bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial and Temporal Variability of Transplanted Rice at the Field Scale
Authors: Dobermann Achim , Pampolino Mirasol F. , Neue Heinz‐Ulrich 
Published: July 2010

AbstractMeasuring rice (Oryza sativa L.) growth in farmers' fields requires plant sampling techniques that take account of spatial and temporal variability. Our objective was to specify sampling recommendations for transplanted rice at the field scale. Rice was grown in two fields, fertilized and not, at 20‐ by 20‐cm hill spacings. Plant height, tiller number per hill, dry matter yield, and foliage area index were measured during the growth period at 8 locations and harvest samples were taken at 56 locations per field. Variation was low for plant height at all growth stages (CV = 6.1–9.5%); tiller number varied more (CV = 21–33%), especially in the tillering stage. Variation at harvest was intermediate (CV = 12–21%) for most crop variables. Grain yield ranged from 2.41 to 5.88 t ha−1 for the unfertilized field and 4.54 to 8.82 t ha−1 for the fertilized field. Transplanting errors introduced variation among hills. Variation between quadrats within a field was due to varying growth rates between tillering and panicle initiation (PI) and was related to the spatial distribution of inherent soil nutrient availability and fertilizer nutrient supply. Nonhomogeneous topdressed application of N caused location‐specific microvariation in crop stands. At all growth stages, two samples of three randomly selected hills were sufficient to measure plant height in a field. Increasing the number of samples had more effect on the precision of tiller number estimates than did increasing the size of the sampling unit. To measure tiller number between tillering and PI of rice, sampling units of five hills should be used and samples should be collected from 12 to 19 quadrats. At flowering, seven samples are enough. Harvest estimates of agronomic characters should be based on 8 to 12 quadrats when 10‐hill sampling units are used. A stratified random sampling design should be used, and samples should be taken >3 m apart.
Evaluation of the Aphid‐Day Standard as a Predictor of Yield Loss Caused by Cereal Aphids
Authors: Kieckhefer Robert W. , Gellner Jeffrey L. , Riedell Walter E. 
Published: July 2010

AbstractAccurate prediction of yield loss caused by cereal aphids in small grains involves assessment of the aphid population density on plants, the duration of their feeding, and the growth stage of the crop at the time of feeding. In this research, aphid‐day (one aphid feeding on one plant for 24 h) unitage was used as a standard to compare the effects of feeding by greenbug, Schizaphis graminum (Rondani), Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko), and bird cherry‐oat aphid (BCO), Rhopalosiphum padi (L.), on the growth and yield of spring wheat, Triticum aestivum L., to measure the degree of additivity of yield loss caused by aphid feeding on the same plants at several stages of plant growth, and to evaluate the adequacy of the aphid‐day standard as a predictor of yield loss. Results of greenhouse experiments with a scaled series of aphid‐day components (150 aphids ✕ 2 d; 75 ✕ 4 d; 50 ✕ 6 d; 25 ✕ 12 d) of equal total value (300 aphid‐days) showed that the three aphid species were similarly damaging to yield but that for RWA and BCO the 25 ✕ 12 d combination was significantly (P ≤ 0.01) more damaging than the other aphid‐day treatments for those species. The administration of escalating aphid‐day dosages to plants concomitant with advancing plant growth stages (two‐leaf, 300 aphid‐days; four‐leaf, 400 aphid‐days; two‐leaf + four‐leaf, 700 aphid‐days; boot, 1200 aphid‐days; two‐leaf + boot, 1500 aphid‐days; milk, 200 aphid‐days; two‐leaf + milk, 2300 aphid‐days) revealed that yield loss caused by aphid feeding at two plant growth stages was usually significantly (P ≤ 0.01) greater than that at a single stage, but was not fully additive simply as the arithmetic sum of the yield losses at the two stages. Yield losses due to aphid feeding (expressed as milligrams per 100 aphid‐days) declined precipitously with advancing plant growth stage. These results show that the aphid‐day unitage, properly interpreted in relation to the aphid species involved and the growth stage of the crop, is a useful predictor of grain yield loss at harvest. Relating cumulative aphid‐days at successive plant growth stages to ultimate yield loss enables producers to make informed decisions about the need for and timing of rescue chemical treatments.
Carbon Dioxide and Temperature Effects on Pima Cotton Development
Authors: Reddy K. Raja , Hodges Harry F. , McKinion James M. 
Published: July 2010

