Publications (13)3.24 Total impact
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Article: Carbon dioxide flux as affected by tillage and irrigation in soil converted from perennial forages to annual crops.
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ABSTRACT: Among greenhouse gases, carbon dioxide (CO(2)) is one of the most significant contributors to regional and global warming as well as climatic change. A field study was conducted to (i) determine the effect of soil characteristics resulting from changes in soil management practices on CO(2) flux from the soil surface to the atmosphere in transitional land from perennial forages to annual crops, and (ii) develop empirical relationships that predict CO(2) flux from soil temperature and soil water content. The CO(2) flux, soil temperature (T(s)), volumetric soil water content (theta(v)) were measured every 1-2 weeks in no-till (NT) and conventional till (CT) malt barley and undisturbed soil grass-alfalfa (UGA) systems in a Lihen sandy loam soil (sandy, mixed, frigid Entic Haplustoll) under irrigated and non-irrigated conditions in western North Dakota. Soil air-filled porosity (epsilon) was calculated from total soil porosity and theta(v) measurements. Significant differences in CO(2) fluxes between land management practices (irrigation and tillage) were observed on some measurement dates. Higher CO(2) fluxes were detected in CT plots than in NT and UGA treatments immediately after rainfall or irrigation. Soil CO(2) fluxes increased with increasing soil moisture (R(2)=0.15, P<0.01) while an exponential relationship was found between CO(2) emission and T(s) (R(2)=0.59). Using a stepwise regression analysis procedure, a significant multiple regression equation was developed between CO(2) flux and theta(v), T(s) (CO(2) flux = e(-3.477+0.123T(s)+6.381theta)(v); R(2)=0.68, P <or= 0.01). Not surprisingly, soil temperature was a driving factor in the equation, which accounted for approximately 59% in variation of CO(2) flux. It was concluded that less intensive tillage, such as no-till or strip tillage, along with careful irrigation management will reduce soil CO(2) evolution from land being converted from perennial forages to annual crops.Journal of Environmental Management 09/2008; 88(4):1478-84. · 3.24 Impact Factor -
Conference Proceeding: Soil Carbon Dioxide Emission as Influenced by Irrigation, Tillage, Cropping System, and Nitrogen Fertilization
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ABSTRACT: Soil and crop management practices can influence CO 2 emission from crop and grasslands and therefore on global warming. We examined the effects of two irrigation systems (irrigated vs. non-irrigated) and six management practices [no-till malt barley (Hordeum vulgaris L.) with 67 or 134 kg N ha -1 (NTBFN), no-till malt-barley with 0 kg N ha -1 (NTBON), conventional-till malt barley with 67 or 134 kg N ha -1 (CTBFN), conventional-till malt barley with 0 kg N ha -1 (CTBON), no-till pea (Pisum sativum L.) with 0 kg N ha -1 (NTPON), and undisturbed alfalfa (Medicago sativa L.) and grasses with 0 kg N ha -1 (UAGON)] on soil surface CO 2 flux and soil temperature and water content at the 0 to 15 cm depth. Weekly CO 2 flux, soil temperature, and soil water content were monitored during the crop growing season from May to November 2005 in Lihen sandy loam (sandy, mixed, frigid, Entic Haplustolls) in western North Dakota. Irrigation increased CO 2 flux by 27% compared with non-irrigation by increasing soil water content during dry periods. Similarly, tillage increased CO 2 flux by 58% compared with non-tillage by increasing soil temperature. The CO 2 flux was 1.5 to 2.5-fold greater in tilled than in non-tilled treatments following heavy rain or irrigation. Nitrogen fertilization increased CO 2 flux compared with no N fertilization in 2 out of 17 measurements while cropping system did not influence CO 2 flux. The CO 2 flux in undisturbed alfalfa and grasses was similar to that in no-tilled crops. The CO 2 flux was linearly related with soil temperature and daily average air temperature at the time of CO 2 measurement. Tillage followed by heavy rain or irrigation during the crop growing season drastically increased CO 2 flux in the coarse-textured soil previously managed under Conservation Reserve Program (CRP) planting for more than 20 yr.Workshop on Agricultural Air Quality: State of Science. June 5-8, 2006, Potomac, Maryland, USA; 06/2006 -
