Introduction
Attaining and sustaining correct levels of soil fertility is essential for agronomic land to support crop production at satisfactory levels. Soil analysis, which is a critical process in agriculture, involves testing a soil sample to ascertain its nutrient content, structure, and other attributes such as alkalinity or acidity (pH level), porosity, and permeability (Rowell, 2014). Soil analysis determines the soil texture, which is useful in predicting crops that can thrive in specific soils. This process also verifies the level of nutrient availability in the soil, thereby acting as a basis for the computation of the amount of fertilizer needed. Consequently, it is possible to forecast increase in yields and profitability. Additionally, soil analysis assesses the supply of each nutrient element to direct the establishment of eco-friendly nutrient management strategies. Nutrient management encompasses three main steps: soil sampling and analysis, interpretation of analytical data, and making recommendations based on the results. Sampling should be done following harvest and before applying any fertilizer. For permanent crops such as orchards, soil analysis should be conducted every four to five years (Colazo & Buschiazzo, 2015).
Soil productivity is influenced by multiplex interactions between biological, chemical, and physical attributes of soil. Therefore, good farming practice strives to optimize crop yields by regulating these three soil properties. Physical aspects of soil include factors such as texture, porosity, and permeability, whereas chemical features encompass the availability and concentration of chemical elements (such as potassium, nitrogen, phosphorus, and magnesium) that provide nutritive benefits to plants. Biological properties, conversely, refer to microorganisms found in soil.
The sample used in this study comes from Petrolia Texas. Soil maps indicate that the predominant soil in this region of Texas is clay (United States Soil Conservation Service & Texas Agricultural Experiment Station, 2015). However, the precise composition of the soil varies from one place to another with some areas having silt-loam and others clay-loam soils. Therefore, it is hypothesized that the predominant soil texture for this sample will be clay. The purpose of this experiment is to conduct a soil analysis to determine the texture, porosity, permeability, pH, and nutrient levels of the provided soil sample.
Data
Soil Texture
Table 1 indicates the percentage composition of various soil components in the sample. The proportions of each constituent (as indicated in the percentage composition column) show that the soil texture can be classified as sandy clay.
Table 1. Soil components and their percentage composition
Water Holding Capacity (Soil Porosity)
The soil porosity was calculated as follows:
Volume of pore space= 25 ml
% pore space = (volume of water/volume of soil x 100)
= 25 ml/100 ml × 100% = 25%
Soil Permeability
The amount of water that drained in 10 minutes was 29.574 milliliters.
Soil pH
The pH reading was 7.5. Therefore, the soil could be classified as alkaline (weakly alkaline). Examples of three crops that can grow in soil with this pH are bean, artichoke, and cucumber.
Soil Nutrients
Table 2 shows the levels of three nutrients tested in the experiment. The amounts of phosphorus and potassium were appropriate for healthy plant growth. However, nitrogen was depleted in the soil.
Table 2. Nitrogen, phosphorus, and potassium levels in the sample
Analysis
The physical composition of soil is determined by the dimensions of its particles, which can be clay, sand, or silt. Sand, which is characterized by a grainy feel, has the largest particles. The size of silt particles is significantly smaller than sand but larger than clay. Additionally, silt has a smooth, crumbly feeling. Clay has the smallest particles that are arranged compactly. Soil texture is determined by the proportions of clay, sand, and silt in the mixture. This property is useful because it influences the oxygen and water holding ability of the soil (Colazo & Buschiazzo, 2015). Porosity signifies the extent of open spaces between particles. Fine-textured soil such as clay has more pores and holds more water than coarse-textured soils such as sand. Soil perviousness is the capacity of water to move through the soil. Sandy soils are highly permeable as opposed to clay soils. The soil texture was determined as sandy clay. This type of soil has almost equal proportions of sand and clay. It is known for its low aggregate stability as well as drainable pores, which can be improved by a process known as biochar amendment (Baiamonte et al., 2015). These findings corroborated the hypothesis that the sampled soil would have large proportions of clay.
Soil pH is an estimation of acidity or alkalinity as shown by the relative concentrations of free hydrogen ions and hydroxide ions respectively. The pH scale, which ranges from 0 to 14, is usually used to categorize soil pH. Substances with pH values below 7 are considered acidic, whereas values exceeding 7 are regarded alkaline. A pH of 7 is an indication of a neutral substance. Soil pH influences plants’ nutrient absorption potential because different nutrients are soluble at varying pH levels. Thus, knowledge of soil pH aids in determining crops that should be grown in specific soils. The experiment indicated that the soil had a pH of 7.5, which fell within the conventional pH range of 4.5 to 8.5 as reported by Rowell (2014).
Healthy plant growth requires about sixteen nutrients that are classified as either macronutrients or micronutrients. Macronutrients are consumed in large quantities by plants for growth and other physiological processes. They include nitrogen, phosphorous, and potassium. Nitrogen is involved in protein synthesis and the formation of chlorophyll while phosphorus promotes cell division and metabolic reactions through phosphorus-containing molecules such as adenosine triphosphate and adenosine diphosphate (Rowell, 2014). Potassium plays a vital role in the metabolism of carbohydrates. Micronutrients are needed in small quantities. They consist of elements such as iron, zinc, copper, and cobalt. The absence of these nutrients threatens crop productivity, which necessitates the application of fertilizers. Nevertheless, increasing their concentrations to very high levels is an unwarranted expense. In this experiment, nitrogen was not detected because it was depleted in the sample. However, potassium and phosphorus were present in adequate quantities. Soil management efforts should consider nourishing the soil with nitrogen-rich fertilizers.
The availability of soil nutrients to plants is determined by the pH of the soil. High acidity levels (below pH 6.0) are known to decrease the availability of phosphorus and trace elements. Optimal levels of nitrogen and potassium are found within pH ranges of 6.0 to 8.0 and 6.0 to 10 respectively. Phosphorus is readily available in slight acidity and slight alkalinity conditions (6.5 to 7.5).
Conclusion
Soil analysis facilitates the determination of the physical and chemical features of soil to inform agricultural practices. In this experiment, the soil texture was identified as sandy clay, which indicated that the soil could benefit from additional processes such as biochar amendment to improve its porosity and permeability. The pH was determined as slightly alkaline (7.5), which favors the growth of plants such as bean, artichoke, and cucumber. Phosphorus and potassium levels were adequate for plant growth. However, the soil required enriching with nitrogenous fertilizers.
References
Baiamonte, G., De Pasquale, C., Marsala, V., Cimò, G., Alonzo, G., Crescimanno, G., & Conte, P. (2015). Structure alteration of a sandy-clay soil by biochar amendments. Journal of Soils and Sediments, 15(4), 816-824.
Colazo, J. C., & Buschiazzo, D. (2015). The impact of agriculture on soil texture due to wind erosion. Land Degradation & Development, 26(1), 62-70.
Rowell, D. L. (2014). Soil science: Methods & applications (2nd ed.). New York, NY: Routledge.
United States Soil Conservation Service & Texas Agricultural Experiment Station. (2015). General soil map, Clay County, Texas. Web.