bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrolytic Enzyme Differences in Cold‐Tolerant and Cold‐Sensitive Alfalfa1,2
Authors: Krasnuk M. , Witham F. H. , Jung G. A.
Published: July 2010

This investigation was part of a continuing effort to ascertain the role of soluble proteins in the development of cold tolerance of alfalfa, Medicago sativa L. The research was conducted to determine whether certain soluble proteins, known to be closely associated with the development of cold tolerance, exhibited hydrolytic enzyme activity. Cold‐tolerant ‘Vernal’ and cold‐sensitive ‘Sonora’ alfalfa plants grown for 66 days under simulated “summer” (nonhardening) and “winter” (hardening) conditions exhibited different levels of cold tolerance as indicated, by cold tolerance assays performed at three freezing temperatures. Sonora winter plants were only moderately tolerant to −6 C, whereas Vernal plants were well hardened to −8 C and were tolerant to −10 C. Soluble protein concentrations were higher in hardened than in unhardened plants, with differences in protein concentration greater for Sonora than Vernal. Localization of hydrolytic enzymes on polyacrylamide gels after disc electrophoresis and subsequent densitometric scanning of zymograms demonstrated that activities of amylases, leucine amino peptidases, and α‐esterases were greater in winter than summer samples of both cultivars; whereas ATPase activities were lower in winter than summer samples. Furthermore, differences between αaesterase levels of hardened and unhardened samples were greater than those of amylase or peptidase. New esterase forms and higher quantities of a heat‐stable amylase also were detected in hardened samples. Differences in enzyme solubility between distilled water and tris‐HCl extracts, related to environment, extractant, or cultivar influences, were evident for esterases and ATPase and for individual forms of amylase and peptidase. The large quantitative changes in amylases and esterases localized within gel column regions 7 and 8 of hardened Vernal zymograms implied a close relationship of these hydrolytic enzymes to the hardening process; whereas the decreased ATPase activities reflected an inverse relationship with cold tolerance. It is, therefore, reasonable to conclude that quantitative and qualitative differences in hydrolytic enzyme activity are evident between hardened and nonhardened plants. The differences among hydrolytic enzymes do not necessarily follow the same quantitative or qualitative pattern, and for this reason they should be studied collectively to understand the biochemistry of hardening.
Dehydrogenase Levels in Cold‐Tolerant and Cold‐Sensitive Alfalfa1,2
Authors: Krasnuk M. , Jung G. A. , Witham F. H.
Published: July 2010

Certain soluble proteins are believed to be closely associated with cold tolerance. The objectives of this work were to determine whether the proteins exhibited dehydrogenase activity and if there were qualitative and/or quantitative differences in dehydrogenases between hardened and nonhardened plants. Cold‐tolerant ‘Vernal’ and cold‐sensitive ‘Sonora’ alfalfa (Medicago sativa L.) plants were grown for 66 days under simulated summer (non‐hardening) and winter (hardening) conditions, using growth chambers, and were assayed for the levels of cold tolerance developed at three freezing temperatures (−6, −8, and −10 C). To determine differences in dehydrogenases, soluble proteins were separated from extracts of crown and root tissues by polyacrylamide disc gel electrophoresis. Localization of dehydrogenases on gels and densitometric scanning of zymograms indicated that activities of glutamate, lactate, isocitrate, glucose‐6‐phosphate, 6‐phosphogluconate, nicotinamide adenine dinucleotide (NAD) malate and nicotinamide adenine dinucleotide phosphate (NADP) malate dehydrogenases were high in both cultivars exposed to hardening and were generally highest in Vernal. Percent increases for winter over summer levels of glutamate, lactate, glucose‐6‐phosphate, and 6‐phosphogluconate dehydrogenases were large compared with those of isocitrate, NAD‐malate, and NADP‐malate dehydrogenases. Moreover, the magnitude of change in enzyme activity between summer and winter plants also was influenced by extractant (distilled water, pH 7 or 0.10 M tris‐HCl, pH 7) and varied quantitatively according to the solubility of the dehydrogenases in the two extractants. Enzyme solubility differences related to cultivar or environmental influences and cold tolerance were also observed, especially for isocitrate dehydrogenase. Large quantitative differences in glucose‐6‐phosphate and lactate dehydrogenase activities and substantial increases in isocitrate and 6‐phosphogluconate dehydrogenases localized within gel column regions 7 and 8 of zymograms developed from winter samples implied a close relationship of these enzymes to cold tolerance. Forms of lactate, glucose‐6‐phosphate, and isocitrate dehydrogenases were present in hardened tissues that were not present in un‐hardened tissues. It is concluded that the observed differences in dehydrogenasees between hardened and non‐hardened plants are major indicators of the cold tolerant state. Based on these and past studies, the reactions analyzed by representative hydrolytic and dehydrogenase enzymes may serve as a working hypothesis for future studies concerning the mechanics of induction and the suspected catenary nature of the hardening process.
Influence of Manure Application Rates and Continuous Corn on Soil‐N1
Authors: Magdoff F. R.
Published: July 2010

Manure application to continuous corn (Zea mays L.) should provide some or all of the crop N needs and help maintain or increase soil organic matter. This should be done without damaging the environment by adding excess nutrients to ground or surface waters. A range of factors may influence manure decomposition, and hence N availability to crops. However, application recommendations are usually not site specific. To attempt to deal with site specific considerations, a comparison was made of the effect of manure on soil‐N and crop response to inorganic‐N between similar continuous corn experiments at two different sites.

