Impacts of Agricultural Management Systems on Economic, Environmental, and Wildlife Values of Altered and Unaltered Wetland Areas

Impacts of Agricultural Management Systems on Economic, Environmental, and Wildlife Values of Altered and Unaltered Wetland Areas

Summary

Rationale:
Wetlands are an integral part of agricultural systems in the Prairie Pothole Region (PPR) of
eastern South Dakota. Wetlands impact agriculture by providing hay and forage, trapping
sediment and runoff and storing water for groundwater and soil recharge. Agricultural practices
can influence wetland water quantity and quality, habitat value and species diversity.

Objectives:
1) To research the impact of farm production systems on avian populations, food supplies and
habitat diversity of altered and unaltered wetland and upland areas.
2) To determine the effects of farm production systems on the water quantity and quality of
wetland areas which are hydrologically linked to ground water.
3) To estimate production costs and net returns of major farming systems adapted to the selected
field tracts.
4) To compare selected economic and environmental trade-offs between major farm production
systems.
5) To develop holistic packages of information and an improved network for exchange of
information concerning the effects of management on wetland values.

Methods:
Three farmers who operate farms [conventional (CON), transitional no-till (TNT), and organic
(ORG)] in the Prairie Pothole Region (PPR) agreed to participate in the study.

Results (listed individually, by objective):
1) Differences were found in waterfowl pair abundances, however most resulted from wetland
habitat conditions on the three farming systems. In general, breeding waterfowl pair abundance
was higher in seasonal and semipermanent wetlands on the CON farming system, probably
resulting from more wetlands with "semi-marsh" conditions. On the other hand, pair abundance
was generally higher in temporary wetlands in the ORG and TNT farming systems. Species
richness was typically highest in the ORG system for both waterfowl pairs and non-waterfowl
breeding birds.

2) Water budgets were determined for upland and wetland sites. At the upland site precipitation
was 85 percent of the input with soil water supplying 15 percent of the output. The major output
was evapotranspiration (72 percent). At the wetland site, run-on was the major input to the water
budget (60 percent). Overflow accounted for 36 percent of the wetland output and surface
storage/seepage accounted for 40 percent. Evapotranspiration at the wetland site was much lower
than at the upland site.

3) Nitrate concentrations were consistently higher in the semipermanent wetland areas than the
seasonal wetland areas, and therefore are not as efficient as seasonal wetlands in removing
nitrates. Orthophosphate concentrations were not significantly different due to wetland
classification in 1993, but were higher in seasonal than semipermanent wetland areas in 1994.
The data show a steady decrease in phosphate concentration moving upward in the landscape.
Higher concentrations in wetland than upland groundwater may indicate that some soluble P is
moving through the system and/or that the sorption capacity of the wetland soils has been
exceeded.

4) Economic returns and costs of the three farming systems are estimated for 1992 - 1994 at the
whole-farm and crop-field level. The relative ranking of net returns by management systems are:
TNT > CON > ORG, unless organic premiums for corn and soybeans are a major component of
gross farm income. Production costs per acre by management system from lowest to highest are
ORG < TNT < CON. Net returns per acre were lower in the organic system compared to the
conventional and transitional no-till system, especially in fields with relatively large proportion
of wetland acres. Additional years of field level information are needed to determine if this
finding is consistent. Also, the relative importance of different cultural practices, type and extent
of wetland, and other factors influencing producer net returns for fields in groundwater/wetland
areas needs to be established with multi-year data.

5) Liaison work with the Soil Conservation Service has resulted in cooperative efforts to
complete topographic surveys and plant inventories. Additional support has aided cooperative
work with the South Dakota Geological Survey and the South Dakota Department of
Environment and Natural Resources to help establish deep monitoring wells in the Big Sioux
Aquifer (which underlies parts of the study site). The progress report included in this proposal
has been supplied to an NCR Sustainable Agriculture committee and the state water quality
extension specialist. Interest in the project is already increasing. Funding is being sought from
state sources to monitor the effectiveness of establishing prairie grass buffer strips around
wetlands to prevent non-point source pollution from agriculture. Efforts are also being
coordinated with a project using Geographical Information Systems to pinpoint wetlands
enrolled in the Conservation Reserve Program. Management systems which will minimize risk to
the wetlands are being proposed so that options are available upon contract expiration. The
continuation of this project will allow for the development of wetland management systems
based on the complex interactions of wildlife, water, agriculture and economics.