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Soil erosion is considered the biggest contributor to nonpoint source pollution in the United States according to the U.S. Environmental Protection Agency and the federally mandated National Pollution Discharge Elimination System. Soil loss rates from construction sites can be 10 to 20 times that of agricultural lands. The use of surface applied organic amendments has been shown to reduce runoff and erosion, however, with the exception of animal manure, little research has focused on nutrient loss from these amendments. Four types of compost blankets, hydroseed, silt fence, and a bare soil (control) were applied in field test plots. Treatments were seeded with common bermuda grass. A rainfall simulator applied rainfall at an average rate equivalent to a 50 yr hr −1 storm event (7.75 cm hr −1 ). Three simulated rain events were conducted: immediately after treatment application, at three months when vegetation was established, and at one year when the vegetation was mature. After three months, the compost generated five times less runoff than hydroseed with silt fence, and after one year, generated 24 percent less runoff. All treatments proved better than the control at reducing solids loss. Total solid loads were as much as 3.5 times greater from hydroseed and silt fence compared to the composts during the first storm, and as much as 16 times greater during the second storm. Materials high in inorganic nitrogen (N) released greater amounts of nitrogen in storm runoff; however, these materials showed reduced N loss over time. Hydroseeding generated significantly higher total phosphorus (P) and dissolved reactive P loads compared to compost in storm runoff during the first storm event.

Organic farming offers an alternative that can eliminate many of the environmental problems of conventional agriculture in the industrialized world. Instead of using petroleum-derived chemicals to fertilize and protect crops, farmers manage their fields so as to take advantage of naturally-produced composts and mulches that recycle nutrients, and control pests and weeds. However, organic farming is often logistically inefficient, because these organic composts and mulches are bulky and difficult to transport. Alleycropping as practiced in the tropics may be able to make organic farming more efficient in the southeastern United States. In this form of alleycropping, trees or shrubs, often leguminous, are planted in hedgerows between open spaces ('alleys') where the crop is grown. The hedgerow species are periodically pruned (both aboveground and belowground), and prunings fall directly onto or into the soil where the crop is growing. These prunings add carbon and nutrients to the soil, and provide mulch that helps suppress weeds. Use of prunings reduces the need for composting and hauling manures and mulches, thereby increasing the efficiency by which organic material is supplied to the soil that supports the economic crop. In Georgia, dry weight annual production of prunings reached up to 18.4 Mg ha^sup -1^, a quantity high enough to maintain crop production. Thus, alleycropping may be feasible for organic farmers in the southeastern United States.[PUBLICATION ABSTRACT]

Compost and mulch blankets have been widely used for slope stabilization and erosion control at construction sites; however, the majority of research on these erosion control blankets has failed to meet state or federal specifications for particle size distribution. The primary objective of this study was to determine how blending wood mulch with compost may affect its performance as an erosion control practice relative to a straw blanket with polyacrylamide (PAM). The secondary objective of this study was to determine if particle size distribution of the organic erosion control blanket affects runoff, erosion, and vegetation establishment. Researchers concluded that the greater percent of compost used in an erosion control blanket, the lower the total runoff and the slower the runoff rate. Compost erosion control blankets retained 80% of the simulated rainfall applied and reduced cumulative storm runoff by 60%, while the wood mulch blankets reduced runoff by 34% and straw with PAM by 27%. Conversely, the greater the percent of mulch used in the erosion control blanket, the lower the sediment and suspended sediment load. However, any combination of compost and mulch reduced runoff volume, runoff rate, and soil loss relative to a straw blanket with polyacrylamide. The average cover management factor (C factor) for the straw with PAM was 0.189, the compost blanket was 0.065, and the mulch blanket was 0.013. Researchers also concluded that particle size distribution of the compost and mulch blankets was the leading parameter that reduced soil loss and runoff. If particle size distribution specifications are not followed, total soil loss can be four times greater, suspended solids can be five times greater, and turbidity can be eight times greater, relative to blankets that meet particle size distribution specifications. Nitrogen and phosphorus loading from mineral fertilizer used with conventional straw blankets may lead to increased nutrient loading of receiving surface water relative to the compost and mulch blankets. The straw blanket with fertilizer increased total Kjeldahl nitrogen loading by more than 8,000%, the compost blanket increased total Kjeldahl nitrogen by 340%, and the mulch blanket by 18% relative to the control. Although the bare soil and mulch blanket treatments did not contribute any soluble phosphorus (P) to runoff, relative to the compost blanket, the soluble P load from the straw blanket with PAM was 3,800% greater. Results from this study may be used to revise particle size specifications for compost erosion control blankets and to help regulators and design professionals determine which type of erosion control best management practice is best for their particular application.

