Understanding Soil Acidification: Main Causes And Remedial Measures

Causes of soil acidification

Soil acidification is the accumulation of hydrogen cations that are also known as protons. Soil becomes acidic when the pH level decreases to the normal level of 5.5. Chemically, soil acidification occurs when proton donor added in the soil. This donor can be sulphuric acid as well as nitric acid. The aim of the paper is to understand the concept of soil acidification. It is caused by various reasons (Webb, Nelson, Banabas and Nake, 2015). The main cause of soil acidification is decrease in the level of pH and excess rainfall. Further, the discussion is carried on the main causes of soil acidification. Due to the soil acidification, water as well as food quality is being compromised. In addition, it is also affecting health of the people. By taking this approach, environmental problems from the soil acidification has been discussed. Various techniques can be adopted to reduce the level of soil acidification. In this way, the discussion is ends by providing measures to reduce the level of soil acidification. 

A natural process that is enhanced either by human activities and plants or by slowing down careful management practices. Mining as well as industrial activities lead to the acidification in soil. It is made-up of hydrogen cations that are also called “Protons.” It occurs when proton donor added to the soil. Donor is an acid such as sulphuric acid or nitric acid. These two acids are mechanisms of acid rain (Tian and Niu, 2015).

Acidification also happens when base cations such as magnesium, sodium, calcium, or potassium that leached in front of the soil. This leaching also increases due to increase in precipitation. Acid rain rushes the leaching of these alkali elements. After this, plants utilise all the alkali elements as soon as grow. As a result, when plant material is removed, a crop is harvested or forest is logged, the base elements that are taken by them are lost from the soil permanently. In addition to this, acidification also occurs from the emission of nitrogen from air as nitrogen end by depositing into soil (Lu, Mao, Gilliam, Luo and Mo, 2014).

It has now become a major economic and environmental concern. In order to prevent the soil acidification, there must be 5.5 pH level. However, in Australia agriculture land is less than or equal to 5.5 pH value that is causing acidification in soil. Besides this, subsurface acidity is already a serious problem in New South Wales and Western Australia. Acid in soil puts significant loss in the production and where the choices of acid is limited to acid tolerant spices and varieties, the opportunities for profitable market is reduced (Chen, Li, Lan, Hu, and Bai, 2016).

Types of acidity

There are two types of acidity. The one type of acidity is Active acidity on the other hand Exchange acidity is second type of acidity. Active acidity is developed due to the aluminium and hydrogen. In this, the magnitude of the acidity is somewhat limited. Exchange acidity is developed due to the absorbed aluminium or hydrogen on the soil colloids. In this, magnitude of acidity is too high.

Usually soil acidification occurs naturally by slow process when soil is weathered but the process is

• Soil acidification is caused by the discharge of protons during the cycling or transformation of carbon. The acidification that is caused by these processes can put adverse impacts where soil is unable to shield against decrease in pH. For example- in some parts of Australia, incessant cultivation as well wrong use of N fertilizer has produced sufficient soil acidity.
• Increase in the deliberation of hydrogen ions in the soil also causes soil acidification. The same is due to the inefficient use of nitrogen.
• Large amount of rainfall becomes acidic as the water reaches in the basic cations (such as sodium, magnesium, potassium, or calcium) out of the soil profile and as a result, these cations are further replaced by acidic cations.
• The soil parent material from which soil is developed is a source of acidity in soil.
• Leaching and rainfall- excessive rainfall as well as leasing of nitrate nitrogen causes the acid in soil. Generally, acidity in soil are common in all those regions where rainfall is high enough to percolate considerable amount of exchangeable bases from the surface soil and some compounds of Fe and Al remains in soil. The nature of these compounds are acidic and its hydroxide and oxide react with water that is H2O and release H+ (hydrogen) in soil solution and soil becomes acidic (Government of Western Australia, 2018).
• Ammonium fertilisers are major contributor of soil acidification. Nitrogen in agriculture system either fixed by legumes or decomposed from the soil organic matter (remaining dead portion of animals or plants) added in various types of fertiliser. Different nitrogen fertilizers follows some different path when they breakdown in the soil which in turn contribute various amount of acid to the soil.
• As soil contains high level of CO2, the pH value of this type of soil will be low. Due to the low level of pH, soil becomes acidic. Metabolism and root activity also serves as a source of CO2 that helps the soil to become more acidic.
• Export of food and fibre from the firm is also another cause of soil acidity. In agriculture, if plant material is removed by harvest, grazing, or relocated by application of dung into the stock camps rather then returning into the soil. As a result, alkalinity occurs and hydrogen remains in the soil that contributes soil acidity. For more time, if this process is repeated, soil becomes acidic (Fujii, 2014).

