Original Research
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DOI: http://dx.doi.org/10.4314/star.v3i4.6 ISSN: 2226-7522(Print) and 2305-3372 (Online) Science, Technology and Arts Research Journal Sci. Technol. Arts Res. J., Oct-Dec 2014, 3(4): 42-48 Journal Homepage: http://www.starjournal.org/ Original Research Assessment of the Severity of Acid Saturations on Soils Collected from Cultivated Lands of East Wollega Zone, Ethiopia Achalu Chimdi* College of Computational and Natural Sciences, Wollega University, P.O Box: 395, Nekemte, Ethiopia Abstract Article Information The study was conducted during 2014 on acidic soils collected from agricultural lands of Article History: selected Districts of East Wollega Zone and its aim was to determine the status, extents and Received : 12-10-2014 rating of the level acid saturation percentages of the soils of agricultural lands of the study area. Field observation and soil surveys on acidic soils of agricultural lands of the study areas Revised : 23-12-2014 were carried out and then delineated and dug on different landscape positions. Representative Accepted : 28-12-2014 composite soil samples were collected from agricultural fields of the soil surfaces (0-20 cm) Keywords: depth and analyzed at Nekemte and Holleta Soil Research Center Laboratory for soil pH, Aluminum saturation, exchangeable hydrogen, exchangeable acids and bases as well as soil Agricultural fields available and total phosphorus. Laboratory analysis was determined based up on their East Wollega corresponding standard procedures. Data generated were subjected to analysis of variance Exchangeable acids using SAS software version, 9. The results of the study revealed that the soils in the entire agricultural fields of the studied districts of East Wollega Zone are ranged the soil pH(H2O) Aluminum saturation from 4.63 to 6.01 which rated as very strongly acidic at Wayu Tuka to moderately acidic at East Wollega Zone Gida Ayana District. Highest (71.85%) and lowest (17.45%) PAS were recorded in the soils collected from Wayu Tuka and Diga Districts, respectively. The inverse relationship of Acid Saturations exchangeable acidity and PAS with PBS may be attributed to intensive cultivation which leads to the higher exchangeable acidity content in soils collected from Wayu Tuka District than the *Corresponding Author: remaining agricultural fields. The status of soil acidity in almost all the agricultural field of present study are beyond acidity tolerance limit of acid sensitive crops in the area. Therefore, Achalu Chimdi due attention must be given to minimize the severity of Al toxicity of the soils with high PAS in the area, to reinstate intensively cultivated agricultural fields by improving the soil properties E-mail: through crop rotation, returning crop residues to the fields and by using different amendment [email protected] options such as agricultural liming materials. Copyright@2014 STAR Journal. All Rights Reserved. INTRODUCTION Soil acidification is a natural process mainly Due to this acidic nature, most of the soils of the conditioned by naturally acidic parent rocks and leaching highlands of Ethiopia are deficient in inherent available P of base forming ions which attributed to high precipitation. content. Likewise, in most areas of western Oromia Although soil acidity is naturally occurring in some areas, Region, soil acidity and P fixation are the major limiting in many others cases, agricultural practices have factors and serious problems to P-use efficiency and has accelerated the process of soil acidification. Normally, the detrimental influences on the growth performances of acid indication for high soil acidification in the soil solution is sensitive crop production like barley (Achalu et al., associated with the presence of pH levels lower than 5.5 2012b). Because, in acidic soils, plant growth is often and high exchangeable acidity as well as aluminum limited by Al toxicity and this is characterized by marked saturation (Al). When soil pH drops (pH < 5) active form of reduction in shoot and particularly roots growth by Al becomes soluble and results in reduced nutrient preventing the plants from using available soil P uptake. Inadequate crop growth on acid soils is usually a effectively and moreover, nutrients deteriorated land, like direct result of Al saturation. The negative effects of soil the cultivated land may indicate risk to the sustainable acidity on soil biodiversity and crop growth are related to crop production and soil fertility (Curtin and Syres, 2001; the deficiency of major nutrients and the toxicity of Al, Achalu et al., 2012a). Soil acidity due to aluminum toxicity manganese (Mn) and hydrogen (H) ions in the soil to plant is a common problem that has major ramifications for physiological processes. In addition, Differences in land plant growth such as barley, wheat and causes significant use patterns also play a vital role in governing the spatial losses in production, especially in the high rainfall areas of variation in soil physicochemical