bluuebunny/crossref_metadata_2025 huggingface dataset:
Water Relations of Wheat Leaves in the Field1
Authors: Millar B. D. , Denmead O. T.
Published: July 2010

Stomatal closure at low leaf turgor and water potentials has been demonstrated in a number of crop plants but as far as we are aware, the magnitudes of these critical potentials have not been established for temperate cereals; nor have their variation from one leaf to the next been studied. We have examined the relationships between turgor potential (P), water potential (Ψ), osmotic potential (π), and stomatal closure in leaves at different positions on the stem of mature wheat plants (Triticum aestivum L. ‘Heron’) in the field.

Thermocouple psychrometry was used to determine P, Ψ, π, and the resistances of leaves to mass‐flow were used as an indication of stomatal aperture.

Stomatal closure was induced at about the same P, 8 bars, in leaves at all positions on the stem, but because of a different relationship between and Ψ for each leaf, the corresponding critical water potentials varied from —7 bars for leaves at the bottom of the stem, to —14 bars for the next highest leaves, to —19 bars for top leaves. The different relationships between P and Ψ resulted from a systematic decrease in π with leaf position from bottom to top of the stem.

There appear to be important differences in leaf water relations between this wheat variety and some other crops. For instance, the critical P of 8 bars is higher than has been reported for maize, sorghum, and tobacco, but π is generally lower. The agronomic significance of these species differences is discussed.
Sulfur Response of Maize in Western Nigeria1
Authors: Kang B. T. , Osiname O. A.
Published: July 2010

Studies of S deficiency, a problem in certain crops in Africa, have yielded inconclusive and incomplete information. There is little information on the S status of soil in the forest‐savanna zone.

Field trials were carried out with maize (Zea mays L.) at six locations in the forest and savanna zones of western Nigeria. Sulfur was applied at 0, 7.5, 15.0, 30.0, and 60.0 kg S/ha. Significant yield increases were observed with rates of S application from 7.5 to 30 kg S/ha. The response was more distinctly evident in the savanna than in the forest zone. Silking percentage was enhanced and grain quality improved with S application. No significant residual effect of the applied S was observed in the savanna zone, which was probably due to heavy leaching of the applied S. On these soils S response was observed where the amount of extractable S, extracted with either KH2PO4, Ca(H2PO4)2, or NH4C2H3O2 was below 4 ppm S. There was no response to S when extractable S levels were equal to or greater than 8.5, 10.0, and 12.0 ppm when soils were extracted with Ca(H2PO4)2, NH4C2H3O, and KH2PO4, respectively. The critical S level in the ear leaf was estimated at about 0.14% S. Although there was a strong correlation between % N and % S in the ear leaf, the N:S ratio was not related to critical S levels in plants.
Non‐Uniform Infiltration Under Potato Canopies Caused by Interception, Stemflow, and Hilling1
Authors: Saffigna P. G. , Tanner C. B. , Keeney D. R.
Published: July 2010

It is generally assumed that infiltration of sprinkler irrigation and rainfall under potato is uniform. However we observed non‐uniform infiltration beneath the hills of sprinkler‐irrigated potatoes (Solanum tuberosum L, var. Russet Burbank) grown on Plainfield loamy sand (Typic Udipsamment; sandy, mixed, mesic). The objective of this field study was to determine the effects of foliage interception and hilling on non‐uniform infiltration, since concentrating water in local zones would increase deep drainage and nitrogen leaching. To do this we traced the rainfall and irrigation infiltration pattern with Rhodamine WT dye and collected the stemflow in stem collars. Throughfall of rainfall, the soil water content, and soil water tension also were measured.

From 20 to 46% of the irrigation and from 4 to 23% of the rainfall on the canopy flowed down the stems. Stemflow increased the soil water content around the stems and moved Rhodamine dye deep beneath the soil surface. Deep movement of dye beneath the furrows was caused by runoff from the hills and by leaf drip from the outer foliage.

The results obtained suggest that irrigation and fertilizer management could be improved by taking this non‐uniform infiltration pattern into account. Smaller irrigations should improve water use efficiency and minimize nitrate leaching. Further, evaluation of solute movement by soil sampling should consider the spatial variation introduced by the non‐uniform infiltration. Finally, predictive leaching models should account for non‐uniform infiltration.
Comparison of Modified Montmorillonite to Salts and Chelates as Carrier for Micronutrients for Plants: II. Supply of Iron1
Authors: Navrot Jerzy , Banin Amos
Published: July 2010

Symptoms of iron deficiency appear very frequently in the calcareous soils which represent a major part of the agricultural soils of Israel; therefore a search for novel carriers of iron is constantly conducted. Previous studies showed that Cu, Zn, and Mn, attached to modified montmorillonite, can effectively replace salts and chelates as carriers for micronutrient elements for plants.

