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  • 1
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    Measured and Simulated Carbon Dynamics in Midwestern U.S. Corn‐Soybean Rotations (2021)
    Details
    Publication Date: 2021-07-05
    Description: Corn (Zea mays L.) and soybean (Glycine max [L.] Merr.) production dominate Midwestern U.S. agriculture and impact the regional carbon and nitrogen cycles. Sustaining soil carbon is important for corn‐soybean production (CS); however, quantifying soil carbon changes requires long‐term field measurements and/or model simulations. In this study, changes in soil organic (SOC), inorganic (SIC), and total (TC) carbon; pH; total nitrogen (TN); and net ecosystem production (NEP) were measured in a conventional corn‐soybean rotation in central Iowa. Soil samples (n = 42; 0–120 cm depth) were collected from two adjacent fields in 2005 and 2016. Eddy‐flux stations set up in the fields continuously monitored NEP from 2005–2016, and net biome production (NBP) was calculated using yield records. The DayCENT model was used to simulate the effects of conventional management practices on soil carbon and calibrated with field‐measured NEP and SOC. Measured soil TC (0–120 cm) decreased by −14.19 ± 6.25 Mg ha−1, with highest reductions in SOC and SIC (p 〈 0.05) at 0–15 and 90–120 cm, respectively. Measured TN decreased by −0.7 ± 0.29 Mg ha−1 with N‐accumulation at 60–90 cm (p 〈 0.05). Eddy‐flux NBP decreased by −13.19 ± 0.05 Mg ha−1. Soil and eddy‐flux records show a carbon reduction by −1.14 ± 0.63 and −1.20 ± 0.06 Mg ha−1 yr−1, respectively. The validated DayCENT model suggests that all SOC pools declined. We postulate that conventional CS production has adverse effects on C and N dynamics in Midwestern United States.
    Description: Key Points: Eddy covariance shows a decrease in ecosystem C after 11 yr of corn‐soybean production. Soil inorganic C decreased in 90–120 cm, and organic C decreased in 0–15 cm after 11 yr. DayCENT simulations suggest current conventional corn‐soybean rotations decrease all SOC pools in topsoil layer.
    Description: ORISE http://dx.doi.org/10.13039/100006229
    Keywords: 551.9 ; Midwestern U.S. region ; biogeochemical cycles ; carbon cycles ; nitrogen cycles
    Type: article
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    CITATION GEO-LEO
  • 2
    Electronic Resource
    Electronic Resource
    ENERGY BALANCE OF A CORN RESIDUE-COVERED FIELD DURING SNOWMELT (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 34 (1998), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Transport of agricultural chemicals in runoff and recharge waters from snowmelt and soil thawing may represent a significant event in terms of annual contaminant loadings in temperate regions. Improved understanding of the melt dynamics of shallow snowpacks is necessary to fully assess the implications for water quality. The objective of this study was to measure the energy balance components of a corn (Zea mays L.) stubble field during the melting of its snowcover. Net radiation (Rn), soil (G), sensible (H), and latent (Q) heat fluxes were measured in a field near Ames, Iowa, during the winter of 1994–1995. Energy consumed by melting including change in energy storage of the snowpack was determined as the residual of the measured energy balance. There was continuous snowcover at the field site for 71 days (maximum depth = 222 mm) followed by an open period of 11 days before additional snowfall and a second melt period. The net radiation and snow melt/energy storage change (5) terms dominated the energy balance during both measurement intervals. Peak daily sensible and latent heat fluxes were below 100 W m−2 on all days except the last day of the second melt period. There was good agreement between predicted and measured values of H and Q during the melting of an aged snow layer but poorer agreement during the melt of fresh snow. Both snowpacks melted rapidly and coincident changes in soil moisture storage were observed. Improved estimates of Q and H, especially for partially open surfaces, will require better characterization of the surface aerodynamic properties and spatially-representative surface temperature measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1998.tb05440.x
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  • 3
    Electronic Resource
    Electronic Resource
    Canopy temperature and water stress of cotton crops with complete and partial ground cover (1984)
    Springer
    Irrigation science 5 (1984), S. 37-46 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The use of canopy and air temperature differences to compute a crop water stress index (CWSI) for assessing plant water status was investigated using cotton crop canopies that either fully or partially covered the ground. The complete ground cover canopy condition was studied in a well watered moisture regime in a rainout shelter with measurements made on six Texas cotton race stocks. The partial ground cover canopy situation was investigated in a well watered moisture regime of a commercial cotton variety ‘Paymaster 266’ grown in the field. The slope of the nonstressed baseline of the CWSI for a cotton canopy with about 50% ground cover was approximately one-half that reported for full canopies. Values of CWSI calculated with “theoretical” and “empirical” procedures agreed more closely under a complete canopy condition than under a partial canopy situation. Values of aerodynamic resistance (r a ) and canopy resistance for well watered soil moisture conditions (r ep )were estimated in order to use the theoretical procedure of computing CWSI. Values of r a ranged from 10 to 15 sm−1 and r cp from 50 to 60 sm−1. Both the theoretical and empirical procedures showed much promise, but more information is needed to develop techniques for evaluating r a and r cp under differing canopy and environmental conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00275036
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  • 4
    Electronic Resource
    Electronic Resource
    Response of cotton water stress indicators to soil salinity (1984)
    Springer
