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Physicochemical properties of an acid ultisol subjected to different tillage practices and woodash Amendment: impact on heavy metal concentrations in soil and Castor plant

Nnadi, E.O, Mbah, C.N., Nweke, A.I., Njoku, C.
Soil & tillage research 2019
Ultisols, acidity, base saturation, cation exchange capacity, copper, crops, field experimentation, heavy metals, hydraulic conductivity, iron, lead, organic carbon, pH, phosphorus, porosity, ridge tillage, wood ash, zinc
A field experiment was conducted in 2016 and 2017 cropping seasons to determine the effects of tillage practice alone and tillage practices amended with woodash on soil physicochemical properties and soil concentration, shoot and seed uptake of heavy metals (Fe, Zn, Cu, B, Pb). The experiment was laid out as Randomized Complete Block Design with six treatments and three replications. The treatments were: mound tillage alone (MO); Ridge tillage alone (RO); Flat tillage alone (FO); Mound tillage +4 t ha-1 woodash (MW); Ridge tillage +4 t ha-1 woodash (RW) and Flat tillage +4 t ha-1 woodash (FW). Results of the study showed significant (p = 0.05) increase in soil hydraulic conductivity and total porosity in woodash amended tillage practices relative to tillage practices alone. Results of the study also showed significant (p = 0.05) increase in soil base saturation, organic carbon, available P, total N, effective cation exchange capacity, pH and decrease in exchangeable acidity in wood ash amended tillage practices relative to tillage practices alone. Significant (p = 0.05) increases in heavy metals concentration in soil, shoot and seed of castor but to non-toxic level except Fe concentration in soil were observed in tillage practices amended with woodash compared to tillage practices alone. On the average RW was observed to have the highest improvement in the studied parameters. Use of woodash at applied rate to improve soil properties does not constitute any negative effect on soil and crops.