bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical Derivation of Stable and Nonisotopic Approaches for Assessing Soil Organic Carbon Turnover
Authors: Clay D. E. , Carlson C. G. , Clay S. A. , Reese C. , Liu Z. , Chang J. , Ellsbury M. M.
Published: April 2006

Techniques for measuring soil organic C (SOC) turnover in production fields are needed. The objectives of this study were to propose and test nonisotopic and 13C stable isotopic techniques for assessing SOC turnover. Based on SOC equilibrium and mass balance relationships, an equation was derived: NHC/SOCinitial = [1/(SOC × kNHC)](dSOC/dt) + kSOC/kNHC, where dSOC/dt is the annual change in SOC, NHC is nonharvested C returned to soil, kSOC is the annual mineralization rate of SOC, and kNHC is the annual mineralization rate of NHC. This equation was used to calculate maintenance rates. An isotopic approach based on simultaneously solving the equations was developed to determine C budgets: (i) SOCretained = [SOCfinal (Δsoil final − ΔPCR)/(ΔSOCretained − ΔPCR)]; (ii) ΔSOC retained = Δsoc initial − [ε ln(SOCretained/SOCinitial)], (iii) ΔPCR = ΔNHC − [ε ln(PCR/NHC)]; and (iv) SOCfinal = SOCretained + PCRincorp, where ε is the Rayleigh fractionation constant, PCRincorp is the amount of NHC incorporated into SOCfinal with ΔPCR being the associated 13C discrimination (Δ) value, and SOCretained is the amount of SOCinitial retained in the soil after mineralization with ΔSOC retained being the associated Δ value. Isotopic and nonisotopic approaches were tested on a production field where aboveground corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields were measured with a yield monitor and soil samples collected from a slightly offset grid (30 m) in 1995 and 2003 were analyzed for organic C and Δ. The nonisotopic approach showed that maintenance rates increased with SOC and that an accurate measure of NHC was required to calculate maintenance requirements. Sensitivity analysis of the isotopic approach showed that calculated budgets were sensitive to 13C discrimination during SOC mineralization. If 13C discrimination during SOC and NHC mineralization did not occur (ε = 0), then 14.9 and 7.6% of the SOC measured in 1995 (SOCinitial) was mineralized, and 7420 and 2780 kg C ha−1 of NHC were incorporated into SOCfinal in the 523.4‐ to 527.3‐ and 527.3‐ to 529.2‐m elevation zones, respectively. If 13C discrimination occurred (ε = −2.52‰) during SOC mineralization, then the calculated amount of SOC mineralized and the amount of new C incorporated into SOC were reduced.
Modeling the Response of Fatty Acid Composition to Temperature in a Traditional Sunflower Hybrid
Authors: Izquierdo Natalia G. , Aguirrezábal Luis A.N. , Andrade Fernando H. , Cantarero Marcelo G.
Published: April 2006

Oil quality highly depends on its fatty acid composition. In traditional sunflower (Helianthus annuus L.) hybrids, fatty acid composition is affected by night temperature during grain filling. It is unknown if the increase of oleic acid concentration when night temperature increases saturates at a temperature threshold. Modeling the response of fatty acid composition to temperature could lead to oil quality prediction. The objectives of this work were: (i) to develop precise models to estimate fatty acid composition, and (ii) to use the established models to assess differences in final fatty acid composition among regions, sowing dates, and years. The traditional hybrid Dekasol 3881 was exposed to different day–night temperature regimes during grain filling (28 and 20°C, 25 and 23°C, and 20 and 28°C). To model the response of fatty acid composition to temperature data from two field experiments, eight field crops and five growth chamber experiments were analyzed. Night minimum temperature during the 100 to 300 ddaf (degree‐days after flowering) period (base temperature = 6°C) accounted for most of the variability in oleic acid concentration (r2 = 0.84). The relationship was linear up to 22.6°C, the temperature at which the maximum value of oleic acid was reached. The model also estimated other fatty acid contents. The relationships accurately predicted independent data from Dekasol 3881 and other hybrids. Our model explained most of the variation in oleic acid concentration observed in a large region were sunflower is cultivated (27°–37° S) and it is feasible for a wide range of environmental conditions.
Crop Rotation Effects on Soil Quality at Three Northern Corn/Soybean Belt Locations
Authors: Karlen Douglas L. , Hurley Eric G. , Andrews Susan S. , Cambardella Cynthia A. , Meek David W. , Duffy Michael D. , Mallarino Antonio P.
Published: April 2006

Do extended crop rotations that include forages improve soil quality and are they profitable? Our objectives were to determine (i) how crop rotation affected soil quality indicators, (ii) if those indicator changes were reflected in soil quality index (SQI) ratings when scored and combined using the Soil Management Assessment Framework, and (iii) how SQI values compared with profitability. Soil samples were collected from three long‐term studies in Iowa and one in Wisconsin. Bulk density (BD), soil pH, water‐stable macroaggregation, total organic C, total N, microbial biomass C, extractable P and K, and penetration resistance were measured. The indicator data were scored using nonlinear curves reflecting performance of critical soil functions (e.g., nutrient cycling, water partitioning and storage, and plant root growth). Profit was calculated by subtracting costs of production from potential income based on actual crop yields and the 20‐yr average nongovernment‐supported commodity prices. Extended rotations had a positive effect on soil quality indicators. Total organic C was the most sensitive indicator, showing significant measured and scored differences at all locations, while BD showed significant differences at only one location (Kanawha). The lowest SQI values and 20‐yr average profit were associated with continuous corn, while extended rotations that included at least 3 yr of forage crops had the highest SQI values. We suggest that future conservation policies and programs reward more diverse and extended crop rotations, as is being done through the Conservation Security Program.
Threshold Value for Chlorophyll Meter as Decision Tool for Nitrogen Management of Potato
Authors: Olivier Marguerite , Goffart Jean‐Pierre , Ledent Jean‐François
Published: April 2006

