bluuebunny/crossref_metadata_2025 huggingface dataset:
Freezing and Ice Tolerance Tests for Winter Brassica
Authors: Andrews C.J. , Morrison M.J.
Published: July 2010

Cold stress tolerances of winter brassicas (Brassica napus L., B. compestris L.) have frequently been reported from tests on leaves, without regard for the requirement of an intact crown meristem for overwinter survival. A method is described to determine the LD50 of washed, trimmed plants for freezing and ice encasement. Plants were cold hardened in controlled environment or in the field and tested at the five‐leaf stage. To determine freezing tolerance, units of five plants were sealed in polyethylene bags and survival determined of samples withdrawn during a 1 °C h−l programmed temperature decline. For ice encasement tolerance, units of five plants were sealed in ice in polyethylene beakers and survival determined after thawing at intervals during exposure to ‐1 °C. The LD50 was determined by interpolation or the Probit procedure. Significant separation of the cold stress tolerance of a number of cultivars of B. napus and B. campestris is presented.
Sufficiency Level and Diagnosis and Recommendation Integrated System Approaches for Evaluating the Nitrogen Status of Corn
Authors: Dara Syed T. , Fixen P. E. , Gelderman R. H.
Published: July 2010

An irrigated corn (Zea mays L., cv. Pioneer 3732) N fertilizer field experiment was conducted for 3 yr to compare plant analysis interpretation of N status by the diagnosis and recommendation integrated system (DRIS) and sufficiency level (SL) methods. Preplant soil NO3‐N was supplemented with ammonium nitrate to provide seven available N levels. Leaf samples were taken at the silking stage and analyzed for N, P, K, Ca, Mg, S, Mn, Zn, and Cu. Nutrient indices were calculated using published standard and locally‐developed (South Dakota) DRIS norms derived from 600 observations. At bighest grain yield, 11.86 Mg ha−1, the average soil NO3‐N level was 247 kg ha−1 over the 3‐yr test period, while check yields averaged 6.54 Mg ha−1 and required 68 kg N03‐N ha−1. The SL approach (using a critical ear leaf N concentration of 27.6 g kg−1) diagnosed N as inadequate even when excess N was applied, indicating that the N sufficiency level for irrigated corn is inflated and needs to be readjusted to 25.2 g N kg−1. Nitrogen indices calculated from the standard and local DRIS norms at 90% of maximum yield were −2 and 2, respectively. Regression of Nutrient Balance Indices against relative yield indicated greater variability in the standard norms than in the local norms. Our data suggest that the SL approach overestimated ear leaf N requirement, and that DRIS indices calculated using published standard norms were less useful than those from locally‐developed norms.
Quantification of Symbiotically Fixed Nitrogen in Soil Surrounding Alfalfa Roots and Nodules
Authors: Lory J. A. , Russelle M. P. , Heichel G. H.
Published: July 2010

Symbiotically fixed nitrogen (SFN) can be transferred from alfalfa (Medicago sativa L.) to intercropped nonlegumes and succeeding crops. Our objective was to quantify deposition of SFN from alfalfa roots and nodules to surrounding soil and to assess its significance in comparison to reported estimates of legume‐nonlegume N transfer. We quantified net loss of SFN to rhizosphere soil (i.e. rhizodeposition) at the end of one growing season under field and greenhouse conditions, using the 15N isotope dilution technique in soil that had been labeled with 15N 8 yr before initiation of the experiments. ‘Saranac’ and ‘Ineffective Saranac’ alfalfa were transplanted in the field into paired 0.75‐ by 1.0‐m microplots. In the greenhouse study these two alfalfas were grown separately in 15‐cm diam. by 90‐cm long polyvinylchloride tubes, four plants per tube. Plant organs were meticulously separated from soil at the end of one growing season. Soil adhering to roots and nodules was defined as rhizosphere and nodusphere soil, respectively, and was separated from the organs by 60 s sonication in 0.08 mol L−1 phosphate buffer. Symbiotically fixed N was quantified by comparing the atom % 15N of Saranac vs. Ineffective Saranac for each soil and plant N compartment. Harvested herbage contained 270 kg SFN ha−1 in the 135‐d field experiment and 55 mg SFN plant−1 in the 112‐d greenhouse experiment. Symbiotically fixed N was not uniformly distributed in the Saranac root system. Sampled rhizosphere soil contained no SFN in the field experiment and the equivalent of about 1 kg SFN ha−1 in the greenhouse experiment. Over one quarter of nodusphere soil N was apparently derived from SFN in both experiments, but amounted to less than 0.5 kg SFN ha−1 at the time of harvest. Nitrogen transfer to nonlegumes is often an order of magnitude larger than net deposition measured here. Thus it appears that rhizodeposition is a relatively small component of SFN loss from nodules and roots of alfalfa grown in monoculture.
Growth Chamber Modification to Emulate a Seed Germination Chamber
Authors: Springer T. L. , Tharel L. M.
Published: July 2010

In the absence of specialized research equipment, existing equipment often must be modified to meet research needs and objectives. Specialized germination chambers which control temperature, light, and humidity may not always be available to conduct detailed germination experiments. The objectives of this research were to modify a growth chamber to emulate a seed germination chamber and validate the system by reporting the variation in percentage seed germination and seedling root and shoot lengths. Modifications to the growth chamber consisted of mounting trays in space and adding cool humidified air. Within the modified growth chamber variation in seed germination was small for row or column placement on a tray and large between trays. Among the 11 trays, the optimum tray placement for seed germination was on Trays 4,5,6,7, and 8 for all species studied. Variation in seedling root and shoot lengths was attributed to row and column placement on a tray and tray levels, and was associated in part with light and temperature gradients in the modified growth chamber.
Dynamics of Soybean Growth in Variable Planting Patterns
Authors: Wells Randy
Published: July 2010

