bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature and Zinc Interactions on Cotton Growth1
Authors: Joham H. E. , Rowe Viola
Published: July 2010

We have been obtaining variable results with respect to the effects of high levels of substrate zinc on the growth and development of cotton (Gossypium hirsutum L.). The present investigations were made to study the possibility that the observed Zn effects were subject to modification by changes in temperature.

Cotton, ‘Deltapine 16,’ was grown in the greenhouse and supplied various levels of substrate Zn. The minimum greenhouse temperature in each experiment was controlled at 15, 19 or 23 C. A Zn‐temperature interaction was apparent in the control of flowering and fruiting. Increasing the minimum temperature from 15 to 23 C and increasing substrate Zn from 1 to 25 ppm at 15 C caused a shift in flowering from an indeterminant to a more determinant pattern and increased fruit production. Increasing temperature from 15 to 23 C eliminated the effect of substrate Zn concentration on flowering and yield. Maximum fruit production in the low, medium and warm temperature experiments were obtained with the 25, 5, and 1 ppm Zn treatments, respectively. The critical concentration of Zn in the leaves (that concentration above which toxic effects are obtained) was observed to be between 200 to 300 ug/g at the 54‐day harvest and decreased with age to a level between 100 to 200 ug/g by the 130‐day harvest.

Thus, high levels of substrate Zn, which promote tissue concentrations just below the critical levels, may have a beneficial effect on the yield of cotton grown under low temperature conditions.
Effect of Fertilizer and Fritted Trace Element (FTE 503) Levels and Placement on Snap Beans Grown on a Tiwiwid Sand1
Authors: Saxena G. K. , Locascio S. J.
Published: July 2010

Nutritional requirements of vegetables grown on noncoastal regions of Guyana have not been established. The present study was conducted on a major soil type in these areas, a Tiwiwid sand (Typic Quartzipsamments) to evaluate the effects of fertilizer rate and placement and fritted trace element (FTE 503)4 rate on nutrient uptake, root distribution, and yield of snap beans (Phaseolus vulgaris L.). Fertilizer levels were 79‐67‐112 and 158‐67‐224 kg/ha on the area fertilized and were applied on one‐third, two‐thirds, and the full bed. FTE 503 treatments 44.8 kg/ha and no application.

Snap bean yields were reduced from 1,008 kg/ha at the lower fertilizer rate to 727 kg/ha at the high rate. With the application of FTE 503 and the low fertilizer level, yields increased with an increase in the width of the fertilizer band. At the high fertilizer rate, yields were reduced with an increase in the width of the fertilizer band. Application of FTE 503 increased the average dry weight of bean plants from 0.55 to 1.07 and from 1.94 to 5.17 g/plant at the flowering and pod set stages, respectively. Yield increases due to FTE 503 applications were from 216 to 1,800 kg/ha and from 26 to 1,428 kg/ha, when fertilizer rates were 79‐67‐112 and 158‐67‐224 kg/ha, respectively. Mean root concentration in the surface 30 cm of soil were increased from 1.39 to 1.82 cm root/cc soil with an application of FTE 503. Results indicated that application of FTE 503 corrected micronutrient deficiencies and improved the availability of soil water and nutrients.
Optimum Size of Sampling Unit to Estimate Coastal Bermudagrass Yield1
Authors: Soplin H. , Gross H. D. , Rawlings J. O.
Published: July 2010

Because the field‐plot techniques used on ‘Coastal’ bermudagrass [Cynodon dactylon (L.) Pers.] have been empirically transferred from temperate species research, our objective was to define an optimum sampling‐unit size for this species. Optimum size of sampling unit was evaluated under six managements: three heights of available forage (avg. 3.75, 7.50, and 11.25 cm), each maintained by grazing or clipping. Three samplings were made on each treatment, corresponding to early, mid, and late‐summer harvest dates. The basic sampling unit was a 20‐cm square.

Plots more nearly square and those perpendicular to the slope gave larger estimates of variance than plots that were parallel to the slope and rectangular. Variance of yield/unit area arranged over plot size‐harvesting date combinations increased with height of available forage.

Three weighted coefficients of the logarithm of variance of mean yield by heights, regressed on the logarithm of plot size, were computed. Optimum size of sampling unit, regardless of treatment, was found to be not greater than 20 ✕ 20 cm for a cost function based on hand clipping. Assuming costs associated with mechanized harvest, optimum size was found to be 16, 15, or 10 units in size (respective to the three heights) with the longer dimension parallel to the slope.
Boron Source and Lime Effects on the Yield of Three Crops Grown in Peat1
Authors: Prasad M. , Byrne E.
Published: July 2010

The necessity of adding B in peat soils is recognized. A limited amount of information is available regarding toxic levels of B in these soils. A greenhouse experiment was therefore carried out to measure effects of three levels of lime × four levels of B (including control) × two types of B source on tomato (Lycopersicon esculentum Mill cv. Eurocross BB), cucumber (Curcumis sativus L. cv. Sporu), and sweet corn (Zea mays L. cv. Golden Cross Bantam) in a peat soil. The two sources of B were sodium tetraborate and B‐frit. The crops were grown for about 7 weeks.

“Lime had a significant effect on yield of tomato, cucumber and corn, while B‐rate had a significant effect on yield of tomato and cucumber only. B‐rate had a significant effect on B‐concentration of all three crops — B‐source had a significant effect on B‐concentration of sweet corn only.”

