The experiment was established at Legado Winery in Campo Largo, Paraná, Brazil, a region characterized by a humid subtropical climate and high-altitude conditions. The vineyard, planted with Viognier vines grafted onto P1103 rootstock, was divided into five treatments designed to compare spontaneous vegetation managed with or without herbicides against various sown cover crop systems. The treatments included spontaneous vegetation with herbicide application, spontaneous vegetation without herbicide, and three distinct sown systems involving single species or multi-species mixtures of grasses, legumes, and other functional plants. The study spanned the 2023/24, 2024/25, and 2025/26 growing seasons, allowing researchers to assess the consistency of responses under varying meteorological conditions.

Researchers measured a comprehensive suite of variables, including cover crop dry biomass, macronutrient accumulation, soil chemical and physical properties, and grapevine physiological and productive traits. The results demonstrated that sown cover crops, particularly those involving common vetch and mombaça grass or multi-species mixtures, produced substantially more biomass than spontaneous vegetation. These sown systems accumulated higher levels of nitrogen, phosphorus, potassium, calcium, and magnesium in their biomass, indicating a greater capacity for nutrient capture and recycling. The increased residue inputs were associated with measurable changes in surface soil properties, including higher total organic carbon, total nitrogen, and cation exchange capacity, as well as lower bulk density in certain treatments.

Despite these positive soil responses, the grapevines did not exhibit corresponding increases in canopy development or yield across the three-season average. Total leaf area and the ratio of yield to leaf area remained statistically similar among all treatments, suggesting that the additional nutrient inputs did not stimulate vegetative growth or improve productive efficiency per unit of leaf area. While physiological parameters such as net photosynthesis and carboxylation efficiency showed treatment-dependent responses, with some sown systems outperforming the herbicide-treated control, these physiological advantages did not consistently result in higher fruit production. The lack of a direct causal link between soil improvements and yield highlights the complexity of the soil-plant system in perennial crops.

Interannual variability played a significant role in the observed outcomes, with the most pronounced yield differences occurring in the 2025/26 season. In that year, treatments maintaining spontaneous vegetation without herbicide and those using vetch and mombaça grass reached yields of approximately 11.06 and 11.12 megagrams per hectare, respectively, which was about 20% higher than the herbicide-treated spontaneous vegetation. However, this specific seasonal response does not reflect the overall trend of the three-year study, where no consistent yield advantage was observed for any single management strategy. The variability underscores the importance of climatic factors, such as precipitation and temperature, in modulating the effects of vegetation management on grapevine performance.

The study also highlighted the importance of distinguishing between the effects of herbicide use and the presence of continuous vegetation cover. The treatment involving spontaneous vegetation without herbicide performed comparably to the sown cover crops in terms of grapevine productivity, despite producing less biomass and accumulating fewer nutrients. This suggests that the mere maintenance of living vegetation may be sufficient to sustain grapevine performance without the need for diversified sown species. The herbicide-treated control, which involved the suppression of vegetation within the vine row, generally showed lower yields and less favorable soil properties, although the specific contribution of herbicide cessation versus vegetation cover could not be fully isolated in this experimental design.

Fruit technological maturity was largely unaffected by vegetation management, with soluble solids and pH remaining stable across all treatments. Titratable acidity showed some variation, but these differences were not consistent across the three growing seasons. The stability of these quality parameters indicates that the different floor management strategies did not compromise the basic chemical composition of the grapes, which is a critical consideration for wine production. The findings indicate that cover crop systems can improve soil health and ecosystem services without risking the fundamental quality attributes of the fruit, provided that the vegetative-productive balance of the vines is maintained.

The authors emphasize that the translation of soil changes into grapevine responses may occur over longer time scales than the three-year period evaluated in this study. Perennial crops like grapevines may require several seasons for the cumulative effects of improved soil structure and nutrient cycling to manifest as consistent changes in yield and stability. Furthermore, the study was limited to the top 10 centimeters of soil, whereas mature grapevines can explore a much deeper soil volume, meaning that the measured surface changes may not fully represent the conditions experienced by the root system. Future research should extend the duration of such trials and incorporate deeper soil layers and direct measurements of soil temperature and water dynamics to better understand the long-term implications of cover crop management.

