bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tillage System and Crop Residue Effects on Surface Compaction of a Paleustoll
Authors: Dao Thanh H. 
Published: July 2010

AbstractConcern of excessive compaction of soils under conservation tillage (CT) has persisted as CT practices gain acceptance in major agricultural systems. The objective of the study was to determine the cumulative effects of tillage systems [moldboard plowing (MT), stubble‐mulch tillage (ST), and no‐till (NT)] and rates of crop residues on bulk density of the near‐surface zone under annual winter wheat cropping. In the fall of 1983, tillage plots were established on Bethany (fine, mixed, thermic Pachic Paleustoll) and Renfrow (fine, mixed, thermic Udertic Paleustoll) silt loams on a 2% slope near El Reno, OK. Bulk density and water content were measured to a depth of 0.3 m in 0.025‐m increments using gamma and neutron attenuation techniques during 1991 and 1992. After planting, MT and ST soils had the lowest mean surface density; these soils consolidated as bulk density during winter wheat dormancy averaged 1.34 (±0.06), 1.30 (±0.06), 1.21 (±0.06) in 1991, and 1.31 (±0.06), 1.30 (±0.05) and 1.24 (±0.05) Mg m−3 in 1992 in MT, ST, and NT soils, respectively. Near the end of the season, surface density of ST and MT soils had increased by 1.6 and 4.8%, respectively. No‐till soil showed a decrease of 5.4% during the same overwinter period and had the lowest bulk density in the end. The inherent reduction in field operation traffic in CT systems, and a decrease in tillage intensity proportionately reduced soil surface compaction under annual wheat cropping. Bulk density increased with soil depth in all treatments; however, NT resulted in decreased soil density in and below an old restrictive layer more effectively than ST or MT management. Removal of crop residues resulted in higher bulk density, primarily in the 0.05‐ to 0.125‐m depth of MT soils, and in the 0 to 0.05‐m surface layer of NT soils. Maintaining high amounts of wheat residues at the soil surface helps improve the macroporosity of near‐surface zones of soils under conservation tillage. Severe compaction of CT soils did not appear prevalent under winter wheat production to cause physical constraints to crop growth in subhumid regions.
Management Influences on Arbuscular Mycorrhizal Fungal Species Composition in a Corn‐Soybean Rotation
Authors: Kurle James E. , Pfleger Francis L. 
Published: July 2010

AbstractCrop and edaphic factors influence arbuscular mycorrhizal (AM) fungal species composition and populations. This study was conducted to determine the effect of management history, crop, and input system on species composition of AM fungal spore populations. Corn (Zea mays L.)‐soybean [Glycine max (L.) Merr.] sequences receiving no inputs (NI), organic inputs (OI), minimum inputs (MI), and conventional inputs (CI) were established in two adjacent areas with differing management histories: one area, the Koch Farm, had received no fertilizer or herbicide inputs for the past 25 yr; the other area, the experiment station, received recommended herbicide and fertilizer inputs. Fifteen AM fungal species were found in a survey of mycorrhizal fungal spore populations. Glomus aggregatum populations were positively correlated with Setaria spp. populations (r = 0.56), pH (r = 0.47), and K (r = 0.25) and negatively correlated with soil P (r = −0.57). Populations of Gl. geosporum, Gl. leptotichum, Gl. macrocarpum, and Gl. occultum were also positively correlated with soil pH and negatively correlated with soil P. Gigaspora margarita spore populations were positively correlated with soil P level (r = 0.272). Although species richness was greater (13 species vs. 10), species diversity (Hw) was lower at the Koch Farm than the experiment station (0.57 vs. 0.64) because of large Gl. aggregatum spore populations. The correlation of AM fungal spore populations with Setaria spp. and P, K, and pH indicates that management practices influence AM fungal species composition through both biotic and abiotic factors.
Soil Temperature and Planting Date Effects on Corn Yield, Leaf Area, and Plant Development
Authors: Bollero Germán A. , Bullock Donald G. , Hollinger Steven E. 
Published: July 2010