Visible toxicity symptoms were recorded with cucumber and corn at three times the normal rate of B application. The plant levels of B at which toxicity occurred were 115 and 53 ppm for cucumber and corn, respectively. Hot water soluble B up to 10 ppm failed to produce toxicity symptoms.

Significant correlations between hot‐water soluble B and B concentration in plant and B‐uptake suggested that hot‐water soluble B was an effective soil test for peat soils in spite of the fact that it can overestimate the availability of B at high lime levels. The critical values of hot‐water soluble B for deficiency and toxicity are much higher than in mineral soils.
Influence of Salinity and N‐P Fertility Levels on Mineral Content and Growth of Sorghum in Sand Culture1
Authors: Patel P. M. , Wallace A. , Wallihan E. F.
Published: July 2010

Plant growth is characteristically depressed at certain levels of salt concentrations yet it sometimes responds to fertilizers even though growth depression can be expected to reduce nutrient requirements and even though fertilizer application increases salinity to some degree. This study was designed to examine tension zones involving interactions between nutrient supply (N and P) and salt concentrations.

Grain sorghum (Sorghum bicolor (L.) Moench) was chosen for this study because it is commonly grown in regions of irrigated agriculture where soil salinity is often a problem. Plants were grown to maturity in automatically operated sand culture equipment at two levels each of N and P, each subjected to added Ca‐Na chloride salinity levels of zero, medium (EC = 10 mmho/cm) and high (EC = 20 mmho/cm).

Vegetative growth was depressed to about 50% of control at both medium and high salinity, while grain production was depressed to about 35% at medium salinity and to almost none at high salinity. Chemical composition of leaves, in addition to familiar dilution effects and ion competition, revealed increased accumulation of Ca, Na, and CI related to high level of P supply, at high salinity only. When sorghum was grown at salinity levels that permitted reasonable grain production, maintenance of optimum soil fertility was important. However, the required level of nutrient supply was lower in saline than in nonsaline soils because of reduced growth. A critical balance between optimum nutrition and increased salinity from applied fertilizers was also involved.
Relationship of Alfalfa Cultivar Yields to Specific Leaf Weight, Plant Density, and Chemical Composition1
Authors: Porter T. K. , Reynolds J. H.
Published: July 2010

The objective of this study was to determine the relationship of dry matter yield to various plant parameters in 11 alfalfa (Medicago sativa L.) cultivars that represented a wide range of winterhardiness. The parameters measured were specific leaf weight (SLW), plant density, and concentrations of protein‐N, P, K, Ca, and Mg in the forage. Suggestions and reports have been made in the literature that plant parameters such as specific leaf weight and K concentration in the forage are positively correlated with yield of alfalfa. Previous research reports have not contained correlations of all our parameters with dry matter yield from broadcast‐seeded field plots. The cultivars were broadcast‐seeded in 2.1 ✕ 7.6 in plots on a Humic Hapludult soil and harvested five times at approximately 1/10 bloom during the next year.

Dry matter yield of cultivars was positively correlated with plant density but not correlated with SLW or with concentration in the forage of any of the following elements: protein‐N, P, K, Ca, Mg. When averaged over all cultivars, the SLW generally was higher on the sampling dates preceded by higher mean air temperatures. When averaged over all harvests, the range in concentration of each element was not large. Apparently correlations previously reported between SLW of alfalfa and net photosynthetic rate on a unit leaf area basis did not extend to yield on a unit land area basis in broadcast‐seeded field plots. Individual elemental concentration of protein‐N, P, K, Ca, or Mg, when sampled at 1/10 bloom harvest, was not a good parameter for evaluating the immediate dry matter production of the alfalfa cultivars.
Influence of Seed Size, Planting Depth, and Companion Crop on Emergence and Vigor of Seedlings in Sweetclover1
Authors: Haskins F. A. , Gorz H. J.
Published: July 2010

Seed size has been shown to have an important influence on the emergence and early growth of seedlings of several forage legumes, but only fragmentary information on seed size effects in sweetclover (Melilotus spp.) has been published. Therefore, a 2‐year study was conducted in which spring and fall seedings of small, medium, and large seeds of ‘Madrid’ and ‘N13’ sweetclover (Melilotus officinalis (L.) Lam.) were made at depths of 19, 38, and 57 mm. The spring seeding also included a comparison of a companion crop (oats) with no companion crop. Data on emergence score and plant height were collected for the spring seeding only; stand count and dry matter yield of tops and roots were measured for both spring and fall seedings.

The companion crop had little effect on emergence score, but it reduced stand count and plant height, and was highly detrimental to dry matter yield. The performance of Madrid was poorer in all respects than that of N13, an experimental cultivar with relatively large seeds. As planting depth was increased, stand counts decreased, but the performance of plants that emerged from the greater depths was relatively good. The most striking results of increased seed size appeared to be improved emergence score and increased dry matter production.
Herbicides for Establishing Kentucky Bluegrass Turf from Plugs1
Authors: Solon E. G. , Turgeon A. J.
Published: July 2010

The use of herbicides for controlling weeds while establishing turf from seed has been limited by the intolerance of seedling turfgrass plants to many herbicides. However, the introduction of vegetative techniques tor establishing Kentucky bluegrass has presented new possibilites for successfully using herbicides in conjunction with turfgrass establishment. The purpose of this study was to determine whether the use of preemergence herbicides is feasible while establishing Kentucky bluegrass from plugs.

