Assessment of depth distribution of micronutrients (Cu, Fe, Mn and Zn) in soils under a long term fertilizer use in Imo, southeast Nigeria
To assess the long term fertilizer application and continuous cropping effects on soil micronutrient, this study examined the depth distribution of iron, manganese , Copper and Zinc at depth of 0-5, 5-10,10-20, 20-30, 30- 50, and 50- 100cm, of ultisols of Imo Southeast, Nigeria. Four treatments comprised of; 15 years land fallow of no fertilizer amended site (CONT) , 12 years organic fertilizer amended site (OFA) of 200 kg ha-1 year-1, 10 years inorganic fertilizer amended (IFA) site of 200 kg ha-1 year-1 and 10 years organic and inorganic fertilizer amended site (CFA) of 300 kg ha-1 year-1. Three profile pits were dug each year in 2013 and 2014, at all the experimental treatments and a total of 108 composite samples were generated over these study period in all the sites and were arranged in Completely Randomized Design (CRD). Sample means were separated with Fischer Least Significant Difference at p = 0.05. Micronutrients were affected by long term fertilizer amendment. Thus, the OFA site in the 0-5cm depth with Fe, Mn, Zn content of 9.40, 9.49, 18.33 mg/kg were significantly higher than the other amended sites while, the CFA sites with Cu content of 1.72mg/kg was higher than other site at the same depth. Micronutrients decreased with depth in all the sites. The last soil depth of CFA site recorded copper, iron, manganese, zinc contents of 0.36, 0.17, 2.24, 1.74 mg/kg, respectively and was significantly higher than other treatment sites at same depth. This result may have occurred mainly do leaching, anthropogenic disturbance, biological cycling and strongly affected by long term fertilizer amendment and continuous cropping.
Keywords: Assessment, Concentration, fertilizers, Micronutrient and distribution
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