Yields and heavy metal uptake of cocoyam (Xanthosoma sagittifolium) and effects on soil properties of different tillage practices and application of burnt rice husk dust in Abakaliki, south-east Nigeria

Indigenous crops play a critical role in the socioeconomic growth of developing nations where there have been calls for exploitation of these staple crops. This study investigated the yield and heavy metal uptake of cocoyam and changes in soil physical properties in relation to different tillage practices and the application of burnt rice husk dust (BRHD). The experiment was arranged as a split plot in a randomised complete block design (RCBD) with six treatments and three replications. The treatments were: mound tillage (no BRHD); ridge tillage (no BRHD); mound + 10 t ha(-1) BRHD; mound + 20 t ha(-1) BRHD; ridge + 10 t ha(-1) BRHD and ridge + 20 t ha(-1) BRHD. The results showed that soil bulk density (at 45 days after planting, DAP) was lower when the tillage practices were combined with the amendment of burnt rice husk dust, while total porosity (at 45 DAP) and aggregate stability were higher. The yields of cocoyam corms were also higher for tillage practices combined with amendment with burnt rice husk dust. The concentrations of heavy metals (Cu, Fe, Pb and Zn) in the cocoyam corms were higher for plants grown in soil amended with BRHD, but the levels were still below the levels considered harmful in food crops. Burnt rice husk dust could be recommended for use as a soil amendment in the study area to improve soil properties and increase the production of cocoyam, without increasing the concentration of heavy metals in the corms to harmful levels.