Greenhouse studies were undertaken to evaluate the effects of preemergence herbicides on the growth of single‐plant cultures of ‘A‐20’ Kentucky bluegrass (Poa pratensis L.), All herbicides inhibited some aspect of growth as determined by measurements of roots, shoots, density, and rhizomes. In the field, however, only benefin (N‐butyl‐N‐ethyl‐ a,a,a‐trifluoro‐2,6‐dinitro‐p‐toluidine) and bensulide [O‐O‐diisopropyl phosphorodithioate S‐ester with N‐(2‐mercaptoethyl)benzene sulfonamide] reduced the lateral growth of ‘A‐20’ plugs while calcium arsenate and DCPA (dimethyl tetrachloroterephthalate) did not inhibit establishment of the turf compared to untreated plots. Where annual bluegrass (Poa annua L.) was seeded in conjunction with plugging the fastest Kentucky bluegrass establishment and best weed control were in plots treated with oxadiazon [2‐tert‐butyl‐4‐(2,4‐dichloro‐5‐isopropoxyphenyl)‐ Δ2‐l,3,4‐oxadiazolin‐5‐one]. Postemergence applications of endothall [7‐oxabicyclo(2,2,l)heptane‐2,4‐dicarboxylic acid] did not control annual weeds and reduced the amount of ‘A‐20’ in some plots due to its injurious effects on the plugs.
Accuracy of Lysimetric, Energy Balance, and Stability‐corrected Aerodynamic Methods of Estimating Above‐canopy Flux of CO21
Authors: Verma S. B. , Rosenberg N. J.
Published: July 2010

Measurement of carbon dioxide exchange is necessary to indicate rates of photosynthesis in the field. Methods which are accurate over short periods of 15 min to 1 hour can indicate the influence of changing weather conditions on crop photosynthetic activity. Three micrometeorological methods—the lysimetric, energy balance, and stability‐corrected aerodynamic—can be used for field determination of the flux of CO2 to a crop surface. The objective of this paper is to present a detailed comparison of the performances of the three methods. Measurements were made in an oat field at Mead, Neb. Results obtained with the three methods were in good agreement, both on a short‐period and on a daily basis. The calculated CO2 flux agreed reasonably well with estimates from other oat‐photosynthesis studies. Midday CO2 flux rates ranged from about 2 to 3 ✕ 10−7 g cm−2 sec−1. The three micrometerological methods were subjected to detailed error analysis to evaluate the relative influence of errors in measurement of the constituent input parameters used to calculate the flux of carbon dioxide, namely water vapor flux and gradients of vapor pressure and CO2 concentration in the lysimetric method; net radiation, soil heat flux and gradients of vapor pressure, air temperature and CO2 concentration in the energy balance method; and gradients of windspeed, air temperature and CO2 concentration in the stability‐corrected aerodynamic method.
Potential Distributions in the Soil‐Root System1
Authors: Molz Fred J.
Published: July 2010

A more complete theoretical understanding of water transport in the soil‐root system depends upon considering the combined effects of the root tissue and soil on water flow. Therefore, equations were developed to describe the steady flow of water in a cylindrical soil‐root system. The main objective was to calculate water potential distributions in the root cortex as well as in the surrounding soil. Results indicate that there will be small water potential gradients in the soil relative to those in the root, with the possible exception of very dry soil conditions. An important implication of the present study is that models designed to predict the pattern in which roots extract water from soil will have to consider the rate‐limiting aspect of the root tissue.
Zinc Accumulation and Growth of Corn Seedlings as Affected by Endosperm Removal1
Authors: Edwards J. H. , Kamprath E. J.
Published: July 2010

Previous work indicated that under low light intensity, seed Zn was the main source for young corn (Zea mays L.) seedlings and that uptake of Zn from an external source was minimal. Experiments were conducted under controlled conditions to determine the effects of endosperm removal on uptake and accumulation of Zn by corn seedlings under varying conditions of light intensity, P levels, and external Zn levels.

Corn seedlings were grown three days at light intensities of 30,000 and 14,000 lux. The endosperm was removed from one group of seedlings and left intact on another group of seedlings. Three days later the seedlings were placed in Zn solutions of 0, 0.2, and 1.0 μM ZnSO and either 0 or 0.1 mM P. The uptake of Zn was investigated over a 144 hour uptake period. Endosperm removal did not affect Zn accumulation at the high light intensity. At the low light intensity, Zn accumulation was reduced by endosperm removal at 0.2 μM Zn, but accumulation was similar in both endosperm treatments at 1.0 μM Zn. Root growth was reduced more severely than top growth by endosperm removal at both light intensities as indicated by increasing shoot‐to‐root ratio. This effect was still apparent 216 hours after endosperm removal.

Phosphorus treatments did not adversely affect Zn uptake or translocation. The maximum enhancement in Zn uptake was observed when P occurred as an external ion at low Zn concentration and minus endosperm treatment. At low light intensity Zn uptake rate was drastically reduced when P was not present as an external ion.
Soybean Root Anatomy as Influenced by Soil Bulk Density1
Authors: Baligar V. C. , Nash V. E. , Hare M. L. , Price J. A.
Published: July 2010

This research was conducted under controlled greenhouse conditions to investigate the effects of soil compaction on soybean (Glycine max L.) root antomy. Previous research has shown that high soil compaction reduces root efficiency in moving air, water, and nutrients into the plant.