We developed a practical system to improve crop N efficiency in potato (Solanum tuberosumL.). It is based on a strategy that includes split applications of N fertilizer and the use of the Hydro N Tester (HNT) leaf chlorophyll meter as a plant N status indicator. The method was tested in 12 potato field trials conducted from 1997 to 2000 on loam and sandy loam soils in Belgium. The fields were fertilized at planting with 70% of a field‐specific N recommendation. Because of site‐specific effects, raw HNT values measured during the growing season were not useful in assessing the crop N status and the need for supplemental N. In each field, there was a 200‐m2subplot receiving no N fertilizer to obtain a control HNT value. After harvest, the 12 sites were separated into two groups according to the crop response to increasing N fertilizer rates. A parameter called theHNT slopewas determined as the difference between HNT values measured in the field and those from the zero‐N plot divided by the applied N rate. This parameter shows low values for sites presenting a weak crop response to N and high values for sites with a strong response. A threshold value to determine the need for supplemental N was found to correspond to a HNT slope value of 0.5. This value was successfully validated on a commercial scale at 10 sites in Belgium in 2001 and 2002 for nonirrigated crops of cultivar Bintje.
Approaches to Modeling Potato Leaf Appearance Rate
Authors: Fleisher David H. , Shillito Rose M. , Timlin Dennis J. , Kim Soo‐Hyung , Reddy Vangimalla R.
Published: April 2006

Two approaches quantifying potato (Solanum tuberosum L. cv. Kennebec) leaf appearance rates were evaluated: a thermal time approach using the phyllochron, and a nonlinear temperature response approach using a modified β distribution function. Leaf appearance measurements at six temperature treatments (14/10, 17/12, 20/15, 23/18, 28/23, and 34/29°C thermoperiods with a 16/8 h cycle) were obtained from three SPAR (soil–plant–atmosphere–research) chamber experiments at 450 (D0), 370 (D1), or 740 (D2) μmol mol−1 atmospheric CO2 concentration. Independent data from a field study and the literature were obtained. The [CO2] effects on leaf appearance rate were not significant (P ≤ 0.05). Leaf appearance rate increased from 12 to 27.2°C and declined with increasing temperature for all SPAR data except D2. Data from D0 and D1 were pooled to estimate model parameters. Phyllochrons of 28.2 and 24.3°C‐d leaf−1 (4°C base temperature) were obtained with all temperature treatments and without the 34/29°C treatment, respectively. Parameters for the modified β distribution function were 39.5°C for the ceiling temperature, 27.2°C for the optimum temperature at which the leaf appearance rate is maximum, and 0.96 leaves plant−1 d−1 for the maximum leaf appearance rate. Both approaches were comparable with values reported in the literature and were suitable for simulating leaf appearance in the field study (root mean square deviations of 3.2 and 2.6 leaves for thermal time and response function, respectively). The temperature function approach has advantages in that nonlinear relationships, particularly those at warmer temperatures, can be included in a single equation with biologically meaningful parameters.
Corn Response to Nitrogen Rate, Row Spacing, and Plant Density in Eastern Nebraska
Authors: Shapiro Charles A. , Wortmann Charles S.
Published: April 2006

Efficient use of N by corn (Zea mays L.) is financially and environmentally important, and may be improved with higher plant density and reduced row spacing. Hypotheses were tested that irrigated corn yield in northeast Nebraska is increased by reducing row spacing from 0.76 m and increasing plant density above 61 800 plants ha−1, and that grain yield response to applied N is greater with reduced row spacing and increased plant density. Field experiments were conducted for 3 yr comparing the effects 0.76‐ vs. 0.51‐m row spacing, three plant densities, and four N rates on crop performance. The soil was a silty clay loam (mesic Cumulic Haplustoll). Nitrogen rates ranged from 0 to 252 kg N ha−1. Plant N concentration and biomass and grain yield were not affected by plant density. Decreasing row spacing from 0.76 to 0.51 m resulted in 4% more grain yield. Grain yield response to applied N and N rates for optimum yield were not affected by row spacing. Nitrogen application resulted in mean increases of 22% more biomass production and 24% more grain yield. The N response function was linear in 1996, quadratic in 1997, and quadratic with decreased yields at the high N rate (252 kg N ha−1) in 1998. Grain yield was not affected by increasing plant density above 61 800 plants ha−1 but was greater with narrow row spacing. Yield response to applied N was similar for all planting arrangements. Optimal N rate cannot be better predicted by considering plant density and row spacing.
Critical Factors for Grain Filling in Low Grain‐Ripening Rice Cultivars
Authors: Kobata Tohru , Nagano Tomonori , Ida Kumi
Published: April 2006

