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Papers by Jon D. Hanson

Rangeland Ecology & Management / Journal of Range Management Archives, Jul 1, 1982

Net carbon dioxide assimilation rates (PN) were measured for individuals from two Texas honey mes... more Net carbon dioxide assimilation rates (PN) were measured for individuals from two Texas honey mesquite populations grown under controlled water stress, temperature, and light treatments. Maximum PN observed for the various tests ranged from 0.69 to 0.82 mg l rne2se1. Net assimilation rates were significantly lower in the west Texas population than in the east Texas population under high and low water stress. Maximum PN at 1.35 mmol l rnm2se1 photon flux density were reached under low water stress at 20" C and 30 O C for east and west Texas populations, respectively. The response of PN to light was similar to responses reported for other CB species; and 81 to 99% of the variability in the data was accounted for by using a hyperbolic light response model. Light use efficiency was lower for the west Texas population, and for high temperature and water stress. High temperature and water stress treatments also caused substantial decreases in the estimated theoretical maximum net assimilation rates. Finally, the light saturation point of mesquite varied depending on population and water stress.

Journal of Range Management, Sep 1, 1983

Honey mequite [Prosopisllrliitro (Swutz) DC. vu.ghmdu~a (Torr.) Cockcreii] response to spnys of 2... more Honey mequite [Prosopisllrliitro (Swutz) DC. vu.ghmdu~a (Torr.) Cockcreii] response to spnys of 2,4&T [(2,4,5-tricbio-Wb-xY)8=ti-W8ndpiflorun(-*rcid) + 2,4,5-T ~8s ev8iu8ted urd correlated with nuximum driiy photosynthetic rate, upwud movement of methyiene dye, xylem pressure potentW, 8nd percent soii w8ter. Piciorun + 2,4,5-T ~8s superior to 2,4,5-T 8lone for kiiling honey mesquite from M8y 15 through Augusl4. Time of d8y the herbicide ~8s rppiied h8d no dgnifiant effect on control. M8ximum d8iiy photosynthetic rrte varied from 32.9 to 10.1 mg Co1 dm-' ie8fue8 hr-' 8nd ~88 highly correi8ted (r = 0.89 to 0.92) with honey menquite control with herbicides. R8te of upwud movement of methykne blue dye in the xylem vuied from 295 to 44 cm hr-'. (MP8) while soil w8ter content v8ried from 11.5 to 18.6%. UpwUa movement of methyiene blue dye, xylem pressure potenti 8nd percent soii w8ter were not signifkantiy correi8ted with honey mesquite control. Honey mesquite [Rosopis julr&'ora (Swartx) DC. var. glandu-Zosa (Torr.) Cockerell], a woody perennial of the Leguminosae, is adapted to a broad range of environmental conditions. It is distributed throughout much of the southwestern United States and occupies about 25 million ha of Texas rangeland (Smith and Rechenthin 1964). Honey mesquite is generally controlled by foliar sprays of 2,4,5-T [(2,4,Qrichlorophenoxy)acetic acid], picloram (4-amine-3,5,6-trichloropicolinic acid) + 2,4,5-T, or dicamba (36 dichloro-o-anisic acid) + 2,4,5-T, by basal treatment with diesel oil; or by mechanical treatments including bulldozing or chaining. Also, karbutilate [tert-butylcarbamic acid ester with 3(m-hydro-xyphenyl>l,l-dimethylurea[ and tebuthiuron {

Journal of Range Management, 2005

Journal of Range Management, Jul 1, 1982

Net carbon dioxide assimilation rates (PN) were measured for individuals from two Texas honey mes... more Net carbon dioxide assimilation rates (PN) were measured for individuals from two Texas honey mesquite populations grown under controlled water stress, temperature, and light treatments. Maximum PN observed for the various tests ranged from 0.69 to 0.82 mg l rne2se1. Net assimilation rates were significantly lower in the west Texas population than in the east Texas population under high and low water stress. Maximum PN at 1.35 mmol l rnm2se1 photon flux density were reached under low water stress at 20" C and 30 O C for east and west Texas populations, respectively. The response of PN to light was similar to responses reported for other CB species; and 81 to 99% of the variability in the data was accounted for by using a hyperbolic light response model. Light use efficiency was lower for the west Texas population, and for high temperature and water stress. High temperature and water stress treatments also caused substantial decreases in the estimated theoretical maximum net assimilation rates. Finally, the light saturation point of mesquite varied depending on population and water stress.

