bluuebunny/crossref_metadata_2025 huggingface dataset:
Ecological consequences of global climate change for freshwater ecosystems in South Africa
Authors: Dallas Helen F. , Rivers-Moore Nicholas
Published: May 2014

Freshwater resources in South Africa are under severe pressure from existing anthropogenic impacts and global climate change is likely to exacerbate this stress. This review outlines the abiotic drivers of climate change, focusing on predicted changes in temperature and precipitation. The consequences of global climate change for freshwater ecosystems are reviewed, with effects grouped into those related to water quantity, water quality, habitat and aquatic biological assemblages. Several guiding principles aimed at minimising the potential impact of climate change on freshwater ecosystems are discussed. These guidelines include those focused on water quantity and the maintenance of appropriate environmental flows, integration of global climate change into water quality management, conservation planning for freshwater biodiversity, the promotion of ecosystem resilience, and extending climate change science into policy and public discourse. Proactive assessment and monitoring are seen as key as these will allow for the identification of ecological triggers and thresholds, including thresholds of vulnerability, which may be used to monitor and inform decisions, as well as to improve the ability to forecast based on this knowledge.
Fragmentation and dewatering transform Great Plains stream fish communities
Authors: Perkin Joshuah S. , Gido Keith B. , Cooper Arthur R. , Turner Thomas F. , Osborne Megan J. , Johnson Eric R. , Mayes Kevin B.
Published: May 2014

Biodiversity in stream networks is threatened globally by interactions between habitat fragmentation and altered hydrologic regimes. In the Great Plains of North America, stream networks are fragmented by >19 000 anthropogenic barriers, and flow regimes are altered by surface water retention and groundwater extraction. We documented the distribution of anthropogenic barriers and dry stream segments in five basins covering the central Great Plains to assess effects of broad‐scale environmental change on stream fish community structure and distribution of reproductive guilds. We used an information‐theoretic approach to rank competing models in which fragmentation, discharge magnitude, and percentage of time streams had zero flow (a measure of desiccation) were included to predict effects of environmental alterations on the distribution of fishes belonging to different reproductive guilds. Fragmentation caused by anthropogenic barriers was most common in the eastern Great Plains, but stream desiccation became more common to the west, where rivers are underlain by the depleted (i.e., extraction > recharge) High Plains Aquifer. Longitudinal gradients in fragmentation and desiccation contributed to spatial shifts in community structure from taxonomically and functionally diverse communities dominated by pelagic reproductive guilds where fragmentation and desiccation were least, to homogenized communities dominated by benthic guilds where fragmentation and desiccation were common. Modeling results revealed these shifts were primarily associated with decline of pelagic reproductive guilds, notably small‐bodied pelagophilic and lithopelagophilic fishes that declined in association with decreased fragment length and increased number of days with zero flow. Graph theory combined with a barrier prioritization approach revealed specific fragments that could be reconnected to allow fishes within these guilds to colonize currently unoccupied fragments with the mitigation or removal of small dams (<10 m height). These findings are useful for natural resource managers charged with halting or reversing the prevailing pattern of declining fish diversity in the Great Plains. Our study represents one of the most comprehensive assessments of fish diversity responses to broad‐scale environmental change in the Great Plains and provides a conservation strategy for addressing the simultaneous contributions of fragmentation and flow alteration to the global freshwater biodiversity crisis.
Evaluation of Yield‐Based Drought Tolerance Indices for Screening Safflower Genotypes
Authors: Bahrami Forouzan , Arzani Ahmad , Karimi Vahid
Published: May 2014

Drought tolerance is not often considered an independent trait by plant breeders because the collective result of many traits of a plant with positive or negative interactions may be fairly general and polygenic in nature. The objective of this study was to evaluate six drought tolerance indices, namely the stress susceptibility index (SSI), yield stability index (YSI), tolerance index (TOL), mean productivity (MP), geometric mean productivity (GMP), and stress tolerance index (STI), to be used in screening safflower (Carthamus tinctorius L.) genotypes. For this purpose, 64 genotypes were grown during two growing seasons (2011–2012) under both normal and drought‐stress field conditions at the Research Farm of Isfahan University of Technology located at Lavark, Najaf‐Abad, Iran. The drought tolerance indices were calculated based on seed yield under drought stress and nonstress conditions. Results of combined analysis of variance showed the significant influences of drought stress on seed yield as well as significant differences among genotypes for seed yield and the indices. Results of calculated correlation coefficients and multivariate analyses showed that GMP and STI indices were able to discriminate between drought‐sensitive and ‐tolerant safflower genotypes. Cluster analysis using the drought‐tolerance indices divided the 64 genotypes into tolerant and susceptible groups. Based on multivariate analyses using the indices singly or in combinations, it was possible to identify the most yield‐stable genotypes across the environments. Overall, we concluded that GMP and STI indices can be efficiently exploited not only to screen drought tolerance but also to identify superior genotypes for both stress and nonstress field conditions in safflower.
Iron Chelates Alleviate Iron Chlorosis in Soybean on High pH Soils
Authors: Gamble A. V. , Howe J. A. , Delaney D. , van Santen E. , Yates R.
Published: May 2014

