SOIL CARE
Soil management is of great importance to grapevine cultivation as a means of avoiding competition between other plants and vines. The physical properties of the soil and its fertility must also be respected, as well as the natural balance of the vineyard ecosystem.
Each vineyard ecosystem determines the most appropriate management approach; site slope, soil fertility, water availability, and vine vigor are some of the determining factors.
Two soil conservation measures should be considered. One is herbaceous ground cover and it protects vineyard soils from erosion during the high-rainfall autumn– winter period; it may consist of either spontaneous or sown vegetation. The other is called minimum soil tillage; it reduces compaction, using mowing equipment in the inter-row during spring–summer.
Cover cropping is a sustainable method of weed control, promoting the balance of the soil–vine relationship, while also reducing water water loss through evapotranspiration during summer, promoting natural enemy populations, and providing alternative resources for predatory insects.
Cover cropping may be temporary (annual seedings) or permanent, consisting of spontaneous vegetation or sown legumes, grasses, or mixtures. The recommended period for seeding is early fall, with the first rains, and the most commonly used species are clovers, serradellas, and lupins among legumes, and ryegrasses, fescues, bentgrasses, and orchardgrass among grasses. Commercial mixtures are also available, depending on soil conditions and specific objectives.
During spring, the seeded or non-seeded vegetation should be cut. During summer, it dries out and self-seeds.
Weeds in the vineyard can be controlled through soil tillage, both in the inter-row areas and within the rows.
Tillage that incorporates weeds into the soil can be achieved by passing a shovel cultivator, rotary tiller, or disk harrow through the inter-row area. Between rows, an under-vine cultivator must be used (with a disk harrow or rotary tiller) equipped with a sensor that retracts when approaching the vines.
Repeated mechanical tillage can sometimes cause soil to accumulate around the vine trunks along the rows—which may be beneficial for protecting vine base in cold regions. However, it then necessitates the leveling of the soil surface with a vineyard plow.
A shallow central furrow may be made in the inter-row area for annual corrections and fertilization.
Inter-row control
The alternating use of tillage and cover crops in the inter-row areas is becoming increasingly common. Alternate inter-row areas are tilled and covered with vegetation in alternating years ("zebra effect”). Thus,the advantages of tillage are combined with those of cover cropping. Tillage facilitates the incorporation of fertilizers and manure, increases soil fertility by incorporating vegetation, improves soil aeration, avoids competition with vines for water and nutrients, and destroys sources of disease, such as downy mildew. Cover cropping, on the other hand, improves soil structure, facilitates machinery traffic, and, when legumes are included, provides sources of nitrogen through atmospheric nitrogen fixation and phosphorus via the decomposition of adventitious roots. It also provides habitat for natural enemies that limit pests such as scale insects, leafhoppers, and grape berry moths. The advantages and disadvantages of these techniques make it necessary to combine their use in a rational way.
Inter-row control
During the annual growth cycle, the row must be kept free of weeds, and the most common method of controlling them is using an under-vine cultivator. For smaller areas, weed control within the row can be often carried out using a brush cutter, providing that extreme operator care is given.
For younger vineyards, weed control within the row can also be carried out by applying biodegradable plastic during the first two years.
Inter-row control vs. in-row control
Given the options above, and always taking into account the rainfall regime of this region—wet springs and hot summers—the most advisable approach is a combined system of maintaining controlled cover cropping (natural or sown) in the inter-row areas and applying herbicide within the row.
On the other hand, if the soil is poor and results in low vine vigor, with little risk of erosion and no possibility of irrigation, the recommended approach is to carry out tillage during spring–summer to avoid vine competition, while maintaining natural cover crops during fall–winter and applying herbicide within the row.
If the soil is rich, the vines are vigorous, there is a risk of erosion, and irrigation is available, the best option is permanent cover cropping, with herbicide application within the row.
The application of herbicides for weed control in the vineyard requires certain precautions, including the following:
● Application should be based on the spray volume per hectare, taking into account the type of nozzles used and the soil vegetation cover (dominant weeds).
● Application should occur at the appropriate time, namely during the early stages of weed development; if the vines have already started budbreak, watershoots on the trunk should be removed before applying systemic herbicides.
● Application should always be carried out at low spray volumes, avoiding drift or product runoff onto the soil, and ensuring uniform distribution.
● Application should take place in dry, warm weather and under calm conditions.
Weeds are a major vineyard threat as they consistently cause significant losses through intense competition with vines for both water and soil nutrients, particularly during critical periods of vegetative growth. This competition results, on one hand, in reduced growth of young vines and, on the other, in reduced yield and production quality.
Given the soil and climate conditions of this region, weeds in vineyards are particularly harmful because they contribute to an overly humid and shaded canopy microclimate, which favors the development of diseases such as gray mold, downy and powdery mildew. They may also, in some cases, serve as hosts for pests, such as tetranychid mites and other polyphagous pests, such as the grapevine moth.
The species that compete most strongly with vines are spring–summer annuals, some biennial species, and perennial species that spread through rhizomes, stolons, and bulbs.