Soil erosion is one of the biggest contributors to nonpoint source pollution in the United States. Soil loss rates from construction sites are 10 to 20 times that of agricultural lands. The use of surface applied organic amendments has been shown to reduce runoff and erosion through enhanced vegetation growth and soil quality characteristics. The objective of this study was to evaluate the vegetation growth and soil quality effects from compost blanket and hydroseed applications to soils disturbed by construction activities. Four types of compost blankets, two hydroseeded treatments (silt fence and mulch filter berm) and a bare soil (control) were applied in field test plots. Treatments were seeded with common Bermuda grass ( Cynodon dactylon ). Vegetative growth (percent cover and biomass of weeds and grasses) and soil quality characteristics were evaluated periodically over one year and 18 months, respectively. Results showed compost blankets provided an average of 2.75 times more vegetative cover than hydroseed after three months. After one year, cover was similar, but hydroseed had significantly greater weed biomass than compost and a greater ratio of weed biomass relative to Bermuda grass biomass. One type of compost blanket increased surface soil extractable organic carbon, and another type increased organic matter in 0 to15 cm (0 to 6 in) soil depths relative to hydroseed treated soils. A one-time application of hydroseed that included mineral phosphorus (P) fertilizer elevated surface soil P after 18 months. On construction sites where disturbed soils are prone to erosion and vegetation establishment is required, compost applications will promote quicker vegetation cover with less weed growth than hydroseeding. Some compost erosion control blankets have the ability to increase soil quality characteristics relative to hydroseed applications within 18 months of application.

The Everglades in southern Florida, U.S.A., is a major focus of conservation activities. The freshwater wetlands of the Everglades do not have high species richness, and no species of threatened aquatic animals or plants live there. We have, however, identified a distinctive ecological feature of the Everglades that is threatened by canal construction, draining, and nutrient enrichment from agricultural runoff. Compared to values reported from other freshwater systems, standing stocks of periphyton in relatively undisturbed areas of the Everglades were unusually high, and standing stocks of invertebrates and fish were unusually low. Averaging data gathered from nine sites and five sampling periods spanning 1 year, we found that periphyton standing crop was 88.2 g/m2(ash-free dry mass), invertebrate standing stock was 0.64 g/m2(dry mass), and fish standing stock was 1.2 g/m2(dry mass of large and small species combined). We found that fish standing stocks were much higher in phosphorus-enriched sites than in nearby reference sites but that invertebrate standing stocks were similar in enriched and reference sites. Our results support the notion that oligotrophy is at least partially responsible for the low standing stocks of fish, but they also suggest that species interactions and a paucity of deep-water refugia are important. Anthropogenic eutrophication in Everglades marshes will lead to the loss of distinctive ecosystem features. A focus on species richness and \"hot spots\" of threatened species provides no basis for conservation of ecosystems like the Everglades. If oligotrophic ecosystems often have low species richness, they will be underrepresented in preservation networks based on some common criteria for establishing conservation priorities.

Information about the costs and labor requirements of experimental organic farming systems designed to restore highly degraded soils in the southeastern US are needed. Enterprise budgets were prepared for the production of okra, hot pepper and a corn/winter squash intercrop under 10 different production systems, nine of which were based on organic conservation tillage. A stochastic dominance analysis was conducted to determine the relative risk efficiency of the 10 systems over the course of the experiment in terms of productivity, profitability and carbon sequestration potential. Organic conservation tillage treatments had lower tractor labor and fuel costs than conventional treatments, due to the extensive tillage required in conventional vegetable farming. The subset of organic treatments receiving compost addition without additional mulches also demonstrated increases in soil carbon, an important driver of system productivity. Organic treatments had little pest and pathogen pressure, with the exception of Fusarium wilt in some treatments receiving straw mulch. Weed suppression by straw mulches reduced labor requirements by an average of 23%. Yields in all treatments were lower than conventional yields from other studies in the region, due to the degraded nature of the soil on the study site. However, net returns on high-labor, organic crops were over US$30,000 ha−1 in some treatments. The results of this work indicate that organic, conservation tillage systems can restore soil productivity and command high returns per hectare if labor requirements can be met.

