bluuebunny/crossref_metadata_2025 huggingface dataset:
Stochastic Simulation of Daily Climatic Data for Agronomic Models1
Authors: Larsen G. A. , Pense R. B.
Published: July 2010

Many 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

Low 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

Soybean [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

Knowledge 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

Multiple 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

In 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

Crimson 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 grown

This 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

Yield 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

Though 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

Accurate 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

Visual 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

Soil 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.
Environmental Influences on Yield and In Vitro True Digestibility of Warm‐Season Perennial Grasses and the Relationships to Fiber Components1
Authors: Henderson M. S. , Robinson D. L.
Published: July 2010

In recent years climatic fluctuations have been increasingly associated with seasonal variation in yield and quality of forage crops. Although considerable information is available concerning environmental influences on yield and quality of many temperate and tropical grasses, very little is known about these relationships in the major grasses grown in the southern U.S.A. The objectives of this study were to determine the relative influences of temperature (T) and photon flux density (L) on dry matter yield (DMY) and in vitro true digestibility (IVD) of four warm‐season perennial grasses grown at two soil moisture levels and to relate the differences in IVD to fiber component concentrations. Coastal and common hermudagrass [Cynodon dactylon (L.) Pers.], Pensacola hahiagrass (Paspalurn notatum Flugge), and dallisgrass (P. dilatatum Poir.) were grown in an artificial growth medium at 4 day/night temperatures (35/24, 32/21, 29/18, 26/15 C), four photon Aux densities (1,050, 840, 630, 420 µEm−2 sec−1 PAR) and two soil moisture levels in growth cabinets. After 14 and 21 days regrowth, DMY and IVD were measured. Regression equations were developed to predict DMY and IVD as functions of T and L at each soil moisture level and regrowth period.

The study clearly showed that DMY of all grasses increased with increasing T and L. The imposed moisture stress sharply reduced DMY of dallisgrass (DAL) hut not of the other grasses. In all grasses IVD consistently decreased as T increased, resulting in maximum IVD at the lowest T. The effect of L on IVD ranged from positive to negative, depending on the grass and T. Maximum IVD values occurred at the high soil moisture (HM) level after 14 days regrowth. At the HM level maximum IVD of Coastal bermudagrass (COA), common hermudagrass (COM), and Pensacolabahia grass (BAH), respectively, was 5.7, 4.9, and 3.6 percentage units higher after 14 than after 21 days regrowth. In DAL at the HM level and in all grasses at the low soil moisture level, these differences due to age were only about one percentage unit or less. The Paspalum spp. averaged about seven percentage units higher in IVD than the Cynodon spp. Significant (P ≤ 0.01) negative correlations were obtained between IVD and previously reported concentrations of acid detergent fiber (ADF), cellulose, permaganate lignin (LIG), and silica in all grasses and concentrations of neutral‐detergent fiber in COA and COM. Although correlation coefficients were ≤ 0.50, hemicellulose concentration and IVD were positively correlated in all grasses. Strongest correlations were obtained between IVD and concentrations of ADF and LIG.
Effect of Irrigation and Row Spacing on Soybean Water Use1
Authors: Reicosky D. C. , Rowse H. R. , Mason W. K. , Taylor H. M.
Published: July 2010

A better understanding of the soil‐water plant spacing interactions as they affect water‐use efficiency and crop yields requires the development of satisfactory methods for determining water use.

The objective of this work was to determine the effect of 25− and 100‐cm row spacings on crop water use under irrigated and nonirrigated soybeans [Glycine max (L.) Merr.] on a fine, silty, mixed (calcareous) mesic family of Typic Udorthents soil.

Water use was evaluated by measuring evapotranspiration and soil water extraction. Evapotranspiration (ET) was measured using a portable chamber that utilized psychrometric techniques to determine changes in the water vapor density when the chamber enclosed the crop canopy and the soil surface. Soil water extraction (SYVE) was calculated from changes in gravimetric water content during periods without rainfall and then corrected for the flow of water at the bottom of the root zone.

