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April 12, 2012

Alternative Crop Rotation Available for Farmers in Central Brazil

Farmers in Brazil continue to be concerned about increasing disease and pest pressures resulting from the monocrop production of soybeans. Without the incorporation of different crop rotations, the amount of diseases and pests continues to increase on their soybeans. On the disease side, the biggest concern is soybean rust, which is potentially a devastating disease if not controlled properly. As far as pests are concerned, nematodes have emerged as a significant problem for Brazilian soybean production. These microscopic worms are very difficult to control and they are becoming a major soybean pest in Brazil. Both of these concerns could be addressed by the incorporation of a more varied crop rotation pattern. One such proposed rotation would be planting a first crop of rice followed by a second crop of dry beans.

Rice and dry beans are the two basic staples of the Brazilian diet, but traditionally they have been grown in primarily southern Brazil and not in the more tropical regions of central Brazil. Agronomists from Agro Norte have developed varieties of rice and dry beans that they feel are well suited for production in northern Mato Grosso.

Their proposed crop rotation involves planting a crop of rain-fed rice in early October after the rainy season has started. They feel their best rice variety is Cambara and if the weather cooperates, the rice can yield as much as 5,500 kg/ha. This rice variety matures in 105 days so it would be ready for harvest in early January. Immediately after the rice is harvested, a second crop of dry beans would be planted. They recommend planting IPR 139, which matures in 90 days, so the dry beans would mature before the rainy season ends and it would be ready to harvest in May.

The dry beans would be no-tilled into the rice stubble which offers several advantages. First of all, leaving the crop residue in place is the very best way to prevent soil erosion. An additional advantage of the crop reside is that it could help prevent fungal diseases from attacking the dry beans. By keeping the residue in place, it prevents soil from being splashed onto the developing pods during the heavy tropical rains. Various fungi found in the soil are a primary source of diseases for dry beans, so if the soil does not come into contact with the pods, it can help prevent a lot of potential problems.

Other long-term advantages of this alternative crop rotation are that it helps to break the cycle of soybean diseases and pests. Pests and diseases in central Brazil do not encounter cold winter temperatures like they do in the United States, so they can flourish year-round making them more difficult to control. The best way to control them is to plant non-host crops such as rice or dry beans. Other advantages of this alternative crop rotation would include: improved soil fertility, improved physical characteristics of the soil, better utilization of equipment and labor since harvesting would occur generally at times when soybeans or corn would not be harvested.