Reported soybean [Glycine max (L.) Merr.] yield responses to variable plant populations have been inconsistent. The varied responses are tied to the capacity of the plant stand to attain a minimal level of dry matter prior to reproductive growth. This study examined soybean growth expressed as functions of both plant and ground area to identify associations with yielding ability. Treatments consisted of high, medium, and low populations (approximately 21, 13, and 3 plants per square meter) at 0.96‐m row widths and a medium population (approximately 13 plants m−2) at 0.43‐m row widths for 2 yr. The values of total dry matter (TDM), stem DM, leaf DM, leaf area, height, and main stem node number were determined on both a whole plant and ground area basis. In addition, relative growth rate (RGR), relative leaf area growth rate (RLAGR) and net assimilation rate (NAR) were examined. Treatments with the greatest interplant space had the largest RGR, RLAGR, and NAR early in growth, thus resulting in compensation for reduced plant population. Decreases in plant DM at 91 DAP in response to increasing plant population were greater in 1988 than in 1989, and were related to poorer growing conditions in the latter year. The related TDM values were larger in 1988, with all treatments exhibiting a TDM above 500 g m−2 by early podfill (R5). In contrast, the TDM at 91 DAP of the wide row, low and medium population treatments was 300 and 426 g m−2, respectively in 1989. Seed yield differences were found in 1989 but not 1988. Differences among years and treatments concerning growth rates, plant DM, TDM, and seed yield emphasize the impact of limiting environmental factors on plant compensation in response to increased space.
Seed Production after Floret Removal from Sunflower Heads
Authors: Charlet L. D. , Miller J. F.
Published: July 2010

The banded sunflower moth (Cochylis hospes Walsingham; Lepidoptera: Cochylidae) is a pest of sunflower (Helianthus annuus L.) in the northern Great Plains. Larvae feed initially on sunflower florets and subsequently on immature and matue seeds (achenes). Our objective was to measure the compensatory ability of sunflower for increasing seed yield in response to the loss of florets caused by floret and seed feeding of the banded sunflower moth for the accurate computation of economic injury levels. Treatments were removal of floret at 10% increment intervals from 0 to 50% of the florets of sunflower heads (capitula) at flowering. Floret removal had a direct effect on the number of resulting fertile seeds. Reducing the number of florets by 10% resulted in a 20% decrease in the number of fertile seed, an 18% decrease in total seed weight of the head, and a 22% decrease in seed volume. Comparable decreases were found in the number of fertile seeds for other increments of floret removal. The sunflower plant can compensate for floret removal by increasing the weight of individual seeds. As percent of floret loss increased, seed weight increased, but even when only 10% of the florets were destroyed, the weight gain did not overcome the subsequent loss of seeds. Oil content of seeds significantly decreased as floret loss increased. In addition to consumption of mature seeds, simulation of damage showed that early feeding by banded sunflower moth larvae on florets can also directly and indirectly affect the final yield of infested plants.
Relationships between Soil Sulfate‐Sulfur and Seed Yields of Winter Rapeseed
Authors: Mahler R. L. , Murray G. A. , Swensen J. B.
Published: July 2010

Winter rapeseed (Brassica napus L.) has a higher S requirement than most currently grown cereals and legumes. The objectives of this study were to (i) determine the effect of S fertilization rates on winter rapeseed yields and oil composition, (ii) establish relationships between winter rapeseed yields and soil SO4‐S levels for three cultivars, and (iii) determine the optimum time and depth of soil sampling for S diagnosis. Field experiments were conducted on a S deficient Latahco silt loam (fine‐silty, mixed, frigid, argiaquic Xeric Argiaboll) and two S deficient Palouse silt loam (fine‐silty, mixed, mesic pachic Ultic Haploxeroll) soils for three growing seasons. Each factorial trial had three cultivars, three S rates, and four replications. Soil samples were collected from all plots to a depth of 120 cm and sectioned into six 15‐cm and one 30‐cm sample in October, April, and June for SO4‐S analysis. Winter rapeseed yield was correlated to soil SO4‐S at different sampling depths. Both ‘Bridger’ and ‘Cascade’ cultivars responded to S; however, no response was observed for ‘Dwarf Essex’. The most significant coefficient of determination values between soil SO4‐S and rapeseed yield (Bridger r = 0.82, P = 0.01; Cascade r = 0.79, P = 0.01) were obtained with a 75‐cm soil sample from the April sampling. By linear plateau regression, critical soil test SO4‐S levels for Bridger and Cascade were 45 and 51 kg SO4‐S ha−1, respectively. This research demonstrates the need to modify current soil sampling for S management in winter rapeseed production to reflect the need for an April sampling to a 75‐cm depth.
Root Development and Nitrogen Influx of Corn Genotypes Grown under Combined Drought and Nitrogen Stresses
Authors: Eghball Bahman , Maranville Jerry W.
Published: July 2010

