Invasive exotic cool-season grasses such Kentucky bluegrass (Poa pratensis L.) and smooth bromegr... more Invasive exotic cool-season grasses such Kentucky bluegrass (Poa pratensis L.) and smooth bromegrass (Bromus inermus Leyss.) have reduced native grasses in the northern tallgrass prairie. The objective of this study was to determine the effects of spring burning, intensive clipping, and late season nitrogen application on species foliar cover. Experimental sites were established near Brookings (restored), Miller (native), and Volga (native) in eastern South Dakota. The experimental design was a split-split plot with 4 replications. The whole plot consisted of spring burning or no-burning, the subplot consisted of weekly clipping to 5-10 cm in May, and the sub-subplot consisted of June application of 0 or 15 kg/ha nitrogen. Foliar cover estimates of major plant functional groups were conducted in late-June/early-July and late-August/early-September
Recent research suggests that N recommendations developed using the linear plateau model have a p... more Recent research suggests that N recommendations developed using the linear plateau model have a poor relationship with the economic optimum N rates. These results have been attributed to inaccurate assessment of N mineralization. The objective of this study was to determine the influence of soil moisture regime on yield, N responses, and mineralization because not only do environmental conditions vary from year to year but yield also varies from location to location. Field experiments were conducted in Aurora, South Dakota, 2002, 2003 and 2004. Treatments were natural rainfall, natural rainfall + irrigation, and four N rates (0, 56, 112, 168 kg N/ha). Plant samples were analyzed for 13C discrimination (Δ), 15N, and total N. An interaction between soil moisture regimes and N rates was not observed. Increasing N rates increased corn grain yields and applying supplemental irrigation increased corn grain yield and N mineralization. The optimum N rate was similar in both soil moisture regimes. This work suggests that the linear plateau model is not accurate because it does not account for increased N mineralization effect of soil moisture regimes
Biochars are the byproduct of anaerobic combustion (pyrolysis) of organic materials. Three biocha... more Biochars are the byproduct of anaerobic combustion (pyrolysis) of organic materials. Three biochars (switchgrass, cornstover, and Ponderosa pine woodchip) were created by burning the materials under anaerobic conditions for four hours at maximum temperatures of 850 C (fast pyrolysis). Biochar samples were sorted by size (< 2 mm, 2-4 mm, and > 4 mm) and electrical conductivity (EC) and pH characteristics were determined in 1:5 (w/v) water and 0.01M CaCl. Each biochar type and size was added at 1 and 10% (w/w), to two South Dakota soils, Barnes (loamy) or Maddock (loamy fine sand). Atrazine sorption and changes in soil pH and EC were measured in slurry experiments (1:2 w/v). Biochar pH values were higher than soil pH values; however, the addition of biochar had minimal influence on soil pH. Biochar size affected soil EC values; the smallest sized chars at the 10% addition increased the soil EC. Atrazine sorption from solution increased from about 35% in soil only to almost 99% w...
Recent research suggests that N recommendations developed using the linear plateau model have a p... more Recent research suggests that N recommendations developed using the linear plateau model have a poor relationship between yield and the economic optimum N rates. These results have been attributed to inaccurate assessment of N mineralization. The objective of this study was to determine the influence of soil moisture regime on yield, N responses, and soil N mineralization due to water availability where environmental conditions vary from year to year and from location to location. Field experiments were conducted in Aurora, South Dakota, 2002, 2003 and 2004. Treatments were natural rainfall, natural rainfall + irrigation, and four N rates (0, 56, 112, 168 kg N/ha). Plant samples were analyzed for 13C discrimination (D), 15N, and total N. An interaction between soil moisture regimes and N rates was not observed. Increasing N rates increased corn grain yield and applying supplemental irrigation increased corn grain yields and soil N mineralization. The optimum N rate was similar in both soil moisture regimes. This work suggests that the linear plateau model is not accurate because it does not account for increased N mineralization effect of soil moisture regimes
Can weed distribution maps be developed from remote sensed reflectance data? When are the appropr... more Can weed distribution maps be developed from remote sensed reflectance data? When are the appropriate times to collect these data during the season? What wavebands can be used to distinguish weedy from weed- free areas? This research examined if and when reflectance could be used to distinguish between weed-free and weed-infested (mixed species) areas in soybean and to determine the most useful wavebands to separate crop, weed, and soil reflectance differences. Treatments in the two-year study included no vegetation (bare soil), weed-free soybean, and weed-infested soybean and, in one year, 80% corn residue cover. Reflectance was measured at several sampling times from May through September in 2001 and 2002 using a hand-held multispectral radiometer equipped with band-limited optical interference filters (460 - 1650 nm). Pixel resolution was 0.8-m. Reflectance in the visible spectral range (460 to 700 nm) generally was similar among treatments. In the near-infrared (NIR) range (>...