Ecological Modelling, 2016

Agricultural production in the United States is undergoing marked changes due to rapid shifts in ... more Agricultural production in the United States is undergoing marked changes due to rapid shifts in consumer demands, input costs, and concerns for food safety and environmental impact. Agricultural production systems are comprised of multidimensional components and drivers that interact in complex ways to influence production sustainability. In a mixed-methods approach, we combine qualitative and quantitative data to develop and simulate a system dynamics model that explores the systemic interaction of these drivers on the economic, environmental and social sustainability of agricultural production. We then use this model to evaluate the role of each driver in determining the differences in sustainability between three distinct production systems: crops only, livestock only, and an integrated crops and livestock system. The result from these modelling efforts found that the greatest potential for sustainability existed with the crops only production system. While this study presents a stand-alone contribution to sector knowledge and practice, it encourages future research in this sector that employs similar systems-based methods to enable more sustainable practices and policies within agricultural production.

Transactions of the ASAE, 2003

ABs'rnAcr. The ability to predict and manage crop growth under varying available water conditions... more ABs'rnAcr. The ability to predict and manage crop growth under varying available water conditions is of vital importance to the agricultural community since water is the most important limiting factor for agricultural productivity, especially in semi.-rid regions. This study evaluated an agricultural system mode4 the USDA-ARS Root Zone Water Quality Model (RZWQM), for its ability to simulate the responses of corn (Zea mays L.) growth and yield to various levels of water stress,

Soil and Tillage Research, 2007

Agriculture and the plow originated 10-13 millennia ago in the Fertile Crescent of the Near East,... more Agriculture and the plow originated 10-13 millennia ago in the Fertile Crescent of the Near East, mostly along the Tigris, Euphrates, Nile, Indus and Yangtze River valleys, and were introduced into Greece and southeastern Europe $8000 years ago. The wooden plow, called an ard, evolved into the ''Roman plow'', with an iron plowshare, described by Virgil around 1 AD and was used in Europe until the fifth century. It further evolved into a soil inverting plow during the 8th to 10th century. In the U.S., a moldboard plow was designed by Thomas Jefferson in 1784, patented by Charles Newfold in 1796, and marketed in the 1830s as a cast iron plow by a blacksmith named John Deere. Use of the plow expanded rapidly with the introduction of the ''steam horse'' in 1910 that led to widespread severe soil erosion and environmental degradation culminating in the Dust Bowl of the 1930s. A transition from moldboard plow to various forms of conservation tillage began with the development of 2,4-D after World War II. No-till is presently practiced on about 95 million hectares globally. No-till technologies are very effective in minimizing soil and crop residue disturbance, controlling soil evaporation, minimizing erosion losses, sequestering C in soil and reducing energy needs. However, no-till is effective only with the use of crop residue as mulch, which has numerous competing uses. No-till farming can reduce yield in poorly drained, clayey soils when springtime is cold and wet. Soil-specific research is needed to enhance applicability of no-till farming by alleviating biophysical, economic, social and cultural constraints. There is a strong need to enhance sustainability of production systems while improving the environmental quality.

Renewable Agriculture and Food Systems, 2008

During the 20th century, US agriculture underwent vast transformations. The number of farmers has... more During the 20th century, US agriculture underwent vast transformations. The number of farmers has decreased, more farmers are relying on off-farm income, agriculture's proportion of the US GDP has declined, and a minority of non-metro counties in the US are farming dependent. Agriculture's evolution will continue and we have identified key trends and future challenges to effectively manage our changing agricultural system. Eight current trends in US agriculture were identified. These included: (1) increased land degradation; (2) competing land uses; (3) focus on single ecosystem service; (4) increase in farm size; (5) movement toward commercialization; (6) genetic engineering; (7) global markets; and (8) changing social structure. Future trends likely to affect agriculture include: (1) diminishing and increasingly volatile farm incomes; (2) reduced government involvement in food regulation; (3) continued transition from farming to agribusiness; (4) land-use will become a maj...

Journal of Sustainable Agriculture, 2010

This article is not subject to US copyright law. Mention of trade names is given to provide speci... more This article is not subject to US copyright law. Mention of trade names is given to provide specific information and does not constitute recommendation or endorsement by the USDA-ARS.

Biomass and Bioenergy, 2005

Switchgrass (Panicum virgatum L.) is considered to be a valuable bioenergy crop with significant ... more Switchgrass (Panicum virgatum L.) is considered to be a valuable bioenergy crop with significant potential to sequester soil organic carbon (SOC). A study was conducted to evaluate soil carbon stocks within established switchgrass stands and nearby cultivated cropland on farms throughout the northern Great Plains and northern Cornbelt. Soil from 42 paired switchgrass/cropland sites throughout MN, ND, and SD was sampled to a depth of 120 cm and analyzed for soil carbon in depth increments of 0-5, 5-10, 10-20, 20-30, 30-60, 60-90, and 90-120 cm. SOC was greater (Po0:1) in switchgrass stands than cultivated cropland at 0-5, 30-60, and 60-90 cm. Differences in SOC between switchgrass stands and cultivated cropland were especially pronounced at deeper soil depths, where treatment differences were 7.74 and 4.35 Mg ha À1 for the 30-60 and 60-90 cm depths, respectively. Greater root biomass below 30 cm in switchgrass likely contributed to trends in SOC between switchgrass stands and cultivated cropland. Switchgrass appears to be effective at storing SOC not just near the soil surface, but also at depths below 30 cm where carbon is less susceptible to mineralization and loss.