Article: Passive Capillary Sampler for Measuring Soil Water Drainage and Flux in the Vadose Zone: Design, Performance, and Enhancement
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ABSTRACT: Various soil water samplers are used to monitor, measure, and estimate drainage water, fluxes, and solute transport in the vadose zone. Passive capillary samplers (PCAPs) have shown potential to provide better measurements and estimates of soil water drainage and fluxes than other lysimeters designs and field sampling methods. Twelve automated PCAPs with sampling surface dimensions of 31 cm width × 91 cm long and 87 cm in height were designed, constructed, and tops of the samplers were placed 90 cm below the soil surface in a Lihen sandy loam (sandy, mixed, frigid Entic Haplustoll). The PCAPs were installed to continually quantify the amount of drainage water and fluxes occurring under sugarbeet (Beta vulgaris L.) and malting barley (Hordeum vulgare L.) crops treated with 30 mm (low replacement) and 15 mm (high replacement) irrigation frequencies. Drainage water was extracted, collected, and measured periodically (weekly from May to mid‐August, biweekly until late September, and monthly thereafter until mid‐November). This design incorporated Bluetooth wireless technology to enable an automated datalogger to transmit drainage water and flux data simultaneously every 15 min to a remote host. Real‐time seamless monitoring and measuring of drainage water and fluxes was thus possible without the need for costly time‐consuming supportive operations. The mean difference (M d) values between manually extracted and logged drainage water for high frequency (M d = 0.80 mm) and low frequency (M d = 0.26 mm) irrigations were small and not significantly different from zero. The Root Mean Square Error (RMSE) of 2.46 and 7.83 mm for high frequency and low frequency irrigations, respectively, were also small. Despite small variations in drainage water results, our novel PCAP design provided an accurate and convenient way to measure water drainage and flux in the vadose zone. Moreover, it offered a significantly larger coverage area (2700 cm 2) than similarly designed vadose zone fluxmeters or PCAPs. In the course of one year's field testing, we incorporated several additional enhancements such as PCAP container, tipping bucket and datalogger unit, all of which we recommend for optimal performance. Keywords. Lysimeter, Tipping bucket, Fluxmeter, TDR sensor. he vadose zone, also termed the unsaturated zone, is an important layer of the soil profile between the surface and the saturation zone or permanent water table (Warrick, 2003). Chemical transport and loss with drainage water through the vadose zone and into the groundwater poses a critical problem for public health and environmental quality as well as cost‐effective agriculture. Successful monitoring of pollutant transport and leaching through the soil requires accurate and appropriate methods to capture, sample, and measure drainage water and estimate water fluxes within the vadose zone. The most common and currently available field methods for drainage water and flux Submitted for review in August 2007 as manuscript number SW 7136; approved for publication by the Soil & Water Division of ASABE in April 2008. Mention of trade names, proprietary products, or specific equipment is intended for reader information only and does not constitute a guarantee or warranty by the USDA‐ARS; nor does it imply approval of the product named to the exclusion of other products. -
Article: Carbon dioxide flux as affected by tillage and irrigation in soil converted from perennial forages to annual crops
