bluuebunny/crossref_metadata_2025 huggingface dataset:
Ammonium‐N and Nitrate‐N Effects on the Growth and Mineral Compositions of Triticale, Wheat, and Rye1
Authors: Gashaw L. , Mugwira L. M.
Published: July 2010

Absorption and utilization of N has been shown to be affected by the N form supplied and cultivar used. The relative absorption and utilization of NH4+−N and NO3−−N by triticale (X Triticosecale, Wittmack), wheat (Triticum aestivum L.), and rye (Secale cereale L.) have not been determined. This study was conducted to determine the growth and mineral composition of triticale 6TA 131, ‘Arthur’ wheat, and ‘Abruzzi’ rye grown in nutrient solutions containing different NH4+−N/N03−−N ratios in a growth chamber. The NH4+−N/NO3−−N ratios were 0/100, 25/75, 50/50, 75/25, and 100/0. Solutions were sampled every 10 days during a 30‐day plant growth period. Triticale and rye more preferentially absorbed N03−−N over NH4+−N than wheat which sometimes (50/50) absorbed more NO3 than NH4. All species produced higher dry matter with the combinations of 25/75, 50/50, and 75‐25 NH4+−N/NO3−−N ratios than with either N source alone. There were increases in the uptake of N, P, and Fe when NH4+−N/NO3−−N ratio was increased in the mixture whereas NO3−−N increased the uptake of Mg, Ca, Mn, and NO3−−N. These results suggested that the triticale inherited its absorption efficiency of NO3− from rye.
Mechanical Impedance Effects on Oxygen Uptake and Porosity of Drybean Roots1
Authors: Schumacher T. E. , Smucker A. J. M.
Published: July 2010

Low oxygen concentrations and mechanical impedance are two components of soil compaction often implicated in the reduction of crop yields. The relative importance of these two stresses to the root system has not been thoroughly assessed. A system was developed to study the effect of mechanical impedance on root respiration and morphology. Oxygen uptake, by intact plant root systems subjected to three levels of mechanical impedance, was determined polarographically by measuring the oxygen concentration of nutrient solutions before and after flowing through a root media of 1 mm, 3 mm, or no glass beads. Oxygen uptake rates by drybean (Phaseolus vulgaris L.) roots were independent of solution flow rates ≥ 6.0 ml/min‐1 when inlet pO2 was 0.21 atm. Mechanical impedance reduced dry weight, fresh weight, volume, and length of roots after 8 days of treatment. Dry matter percentage of mechanically impeded roots was greater than the control. Roots subjected to mechanical impedance were deformed, branched more frequently, less porous, and consumed more oxygen per unit fresh weight. It is suggested that a greater oxygen supply may be required at the root surface to prevent anoxia in mechanically impeded roots.
Allelopathic Effects of Tall Fescue Genotypes1
Authors: Peters E. J. , Mohammed Zam A. H. B.
Published: July 2010

Tall fescue (Festuca arundinacea Schreb.) has been shown to have allelopathic effects on some species. Some tall fescue genotypes growing in a breeding nursery had large crabgrass [Digitaria sanguinalis (L.) Scop.] infestations while other genotypes had none. The difference in infestations did not appear to be due to competition; therefore, the possibilities of allelopathic effects were investigated. The surface 2.5 cm of soil in which the various tall fescue genotypes were growing was placed in pots in the greenhouse. The crabgrass germination in the greenhouse varied with genotypes in a manner similar to what had been observed in the field. Genotypes were evaluated for allelopathic effects by germinating seeds of birdsfoot trefoil (Lotus corniculatus L.) and medium red clover (Trifolium pratense L.) in petri dishes containing extracts made by soaking 10 g of tall fescue leaves in 100 ml of water for 24 hours. After 10 days, germination of the legume seeds was significantly inhibited by fescue extracts as compared with distilled water. After 14 days, one tall fescue genotypes had significantly less germination of birdsfoot trefoil seed than did three other genotypes, while one genotype had significantly less germination of red clover seed than did one other genotype.

