How to maintain productivity in grain farming

The concept of technology in agriculture is often confused with the use of modern machines, cultivar releases and pesticides. But the use of inputs needs to be complemented by the correct management of environmental resources to maximize grain production. The adoption of technologies aimed at soil restructuring has guaranteed producers peace of mind even in drought years. 

In Brazil, the area managed with direct planting system, even with limitations, is 32 million hectares. In Rio Grande do Sul, cultivation of annual grain-producing species is present in 7,57 million hectares, with the direct planting system requiring adjustments, but present in 90% of the area. In summer, soybean cultivation predominates, with 5,69 million hectares, making up more than 75,2% of the grain producing area. In winter, grain production is 1,03 million hectares, which represents only 13,6% of the cultivated area. Adding grain production to the area cultivated with green manures or cover crops, there are still around 5,68 million hectares remaining, that is, 75% of the area under cultivation of annual grain-producing species remains in winter fallow, with only of spontaneous plants, such as oats and ryegrass.  

The most harmful effect of adopting this production matrix or production model, according to Embrapa Trigo researcher José Eloir Denardin, is the degradation of the soil structure, which makes it difficult or prevents plant roots from accessing nutrients, even when applied of technically indicated doses of corrective agents and fertilizers. This fact, according to the researcher, results in increased production costs and reduced income, as investment does not translate into productivity. “It is important to highlight that the degradation of the soil structure does not allow the roots to deepen, does not allow the flow of water, air and nutrients between the soil layers, turning a few days without rain (7 to 10 days) into a deficiency , a drought scenario, with loss of productivity and profitability”, says Denardin.

Another problem is associated with liming applied to soils with a low organic matter content, resulting from the low contribution of crop residues to the soil. In this condition, the soil compaction process is accelerated. “Lime, applied to the surface of soils with a low organic matter content, normally raises the soil pH to values ​​above 6,5. As a result, the clay separates from the other soil particles and is dragged from the surface to the subsurface of the soil, obstructing the pores of the subsurface layer, reducing the rate of water infiltration, increasing water erosion and anticipating the symptoms of water deficit in the soil. plants”, explains Denardin.

In southern Brazil, soil compaction is responsible for loss of productivity in three out of every ten harvests. Hence the importance of expanding the use of conservation practices capable of reducing or eliminating compaction, in addition to increasing the flow of water, air, nutrients and roots in the soil profile. 

Solutions highlighted by the research

Through mechanical and vegetative processes it is possible to reverse soil degradation and compaction. This is what the results of research conducted by Embrapa in the Southern Region show, in partnership with research, rural extension and technical assistance institutions.

For three years (harvests 2017/18, 2018/19 and 2019/20), technological reference units were monitored in more than 100 municipalities in Rio Grande do Sul, Santa Catarina and Paraná. Some results were impressive: soybean productivity under strong water stress was 3.458 kg/ha, three times higher than the average for surrounding crops; wheat yield under severe water stress was between 36% and 45% higher; and the water infiltration rate into the soil was 92 mm/h in the area where mechanical and crop diversification practices were combined, while in an area without these practices, the infiltration rate was 13 mm/h. 

The mechanical process of soil decompression is based on scarification, which consists of breaking the compacted layer using motorized equipment that operates at a depth slightly greater than the lower limit of the compacted layer. 

The vegetative process of soil decompression is associated with the development of plant roots, whose root system is sufficiently vigorous, aggressive, intense and thick to penetrate and break the compacted layer, leaving, after death and decomposition, macropores in the soil. “The use of plants with high-density, thick, thin roots that decompose slowly constitutes an essential complement to the mechanical action of decompression, since the roots will occupy the spaces resulting from the rupture of the compacted layer”, explains the Head of Transfer of Embrapa Trigo Technology, Jorge Lemainski. The best options are summer grasses such as corn, sudan grass, millet or sorghum, followed by winter grasses such as rye, white oats, black oats, triticale, wheat and barley.

Producer experience

With his life dedicated to grain production in Santo Ângelo, in the northwest region of Rio Grande do Sul, Jorge Dezen always prioritized the formation of straw for direct planting, even so, he felt the progressive drop in crop yield even with the increase in investment in inputs: “We were always worried about making straw on top of the land, but we didn't care about what was happening below, until we felt the negative effects on our pockets.” 

Despite following the municipality's productivity average, Jorge Dezen always believed that the results could be better. It was with the support of his daughter, Márcia Dezen, an extension worker at Emater/RS-Ascar, that the revolution in farming began. Several trenches were dug to assess the soil profile on the 540-hectare property, checking the severity and depth of compaction that limited yields. After corrections based on the analysis, planning began for the most agronomically efficient species, but without compromising the financial result. In the 2018/2019 harvest, the departure of soybeans was followed by corn, which covered the soil for approximately 60 days, when it was dried for sowing oats, returning with soybeans in the summer. The producer celebrates the results: “The average soybean productivity in the municipality was 24 bags per hectare, but there was a neighbor harvesting 10 bags. Here (on the property) I closed with 43 bags of average”, says Jorge Dezen, who invested in sudan grass in this year's soil cover and is already planning to try sorghum next autumn, practicing crop diversification.

The succession of crops, soybeans in the summer and wheat in the winter, was also reducing the grain yield on Alisson Padoim's property. “We believed that just maintaining the cover in winter was enough to take care of the soil, but when I saw it in the trench in the area where I was planting it was easy to understand why it wasn't producing as much as it used to.” The producer invested in corn to cover the soil, sown on the same day he harvested the soybeans, in April 2019: “I bought grains from a neighbor and my cover cost 40 reais per hectare, an amount that certainly returned in the soybeans that it came after wheat”, says Alisson. Last harvest, soybean yields were between 40 bags per hectare in the area under recovery and 25 bags per hectare in the rest of the area, but the producer's expectation is to expand soil improvement throughout the property and obtain even greater results in the long term : “Corn has already contributed well to loosening the soil. With the soybean harvest, we were still able to see residues of corn and wheat straw from the previous year, showing that, even with this summer's heat, the soil was unable to decompose all the straw and roots, maintaining good coverage and humidity in the area . The tendency is for the results to be even better in the next harvests.”

With the results of the project, new producers have already approached the Emater/RS-Ascar office in Santo Ângelo to be part of the soil conservation group: “The year of drought in soybeans helped to show the results of the soil structuring work with the use of summer grasses. The permanent cover, with no void between the soybean exit and the wheat entry, was enough to control erosion in the worked areas, a result that, added to the production of roots and organic matter, showed the potential of conservation practices to resume productivity in grain farming”, assesses agronomist Márcia Dezen.