Cover plants as allies

Important in helping to control weeds and pests such as nematodes, cover crops are great allies for the producer. However, it is necessary to make the correct choice for each environment.

In the field, the main tool used for control of weeds lies in the use of herbicides, however, one of the problems faced in management are resistant biotypes, which makes it unfeasible the use of certain herbicides and increases the total production cost by producer. There are several solutions for efficient and profitable management, with integrated management in the production system standing out as the most efficient. Among the possibilities available for control, an option that has been increasingly common is the adoption of intercropped cover crops or succession system in agricultural crops.

Cover plants are those that have the purpose to cover the soil, protecting it against erosion, nutrient losses due to leaching, in addition to being used for grazing, grain and seed production, hay, silage, straw supply for the direct planting system (SPD) and some species have the ability to cycle nutrients.

Due to these attributes, cover crops constitute important allies in the management of weeds, as the accumulation of straw serves as a physical barrier, which in addition to maintaining soil moisture and increase organic matter, suppresses the emergence of weeds, both by impediment to the passage of light as well as the allelopathic effect that makes it difficult to germination, emergence, and establishment in the area through exudates released by decomposing aerial parts or roots.

A adoption of cover crops contributes to improving soil attributes, such as physical, chemical and also biological. The roots of plants coverage disaggregate soil particles, forming micropores that favor distribution of water in the system and are of great importance in the construction of the soil profile. Furthermore, cover crops help control diseases, nematodes and other pests, directly benefiting the crop interest.

Types of Cover Plants

It is important to remember that for each environment, and depending on the successor crop there is a cover plant that suits better, that is, to choose a good cover plant you must take into account takes into account some factors, such as: the plant must be fast and easy to grow establishment, have a deep and vigorous root system to recycle nutrients, not host pests and diseases, offer good soil cover, be a good producer of dry matter, have low cost management and preferably the producer obtains some economic return, such as supply grains or serve for animal grazing in the off-season.

Nonetheless, the adoption of these plants requires care, as there is no cover plant that suits all conditions and offers all the benefits that any systems may require. The choice must take into account the limitations of the area and the characteristics of each species.

A Most plants used for this purpose fall into two families: Legumes (Fabaceae) and Grasses (poaceae). Plants from the family legumes, such as sunn hemp, are important nitrogen fixers atmospheric. And grasses, such as brachiaria and millet, have a vigorous and deep roots, efficient in recycling essential nutrients for the growth and development of plants that will be cultivated in succession.

They can be implemented in consortium with some crops, including corn, coffee and fruit trees, or else be cultivated alone, in the off-season and winter, normally in regions that They do not cultivate grains during these times. Thus, in addition to the benefits already mentioned, prevents the incidence of weeds in the area during the fallow season, and consequently prevents the increase of the seed bank, especially of resistant weeds, thus bringing a positive impact on the crop summer, as the seed bank will be reduced. It is worth remembering that the desiccation of cover crops is much easier and more economical than that of lignified and resistant weeds.

Desiccation management

The desiccation of cover crops and weeds should be carried out approximately 15 to 20 days before planting, due to the various benefits provided, how to break the cycle of pests and diseases; reduce competition for water in beginning of culture development; increase the decomposition of remains cover crops and weeds; improve uniformity of planting; reduce allelopathic effects caused by cover crops and weeds; standardize the stage of weeds to facilitate the application of post-emergent herbicides; promote the control of plants difficult to control and consequently increase productivity.

Types of Cover Plants

• Black oats (Avena strigosa): widely used in grain cultivation, it is a very precocious and rustic, it is resistant to the main pests and therefore is used as a health regenerator, reducing the population of pathogens such as rust and aphid attack, in addition to being used for hay production, silage and feed for both animals and humans. It also produces a high amount of green mass and contributes to the cycling of nutrients. It is a plant widely used to protect the soil during winter. and is an excellent forage.

• Ryegrass: (Lolium multiflorium): has allelopathic compounds that reduce the incidence of weeds, is an important ally against erosion and can be used for animal feed. Also used as forage and straw forming for direct planting, but in some winter crops it is considered a weed, such as wheat. It is often used as cover before crops such as corn and soybeans.

