bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stochastic Simulation of Daily Climatic Data for Agronomic Models1
Authors: Larsen G. A. , Pense R. B. 
Published: July 2010

AbstractMany agronomic models require the input of daily climatic data. Simulated climatic data may be used when long series of historic data are not available or convenient, or when future data are needed. A stochastic weather simulation model was developed and validated for a wide range of climates. The model produces possible daily sequences of precipitation amount, maximum and minimum air temperature, and total solar radiation at the earth's surface for the entire year.A first‐order, two‐state Markov chain is used to simulate the occurrence of wet and dry days. Probabilities are used to simulate the occurrence of trace precipitation amounts on wet days. A two‐parameter gamma distribution conditioned by the precipitation status on the previous day is used to generate greater than trace amounts. Two bivariate normal distributions conditioned by the precipitation status on the current day are used to simulate current temperature deviations from long‐term average temperature curves. A two‐parameter gamma distribution simulates current solar radiation deviations from the calculated maximum clear day radiation on dry days. On wet days, the deviations are simulated with a two‐parameter beta distribution.The model was developed with data from Columbia, Mo. Model validation was done for Columbia, Albuquerque, N.M., Caribou, Maine, Medford, Ore., and Miami, Fla. Various statistical tests were done to detect significant differences in central tendency, dispersion, and distribution. Comparisons were made to the base period used for parameter estimation (ranged from 16 to 20 years) and also to the 80‐year period of record available at Columbia. The validation showed that the model produced climatic data which generally did not differ significantly from the base period at any of the locations. At Columbia, it was determined that the 17‐year base period was not long enough to adequately represent the 80 years of precipitation data.
Bodie Bean Responses to Changes in Plant Density1
Authors: Brathwaite Richard A. I. 
Published: July 2010

AbstractLow yielding vining types of bodie bean [Vigna unguiculata (L.) Walp. syn. V. sinensis] are traditionally grown throughout the Commonwealth Caribbean for their green immature pods. To increase productivity and profitability of this nutritionally important cowpea an erect bush cultivar was recently introduced, but it is frequently cultivated at highly variable plant densities, contributing to low yields. The objective of this study was to determine the effects of plant density at thinning of 63, 74, 88, 111, 148, 222, and 444 thousand plants/ha (TPH) in 45 cm rows on the yield and quality of marketable green immature pods of ‘Los Baños Bush Sitao No. 1’ bodie bean when grown under weed‐free conditions during the rainy season. The experiment was established during 1975, 1977, and 1978 on a River Estate sandy loam (Fluventic Eutropept) at Valsayn and a Cunupia silty clay loam (Aquic Eutropept) near Piarco in Trinidad. Although differences occurred in seasonal precipitation between the two locations, response of the different plant parameters to density was generally similar. Increasing plant density increased the yield while the weight and numbers of pods/plant decreased as density increased. The number of pods/plant was the yield component most affected by the plant density. Pod size was reduced by density increments of 148 to 444 TPH. Plant density did not affect the days to 50% flowering or maturity, pod length, plant height or show evidence of density‐induced mortality, but slightly decreased the number of branches/plant. Pod moisutre content was slightly reduced by plant densities of 222 and 444 TPH, but the grading quality of the pods and their fiber and protein contents were unaffected. The results indicate that high yields of good quality pods can be obtained from increased plant density, and in a weed‐free environment a density of 148 TPH in 45 cm rows would result in a significant yield advantage to bodie bean growers.
Effect of Freezing Temperatures during Soybean Seed Maturation on Seed Quality1
Authors: Judd R. , TeKrony D. M. , Egli D. B. , White G. M. 
Published: July 2010

