Profitable option: corn-brachiaria consortium

Off-season corn is grown in a peculiar environment, with less water and heat compared to summer corn, which is unfavorable for the growth of grass of tropical origin. Therefore, the biggest challenge is not to suppress the initial growth of grass, but to provide good conditions for its establishment and development. The forage can be grazed in a short period of time (two months, on average) or used as a cover crop. Therefore, the grass cannot produce seeds before management, it needs to cover the area uniformly, be easy to desiccate and provide good performance for the soybean seeder. A Brachiaria ruziziensis is the species that meets all these requirements.

The brachiaria implantation methods that are suitable for most off-season corn environments are simultaneous or with a minimum time lag in relation to corn sowing, whether with seed distribution by broadcast or in the sowing furrow.

Intercropping with an intercrop is the best method when off-season corn is grown with a row spacing of 80cm or 90cm. The machine that sows soybeans is the same one that will be used for off-season corn, with the same spacing between carts. Normally, the producer removes every other row after soybean sowing, leaving the machine prepared for the 80cm to 90cm spacing of the off-season corn. In the case of using the consortium, the producer must keep the rows at 45 cm and use different discs for the grass: in conventional seeders, the 5 mm universal sorghum disc with 50 holes is used and in pneumatic seeders, the 1,2 mm canola disc. 1,5mm to 120mm with XNUMX holes. Only the corn row must be fertilized, and to do so, the fertilizer box outlet must be covered in the row where the forage plant will be sown.

Broadcast distribution is used in crops with reduced spacing and must be done before sowing the corn to allow the seeder-fertilizer machine line mechanisms to incorporate part of the grass seeds. The disadvantages of this method are the greater cost of seeds (at least double compared to the intercropping) and the emergence in reboleiras, depending on the climatic conditions at the time of sowing the second-season corn. Simultaneous distribution can also be done on the seeding line itself, using a corn seeder with a box for grass seeds or adapting the third box in a regional workshop.

 In the case of safrinha corn, the technique of mixing the seeds with the seeding fertilizer is not recommended, as the deep positioning of the fertilizer can delay the emergence of the grass. Mixing the seed with nitrogen fertilizer is also not suitable, as the fertilizer is distributed some time after the corn emerges.

The consortium of off-season corn and forage plants allows, in addition to the diversification of cultivated species, the maximization of nutrient cycling. Approximately 35 kg of potassium (K₂0) per ton of dry mass of the aerial part of the B. ruziziensis which, after desiccation with glyphosate, are quickly mineralized and contribute to the nutrition of soybeans grown in succession, as demonstrated in Figure 1.

 

Care

The correct establishment of the consortium depends on good quality grass seeds. Most forage seeds aim to serve the livestock market which, due to the need for greater volume for broadcast distribution and little impact from the presence of soil and weeds on the formation of pastures, adopts relatively low official standards in seed marketing. The minimum cultural value (VC) for commercialization is 50. The CV is the product between the purity (%) and the germination (%, in tetrazolium) of the seeds. In the case of a consortium, seeds with VC above 70 must be used, which, as they have high levels of germination and purity, are suitable for distribution in the small quantities required in intercropped cultivation, and reduce the chance of contaminating the area with nematodes and plants. weeds. The expenditure of VC 70 seeds in intercropping is approximately 3 kg/ha.

Grass development and suppression with herbicides

 Generally, there is no significant difference in corn grain productivity when comparing intercropped corn and single corn, and the application of herbicides is not necessary to partially suppress grass growth. Likewise, there is no need to increase the nitrogen fertilization of safrinha corn to compensate for possible absorption by the grass. However, when a high population of forage is used, corn hybrids with more erect leaves and/or when the corn sowing season is brought forward (warmer period), grass mass production can be favored, reaching 3,0 t/ ha or more, affecting corn development and productivity. Although these cases are few, the initial development of the grass must be monitored to verify the need for suppression with a subdose of nicussulfuron (up to 100 mL/ha of the commercial product for Brachiaria ruziziensis).

Pest control

 Currently, with the use of transgenic Bt corn, it may be necessary to apply insecticides to control caterpillars specifically in grass, as brachiaria are attacked by the majority of caterpillars.

Soy desiccation and seeding machine

 To ensure the benefits of intercropping on soybean productivity, appropriate desiccation of the grass (approximately two weeks beforehand) and adjustments to the soybean planter (increasing the size and sharpening of the cutting disc, for example) are necessary for uniform distribution and direct contact. of the seeds with the soil (without air pockets).

Consortium rotation

Is recommended avoid the continuous cultivation of the safrinha-brachiaria corn consortium and do not implement it in soils with a high population of Pratylenchus brachyurus because this nematode multiplies in both species. Therefore, the system must be alternated across different plots of the property to maximize the benefits of breaking monoculture. Generally, when brachiaria is cultivated for just one cycle, the increase in organic matter and soil porosity overcomes the possible multiplication of pests and nematodes, which can become a problem if the grass continues to be used in the same area.

 The full article can be found in Cultivar Grandes Culturas edition 190.