A erosão hídrica é a principal causa de degradação do solo em ambientes tropicais e subtropicais úmidos e a perda da camada superficial do solo é o maior desafio para sustentabilidade da agricultura no mundo. Ela afeta a qualidade e o volume dos corpos d\'água e diminuí a qualidade dos solos. Apesar disso, o mercado não é capaz de corrigir estes problemas em razão da sua característica de bens públicos (não-exclusividade e não-rivalidade). Assim, o controle da erosão agrícola gera um serviço benéfico para toda a sociedade, mas os seus custos são exclusivamente dos agricultores. Pagamentos por Serviços Ambientais - PSA são mecanismos de compensações em que os beneficiados pelos serviços pagam os seus provedores. PSA são mecanismos promissores para o financiamento da proteção ambiental e podem complementar as atuais regulações. Entretanto, a literatura atual ainda é limitada em termos de quantificação dos serviços gerados, da sua demanda e sua viabilidade econômica. Este estudo analisa a viabilidade econômica de esquemas de PSA para o controle da poluição hídrica advinda da agricultura no Brasil. O objetivo específico do estudo é estimar ofertas de Serviços Ambientais - SA de conservação do solo. As ofertas de SA foram estimadas para áreas de cana-de-açúcar (na Bacia do Rio Corumbataí) e horticultura (na Sub-Bacia Cabeceiras do Tietê) utilizando uma metodologia de dados mínimos. As ofertas foram estimadas para diferentes práticas agrícolas, permitindo a comparação da eficiência das diferentes práticas na produção do SA. No caso da cana, a implantação e manutenção de florestas nas APPs mostrou-se a prática mais eficiente. Gastos de R$150,00/ha/ano com esta prática conservam cerca de 140.000 Mg de solo, enquanto o mesmo gasto aplicado na prática de não utilização das APPs conserva 70.000 Mg. Os resultados indicam que existe potencial para aplicação do modelo como forma de integrar as políticas públicas agrícolas com as ambientais. O estudo mostra que a adoção de práticas com maior produção de SA depende de incentivos. Nas condições atuais elas não são atrativas na medida em que geram menores retornos aos agricultores. Os incentivos podem ser através de subsídios das práticas adequadas, estímulo à demanda de produtos ambientalmente amigáveis ou pagamentos diretos pelos SA produzidos. / Water erosion is the main cause of soil degradation in tropical and sub-tropical environments and top soil loss is the biggest challenge for sustainable agriculture in the world. It affects water quality and quantity, and decreases soil quality. Despite this, the market is not able to solve these problems because of their public good characteristics (non-rivalness and non-excludability). Agricultural pollution control by farmers is a service society free rides because only farmers pay its costs. Payments for Environmental Services - PES schemes are flexible mechanisms in which providers of these services get paid by their users. PES schemes are considered to be promising mechanisms for financing environmental protection and restoration as well as for complementing and enforcing regulations. However, most of the on-going schemes don\'t use studies to quantify the services produced, to analyze the demand for them, or to check the schemes\' economic viability. This study analyses the economic viability of PES schemes in order to control the agricultural pollution of water resources in Brazil. The specific objective is to estimate the Environmental Services - ES of conservation soil supplies. These supplies were estimated for sugar cane (Corumbataí Watershed) and horticulture areas (Tietê Cabeceiras Subwatershed), using a minimum-data model. The supplies were calculated for different practices, so it is possible to compare the different practices\' efficiency to produce ES. For the sugar cane area it is more efficient to plant trees in the riparian buffer zones. Paying 150 reais per ha per year produces 140.000 Mg of conserved soil through tree planting, while with the same amount, the exclusion of the riparian zones from cultivation produces approximately 70.000 Mg. The results show this model can be applied as a way of integrating agricultural and environmental public policies. It was concluded that incentives are necessary to make the farmers adopt the practices that produce ES, because they are not economically feasible under current market conditions. The incentives could be either subsidies for these practices, fostering the demand for environmental friendly products, or direct payments for the ES produced.

