bluuebunny/crossref_metadata_2025 huggingface dataset:
Corn, Sunflower, and Soybean Emergence Influenced by Soil Temperature and Soil Water Content
Authors: Helms Theodore C. , Deckard Edward L. , Gregoire Peter A.
Published: July 2010

The influence of soil temperature and initial soil water content on subsequent germination and emergence of corn (Zea mays L.), sunflower (Helianthus annuus L.), and soybean [Glycine max (L.) Merr.] needs to be understood. Previous research has not determined whether emergence of corn and sunflower is reduced by soil water content that is high enough for seed imbibition but too low for radicle emergence from the testa. Our objective was to evaluate corn, sunflower, and soybean emergence influenced by initial seed‐zone soil water content of 0.05, 0.07, and 0.09 kg kg−1 and soil drying at three day/night (17/8, 21/12, 25/16°C) soil temperature regimes as the number of days of soil water deficit and temperature stress increased. A factorial experiment with two replicates was conducted under controlled temperature conditions in an incubator. This experiment was conducted using a Glyndon silty clay loam (coarse‐silty, frigid Aeric Calciaquolls). Corn emergence was >85% at all three initial soil water contents and temperature regimes. Sunflower emergence increased from 59% at the low initial soil water content to 90% at the higher initial soil water content. Soybean emergence was 22% after stress was imposed by a 0.07 kg kg−1 initial soil water content (high enough for seed imbibition but too low for germination). If soil water content is sufficient to imbibe seeds of soybean and sunflower, but too low for germination during the 6 d after planting, producers may need to replant, especially when soil temperature is above 21/12°C.
Developing Guidelines for Replanting Grain Sorghum: I. Validation and Sensitivity Analysis of the SORKAM Sorghum Growth Model
Authors: Heiniger Ronnie W. , Vanderlip Richard L. , Welch Stephen M.
Published: July 2010

Sorghum [Sorghum bicolor (L.) Moench] producers often have difficulty determining when plant stands are low enough to merit replanting. Our objective was to use SORKAM, a sorghum growth model, to develop guidelines for replanting grain sorghum. A necessary first step is validation of the model over an extensive range of management and environmental factors. Validation was accomplished using 19 field data sets representing 11 yr and six Kansas locations. Several nonparametric tests were used to compare observed and simulated yields, yield components, and phenological dates. In addition, sensitivities of yield and yield components were determined in response to yearly climate, planting date, plant population, and maturity class changes. Model sensitivities were compared with sensitivities calculated from field data. While phenological predictions were adequate, SORKAM could capture only 27 to 79% of grain yield variability at the locations tested. Yield predictions from different plant populations within a planting date were particularly inaccurate. The validation and sensitivity analyses showed that the poor yield predictions were the result of improper computation of tiller number and faulty partitioning of biomass to caryopsis weight. Partitioning errors translocated enough assimilate from culm to grain to make yields essentially constant across populations within a planting date. To use SORKAM to generate replant guidelines, improvements must be made in modeling the relationships among yield components and the source‐sink relationship that determines caryopsis weight.
Early‐Maturing Soybean Cropping System: I. Yield Responses to Planting Date
Authors: Kane Mark V. , Steele Colleen C. , Grabau Larry J.
Published: July 2010

An early‐planted, early‐maturing soybean [Glycine max (L.) Merrill] cropping system has been quite successful across the southeastern USA. This cropping system was intended to use early planting to improve yield by avoiding late season drought stress. However, producers in this region use planting dates ranging from late April through late June. Our objective was to characterize the yield response of early‐maturing cultivars to environmental conditions over a range of planting dates. Field studies were conducted on a well‐drained Maury silt loam (fine, mixed, mesic Typic Paleudalf) in 1990 through 1993 using cultivars from Maturity Group (MG) 00 through IV planted in late April, mid‐May, early June, and late June each year. Modest moisture stress was observed over the years tested; however, temperatures during soybean growth stages depended strongly on planting dates. When averaged across years and cultivars, yields were similar for the first three planting dates. Best overall yields were obtained using the MG IV cultivar for late April and mid‐May planting; however, its advantage over MG II and III cultivars diminished for the early June planting date and disappeared for the late June planting date. Early‐maturing cultivars (MG 00 to I) were less likely to achieve competitive yield levels. Lower yields of early‐maturing cultivars for the late April planting date were associated with low temperatures during vegetative growth and with high temperatures during seedfill. In the absence of pronounced moisture stress, low or high temperatures may become the key environmental factors limiting yield. Early planting, a centerpiece of previous successful early‐maturing soybean cropping systems in the southeastern USA, appears to be less important under more favorable moisture conditions.
Early‐Maturing Soybean Cropping System: II. Growth and Development Responses to Environmental Conditions
Authors: Kane Mark V. , Steele Colleen C. , Grabau Larry J.
Published: July 2010

