Effect of sewage sludge and fertilizers on accumulation of micronutrients and yield of cauliflower (Brassica oleracea var botrytis) in an alluvial soil

A field experiment was conducted at Bichpuri (Agra) during rabi seasons of 2007-08 and 2008-09 by using treated sludge along with fertilizer levels to study the effect on yield and accumulation of heavy metals in cauliflower [(Brassica oleracea var botrytis (L.)] and soil. The eight manurial treatments consisted of inorganic and organic sources (treated sludge and FYM) of nutrients. Application of 10 tonnes sludge/ha significantly enhanced the yield and dry matter of cauliflower curd by 36.0 and 36.8% over control, respectively. Increasing levels of NPK fertilizers up to 150% increased the mean curd yield, dry matter yield, content and uptake of elements significantly over control. The maximum curd (33.08 and 28.71 tonnes/ha) and dry matter yields (11.39 and 9.86 tonnes/ha) were recorded under 100% NPK + 10 tonnes treated sludge/ha and minimum (10.83 and 10.45 tonnnes/ha and 3.68 and 3.54 tonnes/ha) under control in first and second year, respectively. Therefore, for the higher productivity of cauliflower about 50% NPK fertilizers could be replaced with addition of treated sludge. Application of 100% NPK + 10 tonnes sludge/ha resulted in the maximum contents of heavy metals in cauliflower curd over control and sludge treated soil. The content of Pb only in curd exceeded the threshold values but no reduction in yield was noted. The highest uptake of Fe (1364 g/ha), Mn (428 g/ha), Cu (121 g/ha), Zn (396 g/ha), Cd (6.1 g/ha) Ni (6.9 g/ha), Pb (52.2 g/ha) and cobalt (7.2 g/ha) by cauliflower curd was recorded under 100% NPK + 10 tonnes sludge/ha. Soil amended with sewage sludge alone resulted in significant build-up of DTPA-extractable micronutrients and heavy metals over control. Combined use of 100% NPK + 10 tonnes sludge/ha resulted in further build–up of micronutrients and heavy metals over sludge treated soil. Thus, it can be concluded that use of sewage sludge can be followed as a good supplement of nutrients for crop production, but care should be taken for the presence of heavy metals and pollutants.