Showing posts with label soil. Show all posts
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3:09 AM
Agronomy
Agronomy
Agronomy is a group of applied science disciplines concerned with land and soil management and crop production. Agronomists’ areas of interest range from soil chemistry to soil-plant relationships to land reclamation.

The word "agronomy" derives from the ancient Greek agros (field) and nemein (manage) and therefore literally means "field management". The American Society of Agronomy defines agronomy as "the theory and practice of crop production and soil management". There are many specialties within the study of agronomy.

Agronomic Specialties

Agronomy is the family of disciplines investigating the production of crops supplying food, forage, and fiber for human and animal use. It studies the stewardship of the soil upon which those crops are grown. Agronomy covers all aspects of the agricultural environment, from agroclimatology to soil-plant relationships.

It includes crop science, soil science, weed science, and biometry (the statistics of living things) as well as crop, soil, pasture, and range management; turfgrass; agronomic modeling; and crop, forage, and pasture production andutilization.


Within each area are subdisciplines. For example, within soil science are traditional disciplines such as soil fertility, soil chemistry, soil physics, soil microbiology, soil taxonomy and classification, and pedogenesis, the science of how soils form.

Newer disciplines within soil science include such studies as bioremediation, or the study of how living organisms can be used to clean up toxic wastes in the environment, and land reclamation, the study of how to reconstruct landscapes disturbed by human activities, such as surface mining.

Scientific Goals

Chief among detrimental human activities is poor field management, which leads to reduced productivity and reduced environmental quality. Historical examples abound; one is that of the 1930’s Dust Bowl in the United States.

In the early 1900’s much of the American Southern Plains, which had been natural grassland, was converted to wheatland. Planting and plowing methods of the time did not enable wheat to protect the ground against winds. Additionally, overgrazing of livestock had destroyed what grassland remained by the 1930’s.

The soil eroded, drought conditions which would last for most of the decade set in, and a series of wind and dust storms whipped through the region. An estimated 50 million acres of land were destroyed before soil conservation measures, implemented under the administration of Franklin Roosevelt, began to improve the situation.

It is the role of agronomy to manage soil and crop resources as effectively as possible so that the twin goals of productivity and environmental quality are preserved.

Agronomy treats the agricultural environment as humankind’s greatest natural resource: It is the source of food, clothing, and building materials. The agricultural environment purifies the air humans and other animals breathe and the water they drink.

Scientific Goals
Scientific Goals

Agronomists, whatever their specific field, seek to utilize soil and plant resources to benefit society. Crop breeders, for example, use the genetic diversity of wild varieties of domesticated plants to obtain the information needed to breed plants for greater productivity or pest resistance.

Soil scientists study landscapes to determine how best to manage soil resources. Integrating agricultural practices with the environment maintains soil fertility and keeps soil in place so that erosion does not reduce the quality of the surrounding environment.
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4:08 PM
Biofertilizers
Biofertilizers
The use of biofertilizers, biological systems that supply plant nutrients such as nitrogen to agricultural crops, could reduce agriculture’s dependency on chemical fertilizers, which are often detrimental to the environment.

Plants require an adequate supply of the thirteen mineral nutrients necessary for normal growth and reproduction. These nutrients, which must be supplied by the soil, include both macronutrients (nutrients required in large quantities) and micronutrients (nutrients required in smaller quantities). As plants grow and develop, they remove these essential mineral nutrients from the soil.

Because normal crop production usually requires the removal of plants or plant parts, the nutrients are continuously removed from the soil. Therefore, the long-term agricultural utilization of any soil requires periodic fertilization to replace lost nutrients.

Nitrogen is the plant nutrient that is most often depleted in agricultural soils, and most crops respond to the addition of nitrogen fertilizer by increasing their growth and yield. Therefore, more nitrogen is applied to cropland than any other fertilizer component.


