Straw Removal Affects Soil Physical Quality and Sugarcane Yield in Brazil

Abstract

Industrial use of sugarcane straw for bioenergy production represents a promising opportunity for the Brazilian sugarcane sector. Nonetheless, intensified straw removal may aggravate the effects of mechanized harvesting and increase the risks of soil compaction, declining sugarcane yield. An experiment was designed, and four field studies were conducted to evaluate the cumulative effects of straw removal on soil physical attributes (bulk density, BD; soil resistance to penetration, SRP; macroporosity, MaP; microporosity, MiP, and mean weight diameter of soil aggregates, MWD) and their relationship with crop yield under clayey and sandy soils in the Sao Paulo state, Brazil. In each field study, four straw removal rates (no removal, NR; low removal, LR, removal of 5 Mg ha−1; high removal, HR, removal of 10 Mg ha−1; and total removal, TR, removal of 15 Mg ha−1) were arranged in a randomized block design with four replicates. The 4-year intensive management of straw removal (HR and TR) resulted in an increased soil compaction (BD and SRP values) and reduced the MWD in both sandy and clayey soils. Our findings also showed that these effects are more significant in sandy soils, where soil carbon content was substantially reduced in HR and TR treatments. Sites with higher BD and SRP induced by straw removal were strongly associated with lower sugarcane yields, especially in sandy soils. Conversely, our findings indicate that LR was not detrimental to soil physical quality and sugarcane yield. Nevertheless, considering the multifunctionality of straw in sustaining multiple ecosystem services in different soil types, straw management should be defined taking into consideration site-specific conditions. We advocate that recommendations for straw removal should also be combined with other conservationist soil management practices in order to minimize soil compaction and its negative implications on sugarcane yield and other ecosystem services.