The 2009 ASHS Annual Conference

Hydroponic production systems utilizing substrate has traditionally used perlite, a non-renewable resource, as a major component of the substrate. Perlite is used to provide aeration and drainage and has the benefits of being sterile, a neutral pH, lightweight and disease free. The main disadvantage of perlite is it is non-renewable and does not decompose. Parboiled rice hulls (PBH), a renewable resource from rice production, are used in substrates in the ornamental and nursery industries. However, no research exists on PBH as a replacement for perlite in hydroponic production. Our question was if PBH could be used as a replacement for perlite in a hydroponic substrate. A vertical hydroponic system with two substrates consisting of approximately 85% perlite or PBH and 15% coir was used. Two towers with eight pots each were planted with parsley, basil, peppermint, nasturtiums and pansies for each substrate. Herbs were harvested weekly when the petiole or stem length exceeded 6-8 inches. Flowers were harvested when petals were open. Fresh weight and flower/stem number of the four plants in each pot per tower were weighed and counted at each harvest from mid-April to mid-July. No statistical differences were found between the two substrates for fresh weight or flower/stem number for any crop. Fresh weight per tower was 4.8 kg of basil, 3 kg of peppermint, 2.7 kg of parsley and 1.9 kg of pansies and nasturtiums over the 3 months.  Thus, PBH can be used as a renewable substrate component for hydroponic production.