bluuebunny/crossref_metadata_2025 huggingface dataset:
Potato Tubers and Soil Aeration1
Authors: Cary J. W.
Published: July 2010

Potato plants are more sensitive to soil oxygen stress than many other common crops. Some recent literature suggests this may be due to a relatively high oxygen requirement for tuber growth, rather than a greater requirement for the roots per se. Consequently, the oxygen consumption of growing potato tubers (Solanum tuberosum cv. Russet Burbank) was measured in the field on a Portneuf silt loam (coarse‐silty, mixed, mesic Durixerallic Calciorthid). Typical rates were 15 µg O2 cm−2 hr−1. A simple method for measuring soil oxygen diffusion rates in the laboratory was then devised, utilizing an oxygen meter and a stream of N2 gas. Soil conditions such as texture, bulk density, compaction around expanding tubers, oxygen sinks and water contents were studied with respect to their relative effects on limiting oxygen uptake by tubers. The minimum soil oxygen diffusion coefficient required for adequate tuber aeration is quite sensitive to the soil respiration rate and the depth of soil covering the tubers. Water contents of “field capacity” or a little wetter were found to not necessarily inhibit tuber aeration in loamy sand, silt loam, and silty clay soils provided the bulk densities were not excessive; i.e., greater than 1.6 or 1.7 Mg m−3 in the silt loam. Reduced aeration due to compaction around growing tubers is a possibility in the silty clay, but probably not in well drained silt loam or loamy sand. The criteria for a minimum acceptable soil oxygen diffusion coefficient must be based on tuber periderm permeability, soil ethylene generation, and other anaerobic soil reactions, as well as tuber respiration per se.
Phosphorus Efficiency and Phosphate–Iron Interaction in Maize1
Authors: Elliott George C. , Läuchli André
Published: July 2010

Genotypic differences in absorption or utilization of P might be exploited to improve efficiency of fertilizer use or to obtain higher productivity on P‐deficient soils. Experiments were conducted to determine rates of P absorption, P accumulation, and P utilization in 15 inbred genotypes of maize (Zea mays L.) at 3 P supply levels. Nutrient solution P concentrations were maintained at approximately 5,25, and 100 mmol m−3 (P1, P2, and P3, respectively) with an alumina‐P solid phase buffer. There were significant differences among genotypes for rate of P utilization, but not for rate of P absorption by roots. Utilization of P was negatively correlated with the ratio of inorganic P accumulation rate to total P accumulation rate, indicating that P utilization is limited by partitioning of P between free orthophosphate and organically combined forms. Absorption of P by roots and utilization of P in shoots were positively correlated. Iron deficiency occurred with all genotypes grown in the P2 and P3 treatments, but not in the P1 treatment. Both Fe absorption by roots and partitioning of Fe to shoots decreased with increasing concentration of P in the nutrient solution. Utiliition of Fe (rate of dry matter production per unit of Fe accumulated) in shoots increased in Fe‐deficient plants. Phosphate‐induced Fe deficiency in maize evidently involves both inhibition of Fe absorption by roots and inhibition of Fe transport from roots to shoots.
Grain Yield and Yield Components of Soft Red Winter Wheat as Affected by Management Practices1
Authors: Frederick J. R. , Marshall H. G.
Published: July 2010

The use of intensive management practices could substantially increase soft red winter wheat (Triticum aestivum L. em Thell.) grain yields in the northeastern USA, but more information is needed about the influence of management factors on components of yield. Our objective was to determine the effects of seeding rate, row spacing, seeding depth, and rate of spring‐applied N fertilizer on grain yield components and to calculate the yield changes associated with changes in the yield components. ‘Roland’ wheat was grown on eight Pennsylvania farms during 1981 and 1982 on either Typic or Ultic Hapludalf soils. Treatments were row spacings of 12.7 and 17.8 cm, seeding depths of 1.9 and 3.8 cm, seeding rates of 101,168, and 235 kg ha−1 and spring N topdressing rates of 0, 34, 67, and 101 kg ha−1. Plot subsamples were used to determine grain yield, tiller number, kernel number per tiller, and kernel weight. The over all treatment means for locations ranged from 291 to 420 g m−2 for yield, 440 to 585 for tillers m−2, 20.0 to 27.6 kernels/tiller, and 27.2 to 35.5 g/l000 kernels. Kernel number per tiller appeared to be consistently below genetic and phenotypic potentials. Yield changes associated with increasing levels of N varied from positive to negative quadratic responses at the low and high yielding sites, respectively. The primary component of yield decreases was reduced kernel weights. Increasing the seeding rate beyond 101 kg ha−1 always resulted in increases in tiller number and decreases in the number of kernels per tiller while increases in kernel weight occurred at six locations. When row spacing was decreased to 12.7 cm, grain yields increased by an average of 8.2%, and the primary contributing component was more tillers per unit area. This was the only treatment without consistent negative responses in at least one other yield component. Increasing planting depth to 3.8 cm reduced the number of tillers and was associated with increased kernel number per tiller at most locations. The only yield change was a decrease at a location where planting date was delayed.
Soyphen: Soybean Growth Stages Modeled from Temperature, Daylength, and Water Availability1
Authors: Hodges Tom , French Vikki
Published: July 2010

