The watershed-scale effects of agricultural conservation practices are not well understood. A baseline calibration and an input parameter sensitivity analysis were conducted for simulation of watershed-scale hydrology in the Little River Experimental Watershed (LREW) in the Coastal Plain near Tifton, Georgia. The Soil and Water Assessment Tool (SWAT) was manually calibrated to simulate the hydrologic budget components measured for the 16.9 km 2 subwatershed K of the LREW from 1995 to 2004. A local sensitivity analysis was performed on 16 input variables. The sum of squares of the differences between observed and simulated annual averages for baseflow, stormflow, evapotranspiration, and deep percolation was 19 mm 2 ; average annual precipitation was 1136 mm. The monthly Nash-Sutcliffe model efficiency (NSE) for total water yield (TWYLD) was 0.79 for the ten-year period. Daily NSE for TWYLD was 0.42. The monthly NSE for three years with above-average rainfall was 0.89, while monthly NSE was 0.59 for seven years with below annual average rainfall, indicating that SWAT's predictive capabilities are less well-suited for drier conditions. Monthly average TWYLD for the high-flow winter to early spring season was underpredicted, while the low-flow late summer to autumn TWYLD was overpredicted. Results were negatively influenced when seasonal tropical storms occurred during a dry year. The most sensitive parameters for TWYLD were curve number for crop land (CN2(crop)), soil available water content (SOL_AWC), and soil evaporation compensation factor (ESCO). The most sensitive parameters for stormflow were CN2(crop), curve number for forested land (CN2(forest)), soil bulk density (SOL_BD), and SOL_AWC. The most sensitive parameters for baseflow were CN2(crop), CN2(forest), ESCO, and SOL_AWC. Identification of the sensitive SWAT parameters in the LREW provides modelers in the Coastal Plain physiographic region with focus for SWAT calibration.

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During an autumn runoff event we sampled 48 streams with predominantly forested watersheds and igneous bedrock in the Oregon Coast Range. The streams had acid neutralizing capacities (ANC) > 90 μeq/L and pH > 6.4. Streamwater Na +, Ca2 +, and Mg2 + concentrations were greater than K + concentrations. Anion concentrations generally followed the order of Cl‐ > NO3‐ > SO42‐. Chloride and Na + concentrations were highest in samples collected in streams near the Pacific Ocean and decreased markedly as distance from the coast increased. Sea salt exerted no discernible influence on stream water acid‐base status during the sampling period. Nitrate concentrations in the study streams were remarkably variable, ranging from below detection to 172 μeq/L. We hypothesize that forest vegetation is the primary control of spatial variability of the NO3‐ concentrations in Oregon Coast Range streams. We believe that symbiotic N fixation by red alder in pure or mixed stands is the primary source of N to forested watersheds in the Oregon Coast Range.

Core Ideas Agricultural lands have varying potential based on climate, topography, and soils. Aligning land use and potential improves sustainable delivery of ecosystem services. Integrated agricultural systems (IAS) are uniquely adapted to variable land types. Socioeconomic barriers to IAS implementation are significant. Considerable research and education is needed to facilitate IAS adoption. Contemporary agricultural land use is dominated by an emphasis on provisioning services by applying energy‐intensive inputs through relatively uniform production systems across variable landscapes. This approach to agricultural land use is not sustainable. Achieving sustainable use of agricultural land should instead focus on the application of innovative management systems that provide multiple ecosystem services on lands with varying inherent qualities. Integrated agricultural systems (IAS) represent an alternative approach to prevailing land use, whereby site‐adapted enterprises are implemented to enhance synergistic resource transfer among enterprises and sustainable delivery of ecosystem services. Sustainable deployment of IAS on agricultural land involves placing the “right enterprise” at the “right intensity” at the “right time” on the “right location,” with the inherent attributes of location providing guidance for management decisions. There is an urgent need to design IAS that enhance delivery of ecosystem services while ensuring land potential thresholds are not exceeded.

The ability of soils from hardwood, clear-cut, and pine forests to incorporate sulfur from added inorganic sulfate into salt-extractable (adsorbed) and nonsalt-extractable forms was investigated. At least 65% of the added sulfate was adsorbed while 8–27% of the sulfate added was recovered only after treatment of salt-extracted samples with acid and base (nonsalt-extractable sulfur). The incorporation of sulfur into this latter fraction was dependent upon incubation time, temperature, and depth and exhibited both spatial as well as seasonal variation in samples taken along a transect of one of the watersheds. Sulfur incorporation into the nonsalt-extractable fraction was inhibited 75–87% by sodium azide, 62–84% by erythromycin, and 41–68% by candicidin suggesting that the process is mediated by bacteria and fungi. Data on factors influencing sulfur incorporation suggest that sulfate was incorporated into organic matter as a covalent linkage and released after rupture of this linkage during acid and base treatment. The observations that 35S incorporation was inhibited 93–99% by unlabelled sulfate and stimulated 21–65% by increased carbon availability are consistent with this suggestion.