Irrigation resulted in the expected higher water use rates on both row spacings. The row spacing effect early in the season was related to the leaf area index (LAI). Early in the season, the 25‐cm irrigated treatment had a slightly higher ET than the 100‐cm irrigated treatment. Later in the season, row spacing effects were not evident. The two methods employed for evaluating crop water use showed only fair agreement.
Date of Seeding, Fall Growth, and Winter Survival of Winter Wheat and Rye
Authors: Fowler D. B.
Published: July 2010

In the northern part of the North American Great Plains the level of cultivar winterhardiness required for winter cereal production is extremely high. Therefore, for successful production in this area close attention must be paid to all factors that influence a plant's ability to attain maximum winterhardiness. In this study, the influence of date of seeding on fall growth and winter survival of winter wheat (Triticum aestivum L.) and rye (Secale cereale L.) was assessed in seven trials grown on udic and typic boroll soils in the northcentral part of the agricultural area of Saskatchewan. In these trials, four wheat and two rye cultivars were seeded at 2 week intervals between 1 August and 15 October in each of 3 years. During this period, rye accumulated shoot dry matter at twice the rate of wheat. However, as expected, a decrease in shoot dry weight of both wheat and rye occurred with each succeeding delay in seeding date. The only meaningful winter damage that was observed in the rye was for the last two seeding dates with ‘Cougar’. The effect of date of seeding on survival of wheat was not consistent among trials. However, average survival was highest for the 15 August and 1 September seeding dates. This was 4 to 6 weeks prior to the onset of fall conditions favorable for cold acclimation. Differences in survival among wheat cultivars were not influenced by seeding date. This allowed for utilization of the Field Survival Index to evaluate the relative effects of suboptimal seeding dates on winter survival potential of cultivars. These results demonstrate that the Field Survival Index can be used to evaluate the effects of certain management practices in addition to inherent cultivar potential on winter survival.
Effect of P and K on Yield and Chemical Composition of Forage Sorghum1
Authors: Reneau R. B. , Jones G. D. , Friedericks James B.
Published: July 2010

Even though P and K are both essential nutrients, the response of agronomic crops to P/K interaction under field conditions has not been adequately documented. This research was conducted to examine the influence of a high and low level of P over a wide range of K levels and vice versa on yield and chemical composition of forage sorghum (Sorghum bicolor L.). In Exp. I, K was applied at rates of 0, 56, 112, and 244 kg/ha and split with P application of 0 and 116 kg/ha. For Exp. II, P was applied at rates of 0,29,58, and 116 kg/ha. For Exp. II, P was applied at rates of 0, 29, 58, and 116 kg/ha and was split with K applications of 0 and 224 kg/ha. These studies were conducted from 1978 thru 1980 on a Davidson clay (Rhodic Paleudult: clayey, kaolinitic, thermic) soil. Potassium application (Exp. I) increased yields only in years with less than optimum moisture conditions and then only when P was applied. When no P was applied, yields decreased with increased K application. Phosphorus (Exp. II) increased yields for each of the 3 years studied. In years with less than optimum moisture conditions, application of K increased yields at the higher P levels. Tissue K concentrations increased with K application while Ca and Mg concentrations decreased with increased K application. However, when P was applied Ca and Mg concentration increased. In the absence of applied P, the decreased in Ca and Mg concentration was related to competition with K for uptake. This competition may be responsible for reduced yields when K application was increased in the absence of applied P. When P was applied (in the presence or absence of applied K), Ca and Mg concentration increased in the tissue. A linear relationship between yield and Mg concentration in the tissue was present.
Crop Yield – Irrigation Relationships in a Gypsiferous‐Sodic Soil1
Authors: Russo David
Published: July 2010

The effect of irrigation regime on the soil‐water suction, the salinity of the soil solution, and the yields of tomato (Lycopersicum esculantum var. 675) and bell pepper (Capsicum frutescens var. ‘Maor’) in a gypsiferous‐sodic soil was studied. For each of the two crops, three different amounts of water (in terms of pan evaporation) at two different irrigation frequencies (daily irrigation and irrigation every 3 days) were applied. The different irrigation regimes resulted in different soil water suction and salinity profiles, each of which can be characterized by a time average and the variance about this average. Average (over time) soil water potential (ψ) increased as both the amount of irrigation water (Q′) and the irrigation frequency (I) increased. For a given I, the ψ‐Q′ relationships can be described by a hyperbolic function. In the gypsiferous‐sodic soil used, the salinity of the soil solution was highly correlated with the exchangeable Na of the soil, which, in turn, was reduced with added irrigation water. Relative yields, Y, of the two crops were linearly dependent on the variance of the soil‐water potential, independent of the irrigation regime. This implies that the yield‐soil‐water potential relationship can be described by a quadratic function. As opposed to the unique Y‐ψ relationships, the Y‐Q′ relationships depend on the irrigation frequency. For a given Q′ yields of both crops obtained under daily irrigation were higher than the yields obtained under irrigation once in 3 days. Highest fruit yields were 126.1 Mg/ha of tomatoes and 62.7 Mg/ha of bell pepper; the respective amounts of irrigation water were 1,013 and 2,164 mm (109%) and 160% of the evaporation from a Class A pan).
Bermudagrass, Tall Fescue, and Orchardgrass Pasture Combinations with Clover or N Fertilization for Grazing Steers. I. Forage Growth and Consumption, and Animal Performance1,2
Authors: McLaren J. B. , Carlisle R. J. , Fribourg H. A. , Bryan J. M.
Published: July 2010

