bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Ethanol‐Extracted and Unextracted Crownvetch Forage Fed to Weanling Meadow Voles1
Authors: Barnes R. F. , Fissel G. W. , Shenk J. S.
Published: July 2010

The potential effects of adverse constituents in crownvetch (Coronilla varia L.) forage on animal response were assessed using the weanling meadow vole (Microtus pennsylvanicus) as the test animal. ‘Chemung, ’ ‘Emerald,’ and ‘Penngift’ crownvetch were harvested at the early‐bud and late seed‐set stages during two growing seasons. Crownvetch forage extracted with ethanol and unextracted forage were incorporated into diets supplemented with adequate levels of protein, carbohydrate, vitamins, and minerals and fed to weanling meadow voles. Of 72 voles fed unextracted crownvetch diets, 46 died within 6 days, and most of the remaining voles lost weight. Deaths and weight losses were greatest on the mature crownvetch diets, with more deaths occurring from the 1969‐harvested forage than from that of 1971. The deleterious substance was apparently removed by ethanol extraction of the forage as shown by the death of voles fed control diets to which the ethanol extract was added. Weight gains and dry matter consumption of voles fed diets prepared with ethanol‐extracted forage were equivalent to those of the voles fed control diets containing purified cellulose.
Effects of Different Initial Cutting Treatments on the Production and Quality of Climax Timothy and Reed Canarygrass1
Authors: Mislevy P. , Washko J. B. , Harrington J. D.
Published: July 2010

Total yield, aftermath, and total digestible nutrients (TDN) production of perennial grasses when harvested at various physiological stages of development were investigated. The initial harvest of Climax timothy (Phleum pratense L.) and reed canarygrass (Phalaris arundinacea L.) was removed at eight physiological stages of development corresponding to plant heights of 20, 30, 41, 46, 51, 61, 71, and 81 cm.

Removal of the initial harvest of timothy when the apical meristem was at a transition stage (plants 30 cm tall) resulted in highest total seasonal yield, aftermath, and TDN/ha. Reed canarygrass, however, produced lowest total seasonal yield and TDN when the initial harvest was removed early, at the first two stages of development. This species was less influenced by initial plant cutting height. Total seasonal aftermath of reed canarygrass varied by only 1,973 kg/ha regardless of when the initial crop was removed. These data indicate a differential response of timothy and reed canarygrass to specific cutting management practices.
Effect of Irrigation and Water‐Table Depth on Crop Yields1
Authors: Follett R. F. , Doering E. J. , Reichman G. A. , Benz L. C.
Published: July 2010

The objective in this field study was to determine the most desirable combination of amount of irrigation and degree of drainage for production of corn (Zea mays L.), sugarbeets (Beta vulgaris L.), and alfalfa (Medicago sativa L.) grown on sandy soil over a declining water table. Irrigation was applied at weekly intervals at rates of either 0, 0.5, 1.0, or 1.5 times the water requirement of the crops as predicted by the modified Jensen‐Haise equation. Irrigation amounts were applied in combination with shallow, medium, and deep drainage. In 1971 and 1972, early season depth to water table was 92 and 69 cm for the shallow drainage treatment, 166 and 145 cm for the medium, and 186 and 193 cm for the deep. Water‐table declines were 94 and 96 cm during the 1971 and 1972 growing seasons, respectively, under all treatments. Corn was harvested at maturity, sugarbeets in mid‐October, and alfalfa (three cuttings) at 1/10 bloom.

Maximum yields of all crops occurred over the shallow water table; no yield response to irrigation was observed over the shallow water table. Both corn and sugarbeets grown over the medium and deep water tables responded to irrigation as did alfalfa grown over the deep water table. Regardless of irrigation amount, crop yields from deeper water tables never exceeded those from the shallowest water table. Results indicate a need for research on methods for developing practical systems of controlled shallow drainage on a field scale.
Dissipation of Acetanilide Herbicides from Soils1
Authors: Beestman G. B. , Deming J. M.
Published: July 2010

Three commercial α‐chloroacetanilide herbicides, alachlor, butachlor, and propachlor, were surface‐applied in aqueous solution on two soil types in the field to determine their soil half‐lives. Laboratory studies were conducted to assess the major routes of dissipation from soils. While much is known about the activity and mode of action of these herbicides, little quantitative information is available concerning the modes of dissipation from soils. This research was conducted to determine dissipation rates under field conditions and to quantitate the contributions of microbial decomposition, chemical breakdown, volatilization, and leaching. Dissipation followed first order kinetics with short field half‐lives ranging from 2 to 14 days depending upon the herbicide and soil type. Leaching did not contribute to dissipation since no residues were found below the upper 4 cm layer. Dissipation from sterilized soil was 50 times slower than dissipation from viable soil, indicating that microbial decomposition played a major role in herbicide degradation. Rapid herbicide volatilization occurred from continuously moist soil exposed to a constant 21C, 3.2 kph air stream impinging upon the treated soil surface but little loss occurred from dry soils. Atrazine was also rapidly lost from moist soil under these conditions, with volatilization rates falling in the order propachlor > atrazine > alachlor > butachlor. The major avenue of dissipation of these acetanilide herbicides from soil is by microbial decomposition. Significant volatilization losses occur only under windy conditions during the interval that exposed soil surfaces remain moist.
Determining Nitrogen Fertilizer Needs for Sugarbeets from Residual Soil Nitrate and Mineralizable Nitrogen1
Authors: Carter J. N. , Jensen M. E. , Bosma S. M.
Published: July 2010

Soil nitrate and mineralizable nitrogen are used to predict the root yield potential and N fertilizer needs of sugarbeets. Predicting the required N fertilizer for optimum refined sucrose production based on soil test procedures is needed because inadequate N limits root yield and high levels of N may reduce both extractable sucrose and sucrose yield.

