Effect of Citrate Concentration on the Extraction Efficiency of Selected Micronutrients from Soil

This study was carried out with the objective of evaluating the effect of citrate concentration on the extraction efficiency of some micronutrients from soil. Composite surface soil samples (0–20 cm) were collected from Eastern Harage Zone (Babile and Haramaya Districts), Wolaita Zone (Damot Sore, Boloso Bombe, Damot Pulasa and Humbo Districts) and Dire Dawa Administrative Council in purposive sampling. The treatments were arranged in completely randomized design (CRD) with three replications. A greenhouse pot experiment with soybean plant was conducted to determine the correlation between soil test methods and the selected micronutrients, such as iron (Fe), copper (Cu), manganese (Mn) and zinc (Zn) in the leaves of the plant. The results showed that, among the different citrate concentrations with strontium chloride (SrCl₂) tested for the determination of available Fe, Mn and Zn, the highest correlation coefficients (r = 0.82, p < 0.05), (r = 0.96, p < 0.001) and (r = 0.98, p < 0.001) were found between the diethylenetriamine pentaacetic acid (DTPA) method and 0.02 M strontium chloride (SrCl₂)-0.025 M citric acid extractant, respectively. Therefore, 0.02 M SrCl₂-0.025 M citric acid extractant is considered to be the most effective for the determination of Fe, Mn and Zn in soils of the studied areas. Similarly, high correlation coefficients (r = 0.97, p < 0.001) were found between DTPA and 0.02 M SrCl₂-0.05 M citric acid and (r = 0.88, p < 0.01) between DTPA and 0.02 M SrCl₂-0.025 M citric acid extractants for the determination of available Cu from soils. Hence, the 0.02 M SrCl₂-0.05 M citric acid extractant was shown to be the best for the determination of Cu in soils of the studied areas. However, considering the use of universal extractant, the 0.02 M SrCl₂-0.025 M citric acid extractant could easily be adopted as a procedure for the determination of Fe, Cu, Mn and Zn for both agricultural and environmental purposes. The greenhouse experiment confirmed the result.     

Soil–Plant Nutrient Status and their Relations in Maize-Growing Fields of Wolaita Zone,Southern Ethiopia

This study investigates the soil–plant nutrient status and relationship in Wolaita, Southern Ethiopia. Maize leaves, soil samples and field history were collected. The result indicated that continuous cultivation without fallowing, complete crop residue removal and inadequate fertilization were common practices. The soil was low in organic carbon, total nitrogen, available phosphorus, potassium, sulfur, boron and copper. Tissue analysis indicated 100, 84, 54 and 28% deficiency of nitrogen, phosphorus, potassium and copper, respectively. Significant and positive correlations (r = 0.70, 0.40 and 0.50) of soil phosphorus, calcium and copper with tissue content were observed. Soil pH was correlated with tissue phosphorus (r = 0.4), iron (r =—0.3) and manganese (r = ?0.7). Overall, the levels of calcium, magnesium, iron, manganese and zinc were adequate for maize. Therefore, fertilizer application addressing nitrogen, phosphorus, potassium and copper deficiencies is recommended for the study area.