and biological properties western Oromia. under different land use systems, land productivity, and farming practices (Ahmed, 2002; Achalu et al., 2012a). Now a day, in Ethiopia the problem of soil acidity caused by Al saturation in the high rainfall area has A Peer-reviewed Official International Journal of Wollega University, Ethiopia 42 Achalu Chimdi Sci. Technol. Arts Res. J., Oct-Dec 2014, 3(4): 42-48 become a national issue. In line with this, several studies (1990) classification legend, the main soil group of most of (Wakene and Heluf, 2003; Abdenna , 2013; Achalu et al., the East Wollega areas is Nitisols. Similar to most parts of 2013a-c) have been made on soil p availability, dynamics the country, the economic activities of the local community and fertility status as well as on the properties, and of the study area are primarily mixed farming system that reclamation procedures of soil acidity in some parts of involves crop production and animal husbandry. The Western Oromia highlands. However, the severity of the major crops grown in the area are coffee (Coffee arabica problem of acid saturations on soils collected from L.), teff (Eragrostis tef), barley (Hordeum vulgare L), cultivated lands of the suspect Districts of East Wollega maize (Zea mays L.) and potato (Solanum tubersoum L.) Zone were not yet studied and rated in sufficient detail. hot pepper (Capsicum frutescence) and are usually Most of the Districts of the East Wollega Zone where the produced once in a year under rainfed conditions. Rapid present research study conducted also share these human growth at the study area has resulted in a problems. Therefore, to fill the gap the present study substantial change in land use system and most natural explored the severity of acid saturation the agricultural forest has been cleared for crop production and local fuel. lands and its extents as well as rating of the acid These environmentally unfriendly farming practices and saturation percentages of the soil of the selected Districts the high rainfall amounts have exposed the soils of the of East Wollega Zone. study areas to severe erosion resulting in nutrient loss, soil acidity and overall land and natural resource MATERIALS AND METHODS degradation. As a result, most of the crops which are General Description of the Study Area susceptible to soil acidity like barley, bean, and wheat are The study was conducted in the Districts of East forced to be out of production in the region (Fite et al., Wollega Zone of Oromia Regional State, western 2007; Achalu et al., 2012b). highlands of Ethiopia (Figure 1). According to the FAO Figure 1: General location map of the study area Site Selection, Soil Sampling and Preparation solution at pH 7. The extracts of Ca and Mg ions were Preliminary survey and field observation was carried determined using AAS while K and Na were determined out. Based on field observation and soil surveys, acidic by flame photometer. To determine the cation exchange soils of agricultural land was delineated and dug on capacity (CEC), the soil samples were first leached with 1 different landscape positions and then samples was M NH4OAc, washed with ethanol and the adsorbed collected from the soil surfaces (0-20 cm) depth. Then ammonium was replaced by Na (Chapman, 1965). The composite sample (after being well mixed in a bucket) of CEC was then measured titrimetrically by distillation of about 2 kg of the mixed sub-samples (composite sample) ammonia that was displaced by Na following the micro- was properly bagged, labeled and transported to the Kjeldahl procedure. Total exchangeable acidity was laboratory for analysis of acidity related soil chemical determined by saturating the soil samples with 1M KCl properties. solution and titrated with 0.02M HCl as described by Rowell (1994). From the same extract, exchangeable Al in Laboratory Analysis of Soil Samples the soil was titrating and analyzed using with a standard The soil pH was measured potentiometrically with a solution of 0.02M HCl and finally percent Al saturation digital pH meter in the supernatant suspension of 1:2.5 was calculated from the ratio of exchangeable Al to the soils to water ratio (Baruah and Barthakur, 1997). Soil CEC as a percent. The soil percent base saturation (PBS) available P was extracted by the Bray-II method (Bray and was calculated from sum of the basic exchangeable Kurtz, 1945) and quantified using spectrophotometer cations (Ca, Mg, K and Na) as the percentage of CEC. (wave length of 880 ηm) colorimetrically using From the composite soil samples total P was determined vanadomolybedate acid as an indicator. The soil electrical using perchloric acid digestion method as described by conductivity measurement was done using a conductivity (Kuo, 1996). Available P was analyzed using Bray-II meter at 25ºc using its standard procedures. method colorimetrically using vanadomolybedate acid as an indicator and its concentration was measured using Exchangeable basic (Ca, Mg, K and Na) ions were spectrophotometer at a wave length of 880nm.