Extensive research revealed that there are only three ancillary divisions or components of soil. These divisions have several sub-segments. Some practices that can be used to manage or improve soil health include reducing inversion tillage, using cover crops, and managing nutrients. Soil erosion is caused by deforestation, overgrazing, and rainwater. Please note that a few resources published earlier that 2018 have been used as the data provided remain valid.
ANCILLARY DIVISIONS: SOIL
The components of soil health, also known as its ancillary divisions are physical, chemical, and biological components.
- The physical components of soil health consist of the rocks and minerals that have been fragmented over time into minute particles of sand, silt, and clay. These compounds are often measured to determine the texture of the soil.
- While sand is the most coarse material and can be easily felt as rough particles, silt is smaller than sand, with clay having the smallest particles.
- Sand assists in keeping the soil loose. It also leads to an increased internal drainage. Clay particles, on the other hand, offer more surface area to retain nutrients and healthy water in the soil.
- The natural "physical and chemical bonds between these particles creates internal structure in the soil and small clumps called aggregates." This aggregation decreases soil compression and enlarges the space for roots to penetrate, thus enabling better plant growth.
- Surface slope, internal drainage, and stoniness are a few other features that contribute to the physical properties of the soil.
- The chemical components of soil are categorized into the pH, nutrients such as potassium, and water. In determining the amount of nutrients and water that can be stored in the soil, soil health is important.
- This component is largely dependent on the physical component of the soil. The physical characteristics of soil determine how much water the soil can hold. Sandy soils do not hold water easily, while a clay soil, with very small pores, can hold water better than sandy soils.
- The chemical characteristics of the soil are known through laboratory testing. Through testing, one can look for nutrients necessary for plant production such as zinc. Recommendations for fertilizer can also be made based on the measurable levels of these chemical factors.
- Chemical testing assists in determining soil management practices that are necessary to improve soil characteristics.
- The biological component is the final component of soil that is important to the overall productive capacity and health of soil. This component includes the insects, fungi, animals, bacteria, plants, earthworms, protozoa, nematodes, and arthropods that live in the soil.
- Although much of the soil biological component is visible, an example being earthworms, others are too small to see without magnification.
- The microbiomes that are too small to see are a dynamic and active community that are responsible for a lot of the recycling of nutrients and water that takes place in the soil.
- While microbiomes or microorganisms like Rhizobium bacteria and Arbuscular mycorrhizal fungi are beneficial, others such as the Macrophomina phaseolina fungi are destructive and lead to charcoal rot.
- In one gram of soil alone, there are up to a billion living organisms, consisting of more than five thousand species, most of which are single-celled bacteria.
- Biological activity "enhances water retention and soil absorbency, and reduces water runoff by increasing the organic matter content in the soil."
- Increasing the soil organic matter "by 1% increases the retention of available water by one acre inch, or up to 10% of the soil’s water holding capacity."
PRACTICES FOR MANAGING SOIL HEALTH
Decrease Inversion Tillage & Soil Traffic
- To manage or enhance soil health, it is important to reduce inversion tillage as excessive tillage can harm soil health in several ways. Tillage leads to an increase in oxygen in the soil, thus stimulating microbial activity, and resulting to the decomposition of organic matter.
- Tillage also rattles soil aggregates, exposing particles of organic matter that were already "physically protected within aggregates to microbial consumption." Organic matter levels may reduce after a while if additions are not enough to neutralize the losses from decomposition. This in turn reduces soil health.
- Inversion tillage decreases the soil coverage that crop residues provide, thus leaving the soil even more exposed to erosion. Tillage may also affect the hyphal network of mycorrhizal fungi, leading to their decline after a while.
- If not managed properly, a lot of inversion and non inversion tillage methods could compress the subsoil, causing a plow pan that inhibits root growth and access to nutrients in the subsoil.
- Excessive foot and wheel traffic, especially while the soil is wet and plastic, can compress the surface soil, impeding root growth and decreasing macro porosity.
- Of note, some tillage is still important in certain production systems, specifically organic systems that do not utilize herbicides to control weed.
Increase Organic Matter Inputs
- In order to increase soil organic matter levels, "inputs of organic matter must exceed the losses of organic matter due to decomposition."
- Healthy crops may be a beneficial source of organic matter. Crop residues should also be restored back to the soil as much as possible.
- Incorporating perennial crops or cover crops and cautiously adding compost and green manure are practices that can maintain or increase soil organic matter.
- When submitting soil fertility samples to a soil testing lab, one may ask for an organic matter analysis, as this can help in monitoring soil organic matter over time.
- It is important to ensure that organic matter comparisons over a period of time are based on data from labs using the same procedure for analysis or from the same lab, because results may vary significantly between analysis methods.
Make Use of Cover Crops
- Cover crops are known to add various benefits to soil health as they keep the soil protected during the winter or periods when the crops are not growing. This reduces the risk or erosion.
- The biomass that cover crops produce is put back to the soil, strengthening organic matter levels. Cover crops that have taproots typically create macro pores and reduce compression.
- Cover crops that are fibrous-rooted can even stabilize the soil and bolster aggregation. The cover crops that host mycorrhizal fungi can maintain and even increase these valuable fungi.