Production of early‐planted, early‐maturing soybean [Glycine max (L.) Merrill] cultivars has gained popularity in the southeastern USA in recent years, primarily as a drought‐avoidance mechanism. In seasons with adequate rainfall, however, early planting of such cultivars may not be essential for competitive yields. Our objective was to identify key environmental constraints to the growth and development of early‐maturing soybean in the southern region. Soybean cultivars from Maturity Groups (MG) 00 through IV were planted in late April, mid‐May, early June, and late June in 1990 through 1993 in 0.38‐m rows on a well‐drained Maury silt loam soil (fine, mixed, mesic Typic Paleudalf). Canopy closure, plant height, and plant mass per unit area were recorded at both R1 and R5. In addition, crop growth rate from R1 to R5 was calculated. Cool vegetative‐stage temperatures suppressed vegetative growth, particularly of early‐maturing cultivars and for early planting dates. Crop growth rate during pod‐set was not consistently associated with yield. Canopy closure at R1 of early‐maturing cultivars was more responsive to delayed planting than was that of later maturing cultivars. Across years and planting dates, canopy closure at R5 of MG 00 to I cultivars generally fell below 90%, while that of MG II to IV cultivars generally exceeded 90%. Early planting may be a disadvantage for early‐maturing cultivars in seasons with favorable rainfall patterns, particularly if canopy development is inhibited by cool temperatures during vegetative growth. If moisture is not limiting, delayed planting of early‐maturing cultivars may be advantageous.
Agronomic Response of Winter Rapeseed to Rate and Date of Seeding
Authors: Moore Mary K. , Guy Stephen O.
Published: July 2010

In northern Idaho, winter rapeseed (Brassica napus L.) usually is seeded on summer fallow in early to mid‐August at 4.5 to 13.5 kg seed ha−1. A 2‐yr study was conducted at Moscow, ID, to quantify crop performance as influenced by date of seeding and seeding rate. In the 1991–1992 and 1992–1993 growing seasons, high‐erucic‐acid winter rapeseed cultivars, ‘Dwarf Essex’ and ‘Bridger’, were seeded on four dates at 2‐wk intervals from early August to mid‐September at four seeding rates from 0.9 to 2.7 × 106 seeds ha−1. Greatest yield for the four dates ranged from 1974 to 2675 kg ha−1. Optimum spring plant stands for attaining those yields were between 61 and 112 plants m−2, obtained at different seeding rates, depending on the date of seeding. The lowest seeding rates (0.9 and 1.5 × 106 seeds ha−1) produced optimum spring plant stands for the mid‐August and early September seeding. Higher seeding rates in early August and mid‐September were necessary to achieve optimum spring plant stands.
An Empirical Model of Diurnal Temperature Patterns
Authors: Sadler E. John , Schroll Ronald W.
Published: July 2010

Air temperature is a key driving factor in many crop growth models. Hourly air temperature data required for input are often not available and must be estimated from daily extremes. Several methods to model diurnal patterns exist; all are arbitrary functions of time during the day, chosen to match the daily pattern. Of all possible mathematical shapes, it would be preferable to use the one generated by the data themselves. Thus, our objective was to develop an empirical model to reconstruct the diurnal air temperature curve from measured daily extremes. As usual, temperature was normalized to range from 0 to 1 at the daily extremes. However, we also normalized time, to reduce seasonal variation in the shape of the temperature pattern. Calibration consisted of developing the cumulative distribution function of normalized temperature for a year's data, fitting a beta distribution to the data, and evaluating the 50th percentile, all as a function of time. The resulting vectors of normalized time and air temperature were used to generate diurnal patterns from daily extremes. The model was calibrated with one year's data for each of 14 sites across the USA, and tested for additional years at each site. For the total 32 site‐years, annual mean r1 ranged from 0.47 to 0.87, with values highest for Arizona sites, intermediate for South Carolina, and lowest for mountainous Idaho sites. Model performance was better than or equal to that of the next‐best model in 16 of 32 site‐years, and also overall. Normalization of both time and temperature produced diurnal air temperature patterns that were sufficiently general to apply with minimal loss of predictive accuracy at widely separate sites in the USA.
Analysis of Amino and Fatty Acid Composition in Soybean Seed, Using Near Infrared Reflectance Spectroscopy
Authors: Pazdernik David L. , Killam Arthur S. , Orf James H.
Published: July 2010

Soybean [Glycine max (L.) Merr.] is an important animal and human food source, mainly because of its high protein and oil concentrations. However, there is a need to improve the quality of soybean protein and oil. The objectives of this study were to (i) determine the potential use of near infrared reflectance spectroscopy (NIRS) for amino and fatty acid analysis in soybean seed and (ii) compare NIRS amino and fatty acid equations developed with ground‐seed and whole‐seed soybean samples. A total of 90 NIRS calibration samples and 26 NIRS validation samples were used for NIRS equation development and validation, respectively. All 116 soybean samples were grown at St. Paul and Rosemount, MN, in 1994 and 1995. Seventeen amino acid and five fatty acid NIRS equations for both groundseed and whole‐seed soybean samples were developed using the calibration samples. Validation of these NIRS equations showed a wide range for bias (−1.7 to 3.2 g kg−1), standard error of prediction corrected for bias [SEP(C)] (1.4 to 13.1 g kg−1), and coefficient of determination (R2) (0.38 to 0.85) for all ground‐seed NIRS equations, and a broad range for bias (−3.1 to 4.2), SEP(C) (2.6 to 17.8), and R2 (0.06 to 0.83) for all whole‐seed NIRS equations. It was concluded that NIRS could be used as a gross screening method for many amino and fatty acids contained in soybean seed. Additionally, NIRS was more accurate for amino and fatty acid analysis of ground‐seed than wholeseed soybean samples.
Cattle Grazing Preference among Eight Endophyte‐Free Tall Fescue Cultivars
Authors: Shewmaker Glenn E. , Mayland Henry F. , Hansen Susie B.
Published: July 2010

