Soil quality is one of the most basic and perhaps least understood indicators of land health. Soil supports plant growth and represents the living reservoir that buffers the flows of water, nutrients, and energy through an ecosystem. The ongoing degradation of the earth"s soils by human activity, particularly agriculture, threatens human potential to feed a growing population. The annual global erosion amounts to about 36 billion tons, of which 10 billion are due to natural causes and 26 billion are the result of human activity (Crosson et al. 995).
The soil or runoff that has been eroded ends up in groundwater, lakes, streams, and rivers. The deposits of excess soil and the contaminates in it, cause further ecological complications. Bodies of water need to be dredged and monitored for contamination. Water levels are lowered with the increasing soil eroded into them, making our world"s water supply a concern directly related to the erosion of soil. The process of soil renewing itself is largely unknown. However, there is consensus on the need for conservation.
Evaluating the scope of the problem or predicting the effects that various solutions might have on agriculture and the environment is very difficult. Degradation is gauged for all soil in terms of compaction, erosion, nutrient loss and loss of organic matter. Soil quality refers to the capacity of a soil to perform these beneficial functions. Its texture, structure, water-holding capacity, porosity, organic matter content, and depth, among other properties determine a soil"s quality. Because soils naturally vary in their capacity to perform these functions, we must tie our understanding of soil quality to landscapes and land use.
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We must understand soil quality for two important reasons: First, we must match our use and management of land to soil capability. Second, we must establish understanding about soil quality so we can recognize ongoing trends. If soil quality is stable or improving, we have a good indicator that the ecosystem is sustainable. If soil quality is deteriorating, the larger ecosystem will almost certainly decline with it (Wilken 1995, Mirzamoatafa et al. 1998). Many conservation efforts are being taken to control soil erosion. In order to do this a universal language is need to measure soil erosion, texture, and the potential for erosion.
Soil loss tolerance ("T") is the amount of a given soil that can be displaced by water or wind erosion each year and be replenished through natural soil regeneration processes. This is a basis for evaluating the impacts of soil erosion and develops objectives for conservation treatment. Erosion at rates greater than T is a special concern because it threatens agricultural sustainability. Enrichment Ratios (ER) often used as a measure of the nutrients available for soil. It is a ratio of the intrinsic potential for soil displacement from erosion to the "T" limit (Baffaut et al 1998).
From 1991 to 1992 in Central Kenya"s highlands, these formulas were used to monitor runoff, soil loss, and enrichments of eroded soil material. Annual rainfall was 948 and 1125 mm for 1991 and 1992. Soil loss ranged from 0. 8 to 247. 3 tons, and runoff ranged from 1 to 89 mm. The enrichment ratios (ER) were [greater than or equal to] 1 and sediments were mostly enriched with P and Na. The P and Na concentrations were 4 to 10 and 2 to 3 times the source material. Sediment from the plots was 247 to 936% richer in P than the soil from which it originated.
Too much P can have negative effects on the plant and wildlife surrounding it. Changes in soil pH, percentage organic C, and percentage total N following erosion were significantly correlated with cumulative soil loss (r values of 0. 77, 0. 59, and 0. 71, n = 20). The data indicated that the unbalancing of nutrients in the soil is due to erosion, and one of the major causes of soil fertility depletion of Kenyan soils (Gachene et. al. 1997). The Universal Soil Loss Equation (USLE) estimates average annual soil loss from sheet and till erosion.
The equation is: A=RKLSCP, where A is the computed soil loss per unit area, R is a rainfall factor, K is a soil erodibility factor, L is a slope length factor, S is a slope degree factor, C is a crop practice factor, and P is a conservation practice factor (Baffaut et al 1998). Data from erosion plots in Tarija suggest only moderate rates of erosion (200tons-per. yr. ). Data at 6-min intervals for 41 sites in the tropics of Australia were used to compute the rainfall and runoff factor (R-factor) for the Universal Soil Loss Equation (USLE), and a daily rainfall erosivity model was validated for these tropical sites.
Mean annual rainfall varies from about 300 mm at Jervois to about 4000 at Tully. For these tropical sites, both rainfall and rainfall erosivity are highly seasonal. The daily erosivity model performed better for the tropical sites with a marked wet season in summer in comparison to model performance in temperate regions of Australia where peak rainfall and peak rainfall erosivity may occur in different seasons (Yu 1998). The Wind factor must be considered when evaluating soil erosion. Plant nutrients are transported in windblown sediment.