Knowledge about the interactive effects of N and drought stresses on corn (Zea mays L.) root morphology and rate of N uptake is important for selecting drought tolerant and/or N efficient genotypes and for determining mechanisms that control root growth under stress. The objective was to study these interactions by growing three and four genotypes of known N utilization efficiency (NUE, kg grain/kg N uptake) responses in greenhouse and field experiments, respectively. Nitrogen application rates were 0, 30, 60, and 90 mg N kg−1 soil in the greenhouse and 0, 60, 120, and 180 kg N ha−1 in the field experiment. Water regimes included nonstress vs. an 8‐d water stress in the greenhouse experiment and dryland vs. irrigation in the field. Water‐regime‐by‐N‐rate interactions were not significant for root dry weight, length, average radius, root/shoot ratio, and N influx in either environment. Root weight and length were different among genotypes. The genotype with the greatest amount of roots deep in the soil had the highest grain yield increase with irrigation. Root mass and root length were greater, but mean N influx was two to three times smaller in the zero N treatment than in the applied N treatments (average of all genotypes). Severe water stress reduced corn root mass and length in the greenhouse. Moderate water stress in the field, however, significantly increased root length. Water use efficiency was positively correlated with root mass and length in the greenhouse. Water regime did not affect N influx in either experiment. These results showed that corn response to irrigation will be altered depending on root morphology, and that insofar as possible, the root system should be considered when selecting for N efficient and/or drought tolerant corn genotypes
Impact of Environmental and Harvest Management Variables on Alfalfa Forage Drying and Quality
Authors: Iwan J. M. , Shanahan J. F. , Smith D. H.
Published: July 2010

The objective of this study was to determine the impact of environment and harvest management variables on drying duration and quality of alfalfa (Medicago sativa L.) forage grown under semiarid conditions of the western USA. Untreated and conditioning agent (CA)‐treated forage was harvested with a commercial mower‐conditioner on four dates in 1989 to provide variation in drying duration. Drying duration was determined by periodically monitoring moisture concentration of the forage after harvest until the forage was baled at 180 g water kg−1 herbage. Samples from the bales of each harvest were taken to determine forage quality. Solar radiation, air temperature, air vapor pressure deficit (VPD), soil moisture, and windrow density were monitored during drying. To determine the effect of enviornmental and harvest management variables on drying, temperature‐ and VPD‐based models were used to predict forage moisture concentration at the end of several drying intervals. The VPD model included the variables of VPD, solar radiation, soil moisture, windrow density, and application of CA. The temperature model included of all the previous variables, except air temperature was substituted for VPD. The CA reduced drying duration by a maximum of 50% across the four harvests, with the greatest effect occuring under high solar radiation, temperature, and VPD. Crude protein was improved only slightly by the CA, with a maximum increase of 5.9% for the third harvest. Observed and predicted moisture concentration for several drying intervals closely agreed for both models (r2 = 0.80 for VPD, and 0.78 for temperature). These results suggest that manipulation of all variables included in the models should hasten alfalfa forage drying.
Stand Dynamics and Yield Components of Alfalfa as Affected by Phosphorus Fertility
Authors: Sanderson Matt A. , Jones Ronald M.
Published: July 2010

Stand maintenance of alfalfa (Medicago sativa L.) relies on the persistence of the original plants. Yield (yield per plant, yield per shoot) and stand components (plants per square meter, shoots per square meter, shoots per plant) were studied in two experiments designed to determine yield response to P on a low P soil (Windthorst fine sandy loam; fine, mixed, thermic, Udic Paleustalfs) near Stephenville, TX. Three preplant incorporated rates of P (0, 29, and 59 kg ha−1) and five annual surface broadcast rates of P (0, 7, 15, 29, 59 kg ha−1) were applied to two field experiments established in September 1988 and 1989. The experimental design was a split plot in four randomized blocks. Whole plots were incorporated P rates and subplots were annual broadcast P rates. Plants and shoots per square meter were counted 4 and 8 wk after planting in 1988 and 1989, at each harvest in 1989 and 1990, and at the beginning and end of the season in 1991. Relative distribution of root mass to a 90‐cm depth was determined in the fall of 1990 and 1991 for selected treatments. Phosphorus incorporated before planting increased alfalfa dry matter (DM) yields more efficiently than did broadcast P. Plant and shoot densities did not differ among treatments; thus, low yields at low P levels were a function of reduced yield per shoot. Delayed application of P on fall‐planted alfalfa did not affect plant density. Under 0‐P, root mass was concentrated in the upper 20 cm of soil, whereas under adequate to high P, more root mass was distributed throughout the upper 40 to 50 cm.
Endophyte Effects on Growth and Persistence of Tall Fescue along a Water‐Supply Gradient
Authors: West C. P. , Izekor E. , Turner K. E. , Elmi A. A.
Published: July 2010

