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Abstract
The purpose of this project was to determine key environmental
and economic relationships between agricultural practices and wetlands
in the Prairie Pothole Region (PPR) of eastern South Dakota. Water
quality and water quantity variables were the key environmental
parameters examined. Economic cost and returns by farm management
system and wetland proximity were the key economic parameters.
The three farm management systems examined were conventional
{CON), transitional no-till (TNT), and organic (ORG) • 'lhe 'lNr an::i a:N
management systems used synthetic fertilizers and chemical pesticides.
The ORG system used no synthetic fertilizers and generally no chemical
pesticides. The ORG system had greater emphasis on alfalfa and lower
emphasis on corn and soybean production.
Water budgets were determined for upland and wetland sites. At
the wetland site, runon was the major input to the water budget (60%).
overflow accounted for 36% of the wetland output and surface storage
/seepage accounted for 40%. Evapotranspiration at the wetland site
was much lower than at the upland site.
Nitrate concentrations were consistently higher in the
semipermanent wetland areas than the seasonal wetland areas. The data
show a steady decrease in phosphate concentration as we move upland
in the landscape. Higher concentrations in wetland than upland
groundwater may indicate that some soluble P is moving through the
system and/or the sorption capacity of wetland soils is exceeded.
. Economic returns and costs of the three farming systems were
estimated for 1992 - 1994 at the whole-farm and crop field level. The
relative ranking of net returns by management systems were: TNT > CON
> ORG, unless organic premiums are a major source of gross income.
Production costs per acre by management system from lowest to
highest were ORG < TNT < CON. The organic (ORG) system had lower
reported average yields and considerably lower production costs per
acre than the other management systems. The TNT system had the least
diversity of crop rotations, intermediate-level production costs, and
similar yields or higher yields than reported in the CON system. The
added costs of more tillage and machinery operations in the CON system
exceeded any reduction in chemical costs compared to the TNT system.
Biomass production and most corn/soybean yields were lowest
adjacent to wetland sites and increase to peak production at 150' to
300' feet out. Several years of crop budget estimates for ORG, CON,
and TNT fields adjacent to monitored wetland sites indicated
substandard net returns in most years.