‘HiMag’ tall fescue (Festuca arundinacea Schreb.) was selected for high Mg concentration to reduce grass tetany risk to ruminants, but neither animal preference nor consumption of HiMag were known. The objectives were to evaluate methods of quantifying preference and to determine intake and preference by cattle (Bos taurus L.) of HiMag relative to seven other tall fescues. All entries were free of a fungal endophyte [Neotyphodium coenophialum (Morgan‐Jones & Gams) Glen, Bacon & Hanlin] that reduces cattle performance. The experimental design was a randomized complete block with three replications of eight cultivars nested within each of three test pastures. Six heifers grazed the vegetative to boot‐stage pastures for 48 h in May, June, August, and September of 1993 and 1994. The pastures, located at 1200 m elevation, were furrow irrigated. Pre‐ and postgrazed forage were clipped and weighed to determine yield and utilization (48‐h utilization< 50%) Preferencsec oringo f 0 to 10 (0 to 100% of forage eaten) was done by four trained observers at 24, 30, and 48 h. The heifers quickly learned to distinguish between cultivars, and their order of preference was Kenhy > KY 31 > HiMa=g Barcel= C1= Stargrazer > MO96 = Mozark. The cultivar × trial(year) interaction for preference indicated that cultivars responded differently to weather conditions, which in turn affected animal preference. Preference scoring had high repeatability and ranked cultivars similarly to the clip‐and‐weigh method of measuring utilization. Preference scoring was accomplished with 27% of the experimental error and only 6% of the time required for clip‐and‐weigh. Only 44% of the variation in preference score(PS) was explained by the model: PS = 8.8 ‐ 1.1(Mg DM yield ha−1). Estimated dry matter (DM) intake of HiMag was 6.4 kg (animal unit day)−1. Consumption and preference HiMag by cattle are satisfactory relative to other tall fescue cultivars.
Phosphorus Soil Test Calibration for Lowland Rice on an Inceptisol
Authors: Fageria Nand K. , Santos A. B. , Baligar Virupax C.
Published: July 2010

Efficient use of an adequate level of P in crop production on high‐P‐fixing acid soils is essential, due to high crop response to P fertilization and the high cost of P fertilizers. Soil‐test‐based P fertilization recommendations are not available for lowland rice (Oryza sativa L.) grown on Inceptisols. The objective of this study was to calibrate P soil testing for the response of lowland rice (cv. Javae) to added P. Two field experiments were conducted in two years at two locations in central Brazil on Haplaquept Inceptisols. In the first year, the broadcast P levels used in both experiments were 0, 87, 175, 262, 350, and 437 kg P ha−1, applied as triple superphosphate. In the second year, each residual broadcast P level from the previous year received band application of 0, 22, 44, and 66 kg P ha−1. Soil test levels of Mehlich‐1 extractable P were categorized, based on relative grain yield from the first year, as very low (0‐2.6 mg P kg−1 soil), low (2.6–8.8), medium (8.8–13.0), or high (>13.0). The amount of broadcast P needed to build up soil P test concentrations at very low, low, medium, and high soil test categories was 80, 220, 292, and >444 kg P ha−1, respectively. The rice crop produced 0 to 70%, 70 to 95%, 95 to 100%, and 100% of relative yield at the very low, low, medium, and high P levels, respectively. The amount of banded fertilizer P required to obtain maximum yield at both locations was 66 kg P ha−1 for the very low and low soil P levels, 44 kg P ha−1 for the medium soil P level, and 22 kg P ha−1 for the high soil P level.
Predicting Developmental Morphology in Switchgrass and Big Bluestem
Authors: Mitchell Rob B. , Moore Kenneth J. , Moser Lowell E. , Fritz John O. , Redfearn Daren D.
Published: July 2010

Switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) are important warm‐season grasses in livestock production systems in the central and eastern USA. The objectives of this study were to quantify the morphological development of ‘Trailblazer’ switchgrass and ‘Pawnee’ big bluestem and to evaluate day of the year (DOY) and growing degree day (GDD) as predictors of switchgrass and big bluestem morphological stage. Pure stands of each species were sampled at weekly intervals in 1990 and 1991 at Mead, NE, and classified as to mean stage count (MSC) and mean stage weight (MSW). Prediction equations for MSC and MSW were developed based on DOY and GDD. The validation study was harvested at 2‐wk intervals in 1992 and 1993 at Mead, NE, and Manhattan, KS, and classified as to MSC and MSW. Switchgrass and big bluestem MSC and MSW were related linearly in all environments. Linear DOY calibration equations accounted for 96% of the variation in switchgrass MSC across four environments, which indicates that switchgrass development was related to photoperiod and that general management recommendations could be based on DOY in the central Great Plains. Quadratic GDD calibration equations accounted for 83% of the variation in big bluestem MSC across four environments, which indicates that big bluestem development is more difficult to predict and management recommendations in the central Great Plains should be based on morphological development (which is best predicted by GDD). The comprehensive growth staging system gave repeatable results for quantifying the morphological development of switchgrass and big bluestem. The morphological development of switchgrass and big bluestem can be reliably predicted for adapted cultivars in the central Great Plains during years with near‐normal precipitation using DOY and GDD because of the determinate growth habit of these grasses.
Morphological Development of Switchgrass as Affected by Planting Date
Authors: Smart Alexander J. , Moser Lowell E.
Published: July 2010