In this research, the effect of iron attached to montmorillonite clay on element uptake and yield of plants was compared to that of commonly used iron sulphate or EDTA and EDDHA chelates. In the greenhouse, beans (Phaseolus vulgaris L.) were grown in two calcareous, (Rendzina), iron deficient soils and were treated with either FeSO4, Fe+3‐EDTA, Fe+3‐EDDHA, or Fe+2 bound to montmorillonite clay. The rates of iron added varied from 15 to 60 mg Fe/kg soil for the salt and 3 to 12 mg Fe/kg soil for the chelates and the clay forms. It was found that Fe+3‐clay and Fe+3 in chelates, added at equivalent rates, supplied iron in comparable amounts; FeSO4, added at the conventional rates which are five to ten times higher than that added as clay‐ and chelate‐bound iron, caused similar or lower uptake and yields. Moreover, the slow release of iron from Fe‐clay, even when supplied in high rates, prevented excessive iron uptake which otherwise, as in the case of the chelate FeEDDHA, interfered with plant development. It is suggested that iron attached to mortmorillonite clay can be used as an efficient source of iron for plants grown in calcareous soils.
Relationships among Agronomic Characteristics of Corn and Sorghum Cultivars and Silage Quality1
Authors: Schmid A. R. , Goodrich R. D. , Jordan R. M. , Marten G. C. , Meiske J. C.
Published: July 2010

If agronomic characteristics could be used as criteria for judging quality of corn and sorghum cultivars for silage, the selection of genotypes best suited for silage would be facilitated. The objective of this study was to determine if agronomic characteristics of corn (Zea mays L.) and sorghum [Sorghum bicolor (L.) Moench, S. sudanense (Piper) Stapf, and their hybrid] cultivars are related to their silage quality. Over a period of 3 years, 49 silages, involving 11 corn cultivars and 14 sorghum cultivars, were produced and fed to sheep in conventional feeding trials. Eleven of the 14 sorghum cultivars were the sweet‐stem silage type. We measured fodder yield, height, %dry matter, and % plant parts [stems, ears or heads (EH), and leaves]. The quality measurements were acid detergent fiber (ADF); in vivo measurements, with sheep, of digestible dry matter (DDM); average daily gain (ADG); and dry matter intake/animal/day (DMI).

The highest correlations were obtained between % stems or % EH and quality for both corn and sorghum silages. Percent leaves and plant height were in some cases highly correlated with quality measurements, but these relationships could be explained by high correlations of % leaves and plant height to % EH and stems.

ADF concentration was lower in corn silage (29.0%) than in sorghum silage (34.9%). The low ADG of sheep fed sorghum silage (18.1 g compared to 64.5 g for corn silage) was primarily due to low DMI (649 g) and low DDM (55.6%) of the sorghum silage compared to the high DMI (777 g) and high DDM (63.8%) of corn silage. A regression analysis showed that nearly equal amounts of DDM intake above maintenance were needed for a unit of ADG from corn silage and from sorghum silage.
Anion Leaching in Two Kentucky Soils under Conventional Tillage and a Killed‐sod Mulch1
Authors: McMahon M. A. , Thomas G. W.
Published: July 2010

This study was established to determine the reasons for the larger losses of nitrogen under corn grown in killed sod as compared to conventionally tilled corn. No crop was grown. Two soils, Maury silt loam, a well‐drained soil with rapid permeability and Lowell silty clay loam, a well‐drained soil with slow permeability, were used. Chloride was used as a tracer for nitrate since it is little affected biologically. Soils were sampled by hand using a soil tube periodically to a depth of 90 cm in 15 cm increments so that both nitrate and chloride could be determined. Differences between distributions of nitrate and chloride were ascribed to mineralization and/or denitrification.

On the Maury silt loam (Typic Paleudalfs, fine, mixed, mesic), no evidence of denitrification was found. Mineralization of nitrate was high and no leaching of chloride or nitrate occurred under conventional tillage during the growing season. Under the killed sod, mineralization was lower and leaching was appreciable during the growing season. During the following winter, leaching was similar on both tillage treatments, but because of the differences in leaching during the growing season, essentially all of the chloride and nitrate were removed from the 90 cm profile under the killed sod and only about half from conventionally tilled soil by the following April.

On Lowell silty clay loam (Typic Hapudalfs, fine, mixed, mesic) there was similar behavior during the growing season except that some leaching occurred even on the conventionally tilled soil and denitrification apparently occurred under both tillage treatments at the depth where organic matter was highest.

The results suggest that, during the growing season, nitrate losses by leaching and a lower rate of mineralization are responsible for the lower yields of corn observed with low nitrogen rates under a killed‐sod mulch. Rates of nitrate and chloride movement during the winter were about the same under both conventional tillage and killedsod mulch.
Nitrogen Flux into Corn Roots as Influenced by Shoot Requirement1
Authors: Edwards J. H. , Barber S. A.
Published: July 2010

Knowledge of the N flux characteristics of corn (Zea mays L.) roots is important in determining the N fertilizer practices needed for efficient N fertilizer use. Fertilizing a portion of the root system with N increases the N uptake required per unit of root fertilized over that in which all roots are fertilized with N. The effect that fertilizing a portion of the roots with N has on the N influx characteristics of corn roots has not been evaluated. Hence the objective of this research was to determine if shoot N requirement influenced N influx/m of corn root. Trimmed‐ and split‐root procedures were used in solution culture experiments in the growth chamber to vary the amount of N‐absorbing roots/unit of shoot and determine its effect on N influx. Both NH+4 and NO−3 forms of N were used.

Trimming corn roots 2 days before measuring influx resulted in only small increases in N influx/m of root so that N uptake/plant was greatly reduced by trimming. Splitting the roots between N‐containing and N‐free solutions from seedling stage until 16 or 18 days, when influx was measured, resulted in larger increases in net N influx than when the roots were trimmed 2 days before influx measurement. Nitrogen level within the root was not related to N uptake rate/m of root in either experiment.

