Nourishing the planet without degrading the quality of soils and crops remains a major challenge for humanity. Among the promising avenues to guarantee food security while preserving natural resources is the use of organic urban waste* to fertilize and enrich soils, especially those damaged by human activities and intensive farming practices. The fertilizing and enriching power** of Organic Waste Products (OWPs)*** varies according to their origin: sewage sludge, biowaste, residual household garbage or animal manure. Veolia and its partner, the French National Institute for Agricultural Research (Inra), have been measuring their effects on soils since 1998.
QualiAgro, a long-term project
Some thirty kilometers to the west of Paris, the QualiAgro project’s 40 experimental plots are spread over 6.5 hectares of loamy agricultural soil. The aims are to assess the agronomic efficiency of urban composts, control their health and environmental quality, and then monitor the evolution of the soils, crops and water. The scheme is deployed in line with a rotation of wheat and corn crops, two food grains that represent major long-standing crops in France. The work follows a protocol. Everything is scrupulously measured and compared according to the origin of the compost tested: the OWPs’ characteristics along with their effects on soils, plants, the water in the soil and the air quality above the plots. Many measurement methods have been implemented to control all these effects and some are permanently installed in the plots (such as lysimeters**** or enclosures for measuring gases).
The first assessment: sludge and biowaste are most effective
After 15 years’ field trials, the first phase of the pilot project (1998-2013) gave its assessment in 2015. Inra notes that “from an agronomic point of view, biowaste and sludge composts prove to be most effective due to their greater stability. […] The yields from spring crops sown immediately after input are similar to those obtained with mineral fertilization alone. However,” the Institute qualifies, “these urban composts lead to concentrations of metals (primarily copper and zinc) in the upper layer of the soil in which they are incorporated.” This input does not particularly change the quality of the soils because, as Inra states, “the concentration readings are similar to those measured in similar soils in the region.”
A second organic-driven phase
“In 2014, a second phase of field trials began, which aligns the experimental scheme with organic farming criteria,” adds Maria Albuquerque (read her interview), the manager for this project at Veolia, “to study the behavior of our composts in this new crop management technique. More precisely, how can we compare organic fertilization via compost input to the effect of an intermediate crop such as alfalfa?”
These new field trials reflect the current changes in farming practices, which are looking to abandon the use of mineral fertilizers and pesticides sooner or later. The adoption of a wide variety of crops goes hand in hand with this goal: a legume — alfalfa — capable of maintaining nitrogen in the soil is inserted into the corn-wheat rotation developed in the previous scheme.
The QualiAgro site is part of a vast national and European network observing the return of OWPs to the soil – SOERE PRO (observation and experimentation system for environmental research into OWPs). It is tasked with assessing the long-term effects of this type of application on soil quality.
The data extracted from these field trials is used by numerous associated multidisciplinary programs (see the figures below), such as QualiAgro’s European partner from 2011 to 2014, ECOSOM. The latter has developed new indicators capable of evaluating the effects of these composts on soil ecosystems (Read the article: Composts are good for the soil). These scientific programs encourage interaction between researchers, representatives of the farming profession, local authorities and Veolia. This long-term work looks to meet the challenges of the future and strike a balance between increasing food needs and protecting our planet’s resources and biodiversity.
A few figures
34 national or international research programs attached to the QualiAgro trial (including 5 underway) since 1998
17 theses on the QualiAgro scheme since 1998
58 articles in 26 different journals since 2007
124 oral presentations at 70 conferences since 2004
*organic urban waste is classified into three categories: organic waste sorted at source, waste from residual household garbage (RHW, waste not sorted at source) and sewage sludge.
** The fertilizing power: capacity to make nutrients for plants available and sustainable; the enriching power improves the properties and physical structure of the soil with an impact on resistance to erosion, a reduction in soil slaking, etc.
*** Organic waste products (OWPs) include non-agricultural waste (sludge from industrial or municipal water treatment plants, biowaste and organic waste from household garbage) and livestock manure (dung). They are repurposed into compost.
**** Device for quantitatively studying the evolution of water in a soil profile.