The soybean plant (Glycine max L.) responds strongly to daylength and temperature in its phasic development. Daylength responses vary greatly between varieties. Under very dry conditions, water stress may also affect development. Attempts to develop physiologically based large area yield models for soybeans have been hampered by the lack of a growth stage model incorporating these responses and applicable to a wide geographic and climatic range. The objective of this work was to develop a physiologically based model to predict growth stage dates for soybeans for the widest possible range of maturity groups and geographic areas. A phenology model was developed and tested for soybean Maturity Groups I to V based on temperature, daylength, and water availability. Coefficients were also developed, but not tested independently for Maturity Groups 00, 0, and VI to IX. Coefficients for Maturity Groups I to V were developed from 3 years (1971 to 1973) of data with five planting dates per year collected at Columbia, MO. The coefficients were tested on data sets taken at the same time at Spickard and Mt. Vernon, MO and on data for the 1981 season from 22 international sites. The test results indicate that the model will generate reliable estimates of soybean growth stages over a wide range of climatic conditions. The coeffients for Maturity Groups 00, 0, and VI to IX were developed from data from international sites, but no data were available for independent testing. The model is available in the FORTRAN and PL/I programming languages. It is suitable for incorporation into a soybean growth simulation model or for running as an independent crop calendar model. The model may be run wherever daily maximum and minimum temperatures and rainfall are available.
Plant Accumulation and Soil Sorption of Cobalt from Cobalt‐Amended Soils1
Authors: Pinkerton B. W. , Brown K. W.
Published: July 2010

Present industrial uses of Co result in elevated metal concentrations in soils around industrial activities and land treatment facilities. Laboratory and greenhouse studies were conducted to determine Co uptake by tall fescue (Festuca arundinaceaSchreb.) as affected by soils, Co levels, lime additions, Mn additions, and soil layering. In a laboratory sorption study using solutions containing 5 to 1000 mg Co L−1, the Marietta (Aquentic Dystrochrepts) and Norwood (Typic Udifluvent) soils had sorption maxima of 1440 and 3787 mg Co kg−1, respectively. The higher sorption of the Norwood soil was presumably due to the formation of complexes or precipitates between the CaCO3and Co. Addition of up to 6.7 Mg lime ha−1resulted in decreased concentrations of Co in tall fescue grown in soils containing 400 mg Co kg−1. Addition of 50 to 2000 mg MnO2kg−1soil had no effect on Co accumulation by tall fescue. Layering of uncontaminated soil over Co‐amended soil increased plant uptake of Co over that taken up by plants grown in Co‐amended soil alone. Apparently, the healthy roots in the upper layers of soil removed Co from the lower layers of soil; whereas, elevated Co in the total soil volume retarded root development sufficiently to prevent Co uptake. Total Co determinations were as good as or better than any of the three extractants (2.5% acetic acid, 0.01 MEDTA [ethylenediamine tetracetic acid] and DTPA‐TEA [diethylenetriamine pentacetic acidtriethanolamine]) in predicting plant accumulation of Co. Of the tested extractants, acetic acid had the lowest correlation coefficient when compared with plant Co accumulation.
Amino Acid Composition of Tall Fescue Seed Produced from Fungal Endophyte (Acremonium coenophialum)‐Free and Infected Plants1
Authors: Belesky D. P. , Evans J. J. , Wilkinson S. R.
Published: July 2010

The presence of a fungal endophyte (Acremonium coenophialumMorgan‐Jones and Gams) in tall fescue (Festuca arundinaceaShreb.) has been associated with the production of nitrogenous secondary metabolites such as the pyrrolizidine alkaloids. The increased production of secondary metabolites may alter the N balance of the plant affecting the types and amounts of nitrogenous products available for export to developing seed. An investigation was conducted to determine the impact of fungal endophyte status on the amino acid composition of tall fescue seed. New (viable endophyte) and old (stored for at least 2 yr, nonviable endophyte) seed of ‘Kenhy’, ‘KY‐31’, an experimental line “EXP” and ‘Fawn’ were sown in a randomized block design. New seed of Fawn failed to germinate. Seed sown, vegetative tissue, and seed produced were assayed for fungal endophyte status. Endophyte levels in vegetative tissue and seed produced from plants established from old seed were low in fungal endophyte (<20%). Qualitative evaluation of seed amino composition (grams amino acid per 100 grams amino acid recovered) did not reveal any significant alterations in amino acid composition, which could be attributable to fungal endophyte status of the parent plant.
The Effect of Root Temperature and Nitrate/Ammonium Ratio on Strawberry Plants. II. Nitrogen Uptake, Mineral Ions, and Carboxylate Concentrations1
Authors: Ganmore‐Neumann Ruth , Kafkafi U.
Published: July 2010

Strawberry plants (Fragaria ananasa Duch.) have shallow roots and are grown in the field during both hot and cold seasons. The possibility of irrigating and fertilizing the plants daily, through the trickle system, led to the question of what is the best nitrogen form and NO−3/NH+4ratios to be supplied to this crop during the growing season. The effect of four root temperatures (10, 17, 25 and 32 °C) and five NO−3/NH+4mole ratios (0⁄7, 2⁄5, 3.5⁄3.5, 5⁄2, 7⁄0) at constant total N in the solution was studied. To keep constant pH, total nutrient solution and root temperature, continuous flow techniques were used. The solution was flushed through 1‐L pots at the rate of 1 L h−1. When both N forms were present, the rate of total N uptake was higher than when NH+4or NO−3alone was present. The maximum uptake rate was found at 25 °C root temperature. Best conditions for growth were found at 25 °C root temperature when both N forms were present in equal concentration. A preference for NO−3uptake was found during flowering and the fruiting period. Ammonium was preferred during the vegetative growth period. Increasing root temperature decreased total cation concentration and especially that of K+, Na+, and Mg2+, and increased Ca2+in the roots of NO−3‐fed plants. The Na+was accumulated in the crown and did not move to the leaves and fruits. Increasing root temperature reduced inorganic anion concentration in the roots while increasing it in leaves of NH+4fed plants. In the fruits, the ratio of mole of charges of Ca2+to that of H2PO−4was about 1:1 for both N forms.
Transmitted and Absorbed Photosynthetically Active Radiation in Grain Sorghum1
Authors: Rosenthal W. D. , Arkin G. F. , Howell T. A.
Published: July 2010