It appears that increasing shoot demand for N does not immediately affect N influx into the root but that the capability for higher N influx is developed when plants are grown under N stress.
Corn Plant Water Stress as Influenced by Chiseling, Irrigation, and Water Table Depth1
Authors: Reicosky D. C. , Campbell R. B. , Doty C. W.
Published: July 2010

Improved plant water status through improved soil and water management practices can result in efficient crop production and water utilization in the compact layered soils that restrict rooting in the Southeast. The effect of chiseling and irrigation on plant water status was evaluated through leaf water potential, stem diameter, and stomatal resistance measurements. Corn (Zea mays L.) was grown on a Varina sandy loam (Typic Paleudult) chiseled to 38 cm and compared with that grown on conventionally tilled plots. In 1972 chiseling had no measurable effect on the daily minimum leaf water potential under the same radiant energy level. At tasseling in 1973, with a water table 80 cm from the surface, chiseling resulted in deeper‐rooted corn that enabled utilization of water in the capillary fringe above the water table, and resulted in slightly higher (less negative) daily minimum leaf water potential, lower stomatal resistance, and smaller stem diameter fluctuations. In 1973, plant‐water status on chiseled plots was comparable with that on furrow‐irrigated plots. The cumulative effects of the small improvement in midday plant water status from chiseling resulted in a 8‐metric ton/ha increase in corn ear yields. These findings suggest chiseling of soils with root restricting layers can result in increased corn production, particularly when the water table is approximately 80 cm from the soil surface at tasseling.
Genotype Variation in Nutrient Uptake Efficiency in Corn1
Authors: Bruetsch T. F. , Estes G. O.
Published: July 2010

Information is lacking on the efficiency of nutrient use by corn (Zea mays L.) genotypes of varying maturity. The objective of this study was to characterize the nutrient accumulation of 12 corn genotypes of commercial importance and of varying maturity under field conditions. Relative maturity of the genotypes was established based on percent dry matter (% DM) of the plant tops after 115 days of growth. Significant variability occurred among the genotypes with respect to dry matter yield and accumulation of P, K, Ca, Mg, Fe, and Zn. Significant positive correlations existed between % DM and foliage P (concentration and content) indicating that higher P levels occurred in the earlier maturing genotypes. Genotypes also differed in dry weight production per gram of N, P, K, Ca and Mg absorbed; the relationship between P concentration and relative maturity of the genotypes was the most consistent. The efficiency of dry matter production per unit of P absorbed was greatest for the later maturing hybrids.
Chemical Desiccation of Grain Sorghum1
Authors: Gigax D. R. , Burnside O. C.
Published: July 2010

Desiccation of grain sorghum [Sorghum bicolor (L.) Moench] could benefit seed producers and farmers by permitting earlier combining, maintaining seed viability, and controlling perennial weeds. The rate of sorghum seed drying, seed viability, and plant lodging following desiccation was determined. ‘RS 626’, a widely grown hybrid grain sorghum, was desiccated with glyphosate [N‐(phosphonomethyl)glycine], paraquat (1,1′‐dimethyl‐ 4,4′‐bipyridinium ion), and a 28% N solution at 30 and 25% seed moisture in 1973 and 35% seed moisture in 1974. Six grain sorghum inbred lines desiccated in 1973 gave differential responses. Glyphosate at 2.24 kg/ha and paraquat at 1.12 kg/ha would permit combining (20% seed moisture) 5 to 7 days earlier when desiccated at 30% seed moisture in 1973 and 35% in 1974. However, when desiccated at 25% seed moisture in 1973, only 2 days were gained. Combine yields were reduced due to sorghum lodging following desiccation with glyphosate at 1.12 and 2.24 kg/ha and paraquat at 1.12 kg/ha at 30% seed moisture in 1973. Similar combine losses were experienced on plots receiving glyphosate at 1.12 and 2.24 kg/ha applied at 35% seed moisture in 1974. Data for 1974 showed that germination and emergence percentages of seed from desiccated plots were higher than that from unsprayed plots because an early killing frost reduced seed viability of higher moisture seed from untreated checks. Common milkweed (Asclepias syriaca L.) stands in the succeeding growing season were reduced in one of two experiments with fall applications of glyphosate at 1.12 and 2.24 kg/ha.
Use of Acrylic Plastic as Rhizotron Windows1
Authors: Taylor H. M. , Böhm W.
Published: July 2010

Reliable cotton (Gossypium hirsutum L.) rooting densities (cm roots/cm3 soil) for bulk soil have been estimated previously from the number of visible roots in sandy soil immediately behind glass rhizotron windows. The present study determined whether soybean [Glycine max (L.) Merr. ‘Corsoy’] rooting densities could be estimated reliably in Ida silt loam (fine‐silty, mixed, mesic, Typic Udorthent) from the number of visible roots at the soil‐acrylic plastic windows of the Ames, Iowa rhizotron.

Rooting density was evaluated as a function of soil depth and distance from the plastic‐soil interface in one compartment at the rhizotron. Fifty volumetric soil samples were collected at ten depths and at five distances from the interface. Roots were washed from the Ida silt loam soil. Root length contained in the sample was estimated using a laser modification of the Rowse‐Phillips root‐length instrument.