Sugarbeets (Beta vulgaris L.) were grown at 14 residual and fertilizer N rates to determine the root yield, sucrose percentage, sucrose yield, and N uptake in relation to the residual, mineralizable, and fertilizer N. A soil test to measure both the mineralizable and NO3‐N level of a soil was found to serve as a valuable guide in recommending N fertilizer for sugarbeets. The amount of N supplied from mineralizable sources in a uniformly cropped and fertilized field is expected to remain reasonably constant if adequate but not excess N fertilizer is supplied each year to the crop grown. Therefore, repeating the test for mineralizable N each year may not be necessary. Determining the amount of NO3‐N in the root zone, which is now feasible with rapid and accurate methods of soil analysis, combined with the predetermined mineralizable N, would increase the accuracy of N fertilizer recommendations.
Comparison of Fall‐Applied N Under Formed Beds with Conventional Spring N Application for Corn Production1
Authors: Boswell Fred C. , Futral J .G. , Anderson O. E.
Published: July 2010

Few studies have been reported on the comparison of fall‐ and spring‐applied N for crop production in the Southeast, especially when nitrification inhibitors have been used to ameliorate N losses due to leaching. Because of the agronomic advantages inherent to such a practice, research was needed to assess its feasibility. A study was begun to 1) compare the efficiency in corn (Zea mays L.) production of fall‐applied N under formed beds, with and without a nitrification inhibitor, with spring‐applied N conventionally, and 2) determine the influence of these practices on certain plant constituents. Results indicate that moisture conditions for early planting and plant emergence under formed beds were excellent. In only the 1st year of the 3 years, did fall‐applied N with a nitrification inhibitor result in greater corn grain yield (P = .01) than did the same N rate (156 kg/ha) without the inhibitor. Fall‐applied N (156 kg/ha rate), with or without the inhibitor, was as efficient in corn production as a split application of half in the fall and half as sidedressing, or a preplant application plus sidedressing. For 2 of 3 years, tissue sampled at the silking stage had a higher N content when the N was applied split than did tissue where all the N was fall‐applied.
Quality of First Growth Crownvetch Forage and Its Potential for Improvement1
Authors: Shenk J. S. , Risius M. L.
Published: July 2010

Interest has been developing in the utilization of crownvetch (Coronilla varia L.) forage as livestock feed. In 1969 and 1970, changes in the quality of first growth forage from three crownvetch cultivars were characterized. Forage from ‘Penngift,’ ‘Chemung,’ and ‘Emerald’ was harvested during the spring at weekly intervals from field plots. First growth forage increased in dry matter percentages and cell wall constituents and deceased in in vitro dry matter disappearance (IVDMD) and protein percentages from late May to late June. These changes in forage quality were similar for the three cultivars but significant year effects for most quality traits were found.

The potential for improving the quality of crownvetch forage by breeding and selection was explored by determining the variation for quality and morphological traits among individual plants of Penngift and Chemung. In each cultivar, forage was harvested at first flower from 24 plants. Significant variation for morphological traits, IVDMD, and protein was found among plants within each cultivar. Differences among plants for cell wall concentration and composition were significant for Penngift only. Flowering date, stem length, and regrowth height were not significantly correlated with IVDMD. Although dry matter, protein, and estimated digestibility were significantly correlated with IVDMD, none of the relationships were strong enough to use for predictive purposes. The in vitro system would seem to be the most useful procedure for screening individual plants for higher forage quality.
Rate of Nutrient Uptake per Unit of Corn Root Under Field Conditions1
Authors: Mengel D. B. , Barber S. A.
Published: July 2010

Information on changes in the rate of nutrient uptake per unit of plant root length (nutrient flux) during the growth of the plant is important for evaluating the capacity of the soil to supply sufficient nutrient to the root surface. Since little information was available, nutrient flux into the root was determined in the field by sampling corn (Zea mays L.) plants at 9 and 14 dates in 1970 and 1971, respectively. Root length, root fresh weight, shoot dry weight, and content of 10 nutrients in the shoot were determined on replicated samples at each harvest. Nutrient uptake rates per plant per day were calculated and divided by mean root lengths to get nutrient flux into the root as related to plant age.

Nutrient flux was greatest at the first sampling, decreased rapidly with increased plant age until plants were 70 days old, and then remained relatively constant. Phosphorus flux into the root was 11.3 μmoles per meter of root per day at 20 days and 0.08 μmoles m−1d−1 at 80 days. Mean flux into the root was similar in both years despite large grain yield differences between years. As the flux may be biased downward with older plants because of lower uptake rates by more mature tissue, efforts were made to overcome the bias by assuming that only roots less than 5 days old actively absorbed nutrients. Flux calculations on this basis still decreased as the plant developed, but the differences were smaller.
Interactive Effects of Salinity and Fertility on Yields of Grains and Vegetables1
Authors: Bernstein Leon , Francois L. E. , Clark R. A.
Published: July 2010

The salt tolerance of crops has usually been studied under optimal fertility conditions. The objectives of the present studies were to compare crop response to salinity when nutrients were limiting, adequate, or in excess to guide proper fertilization of saline soils and to determine whether additional fertilizer could restore yield losses caused by salinity.