Late‐spring and early‐summer plantings of warm‐season grasses often fail, due to dry soil conditions and competition from annual grass and broadleaf weeds. The objective of this study was to compare the morphological development of switchgrass (Panicum virgatum L.) planted in early, mid, and late spring in eastern Nebraska. This study was conducted in 1994 and 1995 at Lincoln, NE, on a Kennebec silt loam (fine‐silty, mixed, mesic Cumulic Hapludolls). ‘Blackwell’ and ‘Trailblazer’ switchgrass were planted in mid‐March, late April, and late May using a single‐row, precision grass‐seed cone planter to a depth of 0.6 to 1.3 cm at 98 pure live seed per linear meter of row in a split‐plot design. Twenty seedlings from each plot were excavated to a depth of 20 cm with a spade. Seedling morphological parameters measured were mean stage count root (MSCR) and shoot (MSCS), leaf area, shoot weight, and primary and adventitious root weight. Plots were sampled every 10 d following the first sample date. In 1994, seedlings from the March planting date were more advanced morphologically in MSCR and MSCS, had accumulated 2.5 times more leaf area, and about 3 times more shoot and adventitious root mass than the April planting date when sampled from late May to late June. In 1995, seedlings from the March planting date generally were more advanced morphologically in root and shoot development, had accumulated 2 to 12 times more leaf area, had 2 to 10 times more shoot mass, and had 2 to 33 times more adventitious root mass than the April or May planting dates at the sample periods from early June to mid‐July. We suggest that switchgrass should be planted in early spring instead of in late April and May, as suggested by previous research.
Nitrogen and Defoliation Management: Effects on Yield and Nutritive Value of Flaccidgrass
Authors: Burns Joseph C. , Chamblee Douglas S. , Belesky David P. , Fisher Dwight S. , Timothy David H.
Published: July 2010

‘Carostan’ flaccidgrass (Pennisetum flaccidum Griseb.), a C4 perennial grass, has shown high quality potential in animal trials. Its yield response to defoliation frequency and N fertilization, however, has not been reported. We examined the influence of stubble height and of a range of N applications in two defoliation experiments over 4 yr. Experiment 1 (Raleigh, NC) combined two harvest heights, 76 and 38 cm, with two stubble heights, 25 and 15 cm (76–25, 76–15, 38–25, 38–15); all treatments received 380 kg N ha−1 yr−1. After Year 1, the 76–15 defoliation produced higher yields than 76–25 (Year 2: 11 330 vs. 7930 kg ha−1, P < 0.001; Year 3:8950 vs. 6270 g kg−1, P < 0.001), while in vitro dry matter disappearance (IVDMD) was similar (Year 3) (mean = 582 g kg−1). Compared with 38–15, the 38–8 defoliation resulted in lower yields (Year 2: 8638 vs. 9344 kg ha−1, P = 0.001; Year 3, 6173 vs. 8090 kg ha−1, P = 0.07) but higher IVDMD (Year 3, 651 vs. 635 g kg−1, P < 0.01). Experiment 2 (Raleigh, NC, and Watkinsville, GA) had four defoliations: clipping to 5 cm at 20 and 51 cm (vegetative) and to 8 cm at boot and anthesis stages (20–5, 51–5, Boot—8, Anthesis—8). All defoliation treatments were topdressed with 291 kg N ha−1, and 51–5 and Boot—8 were also evaluated with 179 and 403 kg N ha−1 (eight N—defoliation treatments in all). At both locations, highest yields were obtained with Anthesis—8, averaging 19 010 kg ha−1 at Raleigh and 12 390 kg ha−1 at Watkinsville. The 20–5 defoliation resulted in lowest yields at both locations, averaging 7648 kg ha−1 at Raleigh and 5100 kg ha−1 at Watkinsville. Defoliation frequency altered IVDMD (range = 550 to 789 g kg−1), but N application did not; however, increasing N application increased N concentrations linearly (P = 0.05). Flaccidgrass had high yield potential and high nutritive value at the Raleigh location, and warrants further evaluation in the upper South.
Tracing Nitrogen Movement in Corn Production Systems in the North Carolina Piedmont: A Nitrogen‐15 Study
Authors: Crozier Carl R. , King Larry D. , Volk Richard J.
Published: July 2010

Legume cover crops have been studied in the southeastern USA, but there have been no 15N tracer studies comparing movement of legume N and fertilizer N for this region. Our study used l5N‐enriched crimson clover (Trifolium incarnatum L.) (135 kg N ha−1) and either 15NH4NO3 or NH154NO3 (70 kg total N ha−1) to quantify N movement through soil inorganic and organic N pools and into corn (Zea mays L.). Clover N mineralized rapidly, with 45% of the initially applied N detectable as inorganic N at 18 d following incorporation. Rapid nitrification of enriched NH+4 occurred, but, since the soil NO‐3 pool was larger in this treatment than in the enriched NO‐3 treatment (presumably due to chance), the relative enrichment of the soil NO‐3 pool was less than with the application of enriched NO‐3. At anthesis, 25% of the N in corn had been derived from the NO‐3 source, while only 11% had been derived from the NH+4 source (P < 0.05). At physiological maturity in 1990, the first growing season, 38 to 44% of each enriched source could be accounted for. By physiological maturity in 1991, 60% of the clover source but only 28 to 36% of the fertilizer sources could be accounted for. This study demonstrates the substantial amounts of endogenous soil N mineralization, inorganic N immobilization, and legume N persistence in these cropping systems.
Production Practices Improve Grain Sorghum and Pearl Millet Competitiveness with Weeds
Authors: Limon‐Ortega Augustin , Mason Stephen C. , Martin Alex R.
Published: July 2010