AbstractPredicting plant responses to changing atmospheric CO2 and to the possible global warming are important concerns. Effects of CO2 on developmental events are poorly documented, as is the interaction of CO2 and other major climate variables on crop development. The objective of this experiment was to determine the effects of an altered CO2 environment and interactions of CO2 and temperature on pima cotton developmental rates. Pima cotton (Gossypium barbadense L. cv. S‐6) was grown from seed in sun‐lit plant growth chambers. Air temperatures were controlled from 20/12 to 40/32°C (day/night) in 5‐degree increments. Daytime CO2 was maintained at 350 or 700 μL L−1. In a second experiment, the temperature was maintained at 30/22°C day/night and the plants were grown in 350, 450, or 700 μL L−1 CO2. Days required to develop nodes on the mainstem, days from emergence to first square, number of vegetative and fruiting branches, number of fruiting sites produced, number of bolls and squares produced, and number of bolls and squares retained by the plants were determined. Rates of mainstem node formation and the time required to produce the first square and first flower were not sensitive to atmospheric CO2, but were very sensitive to temperature. Prefruiting branch nodal positions required longer to develop than nodes with fruiting branches. Carbon dioxide levels did not affect the time required to produce nodes. Number of branches produced was sensitive to both temperature and CO2. The larger number of bolls set on the lower branches of plants grown at high CO2 provided a larger sink for photosynthate than plants grown at low CO2. This may be the reason for the observed reduction in number of fruit at the upper nodes of high‐CO2‐grown plants. More bolls and squares were produced and retained on plants grown in high‐CO2 environments, except that none were produced in either CO2 environment at 40/32°C. Our results indicate that high‐temperature‐tolerant cotton cultivars would be more productive in the present‐day CO2 world, and they would be essential in the future if global temperature increases.
Defoliation Effects on ‘Mott’ Elephantgrass Productivity and Leaf Percentage
Authors: Chaparro C. J. , Sollenberger Lynn E. , Jones C. S. 
Published: July 2010

Abstract‘Mott’ elephantgrass (Pennisetum purpureum Schum.) is a high‐quality pasture grass for the tropics and subtropics, but information is needed on growth responses of Mott to clipping management. In 1989, 1990, and 1991, a study was conducted on a hyperthermic, uncoated Aquic Quart‐zipsamment soil to measure Mott herbage dry matter (DM) harvested and plant‐part percentage (1989 and 1990 only) responses to clipping. The study included all 16 treatment combinations of four defoliation heights (10‐, 22‐, 34‐, and 46‐cm stubble) and four defoliation frequencies (3, 6, 9, and 12 wk). Treatments were replicated three times in a randomized block design. Data were analyzed by fitting multiple regression equations starting with a second‐order polynomial model. In 1989, total DM harvested ranged from 8.0 to 16.2 Mg ha−1 and increased (decreasing rate) as defoliation height was lowered and increased linearly as weeks between harvests increased from 3 to 12. The range of total DM harvested was 4.2 to 11.6 Mg ha‐~ in 1990 and 2.6 to 16.1 Mg ha−1 in 1991. Dry matter harvested in 1990 and 1991 increased (decreasing rate) as defoliation height was lowered from 46 to 10 cm and as interval between defoliations increased. Lowest total DM harvested in the third year was observed using a 3‐wk defoliation frequency, 10‐cm defoliation height treatment, a result of reduced plant vigor. Greatest total DM harvested in all years occurred using a 12‐wk frequency, 10‐cm height treatment. Across all treatments, live lamina percentage in total DM harvested ranged from 63 to 100% and was greatest for the 3‐wk frequency, 46‐cm height treatment. Live lamina DM harvested was not affected by treatment in 1989, but in 1990 maximum values were estimated to occur when frequency was 9 to 10 wk and stubble height was 15 to 20 cm. We conclude that Mott elephantgrass is productive and maintains a high leaf lamina percentage over a relatively wide range of defoliation treatments, but close, frequent clipping reduces total DM harvested.
Response of Carbon Metabolism to Night Temperature in Cotton
Authors: Warner Donn A. , Holaday A. Scott , Burke John J. 
Published: July 2010