Rooting density was substantially greater in the 2‐mm thick layers near the plastic‐soil interface than in bulk soil behind it. Acrylic plastic windows apparently are satisfactory for use in root growth boxes or rhizotron compartments for phenological or for comparative experiments, but glass rhizotron windows should be used in rooting density studies.
Evaluation of Resistance and Mass Transport Evapotranspiration Models Requiring Canopy Temperature Data1
Authors: Blad Blaine L. , Rosenberg Norman J.
Published: July 2010

The increasing use of thermal scanners on aircraft and satellites makes it likely that data on surface temperature for large areas will become routinely available. If reliable evapotranspiration methods which incorporate surface temperature data can be developed an important tool for research and application in hydrology, in irrigation scheduling, and in other water management procedures will result.

A ‘resistance model’ which stems from the work of Brown and Rosenberg and a mass transport (Daltonian) model for estimating evapotranspiration (ET) were tested on large fields of naturally subirrigated alfalfa (Medicago sativa L.). Both models make use of crop canopy temperature data. Temperature data were obtained with an IR thermometer and with leaf thermocouples. A Bowen ratio‐energy balance (BREB) model, adjusted to account for underestimation of ET during periods of strong sensible heat advection, was used as the standard against which the resistance and mass transport models were compared.

Daily estimates by the resistance model were within 1C% of estimates made by the BREB model. Daily estimates by the mass transport model did not agree quite as well. Performance was good on clear and cloudy days and also during periods of nonadvection and strong advection of sensible heat.

The performance of the mass transport and resistance models was less satisfactory for estimation of fluxes of latent heat for short term (15 min) periods. Both models tended to overestimate at low LE fluxes.
Resistance‐energy Balance Method for Predicting Evapotranspiration: Determination of Boundary Layer Resistance and Evaluation of Error Effects1
Authors: Verma S. B. , Rosenberg N. J. , Blad B. L. , Baradas M. W.
Published: July 2010

Accurate estimates of evapotranspiration (ET) over large areas are needed for hydrologic studies, irrigation planning and scheduling, and other practices related to efficient utilization of water resources. One approach is the use of a resistance‐energy balance model of ET, the data for which can be supplied, in part, by remote sensing and in part from easily accessible records of National Weather Service observations. This model requires measurement of boundary layer resistance, crop and air temperature, net radiation, and soil heat flux. The objectives of this paper are i) to test the utility of the proposed model, ii) to determine boundary layer resistance at varying stages of crop growth, and iii) to evaluate the relative influence of errors in measurement of the meteorological and crop input parameters used.

Measurements were made in fields of sorghum [Sorghum bicolor (L.) Moench] and millet (Panicum meliaceum L.) grown at Mead and Mitchell, Neb. Boundary layer resistance was estimated from friction velocity measurements used in a stability‐corrected aerodynamic method. Friction velocity was computed by means of the Deacon‐Swinbank approach. Evapotranspiration rates estimated by the resistance model compared well with results of lysimetric and energy balance measurements, on both a short‐period and a daily basis.

The error analysis, in conjunction with field measurement, indicates that the resistance model evapotranspiration estimates are quite sensitive to errors in crop temperature measurement, especially in nonadvective conditions, but are less strongly affected by errors in the estimation of boundary layer resistance.
System for Growing Plants under Controlled Redox Potential‐PH Conditions1
Authors: Reddy C. N. , Jugsujinda Aroon , Patrick W. H.
Published: July 2010

Redox potential and pH are two soil conditions that exert major influence on the solubility and availability of plant nutrients. In order to study the effects of these conditions on the transformation of plant nutrients in the soil and their uptake by plants, it is necessary to control pH and redox potential over a wide range of values. A relatively simple system has been developed by which soils can be incubated under conditions of controlled redox potential and pH. Rice plants were grown in the soil suspensions incubated at six different redox potentials (—200, —100, 0, +100, +200, and +400 mV) and four pH values (5, 6, 7, and 8).
Extended Field Use of Screen‐Covered Thermocouple Psychrometers1
Authors: Brown Ray W. , Johnston Robert S.
Published: July 2010

The use of screen‐covered thermocouple psychrometers for in situ measurements of soil water potential has been criticized because of possible soil and micro‐organism contamination through the screen covering. Double‐junction Peltier psychrometers with a screen covering were installed in the soil under field conditions for periods ranging from 2 to 40 months of continuous exposure, and were then removed and examined for evidence of loss of calibration sensitivity and contamination by soil particles and micro‐organisms. The uncleaned psychrometers were recalibrated in the laboratory and then disassembled and examined under a microscope (250 ✕) for contamination. Although slightly more than half of the units lost some sensitivity after field exposure, the average decrease was less than 5%. The psychrometer cavities were all nearly free of soil particles, the thermocouple junctions were shiny, and no evidence of microbial attack was evident. It appears that long‐term field exposure of screen‐covered psychrometers is no more detrimental to their performance than that of ceramic or other psychrometers.
The Bur Enclosure of the Caryopses of Buffalograss as a Factor Affecting Germination1
Authors: Ahring Robert M. , Todd Glenn W.
Published: July 2010

The seed‐bur of buffalograss, Buchloe dactyloides (Nutt.) Engelm., consists of a tightly held rigid cluster of four to five spikelets enclosed in thickened glumes. Germination of the bur is often difficult, requiring lengthy prechill treatments to attain maximum percentages. Caryopses contained in the bur germinate readily when extracted by hand, generally without additional pregermination treatment. The objective of this study was to evaluate the effect of the oil present in the bur enclosures on germination.

