Temporal Variations in Micronutrients (Cu, Fe, Mn and Zn) Mineralization as Influenced by Animal and Plant Manure-Amended Marginal Soils, Southeastern Nigeria

Low soil fertility is identified as a major factor militating against crop production in many tropical cropping systems where fertilizer used is low and agricultural residues are not returned to the soil for its rejuvenation. The present study was therefore conducted to determine the influence of organic manure application on micronutrient cations (Cu, Fe, Mn and Zn) mineralization in five different marginal soils. Four sources of animal manure (cattle, goat, poultry and swine) and two sources plant residues manure (oil palm bunch and rice husk dust) and a control were added to the soils (alluvial deposits, basalt, basement complex rock, coastal plain sand sandstone and shale) at the rate of 10 t ha-1and, incubated for 8 weeks at a temperature of 30°C. The soils were sampled at weekly intervals and analyzed for pH and available Cu, Fe, Mn and Zn. The results indicated that organic amendments increased soil pH regardless of the type of manure used. Cumulative mineralized Cu was highest in basalt (4.48 mgkg-1) followed by basement complex rock (3.52 mgkg-1) soils. Available Fe was highest in shale (4.93 mgkg-1) followed by alluvial deposit (4.93 mgkg-1) soils. Manganese was highest in basement complex rock (7.39 mgkg-1) followed by coastal plain sand (4.22 mgkg-1) soils. While, Zn was highest in basement complex rock (5.13 mgkg-1) followed by shale (4.56 mgkg-1) and alluvial deposit (4.48 mgkg-1) soils. Similarly, the cumulative mineralized Cu, Fe, Mn and Zn contents were highest in poultry manure (6.53, 5.04, 4.64 and 5.39 mg kg-1) respectively, followed by swine and goat manures. The lowest values for available Cu (1.73 mg kg-1) and Zn (1.55 mg kg-1) was in oil palm bunch while, Mn (1.33 mg kg-1) was in rice husk dust.