Agronomy Journal, 2005

Calibration procedures and data used to parameterize a model, including model components that may... more Calibration procedures and data used to parameterize a model, including model components that may or may not have been addressed, are generally not well documented in modeling studies. A comprehensive description of the process and parameters used for calibrating the Root Zone Water Quality Model, v. 1.3.2004.213, is presented in this article. The model was calibrated to simulate tile drainage and leached nitrate under conventional tillage management practices for maize (Zea mays L.) production followed by a rye (Secale cereale L.) cover crop in Cecil soils (kaolinitic, thermic, Typic Kanhapludults), and for cotton (Gossypium hirsutum L.) development in the Georgia Piedmont. Tile drainage and nitrate leaching were simulated within 15% of the observed values in the calibrated maize scenarios with and without the soil macroporosity option. Simulated and observed tile drainage and leached nitrate were not significantly different, and the simulated values were not significantly differen...

Agronomy Journal, 2005

2004), will be greatly enhanced by effective information about the dynamics of fine root growth a... more 2004), will be greatly enhanced by effective information about the dynamics of fine root growth and dependent Study of root growth is important for understanding C flow through rhizosphere biology. Another area of application for plants to the soil and for modeling plant-soil interactions. Fine root growth can be observed through minirhizotrons (MRs), tubes installed fine root growth information is in soil and crop managein the field. We compared the use of fixed-wall (F-wall) MRs, 5.6 cm ment. For example, Merrill et al. (1996) have linked the in diam., and pressurized-wall (P-wall) MRs, 9.6 cm in diam., with effects of conservation tillage management on wheat an inner cylinder and an outer wall of plastic sheeting kept under growth through MR measurement of fine root growth. constant air pressure. Root growth was measured with a micro-video A general model of plant-soil interactions for undercamera for 3 yr in eight crop species growing on Pachic Haplustoll soil: standing the effects of crop-soil management on the canola, Brassica rapa L.; crambe, Crambe abysinnica Hochst. ex R.E.

Agronomy Journal, 2007

Field research was conducted to determine the influence of crop and crop sequencing on crop resid... more Field research was conducted to determine the influence of crop and crop sequencing on crop residue coverage of soil with 10 crops [buckwheat (Fagopyrum esculentum Moench), canola (Brassica napus L.), chickpea (Cicer arietinum L.), corn (Zea mays L.), dry pea (Pisum sativum L.), grain sorghum [Sorghum bicolor (L.) Moench], lentil (Lens culinaris Medik.), oil seed sunflower (Helianthus annuus L.), proso millet (Panicum miliaceum L.), and hard red spring wheat (Triticum aestivum L.)]. Crop residue production was obtained. Crop residue coverage of the soil surface was measured with a transect technique at the time of seeding spring wheat. Crop residue coverage varied and was more clearly associated with the second-year crop than with the first-year crop of a 2-yr crop sequence. Crop sequences composed of spring wheat, proso millet, and grain sorghum had higher crop residue coverage compared with sequences composed of the other crops. When these three crops and three crops that provide lower crop residue coverage of soil the subsequent year (lentil, chickpea, and sunflower) were analyzed as a subset to compare various sequences of crops providing a range of residue coverage, for example, lower (first yr)/lower (second yr), the surface residue coverage ranged from 65% for the lower/lower combination to 93% for the higher/ higher combination in 2004 and from 56 to 94% in 2005, respectively. A producer operating on more fragile soil and concerned about reducing soil erosion hazards would be advised to grow crops that provide higher residue coverage in the year before crops that provide lower residue coverage.