High pH soils frequently lead to iron deficiency chlorosis (IDC) in soybean [Glycine max (L.) Merr.]. As a result, yields for soybean are often reduced. Studies in the north‐central United States have shown improvements in grain yield after applying Fe chelates on calcareous soils, but this practice has not been evaluated in a southern climate. Two sites within the Blackbelt region of Alabama were evaluated for response to Fe‐EDDHA, Fe‐Citrate, and FeSO4 for their effect on yield and chlorosis in 2010, 2011, and 2012. Treatments were applied in‐furrow at planting, as a foliar spray at the V3 growth stage, or as a split‐application. Remote sensing, relative chlorophyll meter readings, and visual chlorosis scores (VCS) were assessed as methods for identifying degree of Fe chlorosis. At the location where IDC was most pronounced, all treatments of Fe‐EDDHA were effective at reducing VCS ratings when applied in‐furrow at planting; however, chlorosis evaluation through remote sensing and relative chlorophyll readings was not able to detect improvements in chlorosis measured with VCS. Treatments of Fe‐EDDHA at 4.5 kg product ha−1 increased yield whether applied as an in‐furrow at planting treatment or as a split application at planting and at V3 growth stage as a foliar spray. Treatments of Fe‐Citrate and FeSO4 did not improve yield as applied in this study. Results suggest that Fe‐EDDHA can be used in southern climates as a strategy to overcome IDC yield limitations.
Concurrent Improvement in Maize Yield and Nitrogen Use Efficiency with Integrated Agronomic Management Strategies
Authors: Wang Zhigang , Gao Julin , Ma B.L.
Published: May 2014

Low nitrogen use efficiency (NUE) and productivity with excessive use of N fertilizer in maize (Zea mays L.) is a common issue for smallholder farm systems. A 2‐yr field study was conducted to assess the impacts of integrated agronomic management strategies (MT) on pre‐ and post‐silking N uptake, dry matter (DM) production dynamics, and their relationships to yield and NUE components. Three MTs were compared with the regional conventional farming practices (FP). We found that biomass yields differed significantly with similar harvest index (HI) among the MT treatments. While OPT‐1 produced 21% greater DM but only 4% greater grain yield, OPT‐2 had 27% higher yield, and 200% greater NUE, compared to FP. Our results showed the possibility of simultaneously achieving high yield and high NUE with optimized MT. In OPT‐2, 13% greater DM production and 12% more N uptake after anthesis contributed 5% more to grain yield and 18% more to grain N. In HY, excessive N input did not improve the stay‐green trait nor did it enhance grain yield. These results imply a better balance between improving total biomass and achieving more DM accumulation in the post‐silking period with gradually optimized agronomic management practices than other MT. The enhanced NUE observed in OPT‐2 primarily originated from the improved N recovery efficiency, which was associated with larger root biomass at silking and greater post‐silking N uptake. Further NUE improvement in maize could be anticipated through enhanced N internal efficiency by balancing DM and N accumulation between vegetative and reproductive periods.
Implications of Tall Fescue for Inter‐Row Water Dynamics in a Vineyard
Authors: Holland S. , Howard A. , Heitman J. L. , Sauer T. J. , Giese W. , Sutton T. B. , Agam N. , Ben-Gal A. , Havlin J.
Published: May 2014

Vineyards in the southeastern United States face challenges including poor internal soil drainage, high precipitation, and warm temperatures. This environment causes elevated humidity, creating ideal conditions for fungal diseases. Maintaining tall fescue (Schedonorus arundinaceus Shreb) and resident vegetation ground cover in vineyard inter‐rows is a common cultural practice in the region, believed to benefit grape (Vitis vinifera L.) production by increasing competition for soil water and thereby favorably reducing vine vegetative growth. We hypothesized that, although inter‐row fescue may reduce soil water availability, it may also increase humidity within the vineyard. Our objectives were to assess surface vapor flux from two inter‐row treatments (bare soil and tall fescue) and to determine any corresponding effects on soil water content and humidity within the inter‐row. Surface vapor flux, soil water content, and vapor pressure (30 cm height aboveground) were measured in inter‐rows subjected to each treatment. Observed surface vapor flux for fescue inter‐row exceeded that of bare soil by a daily average of 1.1 mm during the grape growing season. Despite fescue inter‐row evapotranspiration (ET), soil water depletion was insufficient to produce stress in the vines. Fescue inter‐row vapor pressure increased compared to bare soil inter‐rows by an average of 2% (P < 0.09) during the growing season. Data suggest that fescue ET may increase inter‐row humidity in warm, humid environments, while providing only modest influence on soil water availability. Additional work including increased plot size to accommodate fetch for microclimate measurements, and biological assessment of humidity implications for disease is warranted.
A Review of Sports Turf Research Techniques Related to Playability and Safety Standards
Authors: Aldahir P. C. F. , McElroy J. S.
Published: May 2014

Sports fields have evolved in design, construction, and maintenance toward complex multiuse venues that host several different types of events. Low‐end sports fields such as public fields, parks, and recreation fields often suffer from limited care and excessive wear. High‐end fields suffer from problems of an altered microenvironment due to modern trends in high‐capacity stadia designs and from increasing wear caused by nonsporting and sporting events. Regardless, sports fields must obey a determined sport's regulations, offering adequate playability and providing a safe playing surface for the players. An aesthetically well‐presented sports field can also enhance the game experience for both players and viewers. Interactions between sports fields, players, and the ball are key to safety and playability. Such interactions are influenced by field construction, turfgrass choice, and maintenance practices. Poor quality sports fields can impair playability and increase injury potential, especially knee anterior cruciate ligament injuries, one of the most common injuries in sports. This review provides a compilation of research techniques attempting to quantify sports turf playability: wear and wear simulation, ball rebound resilience, coefficient of restitution, ball roll, spin and friction, friction and traction, and surface hardness; their relationship with player safety; and, finally, we present new ideas on the future and improvement of sports turf research.
Soil and Rainfall Factors Influencing Yields of a Dryland Cropping System in Colorado
Authors: Sherrod Lucretia A. , Ahuja Lajpat R. , Hansen Neil C. , Ascough James C. , Westfall Dwayne G. , Peterson Gary A.
Published: May 2014