Ecophysiology of the endophyte (Acremonium coenophialum Morgan‐Jones and Gams)‐tall fescue (Festuca arundinacea Schreb.) association needs to be understood in order to promote environmental fitness traits of the association while reducing its deleterious effects on ruminants. Our objective was to determine the influence of endophyte on drought stress tolerance, persistence, and yield components of field‐grown tall fescue on a Typic Hapludalfs soil. A water supply gradient was established during 1988 and 1989 with line‐source irrigation on established populations of 0 and 80% endophyte‐infected tall fescue. Whole plots consisted of endophyte infection status, across which a gradient of water was applied in a strip‐split fashion with eight replicates. Tiller population density and herbage yield were determined every 28 d and yield components were measured on selected dates. Relative to populations receiving high irrigation (375‐650 mm applied), tiller density in nonirrigated stands (0‐50 mm applied) from July to October 1988 was reduced an average of 42% in infected tall fescue and 55% in noninfected tall fescue. Tiller density of nonirrigated, infected populations recovered fully to that of high irrigation treatments by 17 November, whereas that of nonirrigated, endophyte‐free populations recovered to only 62% of irrigated treatments. The advantage in population density due to endophyte infection continued throughout 1989, a relatively wet year. A benefit in total forage yield due to endophyte infection was not consistently evident because of greater yield per tiller in endophyte‐free stands in 1989. Enhanced tiller density and survival were associated with endophyte infection during severe water deficit, and this advantage continued throughout the subsequent year. Endophyte infection confers population stability in tall fescue during drought stress through improved tiller and whole plant survival.
Rooting Depth and Dry Matter Development of Sunflower
Authors: Jaafar M. N. , Stone L. R. , Goodrum D. E.
Published: July 2010

The use of modeling and computers increases the potential to estimate crop water use and irrigation requirements. However, for that potential to be realized, data on root growth are needed for model development and/or input. Few field studies have included direct measurement of sunflower (Helianthus annuus L.) root development. Our objective was to examine plant development, with emphasis on rooting depth, of field‐grown sunflower. The study was in 1985 and 1986 near Manhattan, KS on deep, barrier‐free, Muir silt loam soil (fine‐silty, mixed, mesic Cumulic Haplustoll). Regression analysis was applied to data on root growth and aboveground development. The resulting equations were then used to examine growth patterns and rates of development. Canopy height reached its maximum of 2.40 m during the latter part of disk flowering. The maximum rate of height increase was 72 mm d−1 and occurred during early bud formation. Roots reached the deepest soil depth of 2.18 m late in the growing season (95% of the total of thermal units from emergence to physiological maturity). Roots reached 1.88 m at the beginning of disk flowering and 2.02 m at the completion of disk flowering. Rate of advance of the deepest observed root decreased linearly from 43 mm d−1 during mid June (eight leaves emerged). Green leaf area index (LAI) reached its maximum immediately prior to disk flowering. Dry mass of leaves, stems, and heads reached maximums at late disk flowering, back of head yellow with bracts still green, and physiological maturity (no green on head), respectively. Total aboveground dry mass reached its maximum at 85% of the total of thermal units from emergence to physiological maturity. The rate of total aboveground dry mass yield was greatest near mid season (48% of total thermal units). The data on sunflower rooting depth reported in this article will assist in estimation of crop water use.
Growth, Yield, and Quality of Forage Maize Under Different Nitrogen Management Practices
Authors: Cox W. J. , Kalonge S. , Cherney D. J. R. , Reid W. S.
Published: July 2010

Maize (Zea mays L.) forage producers need more information on how N management affects dry matter (DM) yield, forage quality, and residual soil NO−3 ‐N concentrations. Studies were conducted in New York to evaluate three hybrids under different sidedress N rates (0, 56, 140, and 255 kg N ha−1 at the V4 stage) and timing (70 + 70 kg N ha−1 at V4 and V8 and 75 + 75 + 75 kg N ha−1 at V4, V8, and R1 stages). The DM yields, which averaged 25% lower in 1991 (12.3 Mg ha−1) compared to 1990 (16.9 Mg ha−1), responded curvilinearly to N rates with maximum economic yields of 140 and 160 kg N ha−1, respectively. Whole‐plant neutral detergent fiber (NDF), acid detergent fiber (ADF), and N concentrations responded linearly to N rates in 1990 indicating that forage quality improved with each additional increment of N. Higher N rates, however, increased residual soil NO−3‐N concentrations in the upper 0.3 m soil depth in 1990 (0, 3, 30, and 32 mg kg−1) and 1991 (0, 0, 17, and 17 mg kg−1 for the 0, 56, 140, and 225 kg N treatments, respectively). Split‐N applications compared to respective single rate N applications did not increase DM yields, improve forage quality, or decrease residual soil NO−3‐N concentrations. When applying higher rates of N fertilizer, maize forage producers must balance potential benefits of higher DM yields and improved forage quality with the potential risk of increased residual soil NO−3‐N concentrations.
Penetration of Soybean Roots by Soybean Cyst Nematode at High Soil Water Potentlals
Authors: Johnson A. B. , Scott H. D. , Riggs R. D.
Published: July 2010

Soil water is an important factor in the movement and development of soybean cyst nematode (Heterodera glycines Ichinohe). Plant growth and soybean cyst nematode (SCN) population density were measured to determine the effects of soil water potential (Ψ8) on root penetration by SCN of ‘Essex’, a suspectible cultivar of soybean [Glycine max (L.) Merrill]. Soybean seeds were planted in growth containers and subjected to constant Ψ8 of −5, −10, −20, −30, −40, and −50 kPa at SCN levels of 12 000 eggs and second‐stage juveniles (J2) per kg soil or no SCN for the controls for 16 d. The soil used was a Captina slit loam (fine‐silty, mixed, mesic Typic Fragiudult) with 23, 68, and 9% sand, silt, and clay, respectively. Soybean was inoculated with eggs and J2 at the cotyledon growth stage (VC). Average soil temperature during the study was 25.5 °C. Leaf water potential (Ψ1) and soil oxygen diffusion rate (ODR) were significantly affected by Ψ8 < (P > 0.01) after 16 d of exposure to SCN. In the infested treatments Ψ1 was reduced at a more rapid rate with decreasing Ψ8 than in the non‐inoculated controls. The increase in SCN penetration of the soybean root system corresponded positively to the increase in soil ODR and corresponding decrease in Ψ8. Recovery of SCN from the soil decreased with a decrease in Ψ1. A mechanistic, nonlinear mathematical model was used to describe the relationship between Ψ8 and SCN penetration of soybean roots. A quadratic regression model was used to describe the relationship between Ψ8 and SCN recovery from the soil.
Sward Height and Vertical Morphological Differentiation Determine Cattle Bite Dimensions
Authors: Flores Enrique R. , Laca Emilio A. , Griggs Thomas C. , Demment Montague W.
Published: July 2010