AbstractEarly‐season soil temperature has been reported to affect leaf appearance and expansion rates, and consequently corn (Zea mays L.) ontogeny. A 2‐yr field experiment was conducted on a Drummer silty clay loam (fine silty, mixed, mesic Typic Haplaquoll) at the Agronomy and Plant Pathology South Farm of the University of Illinois at Urbana‐Champaign. Treatments consisted of planting date (early May and early June) and soil temperature surrounding the corn growing point (5°C below ambient, ambient, and 5°C above ambient). Soil temperature was controlled using warm and cool water circulating through copper pipes buried next to the corn rows. Air temperatures were not controlled. Irrigation was used. The experimental design was a split plot in a randomized complete block with four replications. Ten plants were randomly selected within each replication and nondestructive measures of plant stage, individual leaf area, and leaf senescence were taken three times per week from emergence to V5, and once per week afterwards until complete leaf senescence. Growing degree days (GDD) were calculated using the modified growing degree day formula (MGDD). From planting to V5, MGDD were computed using the soil maximum and minimum daily temperatures from each treatment. After the soil temperature treatments were terminated, the MGDD calculations were based on maximum and minimum daily air temperatures. Lower early‐season soil temperature delayed corn development and modified individual leaf area. Plants under these cooler conditions went through vegetative developmental stages faster per unit of accumulated MGDD, showing the effect of temperature on corn ontogeny. The results also show that the current method of calculating MGDD (with base temperature of 10°C) does not adequately predict corn development under exceptionally warm or exceptionally cool soils. Warmer early‐season soil temperature linearly increased corn yield (β1 = 0.14 Mg ha−1 °C−1). Leaves in the lower half of the canopy were larger under cooler soil temperature treatments (β1 = −48.9 cm2 °C−1). There was a linear increase in the size of the leaves in the upper half of the canopy of the plants under warmer temperatures (β1 = 28.8 cm2 °C−1).
Simulating Effects of Genes for Physiological Traits in a Process‐Oriented Crop Model
Authors: White Jeffrey W. , Hoogenboom Gerrit 
Published: July 2010

AbstractRecent improvements in crop simulation techniques and in understanding of crop genetics suggest the possibility of integrating genetic information on physiological traits into crop simulation models. By using known genotypes, rather than empirically fitted cultivar‐specific coefficients, a simulation model should permit more explicit testing of hypotheses concerning the genetic basis of adaptation of cultivars to different environments or production systems. This paper describes and evaluates GeneGro, a version of the dry bean (Phaseolus vulgaris L.) crop simulation model BEANGRO version 1.01 modified to incorporate effects of seven genes affecting phenology, growth habit, and seed size: Ppd, Hr, Fin, Fd, and Ssz‐l, and two more genes for seed size inferred from indirect evidence. Thirty cultivars were calibrated for BEANGRO using data from 14 trials conducted in Colombia, Guatemala, Mexico, and Florida. The resulting cultivar‐specific coefficients of BEANGRO were replaced with information on specific genotypes of cultivars to create the gene‐based model. With cultivar differences specified only by the seven genes, GeneGroe xplained 31% of observed variation for seed yield, 58% for seed weight, 84% for days to flowering, 85% for days to maturity, 52% for maximum leaf area index, and 36% for canopy dry weight at maturity, but 0% for harvest index. In testing the effectiveness of GeneGro after overall trial and cultivar effects were accounted for through regression analysis, all simulated data except for seed weight showed significant relations with observed data (P ≤ 0.01). Our results indicate that for certain traits surprisingly few genes must be characterized to simulate cultivar differences as accurately as with the BEANGRO model. Furthermore, they suggest a potential for developing models similar to GeneGro for studying the effects of genes on adaptation in other crops.
Winter Legume Cover Crop Benefits to Corn: Rotation vs. Fixed‐Nitrogen Effects
Authors: Torbert H. Allen , Reeves Donald W. , Mulvaney Richard L. 
Published: July 2010

