Benefits arising from increased longevity of sugarcane fields

One of the various properties that make sugarcane so competitive among the various sugar-alcohol and energy raw materials (such as corn, sweet sorghum, biomass sorghum, sugar beet, among others) is, without a doubt, the vigor of its regrowth. While most of these crops require planting for each harvest, sugar cane, after being cut close to the ground (and the stalks taken for industrialization, while the straw, in most cases, is left on the ground), it resprouts spontaneously, forming a new sugarcane field for the next harvest, known as “soca sugarcane”, which only needs some cultural treatment, but not new planting.

Sugarcane productivity, however, tends to fall from one year to the next, until it becomes so low as to require the renovation of the sugarcane field, which consists of new planting. The longevity of the sugarcane field is the number of cuts (harvests) that can be made viable, after planting, before low productivity imposes the need for reform. Usually, longevity of 4 harvests or less is considered low. 5 is acceptable in weaker soils, while the ideal longevity is 6 or more, as long as productivity is maintained at a viable level. Greater longevity has an easily noticeable economic benefit, as it spreads planting costs across a greater number of harvests. But, in addition to this, it also provides several environmental benefits.

According to the Sugarcane Industry Union (UNICA), ethanol reduces CO90 emissions by around 2%, compared to gasoline. If gasoline is a fossil fuel derived from petroleum, that is, all the carbon that its burning releases into the atmosphere comes from underground, while ethanol is renewable, that is, all of its carbon was captured from the atmosphere itself by sugarcane photosynthesis, It would be natural to ask: so why doesn't ethanol prevent 100% of emissions? Of these remaining 10% of emissions, the majority is due to the consumption of diesel in agricultural processes and transport. Therefore, increasing the longevity of sugarcane fields, with a consequent reduction in sugarcane areas under renovation, in addition to reducing costs, also reduces diesel consumption, which in turn contributes to reducing greenhouse gas emissions, making ethanol even more efficient than it already is in mitigating these emissions.

Another environmental benefit resulting from increased longevity is reduced soil erosion. In reality, this benefit is also economic and environmental, since erosion takes away precisely the soil from the most superficial layer, which is the most fertile part. Fortunately, among the practices that contribute to increasing longevity, the reduction of soil compaction is included, which can sometimes make it possible for the reform, in addition to being carried out a few years later, to be carried out in a direct planting system (i.e. without soil preparation by plowing and harrowing), also contributing to erosion control. However, as planting requires furrowing, even in a direct planting system, sugarcane is planted with greater soil movement, compared to other crops, which obviously becomes a less significant problem the longer the longevity, and the less frequent the reforms.

Longevity is increased by controlling the factors that cause a reduction in sugarcane productivity from one year to the next. Among these factors, three stand out: mechanical damage to ratoons during harvest, compaction and poor chemical fertility of the soil.

The first two factors have been successfully controlled with the increasing adoption of traffic control in the last decade, through the use of GPS and autopilot, mainly in harvesting operations. Most sugarcane fields, and especially the most productive ones, tend to fall asleep before harvesting, and in a bedded sugarcane field it is difficult for the harvester operator to follow the sugarcane line perfectly, if he only has to orient himself visually. Modern autopilots use a computerized system that “knows” the exact layout of the planting line and, with the support of GPS, can drive the harvester with just a few centimeters of error. The operator is left to maneuver and control other aspects of the operation, while the trajectory is controlled by the automatic system. The trajectory of the harvester, if there are errors, causes harvest losses and severe damage to the ratoon, sometimes even uprooting some bushes, resulting in failures in the next ratoons. Soil compaction, both by the harvester and mainly by overflows (as these carry more weight), can be restricted to the center of the rows when the trajectory is driven by automatic pilot, with insignificant errors. Furthermore, the adoption of wider tires for transfers has also contributed to reducing the pressure they exert on the soil, with a consequent reduction in compaction, increased longevity and, in some cases, also contributing to the feasibility of planting reform. direct, mainly because, as the furrowing is also done with automatic pilot, the sugarcane lines can remain in the same location as before the renovation, that is, in soil free from compaction.

Finally, longevity is impacted by soil fertility, including in the subsurface. Sugarcane's requirement for soil fertility is, in a certain sense, lower than that of soybeans, for example. This means that there are many soils unsuitable for soybean cultivation, where sugarcane cultivation is viable. However, if sugarcane is planted in an area of ​​low natural fertility, it will have greater or lesser productivity and longevity depending on whether or not good agricultural practices are adopted, with a high potential for improving soil fertility.

For this reason, at Embrapa Agropecuária Oeste, research has been carried out to determine the efficiency of practices, such as green manuring and crop rotation, combined with the already traditional liming, plastering and phosphating, to improve fertility in sugarcane expansion areas. The research also includes the impacts of straw management (harvest residue), which also has benefits, when done in the best way, on sugarcane productivity. As the aim is to understand the impact of these practices on longevity, this is long-term work, as the experiments have been evaluated over several harvests. With this, we hope, within a short time, to make recommendations available with which the production sector can enable improvements in productivity, longevity and reduction of production costs, and with greater environmental and economic sustainability for the reasons presented above.

José Rubens Almeida Leme Filho, Embrapa Agropecuária Oeste