Profile Distribution of Selected Essential Micronutrients in Paddy Soils of Abia State, Southeastern Nigeria

Frequency of fertilizer application should be closely monitored to prevent excessive nutrient supply and environmental pollution. A field experiment was carried out in 2010 planting season at the Federal University of Agriculture, Abeokuta (FUNAAB) to determine the residual effect of organic and inorganic fertilizers on soil properties and maize yield. The treatments used were: compost (CP) derived from Tithonia diversifolia composted with poultry manure, green manure (GM) made of fresh Tithonia diversifolia, neem organo compound fertilizer (NF), sunshine organo-mineral fertilizer (OMF), poultry manure (PM) all at the rate of 10 t/ha each, chemical fertilizer (N-P-K- 20:10:10) at 120 kg N/ha and control. The treatments were replicated four times using randomized complete block design. Plant height, number of leaves, leaf area and yield of maize were assessed. The uptake of nitrogen, phosphorus and potassium by maize were determined, post planting soil samples were also routinely analyzed. Results of the experiment showed that the residual effect of organo-mineral fertilizer significantly increased maize height to 139.00 cm when compared with the control. Maize grain yield ranged between 1.64 and 5.54t/ha, CP application resulted in the highest yield. The residual effect of NF promoted the uptake of nitrogen and phosphorus (0.16 t/ha and 18.80 kg/ha respectively). Percentage increase in post planting soil nitrogen and potassium contents above the control were between 7.14 – 31.58 and 7.14 – 27.78 respectively. Highest percentage increase in nitrogen resulted from CP and PM application while potassium was from GM amended plots. Residual effect of CP significantly increased the pH and organic matter contents of post planting soil above the control. The yield of maize and soil quality were both improved on plots where CP was previously applied, thus subsequent crops on CP amended plots require no fertilization.