Extent, Distribution, and Causes of Soil Acidity under Subsistence Farming System and Lime Recommendation: The Case in Wolaita, Southern Ethiopia

Soil acidity is one of the most important environmental threats to the Ethiopian highlands where the livelihood of the majority of people is reliant on agriculture. Yet, information regarding its extent, distribution, causes, and lime requirement at a scale relevant to subsistence farming systems is still lacking. This study (1) investigates the extent and spatial distribution of soil acidity, (2) identifies factors attributing to soil acidification, and (3) predicts the lime requirement for major crops. A total of 789 soil samples were collected from arable lands in the Wolaita area which is mainly characterized by poor soil fertility and soil degradation in southern Ethiopia. Results revealed that the landscape is characterized by a gentle slope followed by strongly sloppy > flat > hilly topographies. Clay is the dominant soil textural class. A soil pH map, which is generated using geospatial analysis, demonstrates that 3.3, 78.0, and 18.7% of the total area were under strongly acidic, moderately acidic, and neutral soil reactions, respectively. The exchangeable acidity (Cmol(+)/kg) varied from nil to 5.1, whereas exchangeable Al ranged from 1.4 to 19.9 Cmol(+)/kg. The soil pH has shown a significantly ( p < 0.001) negative association with clay content (r = −0.33), exchangeable Al (r = −61), exchangeable acidity (r = −0.58), and inorganic fertilizer application (r = −0.33). Increased rates of diammonium phosphate (DAP) (r2 = 0.91) and urea (r2 = 0.88) markedly elevated soil acidity. Conversely, manuring showed a significant ( p < 0.001) and positive relationship with pH (r = 0.37) in which the increasing rate of manure significantly reduced acidification (r2 = 0.98). DAP and urea applications above 75 kg/ha lowered soil pH units by 0.56 and 0.48, respectively, <25 kg/ha while at the same time farmyard manure (FYM) at 4 t/ha raised pH by 0.75 units over the unfertilized field. Residue management significantly ( p < 0.001) influenced soil pH wherein it ranged from 6.09 (complete residue removal) to 6.61 (residue incorporation). Changes in land use, cropping intensity, and socioeconomic status were also significantly attributed to soil acidification. To curb the effects of soil acidity, the lime requirement for common bean growing fields varied from zero to 6.6 t/ha, while for maize it was between zero and 4.3 t/ha. It is concluded that soil management interventions such as maintaining and incorporating crop residues, integrated use of organic and inorganic fertilizers, liming, and enhancing farmers’ awareness should be advocated to overcome soil acidification and improve soil fertility. In addition, introducing crops with traits that tolerate acidity and Al toxicity is also suggested.

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Changes in Soil Phosphorus Pools and Chemical Properties under Liming in Nitisols of Farawocha, South Ethiopia

Applied and Environmental Soil Science ◽

10.1155/2021/5518545 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Fikeremareyam Chulo ◽

Fanuel Laekemariam ◽

Alemayehu Kiflu

Keyword(s):

