Closing the Loop: Use of Biochar Produced from Tomato Crop Green waste as a Substrate for Soilless, Hydroponic Tomato Production

Abstract

<jats:p>Greenhouse tomato (<jats:italic>Lycopersicum esculentum</jats:italic> Mill.) producers are urged to reduce their environmental footprint. Here, the suitability of biochar produced from tomato crop green waste as a substrate for soilless, hydroponic tomato production was evaluated. Substrates containing different combinations of biochar (BC) and pine (<jats:italic>Pinus radiata</jats:italic> D. Don) sawdust (SD) were produced (BC0-SD100, BC25-SD75, BC50-SD50, BC75-SD25, and BC100-SD0) and characterized. The effect of these substrates on tomato growth, yield, and fruit quality was studied. Most of the measured properties of substrates containing biochar were suited to use as a soilless substrate. The electrical conductivity (EC) of substrates containing biochar was initially high (&gt;4.6 mS·cm<jats:sup>−1</jats:sup>), but was easily reduced to &lt;0.5 mS·cm<jats:sup>−1</jats:sup> by rinsing with water before use. The pH of substrates containing biochar was higher than is considered acceptable for tomato production (7.5–9.3) but did not significantly (<jats:italic>P</jats:italic> &lt; 0.05) affect any plant growth, yield, and fruit quality indicators measured compared with those of plants grown in pine sawdust. The results support the concept of creating a closed loop system whereby biochar produced from tomato crop green waste is used as a substrate for soilless, hydroponic tomato production, providing a sustainable means to support the growth of high-value food crops.</jats:p>

Assessment of biochar and hydrochar as minor to major constituents of growing media for containerized tomato production

“…In fact, plants of Gransol RZ grown in substrates containing the highest doses (75% and 100%) of the char, which were the only ones that were still alkaline at the end of the experiment, had reduced leaf content of some nutrients such as P, K and Ca, although these were still within adequate range for tomato . These results did not agree with those presented by Dunlop et al ., who did not observe any decrease in nutrient content in tomato leaf in spite of the strong alkalinity of the biochar‐containing substrates used in their experiments. A second, but also relevant, possible cause for the deficient nutrient supply of these substrates might be related to the physical properties of BCH‐FW.…”

“…Nonetheless, the initial extremely high salinity, which might have lasted for the two or three first weeks of cultivation, might have caused a delay in plant growth, mainly in Gransol RZ, which seemed more sensitive to salinity than Cuarenteno, yet the reduction in substrate salt content through the culture enabled plants to produce a good yield. After rinsing an extremely saline biochar from tomato crop waste, Dunlop et al . did not find any negative effect in the growth and yield of tomato plants grown in it compared to those grown in a pine sawdust substrate.…”

“…Generally, biochar has been applied as a minor component in the growth mix (>50%, v/v). 4,5,8,14 Only in a few cases for biochar, 7,24 and never, to our knowledge, for hydrochar, have high doses (50-100%, v/v) been assayed.…”

Mixed Hardwood and Sugarcane Bagasse Biochar as Potting Mix Components for Container Tomato and Basil Seedling Production

“…The effects of biochar on plant growth could be positive, null and negative [6,42,43], depending on the types of biochar and the incorporation rates. Incorporating biochar made from woodchips of Pinus densiflora and Quercus acutissima and rice husk at 20% (by vol.)…”

“…Even though the effects of biochar on plant biomass can be variable [6,42,43], the effects of biochar on plant GI is more often positively reported [6,27,45]. The GI of plants can be an important parameter for landscape plants such as Magnolia, Ilex, Lagerstroemia and other species [46].…”