RATIONALE
Soil pH is the measure of the concentration of hydrogen ions and hydroxyl ions in the soil. It is measured in the range of 1 – 14, 1 being the most acidic and 14 being the most alkaline while 7 serves as the midpoint representing neutral substances like water.
Soil pH is an essential measure in determining the availability of certain nutrients in the soil. Nutrients can be found in the ground in abundance, but due to some conditions related to the alkalinity and acidity of the soil these nutrients may be scarce or non-existent. To be available, nutrients are supposed to be soluble. Soil pH affect nutrients solubility (The Spruce, 2019).
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Soil pH can also influence plant growth by its effect regarding the survival of microorganisms for instance detritivores and saprotrophs. But also nitrifying bacteria that adds nitrogen into the soil (ESF, 2020). Soil pH also affects the soil structure. For example, clay soil is mostly immune to pH changes. But in an optimum pH range it is usually granular and easy to work with. When it gets too acidic or basic, the soil becomes sticky and usually does not support plant growth making foo availability for the cattle scarce.
BACKGROUND INFORMATION
Cattle grazing is when cattle feed on ground plants in the main purpose of converting the energy stored in plants for themselves (the cattle). This practice is popular in the Monduli lands where the societies there practiced pastoralism. Cattle grazing does not only affect the plants rooting system but also add up to the soil nutrients and alter the soil pH by introducing dung and urine in the grazed lands. Contrast to that, grazing can have negative effects. An increased portion of bare land that is caused by overgrazing making it easily eroded (AHBD dairy, 2019)
Soil pH is an estimated measure of the acidity and alkalinity of soil considering the concentration of hydrogen ions and hydroxyl ions in the soil. It can be measured by using a calorimeter test kit, pH probe or by using test paper strips. The test kit consists of various reagents mixed with soil solutions and a color reference strip.
Soil pH can be affected by various abiotic conditions. The abiotic factors include climate, soil mineral composition and its texture. Temperature and rainfall, affect the degree of leaching and weathering. The soil tends to be more acidic in areas that receive a lot of rain since basic cations such as sodium and potassium are carried away with the water resulting into leaching. In dry areas, where leaching cannot be observed, the soil remains fairly neutral or acidic.
Mineral content in the soil is highly influenced by the input of materials. In non-grazed lands, we expect very little alteration in the soil pH from the neutral point because there is barely any input in the soil. However, in grazed areas we expect a variation of soil pH due to the excreting activities done by the cattle. Although the natural/initial soil pH (other factors excluded) would reflect the basic soil formation factors such as time, topography, parent rock, climate and organisms present during the formation. Soil pH can be easily or very difficult to alter with regards to the mineral composition it has based on organic matters.
The type of soil and the quantity of organic material present also affects the soil pH range. For instance, clay soil is more resistant to pH change while sandy soil is more flexible with pH changes. Organic matter is also resistant to pH change. While we cannot change the type of soil in the area, we can alter the amount of organic materials in the soil (USDA, 2020).
Plant growth observed in grazed and non-grazed lands is highly affected by the soil ph. Soil pH is a highly responsible in the solubility of minerals and plant nutrients. It also affects the survival of micro-organisms that support plant growth like Rhizobium. This is the reason why grazed areas usually has small shrubs and a lot of grass while non-grazed areas have a very thick vegetation with trees and little grass coverage.
HYPOTHESIS
The hypothesis of this experiment is that the soil pH on the grazed lands will be more acidic than the one in non-grazed lands. In grazed lands, cattle like cows are expected to excrete. The major composition of urine is uric acid that rises the concentration of hydroxyl ions in the soil making the soil pH a little under the neutral point 7 on the pH scale. While in non-grazed lands, the soil pH is expected to be neutral or alkaline because of the lack of cattle input.
CONCLUSION
Animals excrete from time to time. Laboratories and research centers have proven that urine is comprised with uric acid which is acidic in nature. Although animals produce feces that sometimes is used as fertilizer that neutralizes the soil, the animals urinate more frequently than the produce feces. In this case, no nearby water source was observed near the grazed lands. High concentration of uric acids in the urines can faster facilitate the acidification of the soil in the grazed lands.
The nutrients availability is affected by the soil pH to a certain extent. Nitrogen was averagely recorded low because soil pH is important for nitrogen fixation bacteria. The survival of the Rhizobium bacteria declines as soil acidity increases. Phosphate was only detected in a trace because its compounds are not easily soluble in acidic soil. Phosphorus forms stable compounds that are not easily disintegrated to be available for solubility. As for Potassium, the nutrient is not directly affected by the pH of the soil. That it is the reason it is found in abundance in grazed lands (USDA, 2020).
On the other hand, the hypothesis also affirms to the fact that the non-grazed area will have a neutral soil ph. In the observations above, the non-grazed area was seen to have less water in the soil due high distribution of trees and shrub. Also, the type of vegetation suggests that the area does not receive as much rainfall throughout the year. Therefore, leaching does not take place and the cations such as potassium and sodium stay intact making the soil pH neutral (ESF, 2020).
With the scientific justification given above, it can be concluded that, the results obtained for the experiment affirms with the hypothesis provided above that the soil pH of the grazed lands will be lower (acidic) than that of the non-grazed land which is expected to be either neutral or alkaline.
EVALUATION
The tape measure was not laid flat on the ground and thus the measurements may be inaccurate. Obstacles such as medium and large sized bushes and large trees in the non-grazed lands made it extremely difficult to lay the tape down. This can be improved by selecting areas which are more open to make it easier to lay the tape on the ground in a straight line.
Some of the pH reagent used got stuck on the side and thus did not react fully. Rinsing it off with water was not an option because then the volume of the water used would increase. Therefore, I would suggest that peeling it directly on top of the solution will ensure it all gets in rather than trying to insert it from the sides.
Inaccurate measure of the sample in ratio to the volume of water. Some necessary equipment such as a measuring cylinder and spatula were not brought with us to the field. Consistency was not achieved due to the absence of these equipment. Random estimation of how much soil will be mixed with an approximated volume of water may have led to inaccurate results. This can be improved by revising the equipment list and ensuring that all equipment regardless how small it is, is brought to the experimenting field.
The water used to mix the soil was not distilled and thus may affect the results of the experiment. At some point during the experiment we ran out of distilled water. So, we opted to use rainwater, this could have affected our results. Rainwater may have traces of carbonic acid altering our results by lowering the pH of the soil. This could easily be solved by bringing enough water to the extraction and experimenting sites in order to make results more accurate.
The use of random sampling ensured that we extracted samples for various area within both the grazed and non-grazed lands. A clear picture and a more accurate result could be obtained since the extraction is not biased to only one section of the lands.
BIBLIOGRAPHY
- The Spruce. Soil pH: What is it and why it matters.https://www.thespruce.com/importance-or-proper-soil-ph-2131096. Accessed on: March 24,2020.
- USDA. Soil ph. https://cropwatch.unl.edu/documents/USDA_NRCS_pH_guide_edit_6_3_14.pdf. Accessed on: March 24,2020.
- AHBD dairy. How farming affects soil life.https://dairy.ahdb.org.uk/technical-information/grassland-management/healthy-grassland-soils/life-beneath-your-land/impact-of-farming-on-soil-quality/how-farming-affects-soil-life/#.Xnxfzm5uJdo. Accessed on: March 26,2020.
- ESF. Soil pH: what it means. https://www.esf.edu/pubprog/brochure/soilph/soilph.htm. Accessed on: March 25,2020.