Corn (Zea mays L.), wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and six vegetable crops were grown to maturity in large, outdoor sand cultures to study the interactive effects of salinity and nutrition. Increasing levels of phosphate (0.1 to 2.0 mM) aggravated salt injury in corn and decreased salt tolerance. Decreasing solution K from 2 to 0.4 meq/liter did not affect leaf K or yield of corn. Deficient levels of P or N did not consistently decrease salt tolerance of any of the crops studied, although the wheat and barley varieties showed erratic decreases in salt tolerance when N or P was deficient. When N or P was severely growth‐limiting, salinity affected growth of some crops [broccoli (Brassica oleracea var. capitata), cabbage (B. oleracea var. botrytis)] less. Conversely, when salinity severely limited growth, nutritional responses of some crops decreased. Salinity did not aggravate N or P deficiency as judged by leaf N and leaf P contents. Effects of salinity and N or P deficiency on other mineral constituents were highly crop specific.
Physiological Responses to Wind‐ and Sandblast‐Damaged Winter Wheat Plants1
Authors: Armbrust D. V. , Paulsen Gary M. , Ellis R.
Published: July 2010

Yield depression due to physical damage by wind and windblown soil (sandblast damage) is well known. The objective of this research was to determine if this yield depression was due to physiological changes within the plant or to the loss of viable plant tissue.

Physiological responses of winter wheat (Triticum aestivum L. em. Thell) to injury by a 20‐minute exposure to wind (13.4 m/sec), wind plus sand (5, 10, and 15 kg), and partial defoliation (removal of the distal 1/4 and 1/2 of each leaf) were evaluated. Net photosynthesis, dark respiration, ribulose‐l,5‐diphosphate (RUDP) carboxylase activity, total chlorophyll, dry weight, leaf area, and total nonstructural carbohydrates (TNC) were determined 1, 3, and 7 days after treatment.

Dry‐weight production and accumulation decreased with increased plant injury. Reduced growth of sandblasted wheat seedlings is caused by loss of viable leaf tissue and physiological changes, which are mainly reduced photosynthesis and increased respiration. It is not clear from this study whether these changes result from partial defoliation, short‐term high‐intensity moisture stress, or a combination of both.
Variations in Percent Protein of Individual Seeds from Five Peanut Plants
Authors: Young C. T. , Tai Y. P.
Published: July 2010

The purpose of this study was to examine the variation in percent protein of individual seeds from five peanut (Arachis hypogaea L.) plants of ‘NC2,’ (a Virginia‐type commercial peanut variety) using macro‐Kjeldahl analysis. The differences in percent protein between mature and immature seeds and between basal and apical seeds were also examined. Protein levels varied significantly among individual seeds from each of the five peanut plants. No relationship was obtained between the percent protein of the individual seeds and either the fruit placement or the branching pattern. Percent protein was higher in immature than in mature seeds. Apical seeds also had a higher pereent protein than the basal ones. Seeds with higher dry weight had significantly lower percent protein. Because of these observed variations in percent protein, the selection of individual seeds for genetic studies of protein must be made with great care.
Iron Supply in Soybean Seedlings1
Authors: Ambler John E. , Brown John C.
Published: July 2010

Soybean [Glycine max (L.) Merrill] seedlings are dependent on the iron supply in the seed for early growth. Any factor that limits this supply of Fe could cause poor growth and would require management practices to eliminate these factors to insure good seedlings. Phosphate and Fe‐stress response were the variables used to test the availability of seed iron in the seedlings. Phosphate competes with the plant for Fe, and Fe‐stress response is an adaptive mechanism that accentuates the transport of iron. ‘PI‐54619‐5‐1’ (PI) soybean has an inefficient Fe‐stress response mechanism and ‘Hawkeye’ (HA) has a very efficient Fe‐stress response mechanism. Our objective was to determine how these factors affected the utlization of Fe from the soybean seeds as compared to Fe supplied externally.

Soybean seeds of these two lines were produced by plants treated from anthesis to seed maturity with 59Fe supplied as ferric ethylenediaminedi(o‐hydroxyphenylacetate). Seedling plants, from labeled 59Fe seeds, were subsequently studied to determine the effect of Fe‐stress response and to determine the effect of varied nutrient P on the translocation and utilization of 59Fe from the cotyledons of Fe‐inefficient and Fe‐efficient soybeans. Cotyledonary Fe, of both lines in the seedling stage, appeared available for translocation and utilization and was not affected by Fe stress or varied nutrient P. It was concluded that Fe should not be a limiting factor in establishing a good stand of soybeans in the field because of the readily available source of Fe from the seed.
Effect of Transpiration Rate on Salt Accumulation Around Corn Roots in a Saline Soil1
Authors: Sinha B. K. , Singh N. T.
Published: July 2010

