Utilization of sewage sludge as a potting media for tree nursery

Abstract

Dumping of sewage sludge in the outer of cities leads to silting of nearby tanks, polluting the lands andalso air they burn, which is a burning problem in urban areas. This sewage sludge is rich in nutrientsand their use has been found to improve the physical condition of the soil as well as increase productivityof green biomass. As it contains heavy metals it threatens the human life by way of entering into foodchain. Hence, the best possible alternative is to utilize the sewage sludge as a potting media for raisingtree seedlings in tree nursery especially timber, energy and industrial wood species. An experimentwith an objective of utilizing sewage sludge as a potting media for tree nursery was conducted atTamil Nadu Agricultural University, Mettupalayam with different potting media mixtures as treatmentsviz., T ~ Soil + Sand + FYM (1: 1: 1 ratio); T, ~ Soil +Sand + Raw Sewage Sludge (1: 1: 1 ratio); T3-Soil + Sand + 2 weeks Cornposted Sewage Sludge (1: 1: 1 ratio); T~ ~ Soil + Sand + 4 weeks CompostedSewage Sludge (I: 1:1 ratio); T ~ Raw Sewage Sludge alone; 1 6 ~ Two weeks Composted SewageSludge alone and Th~Four weeks Composted Sewage Sludge alone. Eucalyptus tereticornis, Tecto,?agrandis, Azadirac ta indica, Casuarina equisetifolia and Acacia nilotica were them grown 111polythene bags containing the above potting media. Plant height and collar diameter at two intervalsviz.,3 months and 6 months after transplanting and drymatter production at 300 DAT were recorded.The results revealed that the plant height of the E. tereticornis and T grandis at 3 months aftertransplanting was significantly higher in T 6 whereas the plant height of the other three tree speciesviz., C equisetifloia, A. indica and Acacia nilotica was significantly higher in T " At 6 months aftertransplanting the plant height of all the tree species significantly higher in T4 T3,' Ts' T4'and T i respectively.At 10 months after transplanting E. tereicornis, T grandis and C equisetifolia recorded the maximumdry matter in Ts whereas A. indica and A. nilotica recorded maximum dry matter. in T7 and T ,.Though the sewage sludge is having sufficient major nutrients, it has heavy metals especially, lead,chromium, nickel and cadmium. In this context, the nutrients and heavy metals present in the pottingmedia were analyzed at initial and 300 DAT of seedlings. The results showed that the potting mediahave considerable quantity of major nutrients and heavy metals also. But the tree seedlings haveabsorbed the heavy metals from the potting media to some extent. Hence, sewage sludge which hastoxic substances or heavy metals could be used as a potting media for raising tree seedlings especiallyenergy, industrial and timber species as they do not affect the food chain. It is concluded that Sewagesludge is an effective substitute to farm yard manure and could be used as a potting media in forestnursery on a large scale.