Influence of Tillage and Wood Ash on Zn and Fe Content of Soil, Castor Shoot and Seed

摘要

The effect of tillage methods (Mound, Ridge, Flat) and rates of wood ash on soil properties and yield of castor bean plant were studied in field trial at Abakaliki for 3 years cropping seasons. The experiment was a split plot in randomized complete block design with three tillage methods and four rates of wood ash (0 t&#8729;ha~(-1), 2 t&#8729;ha~(-1), 4 t&#8729;ha~(-1) and 6 t&#8729;ha~(-1)), replicated three times. CropStat Version 7.2 computer software for data management developed primarily for the analysis of data from agricultural field trials was used to analyze data collected from the study and mean separation was done using least significant difference (LSD) at 5% alpha level. The findings from the study showed for soil heavy metal contents, it was observed that tillage methods had no effect on the heavy metals except for 1~(st) year cropping result of Zn and 2~(nd) year cropping result of Fe. The effect of tillage methods on heavy metal contents of castor shoot showed a significant difference P < 0.05 except for 3~(rd) year result of Fe. The values obtained from Ridge and Flat were higher when compared with the value of Mound with regard to soil and castor shoot; heavy metal content with higher values was more observed in Flat method. The result of heavy metal content of seed indicated that tillage method had no effect on the heavy metal contents of the castor seed; the results of Fe, Zn in 1~(st) and 2~(nd) year planting season were not significant among the rates of wood ash applied. The effect of tillage and wood ash on heavy metal content of soil, castor shoot and seed was found to be significant (P < 0.05). The values obtained decreased as the planting season increased, and the amount was found to increase as the rates of wood ash application increased. The effect of Ridge and wood ash at the rates of 2 t&#8729;ha~(-1) (Rd_(2)), 4 t&#8729;ha~(-1) (Rd_(4)) and 6 t&#8729;ha~(-1) (Rd_(6)) on Fe 2~(nd) year planting result of castor seed was statistically similar, while the result from Mound method was found to increase the seed uptake of the tested parameters. The observed values of the tested parameters (Fe, Zn) in wood ash amended plots in the three years ’ study were beyond acceptable limits; hence reservation in the use of wood ash on continuous bases as soil amendment especially at higher rates. The findings also indicated that the use of wood ash as soil amendment on continuous basis on the same piece of land especial ly at higher rates m ight constitute pollution problems on the near future.