Effect of Integrated Use of Lime and Vermicompost on Faba Bean Productivity and Selected Chemical Properties of the Soil in Acid Prone Areas of Ethiopia

Description of the Study Area

The experiment was conducted on station in Farmers Training Center (FTC) at Damotu Kebele of Ejere district as a permanent plot experiment (Figure 1).

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Figure1: Location Map of the Study Area.

Experimental Procedure

A composite soil sample was collected from the surface layer of the whole experimental field before treatment application and from each treatment plot after harvest at a depth of 20 cm for measurement of the major soil properties. Post-harvest soil sampling and analysis were done to examine the residual effect of the organic and inorganic soil acidity amendment on the prescribed soil properties.

Soil Laboratory Analysis

Soil chemical properties were tested using the standard laboratory procedure. The pH of the soil was measured potentiometrically using a pH meter with a combined glass electrode in soil water ratio of 1:2.5 as described by Brady C, et al. [7]. The base titration method which involves saturation of the soil sample with 1M KCl solution and titrating with sodium hydroxide was employed to determine exchangeable acidity as described by Rowell Dl [8]. Organic carbon was determined using the wet oxidation method [9]. The total N content of the soil was determined using the Kjeldahl method [10]. Available soil phosphorus was extracted by the Bray II procedure Bray RH, et al. [11] and determined calorimetrically by spectrophotometer.

Lime and Vermicompost Rating and Fertilization

The materials used as soil acidity ameliorant were vermicompost (VC) and ground limestone of known composition. The amount of lime was determined based on the soil’s exchangeable acidity and bulk density within 0.2cm depth of the soil, a method adapted from Kamprath EJ [12] whereas the quantity of vermicompost was estimated based on its N-equivalency.

Both soil conditioners were applied to a well-prepared experimental plot one month ahead of planting by mixing them with the soil in the plow depth. The planting material used in the experiment was a recently released variety of faba-bean locally known as ‘Gebelicho’.

Treatment and Experimental Design

The experiment comprised ten treatments each with different rates of lime and vermicompost arranged in systematic combination which were laid out as a randomized complete block design (RCBD) with three replications.

Data Collection and Analysis

Agronomic data of the test crops such as plant height, spike length, number of pods per plant, and number of seeds per plant were measured from five plants randomly selected from middle rows of each plot at harvesting whereas biomass and grain yields were recorded from the central rows of each plot. Both soil and crop data were managed using the EXCEL computer software and were subjected to analysis of variance using the General Linear Model of SAS [13]. Treatment means were separated using the Least Significant difference test at an alpha level of 5 %.

Selected Soil Properties before Treatment Application

The results of soil analysis before treatment application are indicated in Table 1. According to the laboratory analytical result, the soil of the study area was sandy clay loam in texture Jones CA [14], very strongly acidic in reaction as rated by Tekalign T [15], and low in Available P which is probably attributed to high P fixing capacity of the soil at the area.

Vermicompost was prepared from crop residues of maize and soya bean, cow dung, and topsoil by using red earthworm (Eisenia fetida). The laboratory analytical result of the vermicompost chemical properties is shown in Table 2. The vermicompost had N and P of (1.51%) and (0.9%) respectively which are rated higher in comparison to that of the soil entity. The vermicompost’s pH was moderately alkaline (8.07) and had organic Carbon (19.67%) and a low C: N ratio (13.73). The contracted C: N ratio of this vermicompost indicates that there is a high potential of mineralization of soil organic matter for the release of nutrients such as N and p, and therefore their availability in soil for plant use.

pH=Power of hydrogen activity; C=Carbon; N=Nitrogen; P=Phosphorus and EC=Electrical conductivity. Table 2: Selected Chemical Properties of the Vermicompost Utilized in the Experiment