Laboratory studies were conducted to determine the extent of ion accumulation around corn (Zea mays L.) roots of plants exposed to different transpiration conditions. Ion accumulation in the apparent free space of roots, the soil adhering to the roots, and the bulk soil was studied using a soil mixed with sodium chloride so that the electrical conductivity of saturation extract was 3.96 mmho/cm. Maximum ion accumulation occurred in the apparent free space of the roots, followed by the closely adhering soil. Under high transpiration, sodium concentration increased from 37.6 mg/100 g in the bulk soil to 90.3 mg/100 g in the soil close to the roots. After the same treatment, a threefold increase in the chloride content of the closely adhering soil was observed. A significant correlation existed between the rate of water loss per unit root length and the Na and Xl concentration of the closely adhering soil. Results indicate that under high transpiration, the salt concentration close to the roots may be much higher than that obtained from an analysis of the bulk soil.
Isolation of β‐Nitropropionic Acid from Crownvetch1
Authors: Gustine D. L. , Shenk J. S. , Moyer B. G. , Barnes R. F.
Published: July 2010

Compounds that are toxic when fed to meadow voles (Microtus pennsylvanicus) have been isolafed from freshcut, oven‐dried crownvetch (Coronilla varia L.) forage. This activity was detected by weanling meadow vole bioassays in which weight change, diet intake, and death were recorded during 6‐day feeding trials. The compounds were extracted from dried, ground forage with 95% ethanol. Nonpolar compounds were precipitated by addition of water, and the active compounds remained in aqueous solution. The active compounds remained in the aqueous phase after partitioning with chloroformethanol (8.5:1.5), but were extracted into the organic phase during partitioning with ethyl formate. They were further purified by passage through a polyamide column, and then fractionated by silicic acid column chromatography. From the final fractions, β‐nitropropionic acid (BNPA) was isolated. This is the first report of the presence of BNPA in crownvetch. Weanling voles fed crownvetch and BNPA ~in diets at 20 and 0.15%, respectively, showed identical responses, thus indicating that BNPA is a toxic factor in crownvetch.
Anhydrous Ammonia and Propionic Acid as Hay Preservatives1
Authors: Knapp W. R. , Holt D. A. , Lechtenberg V. L.
Published: July 2010

Anhydrous ammonia was applied at 1.0% and propionic acid was applied at 0.02, 0.2, 0.5, and 1.0% of the weight of hay to alfalfa hay baled at about 35% moisture to test their individual effectiveness as perservatives. After 2 months of storage, ammonia‐treated hay was green and no mold was visible. The 1.0% propionic acid‐treated hay was free of visible mold but had lost green color. Hay treated with anhydrous ammonia and highest levels of propionic acid reached lower temperatures and lost only about half as much digestible dry matter as untreated hay or hay treated with lower levels of propionic acid. Anhydrous ammonia treatment at baling time increased by 30% total N content of hay stored 2 months.
Effect of pH on the Absorption of Boron by Excised Barley Roots
Authors: Oertli J. J. , Grgurevic E.
Published: July 2010

In order to obtain information on the mechanism of B uptake and on the relative importance of the two forms H3BO3 and H2BO3− for net B absorption, the uptake of B by excised barley (Hordeum vulgure var. Briggs) was investigated using solutions having pH values from 6 to 10 and B concentrations from 1 to 10 ppm. The B uptake and final B contents after 1 hour absorption periods increased nearly linearly with increasing B supply. The relative B uptake (uptake at pH 6 = 100%) at all supply levels decreased with increasing pH similar to the decrease of the fraction of undissociated H3BO3. At pH 6 final B contents in roots and treatment solutions were similar. From this it is concluded that B in root tissues and external solution tends to approach a diffusion equilibrium which is governed by the undissociated acid. Boron thus differs fundamentally from most other nutrients which are present in an ionized form and are transported actively.
Relationship between Corn Yield and Plant Potassium1
Authors: Walker W. M. , Peck T. R.
Published: July 2010

Chemical composition of the sixth corn (Zea mays L.) leaf at early tassel has been widely used in diagnosing the nutritional status of the plant at this particular stage of development. However at this relatively late stage of development, application of supplement plant nutrients when needed, is difficult. Thus, critical nutrient values for corn and other crop plants should be determined so that a knowledgeable interpretation of their chemical composition can be made at an early stage of development which would permit supplementary nutrient applications. Under some conditions and for some nutrients, plant uptake of one or more nutrients may be more important than concentration; “critical” uptake values should also be determined.

The objective of this experiment was to determine the relationship between corn yield and the K composition of corn plants at three stages of growth where K composition includes both its concentration and uptake. Corn yields and plant samples were obtained from an experiment at the U. of Ill. Agron. Res. Cen. at Browns‐town in South Central Illinois. Experimental plots were lanted in 76‐cm rows to a population of 49,000 plants/ha of an Illinois‐adapted cultivar. The soil type was a Cisne silt loam (mollic albaqualf).