The manure‐N experiments with continuous corn were conducted on both a somewhat poorly drained Panton clay (Typic Ochraqualf) and a well‐drained Calais loam (Typic Fragiorthod). Manure rates of 0, 22, 44, and 66 metric tons/ha/year were combined in factorial arrangement with ammonium nitrate rates of 0, 112, and 224 kg N/ha/year. Comparison of calculated theoretical soil‐N with experimentally determined levels after 5 years and the response of corn to fertializer‐N indicate that mineralization of manure organic‐N, when applied to the Panton clay, was less than when applied to the Calais loam. Thus, manure‐N was less available to the growing crop on the clay and accumulated in the soil at a greater rate than in the loam. The annual manure application rates required to maintain initial soil N levels in Panton clay and Calais loam under continuous corn production were calculated to be 40 to 52 tons/ha respectively. Two mineralization models were examined: Model 1 assumed only the first year manure mineralization rate above native soil organic matter decomposition rate; Model 2 assumed a 5‐year mineralization decay series. Both were effective in predicting final soil‐N levels.
Leaf Temperature and Internal Water Status of Wheat Grown at Different Root Temperatures1
Authors: Kirkham M. B. , Ahring R. M.
Published: July 2010

Both root temperature and plant water status are important in controlling plant growth. Yet few studies report the influence of root temperature on the water relations of plants. Therefore, to determine the effect of root temperature on leaf temperature and internal water status, a cultivar of winter wheat (Triticum aestivum L. em Thell. ‘Ponca’), considered to be drought sensitive, was grown for 82 days, under growth room conditions, at six different root temperatures (15.6, 19.9, 24.7, 28.5, 32.1 and 37.3 C). The air temperature remained constant at 25 C. Leaf temperature and stomatal resistance were measured daily starting on day 18. Leaf water, osmotic, and turgor potentials were determined every other day starting on day 44. No seeds germinated at 37.3 C. During the experiment, leaf temperatures were lower than air temperature by 1.46, 1.16, 1.12, 0.98, and 0.71 C for the 15.6, 19.9, 24.7, 28.5 and 32.1 C root temperatures, respectively. Stomatal resistances averaged 21.5, 19.9, 19.8, 22.1, and 27.4 sec/cm for the 15.6, 19.9, 24.7, 28.5, and 32.1 C root temperatures, respectively. Leaf water, osmotic, and turgor potentials were highest at the 24.7 C root temperature. Potentials were lowest at the highest root temperature (32.1 C). The experiment was repeated using a wheat cultivar considered to be drought resistant (‘KanKing’). KanKing seeds germinated at 37.3 C. For KanKing, leaf temperatures were cooler than air temperature by 1.75, 1.51, 1.36, 1.32, and 1.02 C for the 15.6, 19.9, 24.7, 28.5, and 32.1 C root temperatures, respectively. Stomatal resistances averaged 44.6, 41.9, 33.5, 37.0, and 37.4 sec/cm for the 15.6, 19.9, 24.7, 28.5, and 32.1 C root temperatures, respectively. Potentials were not determined for KanKing. The drought sensitive cultivar grew taller than the drought resistant cultivar. But the heights of both cultivars, decreased in the following order with root temperature: 24.7, 28.5, 19.9, 15.6, and 32.1 C. The results showed that the drought resistant cultivar maintained a larger difference between leaf and air temperature at the different root temperatures than did the drought sensitive cultivar. This suggested that leaf temperature measurements could be used to screen plants for drought resistance.
A Tractor‐Mounted Row Marker Using a Rotating Barrel1
Authors: Cobb D. L. , Doyle B. L. , Webster J. A. , Smith D. H. , Ries D. K.
Published: July 2010

Small, portable, row markers that can be transported easily to off‐station cereal nursery sites are needed. We designed a marker, consisting of a rotating barrel attached to a 3‐point hitch frame. Angle‐iron pieces, attached lengthwise to the barrel sides, mark the rows in the soil as the unit is pulled by a tractor. Chains attached around the barrel mark alleys perpendicularly to the rows. This method has been successfully used in large nurseries and in small, specialized nurseries that are used for plant resistance studies.
Effect of Fertilization on Penncross Creeping Bentgrass1
Authors: Waddington D. V. , Turner T. R. , Duich J. M. , Moberg E. L.
Published: July 2010

Although turfgrass fertilization influences many factors that affect turfgrass quality, little information is presently available that encompasses the interrelationships between fertilization, soil fertility, and turfgrass response and quality. A field study was conducted on Hagerstown soil (fine, mixed, mesic Typic Hapludalf) to determine the effects of N sources (Agrinite, Milorganite, ureaform, and urea), P rates (0, 0.49, 0.98, and 1.95 kg/100 m2), and K rates (0, 0.76, and 1.52 kg/100 m2) on soil nutrient levels and the growth, quality, and chemical composition of ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) maintained as putting green turf. Wilting, disease, chlorosis, and annual bluegrass (Poa annua L.) infestation were used to assess quality.

