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Title: High rates of gasified rice hull biochar affect geranium and tomato growth in a soilless substrate

Author
item Altland, James
item LOCKE, JAMES

Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2015
Publication Date: 7/5/2017
Publication URL: https://handle.nal.usda.gov/10113/5801821
Citation: Altland, J.E., Locke, J.C. 2017. High rates of gasified rice hull biochar affect geranium and tomato growth in a soilless substrate. Journal of Plant Nutrition. http://dx.doi.org/10.1080/01904167.2016.1249800.

Interpretive Summary: Gasified rice hull biochar is generated as a byproduct of rice processing. Rice hulls are the unused husk, and are burned to generate power and heat for other aspects of rice processing. The char or ash that remains from the burning of the rice hulls is hereafter referred to as gasified rice hull biochar (GRHB). We found in previous work that GRHB has high concentrations of phosphorus (P) and potassium (K), two the the most commonly applied fertilizers in greenhouse crops. Subsequent research demonstrated that GRHB incorporated into greenhouse substrates at rates up to 10% by volume provided some, but not all the required P and K for greenhouse crops. The objective of this research was to determine if higher GRHB rates could be used to provide all of a greenhouse crops' P and K requirement without adversely affecting the crop. Our results suggest that higher rates of GRHB (15% to 20%) will provide sufficient P and K for production of greenhouse crops in soilless substrates over a 5 to 6 week production cycle. Some crops, including geranium, might respond negatively to these higher rates with reduced shoot or root growth, while other crops, such as tomato, may respond positively with increased growth.

Technical Abstract: Gasified rice hull biochar (GRHB) is a byproduct of rice production, where rice hulls are gasified to generate energy for other aspects of rice processing. Other research has shown that GRHB up to 10% (v/v) in a soilless substrate can provide much, but not all, of a potted floriculture crops’ phosphorus and potassium needs. The objective of this research was to determine the effect of higher GRHB rates on floriculture crop nutrition and growth. Two experiments were conducted with GRHB rates ranging from 0% to 30% (v/v) of a soilless peatmoss-based substrate. Geranium (Pelargonium ×hortorum ‘Maverick Red’) and tomato (Solanum lycopersicum ‘Megabite’) were grown in 10-cm diameter pots with amended substrates. Addition of GRHB up to 30% affected the physical properties of the peatmoss-based substrate by increasing container capacity (CC) and decreasing unavailable water (UAW). Summarizing across the two experiments, amending a peatmoss substrate with 15% and 20% GRHB provided sufficient P and K for production of geranium and tomato in soilless substrates over a 5 to 6 week production cycle. However, GRHB did not provide a sufficient source of micronutrients to support acceptable crop growth. Geranium responded negatively to high rates (>10%) with reduced shoot and root growth, while tomato responded positively to higher rates with increased shoot growth. Higher rates of GRHB (>10%) can be recommended for some crops, but not all.