Gasified Rice Hull Biochar Affects Nutrition and Growth of Horticultural Crops in Container Substrates

Abstract

This research was conducted to determine if gasified rice hull biochar (GRHB), inherently high in phosphorus and potassium content, could be used as an amendment to container substrates to eliminate the need for other phosphorus and potassium fertilizers. Geranium ( Pelargonium x hortorum ‘Maverick Red’), pansy ( Viola x wittrockiana ‘Mammoth Blue Deep Dazzle’), sunflower ( Helianthus annus ‘Pacino Gold’), zinnia ( Zinnia elegans ‘Oklahoma White’), and tomato ( Lycopersicon lycopersicum ‘Mega Bite’) were grown in a standard commercial soilless substrate composed of sphagnum peat moss:perlite (85:15, by vol) and amended with 0, 5, or 10% GRHB (by vol). A group of plants labeled as NPK-fertilized controls were fertilized with 7.1 mM nitrogen (N), 0.7 mM phosphorus (P), and 1.4 mM potassium (K) derived from ammonium nitrate (NH 4 NO 3 ) and potassium phosphate (K 2 HPO 4 ). Other treatments received 0, 5, or 10% GRHB and fertilized with 7.1 mM N using NH 4 NO 3 . Gasified rice hull biochar had little effect on substrate pH over the course of the experiment. While pH was higher with 10% GRHB than NPK-fertilized controls by 6 weeks after potting (WAP), the difference was only 0.19 pH units. The GRHB used in this study provides a source of readily available phosphate and potassium when incorporated at 5 or 10%. While the five crops grown in this study were of similar size and lacked any signs of nutrient deficiency when amended with GRHB, foliar concentrations of P and K were low when their only source was from pre-incorporated GRHB.