Pearl Millet [Pennisetum glaucum (L.) R. Br.] is a new grain crop adapted to many grain sorghum [Sorghum bicolor (L.) Moench] production regions, but weed control is often difficult, due to slow initial crop growth and limited herbicide options. An experiment was conducted in 1994 and 1995 to compare the competitiveness of pearl millet topcross hybrid 79‐2068A/NPM‐1 and grain sorghum singlecross hybrid DK28 with velvetleaf (A butilon theophrasti Medik.) and foxtail (Setaria spp.) as influenced by crop row spacing and N fertilizer application. The experiment was conducted on a Sharpsburg silty clay loam (fine, smectitic, mesic, Typic Argiudoll) near Mead, NE. Crops were planted in rows 38 and 76 cm apart, and N rates were 0 and 78 kg ha−1. Weed levels were obtained by differential herbicide applications at 7 d after emergence and by hand weeding. Yield losses of grain sorghum in 1994 and 1995, and pearl millet in 1995, were described by a nonlinear model based on a rectangular hyperbola. As velvetleaf and foxtail biomass approached zero, grain yield reduction of both crops was similar. In 1994, as weed pressure increased, grain sorghum yield loss was less in 38‐cm than in 76‐cm row spacing. In 1995, row spacing had no effect on grain yield. In contrast, pearl millet grain yield loss was greater in 38‐cm than in 76‐cm row spacings as weed level increased in 1995. All yield components of both crops were affected by weed level: number of kernels per head was influenced the most. Nitrogen fertilizer application enhanced yield of both crops by an average of 1.15 Mg ha‐1 in the 1994 season, but did not increase yield in the dry 1995 season. Narrowing row spacings from 76 to 38 cm increased grain yield of both crops by an average of 1.06 Mg ha−1 in 1994 and 0.83 Mg ha−1 in 1995. Grain yields of both crops were enhanced by weed control, narrow row spacing, and N application with adequate seasonal precipitation.
A Standardized Plate Meter for Estimating Pasture Mass in On‐Farm Research Trials
Authors: Rayburn Edward B. , Rayburn Susan B.
Published: July 2010

A plate meter for estimating pasture mass (PM) was constructed of 5.6‐mm‐thick acrylic plastic cut into a 46‐cm square and fitted with a 3.8‐cm center hole. (The acrylic is stable under varying humidity, readily available, inexpensive, and easy to work.) A meter stick through the center hole measures the plate height (PH) resting on the pasture canopy. The meter was tested on six rotationally grazed pastures (0.2‐2.4 ha), measured before eight grazing events. Each pasture was double‐sampled for PH and clipped PM at 10 to 30 locations. The calibration regression slope was 452 kg (ha cm)−1, with a residual standard deviation (RSD) of 753 kg ha−1 and an r2 of 0.52. The high RSD is typical of forage stands, which vary widely in forage bulk density. The relatively low r2 was probably due to the uniform height of these rotationally grazed (as opposed to continuously grazed) pastures resulting in a small range in PH. The validation regression had a slope of 0.72 and a RSD of 808 for individual samples and a slope of 1.11 and RSD of 155 for means of 20 samples. The reduction in RSD with increasing sample size points to the need to take 15 to 30 measurements when calibrating the plate meter or sampling rotationally grazed pastures, to have an estimate within 10% of the mean PM. This simple plate meter provides as accurate a measure of PH and PM as the more sophisticated metal plate meters, is practical for carrying in the field, and in 1996 cost $12.
Soybean Leaf Water Potential Responses to Carbon Dioxide and Drought
Authors: Allen Leon H. , Valle Raul R. , Jones James W. , Jones Pierce H.
Published: July 2010

Rising CO2 can have direct effects on crop water relations and indirect effects on water available for growth. We studied the effects of elevated CO2 and drought on leaf water relations of soybean [Glycine max (L.) Merr. cv. Bragg] and considered the hypothesis of osmotic adjustment mediated by increased photosynthesis (Hypothesis 1) vs. the hypothesis of water conservation mediated by decreased stomatal conductance (Hypothesis 2) to explain improved water relations of plants growing under elevated CO2. In Exp. 1, soybean was grown at 330, 450, 660, and 800 μmol mol−1 CO2 in sunlit, closed‐circulation, controlled‐environment chambers under well‐watered conditions. Leaf total water potential (WP), osmotic potential (OP), and turgor potential (TP) were measured at midday during V4 to R6 stages of development. In Exp. 2 (well‐watered, R1‐R3) and Exp. 3 (13‐d drying cycle, R6 seed filling), soybean was grown at 330 and 660 μmol mol−1 CO2, and WP, OP, and TP were measured five times per day on sunlit and shaded leaves. In Exp. 3, stomatal conductance (gs) and transpiration rate (TR) of leaves were also measured. Experiments 1 and 2 showed that elevated CO2 increased TP and decreased OP, but did not affect leaf WP, thus favoring Hypothesis 1. In Exp. 3, leaf WP was higher in elevated than ambient CO2. Diurnal TP was higher in elevated than ambient CO2 at the beginning of drought, and was maintained longer each day as drought progressed. At the end of drought, TP and WP was higher in elevated than ambient CO2. Elevated CO2 leaves had lower TR because of lower gs than ambient CO2 counterparts. Thus, Exp. 3 supported Hypothesis 2, that both stressed and nonstressed plants in elevated CO2 have a better water status (e.g., higher TP) than plants in ambient CO2 due to water conservation mediated by decreased gs. Remobilization of leaf nutrients during seed filling may limit the capability for osmotic adjustment. Regardless of the mechanisms, growth of plants in elevated CO2 should be less affected by drought than plants in ambient CO2.
Corn Response to Cover Crop Species, Spring Desiccation Time, and Residue Management
Authors: Vaughan Jeffrey D. , Evanylo Gregory K.
Published: July 2010