Increasing bulk density from 1.65 to 1.95 g/cm3 altered the root anatomy. In the high density soil layers a larger percentage of the root volume was occupied by cell wall material, and the transverse sections of the roots had a wavy outline with ruptured epidermal cells. The vascular cylinder became more oval with a gradual increase in both casparian thickening in the endodermis and wall thickening in the xylem vessels.
Sprinkler Application of P and Zn Fertilizers1
Authors: Hergert G. W. , Reuss J. O.
Published: July 2010

The rapid development of sprinkler irrigation in the Great Plains has stimulated interest in applying fertilizers in sprinkler irrigation water. Sprinkler application and conventional preplant application effects of P and Zn fertilizers on the dry matter yield, nutrient content, and grain yield of corn (Zea mays L.) were compared in 1968 and 1969. Both years preplant P treatments produced a significantly higher dry matter yield during the first 5 weeks of the growing season. No significant difference existed between P treatments after this time. In 1969 plants which received preplant P and Zn contained slightly higher concentrations of P and Zn than the plants which received sprinkler P and Zn. Grain yields were significantly increased by Zn application in 1968 but not in 1969. In 1968 on a Nunn clay loam soil (Aridic Argiustoll) the sprinkler‐applied P did not move below a 4–5 cm depth. On a Haxtun loamy sand (Pachic Argiustoll) in 1969 sprinkler‐applied P moved to a depth of approximately 18 cm. Sprinkler‐applied Zn moved to a maximum depth of 5 cm on both soils.
Soil Physical Conditions Affecting Rice Root Growth: Bulk Density and Submerged Soil Temperature Regime Effects1
Authors: Kar S. , Varade S. B. , Subramanyam T. K. , Ghildyal B. P.
Published: July 2010

Information is lacking on the performance of the rice plant due to variations in temperature regimes in association with other soil physical properties. This investigation, carried out under controlled greenhouse conditions, evaluated the influence of temperature and mechanical impedance of soil, as well as of their interaction, on root and shoot growth of rice (Oryza sativa L. ‘Taichung Native 1’).

Four submerged soil temperature regimes (27 to 15 C, 32 to 20 C, 37 to 25 C and 42 to 30 C) thermoregulated in water baths, indicated that the maximum root and shoot growth of rice occurred at 37 to 25 C. Irrespective of the bulk density of soil, the total number of roots at the base and the dry weight and volume of the rice root system significantly increased as the submerged soil temperature regime increased from 27 to 15 C to 37 to 25 C, but decreased at 42 to 30 C.

Multiple regression analysis indicated that the number of degenerated roots increased with the increase in submerged soil temperature regime, but decreased with the increase in bulk density of the lateritic sandy loam soil. The multiple correlation coefficient between these three variables was significant at 1% level (R=0.79).

With increase in bulk density from low to medium, the dry weight of shoot and root, and the number of roots at the base significantly increased at 27 to 15 C and 42 to 30 C, but decreased at 37 to 25 C in all the three soil textures studied. However, when the bulk density was increased from medium to high levels, the shoot and root growth parameter decreased under all temperature regimes.
Irrigation Schedules for Sugarbeets on Medium and Coarse Textured Soils in the Northern Great Plains1
Authors: Cassel D. K. , Bauer Armand
Published: July 2010

An increase in the access to irrigation water in the Northern Great Plains is effecting large increases in the acreages of soils being irrigated. Much of this water is being applied to medium to coarse‐textured soils which hold a maximum of 7 to 12 cm of available water in a 152 cm deep profile. An investigation was conducted in the field to devise a system, using tensiometers, to schedule the application of irrigation water to sugarbeets growing on these soils. Tensiometers were installed at various soil depths, and irrigation water was applied with a small plot irrigator when soil moisture tension reached a predetermined level.

One tensiometer located at the 45 cm depth was equally effective in scheduling as two tensiometers, one positioned at a depth of 30 and one at 61 cm. Maximum crude sugar yields of 8.4 to 8.8 metric tons/ha were obtained in 1971 and 1973, respectively. Total water use efficiency was 0.15 to 0.16 metric tons of crude sugar/ha per cm. The maximum irrigation water use efficiencies were 0.32 and 0.36 for 1971 and 1973, respectively. It is concluded that 56 to 62 cm of water, well distributed throughout the growing season, is sufficient for sugarbeet production is southeastern North Dakota in a year of normal growing season temperatures.
Diffusion and Mass Flow of Nitrate‐Nitrogen to Plant Roots1
Authors: Phillips R. E. , NaNagara T. , Zartman R. E. , Leggett J. E.
Published: July 2010

The transport of plant nutrient ions from the soil mass to plant root surfaces is an important phenomenon in mineral nutrition of plants. Nitrate‐nitrogen, the most important source of nitrogen of non‐leguminous plants, is soluble in soil water and is transported to plant roots by both mass flow and diffusion. It is, therefore, important to understand the relative importance of each of these two mechanisms of transport of NO3‐N to plant roots and the environmental conditions under which each is the dominant mechanism of transport.

In order to predict from theory the simultaneous transport of NO3‐N to plant root, several soil and plant parameters must be known. These parameters include the volumetric soil water content, concentration of NO3‐N in soil solution, porous diffusion coefficient of NO3‐N in soil, average macroscopic velocity of soil water at plant root surface, radius of root, transpiration rate and plant root length. These soil and plant parameters must be measured in either the field or greenhouse.

