Organic Mulching Boosts Vineyard Soil Biodiversity After Three Years, Spanish Study Finds

Recent research from the Institute of Grapevine and Wine Sciences (ICVV) in Spain has provided new insights into how different agricultural practices affect the microbiota of vineyards. The study, conducted by David Labarga Varona as part of his doctoral thesis at the University of La Rioja, focused on the impact of organic mulching, rootstock selection, and ozonated irrigation water on soil and must microorganisms in vineyards located in the Rioja Denomination of Origin.

The research was carried out between 2019 and 2024 in vineyards situated in Logroño, Aldeanueva de Ebro, and Arenzana de Abajo. Over this period, 246 samples were collected from soil, rhizosphere (the area surrounding vine roots), and grape must. These samples underwent advanced genetic sequencing to identify both the types of microorganisms present and their functions.

One of the main findings relates to the use of organic mulches such as straw, vine prunings, and spent mushroom substrate. According to Labarga, these materials increase soil biodiversity and help prevent long-term soil degradation. However, changes in microbial diversity were only noticeable after three years, suggesting that the benefits are gradual and cumulative. The mulches also contributed to stabilizing soil temperature and moisture levels.

The study also examined five different grapevine rootstocks—1103P, R110, 140Ru, 41B, and 161-49C—under both irrigated and drought conditions. Results showed that irrigation was the primary factor influencing bacterial communities in the rhizosphere. Under drought stress, differences emerged based on rootstock genotype. This indicates that rootstock choice becomes more important when vines face water scarcity, a scenario expected to become more common with climate change. Labarga noted that no single rootstock was universally superior; each had a moderate but distinct effect on rhizosphere microbiota. In stressful conditions, vines appeared to promote specific microbial groups that support adaptation and survival.

In contrast, irrigation with ozonated water did not produce significant changes in soil microorganisms. This raises questions about its value as a sustainable practice from a microbiological perspective.

The research also found that vintage year and vineyard location had a greater influence on bacterial and fungal composition than any of the agricultural practices tested. Despite this, specific effects were observed for some practices, particularly in soil and rhizosphere samples.

This work highlights the complex relationship between vineyard management techniques and microbial communities. It suggests that while some practices like organic mulching can enhance biodiversity over time, others may have limited or context-dependent effects. The findings underscore the importance of considering local conditions and long-term impacts when adopting new agricultural methods in viticulture.