• Grass Brachiaria: brachiaria ruziziensis (Urochloa ruziziensis), brachiaria brizantha (Urochloa brizantha) and brachiaria decumbens (Urochloa decumbens) are the species used as cover plants. They have a high capacity for biomass production, both in the aerial part, providing straw, and in the roots, contributing greatly to the structuring of the soil and incorporation of organic carbon in deeper layers. Its roots form a mesh that hold the surface particles of the soil and protect it from the impact of raindrops, protecting the soil from erosion.

• Crotalaria: (Crotalaria spectabilis) and (Crotalaria juncea): important Nitrogen fixers have high macro and micronutrients, improving the physical and chemical characteristics of the soil, and allies in the control of root-knot and cyst-forming nematodes. They favor loosening the soil and helping to control erosion. are adopted mainly in association with soybeans, corn and cotton. In addition to this, it has great capacity to fix atmospheric nitrogen in the soil, thus contributing for plant fertility and nutrition.

• Millet (Pennisetum glaucum): also used for animal feed, it is a low water requirement plant, with high water cycling capacity nutrients, rapid growth and high biomass production, which contributes to the formation of straw. It is an important ally in controlling pests and nematodes, as it presents resistance, breaking the cycle of reproduction of these parasites.

• Turnip Forage: (Raphanus sativus): widely used for green manure in winter, animal feed and crop rotation, in addition to being an important ally in soil decompression due to its pivoting root system quite deep. It presents high initial growth, with an important effect suppressant on weeds and decomposes quickly, providing nutrients immediately for the next crop.

Cost X benefit

The adoption recurrent use of this technique is partly due to the accessibility of acquiring seeds, whose price does not exceed R$300,00 per hectare. At the beginning of installation, the producer tends to question the investment to be made, incredulous about the return. However, studies show that the practice can result in savings of R$960,00 per hectare with inputs and soil management.

Other commonly reported problem is regarding the management of cover crops, a since current production systems are very much based on a succession of crops (e.g. soybeans/corn). This type of succession clearly indicates the role of cover crops in the diversification and viability of cropping systems production, thus contributing to greater production and in a more sustainable, that is, less susceptible to pest attacks, diseases and less dependent on agricultural inputs.

Applications

Coffee farming x Plants Roof

Increasingly the adoption of cover crops in coffee farming has become a technique consecrated, because they confer great benefits to culture, and consequently ensure greater profitability in cultivation combined with sustainable production.

In coffee farming, water optimization, nutrient cycling, soil decompression, assistance in weed management, biological N fixation (Fabaceae) and increased organic matter are the main benefits associated with its use.

O brachiaria grass is the cover plant most used in vegetable crops. coffee trees,  due to the gains that this grass provides to plants. This system is managed in a way integrated, where chemical control is carried out in the cultivation line, and between the rows Management takes place mechanically, through mowing. In this sense, the remains cultural crops originating from the fields are thrown into the coffee tree line in search of gains with organic matter, improvement in water use, reduction of thermal amplitude of the soil and suppression of weeds, both due to physical, as well as allelopathy.

Plants of cover such as jack beans, mucuna, forage peanuts, sunn hemp, and Forage turnips are also often used as cover crops in the coffee tree, each with its specificities.

Santa Fe System

The Santa Fé system is established in agriculture, where there is an association between corn cultivation and brachiaria grass, so that, after the corn harvest, the grass starts to be used as fodder for grazing.

Challenge of grain production (box)

O Brazil is one of the largest grain producers in the world, it is estimated that its production could exceed 226 million tons in the 2017/2018 harvest, with soybeans and corn responsible for most of the country's production, representing approximately 89%. According to estimates for this year agricultural, soybean production is expected to be around 119,2 million tons and corn 92,2 million tons.

Despite of the large quantity produced, the average grain productivity in Brazil is still is considered low, which occurs due to several factors, among which the soils stand out Brazilians, as they are acidic and poor in organic matter, and farmers of subsistence do not adopt available technologies, which means that reach a low production average.

Furthermore, the failure to adopt management suitable for crop rotation, phytosanitary treatments, plant control weeds and maintenance of soil fertility and mineral nutrition of plants, affect productivity. In relation to weeds, when not managed in a correctly, can cause reductions in growth, development and crop productivity, due to the high capacity to compete with the crop by essential elements available in the environment, such as: water, space, light and nutrients.

Klinger M. Lima Júnior, Lenise Oliveira Coelho, Giovani Belutti Voltolini, Maurício A. de Paula Santos, Artur José Lima Guedes, UFLA

Article published in issue 229 of Cultivar Grandes Culturas, June 2018.