The semiarid U.S. Great Plains experiences a large variation in crop yields due to variability in rainfall, soil, and other factors. We analyzed (24‐yr) yields from a no‐till rotation of winter wheat (Triticum aestivum L.)–corn (Zea mays L.) or sorghum [Sorghum bicolor (L.) Moench]–fallow at three sites, each with three soil types along a catena in Colorado. We investigated: (i) effects of soil organic carbon (SOC), length of slope (SL), and other soil properties on yields; and (ii) degree in which variability in annual yields are explained with water variables of rainfall during the fallow, vegetative and reproductive stages, and soil water at planting. Wheat and corn/sorghum yields were strongly related to soil properties (R2 = 0.84; 0.97, respectively). Wheat yield regression had only SOC as a significant variable, whereas corn/sorghum had SOC and SL. Water factors explained 37 to 73% of annual variability in wheat yields at the site by soil level, 19 to 63% when pooled over soils within sites, and 35 to 40% pooled over all. For corn, the corresponding percentages were 16 to 64%, 26 to 57%, and 40 to 45%, respectively. Fallow rain made the highest contribution to R2 in wheat whereas reproductive rain did for corn/sorghum. We conclude SOC is a stand‐in for long‐term effects of water availability on production, but other natural factors greatly influence the annual yield variability. Combining mean yields determined from soil properties with CV of pooled annual yields, we can estimate mean and standard deviation of yields.
Green Manure and Pendimethalin Impact on Oriental Sun‐Cured Tobacco
Authors: Travlos Ilias S. , Kanatas Panagiotis J. , Tsioros Stelios , Papastylianou Panayiota , Papatheohari Yolanda , Bilalis Dimitrios
Published: May 2014

Global markets for oriental sun‐cured tobacco (Nicotiana tabacum L.) have increased the number of fields planted to this crop in Greece and other countries. Field experiments were conducted in 2012 and 2013 to determine the influence of pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐ dintrobenzenamine] application and hoeing combined with the incorporation of pea (Pisum sativum L.) and vetch (Vicia sativa L.) as green manures on weed control and tobacco growth and yield. Plant height, number of leaves and total yield of tobacco were generally higher when pendimethalin was applied compared with cultivated tobacco. The absence of weed management resulted in lower growth and tobacco yields (on average 1221 and 1303 kg ha−1 for 2012 and 2013, respectively). Foxtail [Setaria verticillata (L.) P.Beauv.], barnyardgrass [Echinochloa crus‐galli (L.) Beauv.], fat‐hen (Chenopodium album L.), red‐root pigweed (Amaranthus retroflexus L.), and goathead (Tribulus terrestris L.) were adequately controlled by pendimethalin, while hoeing partially controlled weeds such as purple nutsedge (Cyperus rotundus L.). Incorporation of legumes increased both crop growth and yield. Nicotine content increased when green manures were used compared with untreated plots (values up to 3.62 and 3.16%, respectively). The adoption of the appropriate weed management method along with green manure can result in yields up to 2221 kg ha−1. The results of this study are essential for the development of an integrated crop and weed management strategy for oriental tobacco.
DSSAT Nitrogen Cycle Simulation of Cover Crop–Maize Rotations under Irrigated Mediterranean Conditions
Authors: Salmerón Montserrat , Cavero José , Isla Ramón , Porter Cheryl H. , Jones James W. , Boote Kenneth J.
Published: May 2014

The accurate simulation of N cycle in winter cover crop–maize rotations can help to study management practices aimed at reducing N leaching. A lysimeter and field experiment were used to calibrate and test the model under irrigated Mediterranean conditions. Thereafter, the model was used to evaluate the impact of cover crop–maize rotations on N leaching for a range of soil types and irrigation managements during a 14 yr rotation in La Violada watershed, Spain. The Decision Support System for Agrotechnology Transfer (DSSAT) v4.5.0.51 soil temperature subroutine overpredicted soil temperature, but this was improved when using a new EPIC‐based soil temperature subroutine that will be available in DSSAT v4.6. The model was accurate simulating total maize N content in maize after fallow and after different cover crops (root mean square error [RMSE] = 25 kg N ha−1), adequately simulated N leaching reductions with cover crops, and was less efficient simulating soil inorganic N. Overall, the DSSAT‐CENTURY model proved appropriate to simulate N cycle. DSSAT‐CERES‐Maize did not adequately simulate the observed yield reduction under N limitation in our high yielding conditions. Simulations in La Violada watershed indicate that N leaching in maize would still be high (44–98 kg N ha−1 yr−1) under an optimized water and N management. Cover crop–maize rotations could reduce N leaching by 31% while supplying similar N availability to maize than fallow–maize rotations. The model was useful to study several management scenarios that would be difficult to investigate under field conditions.
Photosystem II‐Inhibitors Play a Limited Role in Sweet Corn Response to 4‐Hydroxyphenyl Pyruvate Dioxygenase‐Inhibiting Herbicides
Authors: Choe Eunsoo , Williams Martin M. , Boydston Rick A. , Huber Joan L. , Huber Steven C. , Pataky Jerald K.
Published: May 2014

