Sugarcane and pine biochar as amendments for greenhouse growing media for the production of bean (Phaseolus vulgaris L.) seedlings

Authors: Webber Iii, Charles; White, Paul; GU, MENGMENG - Texas A&M Agrilife; Spaunhorst, Douglas; Lima, Isabel; Petrie, Eric

Submitted to: Journal of Agricultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2018
Publication Date: 3/15/2018
Citation: Webber III, C.L., White Jr, P.M., Gu, M., Spaunhorst, D.J., Lima, I.M., Petrie, E.C. 2018. Sugarcane and pine biochar as amendments for greenhouse growing media for the production of bean (Phaseolus vulgaris L.) seedlings. Journal of Agricultural Science. 10(4):58-68. https://doi.org/10.5539/jas.v10n4p58.
DOI: https://doi.org/10.5539/jas.v10n4p58

Interpretive Summary: Research was conducted to determine the impact of sugarcane biochar as an amendment to soilless planting media for the production of green bean (Phaseolus vulgaris L.) 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. Sugarcane bagasse biochar (SBB) and pine biochar (PB) were each 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). Green bean variety ‘Bowie’ seeds were planted in each of the 10 different planting mixtures. The greater fixed carbon percentage increases the energy value (HHV and LHV) of the PB compared to the SBB, and may influence the potential income streams for the two biochars.The particle size distribution for the two biochars are in stark contrast to each other with the PB particle median, mean, geometric mean, and mode much greater than those of the SBB. These differences in particle size and distribution significantly increased the bulk density and decreased the pore space (%), water saturation (%), and water at field capacity (%) of the PB in contrast to the SBB, although all of these parameters remained in suitable ranges for soilless growing media. As amendments to the soilless greenhouse growing media, the biochars (SBB and PB) functioned very well, especially at the 25% and 75% levels. The 100% SBB performed as well as the 100% commercial soilless growing media and slightly better than the 100% PB when comparing seedling fresh and dry weights. The 100% PB is not recommended as a soilless growing media even with the supplemental fertilizer used in these experiments. These results indicate that the volume of a standard soilless greenhouse growing media can be successfully extended by adding 25% to 75% SBB and PB without reducing bean seedling growth. Future research is needed to evaluate these biochars for the production of additional plant species.

Technical Abstract: Louisiana sugarcane farmers in 2016 harvested 11.7 million Mg of 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 one solution to reduce the excess supply. Research was conducted to determine the impact of sugarcane biochar as an amendment to soilless planting media for the production of green bean (Phaseolus vulgaris L.) seedlings. Sugarcane bagasse biochar (SBB) and pine biochar (PB) were each 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). Green bean variety ‘Bowie’ seeds were planted in each of the 10 different planting mixtures. The greater fixed carbon percentage increases the energy value [higher heating value (HHV) and lower heating value (LHV)] of the PB compared to the SBB, and may influence the potential income streams for the two biochars. The particle size distribution for the two biochars are in stark contrast to each other with the PB particle median, mean, geometric mean, and mode much greater than those of the SBB. These differences in particle size and distribution significantly increased the bulk density and decreased the pore space (%), water saturation (%), and water at field capacity (%) of the PB in contrast to the SBB, although all of these parameters remained in suitable ranges for soilless growing media. As amendments to the soilless greenhouse growing media, the biochars (SBB and PB) functioned very well, especially at the 25% and 75% levels. The 100% SBB performed as well as the 100% commercial soilless growing media and slightly better than the 100% PB when comparing seedling fresh and dry weights. The 100% PB is not recommended as a soilless growing media even with the supplemental fertilizer used in these experiments. These results indicate that the volume of a standard soilless greenhouse growing media can be successfully extended by adding 25% to 75% SBB and PB without reducing bean seedling growth. Future research is needed to evaluate these biochars for the production of additional plant species.