Sugarcane Biochar as an Amendment for Greenhouse Growing Media for the Production of Cucurbit Seedlings

Louisiana sugarcane farmers in 2016 harvested 11.7 million Mg millable sugarcane from 163,000 ha, producing 1.47 million Mg of raw sugar and an estimated 3.5 million Mg of bagasse. Even though Louisiana sugar mills use 80 to 90% of the bagasse for fuel production, another 350,000 to 700,000 Mg of bagasse accumulates each year. The conversion of the excess bagasse into biochar is an excellent option with numerous uses. Research was conducted to determine the impact of sugarcane biochar as an amendment to soilless planting media for the production of cucurbit seedlings. Two biochars were combined by volume with a commercial certified organic soilless growing media into 5 combinations (0%-100%, 25%-75%, 50%-50%, 75%-25%, and 100%-0%, biochars and growing media, respectively). Squash (Cucurbita pepo L.) var. ‘Enterprise’ and cantaloupe (Cucumis melo L.) var. ‘Magnum .45’ were planted in each of the 5 different planting mixtures. The higher heating value (HHV), lower heating value (LHV), and fixed carbon (FixC) were greater for the standard bagasse biochar (SBB), therefore, making it more valuable as a potential fuel source than the pneumatic bagasse biochar (PBB). All of the biochar mixture combinations compared favorably to the commercial media with low bulk densities (0.11 to 0.14 g cm-3) and high water holding capacities (80-87%). In respect to seedling production, the biochars (SBB and PBB) performed well, especially at the 25 and 50% levels for both plant species. The squash seedlings responded better at the 75% level than the cantaloupe seedlings, which reflect differences in nutrient requirements. The 100% biochar growing media are not recommended because both plant species often had a decrease in organic matter. These results indicate that the volume of a standard soilless greenhouse growing media can be successfully extended by adding 25 to 50% sugarcane biochar without a reduction in squash and cantaloupe seedling production. Future research should investigate the impact of additional plant species, as well as different biochar sources on seedling production.