AbstractSoybean [Glycine max (L.) Merr.] seed produced from late maturing cultivars or following delayed planting of early maturing cultivars is often exposed to frost prior to maturation and harvest. Since little information is available regarding the effect of freezing temperatures on seed germination, freezing experiments were conducted with intact plants, and detached pods in controlled environmental chambers. Pods at three developmental stages (green, yellow, and brown) were exposed to temperatures of −2 to −12 C for up to 32 hours. There was a curvilinear relationship (R2 = 0.94) between seed moisture and the freezing temperature of seed with the freezing point decreasing from −2 C at a moisture percentage of 68% (green pods) to −20 C at 30% moisture (brown pods).Seed exposed in detached pods supercooled 2 to 5 C below the freezing point temperature at all development stages. Immature seed in green pods exposed on the plant froze at their freezing point (−2 C); however, seed in yellow or brown pods exposed on the plant supercooled 2 to 4 C below their freezing point. Seed injury did not occur when the seed remained in the supercooled state; however, ice formation resulted in seed injury and death.Immature soybean seed in green pods (65% moisture) were not injured by freezing temperatures of approximately −2 C; however, seed in yellow pods (physiological maturity, 55% moisture) showed significant reductions in seed germination and vigor following an 8‐hour exposure at −7 C. Germination of seed in brown pods (approximately 35% moisture) was reduced only by exposure to −12 C. These results indicate that the temperature required to cause freezing injury to soybean seed decreases during seed development and maturation. When soybean seed have reached physiological maturity (maximum dry weight) temperatures substantially below 0 C are required to cause injury.
Yields of Warm‐ and Cool‐Season Forages on Adjacent Soils1
Authors: Fribourg Henry A. , Carlisle Rick J. , Reich V. H. 
Published: July 2010

AbstractKnowledge of average yields that can be expected over a period of years for a soil mapping unit helps in the use of soil survey information. Even the most recent soil surveys must rely on estimates from experiments and experience. For yields of principal crops these estimates are adjusted for the effects of soil‐water relationships and often must be extrapolated to similar soils for which no data are available. The objective of this study was to determine the yield on adjacent soils varying primarily in their moisture‐supplying capacity and natural drainage, of adapted perennial and annual warm and cool‐season forages and small grains grown under the same general climatic influence and management.The yields of 12 forage crops that grow mostly from spring to autumn were measured for 5 years on five adjacent soils with similar aspect. Later, eight winter small grain cultivars were grown for hay and grain for 3 and 4 years, respectively, on the same sites. The soils used belong to the Eutrochrepts, Hapludults, Paleudults, Fragiudults, and Ochraquults great groups.The soils were characterized in terms of their yield for each crop, ranging from 1,035 to 5,735 kg/ha for the warm‐season crops and from 2,225 to 6,760 kg/ha dry matter for the cool‐season forages. Since the many forage crops adapted to the landscape studied have different periods of growth and can satisfy different animal nutritional needs in different forage systems, no attempt was made to compare species within each soil studied. However, the data presented will help in soil selection for crops needed within specific forage systems on the landscape.
Influence of Tillage Practices on the Fertility Status of an Acid Soil Double‐Cropped to Wheat and Soybeans1
Authors: Hargrove W. L. , Reid J. T. , Touchton J. T. , Gallaher R. N. 
Published: July 2010

AbstractMultiple cropping in conjunction with various minimum tillage practices is currently a conspicuous agricultural production method in the southeastern U.S. The objective of this study was to determine the influence of 5 years of various tillage practices on the fertility status of an Ultisol continuously double‐cropped to wheat (Triticum aestivum L.) and soybeans (Glycine max L.). The tillage treatments for each fall/spring were: no‐tillage/no‐tillage, harrow/ho‐tillage, conventional tillage/no‐tillage, no‐tillage/conventional tillage, harrow/conventional tillage, conventional tillage/conventional tillage. With no‐tillage, soil pH decreased more rapidly with depth than with conventional tillage treatments. Accumulations of Ca, Mg, P, Mn, and Zn occurred in the surface soil with no‐tillage treatments, but surface soil K was lower with no‐tillage compared to conventional tillage treatments. Organic C and N did not accumulate in the soil surface under no‐tillage to the degree reported in other studies. Results indicate that continuous no‐tillage results in increased nutrient concentrations in the surface soil with a rapid decrease with depth, while conventional tillage resulted in a more homogeneous soil with respect to soil fertility status
Response of Maize to Cold Stress During Vegetative Growth1
Authors: Landi P. , Crosbie T. M. 
Published: July 2010