Soil Ph ◽

Nutrient Dynamics ◽

Soil Phosphorus ◽

Acid Soil ◽

Chemical Properties ◽

Soil Chemical Properties ◽

Southern Ethiopia ◽

Organic Part ◽

Exchangeable Acidity ◽

P Pools

Understanding the nutrient dynamics in acid soil is fundamental to carry out proper management. The study was conducted to investigate phosphorus (P) pools and selected properties under different rates of lime for acid nitisols of Farawocha, Southern Ethiopia. Four lime rates incubated for a month in three replications were tested. The lime rates were 0 t/ha (0%), 5.25 t/ha (50%), 10.5 t/ha (100%), and 15.75 t/ha (150%). Lime requirement (LR) for 100% was calculated targeting soil pH of 6.5. Data on the P pools such as soluble P (P-sol) and bounded forms of P with iron (Fe-P), aluminum (Al-P), calcium (Ca-P), organic part (Org-P), residual P (Res-P), and total of P fractions were measured. In addition, changes in soil chemical properties such as pH, exchangeable acidity, calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), copper (Cu), boron (B), zinc (Zn), and manganese (Mn) were analyzed. The result showed that total P was 357.5 mg/kg. Compared to nontreated soil, liming at a rate of 15.75 t/ha significantly improved P-sol (34.2%, r2 = 0.88), Ca-P (61.6%, r2 = 0.92), and Res-P (195%, r2 = 0.94); however, it reduced Fe-P (58.5%, r2 = −0.83), Al-P (71%, r2 = −0.97), and Org-P (19.1%, r2 = 0.93). Overall, the P-associated fractions in the soil, regardless of the lime rates, were in the order of Org_P > Res_P > Fe_P > Ca_P > Al_P > P-sol. Liming raised soil pH by 2.1 units (4.5 to 6.6) over nonlimed soil, whereas it reduced exchangeable acidity from 4.18 to 0.23 meq/100 g soil. Available P, Ca, Mg, S, Cu, Zn, and B contents were significantly improved with lime application. However, liming reduced Fe and Mn contents. In conclusion, these findings showed that liming facilitated the release of P from various pools, modified pH and exchangeable acidity, and resulted in beneficial changes for most of the soil chemical properties.

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Crop Response to Soil Acidity Factors in Ultisols and Oxisols in Puerto Rico. XII. Tomatoes

The Journal of Agriculture of the University of Puerto Rico ◽

10.46429/jaupr.v69i3.7362 ◽

1969 ◽

Vol 69 (3) ◽

pp. 357-365

Author(s):

Edmundo Rivera ◽

José Rodríguez ◽

Fernando Abruña

Keyword(s):

Puerto Rico ◽

Cation Exchange ◽

Soil Ph ◽

Cation Exchange Capacity ◽

Soil Acidity ◽

Exchange Capacity ◽

Crop Response ◽

Exchangeable Al

The effect of acidity factors of two Ultisols and one Oxisol on yield and foliar composition of tomatoes was determined. Yields were not markedly reduced by acidity in the Ultisols until pH dropped to around 4.6 with 45% Al saturation of the cation exchange capacity (CEC), and no yield was produced at about pH 4.1 and 80% Al saturation. In the Oxisol, tomato yields dropped steadily from 39.7 t/ha, when there was no exchangeable AI, to 17.5 t/ha at the highest level of acidity, pH 4.4 and 43% AI saturation. In all soils, yields were closely correlated with soil pH, exchangeable Al and Ca and Al/Ca.

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Effect of Farmyard Manure, Lime and Inorganic Fertilizer Applications on Soil pH, Nutrients Uptake, Growth and Nodulation of Soybean in Acid Soils of Western Kenya

Journal of Agricultural Science ◽

10.5539/jas.v10n4p199 ◽

2018 ◽

Vol 10 (4) ◽

pp. 199 ◽

Cited By ~ 2

Author(s):

Hillary M. O. Otieno ◽

George N. Chemining’wa ◽

Shamie Zingore

Keyword(s):

