Evaluation of organic wastes as soil amendments for cultivation of carrot and chard on irrigated sandy soils

Abstract

A field trial was designed to test the potential of various wastes as soil amendments in horticultural production. Swiss chard (Beta vulgaris L.) and carrot (Daucas carota L.) were grown during 1993–1995 under irrigation in a coarse-textured, British Columbia soil to which annual applications of 45 t ha−1 of various organic amendments plus NPK-fertilizers had been applied. The amendments included biosolids from Vancouver, Kelowna and Penticton, biowastes from Aldergrove and Abbotsford, and peat. Yield of both chard and carrot was increased for some organic treatments plus fertilizer relative to plots receiving commercially recommended rates of NPK-fertilizer only (control plots). Leaf N, P, Zn and Cu concentrations of both crops were usually elevated, but not to toxic values, in plots receiving wastes containing high concentrations of the respective nutrients. By the end of the third growing season, extractable P, Zn and Cu increased in the surface 15 cm of soil, relative to control plots, with P and Cu increases evident to 30 cm depth. Extractable K and pH varied, with applied waste with some treatments having higher and other treatments lower values than in control plots. The cumulative evidence suggested that many locally produced biosolids and biowastes have the potential to improve soil quality and the growth of high value horticultural crops. Key words: Leaf N, leaf and extractable soil P, K, Mn, Zn and Cu, soil pH and EC, yield