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Healthy soil must contain 45% solids, 25% air, and 25% water. 80% of the remaining 5% must be decomposed and decomposing organic matter, while the 20% consists of living organisms, roots, and fresh residue.
According to MediLexicon's medical dictionary, health is defined as the state of the organism when it functions optimally, without evidence of disease or abnormality. So, soil health can be defined as the capacity of the soil to function optimally. Some of the main functions of soil include storage of water and nutrients, feeding the plants, filtration of air and water, etc. Apart from meeting our basic food production needs, healthy soil is also necessary for the effective functioning of our ecosystem.
What is Healthy Soil?
Soil consists of four basic components: minerals, organic matter, water, and air. While minerals generally include clay, silt, and sand, organic matter comprises plant and animal matter that are in different stages of decomposition. When it comes to the health of the soil, the most important factor is the organisms that thrive in it. They include bacteria, fungi, nematodes, protozoa, earthworms, and other small organisms.
Most of them play a major role in decomposing organic matter in the soil, thereby, converting it into nutrients and other beneficial compounds required by plants. These organisms thrive on the organic matter and by-products from the growing roots. So, both plants and soil organisms depend on each other for survival. Apart from decomposing organic matter and cycling nutrients, these soil organisms are also useful for improving soil texture, and control pests in it. In short, healthy soil must have sufficient microbial activity. Healthy soil must have well-balanced physical, chemical, and biological properties.
Soil Health Indicators
Traditionally, improving soil health means, enhancing fertility and balancing the pH. However, the whole concept of soil health has evolved through the years, and now, it constitutes a host of other elements, as discussed above. Efforts must be aimed at achieving a balance between the physical, biological, and chemical properties, as they are interrelated. For example, a very low pH (a chemical property) may affect the texture of the soil, which is a physical aspect.
The health condition of the soil can be determined through assessment of its physical, biological, and chemical features.
The physical features of soil include its texture, structure, topsoil structure, color, rate of water infiltration and drainage, slaking (rate of breakdown of soil, when exposed to water), etc. Chemical properties include its pH, salinity, sodicity (amount of sodium), level of trace elements, levels of nitrogen and phosphorous, etc. Level of organic matter, population of soil organisms, and abundance of roots are classified as biological factors.
Correcting problems relating to these three main indicators will be sufficient to enhance the health of soil. Here are some proven ways to improve soil health.
Methods to Improve Soil Health
Crop Diversity: Rotating crops offer numerous benefits, right from pest control to adequate nutrient supply. For example, legume crops are often followed with crops that demand high levels of nutrients. Growing the same crop year after year could lead to pests, weeds, and diseases. Plants with deep roots (like alfalfa and sunflower) can be cultivated in between, as they will improve infiltration rate.
The added advantage is the diversity of residue and root structure offered by different types of plants. This results in diversity of organisms that thrive in that soil. These organisms are beneficial for controlling a wide array of pests and diseases.
While crop rotation is a method of changing the type of vegetation, year after year, or at regular intervals, you may also opt for different types of vegetation across the landscape. If you want to try the latter method, contour strip cropping, buffer strips, etc., may prove useful.
Ground Cover: Ground cover can be in the form of crop residue or cover crops. A layer of residue over the soil is like a protective cover that will protect it from natural elements, like rainfall and wind. It will prevent soil erosion, and at the same time, improve infiltration too. The ground cover will prevent puddling, and will eventually turn into organic matter. Living crops, like wheat and rice provide ground cover and offer high levels of residue.
Another advantage is the presence of live roots throughout the year. Live roots are necessary for the survival of soil organisms.
Reduced Tilling: Tilling is not always bad, but reducing it will be beneficial in different ways. Tilling introduces air into the soil, and this leads to oxidation of carbon. The carbon that oxidizes to carbon dioxide, leaves the soil. Another problem with tilling is the disturbance caused to the activity of soil microbes. It also exposes the soil, and makes it prone to flooding and crusting.
Without tilling, the soil microbes remain active, and the rate of decomposition of organic matter will be steady. The structure of the soil, as well as the rate of infiltration, will not get affected.
Organic Matter: Though addition of organic matter may not offer you fast results, it is a slow, but sure way of enhancing soil health. Apart from improving soil structure, it will also support microorganisms and their activity. The capacity of the soil to hold water and nutrients will also improve. Organic matter acts as a binding agent for soil that will become porous, thereby, allowing water to infiltrate. Presence of organic matter makes the soil moist too.
Soil Type: While clay soil tends to be sticky and soggy, sandy soil does not retain water and nutrients. Though better than clay soil and sandy soil, silty soil too has some drainage problems. In case of silty soil, avoid soil compaction through tilling and frequent walking. Add at least an inch of organic matter every year. Raised beds may prove useful for both silty and clay soil.
Tilling should be avoided in clay soil, which also requires around three to four inches of organic matter. In case of clay soil, add an inch of organic matter every year, during the fall. For sandy soil, three to four inches of organic matter must be added. Mulching will be beneficial for retaining moisture. Add two inches of organic matter every year, and grow cover crops.
Soil pH: Soil with a pH of 8 to 14 is called alkaline soil, and if the value is between 0 and 6, the soil is acidic. The value of 7 is neutral. A pH value of 6.3 to 6.8 is considered the best for many plants, as most of the nutrients are soluble in this range. However, there are certain plants that require acidic or alkaline soil for healthy growth.
Though addition of organic matter is believed to be useful for balancing the pH of the soil, additional measures may also be required. While addition of ground limestone raises the level of pH, ground sulfur will reduce simultaneously.
Deteriorating Soil Health
Symptoms: The deteriorating health of soil can be manifested in different ways. The most prominent among them is the decline or stagnation of yields from crops. The soil may fail to absorb rainwater properly, and form surface crusts after a rainfall. Poor plant growth, diseases and pests, etc., can also be noticed. Even the quality of the water leaving the site may become poor, due to excess sediments.
Causes: The consequences of unhealthy soil is not limited to poor yield, but in the long run, it can cause various other problems, like pollution of ground and surface water bodies. As far as the ways to improve soil health was concerned, the focus was mainly on enhancing fertility that was primarily achieved through chemical fertilizers.
With deteriorating soil health, incidence of pest attacks and diseases too escalated, leading to a rise in use of pesticides and other chemicals. Misuse of these chemicals resulted in disruption of the chemical and biological balance of the soil. The relationship between the soil organisms and the roots got disrupted due to supply of artificial nutrients.
Another possible reason is regular tilling that disturbs the biological activity and decomposition of organic matter. Lack of organic matter also played a major role in making soil less healthy.
Maintaining soil health is highly important for increased agricultural productivity and maintaining a healthy ecosystem. This Gardenerdy article is intended to provide some basic information about the subject. You must consult concerned authorities, who will help you out with guidelines to improve soil health. Testing the soil is always better, as the underlying problems may not be the same for each and every type.