Soybean productivity increases up to 20% in a consortium of grass with sunn hemp

Research by Embrapa Agropecuária Oeste (MS) carried out in six municipalities in Mato Grosso do Sul, and validated by rural producers, shows that the consortium of forage grasses with sunn hemp (cover legumes) results in an increase in productivity of up to 20% in cultivation of soy. Furthermore, it increases the quantity and quality of biomass produced by plants and promotes biological nitrogen fixation (BNF) in the soil, combining economic and environmental advantages.

The inclusion of legumes in the system is also an alternative for straw production and, in the case of sunn hemp (depending on the species), there is the possibility of grazing in integrated systems. “FBN, provided by legumes, positively impacts production costs in the medium term”, says researcher Rodrigo Arroyo Garcia.

The sunn hemp used in the research were C. juncea, C. ochroleuca e C. spectabilis. Forage grasses were the Brachiaria ruziziensis, Brachiaria brizantha (cv. Xaraés) and Panicum maximum (Tamani and Zuri cultivars).

Another advantage was the significant production of biomass for a consortium production system, exceeding 7 thousand kilos per hectare (kg/ha) in the off-season, close to around 8 thousand kg/ha for single grass. In addition to quantity, the quality of biomass is also relevant. In some experiments, sunn hemp contributed more than 2 tons per hectare in about a hundred days.

According to researcher Luís Armando Zago Machado, the data were obtained in production systems with different purposes and different edaphoclimatic conditions, “from plots of pasture renewal and implementation of integrated systems, to areas with a long history of soy/corn cultivation”, he explains. .

The six municipalities where the experiments were carried out were: Dourados, Naviraí, Rio Brilhante, Nova Andradina, Vicentina and Ponta Porã. “In Dourados, Naviraí and Rio Brilhante, the consortium of forage grass with sunn hemp was an alternative for diversifying the grain production system in the soybean off-season. In other municipalities, the consortium was an additional practice for the renewal of pastures”, adds analyst Gessí Ceccon.

System implementation

“The process of implementing the consortium is the most important stage for the technology to add benefits to the production system, with positive aspects coming from both species”, assures Garcia.

In intercropping, legume seeds are distributed in one row and grass seeds in another. The best option, as researchers warn, is to broadcast the grass and sow sunn hemp afterwards. When implementing on the same line, the C. ochroleuca, as it is made up of smaller seeds, “which favors the uniformity of the mixture with the grass seeds and the distribution in the sowing furrows”, explains Zago.

Another factor to be observed by the rural producer is the quantity of seeds to be used. When the objective is straw production, half the amount recommended for the single species can be used. If there is an intention to graze the area, the amount of C. ochroleuca ou C. juncea can be reduced considerably, to around 25% of the recommendation for single cultivation. According to Garcia, “this is very important so that the legume does not compromise the establishment of forage grass, as grass is a priority and will remain in the area for longer.”

In the municipalities where the Crop-Livestock Integration (ILP) system was implemented, biomass production was lower than in traditional crop areas, however Zago explains that “plant sampling was carried out in advance, as grazing followed. Furthermore, the chemical conditions of the soil were not ideal, as the correction had recently been carried out.”

Species combination

The producer must pay attention to the use of quality seeds. In the case of legumes, seeds with low vigor “result in plants dominated by grass in the initial stages, making intercropping unfeasible”, says Ceccon. Garcia explains that sunn hemp are short-day species, so the later these legumes are sown in the off-season, the lower the potential for biomass production.

The choice of species for cultivation depends on the objective. A C. spectabilis It is not recommended for grazing, as it is toxic to livestock. In the case of nematodes, there is a great difference between sunn hemp species. “In general, C. spectabilis presents greater efficiency, followed by C. ochroleuca and the C. juncea. In turn, the C. spectabilis it is more susceptible to white mold”, ponders Zago.

Soybean implantation

During the off-season, the animals control the forage by trampling or feeding. A C. ochroleuca and C. juncea They have a low regrowth capacity, which makes it easier to plant soybeans in succession. Zago draws attention to intercropping cultivation aimed solely at producing biomass in the soybean off-season, “because the excessive growth of forage crops, such as some cultivars of Brizantha and Panicum, can make their implementation difficult.”

To control the growth of the forage and avoid the production of legume seeds, the recommendation is to mechanically prune the aerial part, using a brush cutter, triton or knife roller, around one hundred days after sowing.

The researchers state that “the existing machinery and technologies already adopted by the rural producer, regardless of the size of the property and level of investment, are adequate, and any small adjustments make it possible to use the consortium in the production areas evaluated in Mato Grosso do Sul” .

Producers prove good results

The technical manager of Grupo Agropecuária Palmares, Franklyn Guimarães, says that the Group has been working with agriculture for over 30 years, in the region of São Gabriel do Oeste, MS, and in Itiquira, MT. In total, there are four properties of 8.500 hectares, 2.500 hectares, 2.200 hectares, and 1.400 hectares.

In São Gabriel do Oeste, before the introduction of research by Embrapa Agropecuária Oeste, the production system used was a succession of soy/corn, and soy/brachiaria. Currently, the consortium between Crotalaria Jjuncea e Crotalaria Oochroleuca on Brachiaria ruziziensis It is adopted on 700 hectares in the off-season.

According to Guimarães, in 2022 the first harvest was planted with Embrapa technology, but it has already been possible to observe good results in improving the soil, with the contribution of nitrogen by FBN. “The partial results of the technological solution point to a tendency to increase the area in the next soybean harvest. I recommend it to other producers,” he emphasizes.