How can we prevent soil leaching?

The leaching of nutrients from the soil is a major cause of stunted plant growth and decreased agricultural product quality. Nutrient leaching can occur due to factors such as heavy rain and over-watering. This article aims to clarify the concept of leaching soil nutrients and provide effective solutions to prevent it.

What are the soil nutrients?

Plants require nutrients to grow and thrive. While carbon, oxygen, and hydrogen are obtained from water and air, other essential nutrients, such as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, manganese, iron, and copper, must be supplied by the soil.

The quality and quantity of a plant and its products are determined by the nutrients it receives from the soil. To have a healthy plant with maximum yield, each essential element must be readily available to the plant. Any imbalance in the plant’s nutrients will result in a decrease in its quality.

How are nutrients removed from the soil?

Nutrients are removed from the soil in several ways:

• Absorption by plants: Plants feed on nutrients in the soil to grow. These elements are absorbed by the root system of plants and distributed in different plant tissues.
• Soil leaching: Leaching of nutrients from the soil occurs due to heavy rainfall and irrigation, which wash away nutrients and transfer them to underground and surface water. The more drainage water there is, the more elements are removed from the soil.
• Soil erosion: Nutrient elements in the soil can be moved out of the soil due to soil erosion or physical and chemical weathering.
• Excretion by animals: organisms living in the soil, such as insects, worms, and microorganisms, absorb nutrients from the soil in their feeding process and then excrete them. This process removes these elements from the soil.
• Crop residue burning: Burning plant residues causes nutrients in the plant tissue to be transferred out of the soil.
• Sunlight: Sunlight and high heat cause nitrogen fertilizers to turn into ammonia gas. Ammonia gas is emitted from the soil surface and enters the atmosphere.
• Soil compaction: Soil compaction causes no gas exchange in the soil. Carbon dioxide gas trapped with soil carbonates forms bicarbonate and precipitates calcium. In this condition, the soil becomes alkaline and lacks nutrients.

The processes we mentioned all reduce the nutrients in the soil. To compensate for these substances, the soil must be nourished and the lost elements replaced.

What is the meaning of soil leaching?

The leaching of nutrients from the soil occurs when some nutrients are washed away from the soil by rainwater or irrigation and are carried to the lower soil layers or underground water. This process can result in reduced soil fertility and a shortage of nutrients for plants.

When soil is washed, essential elements such as nitrogen, potassium, calcium, and magnesium are removed, leading to a reduction in soil fertility. This can limit the access of plant roots to nutrients and ultimately decrease crop yield. Soil washing also removes toxins from agricultural lands, preventing them from entering the ground and polluting the environment and water.

The leaching of nutrients from the soil reduces the population of beneficial microorganisms. This is a precursor to soil erosion.

What causes soil leaching?

Factors affecting the leaching of nutrients from the soil can be classified as follows:

Climatic factors

As mentioned, heavy and prolonged rainfall can lead to the loss of nutrients from the soil. The amount of nutrient washing is determined by the intensity of the rainwater flow. It’s important to note that nutrient leaching is more prevalent in humid climates compared to dry climates.

Excessive watering

Over-watering the plant can lead to nutrient leaching, which is an essential factor to consider. When a large volume of water enters the soil, especially in soils with a light texture, it reduces fertilizer absorption and promotes leaching. To prevent this issue, it’s best to avoid flood irrigation when possible and instead opt for drip or rain irrigation.

Soil texture

Soil characteristics, such as soil permeability, influence soil leaching. In soils with a sandy texture and high permeability, soil nutrients are more likely to be leached.

steep terrain

The slope of the land contributes to soil leaching, with steeper slopes increasing the likelihood of leaching.

too much of organic matter

Excessive use of fertilizers can lead to improper absorption of nutrients and nutrient loss. Among different fertilizers, nitrogen fertilizer has the highest risk of leaching from the soil.

To prevent this problem, it’s best to use fertilizers with high solubility and slow-release fertilizers in your fertilization plan. For instance, urea and ammonium sulfate are two commonly used nitrogen fertilizers. Urea has a higher nitrogen content compared to ammonium sulfate, but its low solubility and fast release lead to high leaching rates. On the other hand, ammonium sulfate is a slow-release chemical fertilizer that provides nutrients to the plant gradually over time. Hence, opting for ammonium sulfate can help reduce nitrogen leaching.

Management factors

Failure to adhere to irrigation principles, improper scheduling of irrigation, inadequate vegetation, and uncorrected soil pH are all management factors contributing to soil nutrient leaching. These factors, whether occurring individually or in combination, form the basis for nutrient leaching from the soil. Effective management of these factors can minimize leaching and preserve soil fertility.