Effects of Lime and Vermicompost on Yield and Yield Component of Faba Bean

The result of the study indicated that the number of pods per plant of faba bean was significantly affected by the mutual effect of lime and vermicompost. A blend use of lime and vermicompost resulted in a higher number of pods per plant compared to the control treatment (Table 3). The result also showed that dry biomass yield and seed yield of faba bean were significantly affected by the combined effect of lime and vermicompost. A combination of lime and vermicompost resulted in higher grain yield than that with lime or vermicompost used individually (Table 3). The highest grain yield (2.95 tons/ ha) was recorded from the use of 50% rec.VC + 50% rec. lime + rec. NP that corresponds to 2.6 t ha-1 of vermicompost and 1.3 t ha-1 of lime respectively, which improved the yield significantly and gave a grain yield advantage of 136% over the no input experimental unit. This could be due to the integrated effect of lime and vermicompost that raised the soil pH, reduced the exchangeable acidity (neutralizing the effect of Al and H), enhanced faba bean root performance, complex formation of organic matter with polyvalent metal ions such as Al that in turn affected the solubility and availability of most of the plant nutrients, raised the level of exchangeable base status and improved crop performance. A similar finding was reported in the experiment conducted in the northwestern highland of Ethiopia with similar soil acidity conditions using lime and compost where the combined application marked a faba bean grain yield advantage of 104% obtained from the plot that received 4t/ha of compost and 3.6 t/ha of lime compared to the non-treated control treatment plot [16]. The growth and yield responses to adding lime in the combination might be attributed to the decrease in exchangeable Al3+ content and to an increase in exchangeable Ca2+, and stimulated P nutrition and increased P content in the tissue of faba bean. The yield parameters such as grain per pod, grain yield, straw yield, biological yield, and thousand-grain weights were found to be significantly (P< 0.05) influenced by the application of sole and combined organic and inorganic treatments (Table 3). In the same way Ayodele OJ, et al. [17], suggested that vermicompost enhanced faba bean response to lime and fertilizer application through the improvement in soil pH, available P and exchangeable Ca and Mg, and reduction in Al, Fe and Mn.

Soil Properties after Harvest (Table 4)

The statistical analysis of soil data indicated that application of vermicompost with lime, increase soil nitrogen content of the experimental soil significantly (Table 4). Significant difference of the observed soil fertility status observed in this study pertaining to total nitrogen to the fact that applying lime and compost enhances nutrient mineralization and availability to plant up take. Liming acid soils enhanced release of P from soil and make it readily available for plant uptake which might be due to improved root growth where Al toxicity is alleviated, allowing a greater volume of soil for root elongation. In consent to the present finding Zengeni R, et al. [18] also indicated that indigenous rhizobium numbers is increased with vermicompost application, which serve as a source of C and provide a favorable environment for bacterial multiplication and concluded that the contribution of lime in reducing soil acidity, food and energy derived from VC and the role of P in nodule formation and overall growth of faba bean were the important effects observed from the combination of lime and vermicompost treatments (Figure 2).

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PH=Potential of hydrogen ion, Ex.ac=Exchangeable acidity, OC=Organic Carbon, TN=Total Nitrogen and Av.P= Available Phosphorus Figure 2: Synergetic Effect of Lime and Vermicompost on Soil Chemical Properties.

The application of lime and vermi-compost has increased soil organic carbon (OC) from 1.62% to 1.95% at the rate of rec.VC+50% rec. lime + Rec. NP (Table 4). This value of organic carbon content is medium as per the rating established by Tekalign T [15], OC content of soil. The increment of soil OC in response to lime alone was about 18.3% over the control. The application of Vermicompost also has increase soil OC from 1.53% to 1.86% at the rate of 4.6t VC ha-1 (Table 4), accounting about 21.5% increment over the control. The highest OC recorded from the combined use of lime and VC had witnessed to be superior to the separate effects of lime and vermicompost. Effects of liming and vermicompost application on net mineralization of organic matter has attributed to a reduction of Al toxicity and an increase in soil pH result in an increase of total microbial activity and a release of labile organic matter [19]. Vermicompost used in the experiment might also be a source of soil nitrifiers and decomposers, which can possibly be the reason for significance effects on organic carbon contents of soils [20, 21, 22, 23].