The agricultural production of peppermint has been shown to contribute significant quantities of nitrate-nitrogen to groundwater recharge. In an effort to provide new tools for increasing nitrogen efficiency within peppermint production, three research questions were proposed: i) How should plant tissue samples be collected to achieve the greatest precision when using the mint stem nitrate test for nitrogen management?; ii) What is the consumptive use of water by peppermint in the post-harvest period?; and iii) How does irrigation uniformity affect nitrate loading to groundwater when N is supplied through chemigation? In the first investigation, structured field experiments were designed and conducted on commercial peppermint fields to isolate potential environmental, management, and sampling influences on stem nitrate test results. The most significant effects observed were those of the type of stem material collected (a 441% effect at p<0.001) and the number of stems collected to estimate the field mean concentration. It was found that the variance of the sample population and the number of stems required for a given sampling error could be greatly reduced by only collecting stems from within the plant canopy. Less pronounced but statistically significant differences in stem nitrate concentrations were produced by variations in solar radiation on hourly (a 17% effect at p<0.05) and daily (a 29% effect at p<0.01) scales. In an analysis of stem nitrate spatial variability, a purely random distribution of stem nitrate concentrations was observed on the 1-150 m scale. For the second investigation, a field study was conducted to measure the consumptive use of peppermint in the post-harvest period and to develop crop coefficients (Kc) used to predict evapotranspiration rates. The soil water balance was measured on two fields with a neutron moisture probe over an 80 day period. Over the 49 days following harvest, a cumulative consumptive use of 96 mm was observed. Basal crop coefficients increased from near zero to approximately 0.40 within 40 days post-harvest. The third, and final, investigation developed a simple heuristic statistical model to explore the effective adequacy of chemical application as influenced by the uniformity of irrigation. To perform this analysis, an expression was presented whereby irrigation distribution parameters for the normal, or Gaussian, model could be derived from common irrigation design terms. The results of this model indicate that the effective chemical adequacy is greatly compromised when the irrigation uniformity coefficient is low and/or the design irrigation adequacy is high. / Graduation date: 1998

Small commercial and non-commercial animal enterprises (SCAEs) raise a few beef cows, horses, pigs, sheep, poultry, and other animals on a few acres. These enterprises are often located in suburban areas of watersheds and show potential for degrading water quality through to increased bacterial, nitrogen, and phosphorus concentrations. SCAEs implement Best Management Practices (BNIPs) on a voluntary basis to control their water quality impacts. Off-stream watering areas, with animal access to streams, and covered manure storages are two BMPs which were analyzed in this thesis for effectiveness in reducing bacteria, nitrogen, and phosphorus from entering surface and groundwater in four SCAEs. The four cooperating SCAEs were located in the Tualatin River Basin, and the potential water quality improvements from implementing these two practices in all SCAEs in the basin were discussed. The BMP analyses use results from several studies. Two of these studies analyzed off-stream watering areas for reducing time animals spend watering at the stream. This time was measured and used to estimate the manure defecated in the stream. Reducing time animals spend at the stream decreases direct defecations in the stream and reduces water quality impacts of SCAEs. A third study analyzed a pasture pump as a possible off-stream watering device. It was analyzed for its ability to provide water to 27 Holstein dairy heifers without limiting water consumption. Daily water consumption from the pasture pump was not significantly different than daily consumption from an open water trough. A fourth study predicted the rainfall required to produce runoff from pastured areas in the Dairy-McKay Hydrological Unit Area within the Tualatin River Basin. These required rainfall amounts and runoff frequency were predicted for summer and winter soil conditions. The BMPs were analyzed for a variety of wet and dry conditions during the summer and winter. Off-stream watering areas were most effective in reducing water quality impacts of SCAEs for dry conditions during the summer and winter, while the covered manure storages were most effective during winter days of continuous rain. Off-stream watering areas reduced the time animals spent at the stream by 75%. Consequently, defecations at the stream were assumed to be reduced 75% and the SCAEs'water quality impacts decreased. Covered manure storages protect manure piles from rain and surface water runoff and prevent bacteria and nutrients from entering the stream or leaching to groundwater regardless of the weather. However, the amount prevented varies with weather conditions. An uncovered manure pile was estimated to cause no water quality impacts during dry weather. During wet weather, the bacteria and nutrients reaching the stream from an uncovered manure pile was estimated to be 60% of the quantity released. The maximum amount of nitrogen leaching to groundwater was estimated to be 10% of the amount applied to the pile since the previous rain. In addition to implementation costs of BMPs, there are changes in annual revenue and costs associated with the management changes. Partial budget analyses were conducted for the four SCAEs to determine their changes in annual monetary returns to management. Both BMPs resulted in negative changes in annual returns to management for all four enterprises. / Graduation date: 1994

Pima Association of Governments 208 Project / Nonpoint Source Pollution, A Report on Tasks 5321, 5327, and 5332 / Prepared by: Water Resources Research Center and College of Agriculture / The University of Arizona, November 1977