How to prevent soil nutrient leaching?

There are several methods to prevent leaching of nutrients from the soil:

• Irrigation management: In order to prevent soil leaching, it’s important to avoid excessive watering. Irrigation should be tailored to the specific needs of the plant and timed precisely. Additionally, it’s best to use efficient irrigation methods such as drip or rain irrigation.
• Improving the soil structure: To reduce leaching, one of the methods is to enhance the soil structure. To achieve this, the soil needs to be tested to identify its fundamental requirements. Once the soil characteristics are recognized, we can devise a more effective plan to enhance the soil structure. Using natural fertilizers like animal manure and compost is one of the most efficient ways to improve soil structure. Additionally, planting cover crops is an effective method to conserve soil and absorb nutrients.
• Using slow-release fertilizers: For chemical fertilizers to minimize leaching, it is recommended to utilize coated or slow-release fertilizers. Additionally, distributing the application of fertilizer throughout the growing season helps in reducing nutrient leaching from the soil.
• Correction of soil pH: Remember to consider soil pH as a factor in soil leaching. Use fertilizers that are suitable for the soil pH to avoid disrupting the soil pH. If the pH decreases, you can use modifiers such as lime to normalize the soil pH.

These methods, separately or in combination with each other, can prevent the leaching of nutrients from the soil and maintain soil fertility.

Methods of detecting the lack of plant nutrients

Soil leaching can lead to a depletion of plant nutrients. When plants display signs of nutrient deficiencies and abnormal growth, it is important to examine the soil structure and make necessary corrections. There are various methods available to identify and address nutrient deficiencies in plants.

• Physical examination of plants: the appearance of special signs of deficiency of any nutrient on leaves and other plant organs, such as changes in the shape, color, and size of leaves and other organs.
• Leaf test: analysis of the leaf tissue of the plant to determine the amount of nutrients in it and compare the results with the standard amounts required by the plant
• Soil testing: soil analysis to determine the amount of nutrients in it and compare the results with the desired values.
• Diagnostic tests: performing diagnostic tests such as hybrid leaf test
• Field observations: examining the appearance and growth of plants in field conditions and comparing them with healthy plants in nearby areas

The following methods are used individually or in combination to detect any potential nutrient deficiencies in plants and to implement appropriate corrective actions. If it is determined that the land is experiencing drainage issues, necessary measures will be taken to address and resolve this problem.

how to solve the problem of soil nutrient leaching in a farm?

To address the issue of soil nutrient leaching in a farm, it’s crucial to implement a comprehensive approach that focuses on optimizing nutrient management practices.

• Soil Testing and Monitoring: Start by determining the soil mineral nitrogen content through regular sampling. This information will help in understanding the current nutrient levels and guide fertilizer applications.
• Balanced Nutrition: Ensure a balanced supply of essential nutrients like phosphorus (P), potassium (K), and sulfur (S) to optimize nitrogen uptake by the crops. This balanced nutrition approach can improve nutrient efficiency and reduce excess nitrogen that could leach into the soil.
• Root System Development: Encourage the development of deep and extensive root systems in crops to enhance nutrient uptake efficiency. A well-developed root system can capture available nutrients effectively, reducing the risk of leaching.
• Accurate Fertilizer Application: Apply fertilizers and manure accurately across fields based on soil test results and crop nutrient requirements. Precise application helps prevent nutrient excesses that can leach into the soil.
• Buffer Strips Maintenance: Maintain buffer strips between cropped land and watercourses to reduce nutrient runoff and erosion. Buffer strips act as a protective barrier, filtering out nutrients before they reach water sources.
• Green Cover Management: Keep green cover on fields for as long as possible to absorb excess nitrogen and prevent leaching. Ensure rapid re-establishment of green cover after plowing to maintain soil protection and nutrient retention.
• Soil Structure Management: Maintain a porous soil structure to facilitate water infiltration and reduce surface runoff and sub-surface bypass flow, especially on heavy soils. Good soil structure promotes water retention and nutrient availability for plants. we suggest you take a look at the stages of preparing agricultural land.
• Fall Application Guidelines: Follow specific guidelines for the application of manure and fertilizers in fall to minimize nutrient leaching during the off-season. Timing applications correctly can help ensure nutrient uptake by plants and reduce losses through leaching. You may be interested in our guid to fall plant care.

By incorporating these strategies into your farm management practices and adapting them to suit your specific soil and crop requirements, you can effectively reduce soil nutrient leaching and promote sustainable agriculture practices for long-term soil health and productivity. Regular monitoring and adjustment of these practices will be essential to maintain optimal nutrient levels in the soil.