Warm-season perennial grasses are a promising source of biomass for energy production in Southeast USA, and low-input production is desirable. With only residual fertility in the soil and no irrigation, this test compared biomass yields of eight grasses under low-input production: L 79-1002 energycane (Saccharum hyb.), Merkeron and N51 napiergrass (Pennisetum purpureum Schum.), three clones of giant reed (Arundo donax L.), and two switchgrass (Panicum virgatum L.) lines. For the first 2 years napiergrass maintained dry matter (DM) yields over 25 Mg DM ha, and energycane yielded over 20 Mg DM ha average of 4 years), but the biomass contained less moisture at harvest than the other, larger-stemmed grasses. Switchgrass biomass also had the lowest concentrations of N, K, and ash. Average yields of giant reeds were also low (6.4 Mg DM ha), while ash and N concentrations were relatively high compared with switchgrass and energycane. In 4 years of production, energycane and napiergrass removed between 269 and 386 kg N ha −1 and 830-1,159 kg K ha −1

The U.S. Department of Agriculture Agricultural Research Service Southeast Watershed Research Laboratory (SEWRL) initiated a hydrologic research program on the Little River Experimental Watershed in south‐central Georgia, United States, in 1967. The primary intent of the program was to develop an improved understanding of basic hydrologic and water quality processes on Coastal Plain watersheds and to evaluate the effects of agricultural management practices on the region's natural resources and environment. Long‐term (up to 37 years), research‐quality streamflow data have been collected for up to eight flow measurement sites within the Gulf‐Atlantic Coastal Plain physiographic region, an important agricultural production area in the southeastern United States. Forty‐six precipitation gauges and three climate stations are currently in operation to collect data in support of the hydrologic network. Over the past 20 years, sediment and agrichemical concentrations in streamflow have also been monitored to permit evaluation of the impacts of agriculture on regional surface and groundwater quality. Along with the hydrologic and water quality data, geographic spatial data layers for terrain, soils, geology, vegetation, and land management have also been developed. These databases, described in five accompanying data reports, can be accessed via an ftp site supported by the SEWRL (ftp://www.tiftonars.org/).

No abstract

Groundwater nitrate moving from upland areas toward streams can be removed by denitrification in mature riparian forests, but denitrification in restored riparian forests has not been quantified. We determined denitrification rates in a restored riparian wetland below a liquid manure application site. A riparian forest buffer consisting of hardwoods along the stream and pines above the hardwoods was established according to USDA specifications. Denitrification was measured monthly using the acetylene inhibition technique on intact soil cores for 2 mo before manure application began and for 24 mo after manure application. Groundwater movement of NO3−‐N and total Kjeldahl N were estimated biweekly. Average annual denitrification rate was 68 kg N2O‐N ha−1 yr−1. Denitrification was significantly higher in a grassed area than in either of the forested areas. Denitrification did not differ significantly between the hardwood and pine areas. Denitrification was greater than a conservative estimate of groundwater input of total N. Denitrification rates were higher in April and May 1992 and 1993, after manure application to the upland began, compared with April and May 1991, before manure application began. These results indicate that a riparian wetland, which has not undergone hydrologic modifications, can have denitrification rates comparable to mature riparian forests. Higher denitrification rates in an adjacent grassed wetland and lack of differences in denitrification in hardwood and pine zones indicates that the high denitrification rates were due to factors other than the reforestation itself. Compared with groundwater inputs of N, denitrification was an important sink for N moving from the upland management system.