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Stable aggregates are critical to erosion resistance, water availability, and root growth. Soils with stable aggregates at the surface are more resistant to water erosion than other soils, both because soil particles are less likely to be detached and because the rate of water infiltration tends to be higher on well aggregated soils. Unstable aggregates disperse during rainstorms, then form a hard physical crust when the soil dries. Physical crusts restrict seedling emergence because they have few pores for air and water entry into the soil. The crusts result in more runoff, more erosion, and less available water. Aggregated soils hold more water than other soils and provide pores for root growth. Large, stable aggregates can resist degradation and removal by wind better than small, weak ones.

Aggregate stability is a good indicator of the content of organic matter, biological activity, and nutrient cycling in the soil. The amount of organic matter increases after the decomposition of litter and dead roots begins. Stable aggregates result from this process because soil biota produce material that binds particles together. “New” organic matter stabilizes the larger aggregates, while the smaller aggregates are more likely to be bound by “old” organic matter. New organic matter holds and can release more nutrients. Changes in aggregate stability may serve as early indicators of recovery or degradation of soils and, more generally, of ecosystems. Perennial plants can often persist long after the soil and plant community have become too degraded to support.


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The amount of organic matter in the soil is a balance between additions of plant and animal materials and losses through decomposition and erosion.

Environmental factors interacting over time affect the amount of organic matter in soil. Rainfall and temperature affect plant productivity and the rate of organic matter decomposition. Increasing levels of organic matter promote a higher waterholding capacity, which results in increased plant growth and thus an increased amount of organic matter and plant nutrients.

Roots are the primary source of organic matter. Dead roots and gelatinous materials exuded by plant roots as they grow through the soil are decomposed by soil organisms and converted into organic matter. Since much of what is produced above ground is lost through photo-oxidation, the amount of root production is very important. Every year, about 25 percent of the total root biomass in areas of tall prairie grasses dies and becomes available for incorporation into the soil as organic matter. In the drier areas, such as areas of short prairie grasses, about 50 percent of the root biomass becomes available, but the total amount is less than that in the areas of tall grasses.

Plant composition and distribution control the distribution of organic matter. The horizontal and depth distribution of roots, the distribution of plants across the landscape, and the susceptibility of roots to decay vary among species. The roots of forbs and shrubs generally contribute less organic matter to the surface layer of the soil than the roots of grasses. Changes in the composition of plant species, especially from grasses to shrubs, affect the contribution of roots to soil organic matter. The organic matter is enhanced by litter beneath shrubs in areas of arid and semiarid rangeland. Fire initially reduces the amount of plant residue added to the soil. If the fire results in a shift from shrubs to grasses, however, the long-term effect can be an increase in soil stability and organic matter.

Soil organisms break down litter, dead roots, and organic matter into smaller fragments and compounds. As they decompose organic matter, they convert nutrients into plant-available forms and release carbon dioxide into the atmosphere. Warm, moist soil supports higher decomposition rates than waterlogged, dry, or cool soil.

Wind erosion and water erosion increase losses of organic matter. Erosion breaks down soil aggregates, exposing physically protected organic matter to decomposition and loss. Organic-rich soil from the surface layer is carried away by runoff or wind. Litter redistribution by wind or water from or to surrounding rangeland also affects the content of organic matter.

Grazing can change plant composition and distribution and increase or decrease the amount of organic matter in the soil. Grazing can increase the rate of root turnover, but overgrazing reduces the amount of plant energy available for the growth of new roots. Trampling by livestock can help to incorporate the plant material above the ground into the soil. In arid ecosystems, however, little plant material is available for incorporation. Trampling also breaks up soil aggregates, exposing organic matter to decomposition and loss through erosion.

Try some of the following management strategies in your garden this Summer. Your garden will thank you by providing you with a larger harvest. If the following information helps you please post a comment about it.

Management strategies

The following strategies can help to maintain the optimum content of organic matter in rangeland soils:

• Increase or maintain plant production.
• Promote the growth of species with high root production and promote a mix of species with different rooting depths and patterns.
• Promote the incorporation of above-ground plant material in moist plant communities with large amounts of standing plant material (e.g., areas of tall prairie grasses).
• Protect the soil from erosion by maintaining or increasing the plant cover and reducing the amount of bare soil.
• Properly manage grazing, fire, and vehicle use and thus promote the desired plant community and protect the soil
from erosion.


