European Agricultural Fund for Rural Development (EAFRD) agreement No. 24-00-C0LA1602-000006
Project partners are LSFRI "Silava" (leading partner), AF "Andrupēni" and AF "Ķiburi".
Total funding of Project is 99,413.93 EUR.
The enrichment of degraded organic soils with organic matter enhances soil health, promotes the development of macrofauna, mesofauna, and microbiota, and improves soil fertility and biodiversity. Perennial crops and plantations not only provide economic returns but also enhance soil structure, increase organic matter content, and reduce erosion. Leguminous crops established between tree rows further improve soil fertility, fix nitrogen, and increase carbon sequestration; however, their effectiveness depends on species selection, soil conditions, and environmental factors.
This study aims to establish both legume monocultures and polycultures, considering variations in morphological traits and the benefits of multi-species mixtures. These include more efficient atmospheric nitrogen (N2) fixation over the long term, increased biodiversity of soil and aboveground fauna, improved nutrient and water utilization, and greater resistance to diseases and pathogens. Optimizing legume growth conditions can enhance their productivity and nitrogen fixation potential. A minimal fertilization dose may improve plant vitality and yield while increasing nitrogen fixation capacity. However, fertilization strategies must be adapted to minimize nutrient leaching and maintain nutrient balance. Organic soil amendments contribute to higher soil organic matter content, greater soil biodiversity, and a gradual release of nutrients, reducing their loss to the environment.
This study will assess the impact of a soil amendment—biogas fermentation residue (digestate)—on legume productivity and nitrogen fixation potential, as it has been previously shown to improve soil quality in both annual and perennial cropping systems. Digestate is a promising amendment that supports circular economy principles, yet nitrogen-containing amendments may also increase greenhouse gas (GHG) emissions, particularly N2O. To better understand the interactions between legume crops and organic soil amendments in carbon and nitrogen cycling, a controlled environment experiment with automated GHG emission measurements will complement the field study. The project will evaluate legume cultivation within tree-based agricultural systems from an agronomic, ecological, and biogeochemical perspective. Data collection will include plant physiological and morphological parameters, soil fauna diversity, soil physicochemical properties, and GHG emissions measures.