Soil Fertility ◽

Nutrient Uptake ◽

Soil Ph ◽

Block Design ◽

Farmyard Manure ◽

Control Treatment ◽

Nodule Formation ◽

Higher Plant ◽

Inorganic Fertilizers ◽

Western Kenya

Soybean is an important crop with nutrition, economic and soil fertility improvement benefits to farmers. However, its production in western Kenya is partly constrained by low soil pH and soil fertility levels. A greenhouse pot study was conducted to evaluate the effects of inorganic fertilizers, farmyard manure and lime application on soil pH, nutrient uptake, growth and nodulation of soybean grown in acidic soils from western Kenya. The experiment was set up in a randomized complete block design with eight treatments: control; NPK; manure; lime; manure+lime; NPK+manure; NPK+lime and manure+lime+NPK. Significant effects of inorganic fertilizers, manure and lime applications were observed on all the variables. Manure, lime and manure+lime treatments increased soil pH by 1.33, 2.19 and 2.28, respectively, above the control treatment. The shoot N was lower under control (1.71-1.81%), NPK (1.85-1.98%) and manure (2.00-2.11%) than under all other treatments. Treatments NPK+lime and manure+lime+NPK recorded higher uptake of P and K nutrients than all other treatments. The control and NPK treatments recorded shorter plants and low leaf area and above-ground biomass compared to other treatments. The NPK+lime and manure+lime+NPK treatments recorded higher plant height and aboveground biomass than other treatments. Lime+manure treatment recorded highest nodule numbers and dry weights per plant. Positive relationships were observed between pH and N, P and K nutrient uptake (R2 ranged between 0.30 and 0.77) and between biomass and N, P and K nutrient uptake (R2 ranged between 0.68 and 0.99). From this study, use of manure and lime could result in improved soil pH for better uptake of nutrients, nodule formation and productivity of soybean in Western Kenya.

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Temporal variation in soil acidity

Soil Research ◽

10.1071/s97022 ◽

1997 ◽

Vol 35 (5) ◽

pp. 1115 ◽

Cited By ~ 21

Author(s):

M. K. Conyers ◽

N. C. Uren ◽

K. R. Helyar ◽

G. J. Poile ◽

B. R. Cullis

Keyword(s):

Temporal Variation ◽

Soil Ph ◽

Soil Acidity ◽

Soil Depth ◽

Weather Conditions ◽

Climatic Conditions ◽

Variable Response ◽

Related Factors ◽

Exchangeable Al ◽

Eastern Australia

Seasonal variation in the response of crops and pastures to limestone application has been observed on acidic soils in south-eastern Australia. Our hypothesis was that temporal variation in soil acidity related factors may contribute to this variable response. Soils from 4 annual pasture sites were sampled at least monthly for 3 years during 1988–1990 to monitor changes in pH(CaCl2) and in concentrations of exchangeable aluminium (Al) and manganese (Mn). The sites received no fertiliser or cultivation and therefore allowed for the estimation of natural temporal variation. Temporal variation in soil pH during a year ranged from 0 to 0·45 pH units depending on the site, soil depth, and the weather conditions. The larger changes in soil pH were associated with more extreme climatic conditions than normal, e.g. following the break of season after a hot, dry summer (autumn 1988) or during periods of above-average rainfall in autumn and early spring (1990). Temporal variation in pH was less than the spatial variability at the sites but greater than the long-term net acidification rate reported for the region. Temporal variation in the concentration of exchangeable Al ranged from 0 to 0·4 cmol(+)/kg during a year and varied primarily with the inverse of pH. Variations in the concentration of exchangeable Mn ranged from 0·05 to 0·35 cmol(+)/kg during a year. The concentration of exchangeable Mn increased over summer to an extent dependent on the drying of the soil. At the 2 sites with duplex profiles, maxima in the concentration of exchangeable Mn also occurred in spring, particularly in the warm wet spring of 1990. Soil tests for soil acidity therefore represent guides to probable risks of toxicity, as pH and the concentrations of exchangeable Al and Mn may change between soil sampling, sowing, and the period of crop or annual pasture growth. Such variations will alter the responsiveness of crops and pastures to lime.