Fertilization with Milorganite increased available soil P and Mg. Available P and K in the soil ranged from 11 to 94 ppm and 0.06 to 0.28 meq/100 g, respectively. Elemental content of clippings was affected by all treatments, and treatment × date of sampling interactions that occurred could limit the usefulness of tissue analyses for diagnosing the nutritional status of turfgrasses.

When K was applied at 0.76 kg/100 m2, both tissue and available soil K increased. When the K rate was increased to 1.52 kg/100 m2, the additional increment of K caused a greater increase in soil K and a smaller increase in tissue K than was obtained with the first increment of added K. The greatest change in tissue P occurred with the first incremental addition of P. Tissue P was not greatly affected by soil P above 24 ppm. Phosphorus fertilization had little effect on clipping yield; however, K fertilization tended to increase growth, as well as decrease chlorosis noted in early spring. Less severe summer wilting was observed with Agrinite, Milorganite, and K treatments. Less dollar spot (Sclerotinia homoecarpa F. T. Bennett) infection was noted with urea fertilization. Annual bluegrass invasion was favored by P and K fertilization and the effect of one was enhanced by the other. Milorganite, which increased soil P, also favored annual bluegrass. Results of this study indicated a need for more work in soil test calibration for turfgrasses.
Growth and Water Relations of Cereal Crops as Influenced by Salinity and Relative Humidity1
Authors: Hoffman G. J. , Jobes J. A.
Published: July 2010

Crop salt tolerance is not absolute but depends on environmental factors such as relative humidity (RH), as well as management of irrigation and fertility. The objective of this study was to evaluate the influence of atmospheric relative humidity on plant growth and how it interacts with salinity to influence salt tolerance and water relations of barley (Hordeum vulgaris L. ‘CM‐67’), wheat (Triticum aestivum L. ‘Siete Cerros’), and sweet corn (Zea mays L. ‘Bonanza’). The studies were conducted in sunlit climate chambers with temperatures cycled daily between 10 and 27 C for barley and wheat and between 17 and 32 C for corn and with average daytime RH controlled near 45% for the low and near 90% for the high RH treatments. The root medium of each crop was maintained at four different osmotic potentials (s Ψo), the range depending on the crop's salt tolerance. With a nonsaline root medium, increasing the RH from 45 to 90%, increased the wheat yield by 24%, had no influence on corn yield, and reduced barley yield by 16%. High RH increased the salt tolerance of barley and corn but did not affect the tolerance of wheat. For all three crops at all sΨo levels, water‐use efficiency (yield per unit of water consumed) was higher at 90% than at 45% RH. Linear relationships were found between leaf total water (LΨt) and osmotic (LΨo) potentials and sΨo for barley and wheat. Leaf pressure potential (LΨp) was reduced by low RH and salinity. The relationship between crop yield and LΨt was linear. The difference between full yield and almost no yield was 2.0 megaPascals for both barley and wheat. RH must be considered when evaluating the salt tolerance of barley and corn but not for wheat.
Influence of Soil Moisture and Plant Cultivar on Cation Uptake by Wheat with Respect to Grass Tetany1
Authors: Karlen D. L. , Ellis R. , Whitney D. A. , Grunes D. L.
Published: July 2010

Several researchers' report that the incidence of grass tetany is most severe when soils are nearly water‐saturated. This report prompted three growth‐chamber studies to determine the influence of soil moisture and wheat cultivar on K+, Ca++, and Mg++ ion uptake and the estimated tetany potential of wheat forage. Hard red winter wheat (Triticum aestivum L. ‘Centurk’, ‘Eagle’, and ‘Newton’) was grown in pots containing 2 kg of Eudora loam (Fluventic Hapludoll) soil. Two soil moisture levels (13 and 27 volume %) were maintained by weighing the pots and watering daily. Final pot weights were increased periodically to account for plant growth. In samplings where cation concentrations were significantly different, K concentrations in leaf, crown, and root tissue from plants grown at 27% moisture decreased 0.10%, increased 0.29%, and increased 0.58% respectively; Ca concentrations decreased 0.12%, 0.05%, and 0.35%, respectively; Mg concentrations decreased 0.01%, 0.02%, and 0.06%, respectively. The equivalent ratio K/(Ca + Mg) in the three plant parts increased 0.49, 0.53, and 0.92, respectively. The average Mg concentration in the root tissue (0.22%) was higher than in either the crown (0.16%) or leaf (0.18%) tissue, indicating that among other factors contributing to low forage Mg, there might be translocation mechanisms that limit the movement of Mg into leaf tissue. Analysis of non‐vernalized wheat tissue showed significant cultivar differences. Average K concentrations in Eagle wheat (6.29%) were greater than in either Newton or Centurk wheat (5.94 and 5.52%, respectively); Ca and Mg concentrations in Eagle wheat (0.823 and 0.193%) were lower than Ca and Mg concentrations in Newton and Centurk wheat (0.980 and 0.222%; 0.940 and 0.217%, respectively). These differences in cation composition resulted in an average equivalent ratio in Eagle wheat of 2.80 compared to 2.27 and 2.28 in Newton and Centurk wheat, respectively. Cation concentrations in the samplings of vernalized wheat showed no significant cultivar differences; however, average equivalent ratios for Newton, Centurk, and Eagle wheat (2.56, 3.00, and 3.47, respectively) were significantly different. This result indicated that Eagle wheat would be a more tetany‐prone forage than either Newton or Centurk wheat. These studies have shown that soil moisture content, cultivar, and possibly translocation mechanisms influence the cation concentrations of wheat forage. They also indicate that perhaps a breeding program could be developed to produce wheat cultivars that have a more balanced cation composition and a lower potential for inducing grass tetany in grazing cattle than those now grown.
Soybean Root Growth during the Reproductive Stages of Development1
Authors: Kaspar T. C. , Stanley C. D. , Taylor H. M.
Published: July 2010