AbstractThe use of winter legume cover crops for erosion control and to provide additional N to the soil is well established. Other potential benefits to legume cover crops besides N additions have been recognized, but have not been quantified. The objective of this study was to separate the fixed‐N effects from the rotation effects in a winter legume cover cropping system. A field study was initiated in 1989 on a Norfolk loamy sand (fine, loamy, siliceous, thermic Typic Kandiudult) in east‐central Alabama. Corn (Zea mays L.) was grown following (i) ‘Tibbee’ crimson clover (Trifolium incarnatum L.), (ii) a partially ineffective‐nodulating crimson clover, CH‐1, (iii) rye (Secale cereale L.), and (iv) winter fallow. The plots were split into four rates of fertilizer N (0, 56, 112, and 168 kg N ha−1) in a split‐plot experimental plan. An evaluation of different methods of distinguishing fixed‐N vs. rotation effects of the winter annual legume cover crop to a subsequent corn crop was made. Regression analysis of the effect of N application rates on N2 fixation by crimson clover (fertilized with 45 kg N ha−1) indicated that CH‐1 clover biomass contained approximately 40 and 101 kg N ha−1 and Tibbee clover contained approximately 51 and 119 kg N ha−1 in 1990 and 1991, respectively. In both years of the study, crimson clover substantially increased corn yield compared with winter fallow, with a yield increase at the highest fertilizer N application level of 7 and 22% for 1990 and 1991, respectively. Estimates of yield increases due to rotation ranged from negative to 40%. The data indicated that winter cover crops improve corn yield and that besides soil N availability, there was very little difference between the beneficial effects of clover and the rye cover crops to corn.
Comparisons between an Upland and a Pima Cotton Cultivar: I. Growth and Yield
Authors: Unruh Bryan L. , Silvertooth Jeffrey C. 
Published: July 2010

AbstractAmerican Pima cotton (Gossypium barbadense L.) is an extra‐long staple cotton produced in the southwestern USA and in other regions around the world. Pima cotton generally yields less than Upland (G. hirsutum L.), but there have not been any studies conducted to document the basis for these differences. Field trials were conducted at two south‐central Arizona locations from 1990 through 1992 for the purpose of comparing growth and yield between representative cultivars of Upland and Pima cotton. The aboveground portion of Upland ‘Deltapine 90’ (DPL 90) and Pima ‘S‐6’ were harvested and separated into stems, leaves (including petioles), burs (carpel walls), lint, and seeds. The bur fraction also included immature fruiting forms. Dry matter accumulation was modeled as a function of heat units (HU) accumulated after planting (HUAP). Both cultivars exhibited a linear increase of total dry matter over the duration of sampling. By the end of sampling, DPL 90 produced more total, stem, seed, lint, and reproductive (bur + seed + lint) dry matter than Pima S‐6; the dry matter that accumulated in leaves, bur fraction, and vegetative structures (leaf + stem) did not differ. The reproductive/vegetative ratio (RVR) was found to be similar for both cultivars, increasing rapidly with HU accumulation. Comparisons of lint dry matter accumulation as a function of RVR and harvest index (HI) revealed that DPL 90 yields more lint than Pima S‐6 due to a greater total biomass production and more efficient partitioning of dry matter into reproductive organs.
Crop Modeling: From Infancy to Maturity
Authors: Sinclair Thomas R. , Seligman No'am G. 
Published: July 2010

AbstractCrop modeling, the computerized simulation of dynamic crop systems, was born about 30 years ago, when systems analysis and modern computers presented a new technique to crop scientists. Since then, crop modeling has gone through a number of developmental stages, similar to those of living organisms. From its infancy, crop modeling seemed to promise a well‐behaved, elegant surrogate for ambiguous and cumbersome field experimentation. Indeed, some of the earliest models proved to be among the most notable achievements to date. During the juvenile stage that followed, there was an impressive increase in complexity and computer sophistication, accompanied by some of the growing pains of childhood. Greater expectations led to more and more detailed descriptions of the functioning of the biotic and abiotic components of cropping systems. The results were often trivial, and the big payoff tended to recede into the future, but the need for predicting future crop performance for management and hypothesis testing, together with progress in crop science and computer technology, spurred crop modeling. The next phase, adolescence, a period marked by intense activity, confusion, and excessive confidence‐sometimes challenged by doubt‐appears to be extending into the present. Not only is the original promise turning out to be elusive, but widely accepted guidelines for scientific modeling, such as greater reductionism, universality, and validation, are being questioned. Maturity may be emerging as expectations become pragmatically adjusted to reality. Crop modeling, like advanced ecological modeling, is proving to be more a heuristic tool than a surrogate for reality. In academic, research, and applied roles, such models can be of great value when used as aids to reasoning about the functioning and response of crop systems under many relevant, nontrivial scenarios.
Analysis of Aerial Photography for Nitrogen Stress within Corn Fields
Authors: Blackmer Tracy M. , Schepers James S. , Varvel Gary E. , Meyer George E. 
Published: July 2010