Birdsfoot trefoil and red clover seedlings were grown in half‐strength Hoagland's solution containing extracts of three tall fescue genotypes made by soaking 3, 5, and 10 g of tall fescue tissue for 24 hours in distilled water. Roots of birdsfoot trefoil were significantly inhibited by the 10‐g concentration as compared with the 3‐g concentration in two out of three genotypes. The 10 gm concentration of one genotype significantly inhibited shoot growth of birdsfoot trefoil as compared with the 3‐ and 5‐g concentrations. Shoot and root growth of red clover were significantly inhibited by all extracts of tall fescue genotypes. In extracts of two out of three genotypes, the 10‐g concentration significantly reduced the top growth of red clover. Soils on which three fescue genotypes had been grown were incubated in the greenhouse for 0, 1, and 2 weeks and birdsfoot trefoil seedlings were planted into them and in soil that was not exposed to tall fescue. Root and shoot growth of birdsfoot trefoil seedlings was significantly inhibited when grown in soils in which fescue genotypes had been grown, but incubation periods of the soil had no effects. In soil from one genotype, root and shoot growth of red clover were significantly inhibited when unincubated and inhibition decreased when the soil had been incubated for 2 weeks. In soil from another genotype, root and shoot growth of red clover were significantly inhibited in all incubated soils as compared with the check soil. In soil from the third genotype, root and shoot growth of red clover were inhibited at all incubation periods, but inhibition of shoot growth was greater in soil incubated for 2 weeks as compared with 0 weeks.
Soil and Management Factors Correlated With Soybean Yields in Southeastern U.S. Coastal Plain1
Authors: Reich R. C. , Kamprath E. J. , Nelson L. A.
Published: July 2010

A field survey of 220 soybean (Glycine max (L.) Merr.) plots was conducted over a 2‐year period on mineral soils in 12 major soybean producing countries in the Coastal Plain of North Carolina. The objectives of this investigation were to study the effects of certain soil and management factors in soybean production and to develop statistical models for explaining variations in soybean grain yields.

Multiple regression and correlation statistical techniques were used to analyze the data. Many factors were highly intercorrelated reflecting the very complex nature of the crop‐soil system. No one factor was found to explain a large proportion of the variation in soybean production but multiple regression models were developed for both years which accounted for 71 to 86% of the variation in yield. Extractable Ca and Al saturation, which reflected past liming practices, were soil chemical properties correlated with grain yield. Physical properties related to available water were also correlated with yield. Management factors such as trips across the field before planting, planting date, crop preceding soybeans, and number of years since liming also influenced soybean yields. Multiple regression analysis indicated that soil pH and number of trips across the field were two important factors affecting yield each year.
Growth Response of Alfalfa to Duration of Soil Flooding and to Temperature
Authors: Thompson Todd E. , Fick Gary W.
Published: July 2010

Alfalfa (Medicago sativa L.) is very sensitive to excessive soil water, yet few studies have been done under controlled conditions to quantify the extent of this sensitivity. The objective of these studies was to investigate the effect of wet soil conditions on alfalfa production. The growth of roots and tops was determined in a factorial greenhouse and growth chamber experiment with treatments for duration of flooding and temperature. Five‐week‐old alfalfa plants, potted in pasteurized soil, were flooded to the soil surface for 4, 8, 12, 16, and 20 days at temperatures of 16, 21, and 27 C, and for 3, 6, 9, and 12 days at 32 C. Root and top dry weights (DW) of flooded and control plants were measured upon draining. Three weeks after draining, the plants were cut to a 2.5 cm stubble and top DW was measured. After 2 subsequent weeks of regrowth, top and root DW's were again measured.

Results demonstrated that root growth stopped during flooding. As measured over the 3 weeks following drainage, the rate of top growth of plants was reduced by 50% with 8 days of flooding at 16 C, 4 days at 21 C, 3 days at 27 C, and 2 days at 32 C. No net top growth occurred during the 3 weeks following drainage in plants flooded for over 14 days at 16 C, 10 days at 21 C, 8 days at 27 C, and 6 days at 32 C. In most cases, the negative response to flooding occurred before the disease Phytophthora megasperma Drechs. is thought to have been able to have an influence. This argues for a physiological as opposed to a pathological basis for the injury.
Foliar Fertilization of Rice After Midseason1
Authors: Thom W. O. , Miller T. C. , Bowman D. H.
Published: July 2010

Foliar fertilization of rice (Oryza saliva L.) with solutions containing N, NPK, and NPKS during reproduction promises to increase yields and affect grain composition. These foliar applications could avoid N depletion as soil N is the major source for late season uptake. To test this hypothesis field experiments were conducted for 3 years with solutions applied at and/or after panicle initiation (2‐mm panicle) in different proportions, and at different rates and times. Applications of N (157 kg/ha) on the soil prior to flooding (preflood) increased yields, ranging from 771 to 2,370 kg/ha, over the no N check but did not affect composition of brown rice. Increases (0.13 to 0.75%) in N concentration of brown rice were associated with foliar applied N of 50 kg/ha or greater, with or without P+K+S at mid‐boot (12‐ to 15‐cm panicle internodes) stage. Split application (panicle initiation and mid‐boot) increased N concentration more than when the total amount of nutrients were applied in one application (panicle initiation). The first or early applications (mid‐boot — 1976; panicle initiation — 1977 and 1978) were effective in increasing yields and the later applications (post flower — 1976; mid‐boot — 1977 and 1978) were more effective at increasing N concentration in brown rice. Differences in P, K, and Zn in brown rice were not related to timing or amount of foliar nutrients applied. Calcium and Mg in brown rice were unaffected.

