Effects of treated piggery effluent from an amended constructed wetland on the growth of the Okra plant (Abelmoschus esculentus)

Abstract

This research investigates the effects of treated piggery effluent from cassava peel-based biochar-amended constructed wetlands on the growth of the Okra plant (Abelmoschus esculentus). A batch-fed pilot-scale Horizontal sub-surface flow constructed wetland (HSSFCW) planted with Vertiveria zizanioides was operated with a 3-day Hydraulic Retention Time (HRT). Four different substrates comprising sharpsand SS, quarry dust QD, sharpsand amended with biochar (SS+B) and quarry dust amended with biochar (QD+B). The biochar and piggery effluent were characterized before and after treatment in the HSSFCW using standard procedures. The treated effluents from the four systems were applied to the Okra plant and growth parameters of Leave area index LAI, Plant height Ph and stem diameter QD, were measured for five consecutive weeks and analyzed. The results show that substrate types have a significant effect on LAI and QD but insignificant for Ph. The highest measured LAI, Ph and QD were 13, 317 mm and 12 mm respectively for SS; 12, 323 mm and 14 mm for QD, 25, 307 mm and 14 mm for SS+B and 27, 325 mm and 17 mm for QD+B.  The biochar-amended quarry dust CWs effluent is recommended as the best for the treated effluent irrigation for okra plant cultivation.