AbstractIn several maize (Zea mays L.) growing regions, sudden, shortterm decreases in temperature may occur when plants are in early vegetative growth stages. Limited research has been reported, however, on the effects of short periods of cold stress during early vegetative stages on subsequent growth and development. Consequently, we studied responses of inbreds A619, B14A, B37, and FR4A to 3/8, 5/10, and 7/12 C night/day temperatures administered for 72 hours at three vegetative growth stages in a growth chamber. Distinct genotypic responses to temperature stress were observed. Seedling growth of B14A was reduced by about 50% by 3/8 and 5/10 C temperatures compared to control plants under constant 10/16 C night/day temperatures. The 3/8 C treatment caused a significant increase in heat units required for B14A to reach the pollen shedding stage of development. These traits were not affected by cold treatments for A619 and B37.A second experiment with B14A, B37, and their single cross hybrid (B14A ✕ B37) was performed with a 72‐hour, 3/8 C temperature treatment imposed at the third‐leaf stage. Treated plants of inbred B14A produced significantly less shoot, root, and total plant dry weight/heat unit than did control plants grown constantly at 10/16 C night/day temperatures. Inbred B37 was not affected by temperature treatments, and the B14A ✕ B37 single cross exhibited a dominant phenotype for tolerance to cold stress. We concluded that maize response to short‐term temperature stress is under genetic control.
Vetch and Clover Overseeded on a Bahiagrass Sod1
Authors: Dunavin L. S. 
Published: July 2010

AbstractCrimson clover (Trifolium incarnatum L.) and arrowleaf clover (T. vesiculosum Savi) have been used rather widely for cool‐season pastures including overseeding on warm‐season perennial grass sods. It would be advantageous, in the event of a shortage of seed of the two clovers, to have alternate legumes which could extend the grazing period or increase the quality of the succeeding grass forage. The release of four new vetch (Vicia sativa L.) cultivars has provided new sources of legumes with potential for use as cool‐season forages overseeded on warm‐season grass sods. This study compares these new vetches with ‘Dixie’ crimson clover and with ‘Yuchi’ arrowleaf clover in a 2‐year field experiment on a 12‐year‐old established ‘Tifhi‐1’ bahiagrass (Paspalum notatum Flugge) sod on a Fuquay fine sandy loam (Plinthic Paleudult). Yields of dry forage, crude protein (CP) from grass and legumes, and digestible organic matter (DOM) from grass were determined. Crimson clover yielded significantly more legume forage than arrowleaf clover and both clovers outproduced the vetches over the 2‐year period. ‘Cahaba White’ vetch and ‘Vantage’ vetch produced higher yields than ‘Nova II’ vetch while legume yields of ‘Vanguard’ vetch were intermediate. The yield of bahiagrass forage was generally 0.8 to 1.7 metric tons/ha greater following any legume than where no legume was grown. Bahiagrass yields over the 2‐year period following Vantage, Cahaba White and Nova II vetch were equal to that following Dixie crimson clover. The total combined yield of grass and legume forage was greatest where crimson clover was grown and least where no legume was grown.The yield of DOM from bahiagrass for the 2‐year total was greatest following either Dixie crimson clover, Vantage vetch, or Cahaba White vetch and lowest where no legume was grown. Dixie crimson clover and Yuchi arrowleaf clover produced similar and significantly greater yields of CP from legume forage than did any of the vetches over the 2‐year study period. Consequently, the combined total yield of CP from legume and bahiagrass forage for the 2‐year period was greatest where either Dixie crimson clover or Yuchi arrowleaf clover was grownThis study shows that while the four vetches studied may be reasonable substitutes for crimson or arrowleaf clover for overseeding on bahiagrass sod, combined forage dry matter yields are likely to be somewhat lower and CP yields significantly lower compared to that obtained with the clover. In general, Vantage and Cahaba White vetch appear to be better substitutes than either Nova II or Vanguard vetch.
Simulating Alfalfa Weevil Effects by Defoliation1
Authors: Fick Gary W. 
Published: July 2010