Cover crops are integral parts of whole farm systems that include corn (Zea mays L.), but there is a lack of synchrony between cover crop N release and corn N uptake. This synchrony may be enhanced by varying the cover crop spring desiccation time and subsequent residue management. A field study was established to determine (i) the effect of rye (Secale cereale L.), hairy vetch (Vicia villosa Roth), and rye + hairy vetch spring desiccation timing on cover crop biomass, N content, and C:N ratio and (ii) the effect of the cover crop species, spring desiccation timing, and residue management on soil moisture content, soil mineral N concentration, corn tissue N concentration, and corn grain yield. Chemical desiccation times were either the boot stage of rye (approximately 3 wk prior to corn planting) or the early flowering stage of hairy vetch (several days prior to corn planting) for all three cover crop treatments. Three cover crop residue management treatments were implemented several days after each chemical desiccation: no further treatment (control), cover crop residue mowed (mow), or cover crop residue mowed and disked (mow + disk). All cover crops increased in biomass accumulation, but only hairy vetch increased in N content between desiccation times. Cover crop N availability was more important for corn yield potential than cover crop soil moisture conservation. Corn yields were higher following hairy vetch than following rye and rye + hairy vetch, due to greater N availability from hairy vetch residue. Corn N concentrations and yields were not influenced by desiccation time following hairy vetch, indicating that hairy vetch should be allowed to grow until immediately prior to corn planting, to permit maximum N accumulation. However, corn N concentrations and yields were higher with early desiccation than late desiccation following rye and rye + hairy vetch, indicating that cover crops including rye should be desiccated several weeks before corn planting. Mowing may be an alternative cover crop management technique that enhances the synchrony of cover crop N release with corn N need and uptake while maintaining a moisture conserving mulch.
Maize and Sorghum Simulation in Diverse Texas Environments
Authors: Kiniry James R. , Bockholt Anton J.
Published: July 2010

Crop models for decision making should accurately simulate grain yields across a wide range of soils and climate regimes. This study was designed to evaluate two models' ability to simulate plot grain yields under diverse weather conditions and soils in Texas. The objective was to compare measured grain yields of maize (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench] with grain yields simulated by the ALMANAC (Agricultural Land Management Alternatives with Numerical Assessment Criteria) model and to compare measured maize yields with grain yields simulated by a new version of the CERES‐Maize (Crop‐Environment Resource Synthesis) model. Using yield performance trials, both models were tested for their ability to simulate the mean yield for five years at each location and their ability to describe year‐to‐year variability in measured yields. Both models were tested at nine locations for maize and ALMANAC was tested at eight locations for sorghum. Model inputs included parameters for the soil type, planting dates, planting rates, and locally measured weather data. Mean simulated grain yield for each site was within 10% of the mean measured grain yield for all cases, except for CERES at Thrall, where mean simulated yield was 13% lower than mean measured yield. When the models did not account for a significant amount of the year‐to‐year variability in measured grain yield at a site, it was usually due to the narrow range of measured grain yields. The soils, weather, and crop parameter data sets developed here can be useful starting points for deriving data at similar sites, giving model users examples of realistic input data.
A Database for Agroecological Research Data: I. Data Model
Authors: van Evert Frits K. , Spaans Egbert J. A. , Krieger Scott D. , Carlis John V. , Baker John M.
Published: July 2010

Data from agroecological experiments are typically stored in a collection of minimally documented computer files, with additional information entered into field or lab books. As a result of this fragmentation of data and lack of proper documentation, information may be lost and data manipulation is generally cumbersome, error‐prone, and hard to automate. Modern database technology has the potential to resolve these issues. Storing experiment data in a database solves the problem of fragmentation because all data are in the database; the problem of documentation is solved by making the relations between different items of information explicit during the design of the database; and the problem of manipulation is solved by the powerful query languages available with modern database management systems. As a first step in the construction of a generally applicable database for use in agroecological research, we used a formal method to design a data model that explicitly describes the types of information (‘entities’) one may want to remember about experiments and the relationships between these entities. The data model described here consists of 40 entities and 54 relationships. The entities are classified in five categories: (i) experiments, including statistical design; (ii) objects on which measurements are made; (iii) measurement protocol and equipment; (iv) measurements; and (v) field operations. We describe in detail how the information from several common types of measurements is stored using the proposed data model and conclude that the data model adequately describes the information that scientists in agroecological disciplines need to remember about their experiments.
A Database for Agroecological Research Data: II. A Relational Implementation
Authors: van Evert Frist K. , Spaans Egbert J. A. , Krieger Scott D. , Carlis John V. , Baker John M.
Published: July 2010

With the goal of creating a generally applicable database for agroecological research data, we developed and described a data model. The objective of the present work was to determine the practical usefulness of a database implemented from that data model. We used a commercially available relational database management system and mapped the entities of the logical data structure to tables, entity attributes to table columns, and entity relationships to foreign keys. The attributes of the entity representing measurement values were distributed over two tables, both to reduce the size of the database and to reduce the response time of queries involving this entity. We found that loading data into the database was the most significant hurdle to its use, and so developed a set of stored procedures that function as a data input language. The input language and other methods were used to load the data from an intensively monitored, multisite, multiyear experiment into the database. The database was used to manage, explore, and analyze the data from these experiments, as well as to share the data between collaborators and with others in an effective way. We conclude that a database implemented from the previously designed data model is a practical and extremely useful tool for research.
Red Clover and Tillage Influence on Soil Temperature, Water Content, and Corn Emergence
Authors: Drury Craig F. , Tan Chin‐Sheng , Welacky Thomas W. , Oloya Tom O. , Hamill Allan S. , Weaver Susan E.
Published: July 2010

