Perennial Filter Strips Reduce Nitrate Levels in Soil and Shallow Groundwater after Grassland-to-Cropland Conversion

Many croplands planted to perennial grasses under the Conservation Reserve Program are being returned to crop production, and with potential consequences for water quality. The objective of this study was to quantify the impact of grassland-to-cropland conversion on nitrate-nitrogen (NO3–N) concentrations in soil and shallow groundwater and to assess the potential for perennial filter strips (PFS) to mitigate increases in NO3–N levels. The study, conducted at the Neal Smith National Wildlife Refuge (NSNWR) in central Iowa, consisted of a balanced incomplete block design with 12 watersheds and four watershed-scale treatments having different proportions and topographic positions of PFS planted in native prairie grasses: 100% rowcrop, 10% PFS (toeslope position), 10% PFS (distributed on toe and as contour strips), and 20% PFS (distributed on toe and as contour strips). All treatments were established in fall 2006 on watersheds that were under bromegrass (Bromus L.) cover for at least 10 yr. Nonperennial areas were maintained under a no-till 2-yr corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotation since spring 2007. Suction lysimeter and shallow groundwater wells located at upslope and toeslope positions were sampled monthly during the growing season to determine NO3–N concentration from 2005 to 2008. The results indicated significant increases in NO3–N concentration in soil and groundwater following grassland-to-cropland conversion. Nitrate-nitrogen levels in the vadose zone and groundwater under PFS were lower compared with 100% cropland, with the most significant differences occurring at the toeslope position. During the years following conversion, PFS mitigated increases in subsurface nitrate, but long-term monitoring is needed to observe and understand the full response to land-use conversion

Tombigbee River Basin, Alabama and Mississippi, Water and Related Land Resources

Excerpts from the report: The Tombigbee River Basin is part of a sub-region of the South Atlantic-Gulf Region. The basin is located in Western Alabama and Northeastern Mississippi. It comprises all or part of 16 counties in Alabama and 19 counties in Mississippi. The boundary encompasses 8.8 million acres of land and water, with 4.9 million acres in Alabama and 3.9 million acres in Mississippi. It is approximately 85 miles wide and 260 miles long. The basin consists of the drainage area of the Tombigbee River above the confluence with the Alabama River, except for the drainage area of the Black Warrior River that flows into the Tombigbee River near Demopolis, Alabama. The eastern boundary is the divide of the Alabama and Black Warrior Rivers. The Tennessee and Hatchie River Systems make up the northern boundary. The western boundary consists of the divides of the Tallahatchie, Yalobusha, Big Black, Pearl, Chickasawhay, and Escatawpa Rivers. The purpose of the study was to formulate alternative plans and suggest an alternative for use in facilitating the coordinated and orderly conservation, development, utilization, and management of the water and related land resources of the basin. Achievement of this purpose required an assessment of the water and related land resource problems, needs, and development potentials of the basin

Little Blue River Basin, Nebraska, Water and Related Land Resources

Excerpts from the report: The Little Blue River is a tributary of the Big Blue River. It originates in the loess plains of south central Nebraska and flows in a south easterly direction to its junction with the Big Blue River near Waterville, Kansas. The area of the Little Blue River Basin in Nebraska totals just under 2,691 square miles, or 1,722,200 acres. Principal tributaries include Big Sandy Creek, having a drainage area of 638 square miles; Rose Creek, 203 square miles; Spring Creek, 180 square miles; and Pawnee Creek, 126 square miles. The total length of the Little Blue River in Nebraska is approximately 200 miles. The Little Blue River drains nearly all of Thayer County and parts of 10 other counties in Nebraska. The report is based upon a study of upstream watershed needs and opportunities for flood prevention; agricultural, municipal, and industrial water supply; fish and wildlife habitat; recreation facilities; and water quality control. The main objectives of the USDA study are to: (1) inventory the natural resources of the basin; (2) analyze the basin's economy relative to present conditions, historic trends, and projections; (3) determine the cause, extent, and frequency of the basin's resource problems; (4) determine the present and future need for development based on resource problems and projected economic activity; (5) describe the pertinent existing water and related land resource projects and programs; (6) describe the physical potential or capability of the basin to supply water and related land resources for development to meet identifiable needs; and (7) describe the opportunities for development through USDA projects and programs and determine their impacts upon the basin

Grassland Retention in the North America Midwest After Periods of High Commodity Prices and Climate Variability

The conversion of grassland, wetlands, and forest to croplands may contribute environmental degradation and diminished sustainability. This study determined the impact of land use change from 2006 to 2012 and from 2012 to 2014 on the cultivation suitability of grasslands that were not converted to cropland. The model system, which includes Nebraska and South Dakota, was selected because it contains climatic conditions ranging from humid continental to semiarid and a large number of farms that produced both crops and livestock. During the study, commodity prices reached historically high values, and a severe drought occurred in 2012. Land use benchmarks were obtained by visually identifying land use at 81,600 sample sites in high-resolution remote sensing images obtained from the National Agricultural Imaging Program. Sampling sites with Land Capability Class values ≤4 were identified as suitable for cultivation if appropriate practices were followed. In 2006, 2012, and 2014, grasslands accounted for 11.0, 10.76, and 10.78 million ha in Nebraska, respectively, whereas in South Dakota, grasslands accounted for 12.12, 11.65, and 11.69 million ha, respectively. In Nebraska, the percentage of grasslands relative to working lands (grassland + croplands) decreased from 60.6% in 2006 to 58.9% in 2014, whereas in South Dakota the percentage of grassland decreased from 69.1% in 2006 to 66.0% in 2014. In eastern Nebraska and South Dakota, 74.1% of the nonconverted grasslands in 2012 were suitable for crop production. Lower-than-expected conversion rates were attributed to a growing interest in land stewardship and a desire to maintain income diversification