Some improved rice (Oryza sativa L.) cultivars such as the new plant type (NPT) lines of IRRI or Japanese indica × japonica cultivars can attach a greater density of spikelets, and hence have higher yield potential (YP); however, low grain ripening means that their higher YP is not fully used. Our objective was to clarify why their grain ripening is lower than in other cultivars, and whether low assimilate supply to grains or insufficient sink capability of spikelets restricts grain ripening in these cases. IR65564‐44‐2‐2 (NPT) and Akenohoshi (indica × japonica) cultivars yield lower percentages of ripened grain (PRG) and have lower spikelet filling percentages (F%) than other cultivars in field trials. When plant density was halved during the grain‐filling period (GFP) to improve plant dry‐matter increase (DMI), PRG and F% in Akenohoshi increased, but scarcely changed in IR65564‐44‐2‐2 and other cultivars. Inferior assimilate supply to YP limited the PRG in most cultivars due to close relationships between PRG or F% and DMI/YP; however, in IR65564‐44‐2‐2 increased DMI/YP did not improve PRG and F%. Among the higher YP cultivars, F% in IR65564‐44‐2‐2 started to decrease earlier with accumulated temperature. When panicles detached during the early GFP were cultured in a complete nutrient medium for 1 wk, F% in cultured Akenohoshi and IR65564‐44‐2‐2 was significantly greater than that under field conditions. These results suggest that inferior assimilate supply is the main cause of lower grain ripening in Akenohoshi, whereas the earlier decrease in grain ripening, probably due to higher spikelet nonfertilization, is the factor responsible in IR65564‐44‐2‐2.
Evaluating Management Zone Optimal Nitrogen Rates with a Crop Growth Model
Authors: Miao Yuxin , Mulla David J. , Batchelor William D. , Paz Joel O. , Robert Pierre C. , Wiebers Matt
Published: April 2006

Determining MZ (management zone)‐specific optimal N rate is a challenge in precision crop management. The objective of this study was to evaluate the potential of applying a crop growth model to simulate corn (Zea mays L.) yield at various N levels in different MZs and estimate optimal N rates based on long‐term weather conditions. Three years of corn yield data were used to calibrate a modified version of the CERES‐Maize (Version 3.5) model for a commercial field previously divided into four MZs in eastern Illinois. The model performance in simulating corn yield for two hybrids (33G26 and 33J24) at five N levels in two independent years was evaluated. Economically optimum N rates (EONRs) were estimated based on 15 yr of simulation (1989–2003). The model explained approximately 59 and 93% of yield variability during calibration and validation, respectively. The model performed well at non‐zero N rates, with most of the simulation errors being <10%. Model‐estimated EONR varied from 70 to 250 kg ha−1. Economic analyses indicated that applying N fertilizer at year‐, hybrid‐, and MZ‐specific EONR had the potential to increase net return by an average of US$49 (33G26) or US$52 (33J24) ha−1 over a URN (uniform rate N) application at 170 kg ha−1. Applying average hybrid‐ and MZ‐specific EONRs across years did not consistently improve economic returns over URN application; however, applying the hybrid‐ and MZ‐specific N rates that maximized long‐term net returns would improve economic return by an average of US$22 (33G26) and US$14 (33J24) ha−1
Seeding Practices, Cultivar Maturity, and Irrigation Effects on Simulated Grain Sorghum Yield
Authors: Baumhardt R. L. , Howell T. A.
Published: April 2006

Grain sorghum [Sorghum bicolor (L.) Moench] is adapted for use in dryland and irrigated cropping systems on the southern High Plains. Irrigation in this region relies on the declining Ogallala aquifer, and applications are transitioning from full to deficit evapotranspiration replacement. Our objective was to identify optimum planting date, population, row spacing, and cultivar maturity combinations to maximize grain sorghum yield using the SORKAM model and long‐term (1958–1999) weather records at Bushland, TX, for a Pullman soil (fine, mixed, superactive, thermic Torrertic Paleustoll) with reduced irrigation. Grain sorghum growth and yield was simulated under dryland and deficit‐ or full‐irrigation conditions (rain + irrigation = 2.5 or 5.0 mm d−1) for all combinations of planting date (15 May, 5 June, 25 June), cultivar maturity (early, 95 d; medium, 105 d; late, 120 d), population (12 and 16 plants m−2), and row spacing (0.38 and 0.76 m). Simulated grain yield was unaffected by planting population but increased 7% for narrow compared with wide row spacing independent of other treatment effects. Results suggest two alternative management practices to optimize yield for the southern High Plains depending on potential irrigation capacity: (i) where rain plus supplemental irrigation was <0.2.5 mm d−1, plant early‐maturing cultivars during June and (ii) where rain plus supplemental irrigation approaches 5.0 mm d−1, plant late‐maturing cultivars on 15 May. Early‐maturity cultivars planted on 5 June were better adapted to dryland and deficit irrigation for optimum grain yield on a southern High Plains Pullman soil.
Univariate Distribution Analysis to Evaluate Variable Rate Fertilization
Authors: Pena‐Yewtukhiw E. M. , Schwab Gregory J. , Murdock L. W.
Published: April 2006