Relationships defining transmitted (TPAR) and absorbed (APAR) photosynthetically active radiation (PAR) in sorghum [Sorghum bicolor(L.) Moench] canopies do not account for senesced leaves, stalks, and panicles after anthesis. Absorbed PAR by senesced leaves does not directly contribute to photosynthesis, whereas PAR absorbed by panicles does. In addition, senesced leaves, stalks, and panicles reduce transmitted solar radiation reaching the soil and thereby affect soil evaporation. The objective of the study was to examine the combined effect of senesced leaves, stalks, and panicles on TPAR and APAR in a developing sorghum canopy before and after maximum green leaf area index (GLAI) was attained. The study was conducted on a Panoche clay loam (fine‐loamy, mixed, thermic Typic Torriorthent) at the West Side Field Station (CA) near Five Points, CA during 1982 and on a Houston black clay (fine‐montmorillonitic, thermic Udic Pellustert) at the Blackland Research Center (TX) in Temple, TX, during 1983. The experimental designs were three replications of four and five altered canopy treatments (panicles and layers of green and senesced leaves removed) at TX and CA, respectively. Transmitted and absorbed PAR were calculated from PAR measurements above and below the canopy, before and after maximum green leaf area was attained. Transmitted and absorbed PAR differed significantly (95% level) before and after maximum leaf area index was attained. Panicles intercepted 8% of the incoming PAR; stalks 14%; and senesced leaves, 23%. Relationships derived between TPAR and GLAI compared favorably with other published data. Absorption of PAR by panicles, stalks, and senesced leaves should be considered in photosynthesis, evapotranspiration, and crop growth estimates.
Growth, Nitrogen Uptake, and Partitioning in Nitrogen‐Fertilized Nodulating and Nonnodulating Peanut1
Authors: Selamat A. , Gardner F. P.
Published: July 2010

Peanut (Arachis hypogaeaL.) is known to be effective in symbiotic N2fixation, but N deficiencies may occur during rapid vegetative and/or reproductive growth. The effects of N fertilization on growth, N uptake, and N partitioning in nodulating and nonnodulating peanut genotypes were studied during 1982 in the field and a greenhouse experiment at the University of Florida, Gainesville. Three lines, 'Florunner' (FL), 'Early Bunch' (EB), and a nonnodulating line ('M4‐2') were grown in the field on a Lakeland sandy soil (hyperthermic coated Thermic Quartzipsamment) at four N rates (0, 6, 12, and 24 g m−2N) and in pots in the greenhouse at N rates at a factor of 0.05, 0.50, 0.95, and 1.40 N‐strength of Hoagland no. 2 solution, modified to adjust the other nutrients at 0.50 strength. In the field experiment, only the biomass crop growth rate (CGR) and leaf area index (LAI) of all genotypes were significantly increased by N rates. A leaf area index of 3.0 was achieved at 60 days after planting (DAP) when 6 g m−2N or more was applied on the nodulating genotypes. For the nonnodulating genotype (M4‐2), 120 days at 6 g m−2N or 85 days at 24 g m−2N were required to achieve LAI of 3.0. The vegetative and reproductive responses of M4‐2 to N increments were highly positive and essentially linear. Pod and seed yields of nodulated genotypes in field‐grown plants were not significantly influenced by N fertilization. Pod yields were increased in pot‐grown plants in the greenhouse, but nodule number and weight were reduced. A genotype X N rates interaction for plant component yield, leaf N concentration, and N content was observed due primarily to the differential response to N between the nodulating and nonodulating lines. Partitioning of photoassimilate to pods was generally reduced by N fertilization, probably due to vegetative growth stimulation. Florunner cultivar biologically fixed more N2than EB, the amount in FL exceeding the seed requirement (12.2 m−2) if fertilizer N rate was low. These studies suggest that the practice of N fertilization of well‐nodulated peanut does not increase pod or seed yield and is economically counter‐productive.
Partitioning of Assimilate Between Vegetative and Reproductive Growth in Soybean1
Authors: Egli D. B. , Guffy R. D. , Leggett J. E.
Published: July 2010

Changes in the proportion of the total biomass harvested have made an important contribution to the increase in yield in several grain crops. Field experiments were conducted for several years on Typic Argiudoll and Typic Paleudalf soils to investigate the effect of cultivars, growth habit, and environmental conditions on the partitioning of assimilate between vegetative and reproductive plant parts in soybean [Glycine max(L.) Merr.] during flowering and fruit set. The experiments included the following variables; cultivars from maturity group II to V, including both indeterminate and determinate growth habits, optimum and delayed plantings, and moisture stress. Data were collected from growth stage R1 to R6 on vegetative growth characteristics (nodes on main stem, total nodes, and plant height), pod development, and weight of vegetative and reproductive plant parts. Partitioning coefficients were calculated by dividing fruit weight by the total aboveground biomass. The nodes on the main stem and on the branches reached a maximum at R5 in all cases. Determinate cultivars produced fewer nodes on the main stem between R1 and R5; however, they produced more branch nodes and the total node production was greater than the indeterminate cultivars. The number of pods containing developing seed increased until approximately R6, suggesting that the production of new vegetative sinks (node production) in soybean stopped before the total fruit load was established. The partitioning coefficients increased rapidly from < 5% at growth stage R3 to ≥ 30% at R6. The partitioning coefficient at any growth stage varied only slightly across the variables included in the experiments. This suggests that variation in fruit and seed number may be more closely related to variations in crop growth rate than to variations in the allocation of assimilate between vegetative and reproductive plant parts.
Photosynthetic Response of Soybean Canopies to Full‐Season Carbon Dioxide Enrichment1
Authors: Acock B. , Reddy V. R. , Hodges H. F. , Baker D. N. , McKinion J. M.
Published: July 2010