Postemergence (POST) application of 4‐hydroxyphenyl pyruvate dioxygenase (HPPD) inhibitors in combination with a photosystem II (PSII) inhibitor, such as atrazine [6‐chloro‐N‐ethyl‐N9‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], is common practice in sweet corn (Zea mays L.) production. Given the sensitivity of sweet corn to HPPD‐inhibiting herbicides, the objective of this work was to determine the extent to which cytochrome P450 (CYP) genotype and PSII‐inhibitors affect crop sensitivity to HPPD‐inhibiting herbicides. Greenhouse experiments were used to identify PSII‐inhibitors that were least injurious when combined with the HPPD‐inhibitors, mesotrione [2‐(4‐mesyl‐2‐nitrobenzoyl)‐3‐hydroxycylohex‐2‐enone], tembotrione {2‐[2‐chloro‐4‐(methylsulfonyl)‐3‐[(2,2,2‐trifluoroethoxy)methyl]benzoyl]‐1,3‐cyclohexanedione}, and topramezone {[3‐(4,5‐dihydro‐3‐isoxazolyl)‐2‐methyl‐4‐(methylsulfonyl)phenyl](5‐hydroxy‐1‐methyl‐1H‐pyrazol‐4‐yl)methanone}. Subsequently, HPPD‐inhibitors were tested individually with PSII‐inhibitors atrazine, or bentazon [3‐(1‐methylethyl)‐(1H)‐2,1,3‐benzothiadiazin‐4(3H)‐one2,2‐dioxide], or alone in field experiments on all three CYP genotypic classes; hybrids homozygous for mutant CYP alleles (cypcyp), hybrids homozygous for functional alleles (CYPCYP), and heterozygous hybrids (CYPcyp). Leaf bleaching within 1 wk of herbicide application increased when a PSII‐inhibitor was combined with an HPPD‐inhibitor; however, the relatively low level of injury was short‐lived. Tank mixing atrazine to mesotrione, tembotrione, or topramezone in sweet corn did not increase risk of yield loss compared to HPPD‐inhibitor applied alone. The synergistic effect on weed control between certain PSII‐ and HPPD‐inhibitor combinations reported previously does not hold true regarding sweet corn sensitivity to these herbicides. Among three HPPD‐inhibitors tested in sweet corn, topramezone was the safest, regardless of PSII combination. Mutant CYP alleles, namely CYPcyp and cypcyp hybrids, are the main cause of sweet corn sensitivity to mesotrione, tembotrione, and other CYP‐metabolized herbicides; therefore, breeding efforts to eliminate mutant CYP alleles should remain a high priority.
The Use of Reflectance Data for In‐Season Soybean Yield Prediction
Authors: Mourtzinis Spyridon , Rowntree Scott C. , Suhre Justin J. , Weidenbenner Nicholas H. , Wilson Eric W. , Davis Vince M. , Naeve Seth L. , Casteel Shaun N. , Diers Brian W. , Esker Paul D. , Specht James E. , Conley Shawn P.
Published: May 2014

Estimation of soybean [Glycine max (L.) Merr.] yield early in the growing season is an appealing idea for both, farmers and soybean‐related industries. Prior attempts to predict soybean yield have had limited success, especially when using information early in the growing season. The objective of this study was to evaluate the release date and maturity group (MG) of the cultivar, digital imaging, reflectance, and weather data during successive stages of crop development as explanatory variables in a soybean yield prediction model. The data were collected in the North Central (NC) United States at Arlington, WI (2010–2011), and Lafayette, IN (2011), using 59 MG II cultivars (released 1928–2008) at Wisconsin, and 57 MG III cultivars (released 1923–2007) at Indiana that were planted in performance trials on two planting dates (May and June). A second order polynomial regression analysis followed by ridge regression was used to develop the soybean yield prediction equation. The model accounted for 80% of the yield variability in the NC U.S. data set. An additional dataset not used in the calibration was used to conduct a validation test of the predictive performance of the model. The average difference between the fitted and actual yields in the validation test was 67 kg ha−1. Results from this study suggest that the use of cultivar release year, planting date, MG, near‐infrared (NIR), visible red (RED), and Red‐edge wavelength bands recorded at 77 d after planting, and weather data 30 d before and after the planting date can closely estimate soybean yields in the Midwest.
Kura Clover Living Mulch for Furrow‐Irrigated Corn in the Intermountain West
Authors: Pearson Calvin H. , Brummer Joe E. , Beahm Andrew T. , Hansen Neil C.
Published: May 2014

