Gypsum and Coal-bed Methane Water Modify Growth Media Properties, Nutrient Uptake, and Essential Oil Profile of Lemongrass and Palmarosa

Coal-bed methane (CBM), an important energy source, coproduces a vast amount of saline-sodic wastewater, CBM water (CBMW), with environmental and economic disposal issues. This research evaluated under a greenhouse production system the influence of gypsum (CaSO4·2H2O) and CBMW on yields, essential oil (EO) content and composition in lemongrass (Cymbopogon flexuosus) and palmarosa (C. martinii), and on growth medium pH and available nutrients. CBMW treatments had higher pH than tap water treatment. Gypsum reduced pH in all CBMW treatments but did not affect pH in tap water treatment. While CBMW may increase the available Cu and Fe in growth medium, the application of gypsum may negate this effect. CBMW significantly increased growth medium Na. Gypsum increased growth medium S, and CBMW increased S in the high gypsum treatments. Palmarosa height, fresh weight, geranyl acetate, and isoneral in lemongrass EO were reduced, while geraniol in palmarosa EO increased with CBMW relative to tap water. In distillation waste plant tissue, CBMW increased Na in lemongrass and palmarosa by almost eight times; increased total P, S, and Mn in palmarosa; and reduced total N, S, Ca, and Mg in lemongrass and Ca in palmarosa, relative to tap water. This study demonstrated that CBMW may be used for greenhouse production of high-value crops, but it may affect the yields and oil content of some crops and growth medium characteristics.