2026-06-29
A study released by the Spanish wine publication Acenología says soil biology, accumulated water stress and winter cane reserves are becoming central tools for vineyards trying to adapt to hotter and drier growing conditions, with early findings from Godello vineyards in Valdeorras pointing to sharp differences from parcel to parcel.
The work, published June 26, follows a project led by Bodega Rafael Palacios with Laboratorios Excell Ibérica focused on 13 vineyard parcels planted to Godello in northwestern Spain. The aim is to adjust both vineyard management and winemaking to future climate conditions while preserving grape quality and reducing reliance on phytosanitary products. The project combines soil microbiology, plant nutrition analysis, water stress monitoring and precision irrigation.
The backdrop is familiar across many wine regions. Rising temperatures, tighter water supplies and shifts in fermentation conditions are putting pressure on growers and wineries. In Valdeorras, where Godello is one of the region’s defining white grapes, the question is not only how to keep vines alive through dry periods, but how to maintain the balance needed for premium wines.
Researchers measured total microbial DNA and ATPase activity in vineyard soils in March, June, September and December 2025 to assess both the abundance of microorganisms and their metabolic activity. They also analyzed winter canes in January 2025 and February 2026 for macro- and micronutrients, starch and carbon reserves. Water stress was tracked through carbon isotope analysis, using δ13C values in grapes collected at harvest as an integrated measure of stress during ripening.
According to the report, the first soil readings from March 2025 showed wide variation among the 13 parcels. Valdagua stood out with both high microbial load and high biological vitality, posting 25 micrograms of DNA per gram of soil and 1,279 nanograms of ATP per gram. As Lamelas, Chandoiro, Chao do Couso and Poulo do Cabo also showed relatively high microbial loads. At the other end, Souto Vello, A Venta, Mourela Nueva and A Barca had microbial DNA levels below 10 micrograms per gram.
When researchers looked at biological vitality rather than microbial quantity alone, some parcels shifted position. A Barca had low microbial load at 4.9 micrograms of DNA per gram but high vitality at 692 nanograms of ATP per gram, suggesting a smaller but highly active microbial community. O Soro Vello, Souto Vello, Valverde Alejos and A Venta showed low metabolic activity below 300 nanograms of ATP per gram, which the report says may be linked to water stress, soil compaction or past use of crop protection products.
That distinction matters because the study argues that functional activity in the soil may be more useful than simple microbial abundance when judging biological fertility and resilience under drought. Over the course of 2025, repeated measurements showed strong swings in both microbial load and activity. Several parcels declined after the initial reading and then recovered after six to nine months. The report says this pattern points to a soil microbiome that responds quickly to irrigation, temperature and moisture changes and can reorganize after management shifts.
The authors say water availability appears to have played a decisive role in those changes. In some periods, higher biological activity suggested favorable moisture and temperature conditions. Later declines in certain parcels pointed to possible episodes of water stress or soil limitations. By the second half of the year, several sites showed signs of stabilization or recovery.
The cane analyses added another layer. In samples taken during winter dormancy, researchers found generally sound organic parameters across parcels but recurring deficiencies in calcium, boron, zinc and sodium. They also found slight excesses of manganese and potassium in many sites. Carbon reserves varied notably. Colas Arriba, A Barca and Coalleira Riego had some of the highest reserve levels, while Mourela Xoven, As Lamelas and Poulo do Cabo were among the lowest.
Low reserve levels matter because they can weaken early growth in the following season. The report says parcels such as Mourela Xoven may need earlier spring irrigation to avoid stress that could further reduce vigor at budbreak. It also identified nutritional imbalances that could affect grape quality and drought tolerance, including low nitrogen-to-potassium ratios in parcels such as Valverde Alejos and A Venta, a sign that excess potassium may be interfering with magnesium and calcium uptake.
Among the parcels flagged for stronger intervention, Valverde Alejos showed very low total nitrogen in the first cane analysis along with a very low N/K ratio. Mourela Xoven combined very low carbon reserves with elevated manganese levels, which the report links to acidic soils and oxidative stress. Based on those findings, researchers proposed corrective fertigation with calcium and boron in some parcels, ammonium nitrate before flowering in Valverde Alejos and removal of external potassium and manganese inputs where those elements were already excessive.
Comparing winter cane data from early 2025 with samples taken in February 2026, the study found a broader pattern of reduced soluble carbohydrates across most parcels. That usually signals vines that ended the season more depleted or exposed to heat or water stress late in the cycle. Some parcels increased starch reserves, including Colas Arriba, Chandoiro, Poulo do Cabo and especially Mourela Xoven. In Mourela Xoven, total carbohydrate reserves rose from 7.91% dry matter to 13.34%, while starch increased from 3.21% to 7.78%, suggesting a strong physiological recovery.
Other parcels appeared more strained. Valdagua showed a marked drop in total carbohydrate reserves from 12.41% dry matter to 10.43%, with limited starch accumulation. Colas Arriba and Chandoiro increased starch but lost soluble carbohydrates sharply, which may mean reserves became less readily available for early growth. The report says this kind of profile can lead to slower or less even budbreak if spring conditions are cool.
On mineral nutrition, nitrogen reserves rose across all parcels between the two winters, in some cases sharply. Chandoiro increased from 0.36% dry matter to 0.81%, Valdagua from 0.48% to 0.83% and As Lamelas from 0.44% to 0.81%. The report interprets that as evidence that vines stored nitrogen efficiently after the 2025 season, which should support early shoot growth and protein synthesis in the next crop.
But phosphorus remained low in most parcels, while potassium accumulation was weak in several sites including Colas Arriba, Valdagua and Souto Vello. Magnesium also slipped slightly overall. Researchers say that combination suggests not simply a fertilizer shortage but weaker physiological functioning after harvest in 2025, with lower accumulation of energy reserves and nutrients tied to metabolism.
Micronutrient trends were mixed. Boron fell broadly across parcels, raising concern because it plays a role in fertility and sugar transport. Zinc accumulation was stronger in some sites including A Barca, O Soro Vello and Coaxeilla, which may reflect better physiological performance during growth. Manganese dropped sharply in several parcels including Poulo do Cabo, Mourela and O Soro Vello. Iron rose strongly in Chandoiro, Poulo do Cabo and Coaxeilla, which could point either to greater soil availability or improved uptake by vines.
The practical goal of the project is not only diagnosis but prioritization. By using δ13C readings at harvest as an accumulated measure of vine water stress during ripening, researchers hope to identify which parcels should receive maintenance irrigation first and build a historical record for each site that can later be linked with grape quality data.
That has direct implications for wine producers beyond this one estate. If growers can identify where biological soil activity supports resilience under drought, where nutrient imbalances are limiting vine performance and where post-harvest reserves are falling short, they may be able to target irrigation and nutrition more precisely instead of applying broad treatments across an entire vineyard. For wineries that depend on consistent fruit composition for premium white wines such as Godello, that could affect both quality stability and production costs as climate pressure grows.
The study presents itself as part of a broader effort to adapt Galician viticulture sustainably to climate change through parcel-level management rather than uniform responses across an estate. Its early results suggest that neighboring vineyard blocks can behave very differently under heat and water pressure, making detailed monitoring of soils and vine reserves increasingly important for future harvest planning.