Technological advances in precision fertilization such as yield monitors and remote sensing are increasing the density of samples collected and decreasing the scale inputs can be managed in the field. A compounding problem is that fertilizer applications can often be made at a much smaller scale than yield data can be collected. Analytical tools such as ANOVA and geostatistics can be used on high‐density data sets; however, these analytical tools do not provide all the information required to test research ideas. An alternative to solve this problem is the use of statistics not traditionally applied to precision agricultural experiments. The objective of this study was to determine if univariate distribution (population statistics) analysis is useful in the study of wheat (Triticum aestivumL.) yield response to variable‐rate N fertilization strategies using active optical sensors in red and near‐infrared bands (NDVI [normalized difference vegetative index] sensors). Measurements of NDVI and fertilizer applications were on a 0.56‐m2basis, while wheat yield data were collected at a 2‐m2scale. Classical ANOVA was conducted to compare treatment effects. Analysis of univariate distributions for NDVI and wheat yield monitor data sets was used to further evaluate the effect of the treatments. In addition to a significant effect on the mean NDVI and yield, fetilizer staregies affected the normality, median, mode, skewness, and kurtosis of the resulting NDVI and yield distributions. Unlike ANOVA, the analyses of univariate distributions provided an insight on those portions of the NDVI and yield populations responsible for changes in the mean.
Tillage and Nitrogen Source and Rate Effects on Corn Response in Corn–Soybean Rotation
Authors: Kwaw‐Mensah David , Al‐Kaisi Mahdi
Published: April 2006

Conservation tillage systems present a challenge for integrating an efficient fertilizer program for corn (Zea mays L.) production in the U.S. Midwest and elsewhere. The objective of this study was to evaluate corn response to three tillage systems (no‐tillage, strip‐tillage, and chisel plow) and four N rates (0, 85, 170, and 250 kg N ha−1) of liquid swine manure and commercial fertilizer in a corn–soybean [Glycine max (L.) Merr.] rotation. A 3‐yr study from 2002 to 2004 was conducted on a Kenyon soil (fine‐loamy, mixed, mesic Typic Hapludoll) at the Iowa State University Northeast Research and Demonstration Farm near Nashua, IA. The experimental design was a randomized complete block with split plots. Tillage and N rates were randomly assigned as main plot and subplot treatments, respectively. Corn grain yield and aboveground biomass response to different tillage systems were not significantly different for all N rates of both N sources; however, the biomass yield at different growth stages with different N sources, tillage, and N rates were inconsistent. There were no interaction effects of tillage and N rates on yields, except in a few cases. The 3‐yr average of maximum (MNR) and economic optimal (EONR) N rates (182 and 174 kg N ha−1, respectively) across all tillage systems with liquid manure produced identical maximum (MGY) and economic optimum (EOGY) grain yields of 11.7 Mg ha−1. In contrast, the MNR and EONR (176 and 144 kg N ha−1, respectively) with commercial fertilizer N produced a MGY and an EOGY of 11.2 and 11.1 Mg ha−1, respectively.
Estimating Source Carbon from Crop Residues, Roots and Rhizodeposits Using the National Grain‐Yield Database
Authors: Johnson J. M.‐F. , Allmaras R. R. , Reicosky D. C.
Published: April 2006

Crop residue management received little attention until about 1970. Records of crop residue production are limited, but crop yield databases have been available since 1865. Carbon sequestration and other conservation benefits require a detailed knowledge of crop residue production and management. Our objectives are to: (i) review grain and biomass yield, harvest index (HI), and root C/shoot C ratios (k) of major grain crops in the USA; (ii) discuss historical agricultural‐practice impacts on soil organic C (SOC); and (iii) compare estimates of total (above‐ and belowground) source C production (ESC) relative to minimum source C inputs required to maintain SOC (MSC). Aboveground MSC input averaged 2.5 ± 1.0 Mg C ha−1 yr−1 (n = 13) based on moldboard plow sites and 1.8 ± 0.44 Mg C ha−1 yr−1 (n = 5) based on no‐till and chisel plow sites. These MSC values included only aboveground source C, thus underestimate the total MSC. When ESC is estimated from k, including rhizodeposition (krec), the true magnitude of the C cycle is at least twice that when ESC is estimated using k excluding rhizodeposition (khis). Neglecting rhizodeposition C underestimates the net production of C in cropland. Current yields and measured MSC predict continued SOC loss associated with soybean [Glycine max (L.) Merr.] and some wheat (Triticum aestivum L.) production management unless conservation tillage is used and ESC is increased. The adequacies of ESC to maintain SOC has direct implications for estimating the amount of crop residue that can be harvested and yet maintain SOC.
Comparative Growth and Yield of Cotton Planted at Various Densities and Configurations
Authors: Siebert Jonathan D. , Stewart Alexander M. , Leonard B. Rogers
Published: April 2006

Cotton (Gossypium hirsutum L.) lint yield stability across a range of plant populations, coupled with expensive transgenic cotton seed, makes reduced seeding rates an attractive cost‐saving option. Studies evaluated plant populations and seeding configurations in an effort to: (i) isolate a specific combination that minimizes seed use without sacrificing yield, and (ii) identify potential growth and development changes associated with cotton grown at these densities. Cotton planted in studies conducted during 2003 and 2004 on a Norwood silt loam (fine‐silty, mixed, calcareous, thermic Typic Udifluvent) were hand thinned to densities ranging from 33 978 to 152 833 plants ha−1 in both hill‐drop and drill‐seeded configurations (96.5‐cm row widths). Plant height, main‐stem nodes per plant, maturity, boll retention by position, lint yield, and fiber quality were all evaluated. No seeding configuration × plant population interaction occurred for variables other than yield. A positive relationship existed between plant population and plant height; however, main‐stem nodes per plant, days after planting to peak bloom, and boll retention were inversely related to plant density. Lint yield was highest for 152 883 plants ha−1 (1465 kg ha−1) planted in a hill‐drop configuration with three plants per 20‐cm hill spacing, and was not reduced until population was lowered to 33 975 (30.5‐cm plant spacing, 1263 kg ha−1) and 50 958 (three plants per hill, 60‐cm hill spacing, 1177 kg ha−1) plants ha−1. Treatments did not influence fiber properties. Reduced seeding rates appear to be a viable cost‐saving option, given that a uniform stand is achieved and appropriate management practices employed.
Rotation Crop Evaluation for Management of the Soybean Cyst Nematode in Minnesota
Authors: Miller D. R. , Chen S. Y. , Porter P. M. , Johnson G. A. , Wyse D. L. , Stetina S. R. , Klossner L. D. , Nelson G. A.
Published: April 2006