In conclusion, the study provides evidence that sown cover crops are effective in enhancing soil quality and nutrient cycling in subtropical vineyards, but these benefits do not automatically lead to increased grape production. The decoupling of soil health indicators from yield suggests that vineyard-floor management should be evaluated based on multiple criteria, including soil functioning, ecosystem services, and long-term sustainability, rather than short-term yield alone. The results support the agronomic feasibility of herbicide-free vegetation management and highlight the need for a nuanced approach to cover crop adoption, where the selection of species and management practices is tailored to local environmental conditions and long-term sustainability goals.

Subject of Research: Effects of cover crop management on soil properties and grapevine performance in a subtropical vineyard

Article Title: Cover crop management influences soil properties and grapevine performance across three growing seasons in a subtropical vineyard

Article References: Teixeira-Loss, M. B., da Rosa Dutra, B., Costa, F. W., Goedel, A. D., Carniel de Oliveira, M. G., Zimmermann, C. M., Botelho de Souza, M. E., Tokushima, A. E., Feuser dos Santos, L., Ferreira, G. W., Marcon Filho, J. L., Loss, A., & Brighenti, A. F. (2026). Cover crop management influences soil properties and grapevine performance across three growing seasons in a subtropical vineyard. Frontiers in Environmental Science, 14, Article 1895755. https://doi.org/10.3389/fenvs.2026.1895755

Image Credits: AI Generated

DOI: 10.3389/fenvs.2026.1895755

Keywords: cover crops, viticulture, soil health, Viognier, subtropical agriculture, nutrient cycling, herbicide management, grapevine yield, Cover, crop, management, influences

The analytical backbone of the study was a modified QuEChERS extraction procedure coupled with ultra-high performance liquid chromatography tandem mass spectrometry, a combination that allows trace-level quantification of multiple pesticide residues across chemically distinct matrices. This approach matters because herbicides behave very differently depending on where they end up. Some dissolve readily into water and travel with runoff; others bind to soil particles and hitch a ride on eroded sediment. By sampling soil, sediment, and water simultaneously and repeatedly across wet, dry, and transitional seasons, the team could trace those partitioning behaviors in a real watershed rather than inferring them from laboratory models alone.

One compound dominated the picture: diuron. This phenylurea herbicide, widely used to control weeds in orchards and cane fields, was detected frequently, with soil concentrations ranging from 0.309 to 175.406 micrograms per kilogram and sediment values reaching 91.292 micrograms per kilogram. Diuron’s persistence is well documented in other systems; it degrades slowly, adsorbs to organic matter, and can linger long after application. Its prominence in both soil and sediment of the Nala watershed suggests a reservoir of legacy and ongoing inputs that continues to feed the aquatic system, even between spraying seasons.

In the water column itself, the headline compounds were different. Ametryn, a triazine herbicide used heavily in sugarcane cultivation, reached a maximum concentration of 30.294 micrograms per liter in surface water, while mesotrione, a triketone herbicide, peaked at 20.264 micrograms per liter. These are striking figures for ambient surface waters, and they reflect the intensity of herbicide use in a watershed where sugarcane and other subtropical crops receive multiple applications per growing cycle. The fact that the dominant compounds shift between matrices underscores a central theme of the study: there is no single herbicide problem, but rather a suite of compound-specific contamination patterns.

The seasonal dynamics proved equally revealing, and somewhat counterintuitive. In soil, the predominant herbicides, particularly diuron and ametryn, showed significantly elevated concentrations in spring, which aligns neatly with pre-planting and early-season weed control. Yet in sediment, the predominant herbicides displayed no significant seasonal differences at all, hinting at a buffered, slowly exchanging pool that accumulates residues over time. Surface water told a third story: several compounds varied significantly across seasons, but the patterns diverged by compound. Butachlor, a chloroacetanilide used in paddy and wetland systems, reached its highest median concentration in summer, while ametryn and mesotrione showed their numerical maxima in spring.