Corn yields were regressed on the K concentration (%K) of whole plants that averaged 25 and 76 cm in height, respectively, and upon the average K concentration of the fifth, sixth, and seventh leaves at early tassel. Co‐efficients of multiple determination (R2) for the quadratic equations were 0.71, 0.74, and 0.78, respectively. The critical K percentage (the percent K resulting in maximum predicted yield) for whole corn plants 25 cm in height was determined to be 3.98; for plants 76 cm in height, it was 3.90. The critical K percentage for the average of the fifth, sixth, and seventh leaves was 1.80%. When corn yield was regressed upon K uptake of plants 25 and 76 cm in height, R2 values were 0.63 and 0.60, respectively. The K content for the maximum predicted yield when corn plants averaged 25 and 76 cm was 0.094 and 0.674 g/plant, respectively. Since the critical K percentage varied with the stage of plant development, critical percentages established for one stage of growth should not be used for diagnosing plant nutrition problems at other stages of the corn plant's development.
Cotton and Corn Root Development in Two Field Soils of Different Strength Characteristics1
Authors: Grimes D. W. , Miller R. J. , Wiley P. L.
Published: July 2010

Many agriculturally important soils in the San Joaquin Valley, being compact and of high strength, may pose special problems in water management. The higher than normal frequency of irrigation often required to meet evapotranspiration demand suggests that plant root development has been limited. This study was conducted to determine the influence of high penetrometer soil strength, found naturally occurring in the field, on the root development of cotton (Gossypium hirsutum L.) and corn (Zea mays L.). Additional objectives were to determine if root distribution could be influenced by planting geometry and density, and to relate soil water depletion to observed root density (cm of root/cm3 of soil).

Cotton and corn plots, having a variable row width and plant density, were established on each of two field soils that differed considerably in strength as measured with a recording soil penetrometer. Root densities of the two crops were related to the independent variables penetrometer strength (measured in situ), and soil depth in a regression model that accounted for 75% of the observed variation. A high‐density plant population of cotton caused higher root densities in the 30 to 122 cm‐depth zone in a low‐strength soil than that with normal plantings. A linear relation between water depletion and root density indicated average water uptake values for fully transpiring corn and cotton to be respectively 2.33 × 10−a and 7.86 × 10−3 cm8/cm/day.

Field measured soil strength was effective for diagnosing or predicting mechanical root growth restrictions of well drained soils.
Effect of Dew on Leaf Water Potentials and Crop Resistances in a Paspalum Pasture1
Authors: Kerr J. P. , Beardsell M. F.
Published: July 2010

Opportunities for comparing the water status of crops when the presence or absence of dew is the main environmental variable are rare. This paper reports the results of such a comparison made on successive days on a Paspalum dilatatum (Poir) pasture. Leaf water potentials (Ψ1) were measured with a pressure chamber, and the energy balance method was used to determine evapotranspiration. Crop resistances (rc) were calculated from the micrometeorological data.

The presence of dew halved the early morning crop resistances (1.7 compared to 0.9 sec cm−1). The paspalum pasture did not appear to exercise stomatal control over evapotranspiration until most of the dew had evaporated. At ca 1000 hours rc was 1.6 sec cm−1 on both days.

Leaf water potentials measured before sunrise were −1.3 bars and at noon were ca −13.0 bars on both days, but the pattern of change in Ψ1 between these times varied. In the absence of dew Ψ1 decreased rapidly to reach −12.0 bars at 0900 hours; whereas with dew present, relatively high Ψ1 were maintained until most of the dew had evaporated.

Dew, which is a significant feature of many agricultural regions, may thus have an important effect on the water balance of pastures and crops and thereby enhance production.
Dry Matter Accumulation in Maize in Response to Defoliation1
Authors: Egharevba P. N. , Horrocks R. D. , Zuber M. S.
Published: July 2010

Prior investigations have reported the effect of leaf removal at various stages of development on yield of corn (Zea mays L.), but none have studied the pattern of grain dry matter accumulation. Therefore, this study was conducted to evaluate the effect of leaf loss on dry matter accumulation patterns of corn grain and grain yields. Defoliation was begun 10 days after 50% silking and continued at 10‐day intervals for the next 40 days. Leaf removal treatments consisted of removing 1) no leaves (control), 2) all leaves below the ear, 3) all leaves above the ear, and 4) all leaves. Dry matter accumulation was monitored by sampling ears at 5‐day intervals from 50% silking to black layer formation.

Regardless of severity, defoliation within 30 days after silking significantly reduced total accumulated dry matter. Complete defoliation was more detrimental (6.4 to 82% yield loss) than partial defoliation (1.5 to 32.7% yield loss). These losses varied with time (after 50% silking) of treatment application. The effect of removing all leaves above the ear was not significantly different from that obtained by removing all leaves below the ear.

Yield component affected most by leaf loss, for the overall treatment period, was kernel weight (12.7 to 53% decrease). However, number of kernels was greatly reduced (62.3%) when all leaves were removed 10 days after silking. Complete leaf removal thereafter and partial leaf removal affected number of kernels considerably less (approximate decline, 20%).

This study showed that severe leaf loss at the onset of silking and until at least 10 days after 50% silking decreased grain yields because of fewer kernels. However, yield decreases associated with less severe leaf loss or loss 20 days or more after 50% silking were largely related to a decline in kernel weight. In addition to providing a better understanding of patterns of dry matter accumulation, these data may be useful to individuals required to estimate grain yield after a significant loss, to natural causes, in plant leaf area.
Corn Growth as Affected By Ammonium vs. Nitrate Absorbed From Soil1
Authors: Dibb D. W. , Welch L. F.
Published: July 2010

The effect of NH4 on corn (Zea mays L.) growth in a soil medium is of interest because of the possibility of significantly decreasing leaching and denitrification losses of applied N by preserving N in the NH4 form. The objective of this investigation was to determine growth and nutrient content of corn plants when the principal form of N was either NH4 or NO3.

