Response of Periwinkle to Composted Sewage Sludge Used as a Soil Amendment

Abstract An experiment was conducted in the greenhouse to investigate the effects of composted sewage sludge as a soil amendment on growth and mineral composition of ‘Bright Eyes’ periwinkle (Catharanthus roseus (L.) G. Dn.). Three desert soils (loamy sand, sandy loam, clay) were amended with two different composted sewage sludges (city and county) at rates of 0, 7.5, 15, 30 and 60% by volume. Plants were grown in the amended soils for four months. Composted city sludge had a positive effect on size, growth rate and number of flowers per plant in all three soils. Plants grown in soils amended with the county sludge grew poorly and developed an interveinal chlorosis. Tissue analysis suggested chlorosis was due to a calcium-induced manganese deficiency. Whole plant tissue Mn declined to as low as 23 mg/kg when the calcium in the soil extract exceeded 25 meq/liter.