In the past, nitrogen fertilizers have been limited to either manures, which have low levels of nitrogen, or chemical fertilizers, which usually have high levels of nitrogen. However, the excess nitrogen in chemical fertilizers often runs off into nearby waterways, causing a variety of environmental problems.

Less Harmful Alternatives

Biofertilizers offer a potential alternative: They supply sufficient amounts of nitrogen for maximum yields yet have a positive impact on the environment. Biofertilizers generally consist of either naturally occurring or genetically modified microorganisms that improve the physical condition of soil, aid plant growth, or increase crop yield.

Biofertilizers provide an environmentally friendly way to increase plant health and yields with reduced input costs, new products and additional revenues for the agricultural biotechnology industry, and cheaper products for consumers.

Nitrogen Fixing

Nitrogen Fixing
Nitrogen Fixing
While biofertilizers could potentially be used to supply a number of different nutrients, most of the interest is focused on nitrogen. The relatively small amounts of nitrogen found in soil come from a variety of sources.

Some nitrogen is present in all organic matter in soil; as this organic matter is degraded by microorganisms, it can be used by plants. A second source of nitrogen is nitrogen fixation, the chemical or biological process of taking nitrogen from the atmosphere and converting it to a form that can be used by plants.

Bacteria such as members of Rhizobium can live symbiotically in the roots of certain plants, such as legumes. Rhizobia and plant root tissue form root nodules, which house the nitrogen-fixing bacteria; once inside the nodules, the bacteria use energy supplied by the plant to convert atmospheric nitrogen to ammonia, which nourishes the plant.

Natural nitrogen can also be supplied by free-living microorganisms, which can fix nitrogen without forming a symbiotic relationship with plants. The primary objective of biofertilizers is to enhance any one or all of these processes.

One of the major goals for the genetic engineering of biofertilizers is to transfer the ability to form nodules and establish effective symbiosis to non-legume plants. The formation of nodules in which the Rhizobia live requires plant cells to synthesize many new proteins, and many of the genes required for the expression of these proteins are not found in the root cells of plants outside the legume family (Fabaceae). If transfer of the appropriate genes could be accomplished, Rhizobia could be used as a biofertilizer for a variety of plants.

There is also much interest in using the free-living, soil-borne organisms that fix atmospheric nitrogen as biofertilizers. These organisms, including types bacteria and algae, live in the rhizosphere (the region of soil in immediate contact with plant roots) or thrive on the surface of the soil.

Because the exudates from these microorganisms contain nitrogen that can be used by plants, increasing their abundance in the soil could reduce the dependency on chemical fertilizers. Numerous research efforts have been designed to identify and enhance the abundance of nitrogen-fixing bacteria in the rhizosphere.

Soil microorganisms primarily depend on soluble root exudates and decomposed organic matter to supply the energy necessary for fixing nitrogen. Hence, there is also an interest in enhancing the biodegradation of organic matter in the soil.

This research has primarily centered on inoculating the soil with cellulose-degrading fungi and nitrogen fixing bacteria or applying organic matter, such as straw that has been treated with a combination of the fungi and bacteria to the soil.
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9:01 AM
Compost is a mixture of organic ingredients used for fertilizing or enriching land. Composting is the practice of making and using compost.

Composting is a way for gardeners and farmers to enrich and otherwise improve the soil while reducing the flow of household waste to landfills. Essentially the slow, natural decay of dead plants and animals, composting is a natural form of recycling in which living organisms decompose organic matter.

The decay of dead plants and animals starts when microorganisms in soil feed on dead matter, breaking it down into smaller compounds usable by plants.

Collectively, the breakdown product is called humus, a crumbly, dark brown, spongy substance. Adding humus to soil increases its fertility. Compost and composting derive from the Old French composter, “to manure” or “to dung.”


History

The origins of human composting activities are buried in prehistory. Early farmers discovered the benefits of compost, probably from animal manure deposited on or mixed with soil.

In North America, American Indians and then Europeans used compost in their gardens. Public accounts of the use of stable manure in composting date back to the eighteenth century. Many New England farmers also found it economical to use fish in their compost heaps.