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ABSTRACT: Among greenhouse gases, carbon dioxide (CO2) is one of the most significant contributors to regional and global warming as well as climatic change. A field study was conducted to (i) determine the effect of soil characteristics resulting from changes in soil management practices on CO2 flux from the soil surface to the atmosphere in transitional land from perennial forages to annual crops, and (ii) develop empirical relationships that predict CO2 flux from soil temperature and soil water content. The CO2 flux, soil temperature (Ts), volumetric soil water content (θv) were measured every 1–2 weeks in no-till (NT) and conventional till (CT) malt barley and undisturbed soil grass-alfalfa (UGA) systems in a Lihen sandy loam soil (sandy, mixed, frigid Entic Haplustoll) under irrigated and non-irrigated conditions in western North Dakota. Soil air-filled porosity (ε) was calculated from total soil porosity and θv measurements. Significant differences in CO2 fluxes between land management practices (irrigation and tillage) were observed on some measurement dates. Higher CO2 fluxes were detected in CT plots than in NT and UGA treatments immediately after rainfall or irrigation. Soil CO2 fluxes increased with increasing soil moisture (R2=0.15, P<0.01) while an exponential relationship was found between CO2 emission and Ts (R2=0.59). Using a stepwise regression analysis procedure, a significant multiple regression equation was developed between CO2 flux and θv, Ts (CO2flux=e-3.477+0.123Ts+6.381θv; R2=0.68, P⩽0.01). Not surprisingly, soil temperature was a driving factor in the equation, which accounted for approximately 59% in variation of CO2 flux. It was concluded that less intensive tillage, such as no-till or strip tillage, along with careful irrigation management will reduce soil CO2 evolution from land being converted from perennial forages to annual crops.Journal of Environmental Management. -
Article: Characterization of spatial variability of soil electrical conductivity and cone index using coulter and penetrometer-type sensors.
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Article: Passive Capillary Sampler for Measuring Soil Water Drainage and Flux in the Vadose Zone: Design, Performance, and Enhancement.
[show abstract] [hide abstract]
ABSTRACT: Various soil water samplers are used to monitor, measure, and estimate drainage water, fluxes, and solute transport in the vadose zone. Passive capillary samplers (PCAPs) have shown potential to provide better measurements and estimates of soil water drainage and fluxes than other lysimeters designs and field sampling methods. Twelve automated PCAPs with sampling surface dimensions of 31 cm width x 91 cm long and 87 cm in height were designed, constructed, and tops of the samplers were placed 90 cm below the soil surface in a Lihen sandy loam (sandy, mixed, frigid Entic Haplustoll). The PCAPs were installed to continually quantify the amount of drainage water and fluxes occurring under sugarbeet ( Beta vulgaris L.) and malting barley ( Hordeum vulgare L.) crops treated with 30 mm (low replacement) and 15 mm (high replacement) irrigation frequencies. Drainage water was extracted, collected, and measured periodically (weekly from May to mid-August, biweekly until late September, and monthly thereafter until mid-November). This design incorporated Bluetooth wireless technology to enable an automated datalogger to transmit drainage water and flux data simultaneously every 15 min to a remote host. Real-time seamless monitoring and measuring of drainage water and fluxes was thus possible without the need for costly time-consuming supportive operations. The mean difference (M(d)) values between manually extracted and logged drainage water for high frequency (M(d) = 0.80 mm) and low frequency (M(d) = 0.26 mm) irrigations were small and not significantly different from zero. The Root Mean Square Error (RMSE) of 2.46 and 7.83 mm for high frequency and low frequency irrigations, respectively, were also small. Despite small variations in drainage water results, our novel PCAP design provided an accurate and convenient way to measure water drainage and flux in the vadose zone. Moreover, it offered a significantly larger coverage area (2700 cm 2 ) than similarly designed vadose zone fluxmeters or PCAPs. In the course of one year's field testing, we incorporated several additional enhancements such as PCAP container, tipping bucket and datalogger unit, all of which we recommend for optimal performance. -
Article: Development of Strip Tillage on Sprinkler Irrigated Sugarbeet.