AbstractYield loss assessment and the economic evaluation of pest control practices require an understanding of how pests affect crops. Hand removal of alfalfa (Medicago saliva L.) leaflets to simulate insect defoliation was used (a) to compare simulated and natural defoliation by the alfalfa weevil (Hypera postica Gyllenhal), (b) to relate yield reduction to the amount of leaf mass removed, and (c) to determine the effect of defoliation on subsequent shoot growth. Leaflets were removed during a period of 11 days to simulate the pattern of alfalfa weevil defoliation. In two experiments, greenhouse‐grown plants were defoliated starting at the first‐bud and first‐flower stages of development, respectively. Defoliation treatments removed all leaflets within 5, 15, or 30 cm of the growing tip by the end of the defoliation period, simulating feeding of about 3, 6, and 11 larvae/stem, respectively. Recovery growth was followed for up to 5 weeks after the end of defoliation.Simulated insect defoliation reduced yield, delayed maturation, reduced stem lengths, and increased axillary branching (for the 5‐cm treatment only) similar to effects observed in the field. The concentrations of crude protein and digestible nutrients were only slightly influenced by simulated defoliation. At the end of defoliation, the yield of residual alfalfa herbage was inversely proportional to the extent of defoliation (P ≤ 0.01). The mass of the removed leaflets did not fully account for the yield reduction, but the relationship between extent of defoliation and the sum of the residual herbage and the removed leaflets was not statistically significant. Growth rates following the end of defoliation were not influenced by defoliation treatment. The data indicate that hand removal of alfalfa leaflets simulates defoliation by the alfalfa weevil if defoliation is extended over a period of days. Such treatment neither inhibited nor stimulated growth following defoliation.
Response of Drip‐Irrigated Sugarcane to Drought Stress1
Authors: Koehler P. H. , Moore P. H. , Jones C. A. , Dela Cruz A. , Maretzki A. 
Published: July 2010

AbstractThough drip irrigation is used on more than half of the irrigated sugarcane (Saccharum spp. hybrid) in Hawaii, the effects of drought stress on the growth and yield of drip‐irrigated sugarcane has not been investigated extensively. This study reports the effects of a single period of drought stress on the growth and metabolism of cultivar H62‐4671 during vegetative growth in drip‐irrigated fields during the 1st year of a normal 2‐year crop in five fields at Kekaha Sugar Company, Kauai, Hawaii. The plants ranged from 5.4 to 9.8 months of age at the beginning of the experiment.Water depletion from the soil profile, leaf water potential (ψΙ), leaf solute potential (ψΠ), leaf pressure potential (ψρ), stalk elongation, plant sugar, K, and amino acid concentrations were monitored at 1200 to 1400 hour during a 5‐ or 6‐week period of drought stress. In three of four fields, soil water extraction was limited by low soil water content after cumulative profile water depletion of approximately 120 mm.Stalk elongation was strongly correlated to ψΙ and cumulative soil water depletion. Stalk elongation of plants in drought‐stressed plots was less than 80%' that of plants in well‐watered plots after only 50 mm of cumulative soil water depletion. During drought the concentrations of potassium and reducing sugars in the leaf blade increased, but the concentrations of sucrose and free amino acids changed little. None of these metabolites changed in the stem apex.The results indicate that a serious reduction in stalk elongation occurs prior to a reduction in the rate of soil water depletion, a change in the false‐color infrared signature of the canopy, or large changes in ψΙ, ψΠ, leaf and meristem sugar, K, and amino acid concentrations. The results emphasize the importance of maintaining normal imgation intervals with drip‐irrigated sugarcane cv. H62‐4671.
An Experimental Study of Net Radiation, Its Components and Prediction1
Authors: Weiss Albert 
Published: July 2010

