345 DIFFERENTIAL GROWTH INHIBITION OF BRASSICA SPECIES BY BROCCOLI RESIDUES

Abstract

Poor seedling emergence and stunted growth were observed in cauliflower (Brassica oleracea L., Botrytis group) and cabbage (Brassica oleracea L., Capitata group) crops when planted after three consecutive monocrops of broccoli (Brassica oleracea L., Italica group). This study was conducted to assess seed, seedling, and plant growth responses of broccoli, cabbage, and cauliflower to broccoli residue (leaves, stem + roots, and whole plant) extracts, broccoli residue incorporation, or soil previously cropped to broccoli. Osmotic potential, electrical conductivity, and pH of extracts were measured, rate (T50) and total germination were determined. Filter-sterilized leaf extract delayed T50(7.5 d) and reduced total germination (22%) of cauliflower compared to broccoli or cabbage. Similarly, plant height, shoot dry weight, and leaf area of cauliflower were significantly reduced when grown on broccoli soil in the greenhouse. Cabbage and cauliflower had low total marketable yields with more culled heads when grown in the field previously cropped to broccoli. Therefore, a potential growth inhibition of cabbage and cauliflower exists when following a continous cropping of broccoli.