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ABSTRACT: A project to evaluate new technologies for strip tillage of small seeded crops was initiated in fall 2003 near Sidney, Montana, for sprinkler irrigated sugarbeet ( Beta vulgaris L.) to be grown in 2004. Strip till treatments were compared to conventional grower tillage practices in fifty-six 15- A project to evaluate new technologies for strip tillage of small seeded crops was initiated in fall 2003 near Sidney, Montana, for sprinkler irrigated sugarbeet ( Beta vulgaris L.) to be grown in 2004. Strip till treatments were compared to conventional grower tillage practices in fifty-six 15- x 25-m (48- x 80-ft) side-by-side plots. Both treatments were flat planted with no ridges or beds. All strip tillage and fertilization was done in the fall after removal of a malt barley crop. Conventional tillage was done in the fall at the Sidney site and in the spring at the Nesson site. Thirty-centimeter (12-in.) wide strips were tilled directly into the straw residues about 20 cm (8 in.) deep using straight and paired fluted coulters and a modified parabolic ripping shank followed by a crows-foot packer wheel. Toothed-wheel row cleaners were installed in front of the straight coulter to move loose residue to the side to avoid plugging. At the same time, dry fertilizer was shanked (banded) about 8 to 13 cm (3 to 5 in.) below the anticipated seed placement location. Sugarbeet were planted about 2.5 cm (1 in.) deep with 60-cm (24-in.) spacing between rows in the spring. Toothed-wheel row cleaners were also placed in front of each row on the planter to move any residue displaced by winter storms. Operation of the strip tillage machine required about 25 tractor horsepower per row, but substantial fuel savings were realized with this system by reducing the number of tractor equipment field passes by up to 75%. In 2004, 2006, 2007, and 2008 there were no significant differences in yields or sugar production between the two tillage treatments; however, in 2005 the strip tilled plots produced about 17% greater yields (tonnage and gross sugar). This benefit in 2005 was primarily due to the standing straw stubble in the strip tilled plots that protected sugarbeet seedlings from blowing soil during a spring wind storm that severely damaged seedlings in the conventionally tilled plots where there was no surface crop residue. It was concluded that strip tillage must be considered as part of a larger cropping system that affects timing and equipment choices for planting, cultivation, spraying, and harvesting as well as tillage and other cultural practices. Based on these results, it is generally recommended that strip tillage should be performed in the fall on clay soils in eastern Montana where it has been shown to result in better seedbed conditions than spring strip tillage. Whereas lighter, sandy soils would probably produce equally well when strip tilled in the spring, which could then be combined with planting into a single pass tillage, fertilizing, and planting operation. Banding fertilizer is highly recommended under strip till to increase fertilizer use efficiencies and reduce input costs. RTK-GPS guided steering in combination with some type of mechanical steering assistance on the implements are also recommended for both strip tilling, planting, and cultivation (if needed). Aproximately 25-m (48- aproximately 80-ft) side-by-side plots. Both treatments were flat planted with no ridges or beds. All strip tillage and fertilization was done in the fall after removal of a malt barley crop. Conventional tillage was done in the fall at the Sidney site and in the spring at the Nesson site. Thirty-centimeter (12-in.) wide strips were tilled directly into the straw residues about 20 cm (8 in.) deep using straight and paired fluted coulters and a modified parabolic ripping shank followed by a crows-foot packer wheel. Toothed-wheel row cleaners were installed in front of the straight coulter to move loose residue to the side to avoid plugging. At the same time, dry fertilizer was shanked (banded) about 8 to 13 cm (3 to 5 in.) below the anticipated seed placement location. Sugarbeet were planted about 2.5 cm (1 in.) deep with 60-cm (24-in.) spacing between rows in the spring. Toothed-wheel row cleaners were also placed in front of each row on the planter to move any residue displaced by winter storms. Operation of the strip tillage machine required about 25 tractor horsepower per row, but substantial fuel savings were realized with this system by reducing the number of tractor equipment field passes by up to 75%. In 2004, 2006, 2007, and 2008 there were no significant differences in yields or sugar production between the