Fresh seed burs were hammermilled to separate caryopses from their enclosures. Hulls or empty burs (100 g samples) were further pulverized and then refluxed in 1,000 ml of distilled water overnight. The oil(s) present in the aqueous solution was evaporated in diethylether, and its properties characterized with infrared spectrophotometry and gas chromatography. A series of tests on the effect of the oil on germination and seedling growth was conducted. Treatments to counteract the effect of the bur enclosure on germination were also studied.

The results showed that: 1) Empty burs contain 2.8% oil(s) by weight; 2) Caryopses extracted by hand germinate readily, the outer glumes, by restricting water movement, may account for low laboratory germination of the seedburs; 3) Dipping the caryopses in the oil extract reduced germination by 47.2%; and 4) Dipping the root tips of healthy seedlings in the oil extract resulted in stunting plant growth. Prechilling at 5 to 10 C for 6 to 8 weeks or presoaking seed‐burs in 5.25% sodium hypochlorite for 72 hours was sufficient to overcome the bur effect on germination. The length of both treatments needed to promote germination varied between seed lots studied. Subjecting the seed‐burs to heat (drying) up to 70 C for 12 hours improved germination. Treatments beyond 70 C for more than 12 hours reduced seed viability.
Production of Corn and Sorghum Grain in Double‐Cropping Systems1
Authors: Nelson L. R. , Gallaher R. N. , Bruce R. R. , Holmes M. R.
Published: July 2010

Double‐cropping systems involving no‐till planting are becoming popular in the southeastern USA, but adequate management practices have not been developed. Therefore, this study was conducted to determine the effects of the following tillage systems. Corn [Zea mays (L.)] and grain sorghum [Sorghum bicolor (L.)] were planted without tillage following winter wheat [Triticum aestirum (L.)] or barley [Hordeum vulgate (L.)] and with conventional tillage following previous summer crop at two locations in Georgia for 4 years with and without irrigation. Corn and grain sorghum yields did not differ significantly for conventional tillage and no‐till plantings made on the same date. No‐till corn and grain sorghum produced higher yields when early planted (after small grain for forage) than when late planted (after small grain for grain). Irrigation increased conventionally tilled corn yields by 31% (at Experiment) and grain sorghum yields by more than 20%. The smaller increases observed for irrigated early‐planted no‐till corn and grain sorghum were attributed to a higher soil water content on nonirrigated no‐till. Irrigation did not increase yields of late planted no‐till corn and grain sorghum due to interfering biological factors.
Cold Tolerance Evaluation of Several Centipedegrass Selections1
Authors: Johnston W. J. , Dickens Ray
Published: July 2010

Centipedegrass (Eremochloa ophiuroides (Munro) Hack.), an excellent lawn grass throughout much of the lower South, is often limited by its lack of cold tolerance. Studies were conducted to determine variability in cold tolerance among centipedegrass selections as affected by hardening conditions. Seven clonal selections were grown under controlled environmental conditions using sand culture and cold hardened during a 21‐day exposure with a 12‐hour photoperiod, 22 C day (16 C day in the second experiment), 4 C night. Unhardened plants recieved a 31 C day, 25 C night.

In one experiment, following hardening treatments, plants were exposed to —9.7 C for 1.5, 3, 5, 7 or 9 hours. In a second experiment plants were exposed to —3.0, —5.6, —7.3, or —10.1 C for 4 hours. After low‐temperature exposure plants were transferred to favorable growing conditions and rated for top‐kill and survival after 7 and 21 days respectively.

Top‐kill increased and survival decreased as duration of cold exposure increased or temperature decreased. Exposing centipedegrass to cold hardening temperature regimes prior to freezing resulted in less top‐kill and more survival. Cold hardening increased low‐temperature tolerance a maximum of 2.3 C; i.e., percent survival was the same for hardened plants at —9.6 C as for unhardened plants at —7.3 C. Selections differed in amounts of top‐kill. Mississippi I, Tennessee Hardy, Oklawn, and FC‐2 were generally less susceptible to top‐kill than PllA,, Mississippi II, and FC‐8. No survival differences were noted among Centipedegrass selections following low‐temperature exposures.
A Self‐Propelled High‐Clearance Soil Coring Machine1,2
Authors: Bausch Walter , Onken A. B. , Wendt C. W. , Wilke O. C.
Published: July 2010

Mechanical soil sampling equipment currently available is suitable for sampling prior to crop establishment or in low growing crops but cannot be used without plant damage in some tall crops. A self‐propelled high‐clearance soil coring machine was designed and constructed to obtain soil samples in a tall standing crop at a range of lateral as well as vertical distances. The sampler is hydraulically operated and has vertical pressure and rotary drilling capabilities. This equipment has a lateral travel span of 152 cm and the capability of coring to a depth of 9 m with the mast in any lateral position on the track. Two operators can use the sampler without difficulty; however, three operators are desirable if a large number of samples are to be taken. As many as eighty 30‐cm increment soil samples have been taken per hour when sampling a moist sandy soil to a depth of 2 m.
Preliminary N, P, and K Foliar Diagnostic Norms for Soybeans1
Authors: Sumner M. E.
Published: July 2010