Agronomy Journal, 2007

Crop sequence is an important management practice that may lower the risk for leaf spot diseases ... more Crop sequence is an important management practice that may lower the risk for leaf spot diseases of spring wheat (Triticum aestivum L.). Field research was conducted near Mandan, ND, to determine the impact of crop sequences on leaf spot diseases of hard red spring wheat early in the growing season. Spring wheat was evaluated for disease severity following crop sequence combinations of 10 crops [buckwheat (Fagopyrum esculentum Moench), canola (Brassica napus L.), chickpea (Cicer arietinum L.), corn (Zea mays L.), dry pea (Pisum sativum L.), grain sorghum [Sorghum bicolor (L.) Moench], lentil (Lens culinaris Medik.), oil seed sunflower (Helianthus annuus L.), proso millet (Panicum miliaceum L.), and hard red spring wheat). Spring wheat leaves with distinct lesions were collected for determination of lesion number and percentage necrosis data, which were used to estimate leaf spot disease severity. Pyrenophora tritici-repentis (Died.) Drechs., the cause of tan spot, and Phaeosphaeria nodorum (E. Mu ¨ller) Hedjaroude, the cause of Stagonospora nodorum blotch, were the major leaf spot diseases and consistently present throughout the growing season. The frequency of isolation following alternative crops was generally lower compared with spring wheat following wheat. Leaf spot diseases on spring wheat were impacted by crop sequencing. Spring wheat following crop sequences with alternative crops for 1 or 2 yr had lower levels of disease severity compared with a continuous spring wheat treatment early in the growing season. Disease severity was apparently not related to the percentage of crop residue coverage on the soil surface associated with various crop sequence combinations. New alternative crops preceding spring wheat reduce levels of leaf spot diseases.

Dynamic Cropping Systems

Agronomy Journal, 2002

ABSTRACT Future trends in population growth, energy use, climate change, and globalization will c... more ABSTRACT Future trends in population growth, energy use, climate change, and globalization will challenge agriculturists to develop innovative production systems that are highly productive and environmentally sound. Furthermore, future agricultural production systems must possess an inherent capacity to adapt to change to be sustainable. Given this context, adoption of dynamic cropping systems is proposed to meet multiple agronomic and environmental objectives through the enhancement of management adaptability to externalities. Dynamic cropping systems are a form of agricultural production that relies on an annual strategy to optimize the outcome of (i) production, (ii) economic, and (iii) resource conservation goals using ecologically-based management principles. Dynamic cropping systems are inherently complex, possessing larger crop portfolios and greater crop diversity and sequencing flexibility as compared with monoculture and fixed-sequence cropping systems. Greater crop diversity and sequencing flexibility within dynamic cropping systems may result in reduced weed and disease infestations, greater nutrient- and precipitation-use efficiency, decreased requirements of exogenous inputs, and lower production risk. The multiple interactions among management components of dynamic cropping systems demand greater management intensity than monoculture and fixed-sequence cropping systems. Further development of dynamic cropping systems is important for managing crop production systems in a sustainable manner. These systems can ultimately assist land managers to develop new and improved land-use strategies to the benefit of generations to come.

Evaluation of the upgraded spur model (spur2.4)

Ecological Modelling, 1999

spur (Simulation of Production and Utilization of Rangelands) is a grassland ecosystem simulation... more spur (Simulation of Production and Utilization of Rangelands) is a grassland ecosystem simulation model. spur2.4 integrates all previous versions of spur. The changes from spur91 make the model more applicable to the southern Great Plains. The forage submodel from spur2 predicts forage intake and diet selection by grazing herbivores, and the cow-calf submodel from spur2 simulates all individuals in a herd for their full life cycle, based on defined genetic traits. The soil organic matter submodel from century was added to improve soil carbon and nitrogen cycling. spur2.4 output is compared with observed values from the Texas Experimental Ranch, Throckmorton, Texas. The changes made in creating spur2.4 have considerably improved the utility and accuracy of the spur model for north Texas. Soil moisture predictions are improved (spur91 is 137% and spur2.4 is 106% of observed, R=0.79–0.86), but run-off is still not adequate (R=0.65–0.76) and monthly evaporation is lower (spur91 is 94% and spur2.4 is 95%) than observed. Soil carbon level predictions by the century submodel are within range of the data, and output is stable over the simulation period. Predictions of individual plant species productivity compared with observed data are improved with spur2.4 (R=0.79–0.98). Between-season plant growth and long-term persistence are simulated well. The addition of the century soil organic matter submodel increased nitrogen level predictions resulting in more accurate predictions of animal weight gain. Steer weight gains are typical for north Texas. Simulation of cow-calf mass was good (R>0.98) as was production per hectare and per cow. The addition of the cow-calf model increases the utility of the model. The paper identifies portions of the model that need further validation and field research to improve model utility and credibility for use in natural resource management.

assessing the impact of management practices on multiple agroecosystem functions.