two tillage treatments; however, in 2005 the strip tilled plots produced about 17% greater yields (tonnage and gross sugar). This benefit in 2005 was primarily due to the standing straw stubble in the strip tilled plots that protected sugarbeet seedlings from blowing soil during a spring wind storm that severely damaged seedlings in the conventionally tilled plots where there was no surface crop residue. It was concluded that strip tillage must be considered as part of a larger cropping system that affects timing and equipment choices for planting, cultivation, spraying, and harvesting as well as tillage and other cultural practices. Based on these results, it is generally recommended that strip tillage should be performed in the fall on clay soils in eastern Montana where it has been shown to result in better seedbed conditions than spring strip tillage. Whereas lighter, sandy soils would probably produce equally well when strip tilled in the spring, which could then be combined with planting into a single pass tillage, fertilizing, and planting operation. Banding fertilizer is highly recommended under strip till to increase fertilizer use efficiencies and reduce input costs. RTK-GPS guided steering in combination with some type of mechanical steering assistance on the implements are also recommended for both strip tilling, planting, and cultivation (if needed). -
Article: Response of eight sugarbeet varieties to increasing nitrogen application. I. Root, sucrose, and top yield.
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ABSTRACT: Nitrogen management affects both the root and top biomass production of sugarbeet (Beta vulgaris L.). An interaction between genetic factors and the amount of N applied may influence variety selection for different N management and cropping systems practices. A three-year field study was conducted with the objective of comparing the relationship between applied N and root, sucrose and top yield for selected commercial sugarbeet varieties. Eight varieties were treated with five amounts of N (0, 90, 179, 269, and 358 kg N ha-1) at a furrow-irrigated site in northwest Wyoming. Variety affected sucrose concentration and sugar loss to molasses (SLM) in all three years, root yield and sucrose yield in one of three years, and top dry matter (TDM) yield and sucrose:TDM ratio in two of three years. All yield parameters were affected by the amount of N applied (N) in all three years. The variety x N interaction was significant for only the sucrose:TDM ratio in two of three years and was most prominent with 0 or 90 kg ha-1 applied N at which two varieties produced higher amounts of sucrose per unit TDM than the other six varieties. Results do not suggest that N fertilizer management should be variety-specific, but the significant interaction in sucrose:TDM ratio indicates that there may be differences in N response among varieties based on how they partition photosynthate between roots and tops, especially at low levels of available. These differences can help determine which varieties are best suited for different management objectives. -
Article: Impact of Fuel and Nitrogen Prices on Profitability of Selected Crops: A Case Study.
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ABSTRACT: Increasing prices for fuel and N fertilizer affect crop production decisions and profitability. Nitrogen response functions are estimated for corn (Zea mays L.), sugar beet (Beta vulgaris L.), dry bean (Phaseolus vulgaris L.), and malt barley (Hordeum vulgare L.) using data from field studies conducted in the Big Horn Basin of Wyoming. These N response functions are used to evaluate the impact of increases in N and fuel prices on the profitable level of N use. Enterprise budgets are developed for seven selected crops to determine return to management [Return to Management = Price x Yield - Total Cost (preplant, plant, growing, harvest, land, and other)] under price increases for fuel and N. Finally, a linear programming model is used to determine the impacts of increased prices for fuel and N on farm profit and crop mix. Results illustrate that impacts of increasing fuel and N prices on individual crops are quite different and also vary with the overall crop mix. In particular, adding alfalfa (Medicago sativa L.) and perennial ryegrass (Lolium spp.) seed production to the crop mix reduced the impacts of increasing fuel and N prices. This suggests producers should adjust production practices on individual crops and also analyze their crop mix when faced with rising fuel and N prices if they are to minimize impacts on profitability. -
Article: Spatial Variability and Correlation of Selected Soil Properties in the Ap Horizon of a CRP Grassland.
