How much sugarcane trash should be left on the soil?

Abstract

How much sugarcane trash should be left on the soil? Large amounts of crop residues are preserved when sugarcane is harvested mechanically, without previous burning. When all this started, many problems associated with trash (or straw, treated here as synonyms) preservation emerged. Later, it was realized that this residue is a valuable asset for both energy production and soil preservation. There is not a well established tradeoff as to whether the trash should be used for energy production or be left in the field. Are these conflicting options? Therefore, there is an unanswered question about if and how much sugarcane trash could be removed from the cultivated fields without jeopardizing long term soil quality and plant productivity. The ethanol industry wants to remove as much trash as possible from the field but this decision must take into account many factors and variables. In this context, the present special edition of Scientia Agricola aims at tackling the central question: "How much sugarcane trash should be left on the soil?" To accomplish this task, a Workshop promoted within the FAPESP BIOEN Program was held at the Brazilian Bioethanol Science and Technology Laboratory (CTBE) in May 2012, in Campinas, Brazil. We invited the main research groups that have been working on the different aspects of this topic in Brazil. During the workshop about 10 technical talks were presented and approximately 40 participants attended the meeting, helping with the discussions that followed. Participants were invited to submit manuscripts to compose this special issue. The articles published herein address a wide range of subjects associated with the roles of trash and its destinations. Members of the ethanol and sugar industry, who have to make decisions, were invited to present their views. Sordi and Manechini outlined a clear picture of the pros and cons of trash removal and the great possibilities opened to the industry. Landell et al. showed the large variation in the amounts, proportions and composition of trash among sugarcane varieties, indicating that not only the presently available genotypes can be chosen according to the mills energy production plans, but that sugarcane can be bred to generate varieties with different trash characteristics for the future. The effect of soil tillage and trash preservation was examined in different papers because soil quality, greenhouse gases emissions, and soil carbon (C) sequestration are key indicators of environmental impact. In the study of Teixeira et al., emission factors of CO 2-C from trash were estimated as affected by several soil tillage options and showed that, on average, 2.3 to 2.4% of the C were lost up to 15 days after tillage operations. In another study, Segnini et al. measured C stock and humification after seven years in a sugarcane field where replanting was done with or without soil disturbance, comparing no-tillage and conventional tillage combined with trash preservation. The maintenance of the plant residues greatly increased soil C stock; however, ...

Comprehensive assessment of sugarcane straw: implications for biomass and bioenergy production

“…In this context, our results suggest that the separation of green tops and dry leaves can be an effective strategy to apply throughout the sugarcane sector, regardless of variety, cycle, or site where straw is collected. In this way, separation of these two fractions should also be a basic premise for studies evaluating the potential use of sugarcane straw and represent a major consideration in the context of debates relating to the economic and environmental aspects …”

Nitrogen Use Efficiency for Sugarcane-Biofuel Production: What Is Next?

“…Sugarcane trash can be burned in boilers to generate steam for electricity production (cogeneration) or it can be used for the production of secondgeneration ethanol [24]. Considering the large-scale production of cellulosic ethanol from ground bagasse and crop residues (i.e., trash), an important topic of discussion is how to effectively manage the sugarcane residues in the fields [25]. Related issues to be addressed include the proportion of trash to be removed from soil for this purpose and how much trash should be left in the fields to provide physical, chemical, and biological benefits to the soil-plant system.…”

Straw preservation reduced total N2O emissions from a sugarcane field

“…A series of studies have started to assess such changes that have such a large impact on sugarcane fields, aiming to identify the best management practices (Cantarella et al ., ). Considering the large amount of straw and its C:N ratio, we expected changes in fertilizer dynamics and, consequently, in N 2 O fluxes.…”