Those contrasting temporal signatures allowed the researchers to disentangle two forces that shape pesticide fate in agricultural catchments. Application timing clearly controls the initial pulse of herbicides entering the environment, which explains the spring peaks in soil and in compounds applied early in the season. But once residues are mobilized, rainfall and hydrological processes take over, governing transport, redistribution, and dilution across the watershed. The summer peak of butachlor, a compound associated with flooded rice systems, likely reflects both its use pattern and the intense monsoon-season runoff that flushes it from fields into streams. In effect, the watershed integrates a chemical calendar written by farmers with a hydrological calendar written by the climate.

Space mattered as much as time. Higher residue levels clustered primarily in the southwestern agricultural areas of the watershed, where cultivation intensity is greatest, while downstream redistribution became evident during the rainy season as runoff carried dissolved and particle-bound herbicides toward lower reaches. This spatial structure has practical implications: it identifies hotspot zones where mitigation efforts, such as vegetated buffer strips, controlled drainage, or adjusted application schedules, would deliver the greatest reduction in downstream loading. It also demonstrates that a watershed cannot be managed as a uniform unit; pollution pathways are dictated by the geography of farming and the connectivity of the drainage network.

The ecological risk assessment is where the study’s findings become most alarming. Using the risk quotient approach, which compares measured environmental concentrations to toxicity thresholds for aquatic organisms, the team identified diuron, ametryn, and imazapic as the principal risk drivers in surface water. Maximum risk quotients reached 1251.23 for diuron, 841.50 for ametryn, and 789.20 for imazapic, values that are orders of magnitude above the threshold of 1 typically used to flag unacceptable risk. More concerning still, the median risk quotients for these three compounds remained above 1, meaning that at typical, not just extreme, concentrations, the water poses sustained ecological concern throughout much of the year.

The risk landscape beyond the top three drivers was more nuanced. Several additional herbicides also exhibited median risk quotients greater than 1, though at lower magnitudes, indicating chronic pressure from a broader suite of compounds. Others showed high maximum risk quotients but lower medians, a pattern the authors interpret as episodic risk, where brief pulses after rainfall or application events push concentrations past toxic thresholds even if average levels appear tolerable. Episodic exposure is ecologically significant because aquatic communities often respond to peak concentrations, and short pulses during sensitive life stages, such as larval development, can cause disproportionate harm. A monitoring program that samples infrequently would miss exactly these events, which is why the monthly resolution of this study is methodologically important.

What emerges from the Nala watershed is a systems-level insight: herbicide occurrence, transport, and ecological risk in subtropical agricultural regions are jointly governed by agricultural practices, compound-specific environmental behavior, and hydrological processes. None of these factors can be addressed in isolation. The authors position their work as a scientific basis for targeted herbicide monitoring, runoff control, and watershed-based pollution management, and the data support concrete interventions, from timing applications to avoid pre-monsoon windows to prioritizing the southwestern hotspot zones for best-management practices. As herbicide use intensifies across the subtropical belt to feed growing populations, studies like this one provide the evidence base needed to keep crop protection from becoming waterway contamination, and they make clear that in intensively farmed watersheds, the two are currently separated by a very thin line.

Subject of Research: Occurrence, seasonal and spatial distribution, and aquatic ecological risk of sixteen current-use herbicides in a subtropical agricultural watershed in South China

Article Title: Occurrence, spatiotemporal distribution, and risk assessment of herbicides in a subtropical agricultural watershed

Article References: Liu, L., Mo, G., Zhao, Y., Rasheed, U., Li, Y., Hu, M., Qin, Q., Qin, Y., Tan, H., & Shan, B. (2026). Occurrence, spatiotemporal distribution, and risk assessment of herbicides in a subtropical agricultural watershed. Environmental Monitoring and Assessment, 198(10), Article 1094. https://doi.org/10.1007/s10661-026-15948-0

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15948-0

Keywords: herbicides, diuron, ametryn, imazapic, butachlor, mesotrione, agricultural runoff, watershed, ecological risk assessment, risk quotient, surface water contamination, subtropical agriculture