Crop rotation is an effective tactic for soybean cyst nematode (SCN) management. In the North Central region of the USA, corn is almost exclusively used as a nonhost rotation crop with soybean. This study was conducted to determine the effectiveness of crops common to or having potential use in the North Central region as rotation crops for managing SCN. Sixteen potential rotation crops and SCN‐resistant and susceptible soybeans were grown along with six fallow controls in three commercial field sites near Waseca, Lamberton, and Morris, MN, in 2001, and SCN‐susceptible soybean was grown on all plots in 2002. Nematode populations at planting, midseason, and harvest were measured both years; soybean yield was measured in 2002. There was large variability in SCN populations and soybean yields at the three sites. Nevertheless, significant treatment effects were detected at all sites. While all of the rotation crops lowered SCN populations compared with SCN‐susceptible soybean, there were only subtle differences among the individual rotation crops and among different groups of the crops. Leguminous nonhosts or poor hosts were best in reducing SCN population density. Corn, the most common rotation crop in Minnesota, was among the least effective in reducing nematode populations. There was an undetectable yield benefit from SCN management, although differences in yield were observed among the rotation crop treatments—probably due to agronomic factors. The data suggest that a single year of rotation of soybean with any of these crops before planting a susceptible soybean may not be sufficient in managing SCN.
Characterizing Water and Nitrogen Stress in Corn Using Remote Sensing
Authors: Clay D. E. , Kim Ki‐In , Chang J. , Clay S. A. , Dalsted K.
Published: April 2006

Interactions between water and N may impact remote‐sensing‐based N recommendations. The objectives of this study were to determine the influence of water and N stress on reflectance from a corn (Zea mays L.) crop, and to evaluate the impacts of implementing a remote‐sensing‐based model on N recommendations. A replicated N and water treatment factorial experiment was conducted in 2002, 2003, and 2004. Yield losses due to water (YLWS) and N (YLNS) stress were determined using the 13C discrimination (Δ) approach. Reflectance data (400–1800 nm) collected at three growth stages (V8–V9, V11–VT, and R1–R2) were used to calculate six different remote sensing indices (normalized difference vegetation index [NDVI], green normalized vegetation index, normalized difference water index [NDWI], N reflectance index, and chorophyll green and red edge indices). At the V8–V9 growth stage, increasing the N rate from 0 to 112 kg N ha−1 decreased reflectance in the blue (485 nm), green (586 nm), and red (661 nm) bands. Nitrogen had an opposite effect in the near‐infrared (NIR, 840 nm) band. At the V11–VT growth stage, reflectance in the blue, green, and red bands were lower in fertilized than unfertilized treatments. At the R1–R2 growth stage, YLWS was highly correlated (r = 0.58, P = 0.01) with red reflectance and NDVI (r = −0.61, P = 0.01), while YLNS was correlated with all of the indices except NDVI. A remote sensing model based on YLNS was more accurate at predicting N requirements than models based on yield or yield plus YLWS. These results were attributed to N and water having an additive effect on yield, and similar optimum N rates (100–120 kg N ha−1) for both moisture regimes.
Delayed Harvest Effect on Soft Red Winter Wheat in the Southeastern USA
Authors: Farrer Dianne , Weisz Randy , Heiniger Ronnie , Murphy J. Paul , Pate Michael H.
Published: April 2006

Harvest of soft red winter wheat (Triticum aestivum L.) in the southeastern USA can be delayed because of inclement weather or other unforeseen problems. Our objectives were to determine the impact of delaying harvest beyond grain ripeness (135 g kg−1 grain moisture content) on yield, test weight, grain protein, and 20 milling and baking quality parameters, and to determine if these impacts were correlated with environmental conditions occurring between grain ripeness and harvest. In 2001 and 2002, a total of six trials were conducted where treatments consisted of a timely harvest at grain ripeness and a delayed harvest, 8 to 19 d later. Yield was reduced by up to ∼900 kg ha−1 due to delayed harvest, with yield losses negatively related to total precipitation and positively related to minimum daily temperatures (R2 = 0.99) during the delay interval, indicating that dry and warm environments increased yield losses. Test weight reductions up to ∼115 kg m−3 were seen and were linearly related to the number of precipitation events (r2 = 0.93) between harvests. Grain protein was not affected by delayed harvest. Of the milling and baking quality parameters measured, grain and flour falling number, clear flour percentage, grain deoxynivalenol (DON), and farinograph breakdown times were negatively affected by delayed harvest. Lower falling numbers and higher levels of DON are consistent with the high humidity and rainfall typical of the southeastern USA wheat harvest and are problematic for millers. Decreased farinograph breakdown times can be a problem for bakers.
Cotton Yield and Fiber Quality from Irrigated Tillage Systems in the Tennessee Valley
Authors: Balkcom Kipling S. , Reeves D. Wayne , Shaw Joey N. , Burmester Charles H. , Curtis Larry M.
Published: April 2006