Global atmospheric CO2concentration ([CO2]) is increasing as a result of the burning of fossil fuels. At present there is little information about how agronomic crops will respond to future high [CO2]. To investigate the basic process that will be most affected, soybean [Glycine max(L.) Merr.] canopies were continuously exposed to various [CO2] and photosynthetic rates were measured throughout the growing season. Soybean was grown to physiological maturity in sunlit controlled‐environment chambers in CO2concentrations of 330, 450, 600, and 800 µL L−1. Carbon dioxide fluxes were measured on the canopies at 15‐min intervals every day and used to calculate photosynthetic and respiration rates. Gross photosynthetic rate increased with each increment in [CO2] regardless of stage of development, but there was considerable day‐to‐day and seasonal variation. Seasonal changes in photosynthetic rate were associated with developmental changes in the crop. Photosynthetic rates were low during early vegetative development, even after the canopy had closed, but increased threefold just before flowering to reach a peak during flowering at stage R2. They then decreased by 30% or more until just before the start of pod expansion (R3) when a 45% increase occurred. Thereafter, photosynthetic rates decreased slowly and continuously to final harvest. The daily curves of photosynthetic rate vs. photosynthetic photon flux density were further analyzed to determine canopy light utilization efficiency (α) and canopy conductance to CO2transfer (τ). Plants grown in 800 µL L−1[CO2] had a value of τthat averaged about 40% higher than that for plants grown in 330 µL L−1and a value of τthat averaged about 24% lower for the season. Differences in α between these treatments were significant throughout the season, while initial differences in τbetween treatments became less obvious after late vegetative growth stage V11.
Soil Fertility Responses of Virginia‐type Peanut Cultivars1
Authors: Coffelt T. A. , Hallock D. L.
Published: July 2010

Differential nutrient contents of peanut (Arachis hypogaeaL.) cultivars in previous studies have demonstrated a need to monitor newly developed cultivars for nutritional peculiarities. Nutrient uptake of large‐seeded, virginia‐type peanut cultivars ‘Florigiant’, ‘Early Bunch’, ‘Virginia 81 Bunch’, ‘NC 7’, and ‘NC 6’ was determined under two fertility treatments (low and high) and two Ca treatments at the high fertility treatment (with and without). The low fertility treatment was 448 kg ha−1of 3–9–18 fertilizer applied to corn (Zea maysL.) prior to peanuts. The high without Ca fertility treatment was 1344 kg ha−1of 3–9–18 fertilizer applied to corn prior to peanuts. In addition, peanuts received 34 kg ha−1Mn, 3.4 kg ha−1Zn and Cu, and 0.6 kg ha−1B prior to planting. The high plus Ca fertility treatment was the same as the high without Ca treatment except 1344 kg ha−1of landplaster was applied to the peanuts at early pegging. The experiment was conducted at Suffolk, VA for 3 yr (1980–1982) on a Wagram loamy fine sand (loamy, siliceous, thermic, Arenic Paleudult). Petioles and leaflets were analyzed for Ca, P, K, Cu, Mg, Mn, Zn, and Fe at early pegging and harvest, and pod yield was determined all 3 yr. Seed germination, seed nutrient content, and market grade were determined in 1981 and 1982. Significant differences occurred among cultivars and fertility treatments for nutrient content of petioles, leaflets, and seeds; yield; market grade; and germination. Leaf tissue contents of Mn, K, and Mg and seed contents of Ca, K, Mg, Fe, Cu, and Zn varied more with fertility treatment than the other nutrients. Leaves of Virginia 81 Bunch (VA 81B) and seed of NC 6 were consistently low in most nutrients, while seed of VA 81B and leaves of NC 6 were not. These results indicate that cultivars differ in nutrient requirement, nutrient uptake, or the redistribution of nutrients. Yield, grade factors, and germination were higher and pod rot lower for the high fertility + Ca treatment than for the other fertility treatments. Simple correlations also showed that the relationship of Ca and K was important in seed germination and the incidence of pod rot.
Aluminum, Citric Acid, Nitrilotriacetic Acid, and Soil Moisture Effects on Aluminum and Iron Concentrations in Ryegrass1
Authors: Muchovej R. M. C. , Allen V. G. , Martens D. C. , Zelazny L. W. , Notter D. R.
Published: July 2010

