Agri-environmental management

The significant growth in sugarcane production in Brazil in recent decades has determined important changes in terms of the agro-environmental aspect. The figures for the sugarcane sector are impressive due to the large extent of the cultivated area. Sugarcane currently occupies around nine million hectares of land, equivalent to 1,6% of Brazil's cultivated land, characterizing a production system that has special economic and social significance for the country. A survey of the supply of sugar cane in the world, referring to the period 1990-2000, consolidates Brazil and India as production leaders. The country produces around 370 million tons of sugarcane per year, which is equivalent to 27% of world production. Over the last five years, the market has consistently grown by 10% per year, thus requiring strategic planning and technology changes to ensure high productivity, competitiveness and harmony with environmental issues. On average, 55% of Brazilian sugarcane is converted into alcohol and 45% into sugar. Foreign exchange earnings vary between 1,5 billion and 1,8 billion dollars per year, representing around 3,5% of total Brazilian exports.

São Paulo is the largest producer with an area of ​​approximately 4,5 million hectares, involving more than 350 municipalities that are considered sugarcane producers. This activity directly employed 235 thousand workers in the 99/2000 harvest and around 80 thousand in the sugar, alcohol and spirit agribusiness, totaling 315 thousand people employed in this activity. In 2014, only areas with high slopes (greater than 12%) will be harvested manually. In the São João do Rio Preto region, 70% of the cutting is mechanized, and in the Ribeirão Preto region, sugarcane harvesting without fire straw was around 60%. Soil conservation is still a concern in the study of Terraces embedded and inverted in soils, whose profile has a sharp gradient of clay in its composition from Horizon B, just below (50cm) the surface, forming the characteristic profile of Argisols, predominant in the northern region of São Paulo, with very high productivity, such as in the region of Catanduva, Olímpia.

Sugarcane cultivation is quite complex, with four to six cuts being able to be obtained from a single planting, with good productivity, and after each cycle high investments must be made so that the renewal of the sugarcane field provides good productivity for the next harvest. . Among these investments is the cost of pesticides to control insect pests and weeds, which can cause some injuries. These products can increase the cost of cultivation, have a prolonged persistence in the environment, can eliminate significant parts of populations of beneficial organisms and can also be carried by rainwater, through the leaching process, to water sources. Currently, both the scientific community and civil society have been concerned about environmental issues and the preservation of life on the planet. Thus, the perspective of organic cultivation of sugar cane crops arises. However, under the guidance of a specialist in the field, this practice can be minimized in relation to the harmful effects on the environment. This has led producers to adapt agricultural activity to an action that is environmentally correct and economically viable, increasing the search for alternative methods to chemical control, thus opening up a great opportunity for the implementation of research with biological control agents.

Furthermore, energy sugarcane is very important in today's context when it comes to bioenergy, or phytomass productivity, with sugarcane with a higher fiber content, thanks to the Genetic Improvement Program of IAC/Ribeirão Preto, São Paulo, where The Sugarcane Center is located, work is being done to increase productivity and sucrose content as well. With crop rotation, such as soybeans, sunn hemp, peanuts, sunflower and even corn, spending on pesticides can be minimized and sugarcane cultivation can be even more valued.

Soil preparation aims to improve physical and chemical properties to ensure sprouting, root growth and crop establishment. As sugarcane cultivation is highly mechanized, it is expected that around three dozen operations take place in the same field over the course of five years. It is inevitable that the soil is more compacted over the years in the sugarcane field, especially when the water content in the soil is not observed. Sugarcane plantation renovation takes place, on average, every five years, but, depending on productivity, it can be postponed to seven, eight or more years. There are examples of Eutroferric Red Latosol, which had nine cuts in the Ribeirão Preto region with good productivity. Therefore, soil preparation is then a fleeting issue in the plant's cultural treatments, as the next opportunity will take a few years, even determining the longevity of the sugarcane field. In other words, if any inappropriate practice is adopted, the resulting problems will remain for a long time and the consequences will take effect. Therefore, the water content, the time to enter with the implements and the grain size of the soil (texture) are some aspects that must be observed.

All stages of soil preparation are important. Soil correction practices such as liming, plastering and phosphating, which will provide good conditions for root growth, weed control, furrowing-fertilization operations, seedling preparation, among others, contribute to the success of planting , the establishment and productivity of the crop.

However, it is known that soil disturbance greatly increases its oxygenation, also increasing microbial activity, with consequent losses of carbon to the atmosphere and the loss of soil organic matter and nutrients to water sources, which can eutrophicate them, even increasing the population of aquatic plants in the watercourses, which reduces their flow, contributing to the compromise of these sources and even generating siltation of their beds.

However, direct planting and minimum cultivation techniques, when possible and indicated, increase the contribution of sugarcane cultivation to environmental issues, by reducing carbon losses to the atmosphere, causing the carbon that was "mitigated" from the atmosphere through sugarcane, during photosynthesis, is stored in the soil compartment. Such techniques also contribute to increasing this stock, by not burning the sugarcane before harvesting and maintaining phytomass in cover in the field. In addition, there are reports that just leaving straw on the surface will contribute to this mitigation, and it is worth noting that what should actually be accounted for is the balance, that is, the difference between what was emitted and what was drained.

Click here to read the article in issue 178 of Cultivar Grandes Culturas.