The challenge in cotton farming is to raise awareness among producers about crop rotation, say researchers from Embrapa

Three researchers from Embrapa Agropecuária Oeste were part of the program at the 14th Brazilian Cotton Congress, held from September 3 to 5, 2024, in Fortaleza, CE. Researcher Fernando Mendes Lamas (pictured, left) has been participating in the event for many years, being one of the members of the Scientific Committee and, this year, he was also the moderator of a Hub for debates; Júlio Cesar Salton (pictured, center) gave the lecture “Physical attributes x growth and development of plants”; and Guilherme Lafourcade Asmus (pictured, right) gave a lecture on “Increased occurrence and damage caused by Rotylenchulus reniformis and the evolution of Meloidogyne in cotton”.

Lamas said that one of the challenges in cotton farming is the soybean-cotton model, which is practically a monoculture. “Rural producers need to be aware that crop rotation is extremely important, whether with corn or any other crop, including service plants such as brachiaria, crotalaria and others in the system.”

He explains that the Scientific Committee organized the Congress program by highlighting crop rotation, as it is an important technique for controlling diseases, weeds, pests and nematodes. “This topic took up a significant amount of space in all of our discussions.” The issue of cotton plant physiology, especially in light of climate change, was another topic that the Scientific Committee emphasized in the program. “Cotton is a plant with low photosynthetic efficiency, and its physical productivity is reduced when there is heat or water stress. For this reason, these were also topics that were addressed during the Congress,” said Lamas.

In Salton’s lecture, he showed how the capacity of the “soil system” provides conditions for plants to tolerate adverse weather conditions such as dry spells when there is permanent coverage of the soil surface, soil with good structure, large and stable aggregates and continuous porosity. “The results are a higher rate of water infiltration, lower evaporation loss, greater water storage and supply and lower temperature and thermal amplitude,” he said.

In experiments on soils on farms in Mato Grosso do Sul (municipalities of Dourados, Naviraí, Ponta Porâ, Chapadão do Sul and Selvíria), with high, medium and low amounts of clay in the soil, regardless of the type of soil, all converged to the same result: “For rural producers to have quality soil, considering the physical aspect, they need to have the input of organic material, which is the fuel for biological activity and, with that, the improvement of the physical quality, the quality of the soil structure. We then measured this in various environments”, said Salton, who conducted experiments in Conventional Planting (PC), Permanent Pasture (PP), Direct Planting (PD), Crop-Livestock Integration (ILP), always having the worst result in Conventional Planting.

Regarding the occurrence of nematodes, researcher Asmus said that there are a number of crop options to diversify the production system, which includes cotton, as well as a number of grasses, such as forage, corn and sorghum. “The most important thing is for the rural producer and technician to know which nematodes are present on their property in order to make the best choice of crops,” warned the researcher.

The characteristics of infested areas are clayey soils, good fertility, monoculture areas, larger than usual reboleiras and fertility/compaction problems. According to Asmus, producers sometimes have difficulty managing the system, firstly because they only manage it for a short period of time, for example, rotating crops for only one year.

“In a short period, there may not be a satisfactory result, because the nematode, like the Rotylenchulus reniformis (Rr), for example, has high persistence in the soil, and medium to long-term actions are necessary", he explained. Another point is regarding the extension of the area in which management should be carried out in large areas and not localized, because the nematodes are distributed more evenly throughout the area.

He reminds us that all measures must be taken to manage nematodes, that is, crop rotation, good nutritional balance and, eventually, soil seed treatments with products, whether chemical or biological.