Seasonal variations in Al and Fe content of pasture forage samples have been generally attributed to soil contamination although mechanisms for plant Al uptake have been suggested. Aluminum and Fe concentrations in annual ryegrass (Lolium multiflorumLam.) grown at two soil moisture levels, flooded and 80% field capacity (FC), with Al added as chelates of citric or nitrilotriacetic acid (NTA) at 0, 33.5 67,100.5, and 134 mg kg−1or chelates added alone, were investigated in a greenhouse experiment. Effects of treatments on soil pH and exchangeable Al were investigated with and without plants present. Plants grown for 10 weeks were harvested at two heights: 6 cm [above 6 cm = upper growth] and ground level (0–6 cm = lower growth). Flooding, chelates, and A1‐chelates increased Al concentrations in plants harvested at both heights. In lower growth, Fe increased only in response to flooding and A1‐NTA. Highest tissue Al concentration occurred with addition of 134 mg Al kg−1as A1‐NTA with values of 850 and 140 mg kg−1in lower and upper growth, flooded, and 480 and 110 mg kg−1in lower and upper growth at 80% FC, respectively. Respective controls contained 410, 67, 133, and 37 mg kg−1Al. Flooding increased soil pH and exchangeable Al. Chelates and Al‐chelates increased soil exchangeable Al. Results show potential for increased plant Al concentrations, particularly under flooded conditions, and suggest chelation with organic acids as an Al uptake mechanism which could affect animal nutrition. For critical determinations, AI should not be used as an indicator of soil contamination in plant samples
Influence of Protective Covers on Reducing Winter Desiccation of Turf1
Authors: Roberts J. M.
Published: July 2010

Loss of turf to desiccation in the later winter and early spring continues to be a major problem especially in northern climates. Reported is a 2‐yr field study to determine the value of synthetic and natural coverings for protection of putting green turf. Studies were made in 2nd and 3rd stand yr on creeping bentgrass (Agrostis palustrisHuds. ‘Emerald’) growing in a Charlton fine sandy loam (coarse‐loamy, mixed, mesic Typic Dystrochrepts). Treatments including spunbonded polyester and polypropylene blankets, sewage sludge, and pine needles were applied in the late fall and compared to a check. Spunbonded polyester blankets weighing 34 to 68 g m2provided the most beneficial results. Compared to the uncovered control, bentgrass grown under the spunbonded polyester blankets generally had 10 to 20% more spring leaf moisture, up to 24% more root length, 80% more clipping(s) and up to 10 °C higher soil temperatures. This hastened the rate of spring turf green‐up by 5 to 12 days. The polypropylene blankets and pine needles also reduced winter desiccation although less consistently. Composted sludge did not. Polypropylene blankets weighing 238 g m2blocked up to 99.5% of the photosynthetically active radiation and caused less desirable color and growth when compared to spunbonded polyester.
Dwarf Bunt of Wheat in China: Potential Sites from Satellite Studies1
Authors: Trione E. J. , Hall M. J.
Published: July 2010

Common bunts of wheat (Triticumspecies) caused by Tilletia caries(DC.) Tul. and T. foetida(Wall.) Liro are present in China, but dwarf bunt has not been reported. Beginning in 1974, wheat shipments from U.S. Pacific Coast states to the People's Republic of China were stopped because they contained spores of the dwarf bunt fungus (Tilletia controversaKuhn), a pathogen affecting winter wheat. This quarantine against T. controversareflected a major Chinese concern that T. controversahad the potential to cause a widespread dwarf bunt epidemic of wheat in China. Thus, the objective of this study was to determine if agricultural lands in China's winter wheat region possessed an important climatic factor (30‐day persistent snow cover) regularly associated with this disease. Weather satellite based NOAA/NESDIS snow and ice charts were used to locate the snow areas occurring on agricultural lands. The agricultural lands were identified using Landsat multispectral scanner imagery. During the period November 1966 through February 1982, 11 instances of persistent snow cover were identified; these occurred in 7 out of the 16 yrs. One area had snow during only 1 yr, four areas had snow during 2 sequential years, and nine areas had snow cover during more than 1 nonsequential yr. Therefore, in China's major winter wheat region the potential sites for the dwarf bunt disease of wheat were rare in time and space, and it appears exceedingly unlikely that a widespread development of this disease could ever occur in China.
Influence of Soil Compaction on Soybean Stand, Yield, and Phytophthora Root Rot Incidence1
Authors: Gray L. E. , Pope R. A.
Published: July 2010

Soil physical factors can influence plant growth and disease incidence. The objective of the present research was to determine if soybean [Glycine max(L.) Merr.] stand establishment and Phytophthoraroot rot incidence were influenced by soil compaction under Illinois growing conditions. Field experiments were conducted for 2 years (1983 and 1984) on a Drummer silty clay loam soil (fine‐silty, mixed mesic Typic Haplaguoll). Plots were compacted once in the spring of each year after the first disking by driving a tractor over the plots. Soil bulk density was increased significantly in both years by tractor compaction. In both years, initial stands and final stands for ‘Corsoy’, (susceptible to Phytophthora megaspermaDrechs. f.sp. glycineaKuan and Erwin) were reduced in the compacted plots. In 1983 there was no effect of soil compaction on initial and final stands for ‘Corsoy 79’ soybeans (resistant to races 1,2,3,6,7,8, and 9 of P. megaspermaf.sp. glycinea) but in 1984 final stands were lower with Corsoy 79 on compacted plots. The number of plants killed by the fungus was significantly increased by soil compaction for Corsoy in both 1983 and 1984. In 1983 there was no difference in seed yield of Corsoy 79 in compacted and noncompacted field plots. In both years the yield of Corsoy was significantly lower in the compacted plots. There was also a significant difference in yield between Corsoy and Corsoy 79 in both years in the compacted plots.
Air and Soil Temperatures during Spring Burning of Standing Wheat Stubble1
Authors: Rasmussen P. E. , Rickman R. W. , Douglas C. L.
Published: July 2010