Nodules may not provide enough N for optimum growth for irrigated and soybean (Glycine max) plant... more Nodules may not provide enough N for optimum growth for irrigated and soybean (Glycine max) plants undergoing extreme water stress. The objective of this study was to develop and test a model that relates soil water, N supply, and N demand to grain protein. The model suggested that three different types of environments exist. In the first environment, water stress reduces N2 fixation more than CO2 fixation (high water stress). These plants may have low yields and relatively low protein concentrations. In the second environment, N2 fixation exceeds or matches soybean N requirement. These plants may have moderately high yields and high protein concentrations (moderate water stress). In the third environment, the plants are actively growing and N2 fixation can not provide enough N to the plant (low water stress). These plants may have high yields and relatively low protein concentrations. Soil water, 13C discrimination ()), yield, total N, and protein information collected from 145 sam...
Grasslands play a key role in providing wildlife habitat and recreation, as well as in range and ... more Grasslands play a key role in providing wildlife habitat and recreation, as well as in range and pasture livestock production systems by producing high quality animal protein for human consumption. Croplands provide high quality grains for human consumption, coarse grains for ethanol production, and along with forages, feed for confined livestock production systems. These livestock systems also produce high quality animal protein for human consumption. Both land use systems play important roles in a wide range of societal issues facing South Dakota including economic productivity and development, water quality and quantity, health of rural communities, urban development, and additional aspects of quality-of-life long associated with the state. The purpose of this study was to estimate land use changes in South Dakota from 2006 to 2012. Estimates of land use changes were calculated based on proportions of visually observed land use using high resolution imagery (< 2-m resolution) ...
Weed distribution maps can be developed from remotely sensed reflectance data if collected at app... more Weed distribution maps can be developed from remotely sensed reflectance data if collected at appropriate times during the growing season. The research objectives were to determine if and when reflectance could be used to distinguish between weed-free and weed-infested (mixed species) areas in soybean and to determine the most useful wavebands to separate crop, weed, and soil reflectance differences. Treatments included no vegetation (bare soil), weed-free soybean, and weed-infested soybean and, in 1 yr, 80% corn residue cover. Reflectance was measured at several sampling times from May through September in 2001 and 2002 using a handheld multispectral radiometer equipped with band-limited optical interference filters (460 to 1,650 nm). The spatial resolution was 0.8 m2. The reflectance in the visible spectral range (460 to 700 nm) generally was similar among treatments. In the near-infrared (NIR) range (> 700 to 1,650 nm), differences among treatments were observed from soybean g...
Invasive exotic cool-season grasses such Kentucky bluegrass (Poa pratensis L.) and smooth bromegr... more Invasive exotic cool-season grasses such Kentucky bluegrass (Poa pratensis L.) and smooth bromegrass (Bromus inermus Leyss.) have reduced native grasses in the northern tallgrass prairie. The objective of this study was to determine the effects of spring burning, intensive clipping, and late season nitrogen application on species foliar cover. Experimental sites were established near Brookings (restored), Miller (native), and Volga (native) in eastern South Dakota. The experimental design was a split-split plot with 4 replications. The whole plot consisted of spring burning or no-burning, the subplot consisted of weekly clipping to 5-10 cm in May, and the sub-subplot consisted of June application of 0 or 15 kg/ha nitrogen. Foliar cover estimates of major plant functional groups were conducted in late-June/early-July and late-August/early-September
Recent research suggests that N recommendations developed using the linear plateau model have a p... more Recent research suggests that N recommendations developed using the linear plateau model have a poor relationship with the economic optimum N rates. These results have been attributed to inaccurate assessment of N mineralization. The objective of this study was to determine the influence of soil moisture regime on yield, N responses, and mineralization because not only do environmental conditions vary from year to year but yield also varies from location to location. Field experiments were conducted in Aurora, South Dakota, 2002, 2003 and 2004. Treatments were natural rainfall, natural rainfall + irrigation, and four N rates (0, 56, 112, 168 kg N/ha). Plant samples were analyzed for 13C discrimination (Δ), 15N, and total N. An interaction between soil moisture regimes and N rates was not observed. Increasing N rates increased corn grain yields and applying supplemental irrigation increased corn grain yield and N mineralization. The optimum N rate was similar in both soil moisture regimes. This work suggests that the linear plateau model is not accurate because it does not account for increased N mineralization effect of soil moisture regimes
Biochars are the byproduct of anaerobic combustion (pyrolysis) of organic materials. Three biocha... more Biochars are the byproduct of anaerobic combustion (pyrolysis) of organic materials. Three biochars (switchgrass, cornstover, and Ponderosa pine woodchip) were created by burning the materials under anaerobic conditions for four hours at maximum temperatures of 850 C (fast pyrolysis). Biochar samples were sorted by size (< 2 mm, 2-4 mm, and > 4 mm) and electrical conductivity (EC) and pH characteristics were determined in 1:5 (w/v) water and 0.01M CaCl. Each biochar type and size was added at 1 and 10% (w/w), to two South Dakota soils, Barnes (loamy) or Maddock (loamy fine sand). Atrazine sorption and changes in soil pH and EC were measured in slurry experiments (1:2 w/v). Biochar pH values were higher than soil pH values; however, the addition of biochar had minimal influence on soil pH. Biochar size affected soil EC values; the smallest sized chars at the 10% addition increased the soil EC. Atrazine sorption from solution increased from about 35% in soil only to almost 99% w...