Kura clover (Trifolium ambiguum M. Bieb.) living mulches have been used successfully to produce corn (Zea mays L.) in the upper Midwest. A study was conducted at Fruita, CO (39.1500° N, 108.7167° W), to evaluate corn production in a kura clover living mulch system under furrow irrigation. Living mulch treatments were: (i) no‐till, (ii) no‐till with a pre‐plant herbicide application, and (iii) strip‐tillage. Nitrogen fertilization rates of 0, 84, and 168 kg N ha−1 were applied to living mulch plots and 0, 168, and 336 kg N ha−1 were applied to conventional corn plots. Grain yield was responsive to N rate with highest yields in kura clover living mulch plots occurring at 168 kg N ha−1 (10.1 and 10.8 Mg ha−1 in 2007 and 2008, respectively). The strip‐till treatment performed best in 2007, yielding 11.7 Mg ha−1 at 168 kg N ha−1, but did not differ from the no‐till with pre‐plant herbicide in 2008. Averaged across tillage treatments, kura clover biomass was highest (991 kg ha−1) when no N was applied and the difference in kura clover biomass was not significant between the 84 and 168 kg ha−1 N rates. There was no difference in kura clover production among suppression treatments (averaging 726 kg ha−1). Strip‐tillage at a 168 kg N ha−1 rate is a promising option for producing grain corn in a kura clover living mulch cropping system under furrow irrigation in the Intermountain West.
Yield Gap and Production Gap of Rainfed Winter Wheat in the Southern Great Plains
Authors: Patrignani Andres , Lollato Romulo P. , Ochsner Tyson E. , Godsey Chad B. , Edwards Jeff. T.
Published: May 2014

Since 1980, average wheat (Triticum aestivum L.) yields have remained nearly stagnant in the southern Great Plains (SGP) and stagnant in the state of Oklahoma. Yield stagnation can sometimes be attributed to a relatively small gap between current and potential yields, but the magnitude of the yield gap for this region has not been well quantified. The objective of this study was to determine the wheat yield and production gaps in Oklahoma at state and county levels. This involved estimation of attainable yield (Ya) using a frontier yield function and water‐limited potential yield (Yp) using estimated transpiration and transpiration efficiency. Yield gap and production gap relative to Ya and Yp were calculated using grain yields and harvested area for 19 counties. Current average yield (Yc) was 2.06 Mg ha−1 at the state level, well below the maximum recorded yield at the plot level of 6.59 Mg ha−1. The Yp of current wheat varieties is far above Yc in Oklahoma, and Yc represents 74% of Ya but only 30% of Yp at state level. For growing season rainfall (GSRF) amount <250 mm wheat yields were often water‐limited. However, average GSRF was 471 mm, and yield was typically limited by factors other than GSRF amount. Production exhibited greater temporal variability than yield, and production gap may be a better indicator than yield gap for regions with highest potential to increase production. Low yields and yield stagnation in Oklahoma cannot be attributed to a small remaining yield gap, nor to inadequate GSRF amount.
Cropping Sequence and Nitrogen Fertilization Impact on Surface Residue, Soil Carbon Sequestration, and Crop Yields
Authors: Sainju Upendra M.
Published: May 2014

To determine farm C credit and reduce global warming potential, information is needed on the effect of management practices on soil C storage. The effects of tillage, cropping sequence, and N fertilization were evaluated on dryland crop biomass, surface residue C, and soil organic carbon (SOC) at the 0‐ to 120‐cm depth in a Williams loam (fine‐loamy, mixed, superactive, frigid, Typic Argiustolls) and their relationships with grain yields from 2006 to 2011 in eastern Montana. Treatments were no‐till continuous malt barley (Hordeum vulgare L.) (NTCB), no‐till malt barley–pea (Pisum sativum L.) (NTB‐P), no‐till malt barley–fallow (NTB‐F), and conventional till malt barley–fallow (CTB‐F), each with 0, 40, 80, and 120 kg N ha−1. Annualized crop grain and biomass yields, surface residue amount, and C contents were greater in NTB‐P and NTCB than CTB‐F and NTB‐F and increased with increased N rates. At 0 to 5 and 5 to 10 cm, SOC was greater in NTB‐P than CTB‐F or NTCB with 40 kg N ha−1 and at 10 to 30 and 0 to 120 cm was greater in NTB‐P than NTCB with 120 kg N ha−1. Surface residue C and SOC were related with grain yield and C content (R2 = 0.21–0.55, P ≤ 0.10, n = 16). Greater amount of crop residue returned to the soil and turnover rate probably increased surface residue C, soil C storage, and crop yields in NTB‐P with 40 and 120 kg N ha−1 than the other treatments. Soil organic matter and crop yields can be enhanced by using NTB‐P with 40 kg N ha−1.
Achieving Water Security in Agriculture: The Human Factor
Authors: Morton Lois Wright
Published: May 2014

It is widely recognized that achieving water security will take substantive investments in hydrology, engineering, soil science, agronomy, and a wide variety of physical and natural sciences and technologies. Less understood is the human aspect, the social science of beliefs, values, human perceptions and decision‐making, social relationships, and social organization that intentionally and unintentionally construct, destroy, and reconstruct the water and land resources to which society is intimately linked. Addressing the complex issues of water security will require humans to acknowledge the threats to security and a willingness to give priority to assuring water quality, water availability, and water access to meet the needs of a growing world population and their economic engines. Soil–water–vegetation–climate–human relationships are central to maintaining and repairing the hydrological cycle necessary for fresh, safe, and abundant water supply. The current and future condition of our earth ecosystem is substantively dependent on individual and social decisions and policies associated with water. There is a need for (i) more coupled human‐natural science to understand these relationships, (ii) greater public participation in connecting scientific facts and social values, and (iii) a willingness to innovate and adapt water and land use decisions and policies as scientific understanding and values evolve.
Radiation Use Efficiency: Evaluation of Cropping and Management Systems
Authors: Hatfield Jerry L.
Published: May 2014