AbstractSpatial variability of soil parameters within fields complicates N fertilizer recommendations for corn (Zea mays L.) production. Thus, the ability to identify differences in crop N status within corn fields could lead to efficiencies in N fertilizer application and decreased ground water pollution. In this study, we digitized aerial color photographic transparencies using an eight‐bit scheme to generate digital counts for the red, green, and blue primary colors in the photographs at the R5 growth stage and related them to grain yield. Digital count responses were relative to the N treatment in which grain yield plateaued. Experiments were conducted in 1992 and 1993 for four irrigated corn hybrids with five N rates on a 6‐ha field near Shelton, NE. Red and green digital counts relative to those for the high N treatment provided better prediction of yield response than relative blue counts in both years. In 1993, black‐and‐white photographs taken with a filter centered around 536 nm also predicted yield response to N well (r2 = 0.93). These findings permit the use of low cost aerial photographs to characterize variability in crop N status throughout entire fields.
Canopy Architecture and Morphology of Switchgrass Populations Differing in Forage Yield
Authors: Redfearn Daren D. , Moore Kenneth J. , Vogel Kenneth P. , Waller Steven S. , Mitchell Robert B. 
Published: July 2010

AbstractPhenotypic selection has been used to improve forage yield and in vitro dry matter disappearance (IVDMD), but the effects on canopy architecture and morphology are not understood. Our objectives were to determine if canopy architecture and morphology can explain genotype × environment (G ✕ E) yield differences in switchgrass (Panicum virgatum L.) and to evaluate canopy architecture and morphology as selection criteria for increasing yield. This study was conducted in 1993 near Mead, NE, and near Ames, IA. The experimental design was a randomized complete block experiment with a split‐plot arrangement of four replicates at each location. Whole plots were tiller population and subplots were sward maturity. Tiller populations were harvested on 9 June, 19 July, and 27 August at Ames and on 10 June, 27 July, and 26 August at Mead and were classified morphologically. Tillers were separated into primary yield components and dried at 55°C to determine total forage yield and dry matter contribution of morphological components. Genotype × environment interactions occurred for total forage yield and tiller density. Previous phenotypic selection for increased forage yield and IVDMD apparently altered morphological changes within the canopy of selected switchgrass populations. The most apparent changes were development of additional collared leaves and internodes in some populations across locations. Although canopy architecture may not be a useful selection criterion because of variability associated with individual canopy traits, indirect measurements showed that leaf area index (LAI) has some potential as a selection criterion for increasing total forage yield. However, selection for individual canopy traits may be most effective for modifying sward growth habits.
Using a Chlorophyll Meter to Estimate Specific Leaf Nitrogen of Tropical Maize during Vegetative Growth
Authors: Chapman Scott C. , Barreto Hector J. 
Published: July 2010

AbstractChlorophyll meters are used as a quick, inexpensive method of estimating leaf N concentration in both experiments and production fields. Direct use of the meter readings is complicated by effects of crop age and cultivar on leaf N concentration, at least partly due to variation in leaf thickness. Research in rice (Oryza sativa L.) shows that readings can be adjusted to account for these effects, and this study sought to establish whether similar relationships exist for tropical maize (Zea mays L.). Additionally, we examined several aspects of sampling methodology. In several field trials in Mexico in 1994 and at different stages of growth (6, 8, 14 leaves expanded) and for plots with different N treatments (0 N, 21 cultivars; 150 kg N h−1, 7 cultivars), meter readings were taken from five leaves per plot, with five readings near the middle of the leaf blade. Leaf N concentration (g N kg−1 dry matter) was significantly linearly correlated with the meter readings (y = 1.46x − 30.68, r2 = 0.81), but the coefficients of fit differed greatly across data sets and growth stages. Adjusting the meter readings by dividing by specific leaf weight (SLW, g leaf m−2 leaf) resulted in an improved fit within and across data sets (y = 33.47x − 6.55, r2 = 0.97). The meter readings were also directly correlated with specific leaf N (SLN, g N m−2 leaf) (y = 0.387x − 0.476, r2 = 0.92) with no adjustments. Analysis of sampling patterns determined that at least four leaves per plot are needed, with several observations per leaf, and that readings should be taken at a point lying between about 40 and 70% along the leaf length from the leaf base. For scientists and farmers with limited direct access to laboratory analysis for N, the meter provides a cheap and convenient estimate of leaf N per unit leaf area during vegetative growth.
Phasic Development of Rice Seedlings
Authors: Salam Moin U. , Jones James W. , Jones John G. W. 
Published: July 2010

