awareness of how there are many valid solutions and approaches, but at the same time these must be tailored to specific local circumstances. I am grateful to the Ambassador program for making possible this exchange with Brazilian colleagues.”