The validity and/or consequences of several assumptions of a previously reported steady‐state model describing simultaneous mass flow and diffusion of NO3‐N to plant root surfaces are discussed with reference to experimental measurement of plant and soil parameters. The relative importance of diffusion to mass flow of NO3‐N is large when the ratio of transpiration rate to the constant of proportionality relating flux into the plant to concentration of NO3‐N in the soil solution is less than 0.2 but is negligible when the ratio is greater than unity. The average concentration of NO3‐N of the entire soil mass rather than the concentration of NO3‐N at the outer radius of the soil cylinder associated with each root can be used in the model with little error for most situations expected to occur in the field.
Molybdenum Concentration of Certain Crop Species as Influenced by Previous Applications of Molybdenum Fertilizer1
Authors: Hawes R. L. , Sims J. L. , Wells K. L.
Published: July 2010

Excessive Mo concentrations in forage crops have been reported to cause toxicity in livestock. Since forage crops often are grown following crops fertilized with Mo, a study was conducted to determine the effect of previous applications of Mo on Mo concentration and yield of dry matter of certain crop species. Five different crops were grown on Maury (Typic Paleudult; clayey, mixed, mesic) soil (pH 6.4) fertilized the previous year with levels of Mo (0, 0.22, 0.44, 0.88, 1.32, and 2.64 kg Mo/ha). The above‐ground plant parts were sampled at one or more dates, weighed, dried, and ground for Mo analysis.

Generally, concentration of Mo increased as the level of Mo applied previously increased in all crops sampled and at most sampling dates. For crops sampled at two maturity dates, Mo concentrations were higher in plants sampled at the earlier date than when plants were mature. The lower values at mature harvest may be attributed to dilution by dry matter. Although concentrations increased with level of Mo applied, the highest concentration found (3.89 μg Mo/g dry weight) was judged unlikely to cause toxicity in livestock. Mo fertilization at recommended rates of soils with low‐to‐average Mo levels should not subsequently result in forage with Mo concentrations that are toxic to livestock. Mo fertilization had little effect on dry matter yields.
Rates of Photosynthesis and Transpiration and Diffusive Resistance of Six Grasses Grown Under Controlled Conditions1
Authors: Frank A. B. , Barker R. E.
Published: July 2010

Photosynthesis (Pn) and transpiration (E), and the components of diffusion resistance to CO2 and water vapor transport were measured in western wheatgrass (Agropyron smithii Rydb.), crested wheatgrass (A. desertorum [Fisch.] Schult.), pubescent wheatgrass (A. intermedium var. trichophorum [Link] Haloc.), Russian wildrye (Elymus junceus Fisch.), orchardgrass (Dactylis glomerata L.), and reed canarygrass (Phalaris arundinacea L.) to determine the rates of these processes and the role of stomates in controlling Pn and E. Plants were grown in a glasshouse and Pn and E measured at tillering and heading growth stages at three ambient CO2 concentrations and four light levels.

At 1,160 μEm−2s‐−1 and 300 μl/liter CO2, Pn at tillering ranged from 10.2 to 26.2 mg CO2 dm−2hour−1 for reed canarygrass and western wheatgrass, respectively. E was lowest in reed canarygrass (1.1 g H2O dm−2hour−1) and highest in western wheatgrass (3.6 g H2O dm−2hour−1). Pn increased and E decreased for all species as ambient CO2 increased from 100 to 500 μl/liter CO2. Somate sensitivity to CO2 concentration and light level was evident in pubescent wheatgrass and orchardgrass but other species exhibited only slight changes. Minimum stomatal diffusion resistance to water vapor transport (rs) varied considerably among species. Partitioning of the components of resistance to CO2 and water vapor transport indicated that, at 1,160 μEm−2s−1 and 300 μ1/1 CO2, Pn of pubescent wheatgrass was primarily limited by stomatal apertures controlling diffusion of CO2 into the leaf (r's), whereas Pn of western and crested wheatgrasses, Russian wildrye, reed canarygrass, and possibly orchardgrass was limited more by the chemical process and/or internal resistances to CO2 diffusion in the liquid phase than by stomatal resistance. Ratios of E/Pn and rs/(r's+rm) (rm is mesophyll resistance), indicate that water use efficiency was highest in pubescent wheatgrass and lowest in western wheatgrass.
Budding Phenology of Guar in the Rolling Plains of Texas1
Authors: Rogers C. E. , Stafford R. E.
Published: July 2010

Development of a sound pest management program for the midge, Contarinia texana (Felt), requires a knowledge of the budding phenology of guar, Cyamopsis tetragonoloba (L.) Taub. Thus a 3‐year study was designed to determine the budding pattern for guar in the Rolling Plains of Texas. Guar was sampled and the number of floral buds counted weekly from the onset of budding until the plants reached maturity or were terminated by a freezing temperature.

Bud production in guar under dryland cultivation was greatest in plants that emerged in mid‐June. With adequate soil moisture, three‐quarters of the total bud load in dryland guar was produced during the middle one‐third of the production period. Maximum bud production in dryland guar occurred during the 8th, 8th, 11th, and 16th week, respectively, for guar emerging on 25 May 1973, 12 July 1973, 12 July 1972, 15 June 1972 and 19 July 1974. Plants emerging on these dates produced 100, 50, 90 and 60% of the total bud load, respectively, by mid‐September.

Bud production in irrigated guar was greatest in plants that emerged in mid‐to‐late May. Irrigated guar emerging on 22 May, 18 June, and 18 July, 1973, experienced maximum bud production during the eleventh, eighth, and sixth week postemergence, respectively. Plants emerging on these dates produced 90, 70, and 57% of the total buds, respectively, by mid‐September.