To identify and quantify the influence of sward structure on the intake of grazing animals requires an understanding of sward‐animal interactions at the bite level. We tested the hypothesis that bite dimensions on vertically heterogeneous swards are determined by structural characteristics of the top leaf stratum, independent of those of a bottom layer of pseudostem or stem. Dallisgrass (Paspalum dilatatum Poir.) microswards were constructed by hand in a factorial combination of two lamina lengths (5 and 8 cm) and two sward heights 8 and 16 cm). Tillers consisted of a top segment of lamina and a bottom one of pseudostem (Exp. 1) or stem (Exp. 2) of length equal to the difference between sward height and lamina length. Treatments were replicated over three steers (Bos taurus) of 750 kg avg. body weight. Bite area and depth increased with sward height in swards with pseudostem but were not affected by lamina length. Pseudostems were not a barrier to defoliation and did not affect bite dimensions. Steers restricted grazing of tillers with stem to the upper lamina horizon. Bite depth was limited by stems only when lamina length was less than half of sward height. Bite area was reduced by the presence of stems because tillers bent at ligule height, restricting the animals to gather fewer tillers in each bite than when tillers bent at the base. Bite weight was reduced severely in swards with stem, relative to those with pseudostem. Results confirmed the importance of stem horizons and their relative positions in the sward as determinants of bite weight.
Growth, Boll Opening Rate, and Fiber Properties of Narrow‐Row Cotton
Authors: Heitholt James J. , Pettigrew William T. , Meredith William R.
Published: July 2010

Row spacing has the potential to affect agronomic traits of upland cotton (Gossypium hirsutum L.). Although narrow‐rows can pose numerous management challenges (e.g., cultivation and harvesting), the benefits of narrow‐rows may justify their use. Unfortunately, the extent and consistency of cotton's response to narrow‐rows is variable, which makes management decisions more difficult. The objective of this study was to determine whether row spacing affected the earliness (date at which 65% of the lint was on open bolls), fiber properties, and vegetative dry matter of normal‐leaf and okra‐leaf cotton. In 1989 and 1990, an okra‐leaf genotype and its normal‐leaf isoline were grown in field experiments on a Bosket fine sandy loam, using 0.5‐ and 1.0‐ m row spacings in early and late plantings each year. During midand late‐bloom, the vegetative dry matter was determined. At maturity, seed cotton in open bolls was picked at approximately 10‐d intervals, ginned, and earliness (date when 65% of total lint was on open bolls) calculated. Okra‐leaf grown in 0.5‐m rows reached 65% open 3 d earlier than okra‐leaf grown in 1.0‐m rows in the early planting of 1990. Otherwise, earliness was not affected by row spacing. Except for a small increase in the 2.5% span length of normalleaf grown in 1.0‐m rows above that in 0.5‐m rows, the other fiber properties, vegetative dry matter, vertical boll distribution, and average seed mass were unaffected by row spacing. Since many agronomic traits were unaffected by row spacing, management practices (e.g. date of defoliation) of narrow‐rows might be expected to similar be to that of conventional rows.
Agronomic Practices that Affect Corn Kernel Characteristics
Authors: Ahmadi M. , Wiebold W. J. , Beuerlein J. E. , Eckert D. J. , Schoper J.
Published: July 2010

Agronomic practices affect corn (Zea mays L.) grain yield and may affect physical and chemical characteristics of corn kernels. These characteristics affect feed, food, and industrial uses of corn grain. Four field experiments consisting of planting date and population combinations were conducted to determine the effect of these agronomic practices on grain yield, kernel N concentration, and kernel hardness. Kernel hardness was estimated by kernel weight, kernel density, and grinding resistance. A fixed ear hybrid, B73 × LH38, was used in all four experiments. Two of the four experiments also included LH119 × LH51, a flexible ear hybrid. Planting date affected yield in only one experiment. In this instance, delaying planting 4 wk decreased yield 55%. Yield reduction from planting delay was greater for B73 × LH38 than for LH119 × LH51. In two experiments, increasing population increased yield quadratrically; whereas, in the other two experiments the effect of population on yield was linear. No interaction between hybrid and population occurred. Delayed planting increased kernel N concentration in one experiment. In all four experiments, increasing population resulted in a linear decrease in kernel N concentration. Few effects from either planting date or population on kernel weight and density were found. Grinding resistance was increased by delayed planting in one experiment but was not affected by plant population in any of the four experiments. Inverse relationships between yield and important kernel physical and chemical characteristics were found. Emphasis on high yield may result in less desirable grain. End‐users that require high grain quality may need to provide incentives to growers.
Residual Effects of Soil Profile Modification on Water Infiltration, Bulk Density, and Wheat Yield
Authors: Unger Paul W.
Published: July 2010

