Evaluation of Flue-Gas Desulfurization gypsum in Poultry Litter as a Substrate Component for Greenhouse Horticultural Crops

A study was conducted to evaluate the growth response and consumer preference of three plant species to substrate blends containing flue gas desulfurization gypsum (FGDG). Substrate blends used in this study were derived from a previous experiment that evaluated the use of FGD Gas a bedding material for broiler chicken production. Five litter treatments chosen from the broiler study were mixed at a 50:50 ratio with crushed pine bark (CPB) giving rise to the following treatments: Pine shavings (PS)+CPB (50:50 v/v); FGDG + PS + CPB(25:25:50 v/v/v); FGDG +CPB(50:50 v/v), Pine bark (PB)+ CPB (50:50 v/v); and FGDG + PB + CPB (25:25:50v/v/v). These treatments were compared to CPB + Farfard 3B (50:50 v/v) as the control (industry stand and).The five broiler litter based substrates (treatments) contained poultry manure while the control did not. There were differences in consumer preference, plant growth, foliar greenness (SPAD values), and drainage rates among substrates (treatments) and their suitability for growing plants. In the substrate based on poultry litter from 100% FGDG bedding, flocculation created good drainage, higher CEC, and greater pore space. This 1: 1 FGDG: CPB substrate had a lower, more desirable pH level, a higher calcium level, and less phosphorus leached from the substrate after watering suggesting the possibility of calcium binding excess phosphorus in the leachate water. Substrates components for greenhouse crops have changed over the years for various reasons. One reason is the availability and costs of substrate components that fluctuate, forcing growers to seek less expensive, readily available alternative substrate components. The primary substrates used in the nursery and greenhouse industry since the 1970’s have been pine bark and peat moss. However, in recent years other uses for pine bark have caused a constriction of pine bark availability for horticultural substrates [1]. Increased availability of alternative substrates for the nursery and greenhouse industry has been a justified pursuit for much research [2,3]. Poultry litter has been one of the materials considered for potential use in the nursery industry [4-6], but most of the litter evaluated in the past has been pine wood shavings or sawdust, with very few studies evaluating litter based on pine bark bedding [7]. Gypsum has also been considered as a substrate component for growing horticultural crops [8,9]. An important influence on best practices across a number of agricultural and industrial industries has been federal environmental protection regulations. Two industries, the poultry industry and coal-fired electric companies, are currently required to manage their waste differently than in the past. For example, large poultry operations are required to submit and use a Water and Nutrient Management Plan [10]. There are numerous reasons why alternative substrate options are needed. Costs of materials can become prohibitive, availability may change [2], consumer preferences may change [5,11], and environmental concerns [3,6,8,10,12-16] and regulations Agriculture and Agri-Food Canada [17], may alter recommended best practices [10]. Research seeking alternative substrates increased in the 1970s resulting from increased populations with an increased demand for container grown plants nationwide [18], erratic supplies of peat moss, and a need to reduce landfill use [3-5,13,14,17,19-21]. Horticulturists are in a unique position to help solve pollution problems caused by the disposal of certain waste materials, which would otherwise become environmental problems [3,13,16,22]. Some materials evaluated for use as horticultural substrate components have included spent tea grinds [23], gasifier residue [24], clean chip residual and processed whole pine trees [2]. Results from studies using composted chicken litter as an alternative to inorganic fertilizers in the landscape and as a substrate component for containers proved suitable in both cases [6]. In another study bio-solids saturated newspaper crumbles or composted poultry litter was added at 25% vol:vol to either ground pine chips or pine bark. Substrates amended with composted poultry litter produced the largest plants across all treatments [3]. Gypsum has been studied both as a substrate component as well as a fertilizer and chemical stabilizer of phosphorus in poultry litter, with the intent of minimizing negative environmental impact on local ground water and waterways with great success.