Controversy exists concerning photosynthate sink relationships associated with seed development and their effects on soybean (Glycine max (L.) Merr.) root development. Seven cultivars were studied in the Ames rhizotron (root observation laboratory) to determine the rate which each cultivar increases its rooting depth during flowering and seed development. Depth of rooting and stage of development were measured three times a week from 16 June to 30 Aug. 1976. Rooting depth continued to increase until the maximum depth of each rhizotron compartment (217 cm) was reached. Some root growth occurred until physiological maturity (R 7). The maximum rate of downward root growth occurred during early flowering (R1 to R3) for all seven cultivars. Cultivars differed significantly in the rate of downward growth during the periods between planting and growth stage R1, R1 and R2, and R5 and R6. The cultivar ‘Hawkeye’ had the greatest rate of downward growth (8.1 cm/day) between the R1 and the R2 stages, and ‘Beeson’ had the greatest overall rate (2.8 cm/day).
Effect of Soil Temperature on Development of Perennial Forage Grasses1
Authors: Morrow L. A. , Power J. F.
Published: July 2010

Soil temperature has a great influence on the development and establishment of all types of plants. The lack of soil temperature information on the development of perennial forage grasses led to the initiation of this study. Seedlings of crested wheatgrass [Agropyron desertorum Fisch. (Schult.)], western wheatgrass (A. smithii Rydb.). smooth brome (Bromus inermis Leyss.), Altai wildrye (Elymus angustus Trin.), Russian wildrye (E. junceus Fisch.). green neellegrass (Stipa viridula Trin.), sideoats grama [Bouteloua curtipendula (Michx.) Torr.], and blue grama [B. gracilis (H.B.K.) Lag. ex Steud.] were grown in a Temvik silt loam soil (typic Haploborolls, fine , silty, mixed) for 12 weeks in a growth room at soil temperatures ranging from 3.3 to 33.3 C in 5 C increments. Air temperature was held constant and a 16‐hour photo period was used. Plant height and water use were measured weekly and dry matter and nitrogen concentration were measured at the conclusion of the study. Crested wheatgrass, Altai wildrye, and green needlegrass reached maximum aboveground dry matter production at 23.3 C. Western wheatgrass, smooth brome, and Russian wildrye produced the most aboveground dry matter at 18.3 C. Crested wheatgrass was the most efficient in water use. Root dry matter production was greatest at 18.3 C for most grasses. Nitrogen concentration of aboveground tissue was usually greatest at soil temperatures of 18.3 or less but all grasses contained sufficient N for grazing livestock. Of the grasses studied, crested wheatgrass, western wheatgrass, and smooth brome appear to be best for dry matter forage production under northern Great Plains climatic conditions.
Foliar Application of P. I. Screening of Various Inorganic and Organic P Compounds1
Authors: Barel D. , Black C. A.
Published: July 2010

The suitability of 32 different P compounds for foliar application was tested by using a new technique in which predetermined quantities of P were applied to a fixed leaf area. This made it possible to obtain quantitative data on absorption of added P and on translocation of absorbed P out of the treated area. Presently foliar applications of P are used less than N, one reason being that no P compound is available which can be sprayed on plants in large enough quantities without damaging the leaves. Several representatives of the condensed phosphates and some compounds containing P‐N bonds or P‐N‐P linkages proved promising. Both group of compounds hydrolyze spontaneously to release orthophosphate, and all share the quality of delayed action. These P sources could be applied at 2.5 to 3 times the quantity of P that could be applied as orthophosphate in a greenhouse experiment without causing leaf damage. The most successful compound for corn (Zea mays L.) was ammonium tripolyphosphate, which could be applied at 370 µg of P/cm2 without causing leaf damage; 66% of the applied P was absorbed within 10 days, and 87% of the absorbed P was translocated out of the area of application in the same period. Other successful compounds for corn were ammonium tetrapolyphosphate and phosphoryl triamide. Soybeans (Glycine max L. Merr.) proved more sensitive than corn and could, in general, tolerate only two‐thirds to three‐fourths of the quantity of the various compounds that could be applied to corn, with the exception of phosphonitrilic hexaamide, which could be applied at 340 µg of P/cm2. Ammonium tri‐ and tetrapolyphosphate could be applied at 220 µg of P/cm2 to soybeans. Rapid intake is suspected to be an important reason for the damage observed with orthophosphate. Several organic P compounds were tested, but none of them was superior to the condensed P sources.
Alachlor and Trifluralin Effects on Nutrient Uptake in Oats and Soybeans1
Authors: Bucholtz D. L. , Lavy T. L.
Published: July 2010