This work presents the results of a three-year field study of agroecosystems designed to restore soil organic matter (SOM) to degraded soils of the Georgia Piedmont. The systems combine a suite of management practices previously demonstrated to increase SOM when studied individually, and examine the effects of these techniques when used in combination in a cropping systems context on soil characteristics, crop production and weed biomass. The systems' components include organic management, alley cropping with perennial legumes, conservation tillage, use of winter cover crops, straw mulch and two compost application rates. Vegetable crops grown were a rotation of okra, hot pepper and a corn and winter squash intercrop. The systems were not able to maintain soil C or N without the addition of compost. Systems incorporating alley cropping, organic management, conservation tillage and compost maintained soil C, and increased in soil C when mulch was not applied. In organic, conservation tillage without alley cropping, soil C did not change significantly, even with annual 44.8 Mg ha−1 of compost additions. Patterns for soil N followed those of soil C. The study demonstrated that alley cropping can maintain and sequester soil C and N beyond organic conservation tillage alone, and more than conventionally tilled, chemically fertilized treatments. Crop yields did not vary by treatment due to high variation within treatments. Winter cover crop residue provided an effective weed barrier for 4 to 6 weeks in the spring, but additional hand weeding was required throughout the summer. The results of this systems-level study demonstrated interactions between management practices when used in combination that would not have been observed when studied individually. It also demonstrates that agroforestry techniques, conservation tillage and compost applications can increase soil C in degraded, clayey soils while they are in cultivation.

Increased organic matter input into weathered and infertile soils through agricultural techniques such as minimum tillage or agroforestry can improve P availability to crops. Organic matter is an energy source for microbes, and their activity may be responsible in part for increased levels of labile P. The objective of the work reported here was to examine, in a highly weathered Ultisol, the influence of microbial activity in mobilizing P, maintaining it in a plant-available state, and preventing its fixation, and the effect of N and biocides on these processes. Exchangeable aluminum and soil moisture were also determined, since they interact with microbes and soil P. Results showed that increased microbial activity reduced sorption of dissolved and organic P by soil, maintained inorganic P in soluble and labile pools, increased microbial P, decreased mineral P, increased exchangeable Al, and increased water retention. Additions of N and biocides had variable effects, probably due to complex interactions between N, degrading biocides, and microbial populations.

The contribution of tropical rain forests to the global nitrogen cycle is considered to be important in view of the extent they cover and of the possible effects of their destruction. Few complete studies have been made of nutrient cycling - including nitrogen - of tropical rain-forest ecosystems. From the information available, a wide variation in nitrogen distribution and cycling patterns points towards a more complex set of strategies previously ignored. As part of the Venezuelan MAB-1 International Project at San Carlos de Rio Negro, the nitrogen cycle of a tropical rain forest is being studied at sites of low mineral nutrient status. These studies of the Amazonian caatinga forest represent a contrast to similar studies carried out at more fertile sites elsewhere in the tropics. The partitioning of the 2087 kg ha⁻¹ of total N among the different ecosystem compartments favours the living parts by over 55%. Litter contributes 6%, and the soil to rooting depth slightly over one-third. The root compartment is the most important N pool with 40% of total N. Input by rain is comparable to output by stream discharge, and is of the same order of the annual turnover in above-ground litter. Internal cycling of N by retranslocation before leaf abscission and scavenging are important processes involving fluxes of the order of 9 kg ha⁻¹ yr⁻¹. Biological fixation occurs in or around roots, lichen-covered bark and leaf surfaces. Estimated rates of 30 to over 100 kg ha⁻¹ yr⁻¹ would suggest that significant gaseous losses might be expected if the system were at a steady state. Experiments show that nitrification is hindered in the soil and that the predominant ion is accordingly $NH_4^ + $. Large-scale perturbations would probably destroy the nitrogen-conserving mechanisms and induce severe losses.

Nutrient balance studies of mature ecosystems have shown that in many cases leaching losses are greater than atmospheric inputs. If the systems are not degrading, this means this means that the net losses must be compensated for by weathering of parent material. In contrast to ecosystems with rates of nutrient leaching that are higher than rates of atmospheric input, leaching of nutrients from an Amazonian rain forest ecosystem was less than or equal to input from the atmosphere every year between 1975 and 1980. If this forest is not aggrading this means that weathering of parent materials does not play an important role in the nutrient economy of the ecosystem. The forest apparently maintains itself on nutrients derived from the atmosphere.