This study indicates that for maximum returns for chemical control of the “guar midge,” treatment should be restricted to the middle one‐third of the budding season.
Alfalfa Weevil Effects on Root Reserves, Development Rate, and Canopy Structure of Alfalfa1
Authors: Fick Gary W. , Liu Beverly W. Y.
Published: July 2010

Defoliation by the alfalfa weevil (Hypera postica Gyllenhal) results in a direct reduction in yield of alfalfa (Medicago sativa L.). Indirect responses to insect feeding may partially compensate for direct losses or cause further reductions in yield and feed quality. The purpose of this study was to identify indirect responses of alfalfa to weevil defoliation. We studied the effects of the alfalfa weevil on (i) root reserves, as measured by total nonstructural carbohydrates (TNC) in the taproot, (ii) morphological rate of development, and (iii) canopy structure.

Alfalfa weevil defoliation produced statistically significant effects on all three factors. When the peak of the undisturbed larval population was about three/stem, TNC levels were reduced by up to 0.14 metric ton/ha while defoliation occurred. After the larval population declined, there was recovery growth and TNC yields reached levels up to 0.09 metric ton/ha higher than where weevils were controlled. The crossover from lower to higher TNC levels was associated with delayed morphological development and a prolonged TNC accumulation period where damage occurred. When alfalfa was cut before the larval population reached a peak, TNC levels were reduced during the regrowth period. Larval populations higher than two/stem reduced canopy height and leaf percentages during defoliation. During the post‐defoliation recovery period, moderately damaged plants increased in leaf percentage and produced more branches than lightly defoliated plants. However, the moderately defoliated plants remained shorter and there were resulting large differences in canopy structure. These findings showed a wide range of indirect effects of insect defoliation on alfalfa growth, and they should be considered in evaluating insect damage to the crop.
Growth Rate and Nutrient Uptake of Two Cotton Cultivars Grown Under Irrigation1
Authors: Halevy J.
Published: July 2010

The production of high cotton yield is highly dependent on adequate growth rate and nutrient uptake about which relatively little information is available under semiarid conditions.

Growth rate and N, P, K uptake of two cotton (Gossypium hirsutum L.) cultivars, ‘Acala 1517‐C’ and ‘Acala 4‐42,’ which differ in their response to K fertilizer, were investigated in an irrigated field (soil type ‐ Typic Rhodoxeralf) under favorable conditions conducive to high yields.

The rate of dry matter production was slow until flowering and after the first bolls opened. Up to 72 days from emergence, 15% of the total dry matter was produced; from 112 days until picking, 10%; and during the 40‐day period from 72 to 112 days, 75%. Throughout this period the growth rate was nearly linear, 250 kg/ ha/day.

Total dry matter was 12,200 to 13,480 kg/ha. Its distribution in mature plants was 26% in the leaves, 24% in stems, 16% in burs, 21% in seeds, and 13% in lint. The lint yield was 1,700 kg/ha. Total uptake of N, P, and K was 230, 45, and 174 kg/ha.

The total uptake of N and P followed that of dry matter production, whereas K was absorbed more rapidly, reaching a maximum at 112 days from emergence and then decreasing. The removal of nutrients from the field by seed and lint was 98 to 109 kg N/ha, 19 to 21 kg P/ha, and 43 to 47 kg K/ha.

Toward the end of growing season Acala 1517‐C suffered more than Acala 4‐42 from K deficiency in soils with a low supply of available K. The factors which may be responsible for this in Acala 1517‐C are earlier development, greater uptake of K during early growth, the larger uptake of K by relatively more developed reproductive parts, and the relatively smaller root system.

The rates of growth and uptake in the present experiment were greater than those reported in the literature. Also, Acala 1517‐C and Acala 4‐42 differed in their nutrient uptake, especially of potassium.
Stomatal Response to Leaf Water Potential as Affected by Preconditioning Water Stress in the Field1
Authors: Thomas J. C. , Brown K. W. , Jordan W. R.
Published: July 2010

Previous research has shown that stomatal response to decreasing soil water potential of chamber‐grown sorghum (Sorghum bicolor L. Moench. ‘Oro’) and cotton (Gossypium hirsutum L. ‘Stoneville 213’) is altered by exposure to previous water stress. This work was undertaken to determine if stomatal response of field‐grown plants is also altered by previous water stress.

Stoneville 213 cotton was grown in the field under movable rainshelters and was subjected to three treatments: control — well watered, one period of water stress, and two periods of water stress. After this preconditioning period, all plants underwent a final stress during which stomatal response to leaf water potential was measured.

The periods of preconditioning water stress were characterized by decreased cumulative growth as measured by leaf area per plant. Leaf areas for the control, one soil water stress plants, and two soil water stress plants were 5,200, 2,200, and 1,200 cm2, respectively. Lower stomates of preconditoned field‐grown plants remained open to lower leaf water potentials (—28 to —30 bars) during the final stress than those of plants which were not preconditioned (—22 bars). These results were similar to those found previously on chamber‐grown plants which had been exposed to more frequent but shorter stresses. The 6 to 8 bar adjustment in leaf water potential vs. stomatal resistance as a result of previous water stress indicates a need for caution in interpreting data from plants of unknown water stress history.
Effect of Soil Moisture Tension and Amendments on Yields and on Herbage N, P, and S Concentrations of Alfalfa1
Authors: Nuttall W. F.
Published: July 2010

Low protein concentration has been observed in alfalfa herbage grown on Gray Wooded Luvisol soils, particularly in cool, wet years. Nutrient deficiencies of N, P, and S also occur on these soils. The objectives of this experiment were to determine how soil moisture and soil type interact with amendments to increase yield and change N, P, and S concentrations in alfalfa (Medicago media Pers.) herbage grown in the greenhouse.