Journal of Range Management, 2002

Rangeland plant productivity and species composition are affected by moisture availability and gr... more Rangeland plant productivity and species composition are affected by moisture availability and grazing intensity. We examined warm-and cool-season grass productivity and relative dis-

Advances in Agroecology, 2009

Rangeland Ecology & Management / Journal of Range Management Archives, Jul 1, 1982

Net carbon dioxide assimilation rates (PN) were measured for individuals from two Texas honey mes... more Net carbon dioxide assimilation rates (PN) were measured for individuals from two Texas honey mesquite populations grown under controlled water stress, temperature, and light treatments. Maximum PN observed for the various tests ranged from 0.69 to 0.82 mg l rne2se1. Net assimilation rates were significantly lower in the west Texas population than in the east Texas population under high and low water stress. Maximum PN at 1.35 mmol l rnm2se1 photon flux density were reached under low water stress at 20" C and 30 O C for east and west Texas populations, respectively. The response of PN to light was similar to responses reported for other CB species; and 81 to 99% of the variability in the data was accounted for by using a hyperbolic light response model. Light use efficiency was lower for the west Texas population, and for high temperature and water stress. High temperature and water stress treatments also caused substantial decreases in the estimated theoretical maximum net assimilation rates. Finally, the light saturation point of mesquite varied depending on population and water stress.

Journal of Range Management, Sep 1, 1983

Honey mequite [Prosopisllrliitro (Swutz) DC. vu.ghmdu~a (Torr.) Cockcreii] response to spnys of 2... more Honey mequite [Prosopisllrliitro (Swutz) DC. vu.ghmdu~a (Torr.) Cockcreii] response to spnys of 2,4&T [(2,4,5-tricbio-Wb-xY)8=ti-W8ndpiflorun(-*rcid) + 2,4,5-T ~8s ev8iu8ted urd correlated with nuximum driiy photosynthetic rate, upwud movement of methyiene dye, xylem pressure potentW, 8nd percent soii w8ter. Piciorun + 2,4,5-T ~8s superior to 2,4,5-T 8lone for kiiling honey mesquite from M8y 15 through Augusl4. Time of d8y the herbicide ~8s rppiied h8d no dgnifiant effect on control. M8ximum d8iiy photosynthetic rrte varied from 32.9 to 10.1 mg Co1 dm-' ie8fue8 hr-' 8nd ~88 highly correi8ted (r = 0.89 to 0.92) with honey menquite control with herbicides. R8te of upwud movement of methykne blue dye in the xylem vuied from 295 to 44 cm hr-'. (MP8) while soil w8ter content v8ried from 11.5 to 18.6%. UpwUa movement of methyiene blue dye, xylem pressure potenti 8nd percent soii w8ter were not signifkantiy correi8ted with honey mesquite control. Honey mesquite [Rosopis julr&'ora (Swartx) DC. var. glandu-Zosa (Torr.) Cockerell], a woody perennial of the Leguminosae, is adapted to a broad range of environmental conditions. It is distributed throughout much of the southwestern United States and occupies about 25 million ha of Texas rangeland (Smith and Rechenthin 1964). Honey mesquite is generally controlled by foliar sprays of 2,4,5-T [(2,4,Qrichlorophenoxy)acetic acid], picloram (4-amine-3,5,6-trichloropicolinic acid) + 2,4,5-T, or dicamba (36 dichloro-o-anisic acid) + 2,4,5-T, by basal treatment with diesel oil; or by mechanical treatments including bulldozing or chaining. Also, karbutilate [tert-butylcarbamic acid ester with 3(m-hydro-xyphenyl>l,l-dimethylurea[ and tebuthiuron {

Journal of Range Management, 2005

Journal of Range Management, Jul 1, 1982

Net carbon dioxide assimilation rates (PN) were measured for individuals from two Texas honey mes... more Net carbon dioxide assimilation rates (PN) were measured for individuals from two Texas honey mesquite populations grown under controlled water stress, temperature, and light treatments. Maximum PN observed for the various tests ranged from 0.69 to 0.82 mg l rne2se1. Net assimilation rates were significantly lower in the west Texas population than in the east Texas population under high and low water stress. Maximum PN at 1.35 mmol l rnm2se1 photon flux density were reached under low water stress at 20" C and 30 O C for east and west Texas populations, respectively. The response of PN to light was similar to responses reported for other CB species; and 81 to 99% of the variability in the data was accounted for by using a hyperbolic light response model. Light use efficiency was lower for the west Texas population, and for high temperature and water stress. High temperature and water stress treatments also caused substantial decreases in the estimated theoretical maximum net assimilation rates. Finally, the light saturation point of mesquite varied depending on population and water stress.