Fine‐textured soils of the Southern High Plains, of which Pullman (fine, mixed, thermic Torrertic Paleustolls) is the dominant series,/ have inherently low water infiltration rates. Pullman soils have a moderately permeable surface horizon overlying and slowly‐permeable Bt horizon, which limits deep water penetration, thus hampering water conservation efforts and reducing water‐use efficiencies for crop production. In 1964, Pullman clay loam was profile‐modified (PM) to 0.9‐ and 1.5‐m depths. The objective of the 1990–1991 study was to compare soil bulk density (Db), water infiltration, plant available water (PAW) content, and winter wheat (Triticum aestivum L.) yield on PM and unmodified soil. Soil Db values were similar near the surface, but decreased with increasing depth of PM at depths greater than 0.3 m, except for the deepest increment (1.50–1.80 m), were Db values were 1.56 Mg m−3 for all treatments. Time required for 240 mm of applied water to infiltrate was 28.6 h on unmodified soil, and 8.4 h with 0.9‐ m and 6.3 h with 1.5‐m PM. The PAW contents in October and March were significantly greater for the mean and at some depths in PM plots than in unmodified plots. The differences were attributed to greater evaporative losses from the unmodified soil. After wheat harvest in June, mean PAW contents were not significantly different, but water extraction occurred to greater depths on modified than on unmodified soil Wheat grain yields tended to increase with PM (2.81 Mg ha−1 on unmodified and 3.07 mg ha−1 with 0.9‐m and 3.37 Mg ha−1 with 1.5‐m deep PM). This study showed that PM imposed on the Pullman soil in 1964 is still highly effective for increasing water infiltration. Although wheat yields were not significantly increased, grain sorghum [Sorghum bicolor (L.) Moench] and alfalfa (Medicago sativa L.) responded favorably to PM in previous studies. Considering the long‐term benefits, PM should be cost‐effective if the cost is prorated over the lifetime of the benefits and if crops that respond favorably to PM are grown.
Inadequacy of the Liebig Limiting‐Factor Paradigm for Explaining Varying Crop Yields
Authors: Sinclair Thomas R. , Park Wayne I.
Published: July 2010

Historically, the limiting‐factor paradigm has been used to describe how crop yields may be constrained by the individual input resources required by plants. The limiting‐factor paradigm proposes that plant growth is constrained only by a single resource whose availability is so low that it solely inhibits greater growth or growth rates. However, this paradigm ignores the great flexibility of plants to acclimate morphologically and physiologically to changing environmental conditions. In view of the inadequacy of the limiting‐factor paradigm, an analysis analogous to that used in economic studies to describe well‐managed businesses was developed. Investment of capital reserves (i.e., photosynthate) is allocated to obtain various input resources (i.e., water, minerals, etc.) in order to maximize output (i.e., crop growth). The important criterion in the allocation of reserves is that the capital reserves should be allocated to the resources with the greatest marginal returns. Since the marginal return for each resource is likely to change as the crop develops and the environment changes, resource allocation (i.e., plant development and physiology) is predicted to be dynamic and continually adjusting through the plant life cycle. An interesting outcome predicted for this acclimatable plant development is that under many conditions a number of resources will be simultaneously limiting crop growth. It is suggested that the types of data and analyses required to assess resource limitation on crop yield need to be reevaluated.
Forage Intake and Ingestive Behavior of Cattle Grazing Old World Bluestems
Authors: Forbes T. D. A. , Coleman S. W.
Published: July 2010

Many native and introduced warm‐season grasses are being seeded as a consequence of crop reduction programs; however, little is known about the intake and ingestive behavior of cattle (Bos taurus L.) grazing such grasses. The influence of differences in herbage mass, sward height, and morphological composition of old world bluestem (Bothriochloa spp.) pastures on herbage intake and ingestive behavior of steers were examined over the course of two grazing seasons at El Reno, OK. Soils were fine‐silty Pachic Haplustolls of the Dale series. Swards of ‘Caucasian’ [B. caucasica (Trin.) C.E. Hubb.] and ‘Plains’ [B. ischaemum (Hack.) Celarier & Harlan var. ischaemum (L.) Keng.] old world bluestem were maintained within the range of 0.5 to 5 Mg ha−1 by continuous variable stocking. Five grazing trials were conducted using a total of 20 swards over the 2 yr. In both years, pastures were grazed from mid‐May to late September by steers with an initial weight of ≈250 kg. Results showed that changes in sward height had little influence on organic matter intake or ingestive behavior, but changes in herbage mass, green mass, total green leaf proportion, and leaf proportion had more effect. Diet digestibility was most influenced by the proportion of green leaf in the sward. Organic matter intake increased with increasing green leaf mass to 1.07 Mg ha−1 and then decreased. Intake per bite and grazing time also increased as proportion of green leaf and herbage mass increased, respectively. These two measures of ingestive behavior were highly influential on intake. Management of old world bluestems should aim to maintain swards with a high proportion of green leaf.
Nonstructural Carbohydrate Utilization by Wheat Shaded during Grain Growth
Authors: Kiniry J. R.
Published: July 2010