No‐tillage systems on fine‐textured soil are not well suited for corn (Zea mays L.) because of problems with excess water, lower temperatures, and residue management during the early stages of corn growth. This is a problem, as corn is commonly used in rotation with wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.]. Furthermore, when corn follows winter wheat there may be additional problems associated with residue management during the early stages of corn growth. Hence, the objectives of this study were to measure the effect of the red clover (Trifolium pratense L.) cover crop underseeded in wheat and no‐tillage on soil temperature, water content, corn emergence, surface residue, and yields in a wheat‐cornsoybean rotation in southwestern Ontario. Treatments included conventional vs. no‐tillage both with and without underseeded red clover in a wheat‐corn‐soybean rotation in a clay loam soil. A no‐tillage and red clover treatment that had the wheat straw baled was also included. No‐tillage (with and without red clover) increased soil water content by 2 to 5% and reduced soil temperatures by 1 to 2°C during early corn emergence. Soil drying occurred along the planting slot of the no‐tillage treatments, which enabled the soil seed furrow to open and the corn seedlings to become water stressed even though the notillage treatments were wetter in the spring. Corn emergence in the no‐tillage treatment without red clover was delayed by 3 to 4 d and the final plant stand was reduced by 24% compared with the conventional tillage treatment. The no‐tillage treatment without red clover had 13% lower corn grain yield than the conventional tillage treatment averaged over three years. However, when red clover was included with no‐tillage, corn emergence was increased and corn grain yields were not significantly different from conventional tillage in both 1994 and 1996. There was also 15% less dry weight of surface plant residue present in the no‐tillage treatments when red clover was included. Hence, red clover alleviated some of the problems of no‐tillage for corn production.
Evaluation of the Root Zone Water Quality Model Using Field‐Measured Data from a Sandy Soil
Authors: Wu Laosheng , Chen W. , Baker John M. , Lamb John A.
Published: July 2010

Testing of simulation models against field‐measured data is an important step that must be taken before a model can be used as a management tool. Field soil water contents, intensively measured by time‐domain reflectometry (TDR) on a Zimmerman fine sand soil (Argic Udipsamments) in the Minnesota Management System Evaluation Area (MSEA), were used to evaluate the Root Zone Water Quality Model (RZWQM) over two rotated crop growing seasons in 1992 (corn, Zea mays L.) and 1993 [soybean, Glycine max (L.) Merr.]. The model was evaluated based on laboratory‐measured soil hydraulic properties. Reasonable agreement exists between the daily TDR‐measured and RZWQM‐predicted water contents for the upper soil depths. However, the model overestimated the lower soil profile, leading to a consistent overestimation of the total water depth (TWO) in the entire root zone (0 to 150 cm) during both the 1992 and 1993 growing seasons. The maximum errors in TWD for the entire root zone were 2.47 and 2.77 cm, respectively, in 1992 and 1993. Predictions of solute transport by RZWQM were examined for three herbicides: atrazine [6‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl) acetamide], and metribuzin [4‐amino‐6‐(1,1‐dimethylethyl)‐3‐(methylthio)‐1,2,4‐triazin‐5(4H)‐one]. Comparison between measured and predicted soil herbicide concentrations averaged over the top 15‐cm layer showed that the model matched the temporal changes of the field measurements reasonably well, although the measurements showed that all pesticides were somewhat more persistent over time than the model predicted.
Improving Nitrogen Use Efficiency for Cereal Production
Authors: Raun William R. , Johnson Gordon V.
Published: July 2010

Worldwide, nitrogen use efficiency (NUE) for cereal production (wheat, Triticum aestivum L.; corn, Zea mays L.; rice, Oryza sativa L. and O. glaberrima Steud.; barley, Hordeum vulgare L.; sorghum, Sorghum bicolor (L.) Moench; millet, Pennisetum glaucum (L.) R. Br.; oat, Avena sativa L.; and rye, Secale cereale L.) is approximately 33%. The unaccounted 67% represents a $15.9 billion annual loss of N fertilizer (assuming fertilizer‐soil equilibrium). Loss of fertilizer N results from gaseous plant emission, soil denitrification, surface runoff, volatilization, and leaching. Increased cereal NUE is unlikely, unless a systems approach is implemented that uses varieties with high harvest index, incorporated NH4‐N fertilizer, application of prescribed rates consistent with in‐field variability using sensor‐based systems within production fields, low N rates applied at flowering, and forage production systems. Furthermore, increased cereal NUE must accompany increased yields needed to feed a growing world population that has yet to benefit from the promise of N2‐fixing cereal crops. The Consultative Group on International Agricultural Research (CGIAR) linked with advanced research programs at universities and research institutes is uniquely positioned to refine fertilizer N use in the world via the extension of improved NUE hybrids and cultivars and management practices in both the developed and developing world.
Wheat Grain Yield and Soil Profile Water Distribution in a No‐Till Arid Environment
Authors: Bonfil David J. , Mufradi I. , Klitman S. , Asido S.
Published: July 2010