AbstractA better understanding of growth and developmental processes of rice (Oryza sativa L.) seedlings is necessary for crop management and modeling perspectives. This experiment was conducted to identify preautotrophic phases of rice seedlings, quantify seed dry matter mobilization and utilization, characterize dry matter partitioning during early growth, and observe if these processes are affected by cultivar and seed size. Seeds of two cultivars, each separated into two seed sizes, were sown in a greenhouse using field soil, and observations on seed weight loss and seedling weight gain were recorded daily for 27 d. The durations of heterotrophic and transition phases were determined as 74 and 247 thermal units (base temperature 9°C), respectively. Seeds lost 0.79 ± 0.010 g g−1 during the preautotrophic phases, while 0.42 ± 0.023 g g−1 seed weight accumulated in the seedling. Partitioning of dry matter was equal between root and shoot up to 37 thermal units, then allocation to root reduced curvilinearly until a constant root‐to‐shoot ratio (15:85) was reached at 148 thermal units and maintained thereafter. Shoot dry matter partitioning between culm and leaf was almost equal throughout the experiment except for the initial 37 thermal units when all dry matter accumulated in the culm. Early developmental processes in rice seedlings were independent of cultivar and seed size in this study. Although seed dry matter loss in proportion to the initial seed dry matter was significantly higher for larger seeds, the utilization pattern remained unaffected by seed size. This indicates that larger seeds were less efficient than smaller seeds in the utilization of reserves.
Bowen‐Ratio Comparisons with Lysimeter Evapotranspiration
Authors: Prueger John H. , Hatfield Jerry L. , Aase J. Kristian , Pikul Joseph L. 
Published: July 2010

AbstractWater use in agriculture by different cropping systems is of interest in determining crop water use efficiency of different tillage practices that will lead to reduced crop production risk. Lysimeters are considered the standard for evapotranspiration (ET) measurements; however, these units are often not replicated and are few in number at any given location. Our objective was to determine if a simple Bowenratio system with nonexchanging psychrometers could provide accurate measurements of ET from lentil (Lens culinaris Medikus) in a semiarid climate. The study was conducted in 1993 and 1994 on two adjacent 180‐ by 180‐m fields with weighing lysimeters (1.68 by 1.68 by 1.83 m) located in the center of each field, on a Williams loam (fine‐loamy, mixed Typic Argiboroll) soil near Sidney, MT. A Bowen‐ratio system comprised of two nonexchanging psychrometers and anemometers at 0.25 and 1.25 m above the plant canopy surface was placed in the lentil field along with a net radiometer and soil heat flux plate. Precipitation during the growing season from planting to swathing was 367 mm in 1993 and 227 mm in 1994. In 1993, soil water content of the lysimeter was greater than the field after large precipitation events around Day of Year (DOY) 210, even though the lysimeter was drained. After this time, the lysimeter ET exceeded that measured by the Bowen‐ratio system. Agreement was closer in 1994, when precipitation was near normal and there was no excess soil water in the lysimeter. Cumulative ET totals from the lysimeter were reflective of the seasonal precipitation patterns. Differences between the lysimeter and Bowen‐ratio occurred when there was excess precipitation and inadequate drainage from the lysimeter. Halfhourly ET fluxes from lysimeter and Bowen‐ratio values agreed to within 10% throughout the season. Bowen‐ratio systems with nonexchanging psychrometers can provide satisfactory estimates of daily and seasonal ET and can be used to estimate ET in semiarid climates.