The previous successful application of Beaufils' Diagnosis and Recommendation Integrated System (DRIS) to crops such as corn and sugarcane as a foliar diagnostic tool capable of revealing mineral imbalances led to the need for the development of DRIS norms for soybeans [Glycine max (L.) Merr.]. Preliminary DRIS norms for soybean leaves are developed from 1,245 sets of data on elemental (NPK) leaf composition and corresponding yields. This is done by dividing the population of observations into two subpopulations on the basis of yield. The norms are calculated from those forms of expressing the leaf parameters which significantly discriminate between the two subpopulations. The degree of nutrient imbalance in the plant is expressed in terms of a DRIS index which measures the extent to which a particular nutrient deviates from the established norm. The norms are developed in such a way that the influence of age of tissue sampled on the diagnostic index is minimized. The DRIS norms enable one to diagnose whether N, P, or K is the nutrient most limiting to soybean production in a particular case to be diagnosed. The results show that the diagnosis can be made irrespective of variety and age at which the leaf is sampled. The advantage of the DRIS system in predicting nutrient imbalances even when the nutrient concentration in the plant is in or above the critical or sufficiency level range, is illustrated.
Field‐Measured Water Uptake of Sudangrass Roots as Affected by Fertilization1
Authors: Flühler H. , Ardakani M. S. , Szuszkiewicz T. E. , Stolzy L. H.
Published: July 2010

Cultural practices could affect the flow of water and solutes toward groundwater. In this field experiment we analyzed the effect of fertilization on water uptake of sudangrass (Sorghum vulgare sudanense, Germain's piper cultivar) and its indirect influence on deep drainage and nitrate leaching. Root water uptake was calculated as sink term in the continuity equation using successive measurements of water content and matric potential profiles in connection with field measured hydraulic conductivity functions. The experiment was conducted in three field plots on Hanford fine sandy loam (coarse‐loamy, mixed, thermic, Typic, Xerorthent).

Fertilization increased dry matter production and water uptake significantly and reduced deep drainage and nitrate leaching. Water uptake patterns and root length distribution was not correlated. Mainly due to fertilization with nitrate nitrogen, the evapotranspiration approximated the amount of irrigation water applied. These results indicate that optimum water and fertilizer use and minimum groundwater pollution per unit crop production are intimately linked together.
Soybean Growth and Elemental Content as Influenced by Soil Amendments of Sewage Sludge and Heavy Metals: Seedling Studies1
Authors: Dowdy R. H. , Ham G. E.
Published: July 2010

Many research studies have substituted soluble metal salts for sludge borne metal in attempts to define heavy metal uptake by plants. To assess this experimental approach and the effect of sewage sludge on the availability of soluble metals, soybean uptake of sludge and salt borne heavy metals was measured.

Soybeans (Glycine max L. var. ‘Corsoy’) were grown 30 days in a growth chamber on an Aquic Hapludoll loam soil receiving the following treatments: a) sewage sludge applications of 0, 34, 67, and 134 metric tons/ha; b) addition of a combination (L) of heavy metals, as inorganic salts, of 10 mg Cu, Cd, Cr, and 18 mg Zn/kg soil at three levels, L, 2L, and 4L; and c) sludge plus metal additions. Sludge applications increased dry matter production, tissue P and N content and reduced root nodulation. Heavy metals depressed plant growth and nodulation in the absence of sludge. A 34 metric tons/ha sludge application eliminated these adverse effects. The Zn concentration of seedling tissue increased with applied Zn, from both sludge borne and salt borne sources. However, per unit of added Zn, more Zn accumulated in tissue grown on sludge amended soil. The tissue concentration of Cu and Cd increased with added sludge. A 34 metric tons/ha sludge application depressed salt borne Cd uptake. Sludge borne Cr and Ni were not taken up by the plants. Plant uptake of salt borne Cd and Ni was enhanced by the presence of Zn, Cu, and Cr. Hence, the uptake of sludge borne metals cannot be predicted from data obtained in studies using inorganic salts as the metal source.
Influence of Seed Size and Density on Germination, Seedling Emergence, and Yield of Grain Sorghum1
Authors: Maranville Jerry W. , Clegg Max D.
Published: July 2010

Seed size is highly influential in determining germinability and seedling vigor of grain sorghum (Sorghum bicolor L. Moench), but whether this factor is predominate over seed density (i.e. specific gravity) has not been established. A 2‐year study was conducted to determine to what extent seed size and density influence germination and subsequent field performance. Large and small seed lots from the same genotype were compared to “more dense” and “less dense” seed lots which were separated using either urea‐phosphate or sucrose solutions. The results indicated that seed lots with larger and denser seeds had a higher percent germination. The data also supported the conclusion that a higher percentage of viable seeds could be selected from seed lots with low average germinability by using specific gravity separations. However, the establishment of seedlings, final stands, and grain yields were not a function of size or density when the same number of viable seeds were planted in the field.
Effect of Management Practices on Thatch Accumulation, Turf Quality, and Leaf Spot Damage in Common Kentucky Bluegrass1
Authors: Murray J. J. , Juska F. V.
Published: July 2010

Excessive thatch accumulation is a serious problem in maintenance of turfgrasses. Several turfgrass management practices have been shown to influence thatch accumulation. The present study was undertaken to determine the effectiveness of various management practices alone and in combinations in preventing thatch accumulation in common Kentucky bluegrass (Poa pratensis L.), and the relationship between thatch accumulation, turf quality, and leaf spot damage. Treatment effects on thatch accumulation were assessed by measuring total amount of organic matter in the thatch layer. Ratings for turf quality and leaf spot damage caused by Helminthosporium spp. were based on color and stand density.