AbstractCotton (Gossypium hirsutum L.) is sensitive to low temperatures during all phases of growth. Throughout the cotton growing season on the High Plains of Texas, days provide optimal sunlight and temperature for metabolism followed by nights with temperatures of 15 to 20°C, well below the optimum. The present growth chamber study compared the response of specific components of C metabolism in vegetative cotton grown with 28°C/28°C and 28°C/20°C day/night regimes. Photosynthesis for cool‐night (20°C) plants measured at 28°C the following day was only 77% of 28°C night plants. Less starch accumulation occurred during the day in the cool‐night plants, yet their predawn starch levels were approximately 2.5‐fold higher than the 28°C plants. Pools of triose phosphate and fructose 1,6‐bisphosphate were lower at night at 20°C than at 28°C. The glucose 6‐phosphate/fructose 6‐phosphate ratio was higher for the cool‐night plants, however, indicative of an apparent limitation in sucrose synthesis subsequent to cytosolic fructose 1,6‐bisphosphatase. The most interesting observation is the maintenance of equal sucrose pools in both treatments, even though the amount of starch catabolized at night was different. This study shows that cool night temperatures alone alter cotton C metabolism throughout each 24‐h period.
Utilization of Allelopathy for Weed Management in Agroecosystems
Authors: Weston Leslie A. 
Published: July 2010

AbstractBiorational alternatives are gaining increased attention for weed control because of concerns related to pesticide usage and dwindling numbers of labeled products, particularly for minor‐use crops. Allelopathy offers potential for biorational weed control through the production and release of allelochemics from leaves, flowers, seeds, stems, and roots of living or decomposing plant materials. Under appropriate conditions, allelochemics may be released in quantities suppressive to developing weed seedlings. Allelochemics often exhibit selectivity, similar to synthetic herbicides. Two main approaches have been investigated for allelopathic weed suppression. One is use of living rotational crops or mulches that interfere with the growth of surrounding weeds [e.g., tall red fescue, Festuca arundinacea Schreb.; creeping red fescue, F. rubra L. subsp. commutata; asparagus, Asparagus officinalis L. var. altilis); sorghum, Sorghum bicolor (L.) Moench; alfalfa, Medicago sativa L.; black mustard, Brassica nigra (L.) Koch; and oat, Avena sativa L.]. Attempts to select germplasm with enhanced suppressive ability have been limited. The second is use of cover crop residues or living mulches to suppress weed growth for variable lengths of time (e.g., winter rye, Secale cereale L.; winter wheat, Triticum aestivum L.; and sorghum). Cover crop residues may selectively provide weed suppression through their physical presence on the soil surface and by release of allelochemics or microbially altered allelochemics. The ability to understand the physiological basis for allelopathy in a crop plant may allow the weed scientist or ecologist to work closely with molecular biologists or traditional plant breeders to selectively enhance the traits responsible for weed suppression.
Forage Yield and Quality of Six Annual Medicago Species in the North‐Central USA
Authors: Zhu Yanping , Sheaffer Craig C. , Barnes Donald K. 
Published: July 2010

AbstractAnnual medics (Medicago spp.) have been extensively used as winter annual forage and green manure crops in Mediterranean regions, but their potential use in the north‐central USA has not been evaluated. Our objective was to determine the summer and fall forage yield and forage quality of spring‐ and summer‐seeded annual medics. Twelve commercial annual medic cultivars from Australia (representing five species) and ‘George’ black medic (M. lupulina L.), ‘Nitro’ alfalfa (M. sativa L.), and ‘Arlington’ red clover (Trifolium pratense L.) were seeded in spring and summer at Rosemount and Morris, MN, in 1991 and at St. Paul and Becker, MN, in 1992. Forage yields were taken at a single harvest in summer (when most medics were reproductive) from spring‐seeded stands and in the fall first frost (0°C) from summer‐seeded stands. Forage yields of spring and summer‐seeded annual medics ranged from 1.2 to 5.7 and 0.5 to 5.5 Mg ha−1, respectively, depending on location and species. Barrel medic (M. truncatula Gaertn.), snail medic [M. scutellata (L.) Mill.], and burr medic (M. polymorpha L.) cultivars were among the highest yielding, while Nitro alfalfa, George black medic, and Arlington red clover were consistently among the lowest yielding forage species. George black medic, Harbinger strand medic (M. littoralis Rohde ex Loisel.), and Kelson snail medic were among the highest in forage crude protein (CP) concentration for both summer and fall harvests. Forage fiber concentrations of all annual medics except Sava snail medic were equal to or lower than those in Nitro alfalfa. Our results indicate that annual medics have the potential for producing high yields of quality forage in the north‐central USA and might be used as short‐season annual crops for harvest in fall and summer when traditional forage supplies are inadequate.
Fall Harvest Management Effects on ‘Grasslands Matua’ Prairie Grass Quality
Authors: Hall Marvin H. , Jung Gerald A. , Shaffer John A. , Everhart John R. 
Published: July 2010