Three Gray Wooded Luvisols, Typic Cryoboralf (Arborfield clay, Garrick clay loam, Mollic Cryoboralf, and Waitville loam) and one Dark Gray Luvisol soil (Nipawin sandy clay loam) × two soil moisture tensions (100 and 151 millibars) were main treatments. Amendments of cattle manure, sedge peat, and wheat straw were applied on subplots at 2.5y0 of soil weight. Additional subplots of a control and nitrate (70 μg N/g soil before each crop) were added. Two crops of barley (Hordeum vulgare L.) and one of rape (Brassica napus L.) were grown before ‘Rambler’ alfalfa.

Yield of alfalfa was significantly related to moisture use (r2 = 77% in cut 1; r2 = 78% in cut 2). Moisture use by alfalfa was higher with cattle manure incorporated in the heavier textured Garrick clay loam and Arborfield clay soils than for other amendments or soil types. The manure treatment applied to Garrick clay loam and Arborfield clay soils under low soil moisture tension (LSMT = 100 millibars) produced the highest herbage yields.

In the first‐cut only, N concentration of alfalfa herbage was higher under high soil moisture tension (HSMT = 151 millibars) than LSMT (5.0 vs. 4.8% N) and was higher for ammonium nitrate than for manure or peat amended soils. Concentration of P in alfalfa herbage was significantly higher under LSMT than HSMT. Concentration of S in herbage was significantly lower under LSMT than under HSMT only for cut 1.

In general, LSMT interacting with soil type and amendments markedly increased alfalfa yields, reduced N and S, and increased P concentration in herbage as compared with HSMT.
Critical Ca Levels and Ca/Mg Ratios in Trifolium subterraneum L. Grown on Serpentine Soil1
Authors: Jones M. B. , Vaughn C. E. , Harris R. S.
Published: July 2010

Serpentine soils are known to have a low Ca/Mg ratio and to respond to applied Ca in many instances. To assist in assaying the Ca status of these soils we determined the effect of growth stage, plant part, and defoliation treatment on the critical Ca concentrations and Ca/Mg ratios in subclover growing in potted serpentine soil of the Henneke series, a lithic Argixeroll.

One of six rates (0, 200, 400, 800, 1,600, and 3,200 ppm) of Ca as CaSO4 and uniform rates of P, K, S, and Mo were applied to each pot and the soil was mixed uniformly and planted to ‘Geraldton’ subclover (Trifolium subterraneum L.). On one set, leaves were removed 61, 85, and 114 days after planting. On a second set, leaves were removed on days 85 and 114, and the third set grew without clipping until day 114.

Critical Ca percentages in the three youngest leaves ranged from 0.55 to 0.69%, with no consistent trend due to growth stage or number of times the plant had been defoliated. In old leaves, critical Ca levels ranged from 0.81 to 1.47% and were higher for 114‐day‐old plants than for 85‐day‐old plants. The more often the plant was defoliated the lower the critical Ca level in old leaves. There was no significant difference between young and old stem tissue in critical Ca levels: 0.30 to 0.38% Ca. Defoliation did not induce a consistent change.

Critical Ca/Mg ratios in young leaves increased from 0.42 to 0.60 between plant ages of 61 and 85 days, whereas no significant change occurred from day 85 to 114. With plants defoliated for the third time at day 114 the critical Ca/Mg ratio was 0.36, although at the first and second clippings their critical ratios were 0.60. Calcium/Mg ratios were similar in young and old leaves. In young stems the critical Ca/Mg ratios on day 114 for the first, second, and third clippings were respectively 0.48, 0.39, and 0.21. The same values for old stem tissue were 0.38, 0.27, and 0.18.

It was concluded that percent Ca and Ca/Mg ratios in new and old stems were insensitive as measures of Ca status since these values changed less in stem than in leaves over a wide range of Ca levels. Percent Ca in young leaves was the best measure of Ca status because critical values varied less due to stage of growth or clipping treatment than did percent Ca in old leaves or Ca/Mg ratios in young or old leaves.
Response of 21 Oat Cultivars to Nitrogen Fertilization1
Authors: Ohm H. W.
Published: July 2010

The importance of percent protein in oats (Avena sativa L.) as a food and feed grain has resulted in the recent development of cultivars with an inherently high percent of groat protein. The need to determine the effects of N fertilization as an additional means of increasing the percent protein prompted experiments to determine responses to fertilizer N of 21 oat cultivars differing widely in percent groat protein and several agronomic traits. Two N treatments: one, no added N (40 to 50 kg available N/ha in the soil); and two, 110 kg N/ha in a split application were assigned at random to main plots. The 21 cultivars (19 of A. sativa and 2 of A. sativa × Avena sterilis L.) were assigned at random to subplots.

Application of N resulted in significant increases in plant height, lodging score, percent protein, and yield; it did not affect heading date or seed weight; and it reduced test weight. Short‐strawed types increased in plant height more with N application than several taller cultivars although plant height increases were greatest for other tall types. Lodging scores of weaker strawed cultivars did not always increase more with N application than those of stronger strawed cultivars. Percent protein in certain low protein cultivars increased more than that of some high protein cultivars with fertilizer N. A given cultivar may not respond similarly to N for percent protein and/or yield.