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Fertility Status of Acid Soils under Different Land Use Types in Wolaita Zone, Southern Ethiopia

Applied and Environmental Soil Science ◽

10.1155/2020/3713967 ◽

2020 ◽

Vol 2020 ◽

pp. 1-9

Author(s):

Mesfin Kassa Cholbe ◽

Fassil Kebede Yeme ◽

Wassie Haile Woldeyohannes

Keyword(s):

Land Use ◽

Soil Acidity ◽

Acid Soil ◽

Acid Soils ◽

Southern Ethiopia ◽

Land Use Type ◽

Grazing Land ◽

Exchangeable Acidity ◽

Fertility Status ◽

Land Use Types

Information on soil fertility status of acid soil of a particular area as affected by land use type is important for developing sound soil management systems for improved and sustainable agricultural productivity. The main objective of this study was to assess the fertility status and effect of land use change on soil physicochemical properties. In this study, adjacent three land use types, namely, enset-coffee, crop, and grazing land use were considered in four districts (i.e., Bolos Sore, Damot Gale, Damot Sore, and Sodo Zuria) of Wolaita Zone, southern Ethiopia. Soil samples were collected from a depth of 0–20 cm from each land use type of the respective districts for physicochemical analyses. The results showed that land use types significantly affected ( P ≤ 0.05 ) soil properties such as bulk density, available P, exchangeable potassium, exchangeable acidity, exchangeable bases (Na, K, Ca, Mg), exchangeable acidity, and CEC. Besides, soil pH, OC, and TN were influenced significantly ( P ≤ 0.05 ) both by districts and land use types. The very strongly acidic soils were found predominantly in the crop and grazing lands whereas a neutral acidity level was found in the enset-coffee land use type of four districts. In conclusion, the study proves that land use type change within the same geographic setting can affect the severity of soil acidity due to over cultivation and rapid organic matter decomposition. Finally, the study recommends an in-depth study and analysis on the root causes in aggravating soil acidity under crop and grazing land use types.

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Long-term acidification of a Brazilian Acrisol as affected by no till cropping systems and nitrogen fertiliser

Soil Research ◽

10.1071/sr07088 ◽

2008 ◽

Vol 46 (1) ◽

pp. 17 ◽

Cited By ~ 22

Author(s):

F. C. B. Vieira ◽

C. Bayer ◽

J. Mielniczuk ◽

J. Zanatta ◽

C. A. Bissani

Keyword(s):

Soil Ph ◽

Soil Acidification ◽

Plant Material ◽

Cropping Systems ◽

Maize Yield ◽

Mineral N ◽

No Till ◽

Leguminous Species ◽

Exchangeable Al ◽

C Cycle

Cropping systems and N fertilisation affect soil acidification mainly due to the removal of alkaline plant material from the field and nitrate leaching. The study evaluated the acidification of a subtropical soil under no till cropping systems with different C and N addition rates for 19 years. The contributions of leguminous and non-leguminous crops (fallow/maize, black oat/maize, black oat + vetch/maize, black oat + vetch/maize + cowpea, lablab + maize, pigeon pea + maize, and digitaria) and mineral N fertiliser (0 and 180 kg N/ha.year as urea) to total acidification were estimated. Cropping systems and N fertilisation significantly affected soil pH, which ranged from 4.3 to 5.1. The presence of leguminous species and mineral N promoted greater decreases in soil pH and net soil acidification, which resulted in increases in exchangeable Al content and Al saturation. Black oat + vetch/maize with N fertilisation promoted the highest soil net acidification rate (2.65 kmol H+/ha.year), while digitaria had the lowest (1.07 kmol H+/ha.year). Leguminous species and N fertilisation increased soil acidification through changes in the C cycle associated with the removal of alkaline plant material by grains. Leguminous-based cropping systems promoted higher maize yields than those comprising essentially gramineous species, indicating an opportunity for a reduction in N fertiliser rates. With N application, however, maize yield did not differ among cropping systems, despite differences in soil pH and exchangeable Al.

