Growth response and mineral uptake of lettuce and tomato transplants grown in media amended with composted sewage sludge

Abstract

Lettuce, Lactuca sativa L. 'Summer Bibb' and tomato, Lycopersicon esculentum Mill. 'Westover' were grown 4 weeks in plastic market packs (MP) in 3 experimental media and a commercially available (Maryland Mix) control. The experimental media were prepared by combining equal parts, by volume of: 1) screened composted sewage sludge (CSS) (made from lime dewatered ferric chloride treated sewage sludge and wood chips), peat moss (PM), and perlite (PL) (CSS-PM-PL); 2) CSS, PM and vermiculite (VL), (CSS-PM-VL); and 3) CSS-PL-VL. A commercially prepared medium, Maryland mix consisting of silt loam, peat, perlite, and vermiculite (1:2:1:1 by vol) was used as a control. The market packs containing 6 transplants each, were arranged in a completely end of the 1st, 2nd, and 3rd week after transplanting with a commercial 20N-8.6P-16.6K (20-20-20) fertilizer. Another set of seedlings were grown for 4 weeks in the control mix and 3 experimental media and fertilized at 1st and 3rd week after transplanting with only N fertilizer. For both lettuce and tomato plants, only 270 mg of N per MP per growing period produced marketable size transplants when grown in the CSS-PM-VL medium. These seedlings had no toxic levels of Zn, Cd, Pb, and Ni and contained adequate N, P, K, Ca, Mg, Mn, Fe, and Cu as compared to plants grown in the control medium.