More extensive testing of potential new cultivars to determine specific fertility × cultivar interactions is recommended.
Differential Tolerances of Triticale, Wheat, Rye, and Barley to Aluminum in Nutrient Solution1
Authors: Mugwira L. M. , Elgawhary S. M. , Patel K. I.
Published: July 2010

Aluminum toxicity to cereals is an important consideration when adapting a new crop to the acid soils of the Southeast. The objective of this study was to evaluate the relative tolerances of different cultivars of triticale (X Triticosecale) a new crop, wheat (Triticum aestivum L.), rye (Secale cereale L.), and barley (Hordeum vulgare L.) to Al in nutrient solution with a pH of 4.8 at the time of transplanting. Plant induced pH change in the nutrient solution and dry matter produced were used as criteria for evaluating Al tolerance. Triticale resembled the other three species in increasing the pH of the solution during growth when no Al was added to the nutrient solution. When 6 ppm Al was added, triticale ‘6TA 131’ and ‘6TA 298,’ Al‐tolerant ‘Thorne’ and ‘Seneca’ wheats, and ‘Vitagraze’ rye increased the nutrient solution pH to values higher than 5.0. However, triticales ‘6TA 385,’ ‘6TA 203,’ and 6TA 522,’ the different barley cultivars, and ‘Abruzzi’ rye either decreased or had no effect on solution pH. ‘Atlas 66’ wheat induced significantly higher pH at 6 ppm Al added to the medium than all the other cultivars tested.

The addition of 6 ppm Al to the nutrient solution reduced the shoot growth of the different cultivars generally in a similar manner. However, reductions in root dry matter by Al indicated that, on the average, Al tolerances were: Al‐tolerant wheat and rye > triticale and Al‐tolerant barley > Al‐sensitive barley and Al‐sensitive wheat. The pH changes induced by the plants in the solution with 6 ppm Al generally confirmed the same order of tolerance as obtained from reductions in root dry matter. Increasing Al in solution significantly increased Al but decreased Ca and P in triticale, wheat, and rye. Aluminum‐sensitive wheat contained higher Al in roots than Al‐tolerant wheat. The roots of triticale and rye cultivars significantly differed in Al concentration.
Leaf Conductance Response to Humidity and Water Transport in Plants1
Authors: Hall Anthony E. , Hoffman Glenn J.
Published: July 2010

Stomatal response to humidity is a potentially important adaptive characteristic. The possibility that stomata may respond to humidity independently of changes in bulk leaf water status was tested. Also the basis for reported differences in leaf water potential response to transpiration was investigated.

Simultaneous measurements of in situ leaf water potential, transpiration, and net photosynthesis were made in controlled environments using sunflower (Helianthus annuus L.) and pinto bean (Phaseolus vulgaris L.). Responses of leaf conductance and leaf water potential to changes in ambient humidity and root medium water potential were determined.

Leaf conductance responded consistently to changes in the vapor pressure difference between leaf and air. Decreases in ambient humidity resulted in decreases in leaf conductance with constant, decreasing or increasing leaf water potentials. Leaf conductance responded to changes in leaf water potential only when manipulations of plant water supply resulted in rapid decreases in leaf water potential below a threshold level of —8 bars. These data demonstrate that stomata may respond to humidity independently of changes in leaf water potential.

On occasions environmental perturbations resulted in changes in leaf water potential that were negatively correlated with changes in transpiration. On other occasions leaf water potential remained constant when transpiration rate or water potential of the root medium was changed. On one occasion an inverted water potential gradient between root medium and leaves was observed in a transpiring plant. Models of the simultaneous movement of water and solutes within plant roots provided qualitative explanations for these observations by predicting that changes in the uptake and translocation of solutes may influence leaf water potential response to transpiration.
Photosynthate Distribution in Natural Stands of Salt Water Cordgrass1
Authors: Hull R. J. , Sullivan D. M. , Lytle R. W.
Published: July 2010

Spartina alterniflora Loisel. is a major grass species of Atlantic coast tidal marshes which contributes heavily to the primary productivity of estuarine ecosystems. As human activity increases in marsh areas, the capability of marsh vegetation to withstand disturbance must be understood and constitute the basis for formulating sound management programs. Toward this end, the seasonal distribution of photoassimilated carbon was studied in S. alterniflora growing under natural conditions. Single culms were exposed to 14CO2 at various times during the 1970 and 1971 growing seasons. Plants were harvested 1, 3, and 7 days following exposure to 14CO2. subdivided into leaves, culm, rhizomes, and roots; and each portion assayed for 14C. Assimilate translocation reached a more or less stable distribution pattern within 24 hours. Throughout much of the growing season, most photosynthate was retained in leaf and culm tissue with less than 10% translocated to roots and rhizomes. Only during early autumn was substantial photosynthate translocated into rhizomes. This and seasonal carbohydrate levels within perennial organs indicate that the stability of S. alterniflora stands may be adversely affected by summer disturbance especially defoliation.
Influence of Various Row Widths on Yields and Agronomic Characteristics of Proso Millet1
Authors: Nelson L. A.
Published: July 2010

Several varieties of proso millet (Panicum miliaceum L.) were tested in five environments at 18‐, 36‐, 53‐, and 71‐cm row spacings on typic argustoll soils. The objectives of the tests were to determine the influence of row spacing on several agronomic traits of proso and to detect any row spacing by variety interaction influence on these traits which would indicate the importance of testing varieties at the same row spacing as the producers use.

Yields were highest with 18‐cm spacings and lowest with 71‐cm spacings. Each additional 18 cm in row width reduced yield 220 kg/ha. Only one environment caused a significant yield change due to variety by row spacing interaction. Plants responded to wider row spacing by increasing in height and decreasing slightly in the time to heading.

Higher plant populations within a row at a wide row spacing reduced the proportion of planted seed which survived. Results of these tests indicate that variety testing should be conducted at a row spacing similar to that used for production of proso and that a producer should consider buying a drill with a narrow row spacing for the production of proso.