Wheat (Triticum aestivum L.) is commonly grown in dryland conditions, where environmental stress during grain filling can increase the dependency on stored assimilate. The objective of this study was to quantify the loss of total nonstructural carbohydrates (TNC) from wheat leaves and stems and the increase in seed dry mass when severe shading stress occurred after anthesis. Beginning 10 to 11 d after anthesis, severe shading was imposed on ‘Mit’ wheat in the field at Temple, TX, in 1991 and 1992. During shading, plants with spikes had reductions in stem dry mass of 290 g kg‐1 in 1991 and 140 g kg‐1 in 1992. Leaf dry mass decreased 240 g kg‐1 in 1991 and increased 10 g kg‐1 in 1992. Fructan and sucrose comprised the largest proportion of the storage carbohydrate reduction in stems and leaves. Starch in stems and leaves was not remobilized during shading. Estimates of maintenance coefficient were 4.3 mg carbohydrate g−1 dry mass d‐1 in 1991 and 1.8 in 1992. Maintenance respiration consumed 68% of the TNC present at the start of shading in 1991 and 18% in 1992. There was 0.68 g of grain produced per gram of assimilate lost from leaves, stems, and the nongrain portions of spikes in 1991 and 0.78 in 1992. When estimated costs of maintenance respiration were removed, 0.82 and 0.93 g of grain was produced per gram of assimilate that disappeared. Stored carbohydrate represented an important buffer for yield production when stress occurred during grain filling.
Seedling Emergence Model for Velvetleaf
Authors: Forcella Frank
Published: July 2010

Consistent postemergence weed control requires information on the timing of weed emergence. Information is especially important for velvetleaf (Abutilon theophrasti Medikus), which interferes with many crops over a broad geographic range. The objective of this study was to develop a model that predicts the timing and proportional extent of velvetleaf seedling emergence. Environmental effects on seed germination and seedling emergence, used to construct the model, were determined in growth chambers or from published sources. Two variables drive the model: average daily soil temperature of the seed zone (5‐cm soil depth) and daily rainfall. The model requires initialization by four seed zone parameters: (i) soil water content at the start of the simulation period, (ii) soil water holding capacity, (iii) soil bulk density, and (iv) a water retention curve relating percent soil water to soil water potential. The model was validated using field data collected in Illinois in 1967 and 1969 and in Minnesota in 1990. Regressions of predicted and observed seedling emergence resulted in r2 values of 0.91, 0.97, and 0.98 for 1967, 1969, and 1990, respectively. Correspondence (regression coefficients) between predicted and observed seedling emergence was 0.83, 1.01, and 1.01 for 1967, 1969, and 1990, respectively. Both sets of statistics indicate the model predicts velvetleaf seedling emergence reliably.
Cotton Yield and Fiber Quality Response to Green Manures and Nitrogen
Authors: Bauer P. J. , Camberato J. J. , Roach S. H.
Published: July 2010

The quantity and availability of N from green manures will considerably affect the N management of a succeeding cotton (Gossypium hirsutum L.) crop. This study was conducted to determine the N supplying capacity of crimson clover (Trifolium incarnatum L.), Austrian winter pea [Pisum sativum subsp. arvense (L.) Poir.], and rye (Secale cereale L.) to cotton and their influence on cotton yield and fiber properties. Green manure treatments (and a fallow check) with fertilizer N levels of 0, 56, 112, and 168 kg ha−1 were compared for 3 yr on a Norfolk loamy sand (fine‐loamy, siliceous, thermic Typic Kandiudult). Soil moisture at planting was similar among the four green manuretr eatments. At the 0 N level, the legumes generally had higher soil NO3‐N than rye or fallow. Cotton grown following clover and pea with 0 kg ha−1 added N had petiole NO3‐N levels similar to those of rye and fallow with 56 kg N ha−1. Fertilizer N had no influence on cotton yield in the pea winter cover treatment. A quadratic regression equation best described the lint yield response following clover. For both rye and fallow treatments, yield plateaued at 56 kg N ha−1. Green manures had little influence on fiber properties. The results indicate that legumes supply adequate but not excessive N for modern cotton production and that incorporation of rye into the production system does not affect N fertilization requirements.
High pH Treatments and the Alleviation of Soil Hydrophobicity on Golf Greens
Authors: Karnok Keith A. , Rowland Everett J. , Tan Kim H.
Published: July 2010

Hydrophobic soil associated with localized dry spots (LDS) on creeping bentgrass (Agrostis palustris Huds.) putting greens has been shown to be caused by a humic and/or fulvic acid coating of the sand particles. Under laboratory conditions, humic acid begins to solubilize at pH 7.0 and is completely soluble at pH 9.5 or greater. The purpose of this study was to determine the potential of high pH treatments for alleviating soil hydrophobicity of a creeping bentgrass golf green. Three separate studies were conducted on the University of Georgia Experimental Golf Green, Athens, GA, during the spring and summer of 1990 and spring of 1991. The creeping bentgrass green, constructed with an 85% sand and 15% peat root zone mixture, had a well documented history of LDS caused by hydrophobic soil. Soil hydrophobicity was determined by the molarity of an aqueous ethanol droplet (MED) technique. Results showed that an application of 0.1 M NaOH sufficient to saturate the upper 50 mm of soil, followed by a water flush of one pore volume, significantly reduced soil hydrophobicity if repeated three or more times. In one study, soil hydrophobicity was completely eliminated after nine consecutive daily treatments of 0.1 M NaOH, each of which was followed by a water flush. A concurrent decrease in soil humic matter content suggested that its dissolution and removal was responsible for the increased wettability of the soil profile. Bentgrass treated with NaOH showed varying degrees of phytotoxicity. The severity of injury depended on the number of consecutive applications and air temperature. Little or no discoloration was noted when air temperatures was ≤24 °C; however, severe wilt and desiccation occurred when treatments were applied when air temperature was ≥ °C. High pH treatments may be an effective means to reduce soil hydrophobicity on sand‐based golf putting greens.
Alfalfa Growth Following Release from Drought Stress
Authors: Hall Marvin H.
Published: July 2010