Recent research suggests that N recommendations developed using the linear plateau model have a p... more Recent research suggests that N recommendations developed using the linear plateau model have a poor relationship between yield and the economic optimum N rates. These results have been attributed to inaccurate assessment of N mineralization. The objective of this study was to determine the influence of soil moisture regime on yield, N responses, and soil N mineralization due to water availability where environmental conditions vary from year to year and from location to location. Field experiments were conducted in Aurora, South Dakota, 2002, 2003 and 2004. Treatments were natural rainfall, natural rainfall + irrigation, and four N rates (0, 56, 112, 168 kg N/ha). Plant samples were analyzed for 13C discrimination (D), 15N, and total N. An interaction between soil moisture regimes and N rates was not observed. Increasing N rates increased corn grain yield and applying supplemental irrigation increased corn grain yields and soil N mineralization. The optimum N rate was similar in both soil moisture regimes. This work suggests that the linear plateau model is not accurate because it does not account for increased N mineralization effect of soil moisture regimes
Can weed distribution maps be developed from remote sensed reflectance data? When are the appropr... more Can weed distribution maps be developed from remote sensed reflectance data? When are the appropriate times to collect these data during the season? What wavebands can be used to distinguish weedy from weed- free areas? This research examined if and when reflectance could be used to distinguish between weed-free and weed-infested (mixed species) areas in soybean and to determine the most useful wavebands to separate crop, weed, and soil reflectance differences. Treatments in the two-year study included no vegetation (bare soil), weed-free soybean, and weed-infested soybean and, in one year, 80% corn residue cover. Reflectance was measured at several sampling times from May through September in 2001 and 2002 using a hand-held multispectral radiometer equipped with band-limited optical interference filters (460 - 1650 nm). Pixel resolution was 0.8-m. Reflectance in the visible spectral range (460 to 700 nm) generally was similar among treatments. In the near-infrared (NIR) range (>...
Nodules may not provide enough N for optimum growth for irrigated and soybean (Glycine max) plant... more Nodules may not provide enough N for optimum growth for irrigated and soybean (Glycine max) plants undergoing extreme water stress. The objective of this study was to develop and test a model that relates soil water, N supply, and N demand to grain protein. The model suggested that three different types of environments exist. In the first environment, water stress reduces N2 fixation more than CO2 fixation (high water stress). These plants may have low yields and relatively low protein concentrations. In the second environment, N2 fixation exceeds or matches soybean N requirement. These plants may have moderately high yields and high protein concentrations (moderate water stress). In the third environment, the plants are actively growing and N2 fixation can not provide enough N to the plant (low water stress). These plants may have high yields and relatively low protein concentrations. Soil water, 13C discrimination ()), yield, total N, and protein information collected from 145 sam...
Grasslands play a key role in providing wildlife habitat and recreation, as well as in range and ... more Grasslands play a key role in providing wildlife habitat and recreation, as well as in range and pasture livestock production systems by producing high quality animal protein for human consumption. Croplands provide high quality grains for human consumption, coarse grains for ethanol production, and along with forages, feed for confined livestock production systems. These livestock systems also produce high quality animal protein for human consumption. Both land use systems play important roles in a wide range of societal issues facing South Dakota including economic productivity and development, water quality and quantity, health of rural communities, urban development, and additional aspects of quality-of-life long associated with the state. The purpose of this study was to estimate land use changes in South Dakota from 2006 to 2012. Estimates of land use changes were calculated based on proportions of visually observed land use using high resolution imagery (< 2-m resolution) ...
Weed distribution maps can be developed from remotely sensed reflectance data if collected at app... more Weed distribution maps can be developed from remotely sensed reflectance data if collected at appropriate times during the growing season. The research objectives were to determine if and when reflectance could be used to distinguish between weed-free and weed-infested (mixed species) areas in soybean and to determine the most useful wavebands to separate crop, weed, and soil reflectance differences. Treatments included no vegetation (bare soil), weed-free soybean, and weed-infested soybean and, in 1 yr, 80% corn residue cover. Reflectance was measured at several sampling times from May through September in 2001 and 2002 using a handheld multispectral radiometer equipped with band-limited optical interference filters (460 to 1,650 nm). The spatial resolution was 0.8 m2. The reflectance in the visible spectral range (460 to 700 nm) generally was similar among treatments. In the near-infrared (NIR) range (> 700 to 1,650 nm), differences among treatments were observed from soybean g...
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