Information on pasture productivity and forage quality of various adapted species and combinations that support rapid animal gains is needed for successfully backgrounding yearling steers in the humid southeastern USA prior to feedlot placement. To evaluate productivity and quality of pasture combinations for growing beef steers, a grazing experiment was conducted near Memphis, Tenn., in 1975 to 1977 on a Typic Hapludalf. The 1.2 ha pastures were Midland (Cynodon dactylon (L.) Pers.) + (Trifolium repens L.) clover, Midland + N, 1/3 Midland + N plus 2/3 fescue (Festuca arundinacea Schreb.) + N in separate pastures, Midland overseeded with fescue + N, common (C. dactylon var. dactylon) + N, fescue + clover, and orchardgrass (Dactylis glomerata L.) + clover (OG + clo). Nitrogen was applied at 224 kg ha−1 y−1 on bermudagrass and at 67 kg ha−1 y−1 on fescue. Pastures were grazed using a modified put−and−take system maintaining orchardgrass at 7 to 14 cm high and the other grasses at 5 to 8 cm. Forage growth and consumption were determined by the cage−and−strip method. Yearling steers weighing 230 kg in the spring grazed 123 to 150 days; they were weighed at 21−day intervals and visual estimates of species composition were made at that time. Forage yield was 8.3 t/ha for Midland + fescue and ranged between 4.0 and 5.7 t/ha for the other treatments. Estimated forage consumption was 80% or more of the forage growth. Forage crude protein (122 to 152 g/kg) was sufficient for meeting the minimum requirements for growing 250− to 300−kg steers. Stocking rates were between 4 and 6 steers/ha. Average daily gains were about 475 to 575 g for all treatments, except for OG + clo (825 g/day). Pasture productivity ranged between 520 animal grazing days/ha for OG + clo to 1190 for Midland + fescue. The productivity of the other pastures was between 730 and 880 grazing days/ha. Daily forage dry matter (DM) intake was 5 to 7 kg/steer. Steers grazing OG + clo, fescue + clover, and Midland + N pastures had feed efficiencies of about 9 kg DM/kg gain; steers on the other treatments required 11 to 13 kg DM/ kg gain. Beef production was 321, 339, 375, 400, 416, 424, and 593 kg/ha for fescue + clover, common + N, 1/3 Midland − 2/3 fescue, Midland + clover, OG + clo, Midland + N, and Midland + fescue, respectively.
Relationship of Runoff and Soil Loss to Ground Cover of Native and Reclaimed Grazing Land1
Authors: Hofmann L. , Ries R. E. , Gilley J. E.
Published: July 2010

Vegetation cover is a dominant factor in controlling runoff and water erosion from agricultural land and an important criterion for determining adequate reclamation of strip−mined land. A simulated rainfall study was conducted near Center, N.D. to determine the relationship of ground cover factors to runoff and soil loss. The point frame technique was used to estimate vegetation cover as measured by either the first contact (first hit) of the sliding pins with live vegetation, litter, or bare soil and rock or by a similar contact of the sliding pins at the soil surface (surface hit). Artificial rainfall was applied at the rate of 46 mm/h to 4.0 × 22.1 m runoff plots located on 9 to 12% slopes within reclaimed and unmined pastures. Reclaimed treatments were ungrazed or grazed at light, moderate, or heavy intensity plus vegetation and litter removed by burning. Native range treatments were ungrazed, closely grazed, and burned. Native ungrazed plots had greater live surface cover than ungrazed or lightly grazed reclaimed plots but similar soil loss, runoff, and soil loss/runoff ratio (SL/RO). Best fit techniques revealed some cover factors linearly related to soil loss, runoff, and SL/RO; others logarithmically related. Live surface cover estimates were poorly related to runoff and soil loss. Adequacy of soil protection can be best estimated by percentage of bare soil. Runoff or soil loss estimates were similar whether total cover was estimated by surface hits or first hits; however, surface hits were easier to determine in tall vegetation under windy conditions. The point frame technique is satisfactory for estimating whether the cover is adequate to maintain soil stability on reclaimed land or native range. Its use can be extended to estimate ground cover in other erosion studies.
The Photoperiod Sensitive Interval in Maize1
Authors: Kiniry J. R. , Ritchie J. T. , Musser R. L. , Flint E. P. , Iwig W. C.
Published: July 2010

