Simulating Long-Term Effects of Trash Management on Sugarcane Yield for Brazilian Cropping Systems

Abstract

Historically, trash has been burnt in Brazil. Recently, increasingly crops are being harvested green with trash retailed as blanket (GCTB) due to environmental restrictions, and because of the trash use as a feedstock for bioenergy. The presence of a trash blanket affects sugarcane crops, by conservation of soil moisture and a potential to increase soil carbon (C) and nitrogen (N). To gain insights into the impacts of the burnt-to-green cane trash blanket transition, a simulation study was conducted with the APSIM-Sugar crop model. Simulations were conducted over 100 years for 3 locations: Piracicaba-SP, Palmas-TO, and Maceio-AL, addressing 2 research questions: (1) what is the yield impact of the transition from burnt to GCTB due to soil N, C and water changes; and (2) what is the impact of trash removal on yield in fields managed under GCTBs. Both questions were answered based on the same set of simulations. We simulated the transition to GCTB after 25 years of burnt management combining four N rates and 3 trash removal treatments [no trash removal, 50 % trash removal (50 %) and 90 % trash removal (90 %)]. Simulated sugarcane yields have potential to respond positively to trash retention, and stalk yield for 50 and 90 % treatments decreased at rates proportional to the trash removal rates for Maceio and Piracicaba. In Palmas, located in a drier region, simulations showed trash retention having a positive effect firstly due to soil water retention. In Piracicaba, simulations also illustrated the potential negative, short-term impact of trash blanketing on yields due to the N immobilization by the decomposing trash.