Soil acidification put various effects on environment that are as follows:

1. Plants growth- Soil acidification also affects the plant. The acidic soil makes it difficult for the plants to attain the needed nutrients. Due to the soil acidification, a plant does not able to grow properly which further affects the quality of crops when it is produced. Due to the slow growth of plant, it is not able to produce the desired output (Wachman, 2018). Due to decrease in production capacity of soil, its growth get affected which in turn lead to slower growth. When soil becomes acidify, level of calcium, potassium, magnesium depletes. As a result, quality of soil fertility also decreased.

1. Degradation of food quality- When the level of soil is below the normal level of pH, soil gets acidify. All the output that is produced through that acidifies soil harms the productivity and quality of food. In this way, when the soil is acidifying, it decreases the quality of food. Due to the bad quality of output, food quality also decreases which in turn affect those who all are consuming the food from acidifying soil. Due to low level of magnesium and potassium in acidify soil, various health problems occur such as grass tenaty and milk fever.

1. Production quantity- soil acidification decreases the quality of production. Due to the acidification of soil, production capacity of soil seeds decreases. It is obvious that acidity in soil leads to decrease the production capacity of soil. When the soil was natural, it was able to produce more output with best quality of grains (Zhu, Chen,  Xu, Zhu and Huang, 2016). As soon as, acid get dissolve in food, it decreases the production capacity of soil. However, if soil acidity is not under sufficient level, then there will be more chance of less production.

1. Pollution of water reservoir- In order to increase the fertility and productivity of soil, it is feeded by water. If the soil itself is acidic, water that is feeded by famers or any person also becomes acidic. Animals and living beings therefore consume the water through consuming surface water or underground water. Due to the increasing soil acidification, water is also polluted (Soil Quality, 2018). Due to this, various diseases are also spreading among the people and animals. If water is mixed in acidify soil, it generates various diseases in the human body.

1. Human health- Soil acidification is not only limited to the farming areas. In urban areas, soil is polluted with organic chemicals from industrial activities, medicines, coal burning. These things are dissolved in soil that pollutes the crops that is further taken by the human beings. The intake of the acid foods and fruits puts various negative impacts on the health of human being. Due to this, human being comes in the contact of various diseases that is sometimes hard to recover.

• Soil testing- It is way to measure the amount of acidic contents in soil. Soil samples are required to taken when soil becomes dry. It is a tool to measure the level of pH using one part soil to five parts 0.01 M CaCl2 Soils with low salt start showing long seasonal variations in pH if it is measures using water. Soil sampling should consider the paddock variability. Samples should be taken at the surface in order to determine a level of pH in soil profile. As a result, it will detect the acidity by increase the level of pH in soil. Samples are required to locate properly to allow the monitoring. Sampling should be repeated in every three to four years to identify the changes and make adjustments of management practices.
• Liming- It is the best economic method of improving the soil acidity. The total amount of required lime will depend on the lime quality, soil pH profile, rainfall, and soil type as well as farming system. The key factor in lime quality is particle size and neutralising value. The defusing value of lime is articulated as proportion of pure calcium carbonate whose value is 100%. With more neutralising value, less time can be used for the same pH change. With the high percentage of small particles, lime will retort faster to neutralise the amount of acid in the soil that will be beneficial(Goulding, 2016).
• Interpreting pH results- Depending on the result of pH test, agriculture lime is either applied to preserve pH or to recover pH to a level of appropriateness. If the top soil level of pH is beyond 5.5 and the subsurface level of pH is above 4.8, then maintenance level of liming is required to counter the acidification that is caused by productive agriculture. If the level of pH in topsoil is low than 5.5, then liming us recommended. If the 10-20 cm layer is below the 4.8 but the 20-30 cm layer is above the 4.8, then also liming is required (Hazelton, and Murphy, 2016).
• Complementary management strategies- If the level of pH is low in soil, varieties of pasture and crops can proved to be helpful. By using these tolerant species, impact of soil acidity reduces to some extent. As this is not a permanent solution, because without the liming treatment, soil remain acidic (Mamo and Shapiro, 2017).