Corn, grown in the greenhouse in a soil medium, was allowed to absorb N as either NH4 or NO3. A chemical nitrification inhibitor and different sources of added N were used to manipulate the form of N available for absorption. The maximum amount of N absorbed as NO3 was estimated as the difference between the NO3 content of fallow and cropped pots at harvest. Plants grown with NH4 and a nitrification inhibitor were estimated to have absorbed at least 95% of their N as NH4. Other plants absorbed N almost solely as NO3. The effect of NH4 versus NO3 absorption on stover yield, percent N, Ca, Mg, K, and P in the plant was determined.

Yield of corn plants was not negatively affected by form of N absorbed when the meq ratio of applied N:K was 2:1. Visual tissue damage and decreased yield were symptomatic of NH4 nutrition where the meq applied N:K ratio was 3.3, 4.0, 4.4, 6.6, and 8.0. Nutrient content of the plants reflected strong cation:cation and cation:anion interactions among N form absorbed and Ca, Mg, K, and P. Soil pH appeared to be affected less by form of N absorbed by the corn plants than by nitrification of applied NH4.
Equipment for Seeding Experimental Plots of Small Grains, Grasses, and Legumes1
Authors: Barker R. E. , Bond J. J. , Zachmeier L. G.
Published: July 2010

Many specialized experimental plot planters have been developed but they are usually expensive and have limited use. This note describes seeding equipment for experimental plots developed by modifying conventional farm implements. The equipment provides the benefits of uniform soil compaction, single cone seeder with distribution to multiple rows, and enclosed cab for seeding during inclement weather. The equipment is adaptable for seeding isolation seed production blocks, large plots for agronomic studies, or variety trials of small grains, grasses, and legumes.
Soil Temperature, Air Temperature, and Defoliation Effects on Growth and Nonstructural Carbohydrates of Kentucky Bluegrass1
Authors: Youngner V. B. , Nudge F. J.
Published: July 2010

Kentucky bluegrass (Poa pratensis L., is used for turf in many areas where soil and air temperatures are high for long periods. Using controlled temperature water baths and growth chambers, Kentucky bluegrass ‘Merion’ plants were grown at various soil and air temperatures and at three clipping heights to determine the interaction effects of temperature and defoliation on growth. Defoliation reduced dry weight of tops, number of innovations, root length and percent of nonstructural carbohydrates at all soil and air temperatures. Although a soil temperature of 18 C produced the most root and top growth in unclipped plants, this superiority was completely negated by defoliation.

A soil temperature of 27 C resulted in reduced root growth compared to that at 18 C. Defoliation intensified the unfavorable effect of the high soil temperature.

Nonstructural carbohydrate levels were lowest at the soil temperature (18 C), that produced the highest vegetative growth in unclipped plants. Differences in nonstructural carbohydrates among the soil temperature treatments were greatly reduced by defoliation.

In the growth chambers where soil and air temperatures were in equilibrium results were in general consistant with those where soil temperatures were regulated separately by means of the water baths. Highest number of innovations was obtained at 10 C regardless of defoliation treatment. Highest dry matter production of tops was obtained at 21 C on unclipped plants while all plants became dormant at 32 C and made no measurable growth.
Tall Fescue Turf as Affected by Mowing Height
Authors: Burns Robert E.
Published: July 2010

Tall fescue (Festuca arundinacea Schreb.) is a common turf and pasture grass in much of the United States. In an effort to determine the optimum cutting height for both uses, plots in a good stand of established tall fescue were mowed at 1.3, 2.5, 4, and 5 cm, when they reached a height 50% greater than the mowed height. The influence of cutting height on seasonal and total yield, appearance, density, and ground cover was determined. One‐half at each plot was overseeded with fescue immediately prior to the test and also in the fall of the first year. In the first year, total yield was higher when mowed at the two lower cutting heights. There was no difference in yields the second year and overseeding had little effect on yield. Both cover and plant density were usually greater at the two intermediate cutting heights and in the overseeded plots when compared with non‐overseeded plots. At the end of 4 years there was no difference in turf cover due to mowing height. This research indicates that with adequate fertilizer tall fescue can do well when maintained at low heights.
Precision Soil Sampler1
Authors: Walker Milton E. , Stansell J. R. , Shannon J. E.
Published: July 2010

A precision soil sampler has been developed that allows a soil core 15.2 cm long to be taken which can be divided into subsamples 2.54 cm or smaller. Speed, accuracy and accessibility are some advantages of this type of sampler over other soil‐tubes.
Nitrogen Fixation by Intact Annual Rangeland Species in Soil1
Authors: Vaughn Charles E. , Jones Milton B.
Published: July 2010

The acetylene reduction technique is widely used as an assay of N2 fixation, but its application to intact N2‐fixing systems in soil has been limited. The purpose of this research was to develop methods suitable for short‐duration assays of entire nitrogenase systems and to utilize these methods in studies of N2 fixation by annual rangeland species growing intact in potted soil.