The results indicate that foliar fertilization of rice with solutions high in N at or after panicle initiation can increase yields. A split application can increase yields and N concentration in brown rice.
Effects of Light Intensity on Growth of Some Tropical Forage Species. I. Interaction of Light Intensity and Nitrogen Fertilization on Six Forage Grasses1
Authors: Eriksen F. I. , Whitney A. S.
Published: July 2010

In order to determine the response of some tropical grass species to low light situations such as under plantation crops, seasonal cloud cover, etc., six tropical forage grasses were evaluated over a 20 month period on an Oxic Haplustoll in Hawaii (100 m above sea level) under four light regimes (100, 70, 45, and 27% daylight using polypropylene netting) in the field.

The forage grasses evaluated were: Brachiaria brizantha, B. miliifirmis, Digitaria decumbent, Panicum maximum, Pennisetum clandestinum, and P. purpureum. Dry matter yields of N‐fertilized (365 kg N ha−1 yr−1) grasses were highest at 100 and 70% daylight (16 to 40 metric tons of dry matter (DM) ha−1 yr−1), with P. maximum and P. purpureum having highest yields. Under 27% daylight, yields were 8 to 15 tons, with P. maximum, B. brizantha, and B. miliiformis having highest yields. When no N was added maximum yields in tons ha−1 yr−1 were B. miliiformis, 9.2 at 27% daylight; D. decumbens, P. maximum, and B. brizantha, 13.5 to 15.0 at 45% daylight; and P. clandestinum, 9.2 at 70% daylight. P. purpureum without N yielded 30 tons at full daylight, apparently because its very extensive root system invaded adjacent N‐fertilized plots. Percentage of DM in the forage decreased with shading and N fertilization. Percent N increased with decreasing light intensity (from 1.0 to 1.6% hi the minus‐N and from 1.2 to 1.9% hi the plus‐N treatments). Slight acetylene reduction activity was found in soil cores beneath all species, except B. brizantha, indicating that the plants were almost entirely dependent on soil and fertilizer N for growth. Sward height increased significantly with decreasing light intensity and N fertilization. Concentrations of P, K, Ca, Mg, S, Cu, and Zn tended to be higher in shaded forage, higher in N‐fertilized forage (except for P and Zn), and generally higher during the cool season.

Thus under N‐deficient conditions, most yield and forage quality parameters were enhanced under moderate shade. Conversely, the tropical grasses studied generally responded to N fertilization only under conditions of moderate to high solar radiation.

Root weight data and observations on the rate of recovery after clipping indicate the shaded pastures would require careful management to avoid excessive depletion of root reserves, either by lenient grazing to maintain high leaf areas or by allowing an extended recovery period.
Tall Fescue and Smooth Bromegrass. II. Effects of Nitrogen Fertilization and Irrigation Regimes on Quality1
Authors: Eck H. V. , Wilson G. C. , Martinez Tito
Published: July 2010

Both quantity and quality must be considered in selecting forages for livestock. This study was conducted to determine effects of N and irrigation treatments on the quality of tall fescue (Festuca arundinacea Schreb.) and smooth bromegrass (Bromus inermis Leyss.) forage in the Southern High Plains. ‘Fawn’ tall fescue and ‘Southland’ smooth bromegrass were grown on Pullman clay loam (fine, mixed thermic, Torrertic Paleustoll) under N rates of 0, 168, 336, 504, and 672 kg ha‐1 year‐1 on three water regimes: W‐l, a moderate (about 50‐cm) and W‐2, an adequate (about 100‐cm) irrigation water level, both distributed for season‐long production, and W‐3, a moderate (about 60‐cm) irrigation level distributed for cool‐season forage production. Forage was harvested and analyzed for N, P, K, Ca, Mg, NO3‐ and in vitro dry matter disappearance (IVDMD). Nitrogen fertilization increased N, K, and NO3‐‐N in both forages. The increased K levels increased the K/(Ca + Mg) ratios. Less marked effects of N included slight increases in IVDMD in both grasses, increases in Ca and Mg, and decreases in P in tall fescue but not in smooth bromegrass forage. The total N and NO3‐‐N were lower and the Ca and Mg were higher in forage from W‐2 than in that from W‐l and W‐3. With N rates through 336 kg/ha, NO3‐‐N remained below the 2,000‐ppm level considered harmful to livestock. Forage P and IVDMD were not affected by differences in irrigation. Although smooth bromegrass was superior to tall fescue in N, K, and Ca concentrations and in IVDMD, N fertilization at levels high enough to produce satisfactory yields increased the K/(Ca + Mg) ratios to levels considered critical for induction of grass tetany. With pure stands of smooth bromegrass, supplemental feeding of Mg would be necessary. Tall fescue contained more Mg than did smooth bromegrass, and its K/(Ca + Mg) ratios were favorable. Without P fertilization, feeding supplemental P would be necessary with both forages. Surface‐applied feedlot waste, at N rates equivalent to those applied as NH4NO3, was less than one‐half as efficient as NH4NO3 in increasing N to forage, but it increased P to levels satisfactory for nutrition of mature cows. Both irrigation adequacy and grass species must be considered in fertilizing for maximum production of high quality forage.
Interactions between Forage Sorghum Cultivars and Defoliation Managements1
Authors: Creel Rodney J. , Fribourg Henry A.
Published: July 2010

