Nodulation and Grain Yield of Soybean and Selected Chemical Properties of the Soil as Affected by Liming at Bako Area, Western Ethiopia.

Abstract

Soil acidity has remarkably been one of the bottlenecks to sustainable agricultural production and productivity that had been prevalent in western part of Oromia with varying degrees of predicament from place to place. A field experiment was conducted to study the effects of liming on root nodulation and grain yield of soybean and selected chemical properties of the soil at Bako Agricultural Research Center during 2013 main cropping season. There were six treatments comprising five levels of lime and a control with recommended rate of inorganic fertilizer. The experiment was laid out in a randomized complete block design with three replications. Analysis of the results revealed that liming had significant effects on the number of nodules per plant and nodule dry weight per plant, plant height, above ground biomass and grain yield. Application of lime at the rate of 4.68 t/ha, which constituted 150% of the recommended rate, was superior to the application of lime at the lower rates in terms of the number and weight of nodules produced per plant. Similarly, grain and biomass yield responses were found to differ under various rates of liming although application of 0.78t/ha lime in excess of the recommended amount resulted the highest improvement. The highest total grain yield of 4.69t/ha and above ground biomass weight of 8.27 t/ha were obtained in response to the application of 3.91 t/ha lime which amounted to 125% of the recommended level (i.e.,3.12 t/ha). The yield advantage obtained from liming the soil at this rate over the no-liming (control) was 0.77 t/ha and 1.81 t/ha for grain and biomass yields respectively. With respect to soil chemical properties, it was observed that application of lime brought significant variations in soil pH, exchangeable acidity, Total N, Available P, CEC, exchangeable Ca and exchangeable Mg, Percent Base Saturation and micronutrients. However, it had no significant effect on OC, exchangeable K and exchangeable Na. Comparison of nutrient levels in the soil of the experimental plots before treatment application with post harvesting revealed that liming at every rate increased the soil pH, total N, available P, total exchangeable bases, and base saturation, but decreased the value of exchangeable acidity, organic carbon and the toxic micronutrients compared to the control.  Economically the treatment which yields 4.38t/ha is recommended because its’ marginal rate of return was 122% followed by the treatment that yields 4.69t/ha having 49% marginal rate of return. In the final analysis, the results indicated that judicious utilization of lime at rates higher than the recommended one enhances the nodulation potential and yield of soybean, improves soil acidity, nutrient availability, and soil productivity overall.

Keywords: Soil acidity, Element toxicity, recommended lime Nodulation, yield advantage