    Irrigation science 5 (1984), S. 25-36 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A field study was conducted on cotton (Gossypium hirsutum L. c.v. Acala SJ-2) to investigate the effects of soil salinity on the responses of stress indices derived from canopy temperature, leaf diffusion resistance and leaf water potential. The four salinity treatments used in this study were obtained by mixtures of aqueduct and well water to provide mean soil water electrical conductivities of 17, 27, 32 and 38 dS/m in the upper 0.6 m of soil profile. The study was conducted on a sandy loam saline-alkali soil in the lower San Joaquin Valley of California on 30 July 1981, when the soil profile was adequately irrigated to remove any interference of soil matric potential on the stress measurements. Measurements of canopy temperature, leaf water potential and leaf diffusion resistance were made hourly throughout the day. Crop water stress index (CWSI) estimates derived from canopy temperature measurements in the least saline treatment had values similar to those found for cotton grown under minimum salinity profiles. Throughout the course of the day the treatments affected CWSI values with the maximum differences occurring in mid-afternoon. Salinity induced differences were also evident in the leaf diffusion resistance and leaf water potential measurements. Vapor pressure deficit was found to indicate the evaporative demand at which cotton could maintain potential water use for the various soil salinity levels studied. At vapor pressure deficits greater than 5 kPa, cotton would appear “stressed” at in situ soil water electrical conductivities exceeding 15 dS/m. The CWSI was as sensitive to osmotic stress as other, more traditional plant measures, provided a broader spatial resolution and appeared to be a practical tool for assessing osmotic stress occurring within irrigated cotton fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00275035
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  • 5
    Electronic Resource
    Electronic Resource
    The utilization of thermal infrared radiation measurements from grain sorghum crops as a method of assessing their irrigation requirements (1983)
    Springer
    Irrigation science 3 (1983), S. 259-268 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field studies on irrigated grain sorghum (Sorghum bicolor L. Moench) crops were conducted in California for three years to evaluate the use of thermal infrared measurements to estimate water use and detect crop stress. These studies were conducted on a Yolo loam soil with different rooting volumes to limit the water availability. Data show that the stress-degree-day index (midday comparison of canopy-air temperature differences) provides a valid indicator of crop stress, and that the canopy-air temperature difference increases rapidly above zero when more than 65% of the available water is depleted. The canopy-air temperature difference is also related to leaf-water potential, with an increase above zero when the potential decreases below − 1.1 MPa (=11 bars). Improvement of the performance of the stress-degree-day index through compensation for environmental variability was achieved by including measurements of the plant water stress which are related to available water extracted. It is concluded that remote sensing of emitted thermal radiation offers a promising technique which can be incorporated into irrigation management programs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00272841
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  • 6
    Electronic Resource
    Electronic Resource
    Crop water stress index relationships with crop productivity (1990)
    Springer
    Irrigation science 11 (1990), S. 93-99 
    Details
    ISSN: 1432-1319
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Field experiments between 1983 and 1987 were used to study the effect of crop development on crop water stress index (CWSI) parameters and the relationship of CWSI with the yield of cotton and grain sorghum. The absolute slopes of nonstressed baselines (NSBL) generally increased until canopy cover reached 70% (Table 1). NSBL derived from data collected when canopy temperature exceeded 27.4 °C had greater absolute slopes and higher R 2-values than NSBL that included all diurnal measurements (Table 1). Average CWSI values of cotton and grain sorghum grown under varying soil water regimes were negatively correlated with yield. Grain sorghum yield was more sensitive to CWSI values than was cotton lint yield (Figs. 1 and 2). Multiyear data analysis indicated that yields from cotton that experienced a completely stressed condition during part of each day during the boll setting period would be 40% of those from completely nonstressed cotton (Fig. 3). Negative values of CWSI computed for cotton growing under non-water stressed conditions were associated with uncertainties in calculations of aerodynamic resistance (r aand in estimating canopy resistance at potential evapotranspiration (r cp).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00188445
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  • 7
    Electronic Resource
    Electronic Resource
    Management of the soil-plant-atmosphere complex (1979)
    Springer
    Water, air & soil pollution 12 (1979), S. 73-81 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The area of land which man manipulates through cultivation is 3.2×109 ha; however, the impact from this system has been large. The soil-plant-atmosphere complex is very dynamic with the plant continually growing throughout a constantly changing atmospheric environment, i.e., radiation, temperature, and precipitation. However, a basis for all exchanges is the energy balance and all changes are made through this balance. Two impacts of this system are realized in water and wind erosion. Both are detrimental to agricultural land and proper management of the system alleviates the impact of these two forces. Other changes which occur are reduction in evaporation and soil temperature under crop cover. There is needed, however, a more thorough understanding of the energy exchanges throughout the growing season, especially as it applies to feed-backs between plant response and the environment, soil derived aerosols, and biogenic ice nuclei. These will provide a better understanding of how we manipulate this complex for maintenance of our world's food supply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01060526
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  • 8
    Electronic Resource
    Electronic Resource
    Microclimate effects of crop residues on biological processes (1996)
    Springer
    Theoretical and applied climatology 54 (1996), S. 47-59 
    Details
    ISSN: 1434-4483