AbstractForage production of ‘Grasslands Matua’ prairie grass [Bromus catharticus M. Vahl; syn. B. unioloides Kunth, B. willdenowii Kunth] (Matua, for short) during the fall months is excellent, but highly management dependent. Unfortunately, fall harvest management effects on the quality of this grass are relatively unknown. Our objectives were to determine the effects of fall harvest management on forage quality of Matua prairie grass during the fall and following spring. Two field experiments were conducted on Hagerstown silt loam soil (fine, mixed, mesic Typic Hapludalfs). Experiment 1 addressed date of fall harvest and residual stubble height; Experiment 2 addressed frequency of fall harvest and residual stubble height effects on forage quality in the fall and spring. Delaying fall harvest of Matua prairie grass caused forage crude protein (CP) content to decline by about 30%; however, delaying fall harvest had no or little effect on acid‐detergent fiber (ADF), neutral‐detergent fiber (NDF), or in vitro dry matter digestibility (IVDMD). Grasslands Matua quality in the spring was unaffected or inconsistently affected by fall harvest management. Delaying harvest of Matua prairie grass in the spring reduced forage quality but not to the extent reported for other cool‐season forage grasses. Our findings indicate that Matua offers considerable latitude in fall and spring harvest management with regards to obtaining quality forage; however, these finding should be considered along with previous findings that fall harvest management has a large effect on winter survival of Matua.
A Design for a Modular, Generic Soil Simulator to Interface with Plant Models
Authors: Timlin Dennis , Pachepsky Yakov A. , Acock Basil 
Published: July 2010

AbstractThe various linkages in agricultural systems are so complex that research questions are often studied via simulation modeling. The development and upgrading of detailed models requires a large investment of time and resources; therefore, it is necessary to simplify the process of building the model and incorporating modifications as research finds new information to include. The goal of this study was to develop the framework for a generic soil simulator that could easily be modified and incorporated into crop models. Soil and root processes are represented by modules that interact on the spatial—temporal grid covering the soil profile and the simulated time interval. Data were divided into public and private components, to minimize information passing between modules. This modular structure and information hiding simplifies replacement or addition of modules and promotes code reuse. The classes of modules include (i) control modules that oversee interactions between processes, (ii) water, solute, heat, and gas transport modules, (iii) interphase chemical transformation modules, (iv) biochemical transformation modules, and (v) root growth and uptake modules. A representative simulator, 2DSOIL, was assembled according to the proposed design. Examples include the incorporation into a simple crop model and the expansion of 2DSOIL with a management module to simulate chemical application.
Biomass Production and Nitrogen Accumulation in Pea, Oat, and Vetch Green Manure Mixtures
Authors: Jannink Jean‐Luc , Liebman Matt , Merrick Laura C. 
Published: July 2010