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What is compaction?

Soil compaction occurs when moist or wet soil aggregates are pressed together and the pore space between them is reduced. Compaction changes soil structure, reduces the size and continuity of pores, and increases soil density (bulk density). Wheel traffic or pressure (weight per unit area) exerted on the soil surface by large animals, vehicles, and people can cause soil compaction. In areas of rangeland, compacted soil layers are generally at the soil surface or less than 6 inches below the surface, although they can be as deep as 2 feet under heavily used tracks and roads. Increases in density can be small to large.

When is compaction a problem?

Compaction changes several structural characteristics and functions of the soil. It is a problem when the increased soil density and the decreased pore space limit water infiltration, percolation, and storage; plant growth; or nutrient cycling.

Water movement and storage.—Compaction reduces the capacity of the soil to hold water and the rate of water movement through soil. It limits water infiltration and causes increased runoff and, in some areas, increased erosion. Compacted wheel tracks or trails can concentrate runoff that can create rills or gullies, especially on steep slopes. When the amount of water that enters the soil is reduced, less water is available for plant growth and percolation to deep root zones.

Water entering the soil can perch on a subsurface compacted layer, saturating the soil to or near the surface or ponding on the surface. This water readily evaporates. Compaction can increase the water-holding capacity of sandy soils. An increase in the amount of water stored near the soil surface and a decrease in the amount of water deeper in the soil may favor the shallower rooted annuals over the deeper rooted plant species, such as shrubs.

Plant growth.—Where soil density increases significantly, it limits plant growth by physically restricting root growth. Severe compaction can limit roots to the upper soil layers, effectively cutting off access to the water and nutrients stored deeper in the soil. Anaerobic conditions (lack of oxygen) can develop in or above the compacted layer during wet periods, further limiting root growth. Even in arid climates, anaerobic conditions can occur where water accumulates.

Nutrient cycling.—Compaction alters soil moisture and temperature, which control microbial activity in the soil and the release of nutrients to plants. Anaerobic conditions increase the loss of soil nitrogen through microbial activity. Compaction changes the depth and pattern of root growth. This change affects the contributions of roots to soil organic matter and nutrients. Compaction compresses the soil, reducing the number of large pores. This reduction can restrict the habitat for the larger soil organisms that play a role in nutrient cycling and thus can reduce the number of these organisms.

Please be aware of soil compaction. Take action by preventing compaction in your town. Read up about some causes, effects, and control techniques at this Website


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What is infiltration?

The process of water soaking into the soil is infiltration. “Infiltration rate” is simply how fast water enters the soil and is usually measured in inches or millimeters per hour. This rate depends on soil texture (amount of sand, silt, and clay) and on soil structure. Soils in good condition have well developed structure and continuous pores to the surface. As a result, water from rainfall or snowmelt readily enters these soils.

Why is infiltration important?

Soil is a reservoir that stores water for plant growth. The water in soil is replenished by infiltration. The infiltration rate can be restricted by poor management. Under these conditions, the water does not readily enter the soil and it moves downslope as runoff or ponds on the surface, where it evaporates. Thus, less water is stored in the soil for plant growth, and plant production decreases, resulting in less organic matter in the soil and weakened soil structure that can further decrease the infiltration rate.

Runoff can cause soil erosion and the formation of gullies. It also carries nutrients and organic matter, which, together with sediment, reduce water quality in streams, rivers, and lakes. The sediment reduces the capacity of reservoirs to store water. Excessive runoff can cause flooding, erode streambanks, and damage roads. Runoff from adjacent slopes can saturate soils in low areas or can create ponded areas, thus killing upland plants. Evaporation in the ponded areas reduces the amount of water available to plants.

Please manage your soil properly in order to prevent the restriction of infiltration. Attempt to deter runoff that may cause gullies and other types of damage.


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Ecotone is a literary journal of place that seeks to publish creative work about the environment and the natural world while avoiding the hushed tones and clichés of much of so-called nature writing. In the natural world an ecotone is a landscape where two separate ecosytems overlap, a place of danger and opportunity for animals. As we try to reimagine a new literature of place, our journal embraces literary ecotones, writing that breaks across genres and seeks out edges. These edges—between science and literature, the urban and rural, the personal and biological—are places that are alive and electric, as well as new and dangerous.