Compensatory growth (increased growth relative to normal) of alfalfa (Medicago sativa L.) when released from periods of drought stress has been observed or suggested. The objective of this research was to determine whether such compensatory growth does occur. Alfalfa was subjected to drought stress (plant water potential < ‐ 1.5 MPa) for 2 and 4 wk in a greenhouse study and 2, 4, and 6 wk in a field (Palouse silt loam soil, fine‐silty, mixed, mesic Pachic Ultic Haploxerolls) study near Moscow ID. Following harvest and removal of the drought stress, plant growth measurements were made after 30 d of growth in the greenhouse and biweekly during 5 wk of growth in the field. At the conclusion of the growth periods in both greenhouse and field studies, average stem length and dry matter yield of previously drought‐stressed plants were 88 and 91%, respectively, compared with previously unstressed plants. Stem growth rates of field grown plants were less for the previously stressed plants only during the first 2 wk after release of stress. Stress treatments did not affect stems per plant (greenhouse) or stems per square meter (field). Leaf area per stem, however, for the previously drought‐stressed plants was 122 and 108% compared with previously unstressed plants in the greenhouse and field, respectively. Leaf area was greater in the growth period following drought stress, but stem length and dry matter yield were reduced. Previous observations of apparent compensatory alfalfa growth after a drought may be attributed to increased leaf area.
Productivity of Four Annual Legumes as Green Manure in Dryland Cropping Systems
Authors: Biederbeck V. O. , Bouman O. T. , Looman J. , Slinkard A. E. , Bailey L. D. , Rice W. A. , Janzen H. H.
Published: July 2010

Integration of green manuring as fallow replacement in dryland cereal production requires selection of well‐adapted legumes. The objectives of this study were to (i) analyze vegetative growth of annual legumes and (ii) assess the relative merits of each legume as shortterm green manure crop. Inoculated black lentil (Lens culinaris Medikus), Tangier flatpea (Lathyrus tingitanus L.), chickling vetch (Lathyrus sativus L.), and feedpea (Pisum sativum L.) were tested on an Orthic Brown Chernozem soil (Aridic Haploborolls) at Swift Current, SK, Canada, from 1984 to 1990. Legume species and years differed significantly in dry matter (DM) production of shoots, roots, and nodules; DM partitioning; growth habit; relative growth rate; and weediness. Total legume DM ranged from 601 to 3961 kg ha−1, with 6‐ yr means of 1669 kg ha−1 for black lentil, 1486 for Tangier flatpea, 2230 for chickling vetch, and 3008 for feedpea. Nodulation was most abundant with chickling vetch and least with Tangier flatpea; nodule DM ranged from 2 to 329 kg ha−1. Coefficients of determination between nodule and legume DM were r2 = 0.93*** for chickling vetch and r2 = 0.78*** for feedpea, indicating their ability to benefit from symbiosis with Rhizobium. Nodulation was greatly influenced by soil mineral N and soil water. Average DM allocation to roots as a percentage of total legume biomass averaged =7% for chickling vetch and feedpea and 12% for black lentil and Tangier flatpea. Feedpea canopy height was double to triple that of black lentil. The degree of decumbency (stem length/canopy height) was 1.09 for black lentil, 1.19 for chickling vetch, 1.21 for feedpea, and 1.29 for Tangier flatpea. Growth rate analysis identified chickling vetch as an early‐developing legume. Feedpea and chickling vetch were definitely more suited to green manuring in semiarid climates than black lentil and Tangier flatpea. Feedpea has good growth habits and greatest DM production. Chickling
Long‐Term Effect of Five Tillage Systems on Corn Response and Soil Structure
Authors: Vyn T. J. , Raimbult B. A.
Published: July 2010

Tillage systems need to be compared over an extended period of time to determine their transitional and long‐term impacts on crop growth and soil properties. A 15‐yr experiment established in 1976 compared reduced tillage systems with conventional fall moldboard plowing for production of continuous corn (Zea mays L.) on a Maryhill silt loam soil (Typic Hapludalf). Corn plant growth and yield and soil properties were compared for five tillage systems: fall plow (fall mold‐board plow + spring secondary tillage), fall chisel plow (fall chisel plow + spring secondary), spring plow, spring plow/secondary (spring plow + secondary), and no‐till. No‐till consistently resulted in slower plant growth than most or all of the other tillage systems. The fall plow and spring plow/secondary treatments resulted in grain yields averaging 5% more than fall chisel plow, 9% more than spring plow, and 16% more than no‐till yields. From 1976 to 1983, no‐till yields tended to increase relative to fall plow; from 1988 to 1990, however, no‐till yields were much less than fall plow. No‐till resulted in the lowest proportion of aggregates <5 mm in diameter, highest bulk density, and greatest penetrometer resistance. Penetrometer resistance of the spring plow plots increased at a slower rate with depth than the fall chisel plow system. Among soil properties measured, the proportion of aggregates <5 mm in diameter was most often significantly correlated with yield.