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ABSTRACT: Knowledge of the spatial variability of soil properties in agricultural fields is important for implementing various precision agricultural management practices. This article examines spatial variation of selected soil physical and chemical properties and explores their spatial correlation in the Ap horizon of a Lihen sandy loam soil (sandy, mixed, frigid Entic Haplustoll) within a field of grass-alfalfa Conservation Reserve Program (CRP) land. Soil measurements were made on a 16 x 36-m grid sampling pattern. Soil properties including penetration resistance (PR), bulk density (rho b), and gravimetric water content (theta m) were measured by collecting undisturbed soil cores from 5- to 10-cm and 20- to 25-cm depths. Additional disturbed soil samples were collected for particle size distribution, electrical conductivity (EC(e)), and pH analysis. The two depths were averaged for the assessment of spatial distribution, relationships and interpolation of soil properties. Soil saturated hydraulic conductivity (K(s)) and total porosity (epsilon(T)) for the 0- to 25-cm depth were estimated from rho b , theta m , and volumetric water content at field capacity (FC) level. Soil properties were analyzed using both classical and geostatistical methods that included descriptive statistics, semivariograms, cross-semivariograms, spatial kriged and co-kriged prediction maps and interpolation. Results indicated that small to moderate spatial variability existed across the field for soil properties studied . Furthermore, cross-semivariograms exhibited a strong negative spatial interdependence between soil PR and theta m, epsilon(T), and lnK(s). Spatial variability of soil theta(m), rho b, PR, ECe, pH, and clay content and their spatial correlation in the Ap horizon of the CRP grassland were attributed to a combination of previous farming practices, topographic characteristics, vegetation history, soil erosion, and weather conditions at this site. -
Article: Repeatability of soil apparent electrical conductivity measured by a coulter sensor.
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ABSTRACT: Apparent electrical conductivity (ECa) measured using an on-the-go coulter sensor offers advantages for mapping soil variability because detailed data can be collected easily and inexpensively using on-the-go ECa sensors. However, there has been little research investigating the repeatability of these sensors, which may be defined as their ability to reproduce the same ECa measurement when operated in the same location under the same operating and field conditions. If the output of the coulter ECa sensor is not repeatable, the accuracy and reliability of the resulting maps and management decisions would be compromised. Therefore, the objective of this study was to evaluate the repeatability of the coulter sensor by comparing ECa data from two passes in barley stubble at two 1.6-ha sites, one with a sandy loam soil texture (Nesson site) and the other, a clay loam soil texture (Montana State University Eastern Agricultural Research Center site). Sampling points were approximately 1.45 m apart in the direction of travel for both passes. The ECa measurements from both passes were compared at shallow (0-30 cm) and deep (0-90 cm) soil depths. The coefficients of variation of ECa measurements for shallow and deep depths from pass 1 were higher than those from pass 2 at both sites. The root mean square error values of ECa measurements between pass 1 and pass 2 at shallow and deep depths for the Nesson site were 0.76 and 0.51 mS m-1, respectively, whereas the root mean square errors for the Montana State University Eastern Agricultural Research Center site were 4.06 and 2.93 mS m-1 at shallow and deep depths, respectively. The repeatability was evaluated using a 95% confidence interval for the differences between ECa measurements of the two passes. Results demonstrate marginally acceptable repeatability between the two passes at shallow depths and acceptable repeatability at deep depths. The reasons for lack of agreement between pass 1 and pass 2 in ECa measurements at shallow depths could have resulted from soil disturbance and compaction caused by the coulter sensor during the pass 1 process. Regardless of discrepancies for shallow depths, the results indicate that the on-the-go ECa sensors can be useful and provide reliable data for describing field spatial variability in precision farming. This study was conducted to represent field conditions under which this equipment will likely be used, and further work is needed to confirm the repeatability of the coulter at shallow depths. -
Article: Tillage Depth Effects on Soil Physical Properties, Sugarbeet Yield, and Sugarbeet Quality.