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary Residues from crops left on the soil surface have an impact on the microclimate, primarily temperature, within the soil and the atmosphere; but, the impact on the biological system is largely unknown. Residue is assumed to have a positive impact on the biological system in the soil and a negative impact on crop growth. This report investigates the effect of standing residue on the microclimate surrounding a cotton (Gossypium hirsutum L.) crop in a semi-arid environment and the effect of flat residue on the seasonal soil temperature and soil water regimes in a humid climate with a corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production system. A study was conducted during 1987 and 1988 in a semi-arid climate at Lubbock, Texas using standing wheat stubble to shelter cotton from wind. In this study soil water, microclimatic variables, and plant growth were measured within standing stubble and bare soil during the early vegetative growth period. Air temperatures were warmer at night within the standing residue and the air more humid throughout the day. This led to a reduction in the soil water evaporation rate and an increase in the water use efficiency of the cotton plant within the stubble. Studies on corn residue with continuous corn and corn-soybean rotations with no-till, chiselplow, and moldboard plow tillage practices in central Iowa showed that the average soil temperatures in the upper soil profile were not affected by the presence of flat residue after tillage. Diurnal temperature ranges were most affected by the residue throughout the year. The largest effect of the residue on soil temperature was in the fall after harvest when no-till fields cooled more slowly than tilled fields. In the spring, surface residue decreased the soil water evaporation rate and increased the soil water storage within the soil profile covered with residue. In years with below normal rainfall, the additional stored soil water due to the surface residue was used by the plant to maintain transpiration rates at optimal levels during the early vegetative growth period. The biological implications of crop residue on the soil surface can be more positive than negative and increasing our understanding of the physical environment and biological system interactions will lead to improved resource management.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00863558
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  • 9
    Electronic Resource
    Electronic Resource
    Spatial Variation of Rainfall over a Large Watershed in Central Iowa (1999)
    Springer
    Theoretical and applied climatology 64 (1999), S. 49-60 
    Details
    ISSN: 1434-4483
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary Rainfall amounts and the distribution across the landscape are critical to decision-making and evaluation of hydrological models. Spatial variation in rainfall has been observed through anecdotal evidence and limited studies; however, there is little quantitative evidence that can be used to assess rainfall variation within a watershed on a daily, monthly, or yearly temporal scale. This study was conducted to quantify the spatial variation within a watershed in central Iowa and to determine if there were consistent differences among rain gages for the period from 1991 through 1998. The study was conducted within Walnut Creek watershed located south of Ames, Iowa on the Des Moines Lobe Landform region. The topography of this 5130 ha watershed is characterized by gently rolling fields with a narrow area of steeper land along the stream in the lower part of the watershed. Twenty-two tipping bucket rain gages were placed throughout the watershed and rainfall was recorded as 5 minute totals and then aggregated into daily totals. Accumulation of errors of the 5 minute values into the daily totals were considered to be random. There was a large coefficient of variation in the average daily totals; however, there was no consistent pattern of variation among rain gages, and coefficient of variation decreased with amount of rain. Each rain gage had an equal chance of receiving the lowest or highest rainfall total for any given storm event. When the daily average was computed over the year, there were no differences among rain gages. Monthly and yearly totals showed a decreased coefficient of variation compared to daily totals. There was no consistent pattern of spottiness within the watershed and if daily rainfall amounts are required for a decision, then direct measurements may be required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007040050110
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  • 10
    Electronic Resource
    Electronic Resource
    Spatial variability of rainfall at an experimental station in Niger, West Africa (1990)
    Springer
    Theoretical and applied climatology 42 (1990), S. 33-39 
    Details
    ISSN: 1434-4483
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary Variability of rainfall in the semi-arid regions can cause problems in evaluating experimental trials. To describe the spatial rainfall patterns over a large experimental station, rainfall was monitored during the 1986 and 1987 rainy seasons using 18 raingages over the 500 ha experimental station of ICRISAT Sahelian Center, in Niger, West Africa. Average relative variability of individual rain storms, defined as the percentage deviation from the mean, varied from 2 to 62%, while the variability over the rainy season was 17.1%. Isohyetal patterns of individual rain storms as well as seasonal totals showed distinct coherence in the spatial pattern over the station. The effects of total volume, duration, direction and intensity of storms and the time of year on the spatial correlations were analyzed. Storm value showed a large influence on the correlation decay with distance. Correlations in the W — E and SW — NE directions were higher in comparison to those in the N — S and NW — SE directions. Point rainfall measurements were better correlated with the network average rainfall than with the rainfall recorded at the meteorological station. Variograms among raingages revealed that the distance of independence was approximately 1 000 m for almost all storms. Use of a network of raingages over agricultural experiment stations reduces the average relative variability of areal rainfall estimates and provides a means to develop simple relations for estimation of point rainfall for individual applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00865524
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