Low rates of sugarcane bagasse-derived biochar have limited effects on soil properties and sugarcane crop yield

Abstract

Sugarcane (Saccharum spp.) represents the most valuable row crop in Louisiana. High levels of biomass production and extensive tillage have degraded portions of the state's alluvial soils used to grow sugarcane. In addition to sucrose, processing the crop generates excess bagasse each year, which can represent a disposal problem for sugar factories. However, converting the bagasse to biochar at nearby pyrolysis facilities may prove to be an economical means of improving degraded soils. The objective was to determine the impacts of low rates of biochar (<3.2 mt ha−1) on soil physical, chemical, and biological properties. Plant available nutrient levels were marginally impacted by biochar additions as the biochar exhibited a relatively low surface area and neutral pH. Bagasse-derived biochar did not affect soil nitrate retention or leaching, and overall recovery was >86%. Biochar did not increase soil CO2 evolution, indicating its stability as a soil carbon amendment. However, adding biochar with mineral nitrogen decreased CO2 evolution, compared to biochar alone, indicating a negative priming effect. Soil moisture retention was minimally impacted by biochar. Cane yield, sucrose content, and sucrose yield were not statistically affected by applying biochar with or without starter fertilizer at planting. Overall, the results indicate that lower levels of bagasse-derived biochar minimally impacted soil properties and crop yield; however, the biochar was stable in soil and may find utility as a carbon-rich amendment should carbon credits prove to be an additional source of grower or land-owner revenue.