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ABSTRACT: Tillage depth influences the soil-water-plant ecosystem, thereby affecting crop yield and quality. The effects of tillage depth on soil physical properties and sugarbeet (Beta vulgaris L.) yield and quality were evaluated. A field study composed of two tillage depths [10 cm, referred to as shallow (ST), and 20 cm, referred to as deep (DT)] was conducted on a Lihen sandy loam soil in spring 2007 at the Agricultural Research Service (ARS) irrigated research farm near Williston, North Dakota. Soil bulk density (ρ(b)), gravimetric water content (theta(w)), and saturated hydraulic conductivity (Ks) were measured three times during the growing season at four depth increments to 40 cm deep. Samples were taken approximately 0.5 m apart within the crop row of irrigated sugarbeet. Soil air-filled pore volume ((epsilon)a) was calculated from soil bulk density and water content data. Soil penetration resistance (PR) was also measured in 2.5-cm increments to a depth of 35 cm. Roots were hand-harvested from each plot, and each sample consisted of the roots within an area consisting of two adjacent rows 1.5 m long. Soil ρ(b) was greater in ST than in DT, whereas Ks was greater with DT than with ST. Soil PR was significantly greater in ST than in DT at the 0- to 20-cm depth. Soil theta(w) and epsilon(a) were slightly greater in DT than those under ST. Although tillage depth had no significant effect on sugarbeet population, root yield, or sucrose content, a small difference in sucrose yield between two depths of tillage may be attributed to reduced ρ(b), increased water intake, improved aeration, and increased response to nitrogen uptake under DT than under ST. It was concluded that tillage depth enhanced soil physical quality and had little effect on sugarbeet yield or quality. -
Article: Soil Carbon Dioxide Emission and Carbon Content as Affected by Irrigation, Tillage, Cropping System, and Nitrogen Fertilization.
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ABSTRACT: Management practices can influence soil CO2 emission and C content in cropland, which can effect global warming. We examined the effects of combinations of irrigation, tillage, cropping systems, and N fertilization on soil CO2 flux, temperature, water, and C content at the 0- to 20-cm depth from May to November 2005 at two sites in the northern Great Plains. Treatments were two irrigation systems (irrigated vs. non-irrigated) and six management practices that contained tilled and no-tilled malt barley (Hordeum vulgaris L.) with 0 to 134 kg N ha-1, no-tilled pea (Pisum sativum L.), and a conservation reserve program (CRP) planting applied in Lihen sandy loam (sandy, mixed, frigid, Entic Haplustolls) in western North Dakota. In eastern Montana, treatments were no-tilled malt barley with 78 kg N ha-1, no-tilled rye (Secale cereale L.), no-tilled Austrian winter pea, no-tilled fallow, and tilled fallow applied in dryland Williams loam (fine-loamy, mixed Typic Argiborolls). Irrigation increased CO2 flux by 13% compared with non-irrigation by increasing soil water content in North Dakota. Tillage increased CO2 flux by 62 to 118% compared with no-tillage at both places. The flux was 1.5- to 2.5-fold greater with tilled than with non-tilled treatments following heavy rain or irrigation in North Dakota and 1.5- to 2.0-fold greater with crops than with fallow following substantial rain in Montana. Nitrogen fertilization increased CO2 flux by 14% compared with no N fertilization in North Dakota and cropping increased the flux by 79% compared with fallow in no-till and 0 kg N ha-1 in Montana. The CO2 flux in undisturbed CRP was similar to that in no-tilled crops. Although soil C content was not altered, management practices influenced CO2 flux within a short period due to changes in soil temperature, water, and nutrient contents. Regardless of irrigation, CO2 flux can be reduced from croplands to a level similar to that in CRP planting using no-tilled crops with or without N fertilization compared with other management practices.
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2008
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United States Department of Agriculture
Fort Collins, CO, USA
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