- Legume cover crops add nitrogen to the soil through the process of nitrogen fixation. Cover crops, in general, can "retain nitrate and other nutrients that are susceptible to leaching losses."
- It is important to cautiously plan the timing, application technique, and quantity of compost, manure, or any other form of fertilizer that minimizes nutrient excesses.
- While health plants that grow rapidly can withstand pest damage better, over fertilizing crops can lead to more pest issues.
- Boosting soluble nitrogen levels in plants can reduce their resistance to pests, leading to crop damage.
- It is necessary to maintain a soil pH that is appropriate for crops to be grown, as this will decrease toxicity and enhance nutrient availability. Retaining sufficient calcium levels will help earthworms thrive and enhance soil aggregation. Making use of different nutrient sources can help preserve soil health.
- Compost and manure offer organic matter, as well as, a wide range of nutrients, however, staying limited to just manure or compost can lead to excessive phosphorus levels in the soil.
- Combining "modest manure or compost additions to meet phosphorus needs with additional nitrogen inputs from legume cover or forage crops in a crop rotation can help balance both nitrogen and phosphorus inputs."
- Managing or improving soil health requires diverse crop rotations as this will help disintegrate soil borne pest and disease life cycles, eventually leading to the improvement of crop health.
- Crop rotations can also help in managing weeds. When diverse crops are grown, pests that thrive within a particular crop do not have the chance to build their populations over a period of time.
- Rotations can also assist in decreasing nutrient excesses.
CAUSES OF SOIL EROSION
Soil erosion occurs when the topsoil is worn out by farming activities like tillage or the natural physical forces of wind and water. There are several types of soil erosion, including water erosion, wind erosion, rill erosion, gully erosion, and ephemeral erosion. Soil erosion is mainly caused by:
Rainwater & Runoff
- Intense rainstorm and greater duration of rain may lead to soil erosion. The impact of raindrops on the soil surface can "break down soil aggregates and disperse the aggregate material."
- When rain falls in areas with hills, it washes the soil away. The running water deposits the "mineral-rich soil in the river bed." Over the years, this "deposition of soil can change the course of the river," leading to floods.
- The rate of soil erosion is more noticeable during heavy rain and less noticeable during light rain. While the soil erosion caused by less intense rain is not easily noticeable, its effect occurs over a long period.
- When water flows in rivers and streams, it often takes away the soils along its path, leading to increased sedimentation in streams and rivers and pollution.
- The increasing demand of the world's growing population for products like wheat and coffee leads to more land being cleared for agriculture.
- Replacing autochthonous trees with new tree crops that do not hold onto the soil allows the soil to be vulnerable to erosion. As time goes on, the most nutrient-rich part of the soil (the top soil) is lost.
- Deforestation also occurs when people cut down trees on a large scale to build houses, industries, or create products.
- Soil is held together by the roots of trees as this prevents the soil from getting uprooted. Deforestation may cause the topsoil to get eroded by wind and flowing water.
- While using chemicals "under the form of pesticides and fertilizers on (often) mono cultural crops is a very usual way of helping farmers improve their yields," excessively using phosphorus chemicals leads to "an imbalance of microorganisms in the soil moisture, stimulating the growth of harmful bacteria."
- The risk of erosion increases as the soil gets degraded and the "sediments sweep into rivers and nearby regions, possibly contaminating nearby ecosystems."
- Overgrazing is caused by "intensive cattle raising." Cattles allowed to graze the same field over a period of time may consume all the grass and their roots. These cattles can also crush the plants.
- This causes the topsoil to be vulnerable to wind and water, thus leading to soil erosion because plants do not have the required recovery period.
- It also causes the remaining soil to lose its infiltration capacity, leading to more water getting lost from the ecosystem.
- Overgrazing decreases the usefulness and productivity of the land. It reduces soil fertility, soil depth, and soil organic matter, which in turn affects the quality of the land.
REGIONS WITH SOIL EROSION
- Annually, Minnesota sees an erosion rate of more than 5.2 tons of soil loss per acre due to its relatively flat topography, carbonates in a lot of soils, and aggressive tilling.
- Minnesota farmers combat wind erosion by reducing its tillage intensity and the number of tillage passes.
- Minnesota sees a lot of wind. To slow wind speed, Minnesota farmers leave residue standing either by raising the "cutting height for small grains" or leaving "alternating strips of unchopped stalks."
- Farmers in Minnesota also use cover crops to increase yield and reduce soil erosion.
- North Dakota loses about 4.7 tons of soil per acre annually due to erosion. This state is vulnerable to wind erosion due to its flat topography and the fact that majority of its fields are left unprotected for 6-9 months of the year after fall tillage.
- The main measure North Dakota farmers have taken to reduce soil erosion is adding cover crops to protect the soil through the early spring months and winter. Ryegrass is an affordable coverage that protects the field from wind and water erosion.
- Vegetative buffer strips are also being planted to "trap sediment and slow wind speeds."
- Farmers in North Dakota are using healthy shelter belts to reduce wind speed and wind erosion.