In order to apply photoperiodic response functions developed in controlled environments to field grown maize (Zea mays L.), the timing of photoperiod sensitivity must be known. The timing of photoperiod sensitivity is also necessary for defining effective photoperiods for determining the effect of latitude and planting date on development of photoperiod‐ sensitive maize cultivars. The objective of this study was to determine the time when maize is sensitive to photoperiod. Two photoperiod sensitive cultivars of maize were grown in controlled environment chambers at the Duke Univ. Phytotron in photoperiods of 10, 12.5, 15, and 17.5 h. A third cultivar was grown in 12.5 and 17.5 h photoperiods. Plants were moved at different times between chambers having different photoperiods. Time from seedling emergence to tassel emergence was recorded. The length of this development interval was compared to the same interval for control plants that remained in a constant photoperiod for the entire time. The timing of photoperiod sensitivity was determined by knowing when the plants were moved and assessing which photoperiod affected them. Plants were insensitive to photoperiod immediately after seedling emergence. They remained insensitive until 4 to 8 days prior to the date of tassel initiation in short photoperiods. The insensitive, juvenile phase, therefore ended at least 4 days prior to tassel initiation in short photoperiods. The sensitivity continued until tassel initiation or shortly thereafter. The photoperiod affecting development in the field, considering the slow rate of change of photoperiod, is the value at the time of tassel initiation.
Mycorrhizae Effects on Plant Growth, Phosphorus Uptake, and N2(C2H4) Fixation in Two Alfalfa Populations1
Authors: Satterlee Larry , Melton Bill , McCaslin Bob , Miller Don
Published: July 2010

Alkaline soils of the southwestern USA often affect phosphorus nutrition of crop plants, decreasing yield and N2‐fixation potential of alfalfa (Medicago sativa L.). The objective of this study was to determine the relationships among P fertilization, mycorrhizae inoculation, and alfalfa populations on plant growth, P concentrations in the tissue, and N2 (C2H4) fixation rate. The experiment was a pot study conducted in a shadehouse during the summer months. Soil was a Glendale clay fineloamy, mixed thermic Typic Torrifluvent with a pH of 8.5, a water extractable P level of 0.06 ppm, and sodium bicarbonate extractable P level of 5.9 ppm.

Amounts of top growth and P concentration in the forage were influenced by the interactions of alfalfa populations with P fertilization levels, and the presence or absence of mycorrhizae inoculation. The unselected alfalfa population (N0) did not increase in top growth when fertilized with P but did increase in top growth when inoculated with mycorrhizae. Phosphorus concentration in the top growth of the unselected population was highest when both fertilized with P and inoculated with mycorrhizae. The selected alfalfa population (N3) increased in top growth and P concentration in the foliage when fertilized with P. Inoculation with mycorrhizae in this population produced no significant effects. None of the treatments affected N2 (C2H4 fixation rates. The results indicated some beneficial effects on alfalfa growth and P concentration in the top growth could be expected from both mycorrhizae inoculation and P fertilization in this soil, but the effect depended on genetic factors in the plants.
Corn Growth Response to Temperature and Photoperiod. III. Leaf Number1
Authors: Warrington I. J. , Kanemasu E. T.
Published: July 2010

The number of leaves formed on a determinate plant species such as corn (Zea mays L.) is dependent on the time between sowing and tassel initiation and on the rate of leaf production at the apical meristem. Both of these processes, and consequently leaf number, are influenced by environmental variables such as temperature and photoperiod. In a controlled‐environment study of two corn hybrids, grown over a wide range of temperature regimes from 16/6 to 38/33°C day/night, a nonlinear leaf number/temperature response was observed. Leaf number was lowest near 18/18° C and highest in the 16/6 and in the 38/33°C conditions. Because of this nonlinearity, leaf numbers observed under differential day/night temperature regimes were sometimes quite different from those observed under constant day/night temperatures but with identical mean temperatures. A leaf number/temperature response function was estimated for each of the hybrids which could be used to predict leaf number for various temperature regimes with 12‐h photoperiods. The response function was found to be in agreement with results in the literature. Differences in leaf number between the two cultivars were consistent with their maturity ranking. Leaf number increased as photoperiod increased; an average increase of 0.71 leaves per additional hour of photoperiod was found. This increase obtained under high light conditions is greater than that recorded previously for other temperate cultivars grown under long day conditions provided by low intensity day‐length extensions from incandescent lighting. Photoperiod sensitivity was not altered by temperature. The number of unexpanded leaves present at tassel initiation was almost constant under different temperature treatments despite changes in total leaf number. In contrast, this number increased when photoperiod was increased. The main ear node position altered with changes in total leaf number but was almost constant relative to the number of mature leaves present at tassel initiation under all temperature and photoperiod treatments.
Response of Soybean Cultivars to Irrigation of a Clay Soil1
Authors: Heatherly Larry G.
Published: July 2010