Ecological Modelling, 2016

Agricultural production in the United States is undergoing marked changes due to rapid shifts in ... more Agricultural production in the United States is undergoing marked changes due to rapid shifts in consumer demands, input costs, and concerns for food safety and environmental impact. Agricultural production systems are comprised of multidimensional components and drivers that interact in complex ways to influence production sustainability. In a mixed-methods approach, we combine qualitative and quantitative data to develop and simulate a system dynamics model that explores the systemic interaction of these drivers on the economic, environmental and social sustainability of agricultural production. We then use this model to evaluate the role of each driver in determining the differences in sustainability between three distinct production systems: crops only, livestock only, and an integrated crops and livestock system. The result from these modelling efforts found that the greatest potential for sustainability existed with the crops only production system. While this study presents a stand-alone contribution to sector knowledge and practice, it encourages future research in this sector that employs similar systems-based methods to enable more sustainable practices and policies within agricultural production.

Transactions of the ASAE, 2003

ABs'rnAcr. The ability to predict and manage crop growth under varying available water conditions... more ABs'rnAcr. The ability to predict and manage crop growth under varying available water conditions is of vital importance to the agricultural community since water is the most important limiting factor for agricultural productivity, especially in semi.-rid regions. This study evaluated an agricultural system mode4 the USDA-ARS Root Zone Water Quality Model (RZWQM), for its ability to simulate the responses of corn (Zea mays L.) growth and yield to various levels of water stress,

Soil and Tillage Research, 2007

Agriculture and the plow originated 10-13 millennia ago in the Fertile Crescent of the Near East,... more Agriculture and the plow originated 10-13 millennia ago in the Fertile Crescent of the Near East, mostly along the Tigris, Euphrates, Nile, Indus and Yangtze River valleys, and were introduced into Greece and southeastern Europe $8000 years ago. The wooden plow, called an ard, evolved into the ''Roman plow'', with an iron plowshare, described by Virgil around 1 AD and was used in Europe until the fifth century. It further evolved into a soil inverting plow during the 8th to 10th century. In the U.S., a moldboard plow was designed by Thomas Jefferson in 1784, patented by Charles Newfold in 1796, and marketed in the 1830s as a cast iron plow by a blacksmith named John Deere. Use of the plow expanded rapidly with the introduction of the ''steam horse'' in 1910 that led to widespread severe soil erosion and environmental degradation culminating in the Dust Bowl of the 1930s. A transition from moldboard plow to various forms of conservation tillage began with the development of 2,4-D after World War II. No-till is presently practiced on about 95 million hectares globally. No-till technologies are very effective in minimizing soil and crop residue disturbance, controlling soil evaporation, minimizing erosion losses, sequestering C in soil and reducing energy needs. However, no-till is effective only with the use of crop residue as mulch, which has numerous competing uses. No-till farming can reduce yield in poorly drained, clayey soils when springtime is cold and wet. Soil-specific research is needed to enhance applicability of no-till farming by alleviating biophysical, economic, social and cultural constraints. There is a strong need to enhance sustainability of production systems while improving the environmental quality.

Renewable Agriculture and Food Systems, 2008

During the 20th century, US agriculture underwent vast transformations. The number of farmers has... more During the 20th century, US agriculture underwent vast transformations. The number of farmers has decreased, more farmers are relying on off-farm income, agriculture's proportion of the US GDP has declined, and a minority of non-metro counties in the US are farming dependent. Agriculture's evolution will continue and we have identified key trends and future challenges to effectively manage our changing agricultural system. Eight current trends in US agriculture were identified. These included: (1) increased land degradation; (2) competing land uses; (3) focus on single ecosystem service; (4) increase in farm size; (5) movement toward commercialization; (6) genetic engineering; (7) global markets; and (8) changing social structure. Future trends likely to affect agriculture include: (1) diminishing and increasingly volatile farm incomes; (2) reduced government involvement in food regulation; (3) continued transition from farming to agribusiness; (4) land-use will become a maj...

Journal of Sustainable Agriculture, 2010

This article is not subject to US copyright law. Mention of trade names is given to provide speci... more This article is not subject to US copyright law. Mention of trade names is given to provide specific information and does not constitute recommendation or endorsement by the USDA-ARS.

Biomass and Bioenergy, 2005

Switchgrass (Panicum virgatum L.) is considered to be a valuable bioenergy crop with significant ... more Switchgrass (Panicum virgatum L.) is considered to be a valuable bioenergy crop with significant potential to sequester soil organic carbon (SOC). A study was conducted to evaluate soil carbon stocks within established switchgrass stands and nearby cultivated cropland on farms throughout the northern Great Plains and northern Cornbelt. Soil from 42 paired switchgrass/cropland sites throughout MN, ND, and SD was sampled to a depth of 120 cm and analyzed for soil carbon in depth increments of 0-5, 5-10, 10-20, 20-30, 30-60, 60-90, and 90-120 cm. SOC was greater (Po0:1) in switchgrass stands than cultivated cropland at 0-5, 30-60, and 60-90 cm. Differences in SOC between switchgrass stands and cultivated cropland were especially pronounced at deeper soil depths, where treatment differences were 7.74 and 4.35 Mg ha À1 for the 30-60 and 60-90 cm depths, respectively. Greater root biomass below 30 cm in switchgrass likely contributed to trends in SOC between switchgrass stands and cultivated cropland. Switchgrass appears to be effective at storing SOC not just near the soil surface, but also at depths below 30 cm where carbon is less susceptible to mineralization and loss.