While living in India from 1905 to 1934, British agronomist Sir Albert Howard developed today’s home composting methods. Howard found that the best compost pile consists of three parts plant matter to one part manure.

He devised the Indore method of composting, alternating layers of plant debris, manure, and soil to create a pile. Later, during the composting process, he turned the pile or mixed in earthworms.

How Composting Works

Composting is a natural form of recycling that takes from six months to two years to complete. Bacteria are the most efficient decomposers of organic matter. Fungi and protozoans later join the process, followed by centipedes, millipedes, beetles, or earthworms.

By manipulating the composition and environment of a compost pile, gardeners and farmers can reduce composting time to three to four months. Important factors to consider are the makeup of the pile, the surface area, the volume, the moisture, the aeration, and the temperature of the compost pile.

Yard waste, such as fallen leaves, grass clippings, some weeds, and the remains of garden plants, make excellent compost material. Other good additions to a home compost pile include sawdust, wood ash, and kitchen scraps, including vegetable peelings, egg shells, and coffee grounds.

Microorganisms digest organic matter faster when they have more surface area on which to work, so gardeners can speed the composting process by chopping kitchen or garden waste with a shovel or running it through a shredding machine or lawn mower.

The volume of the compost pile is important because a large compost pile insulates itself, holding in the heat of microbial activity, which in turn accelerates decomposition.

A properly made heap will reach temperatures of about 140 degrees Fahrenheit in four or five days. Then the pile will settle, a sign that the process is working properly.

Piles 3 feet cubed (27 cubic feet) or smaller cannot hold enough heat, while piles 5 feet cubed (125 cubic feet) or larger do not allow enough air to reach the microbes in the center of the pile. These portions are important only if the goal is fast compost. Slower composting requires no exact proportions.

Moisture and air are essential for life. Microbes function best when the compost heap has many air passages and is about as moist as a wrung-out sponge.

Microorganisms living in the compost pile use the carbon and nitrogen contained in dead matter for food and energy. While breaking down the carbon and nitrogen molecules in dead plants and animals, they also release nutrients that higher organisms, such as plants, can use.

The ratio of carbon to nitrogen found in kitchen and garden waste varies from 15 to 1 in food waste to 700 to 1 in wood. A carbon-to-nitrogen ratio of 30 to 1 is optimal for microbial decomposers.

This balance can be achieved by mixing two parts grass clippings (carbon to nitrogen ratio 19:1) and one part fallen leaves (carbon to nitrogen ratio 60:1). This combination is the backbone of most home composting systems.

Uses and Practice

In the twenty-first century, composting remains an invaluable practice. In landfills, yard and kitchen wastes use up valuable space. These materials make up about 20 to 30 percent of all house-hold waste in the United States.

Composting household waste reduces the volume of municipal solid waste and provides a nutrient-rich soil additive. Compost or organic matter added to soil improves soil structure, texture, aeration, and water retention. It improves plant growth by loosening heavy clay soils, allowing better root penetration.

It improves the water-holding and nutrient-holding capacity of sandy soils and increases the essential nutrients of all soils. Mixing compost with soil also contributes to erosion control and proper soil pH balance, the amount of acidity or alkalinity present.

Some municipalities collect and compost leaves and other garden waste and then make it available to city residents for little or no charge. Some cities also compost sewage sludge, or human waste, which is high in nitrogen and makes a rich fertilizer. Properly composted sewage sludge that reaches an internal temperature of 140 degrees Fahrenheit contains no dangerous disease-causing organisms.

One possible hazard, however, is that it may contain high levels of toxic heavy metals, including zinc, copper, nickel, or cadmium.

The basic principles of composting used by home gardeners also are used by municipalities composting sewage sludge and garbage, by farmers composting animal and plant waste, and by some industries composting organic waste. Food and fiber industries, for example, compost waste products from canning, meat processing, and dairy and paper processing.
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