Capture of solar radiation by plant canopies and conversion of this energy into biomass or grain has been described as radiation use efficiency. Radiation use efficiency (RUE) has been developed as a function of biomass accumulation and intercepted photosynthetically active radiation (IPAR) by the canopy and evaluated under conditions not limiting to plant growth. This study was designed to evaluate RUE across a number of corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] experiments in central Iowa with various tillage and management inputs to determine how RUE changed as a function of agronomic management. In these studies, IPAR was derived through the use of a normalized difference vegetation index, which is a surrogate for the photosynthetically active radiation canopy interception term, and total canopy biomass was measured at five times during the growing season from the early vegetative stage through maturity. Grain yields were obtained from each plot with both hand‐ harvested and combine samples. Values for RUE showed a linear relationship between biomass and IPAR for the entire growing season, with the better fit when the relationship was confined to the vegetative development period. There were differences among years, with management and tillage systems affecting RUE values through the differences in biomass or grain yield. Grain yield relationships to IPAR showed more variation than total biomass, with yearly differences evident in the amount of IPAR during the grain‐filling period suggesting that the length of the grain‐filling period is a dominant factor in grain yield. Application of RUE to field‐scale observations will provide a method of assessing where crop productivity is limited.
Rethinking the Analysis of Non‐Normal Data in Plant and Soil Science
Authors: Stroup Walter W.
Published: May 2014

The introduction of high‐quality, useable generalized linear mixed model (GLMM) software in the mid‐2000s changed the conversation regarding the analysis of non‐normal data from designed experiments. For well over half a century, the reigning paradigm called for using analysis of variance (ANOVA), either assuming approximate normality of the original data or applying a variance‐stabilizing transformation. The appearance of GLMMs creates a dilemma. The ANOVA‐based analyses and GLMM‐based analyses often yield mutually contradictory results. What results should a researcher report, and how should the choice be justified? If GLMM‐based analysis is preferred—and there is increasing evidence that this is the case—approaches to data analysis ingrained while learning ANOVA must be unlearned and relearned. The basic issues associated with the analysis of non‐normal data are reviewed here, the thought processes required for GLMMs and how they differ from traditional ANOVA are introduced, and three examples are presented, giving an overview of GLMM‐based analysis. The three examples include discussions of what is known to date about the relative merits of GLMM‐ and ANOVA‐based analysis of non‐normal data.
The Discovery of Natural Miscanthus Accessions Related to Miscanthus × giganteus Using Chloroplast DNA
Authors: Feng X.P. , Lourgant K. , Castric V. , Saumitou‐Laprade P. , Zheng B.S. , Jiang D. , Brancourt‐Hulmel M.
Published: May 2014

It is essential to enlarge the pool of varieties of the biomass crop Miscanthus to support the increase in its cultivation area, and several natural species from eastern or southeastern Asia could be of interest. Our main study objectives were: (i) to investigate the frequency spectrum of the haplotypes of natural Chinese accessions and their geographic distribution in China, and (ii) to identify the Chinese chloroplast genomes related to the maternal genomes of cultivated European varieties. We studied 21 clones cultivated in Europe and 44 wild Chinese accessions from 10 Chinese provinces covering four species of Miscanthus: M. sacchariflorus (Maxim.) Hack., M. sinensis Andersson, M. floridulus (Labill.) Warb. ex K. Schum. & Lauterb., and M. × giganteus J.M. Greef & Deuter ex Hodkinson & Renvoize. We used chloroplast DNA from sugarcane (Saccharum officinarum L.) due to its taxonomic relationship with Miscanthus and designed primers using the large single‐copy region of the chloroplast genome. The polymorphisms belonged to noncoding and coding regions and were substitutions that corresponded to single nucleotide polymorphisms. Haplotypes were then determined, enabling the investigation of the haplotype frequency spectrum and the geographic distribution of the accessions in China. Furthermore, the maternal genome of M. × giganteus appears related to some Chinese M. sacchariflorus clones. The corresponding geographic native area of these wild clones could be of interest to enlarge the genetic variability for the breeding of new interspecific hybrids.
A Prioritized Inventory of Crop Wild Relatives and Wild Harvested Plants of Italy
Authors: Landucci Flavia , Panella Lorenzo , Lucarini Domenico , Gigante Daniela , Donnini Domizia , Kell Shelagh , Maxted Nigel , Venanzoni Roberto , Negri Valeria
Published: May 2014

The aim of this study was to construct a solid basis for developing a crop wild relatives (CWR) and wild harvested plants (WHP) conservation strategy at the European and national levels. To this end we (i) worked out an annotated and synonymized Working Database of the Italian Vascular Plants, (ii) worked out a full CWR–WHP checklist for Italy, (iii) worked out a prioritized CWR and WHP inventory, (iv) identified native taxa with an ascertained utility for breeding, and (v) on the basis of a gap analysis case study on two Brassica taxa, outlined the first steps to be taken immediately to develop their in situ and ex situ conservation strategy. The Working Database of the Italian Vascular Plants includes a total of 11,710 taxa. Of those, 92.0% form the CWR–WHP checklist. On the basis of the importance of the related crops, their status, and their need of protection and/or monitoring, 1118 taxa were prioritized. Of these, 129 taxa deserve the highest priority in planning a conservation strategy, including 16 that currently have a practical use in breeding. The case study showed that little is still known about relic CWR populations and that not all of them are adequately protected in situ and ex situ. Since information on their abundance, location, distribution, ecological conditions, census, and current conservation is lacking, initiatives should be put into action immediately for developing a national and European conservation strategy.
Brazilian Spring Wheat Homogeneous Adaptation Regions can be Dissected in Major Megaenvironments
Authors: Munaro Lucas Berger , Benin Giovani , Marchioro Volmir Sérgio , de Assis Franco Francisco , Silva Raphael Rossi , da Silva Cristiano Lemes , Beche Eduardo
Published: May 2014

