Aerated chicken, cow, and turkey manure extracts differentially affect lettuce and kale yield in hydroponics

Purpose Manure extracts possess great potential as alternate inorganic fertilizers. However, limited information exists onhow manure influences plant growth. This study’s aim was to determine the impact of aerated manure extracts on romainelettuce (Lactuca sativa var. longifolia) and Russian kale (Brassica napus var. ‘Red Russian’) in hydroponic systems.Methods Chicken, cow, and turkey manure extract solutions (10, 25, and 50 g/L manure) were compared to a control(Hoagland) solution for lettuce and kale grown in an ebb and flow hydroponic system.Results The aboveground dry mass of lettuce grown in a 50 g/L turkey manure extract solution was greater than that of thecontrol. The largest aboveground wet mass for kale occurred with the control. Nutrient analyses of all manure extract solutionsshowed a 29%–79% higher concentration of NH4–N and higher total nitrogen than the control. Principal componentanalysis of the nutrient solutions identified six nutrients that should be monitored to maximize plant yield when using manureextracts in hydroponics: NO3−, NH4+, Ca, Mg, Mn, and Na.Conclusions Healthy lettuce and kale plants were grown in turkey manure extract solution (50 g/L). However, reducedaboveground wet and dry mass were recorded for both plants in chicken and cow manure extract solutions compared to thecontrol. NH4+ toxicity likely killed all plants grown in chicken extract (50 g/L). Apart from NH4+ and P, all nutrients werebelow suggested concentrations suggested for lettuce growth. A combined manure/mineral fertilizer may be necessary tooptimize hydroponic solutions.