Soil pH is a measure of the acidity or alkalinity of soil, which is determined by the concentration of hydrogen ions (H+) in the soil. The pH scale ranges from 0 to 14, with pH 7 being neutral. A pH value less than 7 indicates acidic soil, while a pH value greater than 7 indicates alkaline or basic soil. Soil pH value is considered as one of the most vital factors which may determine the yield of the crops. Soil pH can regulate and control many chemical and biochemical reactions within the soil. If the soil pH is too high or too low, it can obstruct nutrient absorption, reduce plant growth, and even lead to plant death. Thus, it is important to maintain an optimal pH level in soil for healthy plant growth.
Level of acidity and alkalinity | Range of pH |
Strongly acidic | pH below 5.5 |
Moderately acidic | pH between 5.5 and 6.5 |
Slightly acidic | pH between 6.5 and 7.0 |
Neutral | pH of 7.0 |
Slightly alkaline | pH between 7.0 and 7.5 |
Moderately alkaline: | pH between 7.5 and 8.5 |
Strongly alkaline | pH above 8.5 |
Soil pH can be measured using pH meter or by sending the soil samples to a soil testing laboratory for analysis, which typically involves chemical testing using specialized equipment.
Acidic soil is soil that has a pH value of less than 7. Acidic soil can have low nutrient availability, especially for essential plant nutrients such as calcium, magnesium, and phosphorus. This is because these nutrients can become less soluble and available for plant uptake at low pH values. As a result, plants grown in acidic soil may exhibit stunted growth, yellowing of leaves, and reduced yield. Acidic soil may contain high levels of aluminum, iron and manganese which can be toxic to plant roots and inhibit plant growth. This can also result in reduced water and nutrient uptake. Acidic soil have reduced microbial activity.
Alkaline or basic soil is a type of soil with a pH level above neutrality (pH > 7). This alkalinity is often caused by the presence of minerals such as calcium, magnesium and potassium, which are commonly found in alkaline soils. Despite the high mineral content, alkaline soil often lacks nutrients like iron, manganese, zinc, copper due to the high pH level. The high pH level of alkaline soil can cause certain nutrients to become chemically bound in the soil, making them less available to plants. This can lead to poor plant growth and development. In addition, the lack of organic matter in alkaline soil can lead to poor soil structure and decreased water holding capacity.
Crop | Soil pH Range | Crop | Soil pH Range |
Rice | 5.5 – 7.0 | Peas | 6.0 – 7.5 |
Wheat | 6.0 – 7.0 | Okra | 6.0 – 6.8 |
Maize | 6.0 – 7.5 | Brinjal (Eggplant) | 6.0 – 6.8 |
Sugarcane | 5.5 – 8.0 | Cucumber | 6.5 – 7.5 |
Cotton | 5.0 – 7.5 | Watermelon | 6.5 – 7.5 |
Groundnut | 6.0 – 6.5 | Mango | 5.5 – 7.5 |
Soybean | 6.5 – 7.5 | Banana | 5.5 – 7.5 |
Mustard | 6.5 – 7.5 | Pineapple | 5.0 – 6.0 |
Potato | 4.8 – 5.4 | Guava | 4.5 – 8.2 |
Tomato | 6.5 – 7.5 | Citrus (Orange/Lemon) | 5.5 – 7.5 |
Onion | 5.5 – 6.5 | Grape | 6.5 – 7.5 |
Carrot | 6.0 – 7.0 | Cauliflower | 5.5 – 6.5 |
Cabbage | 5.5 – 6.5 | Chilli | 6.5 – 7.5 |
Papaya | 6.5 – 7.0 | Barley | 7.0 – 8.0 |
Barley | 7.0 – 8.0 | Garlic | 6.0 – 7.0 |
Beans | 5.5 – 6.0 | Radish | 5.5 – 7.0 |
Above are the indicated optimum pH ranges for the crops. Soil test analysis during crop planning will help in deciding the crop to go in particular soil. Soils with extreme pH may be corrected to a certain extent with the above-mentioned amendment agents.
NOTE:
Majority of the plant nutrients are most available to plants within the pH range 6 – 7.5. Thus, it is important to maintain this soil pH to ensure healthy plant growth and development.
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