The objectives of this study were to investigate the pattern of genotype environment interaction and identify megaenvironments (ME), essential test locations, and suitable genotypes for each ME. The genotype plus genotype by environment interaction (GGE) biplot and additive main effects and multiplicative interaction analysis (AMMI) were used to demonstrate the potential of using a graphical biplot to analyze the genotype by environment interaction (GEI) in data of multienvironment trials (MET). These trials of the Central Cooperative Agricultural Research (COODETEC) evaluated 36 advanced breeding lines and 27 check cultivars for 3 years (2008–2010) at 12 test locations. Yield data were analyzed using the genotype plus GGE and AMMI biplot methods. The test environments were classified into two ME (i.e. ME1: Castro, Guarapuava, Não‐Me‐Toque, Abelardo Luz, and Cachoeira do Sul; and ME2: Campo Mourão, Dourados, Palmital, Palotina, Ponta Porã, and Rolândia. In ME1, the locations Guarapuava, Cachoeira do Sul, and Abelardo Luz were classified as ideal, while in ME2, Ponta Porã, Dourados and Palotina were close to ideal. Guarapuava was the essential test location in ME1; however the identification of an essential test location in ME2 was unclear. Superior cultivars and advanced lines were identified in both ME that could be valuable for spring wheat (Triticum aestivum L.) improvement or cultivars released.
Genetic Mapping Using Genotyping‐by‐Sequencing in the Clonally Propagated Cassava
Authors: Rabbi Ismail , Hamblin Martha , Gedil Melaku , Kulakow Peter , Ferguson Morag , Ikpan Andrew S. , Ly Delphine , Jannink Jean‐Luc
Published: May 2014

Cassava (Manihot esculenta L.) is one of the most important food crops in the tropics, but yields are far below their potential. The gene pool of cassava contains natural genetic diversity relevant to many important breeding goals, but breeding progress has been slow, partly because of insufficient genomic resources. As a first step toward implementing genomewide genetic studies that will facilitate rapid genetic gain through breeding, we genotyped‐by‐sequencing a set of 182 full‐sibs population of cassava that segregated in several traits: resistance to the cassava mosaic disease (CMD) and yield under CMD pressure; increased carotenoid content in storage roots; color of stem exterior and anthocyanin pigmentation in the petioles, inner root skin, and apical leaves. Employing a rare‐cutting restriction enzyme, PstI, in a genotyping‐by‐sequencing (GBS) library preparation, we obtained 2478 segregating single nucleotide polymorphisms (SNPs), of which 1257 passed standard filtering for missing genotypes and deviation from expected genotypic frequencies. We mapped 772 SNPs across 19 linkage groups and anchored 313 unique scaffolds from the version 4.1 of the cassava genome assembly. Most of the studied morphological traits as well as resistance to CMD and root carotenoid content showed qualitative inheritance. As expected, quantitative trait loci analysis for these traits revealed single loci surrounded by small confidence intervals. Yield under CMD was associated with the CMD resistance locus. We show that GBS is a powerful genotyping tool that provides a sufficient number of markers for unraveling the genetic architecture of Mendelian traits in cassava in addition to the development of a robust genetic map that can help anchor unassembled genomic scaffolds.
Generation Means Analysis for Fiber Elongation in Upland Cotton
Authors: Ng E.‐H. , Smith C. W. , Hequet E. , Hague S. , Dever J.
Published: May 2014

Each bale (218 kg) of upland cotton (Gossypium hirsutum L.) produced in the United States is graded on the basis of several fiber quality traits, namely, strength, upper‐half mean length, micronaire, uniformity index, color, and trash content. To promote production of high‐quality cotton, producers are given monetary incentives to meet and exceed market standards. Quantitative inheritance of these quality traits have been the primary research focus of many cotton researchers worldwide in an effort to better understand the genetics governing these traits. Increased fiber bundle elongation (ability to stretch without breaking) has not been considered because of its weak but negative correlation with fiber bundle strength. However, current literature suggests that elongation, along with fiber strength, contributes to yarn tenacity. To better understand the genetics of fiber elongation, six distinctive upland families derived from four parental genotypes representative of elongation variation within modern cotton germplasm pools were analyzed using generation means analysis (GMA). Additive gene effects were predominant over dominance gene effects, and nonallelic gene interactions were minimal for elongation. The large numbers of effective factors identified suggests that parents used in the GMA are carrying different genetic materials or loci for elongation. Considerable gains in elongation may be achieved by selectively crossing some of these materials in a pure‐line breeding scheme while holding other important fiber traits constant.
Genetics, Breeding, and Marker‐Assisted Selection for Verticillium Wilt Resistance in Cotton
Authors: Zhang Jinfa , Fang Hui , Zhou Huiping , Sanogo Soum , Ma Zhiying
Published: May 2014

