The Legacy of Leaded Gasoline in Bottom Sediment of Small Rural Reservoirs

The historical and ongoing lead (Pb) contamination caused by the 20th-century use of leaded gasoline was investigated by an analysis of bottom sediment in eight small rural reservoirs in eastern Kansas, USA. For the reservoirs that were completed before or during the period of maximum Pb emissions from vehicles (i.e., the 1940s through the early 1980s) and that had a major highway in the basin, increased Pb concentrations reflected the pattern of historical leaded gasoline use. For at least some of these reservoirs, residual Pb is still being delivered from the basins. There was no evidence of increased Pb deposition for the reservoirs completed after the period of peak Pb emissions and (or) located in relatively remote areas with little or no highway traffic. Results indicated that several factors affected the magnitude and variability of Pb concentrations in reservoir sediment including traffic volume, reservoir age, and basin size. The increased Pb concentrations at four reservoirs exceeded the U.S. Environmental Protection Agency threshold-effects level (30.2 mg kg-1) and frequently exceeded a consensus-based threshold-effects concentration (35.8 mg kg-1) for possible adverse biological effects. For two reservoirs it was estimated that it will take at least 20 to 70 yr for Pb in the newly deposited sediment to return to baseline (pre-1920s) concentrations (30 mg kg-1) following the phase out of leaded gasoline. The buried sediment with elevated Pb concentrations may pose a future environmental concern if the reservoirs are dredged, the dams are removed, or the dams fail

100 Native Forage Grasses in 11 Southern States

no. 389 (1971

Crop coefficients of Jatropha

Jatropha and Pongamia are a potential source of biodiesel and grow in a wide range of agroclimatic zones and soil conditions. Data and knowledge available on water requirement of Jatropha and Pongamia are very scarce. Crop coefficients are important parameters used for assessing water requirement and irrigation scheduling. In the present study, crop coefficients of Jatropha and Pongamia were estimated using water balance approach. Temporal data on soil moisture at different depths in block plantations of Jatropha and Pongamia at International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) farm, Patancheru in India, were collected at 15 days interval between 2007 and 2010. Measured soil moisture data were analyzed using one-dimensional water balance model. Results showed that annual water requirement of Jatropha is 750 mm and of Pongamia is about 950 mm in semi-arid tropics. Crop coefficients of Jatropha ranged from 0.10 to 0.95 and of Pongamia from 0.30 to 1.10 depending on plant growth stage in different months. ICRISAT received 820 mm of rainfall in a normal year (data between 2001 and 2010) during the monsoon, of which 52% (430 mm) contributed to evapotranspiration (ET), 34% (280 mm) was stored in soil, and 14% (110 mm) was lost through surface runoff. Stored soil moisture during monsoon season was subsequently utilized by the Jatropha and 270 mm converted into ET during nonmonsoonal period. Pongamia utilized stored soil moisture more effectively than Jatropha as it could remove water from deeper soil layers even at high levels of soil moisture suction

Morphology and Biomass Production of Prairie Cordgrasson Marginal Lands

Prairie cordgrass (Spartina pectinata Link.) is indigenous throughout most of the continental United States and Canada to 60°N latitude and is well suited to marginal land too wet for maize (Zea mays L.) and switchgrass (Panicum virgatum L.). Evaluations of prairie cordgrass in Europe and North America indicated it has high potential for biomass production, relative to switchgrass, in short‐season areas. Our objective was to describe morphology and biomass production and partitioning in mature stands of ‘Red River’ prairie cordgrass and determine biomass production of natural populations on marginal land. This study was conducted from 2000 to 2008 in eastern South Dakota. Mean biomass production of mature stands of Red River was 12.7 Mg ha−1. Leaves composed \u3e88% of the biomass, and 60% of the tillers had no internodes. Belowground biomass to a depth of approximately 25 cm, not including roots, was 21 Mg ha−1. Tiller density ranged from 683 tillers m−2 for a 10‐year‐old stand to 1140 tillers m−2 for a 4‐year‐old stand. The proaxis was composed of about eight phytomers, with rhizomes originating at proximal nodes and erect tillers at distal nodes. Vegetative propagation was achieved by both phalanx and guerilla growth. Differences among natural populations for biomass were expressed on gravelly marginal land. However, production, averaged across populations, was low (1.37 Mg ha−1) and comparable to ‘Cave‐In‐Rock’ switchgrass (1.67 Mg ha−1) over a 4‐year period. The large carbon storage capacity of prairie cordgrass in proaxes and rhizomes makes it useful for carbon sequestration purposes. Prairie cordgrass should be compared with switchgrass and other C4 perennial grasses along environmental gradients to determine optimum landscape positions for each and to maximize bioenergy production and minimize inputs

Water needs and productivity of Jatropha curcas in India: myths and facts

Jatropha curcas referred as a ‘wonder plant’ with low water requirement, which can be cultivated on wastelands in dry tropical conditions to provide oil seeds for biodiesel without competing for prime cropland. However, results from experiments and case studies in semi-arid tropical locations in India indicated that evapotranspiration (ET) demand for Jatropha ranges between 750 and 1000 mm under optimal conditions. Jatropha extracted water from soil layer 150 cm below with transpiration requirements of 600–800 mm with increasing age. The yield potential of current genotypes is low (2–3 ton/ha) for realizing the potential of Jatropha cultivation on wastelands subject to limited availability of nutrients and water. Jatropha curcas is drought tolerant, but contrary to belief, it is not a crop that requires less water: in fact, it requires 750–1000 mm water to achieve economic production. However, Jatropha curcas demonstrated good potential for enhancing green water use efficiency without adversely affecting the blue water component, and for promoting crop management options facilitating carbon sequestration and nutrient recycling when grown on degraded lands. Improved cultivars of Jatropha curcas with synchronized flowering to enable mechanical harvesting, along with improved land and water management, are needed for harnessing the potential of Jatropha as a commercially viable biofuel crop

Measured and Predicted Solute Transport in a Tile Drained Field

Most solute transport measurement techniques are tedious and require extensive soil excavation. A field experiment was conducted to evaluate whether surface transport properties determined by a nondestructive time domain reflectometry (TDR) technique could be used to accurately predict tile flux concentrations. A 14 by 14 m field plot selected above a 1.1-m deep tile drain was studied. Low electrical conductivity (EC) water was sprinkled on the plot surface, and after reaching a steady-state condition, a pulse of calcium chloride solution (16.3 cm) with an EC of 23 dS m−1 was applied through the same sprinklers. Time domain reflectometry equipment was used to record the change in EC of surface (∼ top 2 cm) soil at 45 locations. The EC of the tile drainage flow was measured continuously with an EC probe. The surface convective lognormal transfer (CLT) function parameters, log mean irrigation depth, μI, and its standard deviation, σI, were found to be 3.44 and 0.94 [ln(cm)], respectively, for a reference depth of 110 cm. These surface parameters were used in a one-dimensional (1-D) CLT model and in a two-dimensional (2-D) model (CLT vertical function combined with exponential horizontal transfer function) to predict the tile flux concentrations. The 1-D CLT model predicted an earlier arrival time of chemicals to the tile drain than observed values. The root mean square error, RMSE, of the 1-D CLT predictions was 0.123, and the coefficient of efficiency, E, was −0.47. The 2-D model predictions of tile flux concentrations were similar to the observed values. The root mean squared errors (RMSE) and E were 0.023 and 0.94, respectively. The findings suggest that in this field soil, the surface solute transport properties determined by TDR could be combined with a 2-D transport model to make reasonable predictions of tile flux concentrations