Nitrate pollution of ground and surface water can stem from the mismanagement and over-application of both inorganic and organic fertilizers. This results in the occurrence of non-point externalities, which infringe on the overall level of social welfare. Market based environmental policies, known as economic instruments, can be developed to curb the level of this non-point externality. Such policies directly affect the management decisions of agricultural producers, providing them with incentives to change their management practices. The overall objective of this study is to analyze an array of economic instruments which could feasibly curb water quality degradation resulting from the over-application and misuse of manure and inorganic fertilizers in agricultural production. The economic instruments are compared in terms of their relative effectiveness in decreasing nitrate water pollution and social damage. This thesis develops a three agent manure market model, wherein a vegetable producer and composter can purchase manure from a dairy producer or inorganic fertilizer from an exogenous fertilizer market. The production activities of each agent are modelled using real world production data. A non-linear programming technique is used. The imposition of a percentage manure tax was found to alter the vegetable producer’s derived demand for manure, and resulted in less manure being exchanged between the dairy and vegetable producers. The provisions of a percentage manure composting subsidy increased the quantity of manure demanded by the composter and decreased the amount of manure consumed by the vegetable and dairy producers. The imposition of an inorganic fertilizer tax increased the demands for manure fertilizer, as did the manure application limit. The effects on social damage are dependent on the leaching and surface run-off susceptibilities of each operation’s associated land base. The composting subsidy appeared to be the most efficient instrument for decreasing the overall level of social damage, when qualitatively analyzed. It induced decreases in the demand for manure by both the dairy and vegetable producers, while increasing the demand for manure of the composter. This results in an overall social benefit. There must be, however, financial justification for the implementation of such an instrument.

Eutrophication impacts the quality of many surface waters worldwide. Algal blooms threaten lake water quality and in order to control their growth, understanding of nutrient transport at the field-scale is essential. In order to accomplish this, a combination of field monitoring and computer modeling with the SWAT model was undertaken. / Four sites located in the Pike River watershed of southern Quebec were instrumented to monitor nutrient losses from both clay loam and sandy loam soils under both subsurface and naturally drained conditions. Results illustrate how the presence of subsurface drainage influences phosphorus loss depending on soil texture and structure. Total phosphorus loss from the clay loam subsurface drained site was 4.0 kg ha-1, 55% greater than the naturally drained clay loam site. Total phosphorus loss from the sandy loam subsurface drained site was 1.2 kg ha-1, 14% less than the naturally drained sandy loam site. Total phosphorus losses from the subsurface drainage systems in the clay loam field and the sandy loam field were 2.3 and 0.4 kg ha-1, respectively. Particulate phosphorus was the dominant (78%) form of phosphorus loss from the subsurface drainage system at the clay loam site. This indicates that bypass flow through the soil profile in the clay loam field led to excessive total phosphorus loss. / SWAT, a watershed-scale model was calibrated with over 6 site years of data, in an attempt to simulate hydrology and pollutant transport at the field-scale. After calibration, the monthly Nash-Sutcliffe Efficiency varied from 0.09 to 0.74 for total drainage; 0.04 to 0.71 for sediment loading; 0.29 to 0.48 for nitrate loads and 0.28 to 0.64 for total phosphorus loads. Overall, SWAT has shown that it has the ability to simulate long-term sediment and nutrient transport at the field-scale. This makes SWAT a valuable tool for the development and evaluation of various beneficial management practices which control sediment and nutrient loss from agricultural fields.

In the Missisquoi Bay of Lake Champlain situated in the South of Quebec, phosphorus originating from agricultural sources has been found to be a major contributor to the deterioration of water quality. This study sought to evaluate the nutrient loads, most particularly phosphorus, exported through surface runoff and tile drainage from two agricultural fields of the Missisquoi Bay watershed. As part of the study, a phosphorus simulation model was tested on one agricultural field. The evaluation of FHANTM 2.0 assessed the model's capacity to simulate the transport of phosphorus on agricultural fields. / From the two experimental fields studied, the results showed that the mean phosphorus load exported was larger in surface runoff than in tile drainage. The mean phosphorus load exported was 1.21 kg ha-1yr -1 in surface runoff, and 0.61 kg ha-1yr-1 in tile drainage. In contrast, nitrate loads exiting the fields were larger in tile drainage than in surface runoff. Over the two year study, the mean nitrate load was 5.64 kg ha-1yr-1 in surface runoff, and 91.43 kg ha-1yr-1 in tile drainage. / FHANTM's simulation of hydrology for one field gave slightly negative coefficients of performance (CP), representing a poor capacity to simulate surface and subsurface runoff depths. The simulation of phosphorus concentrations in surface runoff showed a small range of values compared to field measurements, while simulations of phosphorus concentration in tile drainage were considered acceptable. Therefore, the overall evaluation of the FHANTM 2.0 model indicated that it had difficulty in simulating the transport of phosphorus from an agricultural field in Quebec.

Techn. Univ., Diss.--Braunschweig, 2004.

Thesis (Ph.D.). / Written for the Dept. of Natural Resource Sciences, Macdonald College of McGill University. Title from title page of PDF (viewed 2008/07/24). Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 98-108). Also available on the World Wide Web.