Experiments conducted with nodules excised from subclover plants (Trifolium subterraneum L.) indicated large diurnal variation in acetylene reduction rates; the greatest activity being observed between 1200 and 1600 hours and the minimum at 0400 hours. All standard assays of intact cultures were conducted between 1200 and 1600 hours to standardize light conditions. The pots were sealed, cultures exposed to an air‐acetylene atmosphere, and ethylene production was measured. Ethylene production rates of intact subclover plants were linear over a 75‐min period if the gases were mixed during an incubation by pumping a syringe inserted through a rubber serum stopper fitted in the bottom of the pot.

Successive biweekly assays of 30 or 60 min duration were conducted on seven species of annual clovers during complete growth cycles. All species exhibited major exponential phases in ethylene production activity which coincided with flowering and seed development. There was a significant linear relationship between ethylene production and both herbage dry matter production and N content. An average of 3.2 moles of ethylene was produced per mole of total plant N contained in four subclover cultures. Ethylene production during a 4‐month period by soil organisms in the rhizosphere of an annual grass, soft chess (Bromus mollis L.), was significantly and inversely related to the amount of fertilizer N applied. Ethylene production was significantly higher in the grass rhizosphere than in comparable fallow soils, except where 160 mg N (100 ppm) was applied to the grass cultures.

The results indicate that these short‐duration, nondestructive assays are of value in making quantitative estimates of N2 fixation. They are particularly useful for repeated samplings of cultures in situ during entire growing seasons.
High‐frequency Trickle Irrigation and Row Spacing Effects on Yield and Quality of Potatoes1
Authors: Phene C. J. , Sanders D. C.
Published: July 2010

Soil water is a major limiting factor in the production and quality of potatoes (Solanum tuberosum L.). The objectives of this research were to determine the effects of trickle irrigation under controlled soil matric potential and two row spacings on the yield, quality, and nutrient contents of potatoes. Potatoes, trickle irrigated with nutrient solution and grown on 100‐cm row spacing (CSI) on sandy loam (Typic Palendult) soil, yielded 76% more marketable potatoes than those trickle irrigated under a plastic mulch and grown on twin row spacing (TRI) and 206% more than 100‐cm spaced, nonirrigated potatoes (CSNI). Water deficit, calculated by subtracting rainfall from 80% of pan evaporation, was 14.0 cm. Soil matric potentials 15 cm from the soil surface were not different for the CSI and TRI treatments irrigated, respectively, with amounts of water equivalent to 60 and 43% of the water deficit. The N and Mg contents of tubers were increased by irrigation. Leaf petiole nitrate N of CSI and TRI potatoes was consistently greater than 16,000 ppm, a critical level for Russett Burbank potato production in Idaho, but fell significantly below that level for the CSNI potatoes after an extended drought.
Effect of Ammonium to Nitrate Ratio on Growth and Anthocyanin Development of Perennial Ryegrass Cultivars1
Authors: Nittler L. W. , Kenny T. J.
Published: July 2010

Improved methods of determining cultivar purity of perennial ryegrass, Lolium perenne L., seed lots, are needed. We conducted studies to find characteristics in which cultivars might differ. Seedlings were grown in sand and were supplied with solutions in which 0, 25, 50, 75, or 100% of the N was NH4 and the remainder was NO3. Growth and anthocyanin development were affected by ratio of ammonium to nitrate. Cultivars differed in both characteristics. Growth, as determined by tiller height, was greatest when plants were grown with 25% of the N as NH4. Anthocyanin development, as determined by percentage of the tiller height showing red color, was greatest when plants were grown with a solution in which 100% of the N was NH4. Cultivar differences in tiller height were greatest when plants were grown with 25% of the N as NH4. Cultivar differences in anthocyanin development were greatest when plants were grown with 75% of the N as NH4. With this solution, cultivars differed in percentage of plants in which red color extended the entire length of the tillers. Both anthocyanin development and tiller height were useful in determining cultivar purity of seed lots.
Effect of Variations in the Shoot:Root Ratio upon the Chemical Composition and Growth of Soybeans1
Authors: Sanders J. L. , Brown D. A.
Published: July 2010

Published data suggest that the soybean root system may be a limiting factor in maximizing soybean yields. The present study measured the effect of the root:shoot ratio upon the growth and yield of soybeans. Research in growth chamber and field evaluated the effect of varying the shoot:root ratio upon nutrient uptake and growth of ‘Lee 68’ soybeans [Glycine max (L.) Merr.]. Grafting prepared seedling plants with varying shoot:root ratios of 1:1, 1:2, 1:3, 2:1, and 3:1. The grafted plants performed vigorously in both the growth chamber and field. Grafted plants were analyzed for N, P, K, Ca, Mg, Na, Fe, Mn, Zn, and Cu. Increasing the number of shoots gave increases in the total nutrient uptake but the magnitude was not as great as it was from increasing the number of roots. When the number of shoots was increased, the leaf area, number of leaves/plant, seed yield, and number of seeds/plant were increased. However, increasing the number of shoots did not increase the growth characteristics and seed yield as dramatically as increasing the number of roots. Even though the physical shoot:root ratio was varied by grafting, the shoot:root ratio based on the dry weight of plant material remained constant at approximately 10:1.
Effect of P, Ca, and Mg Concentrations in Solution Culture on Growth and Uptake of These Ions by Rice1
Authors: Fageria N. K.
Published: July 2010