AbstractAccurate estimates of net radiation may be preferable to a direct measurement with a net pyrradiometer, due to sensor cost and maintenance requirements, for certain long‐term applications such as irrigation scheduling. Thus, the objective of this study was to investigate methods of estimating net radiation from readily available meteorological measurements and in the process, to study each component of net radiation.Simultaneous measurements of incoming and outgoing solar and longwave radiation, net radiation, air temperture, and vapor pressure were made over a well watered alfalfa (Medicago sativa L.) crop at the Scottsbluff Agricultural Laboratory of the Univ. of Nebraska Panhandle Station. Air temperature, used in the Stefan‐Boltzmann equation, was a good predictor of daily outgoing longwave radiation. Calculation of incoming longwave radiation using three values of atmospheric emisivity (Idso and Jackson, 1969; Brutsaert, 1975; Idso, 1980) overestimated measurements. Two procedures to calculate daily values of net radiation are outlined and tested on independent data. One method uses two emisivities, one for clear sky and one for cloudy conditions. The second method uses only one emissivity and is more straight forward. Calculation of net radiation from incoming solar radiation, air temperature, and vapor pressure by both methods compares quite well to measured values, r = 0.98 for each method.
Soybean Growth over and between Subsoil Channels on Two Loamy Sands1
Authors: Batchelor J. T. , Keisling T. C. 
Published: July 2010

AbstractVisual differences in soybean [Glycine max (L.) Merr.] growth have been observed in dry years where soybeans were grown on loamy sands in Arkansas that had been subsoiled at right angles to the row. Because of this observation, soybeans were grown over and between subsoil channels to characterized soybean development as affected by the distance soybeans were planted from a subsoil channel. A Crevasse loamy sand (a mixed, thermic Typic Udipsamments) and a Steele loamy sand (a sandy over clayey, mixed, nonacid, thermic Aquic Udifluvents) were subsoiled to an approximate depth of 35 cm at right angles to the row (cross‐subsoiled) with subsoil shanks spaced at 97 cm and planted with soybeans. Plant height, total dry weight, and seed yield were measured on soybeans that were grown over the subsoil channel and at two distances between channels at 20 sites on each soil. Plant height, total dry weight, and seed yield declined with distance from the subsoil channel. Soybeans with poorest growth were located at the midpoint between subsoil channels. The decline in soybean growth with distance from the subsoil channel was attributed to reduction in traffic pan destruction as the distance from the subsoil channel increased.
Kentucky Bluegrass Growth and Water Use Under Different Soil Compaction and Irrigation Regimes1
Authors: O'Neil K. J. , Carrow R. N. 
Published: July 2010

AbstractSoil compaction and efficient use of irrigation water are important concerns of turfgrass managers. This field study examined effects of soil compaction on growth and water utilization of a cool‐season turfgrass species under different irrigation programs.A 2‐year‐old stand of Poa pratensis L., ‘Baron,’ on a fine, montmorillonitic mesic Aquic Arguidoll soil, was subjected to four treatments resulting from a factorial design with two levels of compaction (none and 30 passes per week with roller) and two levels of irrigation (set schedule of 3.8 cm water per week plus rainfall and 3.8 cm when tensiometer at 10 cm depth read −0.70 bar).Soil compaction had no effect on root weight or distribution. Visual quality, shoot density, verdure, and percent total cover were reduced by compaction while total nonstructural carbohydrates (TNC) were unaffected. In the surface 3 cm of soil, compaction increased bulk density and moisture retention but reduced aeration porosity at −0.1 bar from 18.1 to 12.5%. Irrigation treatment had no effect on any of the soil physical properties.Without affecting turf quality, water use with tensiometer was reduced by 28 and 48% on noncompacted and compacted areas, respectively, compared to set‐schedule irrigated plots. Water use over a 9‐day period in August indicated that the turf grown under the tensiometer scheduled regime was physiologically or anatomically adapted to use less water even when it was available. This adaptation was not due to differences in vegetative or root growth in this study.Compaction reduced water use by 20% over the 4 month study. During a 9‐day period in August, compaction reduced water use by 3.5 to 11% for the tensiometer and set‐scheduled treatments, respectively. This response appeared to be due primarily to altered moisture retention properties and reduced shoot growth. Thus, compacted and noncompacted sites should be irrigated on separate schedules.