Alachlor [2‐chloro‐2′,6′‐diethyl‐N‐(methoxymethyl)acetanilide] and trifluralin (α,α,α‐trifluoro‐2,6‐dinitro‐N,N‐dipropyl‐p‐toluidine) have been reported by several investigators to inhibit root growth in a variety ot plants. However, the biochemical significance of this inhibition is not known. The inhibition of root growth could interfere wth the uptake of plant nutrients. The greenhouse experiments of the present study were conducted to determine what effects the herbicides, alachlor and trifluralin have on the growth and on the uptake of H32PO2−4 and 35SO2−4 of oats (Avena sativa L. ‘Neal’) and soybeans [Glycine max (L.) Merr. ‘Clark 63’]. Oats is regarded as an alachlor and trifluralin‐sensitive species, and soybean is regarded as an alachlor and triflurafin‐tolerant species. Root weight of both species was reduced with increasing concentrations of both soil‐incorporated herbicides. The reduced root biomass of soybean was accompanied by a proportional reduction in shoot biomass, but in oats the shoot biomass was reduced more than the root biomass. Root biomass and the accumulation of H32PO2−4 and 35SO2−4 in oat and soybean shoots were directly correlated.

Alachlor and trifluralin altered biochemical processes in oats and soybeans which control root and shoot growth. The herbicides selectively altered the plants' abilities to absorb H32PO2−4 and 35SO2−4.
Leaf Water Potential and Gaseous Exchange of Wheat and Tomato as Affected by NaCl and P Levels in the Root Medium1
Authors: Cerda Antonio , Bingham F. T. , Hoffman G. J. , Huszar C. K.
Published: July 2010

The phosphorus nutritional status of some plants has been shown to influence the plant's response to salinity. The objective of this study was to determine if this interaction influenced the plant's water relations, fixation of CO2, and yield. Tomato (Lycopersicon esculentum Mill.) and wheat (Triticum aestivum L.) were grown to maturity in nutrient solution cultures containing low to excessive concentrations of NaCl and P.

Leaf total water potential (Lψt) and its components, osmotic (Lψo) and pressure (Lψp), decreased for both crops as salinity levels increased. Increases in the P concentration tended to increase Lψt and Lψo but decrease Lψp, although the changes were not always consistent. Interactions between salinity and P treatments caused significant differences in Lψt and Lψp for wheat. Statistically significant multiple regression equations were developed for Lψt, Lψo, and Lψp as a function of NaCl and P concentrations for both crops. Plant yields were well‐correlated with Lψt and Lψo, indicating that these measurements may provide a good characterization of salt stress.

Measurements of leaf stomatal diffusion resistance to water vapor (rH2O) and carbon dioxide (rCO2) and calculated values of mesophyll resistance (rm) increased significantly as salinity increased for tomato. Although the resistance values for wheat also increased as salinity increased, only the rCO2 measurements rose significantly. The significant increases in rCO2 and rm for tomato with additions of salinity indicate a significant reduction in the rate of photosynthesis. Increasing P values consistently reduced the gaseous resistance levels although the reductions were not always statistically significant. There were no significant interactions between salinity and P treatments for any of these resistance measurements.
Production and Quality of Limpograss for Use in the Subtropics1
Authors: Kretschmer Albert E. , Snyder George H.
Published: July 2010

‘Greenalta’, ‘Redalta’, and particularly ‘Bigalta’ limpograsses [Hemarthria altissima (Pior.) Stapf and Hubbard] have been commercially planted in south Florida during the past decade. Since little information is available on agronomic attributes of limpograss during the cool‐season when tropical grass growth is markedly reduced, cool‐season productivity and in vitro organic matter digestibility (IVOMD) were compared with other commercial tropical grasses adapted to south Florida.

Effects of nitrogen rates, cutting interval, and fall fertilization dates also were determined for Bigalta to provide information on productivity and IVOMD. The soil used was an Oldsmar fs, a spodosol.

The three limpograss cultivars, ‘Transvala’ digitgrass (Digitaria decumbens Stent.), and ‘Coastcross‐1’ bermudagrass (Cynodon sp.) were equally productive during the cool season and more productive than ‘Pangola’ digitgrass (Digitaria decumbens Stent.), Bigalta IVOMD generally was greater than that of Greenalta and particularly Redalta, equal to that of Transvala and Pangola, and higher than that of Coastcross‐1. Dry matter yields of Bigalta, Coastcross‐1‐ and Transvala were similar at 3 or 4‐week cutting intervals (CI), but Bigalta produced less at a 2‐week CI. During a 24‐week period as CI increased from 4 to 12 weeks (total of 336 kg N/ha applied), Bigalta total yields increased, forage IVOMD and N contents decreased, and yield of digestible organic matter increased. Delaying fall fertilization from 17 September or 1 October until 29 October resulted in greatly reduced forage production when harvested on 17 December. The IVOMD and N contents increased as fertilization was delayed. Many of the N contents from the fertilization date and CI studies were below the acceptable level for maximum voluntary intake of forage by ruminants.