Yields of dryland crops in semiarid and arid zones are limited by precipitation, and so water content and placement are very important at each stage of development. Spring wheat (Triticum aestivum L.) grown in a wheat‐fallow (WF) rotation system (1 crop in 2 years) generally occupies the greatest area in the Israeli dryland region, more than the continuous wheat (CW) rotation system. To identify the optimal crop management for dryland farming where annual precipitation is <250 mm, we compared the effects of no‐tillage (NT) and conventional tillage (CT) on wheat growth and water use efficiency (WUE) in both the WF and the CW rotation systems, and on water storage in fallow (F) plots. During the 4‐year period from 1994 to 1997, experiments were conducted at Gilat Experimental Station, located in the south of Israel (average annual precipitation, 237 mm; soil type, sandy loam loess‐Calcic Xerosol). In the fallow year, F‐NT increased water infiltration and soil water content in comparison with F‐CT. However, most of the water evaporated during the summer, especially from the upper soil layer (0–120 cm). During growth, uncultivated soil with straw mulch increased water content in the upper soil layer and also encouraged the development of a longer root system capable of utilizing deeper water. During 1995, similar grain yields were obtained with both NT and CT treatments, an average of 3.45 t ha−1 for WF and 2.9 t ha−1 for CW. In the last 2 drought years (1996 and 1997), NT management increased yields by 62 to 67% for WF and by 18 to 75% for CW, relative to CT management. During the 2 years when water deficiency occurred during the grain‐filling stage (1994 and 1997), NT management increased grain weight by 20% and test weight by 5 to 7%, in addition to the 70 to 200% increase in the total grain yield, relative to CT management. Crop yield and WUE can be increased in arid zones with annual precipitation of <200 mm, through use of a wheat‐fallow rotation system that is managed by NT.
Response of Tall Fescue to Saline Water as Influenced by Leaching Fractions and Irrigation Uniformity Distributions
Authors: Leskys Algirdas M. , Devitt Dale A. , Verchick Linda S. , Morris Robert L.
Published: July 2010

The use of poor quality water for irrigation purposes in the urban landscape has the potential to save significant quantities of good quality water for higher priority uses. Research was conducted to determine the impact leaching fractions (LF = drainage volume/irrigation volume) and irrigation‐uniformity distributions have on the spatial distribution of water and salts and plant response when irrigating with saline water. Tall fescue (Festuca arundinacea Schreb. ‘Monarch’) was grown in 18 plots, each with a centrally located lysimeter that enabled estimates of evapotranspiration and irrigation requirements. Imposed treatments included setting LF at 0.05, 0.15, or 0.25 and manipulating plot irrigation systems such that the Christiansen uniformity coefficient (CUC) was set at 0.65, 0.75, or 0.85. Saline irrigation water (2.5 dS m−1) was applied for an 18‐mo period. Significant LF × CUC interactions were observed for depth‐weighted soil salinity, yield, evapotranspiration (ET), tissue moisture content, and canopy temperatures. Although the coefficient of variation increased with each measured parameter as the CUC decreased, only the depth‐weighted electrical conductivity (ECc) showed a coefficient of variation > 20%. A 14% savings in irrigation water was obtained when the high CUC, low LF treatment was compared with the high LF, low CUC treatment. Ninety‐one percent of the variability in the average plot ECc could be accounted for if the actual LF, lysimeter ET, and average plot canopy temperatures at the end of the experiment were taken into consideration. Under the conditions of this experiment, irrigating tall fescue with 2.5 dS m−1 water would be an acceptable practice even at LFs as low as 0.05 if the CUC is optimized.
Agronomics and Economics of Different Weed Management Systems in Corn and Soybean
Authors: Cox William J. , Singer J. S. , Shields E. J. , Waldron J. Keith , Bergstrom Gary C.
Published: July 2010

The USDA has a goal of implementing integrated pest management (IPM) practices on 75% of crop area by 2000. Growers require more economic information before adopting IPM practices. A field study was initiated in New York to evaluate weed control, yields, and net returns of chemical (broadcast herbicides), chemical–mechanical (banded herbicides and cultivations), and mechanical (rotary hoe and cultivations) weed management under moldboard plow and chisel tillage in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Chemical and chemical–mechanical weed management had similar corn net returns under moldboard plow ($370 and $355 ha−1, respectively) and chisel tillage ($282 and $287 ha−1). Mechanical weed management had less net returns in moldboard plow ($302 ha−1) and chisel tillage ($121 ha−1) because of 15% lesser corn densities and greater weed densities, especially in chisel tillage. In soybean, mechanical weed management in moldboard plow tillage had similar weed density (1.5 weeds m−2) lower yield (2.71 Mg ha−1), but similar net return ($107.50 ha−1) compared with chemical (1.3 weeds m−2, 2.92 Mg ha−1, and $85.60 ha−1, respectively) and chemical–mechanical weed management (1.0 weeds m−2, 2.78 Mg ha−1 and $99.35 ha−1, respectively). In chisel tillage, mechanical weed management had greater weed density (7.4 weeds m−2), lower yield (2.2 Mg ha−1), and lower net return (−$7.80 ha−1) compared with chemical (1.9 weeds m−2, 2.8 Mg ha−1, and $56.80 ha−1, respectively) and chemical–mechanical weed management (1.9 weeds m−2, 2.4 Mg ha−1, and $27.30 ha−1). Corn and soybean growers apparently can adopt chemical–mechanical weed management and maintain net returns. Soybean growers who use moldboard plow tillage can also adopt mechanical weed management and maintain net returns.