The Wind Erosion Equation (WEQ) is designed to predict long-term average annual soil losses from a field having specific characteristics. The equation is E=f (IKCLV), where E is the estimated average annual soil loss, I is the soil erodibility, K is the ridge roughness factor, C is the climatic factor, L is the equivalent unsheltered distance across the field along the prevailing wind erosion direction, and V is the equivalent vegetative cover (Baffaut et al. 1998). As validation for the Wind Erosion equation (WEQ) two field sites were established in southern Alberta (one in 1990, one in 1993).
At Site 1, total N in windblown sediment trapped at 25-cm height showed an average (13 events) enrichment ratio of 1. 11, while organic C in windblown sediment showed an average enrichment ratio of only 1. 02 compared with soil from the erodible surface. At Site 2, the average (4 events) total N enrichment ratio was 1. 08 and the average organic C (carbon) enrichment ratio was 1. 05. The results provide further evidence that every effort should be to prevent erosion of the thin layer of surface soil that ensures the future sustainability of agriculture (Baffaut et. al. 1998).
These examples of using universal formulas to measure soil erosion allow scientists to evaluate an area and compare efforts that are working else where and apply them to areas were soil erosion is in need of being lessened. During last 40 years, nearly one-third of the world land has been lost by erosion. This loss continues at a rate of more than 10 million hectares per year. The world population"s food demand is increasing at a time when per capita food productivity is beginning to decline (Pimentel et al. 1995). If conditions leading to famine are to be avoided, land that produces food must be preserved.
The ecological food web links plants, animals, and people must live in harmony with the planet"s water, soil, and atmosphere. Once those connections are severed the hunger web begins. To avoid these devastating effects, steps must be taking in all aspects of ecology. The greatest impact of soil erosion is farming practices that are ignorant to overall effects on the food web. The key to farming is to grow enough food for all of your people. When towns were made up of small farms this goal was more easily obtainable. When people stop farming, food production then became an industry where money takes precedent over soil.
Because of demand and economic reason farmers in the United States are destroying delicate balances in nature and drastically altering the landscape so that soil is at risk of erosion, and is eroded faster than it can be formed. (Pimentel, Resosudarmo1995) Agricultural practices of cropping and tillage are two important factors that influence runoff and soil losses. Much research had been done to show the effects of different tilling and crop rotations on soil erosion. Doyle"s (1996) research concluded that between 1982 and 1992 the US improved or at least had no increase in average erosion rates in most areas with extensive cropland.
Some of the improvement found was the result of crops being rotated and better tiling methods. Brown (et al 1998) investigated the effects of combining whey and straw in croplands. This research found that straw or whey alone reduces soil loss by 60-85 percent. When combined they reduce soil loss by 96- 98 percent. Ghidey and Alberts (1998) found through a study in Kansas that the annual runoff and soil losses from soybean cropping were slightly higher than those for corn. These studies and others like them have provided the knowledge of how to prevent further soil erosion.
The Conservation Reserve Program pays farmers to remove or add environmentally sensitive crops to their croplands (Ghidey, Alberts 1998). There are many casualties of conventional chemical farming: erosion, a decline in soil quality, water purity, weakened crop resistance to pests and diseases, and the safety of farm workers. According to US News & World Report, 9/14/92, an excess of $4 billion a year is spent on pesticides, fungicides, and herbicides Chemical farmers are still losing about a third of their crops each year to insects, diseases, and weeds.
Because of tilling practices, these chemicals used in farming not only effect the food produced and ground water but also the places where the runoff is deposited. Herbicide loss by runoff is a world wide problem. These contaminated runoffs kill a variety of wildlife, aquatic life forms, and many species of vegetation. An economical and environmental alternative to conventional farming is organic crop production. Organic farming is a soil management system that maintains and replenishes soil fertility. Organic foods are produced without the use of synthetic pesticides or fertilizers.
The strategy behind organic crop production is to produce food crops which are "processed, packaged, transported, and stored so as to retain maximum nutritional value without the use of artificial preservatives, coloring, or other additives. Allowable management techniques include: the use of cover crops, manures, and composts for soil fertility management, the use of mulches, hand or mechanical cultivation, and crop rotation for weed management, and production scheduling and crop selection for disease and insect management.