Productivity of the limpograsses and Bigalta response to N during the cool season indicate that they offer alternatives to other commercially available tropical grasses. The high digestibility of Bigalta can provide reserve coolseason pasture with quality equal to or better than that from other grasses, however, low N contents may limit intake without proper grass management and N fertilization.
Substitution Value of Birdsfoot Trefoil for Alfalfa‐Grass in Pasture Systems1
Authors: Marten G. C. , Jordan R. M.
Published: July 2010

Conventional alfalfa (Medicago sativa L.)‐gass grazing systems do not permit sufficiently high animal intake of energy for high roducing ruminant animals. Provision of pasture swards containing a higher proportion of legume should increase energy intake. Our primary objective was to determine whether lamb daily gains could be increased by increasing the legume percentage in grazing systems via substitution of pure birdsfoot trefoil (Lotus corniculatus L) for alfalfagass as one‐third of the total rotational pasture. We compared four grazing systems for lambs in each of 3 years. The control system had an alfalfa‐smooth bromegrass (Bromus inermis Leyss.)‐orchardgrass (Dactylis glomerata L.) mixture in each of three rotationally grazed paddocks. A second system had orchardgrass in paddock 1, reed canarygrass (Phalaris arundinacea L.) in paddock 2, and smooth bromegrass in paddock 3; each grass was mixed with alfalfa. In the third and fourth systems paddocks 1 and 2 were identical to those in the control; paddock 3 in these systems had pure birdsfoot trefoil either grazed in sequence in late May or stockpiled for initial grazing in late June.

Substitution of birdsfoot trefoil for alfalfa‐grass as one‐third of total seasonal pasture resulted in 22 to 24% increases in lamb average daily gains over a 3‐year period. The birdsfoot trefoil‐containing systems provided forage that had significantly higher legume composition, in vitro digestibility, crude protein concentration, and ap parent intake potential (lower concentration of cell walls) than did forage provided by the control (all alfalfa‐grass) system. The sometimes lower carrying capacity of the birdsfoot trefoil containing systems partly offset the greater gains of lambs on these systems. However, they provided a mean 17 to 18% increase in lamb product perha, com ared with all alfalfa‐grass systems. The birdsfoot trefoil containing systems also had lower overhead costs, because fewer animal units were required per unit of gain.

The stage of maturation of birdsfoot trefoil at first grazing each year (immature vs. stockpiled) did not significantly influence animal performance or birdsfoot trefoil persistence. Use of a mixture of alfalfa‐smooth bromegrass‐orchardgrass in all paddocks (control), compared to orchardgrass, reed canarygrass, or smooth bromegrass as single species mixed with alfalfa in individual pad. docks, did not influence animal performance.

A “pasture‐type,” creeping rooted alfalfa cultivar (‘Rambler’) did not persist as well as two “hay‐type” cultivars (‘Saranac’ and ‘Agate’). Invasion of weeds in the 3rd year proved to be a disadvantage of using pure stands of birdsfoot trefoil in grazing systems.
Yield and Rooting Activity of Forage Grasses on a Surface‐mined Soil of Texas1
Authors: Hons F. M. , Hossner L. R. , Whiteley E. L.
Published: July 2010

Lignite mining is an expanding industry within Texas. Little or no research has been reported concerning forage production and revegetation following disturbance in this region. Forage plots were established in 1975 to determine the effect of disturbance upon forage production in an area which had been surface‐mined for lig nite in 1972.

The mined soil was originally classified in the fine , montmorillonitic, thermic family of Udertic Paleustalfs. Forages used included NK‐37 bermudagrass (Cynodon dactylon L. Pers.), Pensacola bahiagrass (Paspalum notatum Flugge), coastal bermudagrass (Cynodon dactylon L. Pers.), and Kleingrass (Panicum coloratum L.)

Forage production on the mined soil was comparable to or greater than yields reported on unmined Soils at similar rates of N application. Nitrogen applications were much more significant in determining forage yields than were P additions.

Surface soils were finer in texture following mining due to the mixing of the profile in the mining process. The mined soil possessed a greater percentage of water at field capacity than did an unmined surface soil, primarily because of the finer texture after mining. The potentially increased moisture holding capacity may account for production comparable to that reported for unmined soils with less total moisture received.

The total rooting mass for coastal bermudagrass on the mined soil was approximately three times greater than the root mass observed on a soil genetically related to the unmined soils of the region. Increased rooting activity may result from the destruction of the dense claypan associated with the soil before mining plus the potentially increased moisture holding capacity of the soil following mining.
A Microplot Seeder1
Authors: McLaughlin N. B. , Townley‐Smith T. F. , Dyck F. B.
Published: July 2010

Plots with short rows provide an attractive alternative to hill plantings where seed or space is scarce. The lower planting density in short rows allows for more normal phenotypic expression and easier separation of individual plants. This paper describes an attachment for the Swift Current self‐propelled plot seeder for sowing 0.5 m rows perpendicular to the direction of travel. The attachment consists of a spade‐type opener supported by a linkage which allows it to move in a vertical plane, a seed distribution system, and a control system. Hydraulic cylinders automatically move the opener up and down and open and close the opener blades. In the down position, a 0.5 m long furrow is opened and seeds are dropped into the furrow; in the up position, the opener advances to the next row. The automatic control system both controls and synchronizes the opener movements and the dropping of seeds to ground speed. Border rows can be sown at either end of the micro plots and parallel to the direction of travel with the outside two double disc openers on the seeder.
A Model for Predicting Soybean Yields from Climatic Data1
Authors: Hill R. W. , Johnson D. R. , Ryan K. H.
Published: July 2010

The single most important factor that influences soybean (Glycine max (L.) Merr.) yields from one location to another, or from one year to the next, is moisture availability. A better understanding of how water influences yields is essential for maximizing yields through water management practices. The objective of this study was to develop a model that determines soybean yield as a function of moisture availability during four periods of growth.

