Weed management in direct planting

When used correctly the direct planting system is an important ally for producers in managing weed plants. In the presence of straw on the soil acts as a kind of physical barrier, which limits the development of invasives.

Among the many benefits provided by the direct planting system, cultural control is and physical characteristics of weeds depending on the straw input into the system.

The direct planting system is based on sustainable agricultural practices, such as conserving the structure of the soil profile, through straw and dead roots, carbon sequestration, input of organic matter, moisture conservation and lower soil temperature range. Assists to maintain the quality of the next crops, as the fertility and health of the soil are conserved.

There are some principles basics in direct planting, such as reducing soil disturbance as much as possible, keeping it covered with straw in the appropriate quantity, preventing it from being exposed, delimiting movement only in the planting line, controlling the traffic of machines, carry out sowing right after harvest and use different species plants through practices such as crop rotation, succession or intercropping.

The success of the planting system direct, as with conventional, depends on plant control weeds. Before the emergence of herbicides there were some problems in implementation of the system, precisely because of this aspect, as the way of control used until then was through soil preparation and disturbance, which goes against the precept of not moving the earth recommended by the system.

Among the main characteristics of weed plants are adaptability to conditions adverse conditions, which makes them more competitive in the search for water, light and nutrients against crops of agronomic interest. Therefore, it is necessary to manage appropriate, favoring cultivated plants to the detriment of weeds. In addition to reduce crop productivity through competition and allelopathy, Weeds can make harvesting difficult, increase production costs and serve as hosts for pests and diseases.

In the direct planting system, the straw, in addition to changing conditions such as light incidence, thermal amplitude and soil moisture, works as a kind of physical barrier that prevents normal development of weed plants, causing their etiolation, which makes them more fragile, making them easier to control.

In an experiment conducted to evaluate the productivity of soybeans at different levels of infestation weeds, in direct planting system, the results obtained in the areas of “low”, “medium” and “high” infestation showed that soybean productivity was reduced by 73% (low), 82% (medium) and 92,5% (high). It's possible to realize that the reduction in productivity is very high, even when the level of infestation of weeds is considered low. Therefore, it becomes extremely It is important to carry out appropriate management.

Pre-emergence control is considered the most important, because at the beginning of the development cycle of the culture, interference from weeds must be minimal, so that it is maximum development and greater uniformity in the plants, for the perfect closure of the crop canopy, which in itself will control weeds.

In addition to chemical control, through herbicides, it is possible to use some cultural practices to assist in weed control, such as spacing between plants reduced, greater seed density at planting, use of vigorous seeds, in addition to crop rotation and intercropping. The consortium species, during their growth phase, they can excrete allelopathic substances that inhibit the weed growth. Already in its adult phase, shading harms weed plants and, finally, the straw, after desiccation, serves as a physical barrier to invasive plants.

The use of cover crops, capable of releasing allelopathic substances, associated with the straw layer disposed on the soil, together with herbicides, can optimize the efficiency in control of unwanted plants. The integration of these managements can contribute by reducing the use of pesticides, prolong their effect, in addition to making it more efficient. Therefore, integrated management is the most suitable for controlling weeds, as it reduces the chances of resistance emerging against herbicides, in addition to being considered more sustainable management.

Still regarding the methods for Preventing weed resistance to herbicides is of paramount importance perform the rotation of action mechanisms, associated with crop rotation. OK It should be noted that the emergence of resistant plants can lead to difficulties in subsequent management, which may lead to increased use of herbicides

Another experiment showed that mulching significantly reduces the weed population. The authors observed a proportional effect, as the greater the amount of straw in the soil, better weed control. Furthermore, it was also verified that the use of denser straw, with slower decomposition and with allelopathic action, allowed the reduction or even elimination of herbicide application. Therefore the direct planting system can be effective in controlling weeds when applied correctly.

Article published in issue 226 of Cultivar Grandes Culturas, March, 2018.