Winter wheat (Triticum aestivumL.) residues in the Pacific Northwest are often burned even though long‐term detrimental effects on soil properties may ensue. Better weed and disease control are cited as reasons for burning even though results have been highly inconsistent. Inadequate duration of lethal temperature or a nonuniform burn pattern may allow substantial weed, disease, and insect survival. We investigated temperature patterns during burning of 5.0, 6.3, and 6.9 Mg ha−1of wheat residue on March 21 and 6.5 Mg ha−1of residue on May 3. Wheat residue consisted of about 60% standing stubble (350 mm tall) and 40% harvested litter deposited on the surface of a coarse‐silty, mixed, mesic Typic Haploxeroll. Temperature maximum, duration, and variability below, at, and above the soil surface were recorded with copper‐constantan thermocouples. Air temperatures reached a maximum within 30 s after ignition and returned to near‐ambient level within 180 s. Maximum temperatures averaged 301, 416, and 315°C at 25, 75, and 250 mm, respectively, above the soil surface. Burning had no effect on the temperature 25 mm below the soil surface. Neither residue level nor date of burning substantially influenced temperature maximum or duration. Soil surface temperatures during burning were highly variable, seldom exceeding 120°C when the litter‐burn was incomplete, but ranging between 170 and 330°C where litter was completely burned. Substantial occurrence of surface temperatures below 120°C suggests that uniform residue distribution and complete combustion are critical for achieving temperatures capable of destroying weed seeds and disease organisms located on or near the ground.
Sharing the Available Fertilizer Rate between Two Crops in a Limited‐Capital Situation1
Authors: Isfan Daniel
Published: July 2010

Fertilizer recommendations are usually based on the maximum economic rate, which gives the greatest profit per unit area. When the capital is limited, this fertilization rate obviously cannot be applied to all crops. In this case, a method to calculate the most profitable fertilizer rates for each crop is needed. The objective of this work is to develop such a method for nitrogen (N) fertilizer applied in the same year to two different crops or else the same crop in two different crop sequences where the fertilizer needs are not the same. The shared economic rates (SR) of N for crop 1 (S1) and crop 2 (S2) can be calculated with equations and where S1and S2are shared N rates for crop 1 and 2, in kg ha−1; P1and P2are the price of crop 1 and 2, in $ kg−1; A1and A2are the areas planted to crop 1 and 2, in ha; kis the total amount of N available for A1and A2in kg; and b1, b2, c1, and c2are the regression coefficients of the quadratic production functions for crop 1 and 2 (Y= a+ bN+ cN2, where Yis the predicted yield and N the added N, in kg ha−)1).
Gas Exchange of Field‐Grown Soybean under Drought1
Authors: Cortes P. M. , Sinclair T. R.
Published: July 2010

Drought stress has been shown to reduce leaf carbon exchange rates (CER) and to hasten leaf senescence of plants. This study was undertaken to assess concurrently the relative effects of each process on seasonal accumulation of C for soybean [Glycine max(L.) Merr.| grown under field conditions. Leaflet CER and water vapor exchange rates were measured continuously during drought stress treatments of two indeterminate cultivars. The cultivars differed in maturity with ‘Wilkin’ being in maturity group 0 and ‘SRF 150’ being maturity group I. Gas exchange measurements were made using an open system with assimilation chambers enclosing uppermost fully expanded leaflets. Data were recorded concurrently every 12 min for leaflets attached to plants in an irrigated treatment and in treatments drought stressed at differing stages of reproductive growth. As a result of drought during reproductive growth, CER of both cultivars was reduced by approximately 25% for the remainder of the season. Drought during flowering to mid‐podfill did not seem to hasten leaf senescence in either cultivar. However, drought after mid‐podfill resulted in a 5 to 10 day earlier leaf senescence of these leaves at the top nodes of the plants. These data suggest that reduced CER for the remainder of the season was a consistent consequence of drought stress during reproductive growth. Hastened leaf senescence could further reduce total accumulated C if drought occurred late in reproductive growth.
Phosphorus‐induced Zinc Deficiency in Wheat on Residual Phosphorus Plots1
Authors: Singh J. P. , Karamanos R. E. , Stewart J. W. B.
Published: July 2010

One‐time heavy application of P on certain soils can provide sufficient available P to sustain crop production over a period of several years, but may cause Zn nutritional problem for crops. A field study was conducted to determine the effect of applied Zn on wheat (Triticum aestivum L.) grown on residual P plots and identify the mechanism of P ✕ Zn interaction. This study was conducted in 1984 in a continuous wheat system on a clayey, mixed, frigid Typic Hyploboroll soil that had received 0, 80, and 160 kg P ha−1 in 1979. Three experiments were carried out using a split plot randomized complete block design with three levels of P as main plots and rates of soilapplied Zn‐sulfate (0, 5, 10, and 20 kg Zn ha−1) or Zn‐chelate (0, 0.5, 1.0, and 2.0 kg Zn ha−1) or foliar‐applied Zn‐chelate (0 and 0.35 kg Zn ha−1) as subplots. A one‐time application of 80 or 160 kg P ha−1 increased wheat yield significantly. In the presence of P, application of Zn resulted in significant increase in grain yield and Zn uptake into grain. Applied P increased soil P levels and tissue P concentration, but resulted in a significant decrease of tissue Zn levels. DTPA (diethylenetriaminepentaacetic acid)–extractable soil Zn levels in the non–Zn‐amended treatment were independent of P application rate. Plant roots in high P treatments contained significantly lower levels of vesicular‐arbuscular mycorrhizal (VAM) infection than the control. Further, a close relationship was observed between Zn levels in the aboveground plant parts and VAM infection.
Ground Cover and Weathering Effects on Reflectances of Three Crop Residues1
Authors: Wanjura D. F. , Bilbro J. D.
Published: July 2010