Cotton (Gossypium hirsutum L.) yield and quality responses to irrigation have not been described for conservation management systems that growers are rapidly adopting. We conducted a field experiment from 2001–2003 in the Tennessee Valley near Belle Mina, AL on a Decatur silt loam (fine, kaolinitic, thermic Rhodic Paleudults) to examine how irrigation regimes and tillage systems affect ginning percentage, lint yield, and fiber quality (length, micronaire, strength, and fiber length uniformity). Treatments were arranged with a split‐plot structure in a randomized complete block design with three replications. Main plots were a factorial combination of conventional tillage (CT) with and without a fall paratill operation and no surface tillage (NST) following a rye (Secale cereale L.) cover crop with and without a fall paratill operation. Subplots were irrigation regimes (0, 2.7, 5.4, and 8.1 mm d−1). Ginning percentage increased 2% following CT in 1 of 3 yr (2002) while irrigation improved ginning percentage in 2 of 3 yr (2002 and 2003). The NST systems increased lint yields 13% in 2003 compared with CT systems while irrigation increased yields 46 and 32% over nonirrigated yields in 2002 and 2003, respectively. Fiber properties were affected by tillage systems, primarily in 2002. Irrigation regimes affected length, micronaire, and fiber length uniformity in 2002 and 2003. Fall paratilling had no effect on any measured variable, except for an inconsistent difference between tillage systems for fiber length uniformity. An irrigated conservation system, utilizing a cover crop, can improve cotton yields and positively influence fiber characteristics in the Tennessee Valley.
Nutrient Use Efficiencies and Leaching of Organic and Conventional Cropping Systems in Sweden
Authors: Torstensson Gunnar , Aronsson Helena , Bergström Lars
Published: April 2006

Organic farming has been proposed as a means of reducing leaching and improving the use efficiency of plant nutrients in agriculture. In such systems, nutrient inputs originate from various organic sources or from naturally occurring minerals with low solubility. In this study, measurements of leaching and crop uptake of N, P, and K and determinations of mineral N in soil were conducted in tile‐drained plots during a 6‐yr period in two organic crop rotations, one with and one without addition of animal manures. In the latter, N was provided by green manures. For comparison, two conventional systems in which mineral fertilizers and pesticides were used (one with cover crops) were also included. Leaching loads of N were smallest in the conventional system with cover crops, on average 25 kg N ha−1 yr−1 over the 6‐yr period. The corresponding amounts in the other systems were 39 (organic with animal manure), 34 (organic without animal manure), and 38 (conventional) kg N ha−1. Phosphorus‐leaching loads were small overall in all systems (<0.25 kg ha−1 yr−1). Potassium‐leaching loads reached on average 27 kg ha−1 yr−1 over the 6 yr in the conventional systems and 16 kg ha−1 yr−1 in the organic systems. When N leaching was expressed as a percentage of total N removal during the 6‐yr period (leaching plus harvested N with crops), it represented 59% in the organic system without animal manure, 33% in the conventional system, and 22% in the conventional system with cover crops. These results clearly suggest that N use efficiency is improved if inorganic N fertilizers are used rather than green manures, especially in combination with cover crops. The superior system from all considerations was the conventional system with a cover crop.
Sugarcane Response to Water Table, Periodic Flood, and Foliar Nitrogen on Organic Soil
Authors: Glaz Barry , Gilbert Robert A.
Published: April 2006

Sugarcane (Saccharum spp.) is routinely exposed to periodic floods and high water tables in Florida's Everglades Agricultural Area. Learning sugarcane responses to these conditions will help improve yields. This study evaluated the effects of constant water‐table depths, periodic floods, and N on cane and sucrose yields of two sugarcane cultivars. In 2001 and 2002, two foliar N and four water treatments were applied to the first two crop‐growth cycles (plant and first‐ratoon crops) of ‘CP 72‐2086’ and ‘CP 80‐1827’ in lysimeters filled with Pahokee muck soil. Constant water‐table depths were 23, 37, and 51 cm. A fourth treatment was flooding for 2 d in each of eight 14‐d cycles per year; otherwise its water‐table depth was 44 cm. Foliar N did not consistently affect yields. In nonflooded treatments across cultivars and crop growth cycles, for every centimeter increase in water‐table depth, theoretical recoverable sucrose decreased by 0.13 g kg−1, and cane and sucrose yields increased by 0.16 and 0.02 kg m−2, respectively. By cultivar and crop‐growth cycle, the only significant linear responses to nonflooded water‐table treatments were in the first‐ratoon crop, where for each centimeter increase in water‐table depth, cane and sucrose yields increased by 0.38 and 0.04 kg m−2, respectively. Periodic flooding increased cane and sucrose yields in the plant crop and sustained or improved these yields in the first‐ratoon crop. After rains, allowing floods to remain for up to 2 d may improve yields and reduce P discharge to the Everglades.
Development and Validation of a Phosphate Rock Decision Support System
Authors: Smalberger Suzette A. , Singh Upendra , Chien Sen H. , Henao Julio , Wilkens Paul W.
Published: April 2006

