Table 4: Effect of SS and stabilized SS on Olsen-P in relation to soil type, sewage source, mixing rate, and incubation period.

TreatmentsFluvial soilCalcareous soil
SS1SS2SS1SS2
30 day60 day30 day60 day30 day60 day30 day60 day

Mixing rate, 10%

C7.7f7.7d7.7e7.6c8.8e8.8e8.8e8.8f
SS19.4c20.7b20.7b21.0a25.2b25.7b24.1abc24.9c
SS + CFA17.0d17.8c18.6c19.9a20.4d18.1d24.5ab27.2b
SS + B21.8a18.0c23.6a22.1a22.1c25.2b26.1a25.9c
SS + SBFL21.2ab19.3bc21.2b20.8a31.3a28.3a21.9bcd29.2a
SS + CaCO320.0bc18.7bc17.3cd15.3b26.1b27.3ab22.8abcd21.3d
SS + WH18.8c23.4a16.9cd15.5b20.7d22.5c20.7cd21.6d
SS + RS15.2e17.6c15.6d20.7a21.0cd20.0cd21.0bcd19.3e
SS + CS16.9d18.7bc16.1d19.1ab19.9d20.2cd19.8d22.3d

Mixing rate, 25%

C7.7c7.6f7.7f7.6d8.8h8.8e8.8f8.8f
SS19.4a20.7ab20.7b21.0a25.2b25.7a24.1b24.9c
SS + CFA16.6b16.3de19.8bc21.8a19.9ef20.9bc22.5bc25.4bc
SS + B21.2a18.6abcd23.3a21.2a21.8de22.6b24.5b29.7a
SS + SBFL19.7a21.0a18.2cd20.7a27.9a26.6a28.0a27.6ab
SS + CaCO316.9b18.1bcd17.0de16.9c24.3bc25.8a21.8cd21.6d
SS + WH19.4a17.8cde16.3e16.5c18.5fg20.4c19.8de21.9d
SS + RS14.8b15.3e16.2e16.9c18.1g17.4d18.8e19.1e
SS + CS19.5a19.3abc19.5bc19.1b22.7cd21.3bc22.6bc21.9d

Values accompanied by different letters are significantly different within column ( ).
C: control (un amended soil), SS: sewage sludge, CFA: coal fly ash, B: bentonite, SBFL: sugar beet factory lime, RS: rice straw, WH: water hyacinth, CS: cotton stalks, nd: not detected, —: not measured.