Agronomy Journal, 2005

Calibration procedures and data used to parameterize a model, including model components that may... more Calibration procedures and data used to parameterize a model, including model components that may or may not have been addressed, are generally not well documented in modeling studies. A comprehensive description of the process and parameters used for calibrating the Root Zone Water Quality Model, v. 1.3.2004.213, is presented in this article. The model was calibrated to simulate tile drainage and leached nitrate under conventional tillage management practices for maize (Zea mays L.) production followed by a rye (Secale cereale L.) cover crop in Cecil soils (kaolinitic, thermic, Typic Kanhapludults), and for cotton (Gossypium hirsutum L.) development in the Georgia Piedmont. Tile drainage and nitrate leaching were simulated within 15% of the observed values in the calibrated maize scenarios with and without the soil macroporosity option. Simulated and observed tile drainage and leached nitrate were not significantly different, and the simulated values were not significantly differen...

Agronomy Journal, 2005

2004), will be greatly enhanced by effective information about the dynamics of fine root growth a... more 2004), will be greatly enhanced by effective information about the dynamics of fine root growth and dependent Study of root growth is important for understanding C flow through rhizosphere biology. Another area of application for plants to the soil and for modeling plant-soil interactions. Fine root growth can be observed through minirhizotrons (MRs), tubes installed fine root growth information is in soil and crop managein the field. We compared the use of fixed-wall (F-wall) MRs, 5.6 cm ment. For example, Merrill et al. (1996) have linked the in diam., and pressurized-wall (P-wall) MRs, 9.6 cm in diam., with effects of conservation tillage management on wheat an inner cylinder and an outer wall of plastic sheeting kept under growth through MR measurement of fine root growth. constant air pressure. Root growth was measured with a micro-video A general model of plant-soil interactions for undercamera for 3 yr in eight crop species growing on Pachic Haplustoll soil: standing the effects of crop-soil management on the canola, Brassica rapa L.; crambe, Crambe abysinnica Hochst. ex R.E.

Agronomy Journal, 2007

Field research was conducted to determine the influence of crop and crop sequencing on crop resid... more Field research was conducted to determine the influence of crop and crop sequencing on crop residue coverage of soil with 10 crops [buckwheat (Fagopyrum esculentum Moench), canola (Brassica napus L.), chickpea (Cicer arietinum L.), corn (Zea mays L.), dry pea (Pisum sativum L.), grain sorghum [Sorghum bicolor (L.) Moench], lentil (Lens culinaris Medik.), oil seed sunflower (Helianthus annuus L.), proso millet (Panicum miliaceum L.), and hard red spring wheat (Triticum aestivum L.)]. Crop residue production was obtained. Crop residue coverage of the soil surface was measured with a transect technique at the time of seeding spring wheat. Crop residue coverage varied and was more clearly associated with the second-year crop than with the first-year crop of a 2-yr crop sequence. Crop sequences composed of spring wheat, proso millet, and grain sorghum had higher crop residue coverage compared with sequences composed of the other crops. When these three crops and three crops that provide lower crop residue coverage of soil the subsequent year (lentil, chickpea, and sunflower) were analyzed as a subset to compare various sequences of crops providing a range of residue coverage, for example, lower (first yr)/lower (second yr), the surface residue coverage ranged from 65% for the lower/lower combination to 93% for the higher/ higher combination in 2004 and from 56 to 94% in 2005, respectively. A producer operating on more fragile soil and concerned about reducing soil erosion hazards would be advised to grow crops that provide higher residue coverage in the year before crops that provide lower residue coverage.

