Agronomic and environmental performance of biochar amendment in alluvial soils under subtropical sugarcane production

This study investigated the amendment of sugarcane bagasse biochar (SCBB) on soil fertility, crop yield, and nutrient loss in two different-textured soils under sugarcane (Saccharum spp.) production. Eleven megagrams per hectare of freshly incorporated biochar increased yield of plant cane by 22% in light-texture soil (LS) and 12% in heavy-textured soil (HS). Although the overall yield of the ratoon crop was lower, the biochar treatment produced 20 and 14% higher yields than the control at the LS and HS sites, respectively. Biochar increased soil carbon (C-soil) across LS and HS sites by 15% and decreased the soil C/N ratio by 19%. Over the two growing seasons and sites, cumulative runoff volume, and loads of NO3--N, PO4-3-P, biological oxygen demand (BOD5), total organic C (TOC), and total suspended solids (TSS) were reduced by 33, 35, 39, 25, 24, and 54% with biochar. Calcium and K losses in runoff were also reduced by 43 and 24% with biochar. It reduced NH4+-N leaching in LS and HS soils over the two growing seasons by 33-167% and 66-81%, respectively, and reduced PO4-3-P leaching by 45-57% in HS over 2 yr. Although biochar is not considered a fertilizer, SCBB acted as a source of nutrients, increasing soil fertility and crop yield. It also reduced nutrient losses during heavy rain events typical of the subtropical climate of Louisiana.