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Effect of Soil pH and Related Acidity Factors on Yields of Sweetpotatoes and Soybeans Grown on Typical Soils of the Humid Tropics

The Journal of Agriculture of the University of Puerto Rico ◽

10.46429/jaupr.v61i1.10482 ◽

1969 ◽

Vol 61 (1) ◽

pp. 82-89

Author(s):

Raúl Pérez-Escolar

Keyword(s):

Puerto Rico ◽

Soil Ph ◽

Soil Acidity ◽

Humid Tropics ◽

Soybean Yield ◽

Base Content ◽

Exchangeable Al ◽

Soybean Leaf ◽

Leaf N Content ◽

Leaf N

The effects of soil pH and related acidity factors on the yields of sweetpotatoes, Miguela var., and soybeans, Jupiter var., were determined on typical Oxisols and Ultisols of Puerto Rico. The study revealed no significant effect of pH and acidity factors on the yield of the sweetpotato variety, which was quite tolerant to high soil acidity and exchangeable Al. Yields were similar to those obtained by other researchers who worked with other varieties. Soybeans, although relatively tolerant to high levels of exchangeable Al, were adversely affected when values surpassed 5.5 meq/100 g of soil in a clayey Ultisol. Exchangeable base content was directly related to soybean yield grown on a light textured Oxisol. Yields obtained are considered excellent. Highly significant correlations between soybean leaf N content and yield was found in the clayey Ultisol.

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Rising levels of soil acidity in Meghalaya: Evidences and Imperatives

ANNALS OF PLANT AND SOIL RESEARCH ◽

10.47815/apsr.2021.10073 ◽

2021 ◽

Vol 23 (3) ◽

pp. 297-303

Author(s):

MANOJ KUMAR ◽

Keyword(s):

Soil Acidity ◽

Principal Component ◽

Northeast India ◽

Mean Value ◽

Current Status ◽

Acidic Soils ◽

Exchangeable Acidity ◽

Exchangeable Al ◽

Eigen Values ◽

Garo Hills

In order to examine the current status of soil acidity in Meghalaya, representative soil samples (n= 497) were collected (during 2015-2016) from across the state and analyzed for soil acidity and associated parameters. Averaged across the samples, pH of the soils was found to be very strongly acidic (4.94). Nearly 20 % of the soils had pH below 4.50, 59% below pH 5.0 and 80% below pH 5.50. Only 3.4% of the samples recorded pH more than 6.0. East Khasi Hills District had the maximum percentage (95.1%) of strongly acidic soils (pH ≤ 5.50) while Garo Hills had the least (50.2%). All other districts recorded more than 85% of the strongly acidic soils. Average exchangeable acidity, exchangeable Al and effective CEC were found to be 1.60, 1.27 and 3.86 meq/100g soil, respectively. Mean base saturation was recorded below 60%. Aluminium saturation (percentage of effective CEC being occupied by exch. Al) ranged from 1.5 to 79.7% with its mean value being as high as 33%. Principal component analysis provided three PCs with Eigen values >1 and together they explained 83.2 % of the variance in total dataset. The soil acidity in Meghalaya is on rise, with 80.2% of its soils being strongly acidic (pH ≤ 5.50) in contrast to the previous reports of 53% soils being strongly acidic. This calls for widespread adoption of soil acidity ameliorative measures in agriculture of Meghalaya, Northeast India.

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Optimisation of Charcoal and Sago (Metroxylon sagu) Bark Ash to Improve Phosphorus Availability in Acidic Soils

Agronomy ◽

10.3390/agronomy11091803 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1803

Author(s):

Prisca Divra Johan ◽

Osumanu Haruna Ahmed ◽

Ali Maru ◽

Latifah Omar ◽

Nur Aainaa Hasbullah

Keyword(s):