Crop residue, which is important in protecting soil from wind and water erosion, is not easily differentiated from bare soil and difficult to quantify using remote sensing techniques. A field study was conducted on Amarillo fine sandy loam (Aridic Paleustalfs) for the purpose of measuring the change in spectral reflectance due to varying concentrations and weathering of Texas panicum (Panicum texanum Buckl.) pearl millet [Pennisetum americanum (L.) K. Schum], and cotton (Gossypium hirsutum L.) bur residue. Reflectance was measured in seven wavelength intervals with a multiband radiometer (MMR). The greatest change in reflectance occurred between bare soil and 33% ground cover. Band MMR 2 gave the best separation between the crop residues. The MMR bands 1, 2, and 3 provided the best discrimination among fresh residue types; however, as weathering progressed after 240 mm of rainfall, reflectance in bands MMR 5, 6, and 7 was significantly different among residues. The ratio of MMR 5 divided by MMR 6 was < 1.0 for fresh crop residues compared with values > 1.0 after exposure to a 240‐mm rainfall. The largest relative change in reflectance during the weathering period among residues in decreasing order was pearl millet, Texas panicum, and cotton burs. Band MMR 4 showed the greatest relative reflectance change during 251 days of weathering. Detecting crop residue on bare soil with remote sensing techniques may be feasible if it is known whether the residue is fresh or weathered.
Continuous Flow System for Collecting Volatile Ammonia and Amines from Senescing Winter Wheat1
Authors: O'Deen W. A. , Porter L. K.
Published: July 2010

Evolution of ammonia and amines from wheat‐media systems following anthesis has previously been observed with chambers that have been either closed or open, but lacking in low ultimate relative humidity. Few systems have isolated the aerial parts of the wheat (Triticum aestivum L.) from its growth medium. Therefore, a freeflow open system was designed that isolated the aerial wheat from its growth medium and obtained low ultimate relative humidities of 10 to 20%. Surfaces of 0.1 M HCl were used to trap the ammonia and amines both inside and outside the chamber, increasing the efficiency of collection. Potted winter wheat was heavily fertilized with five additions of 50 mg N kg−1 soil and watered to near field capacity as required. Emission of volatile bases yielded a sensitive double‐peaked senescent N band. The 90‐day average plant emission of 1.8 mg N m−2 day−1 represented a crop loss of 1.6 kg N ha−1 and 3.1% of the total N in the plant material contained in the chamber.
Techniques for Measuring Intercepted and Absorbed Photosynthetically Active Radiation in Corn Canopies1
Authors: Gallo K. P. , Daughtry C. S. T.
Published: July 2010

A portable system that would enable rapid measurement of photosynthetically active radiation (PAR) would be useful in studies that include measurements of interception and absorption of PAR in crop canopies. The objectives of this study were to develop and evaluate a portable system for measuring intercepted and absorbed PAR in corn (Zea mays L.) canopies. This study consisted of two field experiments with corn planted in north‐south rows at two densities with two planting dates in each of 2 yr. The soil was a dark (10YR 4/1) Chalmers silt loam (Typic Argiaquoll). A handle, two levels, and a data logger were added to a line quantum sensor to form a portable system for rapidly measuring the ascending and descending fluxes associated with absorbed PAR (APAR). The effects of sensor orientation and surface length on measurement of transmitted PAR and the errors induced by use of intercepted PAR as an estimate of absorbed PAR were examined. Transmitted PAR (TPAR) was optimally measured with the sensor leveled and positioned perpendicular to the row direction with the length of the sensor equal to the row spacing. Intercepted PAR (IPAR), the difference in descending PAR fluxes above and below the canopy, required fewer measurements than APAR and differed from APAR by the difference between canopy and soil surface reflectances. Prior to the dent stage (R5) of grain maturity, differences between APAR and IPAR were less than 3.5% for this study. Thus IPAR was a reasonable approximation of APAR and required fewer measurements.
Winter Survival Response of Winter Wheat: Tillage and Cultivar Selection1
Authors: Cox D. J. , Larsen J. K. , Brun L. J.
Published: July 2010

Winter wheat (Triticum aestivum L.) production in the Northern Great Plains is dependent upon adequate survival of the crown tissue for regeneration of root and shoot in early spring. Thus, the establishment of winter wheat as a viable alternative crop in North Dakota has been dependent upon the use of management practices that enhance winter survival. Objectives of this study were (i) to verify previous results associating winter injury or lack of with tillage and its associated effects on snow depth and soil temperature, and (ii) to determine the affect of tillage and cultivar selection on grain yield in an environment where winter injury frequently is experienced. Two hard red winter wheat cultivars were planted during the fall of 1981 and 1982 into conventional tillage (CT), mulch tillage (MT), and notillage (NT) plots on a Fargo clay (fine, montmorillonitic, frigid Vertic Haplaquoll) located at Fargo, ND. The experiment was repeated during the winters of 1983–1984 and 1984–1985 using MT, and short (0.05 m) and tall (0.20 m) stubble NT plots. Snow depth was greatest in conjunction with tall stubble (0.20 m) and resulted in warmer soil temperatures and a reduction in the duration of time temperatures dropped within the range responsible for winter injury. Winter injury was recorded only for the winters of 1981–1982 and 1984–1985. Percentage winter survival was greatest for NT wheat planted into tall stubble. The survival of MT wheat was intermediate between that of CT and NT wheat. The snow trapping ability of short stubble (0.05 m) and amount of winter injury recorded was similar to that for MT. The mean grain yield of CT, MT, and NT (both 0.05 and 0.20 m) wheat was 455, 2203, 2270 and 4073 kg ha−1 respectively, for the two winters in which winter injury was recorded. There were no significant differences in yield harvested from tillage treatments for the two mild winters. Tillage selection (CT vs. NT) was more important in explaining the variation in percentage winter survival than was cultivar selection.
Yield and Regrowth Characteristics of Alfalfa Grazed with Sheep. II. Summer Grazing1
Authors: Allen V. G. , Hamilton L. A. , Wolf D. D. , Fontenot J. P. , Terrill T. H. , Notter D. R.
Published: July 2010