Nutrient requirements during various phases of plant growth are affected by many factors. Greater knowledge of this subject is warranted by the intensification of agriculture. The present study was undertaken to determine the effect of varying concentrations of P, Ca, and Mg on the growth and uptake patterns of these ions by rice (Oryza sativa L.). Rice plants were grown in culture solution of these ions. Minimum concentrations required for maximum growth were 25 μM P, 250μM Ca, and 33 μM Mg respectively. At higher P concentrations a linear absorption isotherm was obtained with respect to P content in the plant tissue. The critical concentration of P in the tops of 100‐day old plants was 0.4%. To support maximum growth, Ca content varied from 242 to 2,373 μg‐atoms/five plants for 25 to 125 days of growth. Maximum growth was characterized by a relative absorption (IM) rate ranging from 14 to 320 μg‐atoms of Ca/g dry weight of roots/day during the period of cultivation. To support maximum growth, plants must absorb 13.7, 7.7, 4.3, 4.0, and 2.4 μg of magnesium per g fresh weight of roots/hour at 25, 50, 75, 100, and 125 days of growth respectively. With the advancement of age, P and Ca content in plants and their utilization quotients were increased but relative growth rate and rate of Ca and Mg absorption decreased.
Anatomical Response of Potato Stems and Roots to Soil Moisture and Rates of Fertilizer1
Authors: Singh Gurbachan , Struchtemeyer R. A.
Published: July 2010

This study was conducted to determine the effect of three moisture regimes and three rates of fertilizer on the anatomy of stems and roots of the ‘Katahdin’ cultivar of potato, Solanum tuberosum. A Caribou loam (coarse loamy, mixed frigid Dystric Eutrochrept) was used in a greenhouse experiment. The soil was placed in pots. Fertilizer at rates of 0, 168, and 336 kg N/ha, in a 10‐15‐15 mixture, was used. Soil moisture stresses equivalent to 3C, 50, and 70% depletions of available moisture were allowed to develop. The data showed that the area of the xylem in the stems decreased as soil moisture stress increased. The highest rate of fertilizer reduced the area of the xylem, but increased the diameter of the individual vessels. In the roots the area of xylem and phloem decreased while the area of cortex increased with an increase of soil moisture stress in the 75‐day experiment. The area of xylem tended to increase while the cortical tissue tended to decrease with increases in the rate of fertilization.
Growth of Subterranean Clover in a Range Soil as Affected by Microclimate and Phosphorus Availability. II. Laboratory and Phytotron Studies1
Authors: Osman A. , Raguse C. A. , Sumner D. C.
Published: July 2010

Growth of subterranean clover (Trifolium subterraneum L) seedlings on a soil known to be P‐deficient was studied under controlled‐environment conditions representative of the winter growth period in California's Mediterranean climate annual rangeland.

Ambient air temperature was 20C maximum (4 hours) and 4.4C minimum (12 hours), employing natural photoperiods and light intensities from November to March. Phosphorus treatments were approximately 0, 22, 45, 90, and 180 kg/ha. A P adsorption isotherm was determined for the Sobrante and Las Posas soils used.

Inoculated seeds of ‘Woogenellup’ subterranean clover were seeded into pots containing 3.6 kg of soil. Plants were sampled at the 1.5, 3.0, and 4.5 stages of trifoliolate leaf development for plant weight and P content determinations.

The pots were reseeded with the same cultivar at 30 seeds/dm2 and grown to the five‐leaf stage. Shoots and roots were removed separately and used to determine nodule numbers, shoot and root weights, and P and nitrogen tissue content.

The P adsorption isotherm predicted a fixation capacity of ca 80 and 120 kg/ha at equilibrium solution values of 0.1 and 0.2 ppm P respectively.

Plant weights were significantly affected by P rates only at the 3.0 and 4.5 leaf stages. Total P per plant was a more consistent indicator of P availability than was percent P. Shoot:root ratios, nodules per plant, and percent crude protein in shoot and root increased with P availability.

Fertilizer application rates that provide a minimum soil‐solution level of 0.2 ppm P are indicated for optimal subterranean clover growth during Mediterranean climate winter conditions.
Yield Loss of Corn Due to Corn Stunt Disease Complex1
Authors: Scott Gene E. , Rosenkranz Eugene E. , Nelson Loyd R.
Published: July 2010

The seriousness of a disease is reflected in the amount of yield reduction caused by the disease under field conditions. We wished to obtain data on the amount of yield loss of corn (Zea mays L.) caused by the corn stunt disease complex which includes the maize chlorotic dwarf virus (also referred to as Ohio corn stunt agent) and the Mississippi corn stunt agent, believed to be a mycoplasma; and to determine if time of initial disease symptoms influences the amount of yield reduction. Corn hybrids were subjected to natural infection under field conditions during 5 years. Plants showing disease symptoms were tagged and yields from these plants were compared with plants not showing disease symptoms. Yields from diseased plants were less than 50% of those from healthy plants in each of the 5 years. The number of ears and kernels per plant was reduced more than was the weight of kernels on the diseased plants. Plants showing disease symptoms early in the season were more severely affected than plants that developed symptoms later. From our data, we concluded the following: diseased plants showing symptoms as early as 52 days after planting would produce no grain; plants showing first symptoms as late as 107 days after planting would produce normal yield; between the two extremes the yields on diseased plants would be reduced by 1.82% of that on healthy plants for each day the first symptoms appeared earlier than 107 days after planting.