Submitted to: Journal of Environmental Horticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2013
Publication Date: 9/1/2013
Publication URL: http://handle.nal.usda.gov/10113/58150
Citation: Altland, J.E., Locke, J.C. 2013. Gasified rice hull biochar is a source of phosphorus and potassium for container-grown plants. Journal of Environmental Horticulture. 31:138-144.
Interpretive Summary: Fertilizer costs and nutrient use efficiency are important issues for greenhouse and nursery producers. Research has shown that some forms of biochar provide an abundant source of nutrients and other possible benefit when used as part of the container substrate. The objective of this research was to determine the potential nutritional value of gasified rice hull biochar (GRHB) when amended to a typical greenhouse substrate. Our data show that GRHB amendment rates up to 10% (by volume) have little or no effect on substrate pH. Gasified rice hull biochar provided sufficient phosphorus (P) and potassium (K) to the substrate to grow a geranium crop for six weeks without any additional P or K fertilizers. It was necessary to provide a micronutrient fertilizer source in addition to the GRHB to avoid chlorosis in geranium foliage. It was concluded that GRHB provides a source of readily available P and K, but lacks the correct concentration or balance of micronutrients for adequate container nutrition. Gasified rice hull biochar could be an important source of P and K for greenhouse and nursery container crops in the future.
Technical Abstract: Biochar materials have been reported to improve the chemical, physical, and biological properties of mineral soils and soilless substrates. The objective of this research was to determine the effect of gasified rice hull biochar (GRHB) on available nutrients in a container substrate. Two experiments were conducted in a glasshouse with geranium (Pelargonium xhortorum ‘Maverick Red’) in 10 cm (4 in) pots. Geranium were potted in commercial soilless medium (Sunshine Mix #2) amended with 0 to 10% GRHB. Control pots were fertilized with a commercial complete liquid fertilizer (20N-4.4P-16.6K-0.15Mg-0.02B-0.01Cu-0.1Fe-0.05Mn-0.01Mo-0.05Zn), while GRHB-amended crops were fertilized with ammonium nitrate. Additional GRHB substrates were amended with either 0 or 0.9 kg/m3 (1.5 lb/yd3) micronutrient package (Micromax). The GRHB amendment had little or no effect on substrate pH. Amendment with GRHB increased available phosphate and potassium in substrate leachates compared to the commercially fertilized controls. Substrates amended with GRHB alone were chlorotic and grew less than those amended with GRHB and micronutrients. These data demonstrate that GRHB provides sufficient P and K to support a six week production cycle of geranium, but lacks either the correct concentration or balance of micronutrients for healthy growth.