Soil Ph ◽

Soil Acidity ◽

P Availability ◽

Acidic Soils ◽

Inorganic P ◽

Exchangeable Acidity ◽

P Fixation ◽

Metroxylon Sagu ◽

Sago Bark ◽

Fe Ions

Soil acidity is an important soil factor affecting crop growth and development. This ultimately limits crop productivity and the profitability of farmers. Soil acidity increases the toxicity of Al, Fe, H, and Mn. The abundance of Al and Fe ions in weathered soils has been implicated in P fixation. To date, limited research has attempted to unravel the use of charcoal with the incorporation of sago (Metroxylon sagu) bark ash to reduce P fixation. Therefore, an incubation study was conducted in the Soil Science Laboratory of Universiti Putra Malaysia Bintulu Sarawak Campus, Malaysia for 90 days to determine the optimum amounts of charcoal and sago bark ash that could be used to improve the P availability of a mineral acidic soil. Charcoal and sago bark ash rates varied by 25%, whereas Egypt rock phosphate (ERP) rate was fixed at 100% of the recommendation rate. Soil available P was determined using the Mehlich 1 method, soil total P was extracted using the aqua regia method, and inorganic P was fractionated using the sequential extraction method based on its relative solubility. Other selected soil chemical properties were determined using standard procedures. The results reveal that co-application of charcoal, regardless of rate, substantially increased soil total carbon. In addition, application of 75% sago bark ash increased soil pH and at the same time, it reduced exchangeable acidity, Al3+, and Fe2+. Additionally, amending acidic soils with both charcoal and sago bark ash positively enhanced the availability of K, Ca, Mg, and Na. Although there was no significant improvement in soil Mehlich-P with or without charcoal and sago bark ash, the application of these amendments altered inorganic P fractions in the soil. Calcium-bound phosphorus was more pronounced compared with Al-P and Fe-P for the soil with ERP, charcoal, and sago bark ash. The findings of this study suggest that as soil pH decreases, P fixation by Al and Fe can be minimised using charcoal and sago bark ash. This is because of the alkalinity of sago bark ash and the high affinity of charcoal for Al and Fe ions to impede Al and Fe hydrolysis to produce more H+. Thus, the optimum rates of charcoal and sago bark ash to increase P availability are 75% sago bark ash with 75%, 50%, and 25% charcoal because these rates significantly reduced soil exchangeable acidity, Al3+, and Fe2+.

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Impact of organic and mineral fertilising on aluminium mobility and extractability in two temperate Cambisols

Plant Soil and Environment ◽

10.17221/587/2019-pse ◽

2019 ◽

Vol 65 (No. 12) ◽

pp. 581-587 ◽

Cited By ~ 1

Author(s):

Jiří Balík ◽

Martin Kulhánek ◽

Jindřich Černý ◽

Ondřej Sedlář ◽

Pavel Suran

Keyword(s):

Sewage Sludge ◽

Soil Ph ◽

Farmyard Manure ◽

Close Correlation ◽

Control Treatment ◽

Aluminium Content ◽

Mobile Forms ◽

Exchangeable Al ◽

Positive Correlations

Different fertilisation systems cause changes in the content of mobile aluminium (Al) forms in the soil as a result of soil pH changes. Long-term stationary fertilisation experiments established in 1996 at 2 sites were evaluated. Experiments consisted of unfertilised control treatment and 6 other treatments, combining mineral fertilisation with the application of farmyard manure, sewage sludge and straw. To record the changes in mobile Al forms, we used 5 extraction procedures with agents: water, CaCl2, KCl, CaCl2/DTPA (CAT) and Mehlich 3 solutions. At treatment nitrogen (N) + straw, topsoil acidification was observed, resulting in the increased content of mobile Al. At treatments with mineral fertilisation (N, NPK), increased content of mobile forms of Al was recorded. Application of cattle manure and sewage sludge helped to stabilise the soil pH and reduce mobile Al forms. The close correlation between the methods determining the exchangeable Al (CaCl2 and KCl solutions) was observed; however, KCl extraction was more favourable in soils of low Al extractability, as the amount of extracted Al was 3–4 times higher. Positive correlations were determined between Al extracted by Mehlich 3 solution and the content of exchangeable Al. The less frequently used CAT method also turned out to be perspective for mobile Al determination. Furthermore, aluminium content determined in Mehlich 3 extract was compared with mobile phosphorus amounts in H2O, CAT and Mehlich 3, respectively. All three investigated phosphorus forms showed significantly negative correlations with Al.

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