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

Authors: White, Paul; Ellsworth, Patrick; Lima, Isabel

Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2023
Publication Date: 10/30/2023
Citation: White Jr, P.M., Ellsworth, P.Z., Lima, I.M. 2023. Low rates of sugarcane bagasse-derived biochar have limited effects on soil properties and sugarcane crop yield. Agrosystems, Geosciences & Environment. 6(4).Article e20430. https://doi.org/10.1002/agg2.20430.
DOI: https://doi.org/10.1002/agg2.20430

Interpretive Summary: Sugarcane is the most valuable row crop in Louisiana. Tillage and nutrients removed during harvest have degraded soils used to grow sugarcane. During processing of the crop to produce sugar, large amounts of bagasse are generated. The factories do not use all of the bagasse to generate steam and any leftover must be disposed of or left near the factory. The excess bagasse can be made into biochar and applied to soil to improve its ability to grow sugarcane. However, we do not know how this biochar will change soil nutrient levels that might affect sugarcane growth. Our purpose for these experiments was to determine what effects the biochar has on soil properties. Overall biochar did not negatively impact any soil properties. In fact, the biochar increased the soil carbon level, a critical value that measures how productive a soil is for agriculture. So far, the biochar has not changed sugarcane yields but we are continuing to take measurements over the next few years to determine if biochar impacts stubbling ability of the sugarcane crop.

Technical 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 near-by pyrolysis facilities may prove to be an economical means of improving degraded soils. Much of the scientific literature focuses on high levels of biochar additions, which may not be economical to individual growers. The objective of this research was to determine the impacts of lower 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 statistically 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 of nitrogen. Soil moisture retention was only minimally impacted by biochar, which decreased the field capacity of the soil tested. 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.