The soil condition is essential for healthy plants. Many factors can affect the soil condition including nutrient levels, pH, precipitation, temperature, and water retention. Soil pH is an excellent indicator of the suitability of a given location for plant growth. For most plants, a soil pH of 6 to 7.5 is optimal. When the pH levels are too high or too low, this leads to a deterioration of soil health including a deficiency of many nutrients, a decline in microbial activity, and a decrease in crop yields. Additionally, some diseases thrive in alkaline or acidic soils. Mrs. Brown’s class is studying how the soil pH affects microbial activity and nutrient availability. After planting seedlings in a wide range conditions - including strongly acidic soil, weakly acidic soil, strongly basic soil, weakly basic soil, and neutral soil. The class observed the growth of the seedlings over the next two weeks both qualitatively and with quantitative measurements.

The class found that the pH directly affects ion and nutrient availability. Most minerals are more soluble in acid soils but soils with high acidity tend to have toxic amounts of some ions like aluminum and manganese. Plants which need calcium need moderate alkalinity. Nitrogen and phosphorus are considered essential nutrients for plant health and growth. Nitrogen is part of chlorophyll which is crucial to photosynthesis but nitrogen cycling is inhibited by low pH. Phosphorus is also important to photosynthesis and encourages plant and root growth. Extreme soil pH values below 5.5 and between 7.5 and 8.5 limit the availability of phosphate for plants. Many more nutrients are required in trace amounts for plant health, macro- and micronutrients. These trace essential nutrients are also effected by the pH of the soil. High pH results in low micro-nutrient mobility, while macronutrients are usually less available in soils with low pH.

Furthermore, the class found that microbes are vital to plant growth and survival, by being integral parts of the carbon and nitrogen cycles. The microbes break down organic matter in the soil releasing essential nutrients and carbon dioxide back into the soil. Additionally, the microbial activity helps plants defend themselves against pathogens and degrade pest control chemicals. Finally, microbes are responsible for nitrogen fixation by capturing inert N2 gas from the air and making it available to plants. The majority of soil microbes thrive in neutral pH, between 6 and 7. Microbial activity is high in this range due to the high availability of most nutrients in this pH range. Alterations in pH can render essential microbe enzymes inactive and/or denature proteins within the cells and prevent microbial activity from occurring.

Testing soil pH is imperative to optimize soil condition for plant growth. There may be substantial variation in the pH from one spot in the planting area to another. So collect soil from several locations and combine into one sample to give an average soil sample. Combine several tablespoons of the average sample with several tablespoons of water, mix well, and allow the precipitate to settle. Now the pH can be tested by testing the water. The most accurate method of determining soil pH is by a pH meter. While pH meters are very accurate, such meters are expensive and delicate. The most common test uses specialized paper called pH paper. pH paper is nearly as accurate as the pH meter and is much less expensive. Finally a simple, easy, and inexpensive but less accurate method, consists of using indicators or dyes to estimate the pH. Once the pH of the soil has been determined, then amendments can be added to the soil to adjust the pH.
How is testing soil pH related to the health of the soil?

A)Measuring the pH corrects the deficiency in the soil nutrients and microbes.
B)Calculating the pH of the soil enhances the plant growth microbial activity.
C)Identifying the pH levels helps develop irregularities in the soil conditions.
D)Determining the soil pH helps to optimize and improve the conditions for growth.