Although some mathematical models exist to assist in deciding whether or not to apply phosphate rock (PR) to soils as a source of P, these models focused either on the use of highly soluble PR sources, mainly for pastures, or were too impractical for field use. There was, therefore, a need to develop a Phosphate Rock Decision Support System (PRDSS) with more comprehensive capabilities to predict the relative agronomic effectiveness (RAE) of PR with respect to water‐soluble phosphorus (WSP) fertilizers at field and farm level. The PRDSS includes PR sources varying widely in solubility and different crop species grown on variable soil properties and rainfall conditions. In this paper, we describe the development and use of the mathematical model, PRDSS, to estimate RAE of PR sources with respect to WSP fertilizers and to calculate a simple index to be used for preliminary economic comparison of these two types of P sources. The PRDSS is able to function with a minimum input of only soil pH, the name of the mine that is the source of the phosphate rock, and the species of crop to be grown. A more accurate prediction of RAE is obtained from the PRDSS when more detailed data describing the soil, crop, and weather are included as inputs.
Enhanced Protease Inhibitor Expression in Plant Residues Slows Nitrogen Mineralization
Authors: Kumar K. , Rosen C. J. , Russelle M. P.
Published: April 2006

Organic N mineralization by extracellular proteases affects inorganic N availability and loss. Soil N mineralization is slowed by addition of purified protease inhibitors. We hypothesized that elevated concentrations of protease inhibitors in plant residues would reduce soil and plant residue N mineralization. Isogenic controls and transgenic plants of Brassica (Brassica napus L.), Japonicum rice (Oryza sativa L.), and tobacco (Nicotiana tabaccum L.) showing enhanced wound‐inducible protease inhibitor production were grown in a greenhouse, and leaves were mechanically wounded 3 d before shoot removal. Transgenic plants and their isogenic controls did not differ in N concentration, C/N ratio, or lignin concentration in shoot residues, but protease inhibitor concentration was 1.5 to 2.3 times greater in the transgenic lines. In laboratory incubations in a loamy sand soil, inorganic N in leachate from transgenic plants was significantly lower than isogenic controls for the first 30 d when the residues remained on the soil surface and were higher at one or more dates thereafter. When residues were mixed with soil, differences were observed only for Brassica. Cumulative N mineralization in static incubations of residues mixed with soil followed the order Brassica > tobacco > rice residues. In general, transgenic residues mineralized between 22 and 27% less N than control plant residues in the first 30 d, but no differences in soil N mineralization were detected. Thus, protease inhibitor concentration of plant residues should be included with measures of total N concentration, C/N ratio, and lignin concentration to improve prediction and potentially management of short‐term N mineralization from plant residues.
Associate Editor's Role in Helping Authors and Upholding Journal Standards
Authors: Pearson Calvin H. , Mullen Robert W. , Thomason Wade E. , Phillips Steve B.
Published: April 2006

Scientists must publish the findings of their research for the public good while making an impact on behalf of their funding agencies and institutions or organizations. In this article, we examine associate editor responsibilities and functions to determine the suitability of manuscripts for publication in Agronomy Journal. Associate editors comprise the largest component of scientific editors on the Agronomy Journal Editorial Board and have more one‐on‐one contact with authors than do technical editors, the Managing Editor, the Assistant Editor, or the Editor. A large number of scientific reviewers assist associate editors in evaluating manuscripts submitted to the journal. Identifying qualified reviewers is a critical task for associate editors. Reviewers of manuscripts provide comments, suggestions, and recommendations for publication, while associate editors assess that information to determine if the manuscript should be published. During the review process, associate editors correspond and work with authors and reviewers, obtain revisions as needed, and mediate technical issues and differences. Because the ultimate goal is to help authors publish their papers, associate editors often find themselves as author advocates during the review process. Thus, associate editors carry a dual obligation in that they must serve the needs of authors and also uphold the standards and reputation of the journal.
“Mir”acles in hox gene regulation
Authors: Chopra Vivek S. , Mishra Rakesh K.
Published: April 2006

Micro RNAs (miRNAs) have been shown to control many cellular processes including developmental timing in different organisms. The prediction that miRNAs are involved in regulating hox genes of flies and mouse is quite a recent idea and is supported by the finding that mir‐196 represses Hoxb8 gene expression. The non‐coding regions that encode these miRNAs are also conserved across species in the same way as other mechanisms that regulate expression of hox genes. On the contrary, until now no homeotic phenotype, a hallmark of any hox gene mutation, had been associated with any hox miRNA. Recent work on bithorax complex miRNA (miR–iab‐4–5p) shows, for the first time, that miRNAs can lead to homeotic transformation. This miRNA regulates Ultrabithorax (Ubx) and results in the transformation of haltere to wing.1 This study unveils a new complexity and finesse to the regulation of hox gene expression pattern that is needed for determining the anteroposterior body axis in all bilaterians. BioEssays 28: 445–448, 2006. © 2006 Wiley Periodicals, Inc.
Functional diversity of FGF‐2 isoforms by intracellular sorting
Authors: Sørensen Vigdis , Nilsen Trine , Wiȩdłocha Antoni
Published: April 2006