Agronomy Journal, 2007

Crop sequence is an important management practice that may lower the risk for leaf spot diseases ... more Crop sequence is an important management practice that may lower the risk for leaf spot diseases of spring wheat (Triticum aestivum L.). Field research was conducted near Mandan, ND, to determine the impact of crop sequences on leaf spot diseases of hard red spring wheat early in the growing season. Spring wheat was evaluated for disease severity following crop sequence combinations of 10 crops [buckwheat (Fagopyrum esculentum Moench), canola (Brassica napus L.), chickpea (Cicer arietinum L.), corn (Zea mays L.), dry pea (Pisum sativum L.), grain sorghum [Sorghum bicolor (L.) Moench], lentil (Lens culinaris Medik.), oil seed sunflower (Helianthus annuus L.), proso millet (Panicum miliaceum L.), and hard red spring wheat). Spring wheat leaves with distinct lesions were collected for determination of lesion number and percentage necrosis data, which were used to estimate leaf spot disease severity. Pyrenophora tritici-repentis (Died.) Drechs., the cause of tan spot, and Phaeosphaeria nodorum (E. Mu ¨ller) Hedjaroude, the cause of Stagonospora nodorum blotch, were the major leaf spot diseases and consistently present throughout the growing season. The frequency of isolation following alternative crops was generally lower compared with spring wheat following wheat. Leaf spot diseases on spring wheat were impacted by crop sequencing. Spring wheat following crop sequences with alternative crops for 1 or 2 yr had lower levels of disease severity compared with a continuous spring wheat treatment early in the growing season. Disease severity was apparently not related to the percentage of crop residue coverage on the soil surface associated with various crop sequence combinations. New alternative crops preceding spring wheat reduce levels of leaf spot diseases.

Dynamic Cropping Systems

Agronomy Journal, 2002

ABSTRACT Future trends in population growth, energy use, climate change, and globalization will c... more ABSTRACT Future trends in population growth, energy use, climate change, and globalization will challenge agriculturists to develop innovative production systems that are highly productive and environmentally sound. Furthermore, future agricultural production systems must possess an inherent capacity to adapt to change to be sustainable. Given this context, adoption of dynamic cropping systems is proposed to meet multiple agronomic and environmental objectives through the enhancement of management adaptability to externalities. Dynamic cropping systems are a form of agricultural production that relies on an annual strategy to optimize the outcome of (i) production, (ii) economic, and (iii) resource conservation goals using ecologically-based management principles. Dynamic cropping systems are inherently complex, possessing larger crop portfolios and greater crop diversity and sequencing flexibility as compared with monoculture and fixed-sequence cropping systems. Greater crop diversity and sequencing flexibility within dynamic cropping systems may result in reduced weed and disease infestations, greater nutrient- and precipitation-use efficiency, decreased requirements of exogenous inputs, and lower production risk. The multiple interactions among management components of dynamic cropping systems demand greater management intensity than monoculture and fixed-sequence cropping systems. Further development of dynamic cropping systems is important for managing crop production systems in a sustainable manner. These systems can ultimately assist land managers to develop new and improved land-use strategies to the benefit of generations to come.

Evaluation of the upgraded spur model (spur2.4)

Ecological Modelling, 1999

spur (Simulation of Production and Utilization of Rangelands) is a grassland ecosystem simulation... more spur (Simulation of Production and Utilization of Rangelands) is a grassland ecosystem simulation model. spur2.4 integrates all previous versions of spur. The changes from spur91 make the model more applicable to the southern Great Plains. The forage submodel from spur2 predicts forage intake and diet selection by grazing herbivores, and the cow-calf submodel from spur2 simulates all individuals in a herd for their full life cycle, based on defined genetic traits. The soil organic matter submodel from century was added to improve soil carbon and nitrogen cycling. spur2.4 output is compared with observed values from the Texas Experimental Ranch, Throckmorton, Texas. The changes made in creating spur2.4 have considerably improved the utility and accuracy of the spur model for north Texas. Soil moisture predictions are improved (spur91 is 137% and spur2.4 is 106% of observed, R=0.79–0.86), but run-off is still not adequate (R=0.65–0.76) and monthly evaporation is lower (spur91 is 94% and spur2.4 is 95%) than observed. Soil carbon level predictions by the century submodel are within range of the data, and output is stable over the simulation period. Predictions of individual plant species productivity compared with observed data are improved with spur2.4 (R=0.79–0.98). Between-season plant growth and long-term persistence are simulated well. The addition of the century soil organic matter submodel increased nitrogen level predictions resulting in more accurate predictions of animal weight gain. Steer weight gains are typical for north Texas. Simulation of cow-calf mass was good (R>0.98) as was production per hectare and per cow. The addition of the cow-calf model increases the utility of the model. The paper identifies portions of the model that need further validation and field research to improve model utility and credibility for use in natural resource management.

assessing the impact of management practices on multiple agroecosystem functions.

Journal of Range Management, 2002

Rangeland plant productivity and species composition are affected by moisture availability and gr... more Rangeland plant productivity and species composition are affected by moisture availability and grazing intensity. We examined warm-and cool-season grass productivity and relative dis-

Advances in Agroecology, 2009