Verticillium wilt (VW), caused by the soil‐borne fungus Verticillium dahliae Kleb., is one of the most destructive diseases in Upland cotton (Gossypium hirsutum L.) production in the U.S. and worldwide. Development of VW‐resistant cultivars remains the only economic option for controlling the disease. The objective of this review was to summarize the progress in screening methods, resistance sources, and genetics, quantitative trait locus (QTL) mapping, marker‐assisted selection (MAS) and breeding for VW resistance in cotton. Even though Gossypium barbadense L. carries high levels of resistance, its resistance has not been transferred into commercial Upland cultivars. Many Acala cotton cultivars developed in New Mexico and California between the 1940s and the 1990s, and some commercial transgenic cultivars are tolerant or moderately resistant to VW. However, due to difficulties in achieving consistent and uniform inoculation and infection with V. dahliae, both qualitative and quantitative inheritance of VW resistance have been reported in numerous studies for resistant G. barbadense and Upland genotypes. Several QTL analyses have shown the existence of VW resistance QTLs on almost all the tetraploid cotton chromosomes; however, QTLs have most frequently been detected on c5, c7, c8, c11, c16, c17, c19, c21, c23, c24, and c26. This has led to MAS for progeny with favorable QTL alleles for VW resistance in several experiments. Phenotypic selection for VW resistance has been inefficient, while the effectiveness and efficiency of MAS remain to be validated. There is an urgent need for the development of better plant inoculation and screening methods, and for more molecular mapping studies to discern the genetic basis of VW resistance in cotton.
Carbohydrate and Lipid Dynamics in Wheat Crown Tissue in Response to Mild Freeze–Thaw Treatments
Authors: Skinner D. Z. , Bellinger B. S. , Hansen J. C. , Kennedy A. C.
Published: May 2014

Freezing tolerance resulting from cold hardening is critical to survival of fall‐seeded winter wheat. Exposure of winter wheat plants to cycles of freeze–thaw at temperatures just below, and just above freezing results in incremental improvements of freezing tolerance. Changes in the concentrations of carbohydrates in the cellular fluids of wheat crowns, and of lipids extracted from wheat crown tissue, were quantified following exposure to 24 h freeze(s) at –3°C, with or without a following thaw of 24 h at 3°C. Concentrations of simple sugars, and sucrose and related carbohydrates, increased in the first 24 h of exposure to –3°C, and continued to increase whether the plants were then exposed to a further 24 h at –3°C or were exposed to 3°C for 24 h. The concentration of fructans decreased during the first 24 h of exposure to –3°C, and continued to decrease if the plants were exposed to 3°C for 24 h, but increased if the plants were exposed to a continuous –3°C for 48 h. The frequencies of occurrences of numerous lipid species changed with each 24 h temperature treatment, some consistent with the behavior of lipid signaling molecules. Carbohydrates and lipids in wheat crowns are actively restructured at subzero temperatures as the plants acquire greater freezing tolerance. Identifying plant lines especially able to effect this restructuring may enable the development of plant lines with improved freezing tolerance.
White Clover Inclusion within a Bermudagrass Lawn: Effects of Supplemental Nitrogen on Botanical Composition and Nitrogen Cycling
Authors: McCurdy James D. , McElroy J. Scott , Guertal Elizabeth A. , Wood C. Wesley
Published: May 2014

White clover (Trifolium repens L.) inclusion is a proposed means of increasing the sustainability of low‐maintenance turfgrass scenarios due to its ability to biologically fix N and transfer it to associated grasses. Little is known about white clover N contribution to maintained warm‐season turfgrass swards. A 3‐yr study was conducted to evaluate the effects of white clover inclusion within a hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] lawn. Supplemental N (0, 0.5, 1, 2, 4, and 8 g N m−2) was applied monthly, from April to August, to test the effects of supplemental N on biomass composition, N fixation, and N transfer. Mixed grass plus clover swards yielded higher clipping biomass than grass‐alone swards, which was evidence of enhanced bermudagrass growth due to biological N fixation. Likewise, grass biomass of mixed swards was increased relative to that of grass‐alone swards at supplemental N rates ≤10 g N m−2 yr−1 but was decreased at higher supplemental N rates. Nitrogen fixation was estimated to be 6.6 g m−2 yr−1 during the 3‐yr study, with an apparent increase in fixation as years progressed. Results indicate that N fixation was suppressed at the lower and upper extremes of supplemental N rates. Nitrogen transfer to the associated bermudagrass sward was estimated to be 24% during the latter 2 yr of the study. These results offer evidence of white clover utility when included within maintained warm‐season turfgrass scenarios.
The Effects of GM Technology on Maize Yield
Authors: Chavas Jean‐Paul , Shi Guanming , Lauer Joseph
Published: May 2014

In the United States, maize (Zea mays L.) farmers have adopted genetic‐modification technology rapidly since its first commercialization in 1996. By 2012, 88% of U.S. maize is planted with genetically modified (GM) hybrids. Our objective in the paper is to present an empirical analysis of the determinants of U.S. maize yield using experimental maize production data, with a focus on the interaction effects of GM technology, management, and risk. Genetic‐modification technology had a stronger impact on the lower end of maize yield distribution within a trial thereby reducing exposure to downside risk. A strong interaction exists between GM technology and crop rotations: GM reduces the adverse effects of maize–maize rotation on yield. As such, GM technology is found to be a substitute for crop rotation. Genetic‐modification technology increases the yield gains associated with higher planting density. This indicates that GM technology offers good prospects for future improvements in maize productivity.