Data inputs include the amount of soil water in storage at the beginning of the season, available soil water storage capacity for the root zone, and daily values of rainfall, irrigation, maximum and minimum temperatures, and specific parameters for each cultivar that relate phenology to daylength and temperature.

The program predicts yield as a function of the relative transpiration during each of four growth periods: emergence to beginning flowering; beginning flowering to beginning podfill; beginning podfill to end of flowering; end of flowering to maturity.

When the program is used for scheduling irrigation, the required amount and timing of irrigation water for any planting date is determined by simulating the effects of applying supplemental water in incremental amounts and times. The “best” resultant irrigation scheduling is indicated for any pre‐selected yield level.

The program does not eliminate the need for field trials, but it can be used for identifying management practices that will maximize yields through water management or the avoidance of dry periods. Thus, field research can be concentrated on problem areas with resultant savings of time and money.
Field Assessment of Air Pollution‐induced Soybean Yield Losses1
Authors: Howell R. K. , Koch E. J. , Rose L. P.
Published: July 2010

Estimates of soybean [Glycine max (L.) Merr.] yield losses induced by ambient concentrations of air pollutants are ambiguous, but such estimates are Erequently requested and reported. The objectives and justification of this field experiment were to answer the questions: 1) What soybean yield losses are attributable to air pollution and 2) Do open‐top chambers properly estimate the impact of air pollution on soybean yields? An experiment including cylindrical open‐top field chambers was established in 1973 at Queenstown, Md., on a Mattapex (Typic hapludults) silt loam and repeated in 1974 and 1975 to estimate seed yields of soybean cultivars ‘York,’ ‘Dare,’ ‘Cutler,’ and ‘Clark.’ Yields were com ared for plants growing in chambers (3 m diam an8 2.4 m height) equipped to provide carbon‐filtered air or unfiltered air, and in no‐chamber plots. Treatments were arrayed as four replications of a randomized complete block design with quadrants and cultivars forming a 4 ✕ 4 Latin square as a split‐plot for each environment. Concentrations of photochemical oxidants at the experimental site varied by year and within years, but were comparable to concentrations measured near Washington, D.C. During the 3 years, there was no significant cultivar ✕ environment interaction. Mean seed yields from plants grown in nonfiltered air chambers (24.0 quintals/ha) were significantly lower than those grown in either carbon‐filtered air chambers (30.0 quintals/ha) or in nochamber plots (30.2 quintals/ha). We could not demonstrate that carbon‐filtered air would significantly improve soybean yields over yields of commercially field grown soybeans in this 3‐year test. The 20% yield difference between yields of plants grown in carbon‐filtered air and in nonfiltered air may be an artifact of the chambers and not a true estimate for air pollution induced soybean yield losses. Soybean seed sizes were significantly increased by drought and by carbon‐filtered air.
Leaf Area Index Estimates for Wheat from LANDSAT and Their Implications for Evapotranspiration and Crop Modeling1
Authors: Wiegand C. L. , Richardson A. J. , Kanemasu E. T.
Published: July 2010

Ground measurements of leaf area index (LAI) are tedious and costly. If they could be estimated spectrally from earth observation satellite data, evapotranspiration and photosynthesis models that use LAI as inputs could be implemented for large areas. Thus, we related LAI measurements of winter wheat (Triticum aestivum, L.) made in Kansas during the 1974–1975 and 1975–1976 growing seasons to three spectral vegetation indexes in the literature: transformed vegetation index (TVI), green vegetation index (GVI), and perpendicular vegetation index (PVI). The three vegetation indexes were each significantly linearly correlated (r = 0.70** to 0.95**) with measured LAI from the time LA1 was ≃ 0.3 until plant senescence, and their seasonal time courses were similar to those of directly measured LAI. Thus the indexes capture information on crop development and growing conditions manifested by LAI. We conclude that LAI can be calibrated in terms of the vegetation indexes to provide crop model inputs for as many fields as are of interest, or can serve as an independent check on model calculations when not used as a direct input to physical and physiological process models affected by the amount of vegetation present.
Growth and Water Relations of Wheat Plants with Roots Split Between Soil and Nutrient Solution1
Authors: Erickson P. I. , Kirkham M. B.
Published: July 2010

Soil matric potential controls plant growth. Yet it is difficult to determine the effect of soil matric potential, by itself, on plant water relationships and growth. One way to isolate matric potential is to split roots between soil and nutrient solution because the soil has a matric potential while the nutrient solution has a matric potential of zero. Therefore, in this study, leaf water potential, stomatal resistance, rate of water use, leaf area, plant height, and root length of winter wheat (Triticum aestivum L. em. Thell. cv. Osage), grown with and without wind, and with roots split between soil:soil, soil: nutrient solution (soln), and soln:soln were measured to determine the effect of soil matric potential on wheat water relationships and growth. During the first 16 days of the 38‐day experiment, the soil (Kirkland silt loam, Udertic Paleustoll) was well‐watered. Water was withheld from all soil treatments after the 16th day. Plants were grown with and without wind, and with and without soil drought, because, in the Great Plains, wind and drought, or a combination of the two, are the main causes of crop loss.