Various management practices can reduce the soil acidification. In high rainfall areas, managing nitrogen fertiliser input in order to reduce nitrate leaching is essential. In addition, less acidifying options in rotation is also helpful.

Conclusion

In the limelight of above discussion, it can be concluded that soil acidification is one of the major problem now a days. It is a measure of the hydrogen ions in the soil. The major reason for the soil acidity is the lower level of pH in soil substances. The minimum level of pH is above the 5.5 in the topsoil and 4.8 in the subsurface. In addition, inappropriate use of nitrogen also increases the acidity in the soil.

Soil acidification provides various problems in the environment. Due to this, plant growth reduces which is not able to generate sufficient output. As a result, health of people is getting affected. In order to minimise the soil acidification, it becomes necessary to act appropriately. Soil testing is necessary tool to check the level of pH in the soil. Time-to-time check of PH level in spoil is necessary to assure the soil quality. In addition, liming is also beneficial for reducing the soil acidification. It is one of the most economical method for soil testing.

References

Fujii, K. (2014) Soil acidification and adaptations of plants and microorganisms in Bornean tropical forests. Ecological research, 29(3), pp.371-381.

Goulding, K.W.T. (2016) Soil acidification and the importance of liming agricultural soils with particular reference to the United Kingdom. Soil use and management, 32(3), pp.390-399.

Government of Western Australia. (2018) Causes of soil acidity. [online] Available from: https://www.agric.wa.gov.au/soil-acidity/causes-soil-acidity [accessed 7/10/18].

Government of Western Australia. (2018) Effects of soil acidification. [online] Available from: https://www.agric.wa.gov.au/soil-acidity/effects-soil-acidity?page=0%2C2 [accessed 9/10/18].

Hazel, D., Li, J., Lan, Z., Hu, S. and Bai, Y. (2016) Soil acidification exerts a greater control on soil respiration than soil nitrogen availability in grasslands subjected to long?term nitrogen enrichment. Functional Ecology, 30(4), pp.658-669.

Hazelton, P. and Murphy, B. (2016) Interpreting soil test results: What do all the numbers mean?. CSIRO publishing.

Lu, X., Mao, Q., Gilliam, F.S., Luo, Y. and Mo, J. (2014) Nitrogen deposition contributes to soil acidification in tropical ecosystems. Global change biology, 20(12), pp.3790-3801.

Mamo, M., and Shapiro, C. A. (2017) Management Strategies to Reduce the Rate of Soil Acidification. United Kingdom: Routledge.

Soil Quality. (2018) Fact sheets Soil Acidity. [online] Available from: https://soilquality.org.au/factsheets/soil-acidity [accessed 8/10/18].

Soil Victoria. (2017) Understanding soil acidity. [online] Available from: https://agriculture.vic.gov.au/agriculture/farm-management/soil-and-water/soils/acid-soils [accessed 8/10/18].

Tian, D. and Niu, S. (2015) A global analysis of soil acidification caused by nitrogen addition. Environmental Research Letters, 10(2), p.024019.

Wachman, M. (2018) How Does the Acidity of Soils Affect Plant Growth?. [online] Available from: https://www.ehow.com/about_5531587_acidity-soils-affect-plant-growth.html [accessed 9/10/18].

Webb, M.J., Nelson, P.N., Banabas, M. and Nake, S. (2015) Soil acidification and indicators. United Kingdom: Routledge.

Zhu, H., Chen, C., Xu, C., Zhu, Q. and Huang, D. (2016) Effects of soil acidification and liming on the phytoavailability of cadmium in paddy soils of central subtropical China. Environmental pollution, 219, pp.99-106.