Three sets of treatments were arranged in a split‐split plot design: (A) Mower clippings removed vs. not removed; (B) lime applied as needed to maintain a soil pH 7, lime applied at 4.8 to 7.3 kg/are biannually, and no lime (soil pH 5.4); and (C) sub‐sub‐plots that were: (a) aerified (coring), (b) handraked, (c) verticut, (d) had applications of a wetting agent, (e) had additions of organic matter (Milorganite®3), and (f) untreated. Thatch accumulation was not significant during the first 5 years of the study. Clipping residue left on plots significantly contributed to thatch accumulation when all treatments were averaged, and after thatch had built up to approximately 1.25 cm in depth. Residue from clippings did not increase thatch on aerified turf or turf receiving the wetting agent. Maintenance of soil pH of 6.8 and biannual lime applications effectively reduced thatch accumulation over that of untreated soil. Biannual lime applications did not increase decomposition beyond that of liming as needed to maintain a favorable soil pH. Aerification resulted in the least amount of thatch followed by the verticut and handraked treatments. The wetting agent did not effectively reduce thatch, and the addition of Milorganite® significantly increased thatch production.

The highest quality turf was produced by permitting clippings to remain on the turf, maintaining a favorable soil pH and aerification. Clippings increased turf quality during temperature and moisture stress periods. Leaf spot damage was reduced by aerification, applying the wetting agent, and removing clippings. There was no significant difference in thatch level among the check, aerified, handraked, verticut, and wetting agent 14 months after their discontinuance.
Peanut Seed Germination as Related to Soil Water Regime During Pod Development1
Authors: Pallas J. E. , Stansell J. R. , Bruce R. R.
Published: July 2010

The problem of poor peanut (Arachis hypogaea L.) seed germination has appeared to follow exceptionally dry years in Georgia; consequently, the interaction of soil water availability during the growing season and subsequent seed germination were studied. These results are a composite of 4 years of study under controlled rainfall shelters on Tifton loamy sand, a member of the fine‐loamy, siliceous, thermic Plinthic Paleudults, at six soil water levels. Soil water levels involved irrigation at specified soil water tensions in surface 30 or 60 cm. Soil water tension ranged from + 0.2 to > 15 bar. Good germination of all varieties was obtained when the average soil water tension in the surface 30 cm was maintained at less than 0.6 bars. On the other hand, allowing ‘Florigiant’ to reach a soil water tension greater than 15 bars during the growing season lowered its percentage of sound mature kernels 34%. Of those sound mature kernels, germination was lowered on an average 20%. By contrast, under the similar treatment, SMK's of ‘Florunner’ and ‘Tifspan’ were lowered 22 and 7%, respectively, and the germination of either cultivar was lowered only about 5%. Thus, the large‐seeded Virginia type peanut, Florigiant, was found to be the most susceptible to droughty soil conditions. Irrigation appears to be good insurance against poor peanut seed germination in the following year.
Influence of Plant Population on Field Performance of Three Soybean Cultivars1
Authors: Lueschen W. E. , Hicks D. R.
Published: July 2010

Soybean [Glycine max (L.) Merr.] seeding rates in commercial fields have generally been greater than necessary to obtain maximum seed yield. Because of higher seed costs, we conducted a field study to evaluate the agronomic response of three recently developed soybean cultivars on a clay loam (Aquic Argiudoll) to three plant populations − 171,000, 342,000, and 513,000 plants/ha. Significant yield increases were obtained in only 1 year as a result of higher plant population. Yields in the other years remained constant across populations. Plant height and maturity were not affected by plant population while lodging was increased at higher plant densities. The height above the soil surface of the lowest pod‐bearing node increased as plant density was increased. Numbers of branches, pods, and seeds per plant decreased as population increased. Results presented herein indicate that soybeans have the capacity to compensate for a wide range in plant densities without affecting yield.
Fitting Plants Nutritionally to Soils. III. Sorghum1
Authors: Brown J. C. , Jones W. E.
Published: July 2010

Fifteen sorghum (Sorghum bicolor (L.) Moench) lines, representing diverse germplasm currently used in crop breeding programs in the United States, were grown on the seven soils, used in part I of this study, to produce Fe, Zn, and Cu stresses or Al and Mn toxicities in soybeans. All 15 sorghum lines developed Fe and Zn deficiencies with symptoms ranging from some interveinal chlorosis to necrotic and twisted leaf tips. The sorghum lines responded differentially to Cu stress. When Cu was added to the soil, yields increased and P, Fe, and Zn concentrations significantly decreased in the plant material.

The sorghum lines responded differentially to Al in Bladen soil. Five lines grew poorly and developed a chlorosis with some purple pigmentation; five lines were green and made good growth; and five lines were intermediate in their response. The chlorotic lines contained significantly less Fe and P than the green sorghum. On Richland soil (high Mn), yields were relatively good and the sorghum plants did not develop any persistent toxicity symptoms.