Leaf water potential and stomatal resistance of plants with roots in soi1:soln were usually between those of plants with roots in soil:soin and soln:soln. Plants with all roots in nutrient solution had the highest leaf water potential and lowest stomatal resistance. Plants with all roots in well‐watered soil lost 2.5 times less water, but grew as well as plants with all roots in solution. Plants with roots split between solution and well‐watered soil lost the same total amount of water as plants with all roots in solution. But the plants with roots in soil:soln lost 7 and 11 times more water from the solution side than from the soil side of the split root containers for the wind and no‐wind treatments, respectively. Nonstressed plants (no wind, no drought) with roots split between soi1:soln were taller and had a larger leaf area than plants with roots all in soil or all in solution. The results showed that growth of wheat was increased if part of its root system was in media with zero matric potential (nutrient solution) and part in soil.
Growth Stages and Distribution of Dry Matter, N, P, and K in Winter Wheat1
Authors: Waldren R. P. , Flowerday A. D.
Published: July 2010

Stage of growth descriptions were developed for winter wheat (Triticum aestivum L.) which will apply to single plants or a community of plants. The growth stages are easily discernable and precise. Accumulations of dry matter, N, P, and K in leaves, culms, head, and grain were measured at each growth stage.

Observations and plant samples were taken of fieldgrown winter wheat (cultivar ‘Centurk’) over the 3‐year period of 1975‐77. Plants were grown at the Univ. of Nebraska Agronomy Farm, Lincoln, on a Sharpsburg silty clay loam (Typic argiudoll). Plants for growth stage description and chemical analysis were randomly sampled from a field population and separated into leaves, culms, head, and grain as these plant parts developed.

Growth stages are defined and illustrated. The 10 developmental stages are: O—Emergence, 1—Crown development and tillering, 2—Leaf sheath elongation, 3—Culm elongation (jointing), 4—Flag leaf emergence, 5—Peduncle elongation (heading), 6—Flowering (anthesis), 7—grain filling, 8—Stiff dough, 9—Hard dough (ripening), and 10—Maturity.

Dry matter accumulation increased rapidly from stage 3 through stage 8. Translocation of dry matter from leaves to grain began at stage 6 and from culms and head to grain at stage 7. Nitrogen uptake was most rapid from stage 2 to stage 4 with 80% of the total accumulation occurring by stage 7. Over 70% of the total N uptake was translocated to the grain at maturity. Uptake of P and K was most rapid from stage 3 to stage 7. Seventy‐five percent of P uptake was translocated to the grain at maturity but only 15% of K present in the plant was found in the grain at maturity.

The stage descriptions provide a standard for researchers, extension workers, producers, students, and agribusiness personnel to accurately define and determine the growth stages of winter wheat. The dry matter accumulation and nutrient uptake data provides part of the information necessary in making correct management decisions.
Proteins and Amino Acids in Grain of Maize Grown with Various Levels of Applied N1
Authors: Rendig V. V. , Broadbent F. E.
Published: July 2010

Cereals provide a major source of protein in food chains. Yet, particularly as compared with associated yield responses, relatively little information is available about possible effects of N supply on protein quality in cereal grains. Maize (Zea mays L.) was grown in a series of field plots which received various rata of applied N as ammonium sulfate. The site was in an area mapped as Yolo (Typic Xerorthents) fine sandy loam, and rates of N application of 0, 90, 180, and 360 kg N/ha were used on quadruplicate plots. The entire plot area had been fertilized with K, and sufficient water was applied during the season to meet evapotranspiration needs. Total N in the grain was determined by a Kjeldahl method, amino acids with an amino acid analyzer after subjecting samples to conditions which would hydrolyze protein, and protein fractions were extracted using a modified Osborne‐Mendel procedure.

Yields of grain were nearly doubled to approximately 10,700 kg grain/ha by application of N, with no significant difference between yield means for the 180 and 360 kg N/ha rates. Concentrations of crude protein (N ✕ 6.25) ranged from about 6% in grain from plots receiving no added N or 90 kg N/ha, to nearly 10% (mean of concentrations in grain from plots receiving 180 and 360 kg N/ha, which did not differ significantly). The concentrations in the grain protein of tryptophan, lysine, glycine, arginine and threonine were decreased, and the concentrations of alanine, phenylalanine, tyrosine, glutamic acid and leucine increased by applications of N. The first increment of N (90 kg/ha), which had the greatest effect on grain yield, did not have significant effects on the concentrations of tryptophan, lysine or alanine in the protein.

The differences in concentrations of the amino acids in the grain from the different N treatments were in part, but not wholly, accountable for by differences in the concentrations of the prolamine (zein) protein fraction. Thus, for example, serine, which is present in relatively high concentration in zein, should have been present at higher concentration in the grain from the N‐fertilized mainze. Valine, histidine and methionine, on the other hand, might be expected to be present at lower concentrations with this treatment.

The yields of grain crude protein were approximately 2‐fold greater with applications of 180 or 360 kg N/ha than with no applied N. Treatment effects on yields of amino acids ranged from nil in the case of tryptophan to about four‐fold greater amounts of leucine in grain from plots receiving the two highest rates of N.