Organic farming is not as easy or as productive as conventional farming, especially on infertile sandy soils. To be successful, an organic farmer requires a sound knowledge of soil type, crop management and the incidence of pests and diseases in different seasons (Arden-Clarke et al 1987). Organic production preferably should be combined with systems not usually used in agriculture such as cover crops and livestock farming. This requires a larger area than the normal agricultural holding, which must be chosen carefully. The Department of Agriculture (Elliott et al. 1987) certifies organic production systems.
Certification involves the development of an organic plan for the operation, the plan to be evaluated and approved by an accredited agent, and the agreement of the farmer to abide by the list of approved substances. The organic agent also reviews soil and water tests, crop histories, production, and rotation plans. The area in which organic crops are to be grown must be chemical free for 3 years. They verify compliance with standards through annual and spot inspections, and record keeping requirements (Elliott et al. 1987). Consumers are demanding organically grown fruit and vegetables, and are willing to pay a higher price.
The sales of organic products have increased from $178 million to over $4 billion in 1998, and is growing in excess of 20% per year. These operations will focus on the production of lettuce, tomatoes, and cucumbers (Us News &World 1998). There is a demand for certified organic vegetables, especially with the new health awareness of the public. As with any type of farming, there is the risk of unfavorable weather and invasive pests, which could, reduced a season"s crop. Economics may be a large controlling factor for soil erosion. . When demand for grain increases, and supply decreases, price for food will increase.
Americans can afford to pay a few cents extra for bread, horse food, and rice but poorer countries will suffer when food becomes too expensive. Although the United States has been referred to as the "bread basket" of the world because of our impressive food production, our history constituted prolific amounts of soil erosion. During the 1930"s dust clouds forced people from their homes, killed humans and animals alike, and caused snow in Vermont to be black. Agricultural economists are aware that severely eroded soils are less productive--if too much soil is lost, the next planting and harvest are delayed.
Soils are less productive if crop planting has to be delayed. Instead of harvesting five times in one season, farmers might only reap three. Severely eroded soils have deficiencies in nutrient, bacteria, alterations in structure, and decreased resistance to pests. Continuously planting row crops, corn for example, can cause severe soil loss. Sustainable agriculture can prevent or lessen soil erosion and ensure higher productivity (Gardner 1996). Our county"s high demand for grain forces farmers to over work their land. The demand for this grain and the human consumption of grown vegetation are not the only factors leading to soil erosion.
The beef industry and our consumption of red meat impacts soil erosion as well. Of the total amount of grain that is grown in the US, 80% of it is fed to livestock. To support our meat centered diet, 260 million acres of U. S. forest must be cleared to create cropland for livestock (Gardner1996). Costa Rican produced beef is even more devastating to the environment. For every ? lb. of Costa Rican beef made, one acre of Costa Rican rainforest must be destroyed. This devastation is worsened by the deaths of all the plant and animal species that occur due to habitat loss (Gardner1996).
Because of the above reasons and several other moral, nutritional, and economical reasons, beef consumption is bad for the environment. Every individual who switches to a purely vegetarian diet (Gardner1996) spares one acre of trees each year. The factor of agricultural practices on soil erosion becomes more severe when forests, grasslands, and wetlands are destroyed. Roots from trees in forests, grasslands, and wetlands stabilize soil not only by holding earth, but also by intercepting precipitation, dispersing energy of raindrops, and by increasing infiltration and reducing runoff (Smith 1998).
Native Americans have used good agriculture practices for years. American Indians had respect for the land and all of its life forms. One of their cultural beliefs about farming is centered on the three sisters: corn, squash, and beans. The corn provides a stalk for beans to climb. Beans produce nitrogen that fertilizes the corn. And squash protects the soil and corn roots from the sun, traps moisture, and prevents erosion. All three plants provide edible food, while preserving soil. (Wilken 1995)
It is essential to the survival of the human race, and all other life forms that several forms of soil conservation practices are used. There is a finite amount of food that our country can produce before our production starts to decrease. Although erosion is a natural process, humans have found several unnatural ways to make soil erosion more severe. To be able to continue to feed the growing population and preserve the species diversity of wildlife and plants we need to have sustainable agriculture practices and soil conservation these efforts are crucial in the prevention of extensive soil erosion.
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