Care should be taken to select the sorghum line best adapted to Fe, Zn, or Cu stresses and to Al toxicity so that the plant and the soil may be compatible.
Effect of Forage Harvest Frequency on Subsequent Alfalfa Seed Production and Pollen Quality1
Authors: Abu‐Shakra S. , Bhatti M. L. , Ahmed H.
Published: July 2010

The most suitable time during the growing season for maximum seed production of alfalfa (Medicago sativa L.) depends on geographic area. This investigation was undertaken to study the influence of four forage harvest treatments on the subsequent seed production and pollen quality characteristics of irrigated alfalfa in Lebanon. In addition, wild alfalfa pollinators were collected and identified. Two seed crops were produced after both one and two forage harvests. After three and four forage harvests, only one seed harvest was produced. The two seed crops following the one and two forage harvest treatments produced mean yields of 1,116 and 1,140 kg/ha, respectively. The first seed crop contributed 83% of the total yield. The seed yield components of number of stems/plant, racemes/stem, pods/raceme, and seeds/pod of the first seed crop were higher than those of the second crop. Hard seed percentages were more than 50% in the second crop where seeds developed between late September and early November, compared to less than 20% in the first crop where seeds developed between late June and end of August. Pollen viability was not significantly influenced by forage cutting treatment. However, pollen tube growth immediately after germination was most vigorous from late May to the end of June. This coincided with the flowering of the first seed crop after one and two forage harvests. Four species of Megachile, nine of Andrena, one of Halictus, one of Anthidium and two of Anthophora were identified as alfalfa pollinators.
Sunflower Yield and Water Use as Influenced by Planting Date, Population, and Row Spacing1
Authors: Alessi J. , Power J. F. , Zimmerman D. C.
Published: July 2010

Sunflower (Helianthus annuus L.) has only recently been grown commercially as an oilseed crop in the drier regions of the Northern Great Plains. This study was conducted to acquire preliminary information on seed yield, oil concentration, and water use for oil‐type sunflower as affected by planting date, plant population, and row spacing; and to obtain an indication how these results were affected by yearly variation in precipitation and air temperature. Sunflower was grown at Mandan, N. Dak. at plant population of 25,000, 50,000, 75,000, and 100,000 plants/ha in 30‐ and 90‐cm rows on Temvik silt loam (Typic haploboroll). Soil water withdrawal by sunflower was generally confined to the upper 150‐cm soil depth. Water use by sunflower was consistently greatest for earlier plantings, and was not affected by population or row spacing. Significant positive correlations were obtained between seed yield and water use after 50% flowering. Water use before flowering was much greater in a year of high precipitation during this period than in a year when pre‐flowering precipitation was lower. Seed and oil yield were usually highest for lowest populations and for 30‐cm row spacing. Correlation coefficients showed that 80% of the total variation in oil concentration was accounted for by variation in water use and temperature. Oil concentration was more strongly influenced by water use than by temperature. Although late planting in 1973 increased seed yield for some of the higher plant populations, flowering was delayed until early September, increasing the frost hazard. Days from planting to flowering (50%) decreased as planting date was delayed.
Top and Root Relations of Field‐Grown Soybeans1
Authors: Sivakumar M. V. K. , Taylor H. M. , Shaw R. H.
Published: July 2010

Field data describing both the top and root growth of soybeans [Glycine max L. (Merr.)] at different morphological stages are very limited. Such quantitative data are essential for analyzing or simulating growth patterns of whole soybean plants.

Soybean top and root growth studies were conducted at the Western Iowa Experimental Farm on Ida silt loam soil [fine, silty, mixed (calcareous) mesic family of typic Udorthents]. Plant height, dry matter distribution of above‐ground plant parts, leaf area index, root length, and root dry weight distribution were measured at different physiological stages.

Top‐root ratio of soybeans was 3.8 when the plants were in stage V6, and the ratio increased to 9.0 by the time that the plants reached stage V15R2. From the root length and leaf data, the total length of roots required to supply water and nutrients to each m2 leaf area was calculated. These root lengths increased from 630 m/m2 leaf area when the plants were in V6 stage to 1,190 m/m2 at V13R2 stage then decreased to 345 m/m2 at stage V15R2 as the soil dried. Root length in a specific layer decreased whenever soil was drier than —2 bars or volumetric water content was below 16%.

Plant height and leaf area were positively correlated (r = 0.95). Most of the leaf area was concentrated in the upper portions of the soybean canopy when leaf area was maximum.
Trickle Irrigation and Fertilization of Tomatoes in Sand Dunes: Water, N, and P Distributions in the Soil and Uptake by Plants1
Authors: Bar‐Yosef B.
Published: July 2010

Trickle irrigation has a special advantage in sandy soils where the accurate control of water and ions in the plant's root volume is critical. The purpose of the present work was to investigate the simultaneous migration of water and nutrients from a drip source in the field, to study the plant's response to various moisture and concentration distributions in the soil and to define optimal conditions for maximum yields.

Tomato plants (Lycopersicum esculentum Mill.) grown in a field of fine sand received various daily rates of water, N, and P applied through a trickle irrigation system. Highest fruit yield (about 110 tons/ha) was obtained, when the daily average water content in the soil root volume was about 5% (w/w), the N concentration in the soil solution 140 ± 40 ppm N, and the N uptake rate about 100 mg N plant−1day−1. The estimated daily water consumption by the plants varied between 0.4 and 1.0 liter plant−1day−1, depending on the plants leaf area and climatic conditions. The estimated water quantity used to produce 1 g dry matter was similar in all the treatments — about 250 ± 40 g H2O/g d.m.