Regulation of the subcellular localization of certain proteins is a mechanism for the regulation of their biological activities. FGF‐2 can be produced as distinct isoforms by alternative initiation of translation on a single mRNA and the isoforms are differently sorted in cells. High molecular weight FGF‐2 isoforms are not secreted from the cell, but are transported to the nucleus where they regulate cell growth or behavior in an intracrine fashion. 18 kDa FGF‐2 can be secreted to the extracellular medium where it acts as a conventional growth factor by binding to and activation of cell‐surface receptors. Furthermore, following receptor‐mediated endocytosis, the exogenous FGF‐2 can be transported to the nuclei of target cells, and this is of importance for the transmittance of a mitogenic signal. The growth factor is able to interact with several intracellular proteins. Here, the mode of action and biological role of intracellular FGF‐2 are discussed. BioEssays 28: 504–514, 2006. © 2006 Wiley Periodicals, Inc.
Structural and functional diversity of adaptor proteins involved in tyrosine kinase signalling
Authors: Csiszár Ágnes
Published: April 2006

Adaptors are proteins of multi‐modular structure without enzymatic activity. Their capacity to organise large, temporary protein complexes by linking proteins together in a regulated and selective fashion makes them of outstanding importance in the establishment and maintenance of specificity and efficiency in all known signal transduction pathways. This review focuses on the structural and functional characterisation of adaptors involved in tyrosine kinase (TK) signalling. TK‐linked adaptors can be distinguished by their domain composition and binding specificities. However, such structural classifications have proven inadequate as indicators of functional roles. A better way to understand the logic of signalling networks might be to look at functional aspects of adaptor proteins such as signalling specificity, negative versus positive contribution to signal propagation, or their position in the signalling hierarchy. All of these functions are dynamic, suggesting that adaptors have important regulatory roles rather than acting only as stable linkers in signal transduction. BioEssays 28: 465–479, 2006. © 2006 Wiley Periodicals, Inc.
Lean consumption and its influence on brand
Authors: Truch Edward
Published: April 2006

The continuing growth of the knowledge‐based economy is driving the quest for better understanding of the intangible drivers of wealth creation. American and European models for linking customer satisfaction to corporate and national performance have been established and will continue to be tested and developed. One of the challenges of modelling consumer behaviour is the effect of changing lifestyles. This paper describes a study of UK shoppers which explores the influence of lean consumption, the degree to which the shopping and post‐purchase experience is hassle free and timely, on the warmth of consumers' feelings towards the brand. The study operationalises the construct of lean consumption and finds that it is indeed a significant driver of brand warmth. This leads to clear implications for manufacturers and retailers and the ways in which they innovate and develop their products and services.

Copyright © 2006 John Wiley & Sons, Ltd.
Effect of serotonin‐acting agents on the serotonin content of immune cells. A peculiar observation
Authors: Pállinger Éva , Csaba G.
Published: April 2006

The effect of the tryptophan hydroxylase inhibitor, PCPA methylester, the serotonin reuptake inhibitor fluoxetine and MAO‐A inhibitor clorgyline on the serotonin content of rat immune cells was studied, using labelled antibodies and flow cytometry. Each molecule significantly increased in males the serotonin concentration of peritoneal lymphocytes and the monocyte‐macrophage‐granulocyte group (mo‐gran), however the agents were ineffective towards mast cells. In females fluoxetine and clorgyline increased the serotonin concentration in peritoneal lymphocytes and mo‐gran. Fluoxetine also increased the serotonin level in mast cells. Thymus was absolutely resistant to the drugs in both genders. The results call attention (1) to the reverse effect of serotonin‐acting agents on immune cells, (2) to the influence of the milieu where the cell is located and (3) the effect of gender. Copyright © 2006 John Wiley & Sons, Ltd.
Differences between first and subsequent rounds of the MRISC breast cancer screening program for women with a familial or genetic predisposition
Authors: Kriege Mieke , Brekelmans Cecile T. M. , Boetes Carla , Muller Sara H. , Zonderland Harmine M. , Obdeijn Inge Marie , Manoliu Radu A. , Kok Theo , Rutgers Emiel J. T. , de Koning Harry J. , Klijn Jan G. M. ,   Dutch MRI Screening (MRISC) Study Group
Published: April 2006

BACKGROUND

Within the Dutch MRI Screening (MRISC) study, a Dutch multicenter screening study for hereditary breast cancer, the authors investigated whether previously reported increased diagnostic accuracy of magnetic resonance imaging (MRI) compared with mammography would be maintained during subsequent screening rounds.

METHODS

From November 1999 to October 2003, 1909 eligible women were included in the study. Screening parameters and tumor characteristics of different rounds were calculated and compared. The authors defined 3 different types of imaging screening rounds: first round in women never screened by imaging before, first round in women screened by imaging (mainly mammography) before, and subsequent rounds.

RESULTS

The difference in sensitivity for invasive cancers between mammography and MRI was largest in the first round of women previously screened with mammography (20.0 vs. 93.3%; P = .003), but also in subsequent rounds, there was a significant difference in favor of MRI (29.4 vs. 76.5%; P = .02). The difference in false‐positive rate between mammography and MRI was also largest in the first round of women previously screened with mammography (5.5 vs. 14.0%; P<.001), and it remained significant in subsequent rounds (4.6 vs. 8.2%; P<.001). Screen‐detected tumors were smaller and more often lymph node negative than symptomatic tumors in age‐matched control patients, but no major differences in tumor stage were found between tumors detected at subsequent rounds compared with those in the first round.

CONCLUSIONS

In subsequent rounds, a significantly higher sensitivity and better discriminating capacity of MRI compared with mammography was maintained, and a favorable tumor stage compared with age‐matched symptomatic controls. As results of these subsequent screening rounds were most predictive for long‐term effects, the authors expect that this screening program will contribute to a decrease of breast cancer mortality in these high‐risk women. Cancer 2006. © 2006 American Cancer Society.