AbstractInterest in the use of green manures has revived because of their role in improving soil quality and their beneficial N and non‐N rotation effects. This study evaluated biomass production, N content, radiation interception (RI), and radiation use efficiency (RUE) of pea (Pisum sativum L.), oat (Avena sativa L.), and hairy vetch (Vicia villosa Roth) mixtures. Treatments were a three‐way factorial of pea genotype (‘Century’ vs. ‘Tipu’), pea planting density (90 vs. 224 kg ha−1), and cropping mixture (solecropped pea vs. pea planted with a mixture of oat and hairy vetch). A mixture of oat and vetch without pea was also planted. Treatments were planted in early June on a Caribou gravelly loam (coarse‐loamy, mixed, frigid Typic Haplorthods) in Presque Isle, ME, in 1993 and 1994. Biomass production and radiation interception were measured by repeated sampling. Mixture biomass was affected by a year × pea density interaction: respective yields for mixtures containing low‐density and high‐density pea were 770 and 880 g m−2 in 1993 vs. 820 and 730 g m−2 in 1994. Mixture N content paralleled biomass production and averaged 20.9 g m−2 across all treatments. While pea sole crops did not consistently produce biomass or N equal to three‐species mixtures, the twospecies mixture of oat and vetch did, yielding 820 g m−2 of biomass and 21.7 g m−2 of N, averaged over the 2 yr. Multiple regression showed that 61% of the variability in mixture biomass production was accounted for by a combination of early‐season pea RI and midseason total mixture RUE. Economic analyses showed that rotations including these green manures may be economically competitive with a conventional rotation of barley (Hordeum vulgare L.) undersown with clover (Trifolium spp.) in a potato (Solanum tuberosum L.) production system.
Nitrogen Placement and Tillage Effects on Dry Matter and Nitrogen Accumulation and Redistribution in Winter Wheat
Authors: Rao Srinivas C. , Dao Thanh H. 
Published: July 2010

AbstractNitrogen losses observed with no‐till practices when N fertilizer is surface broadcast prompted the need to reassess N fertilizer management practices for winter wheat (Triticum aestivum L.). Field studies were conducted on Renfrow silt loam (fine‐silty, mixed, thermic Udertic Paleustolls) from 1990 through 1993 near El Reno, OK, to determine the effects of N placement and tillage on dry matter accumulation, N uptake, and N redistribution in winter wheat. Tillage methods were moldboard plowing and no‐till with standing stubble. Fertilizer (60 kg ha−1) treatments were surface broadcast (BR) the same day as seeding, banded (8 to 10 cm below the soil surface) below the seed row (BL), banded between the rows (BT), and no N (control). Fall and spring above‐ground dry matter and N were greater in plowed than in no‐till treatments when precipitation was similar to or above the 24‐yr average. Leaf N content was 8, 12, and 3% greater in BR, BL, and BT treatments, respectively, than in the control. Nitrogen accumulation rates (g m−2 d−1) in heads from anthesis to final harvest were 0.16 for BR, 0.17 for BL, 0.19 for BT, and 0.13 for the control. Final grain yield and grain N content were not affected by N placement in plowed plots. Under no‐till, grain yield was improved by 32% for BL and 15% for BT, and grain N content was increased by 33% for BL and 25% for BT as compared with the BR treatment.
Sensitivity of Phosphorus Uptake to Changes in Root Length and Soil Volume
Authors: Otani Takashi , Ae Noriharu 
Published: July 2010

AbstractRoot length is generally considered important in phosphorus uptake, but it is not known whether a crop with longer roots is always efficient in absorbing P from soils low in available P. Consequently, we investigated the relationships between P uptake and root length, as affected by soil volume, and soil P status. Field‐grown buckwheat (Fagopyrum esculentum Moench), castor (Ricinus communis L.), peanut (Arachis hypogaea L.), pigeonpea [Cajanus cajan (L.) Millsp.], sorghum [Sorghum bicolor (L.) Moench], and soybean [Glycine max (L.) Merr.] were compared in their ability to absorb P from soils with low and high P status. The relationships between root length, soil volume, and P uptake were then examined in pot‐grown buckwheat, peanut, and sorghum using varying pot sizes. Under field conditions, maximum P uptake was by sorghum, which produced the longest roots. A strong correlation (r = 0.85*) between root length and P uptake among crops was observed in high‐P soil, but not in low‐P soil. In pot culture, differences in P uptake were correlated to changes in soil volume rather than root density. Phosphorus uptake per unit soil weight was higher in peanut than in sorghum or buckwheat, especially in low‐P soil. Our results indicate that P uptake by crops is strongly correlated with root length in soils where P availability is high, but not in soils with low P availability, or where volume is limited. Results also suggest that peanut uses additional mechanisms beyond root length to increase P uptake.