Autumnal weed management is a practice that aims to control weeds in the interval between the harvest of the summer crop and the sowing of the subsequent winter crop. With the aim of reducing the incidence of weeds in the area, desiccation during this period will reduce problems with species that may arise and hinder the emergence of the winter crop.
In recent years, weeds have been representing a large part of the problems related to yield and productivity in crops, mainly due to competition for water and nutrients with commercial crops, in addition to being potential hosts of pests and diseases that may attack the crop. culture.
For the autumn period, there are several herbicide options that can be used to control weeds. Since there is no established culture, it is not necessary to worry about the selectivity of herbicides. In addition, it also reduces the umbrella effect, which limits the arrival of products to the lowest and youngest plants. An example of this would be the species Trapoeraba (Commelia sp.) and Poaia (Richardia brasiliensis), which grow closer to the ground and would be difficult to control with an established culture.
In post-harvest soybeans, grasses such as bitter grass (Digitaria insularis) and donkey's tail grass (Andropogon bicornis), both perennial weeds, have their favored control. In this way, they end up being cut by the harvester and begin their regrowth period, the new leaf tissue to be formed will have a less thick cuticle, which increases the absorption of herbicides and increases the level of control of these species.
An allied management between desiccation and pre-emergence makes all the difference for the control of species with a large number of seed banks in the soil, such as horseweed (Conyza sp.) and ryegrass (Lolium multiflorum Lam.). This will appease the occurrence of these weeds during the development of wheat or other winter crops to be sown.
Cover crops are also a great option to reduce the incidence of weeds, in addition to providing nutrient cycling in the soil and protection against erosion. It is important to use cover crops with good biomass production.
When to start management?
Between the months of April and June is the ideal time to manage the weeds left over from the summer crop and those that will appear. It is recommended that in colder regions desiccation be carried out at least 30 days before planting.
The ideal way to reduce the incidence and reduce the seed bank is to carry out applications rotating mechanisms of action, this will hinder the incidence of tolerant or resistant weeds in the crop. It is noteworthy that the more advanced the development stage of the weed, the more difficult it will be to control. For this reason, weed management during the autumn period becomes an important control strategy, since most of them will still be in their initial phase, facilitating herbicide translocation, which is greater in young plants.
Which herbicides to use?
Autumn management makes it possible to use herbicides with different modes of action, such as, for example, herbicides that inhibit the enzyme EPSPs, which act by preventing the synthesis of certain essential amino acids for plant growth. In addition, the application of herbicides that inhibit the enzyme Glutamine Synthetase (GS) in the nitrogen assimilation route is also indicated.
Other herbicides that can also be used are those that mimic auxins, a natural compound that regulates plant growth, thus products that affect growth, leading to the alteration of stems and leaves.
Herbicides that inhibit the ACCase enzyme, responsible for the biosynthesis of fatty acids, are also indicated for the autumn management of weeds.
In view of this, it is concluded that autumn management is extremely important to contain weeds, due to the possibilities that this management has, such as the chance to use herbicides with different modes of action, in addition to the use of cover crops, which also bring numerous benefits to the soil.
Text written by Amanda Vitória Mariani and Eduarda Rotilli Antonow, members of AGR Jr. Agronomic Consultancy, Junior Company of the Agronomy Course at UFSM Campus Frederico Westphalen, under the guidance of professor Gizelli Moiano de Paula.
Imagem de capa: reprodução internet
