Soil Conservation Assessing the National Resources Inventory, Volume 1 (1986) / Chapter Skim
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4. On-Farm and Off-Farm Consequences of Soil Erosion
4. On-Farm and Off-Farm Consequences of Soil Erosion
Pages 62-74
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From page 62... ...
General findings of recent research on the major on-farm and offfarm consequences of soil erosion, focusing on research applications of NRI data, are summarized in this chapter. This research much of which was possible because of the availability of NRI data attempts to quantify basic reasons for conserving soil: reducing the impact of soil erosion on farm production costs and productivity in terms of yield and mitigating costs associated with offsite damages caused by erosion.
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From page 63... ...
In areas of rapidly developing severe gully problems, farm production costs can be increased through damages to farm equipment from crossing gullies and the greater fuel and labor requirements needed to farm around gullies. Except in areas of concentrated flows or where wind abrasion is severe, short-term effects of erosion on farm production costs and profits can be gradual and subtle.
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From page 64... ...
. Soil erosion and associated water runoff can increase short-term farm production costs in several ways, including loss of plant nutrients and damage to machinery incurred when crossing the channels left by runoff.
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From page 65... ...
Such eroded sites usually have less capacity to supply soil moisture or plant nutrients in forms readily available to growing crops. With time, farm production costs increase because more fertilizer, more careful tHlage operations, or other changes in management are required to attain a given crop yield.
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From page 66... ...
For example, crop yield mightbe increased bytechnological acivancesthatare inclepenclentof inherent soil productivity, such as hybrid seed and improved chemical weed-control systems. To evaluate the effects of erosion in such instances, it is necessary to focus on the impact of erosion damage on attainable yield levels, taking into account the effects of technological advances.
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From page 67... ...
Proper interpretation of the stated hypotheses and the experimental results is important. Long-term productivity losses might come about through reduced optimal yields or through higher costs to attain optimal yields.
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From page 68... ...
Results have helped researchers quantify the impact of on-farm erosion damages and have drawn attention to the need for improved soil conservation practices. Empirical studies have also helped researchers identify the soil characteristics and management practices that most significantly influence erosion-productivity damage under many field conditions.
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From page 69... ...
As refined by a research team at the University of Minnesota, the PI model allows comparisons of soil productivity between an ideal soil, in which bulk density, pH, aeration, and available water storage capacity are optimal for root growth, and any other soil for which values for these parameters are available (Pierce et al., 1983~. The computerized data base composed of county-level soil surveys, Soils-5, contains such information for thousands of soil profiles.
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From page 70... ...
Vulnerability increases with increasing V values. Table 4-1 indicates that there are exceptions to the general observation that high rates of erosion are associated with significant soil productivity damages.
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From page 71... ...
Erosion-productivity problems are not uniformly distributed across the country, within regions, or in individual fields of cropland. Assessments of erosion damages that emphasize average reductions in crop yields or other measures of productivity can underplay the more serious, geographically concentrated instances of severe erosion-induced productivity damages.
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From page 72... ...
The model draws upon NRI erosion estimates to develop baseline conditions and can simulate erosion rates and long-term productivity effects that would be expected from alternative cropping and conservation management conditions. In view of the importance of testing the interactive effects of technology and erosion damage on crop yields and other measures of productivity, the EPIC model, used in conjunction with erosion information from the NRIs, is a potentially useful tool for scientific research and policy analysis.
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From page 73... ...
The committee believes that strategies for protecting the quality of surface water and groundwater will have to consider the possibility that groundwater pollution can be aggravated by techniques intended to mitigate erosion problems. Conservation practices often rely more heavily on agricultural chemicals than conventional management and at the same time increase infiltration of water, which may aggravate pollution of groundwater.
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From page 74... ...
The difficulty is in translating these potential loads into actual sediment levels observed in watercourses and then assessing the damage caused by the added sediment. NRI values for select physical factors of the USLE can be helpful in analyzing surface water quality when properly integrated into mathematical models such as those mentioned in Chapter 3.
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