Numerous investigations have shown that soybeans [Glycine max (L.) Merr.] will give a significant yield response to irrigation, especially when the supplemental water is applied during reproductive development. However, the majority of these results have been obtained with soils ranging in texture from silt loam to sandy loam. Since soybeans are frequently grown on finer‐textured soils, we conducted field experiments in 1979 and 1980 on Sharkey clay (Vertic Haplaquept, very‐fine, montmorillonitic, thermic), a soil representative of that occurring in about 3 750 000 ha of the alluvial plain of the Mississippi River. Variables included initiation of furrow irrigation at the prebloom (V), beginning of bloom (BL), beginning of pod set (PS), and beginning of pod fill (PF) stages, plus a nonirrigated (NI) treatment, and three cultivars representing Maturity Groups V (‘Bedford’), VI (‘Tracy’), and VII (‘Bragg’). Data were collected for seed yield, mature plant height, lodging, xylem pressure potential, leaf area, and seasonal soil moisture status. In the ‘wet’ year of 1979, yields from irrigated Bedford and Tracy were not significantly greater than the respective NI yields of 2754 and 3368 kg ha−1. The PF treatment of Bragg produced a yield of 3630 kg ha−1, however, and this was significantly higher than the yields of all other treatments of Bragg, as well as all treatments of Bedford. In the dry year of 1980, all irrigation treatments of all cultivars increased yields above the NI treatment, although the PF treatment yields were only about one‐half of those from PB or BL treatments, which were nearly equal. Seed yield was highest from Bragg and lowest from Bedford in all cases. Lodging was not significantly affected by any irrigation treatment. Mature plant height was significantly increased only in the BL treatment of Bedford in 1980. Measurements of xylem pressure potential, leaf area, and soil water potential in 1980 indicated that the NI plots were severely stressed; thus, response to irrigation should have been expected. These results show that irrigation of soybeans growing in a clay soil should be initiated at or near bloom in a dry year, and at any period of stress during reproductive development in a “wet” year.
Central Appalachian Hill Land Pasture Evaluation Using Cows and Calves. II. Comparison of Animal Days per Hectare Calculations with Statistical Evaluation1
Authors: Burns J. C. , Harvey R. W. , Giesbrecht F. G. , Linnerud A. C.
Published: July 2010

In grazing experiments using variable stocking (put‐and‐take method), animal days ha−1 (from which gain ha−1 is computed) is calculated using the total digestible nutrient (TDN) method. This method has been satisfactorily applied to yearling cattle but not widely used when the tester unit is complicated by two animal types as with the cow‐calf unit. This study uses cow‐calf data from a 6‐year unbalanced grazing trial and compares two methods of computing animal days ha−1 and associated gain ha−1. One method was the TDN procedure consisting of two types of calculations: 1) the standard procedure, using tester animal seasonal mean TDN (SMT) factors, and 2) the calculation of tester animal period mean TDN (PMT) factors. The second method was based on mean tester body live weights computed three ways: 1) converting all weights to a standard weight (453.5 kg) factor (STW); 2) calculating period mean weight (PMW) factors; and 3) calculating seasonal mean weight (SMW) factors. The five animal day calculations were compared for magnitude of year and field variance component and residual error. Relative and absolute values of treatment means were examined. The relative rank of the year and field variance components were generally similar among the five ways of calculating animal days ha−1 and associated gain ha−1. A consistent difference was larger residual error for STW and PMT but smallest for the SMT calculation. The SMT animal days (standard used) and gain ha−1 were highly correlated with STW, PMW, and SMW (r ranged from 0.95**, significant at the 0.01 level of probability to 0.99**) but somewhat lower for PMT (r ranged from 0.82** to 0.88**). Absolute values (both days ha−1 and gain ha−1) from the SMT, PMW, and SMW calculations were very similar, while PMT values were variable and STW values greatly inflated. Results using the SMW and PMW calculations would be very similar to SMT values with little precision lost through increased variance. The use of live weight factors (PMW or SMW) in determining animal days ha−1 is much simpler and requires fewer assumptions than the TDN calcuations.