Grazing alfalfa (Medicago sativa L.) in summer would provide high quality forage during periods of low rainfall when other forages are in short supply. ‘Arc’ alfalfa, grown on fine‐loamy, mixed, mesic Fluventic Dystrochrept at Blacksburg, VA, was grazed by sheep following two hay cuts in 1982 and 1983 with six treatments: (i) no grazing with hay being cut at 1/10 bloom; (ii), (iii), and (iv) grazing began approximately 14 days after second hay cut and continued for 2, 4, and 6 weeks, respectively; (v) grazing began at early bud stage and continued for 10 days in 1982 and 7 days in 1983; and (vi) grazing began at early bloom and continued for 7 days. Following grazing, hay was cut on each treatment if regrowth reached 1/10 bloom stage before killing frost. No grazing was imposed in 1984 and hay was harvested three times from plots from all six treatments. Forage remaining after grazing for 2, 4, or 6 weeks was higher in percent leaf, in vitro dry matter digestibility, crude protein, Ca, Mg, and P concentration, and was lower in cell wall constituents than after grazing at early bud or bloom. Grazing for 4 and 6 weeks precluded fall hay harvest and increased weeds. Alfalfa yield in 1984 was reduced by grazing except grazing at early bloom. Yield was 8.5, 7.3, 7.1, 6.7, 7.3, and 8.7 Mg ha−1 for the six treatments, respectively. Weed encroachment generally increased with increased grazing duration (GD). Grazing could decrease productivity, especially as GD is lengthened, but may be less detrimental than previously supposed.
Grazing Duration Effects on Wheat Growth and Grain Yield1
Authors: Winter S. R. , Thompson E. K.
Published: July 2010

Winter wheat (Triticum aestivum L.) is frequently grazed from November until March in the Southern Great Plains. The effects of grazing on growth and grain yield are not clearly understood. Irrigated grazing trials were conducted on Pullman clay loam, a fine, mixed, thermic Torrertic Paleustolls soil, to determine the growth and grain yield responses of a semidwarf winter wheat cultivar (TAM 105) planted in late August using five dates of grazing termination in the spring. An ungrazed (grain‐only) treatment that was planted in early October and managed for high grain yield was included for reference. Wheat forage was removed to a 50‐ to 70‐mm stubble height (15 to 30% ground cover) by stocker cattle (Bos taurus L.). Growing conditions were good, and heading dates averaged near normal. Growth and grain yield responses to grazing duration were basically the same for all growing seasons. Three‐year‐average grain yields were 4.79,4.79,4.29,3.70,3.20, and 2.40 Mg ha−1 dry weight for grain‐only, 1 February, 6 March, 17 March, 31 March, and 13 April grazing termination dates, respectively. The wheat grazed until 1 February had reduced leaf area index (LAI), biomass, mean tiller weight, height, and single‐seed weight; but grain yield, tiller density at heading, and harvest index were not reduced when compared to the grain‐only wheat. Grazing until 6 March or later progressively reduced LAI, biomass, tiller weight, height, and single‐seed weight. Heading was delayed by late grazing. Tiller density and harvest index were not reduced unless grazing continued past 31 March and 17 March, respectively. Grazing until 6 March or later appeared to reduce grain yield by limiting LAI and biomass in the spring. Since grain yield was reduced even by grazing until 6 March and the wheat did not reach Feeke's stage 6 until about 1 April, removal of spikes by grazing cattle can not be a primary cause of the loss in wheat grain yield. It was observed that grazing past the period of initial elongation of the first internode delayed internode elongation. This delay in reproductive development caused by continued grazing will need to be considered if grazing termination decisions are based on stage of development.
Environmental × Genotype Effects on Seed Dormancy and After‐Ripening in Wheat1
Authors: Hagemann M. G. , Ciha A. J.
Published: July 2010

The length of the after‐ripening period (ARP) for winter wheat (Triticum aestivum L.) in the Pacific Northwest of the United States is very important. If the ARP is too long, fall planted seeds will not germinate uniformly, resulting in poor stands; preharvest sprouting may occur if the ARP is too short. The objective of this study was to examine the influence of cultivar and temperature during grain fill on the level of seed dormancy during ARP. Three winter wheat cultivars differing in susceptibility to preharvest sprouting were grown in five environments with varying rainfall and temperature conditions during grain fill. Grains were harvested at harvest ripeness and stored at −10, 10, 20, and 30°C during an 8‐week ARP. The level of seed dormancy was calculated using germination index and percent germination values determined at harvest ripeness and after an 8‐week ARP. Seed dormancy at harvest ripeness was a function of cultivar and environment during grain development. Loss of seed dormancy during after‐ripening was a function of the cultivar, the environment in which the grain developed, and the after‐ripening environment. Grains that developed in cool environments generally lost their dormancy more rapidly than grains that developed in warm environments. High temperatures during the ARP generally accelerated the loss of seed dormancy. One of the cultivars with low dormancy at harvest ripeness expressed higher levels of seed dormancy when stored at –10°C for 8 weeks than when it developed under certain field conditions. Environmental conditions typical of the Pacific Northwest, cool temperatures during grain development followed by high temperatures after harvest ripeness of the seed, are conducive to rapid loss of seed dormancy, which may lead to severe preharvest sprouting if grain harvest is delayed.