Yield and plant constituent responses of forage sorghum (Sorghum bicolor (L.) Moench) cultivars have usually been compared in uniform defoliation management tests. However, the influence of time of harvest and stubble height on differential response of cultivars needs more precise definition. The extent of cultivar × management interaction was studied for ‘Sweet Sioux III’3 (a leafy high‐producing cultivar similar to many others available), ‘FS‐531’ (a silage‐forage cultivar) and ‘Super‐Chowmaker 235’ (several weeks later in maturity than most other forage sorghum cultivars) for 2 years. The soil was a Sequatchie sandy loam (fine‐loamy, siliceous, thermic Humic Hapludults). Stubble height and defoliation managements designed to simulate grazing, greenchop, hay or silage harvests, in various combinations, were used with each cultivar. Chowmaker plants yielded more, had the same or higher N percent, and the same in vitro dry matter digestibility (IVDMD) when cut to a 15‐cm than when cut to an 8‐cm stubble. Sweet Sioux plants yielded more when cut back to 8 cm than to 15 cm, but their N percent and IVDMD were not affected by stubble height. Cutting when forage reached 50 cm previous to the boot (B) or early bloom (EB) cuts delayed subsequent development, and hence harvest, of FS‐531. The other two cultivars reached the B or EB stages at the same time, regardless of whether that harvest was preceded by a prior harvest or not, but the B or EB stages occurred at shorter heights if preceded by a harvest. Harvesting when forage reached 90 cm before the B or EB cut delayed harvest for all cultivars, probably because all regrowth had to originate from axillary meristems. The delay in B or EB harvests may be beneficial in situations where dry matter production later in the season is more desirable. The results suggested that, if the three different cultivars used here had been entered in a yield trial where all entries were managed uniformly, the information on the potential performance of these forage sorghum cultivars could have been misleading. Harvests at early stages of growth would have penalized Super‐Chowmaker 235 in comparison to Sweet Sioux III, and the reverse would have occurred if later stages of growth had been used to determine harvest time.
Effects of Soil Water on Rhizobium japonicum Infection, Nitrogen Accumulation, and Yield in Bragg Soybeans1
Authors: Hunt P. G. , Wollum A. G. , Matheny T. A.
Published: July 2010

Low soil water contents may be involved in the lack of success of soybean inoculation in southeastern U.S. soils having high indigenous populations of Rhizobium japonicum. This study was conducted to assess the effect of soil water on the inoculation, biomass, N accumulation, and yield of soybean [Glycine max (L.) Merr.]. ‘Bragg’ soybeans were inoculated with 108 cells/cm row of R. japonicum (strain 110) and grown under both irrigated and nonirrigated conditions on a Norfolk loamy sand (Typic Paleudult) in a split plot design. Rainfall maintained the surface soil above −250 mb matric potential until the late flowering stage of growth. Subsequently, a seasonal drought created treatment differences between irrigated and nonirrigated plots resulting in a twofold increase in seed yield due to irrigation (3,160 vs. 1,682 kg/ha). Inoculation increased the percentage infection by strain 110 from practically 0% background to about 20%. Inoculation increased growth and total N accumulation in pods, petioles, and leaves of Bragg soybeans under irrigated conditions. Under nonirrigated conditions, the increased infection of strain 110 appeared to induced a negative response in the vegetative growth of Bragg soybeans. Nitrogen concentration was also significantly lower in the leaves and pods of nonirrigatedinoculated plants. These differences were not observed in N content of the mature seed, and inoculation did not significantly affect seed yield. These findings indicate that R. japonicum strain ✕ environment interactions may be important for soybean growth and yield in the southeast United States.
A Visual Indicator of Physiological Maturity in Soybean Plants1
Authors: TeKrony D. M. , Egli D. B. , Henson G.
Published: July 2010

Physiological maturity (PM) represents an important growth stage of crop plants, since it is normally associated with maximum accumulation of dry seed weight and yield. Physiological maturity of an individual soybean (Glycine max (L.) Merrill) seed or pod occurs when the seed or pod is completely yellow; however, indicators of PM on a whole plant basis are not available. This investigation was conducted to relate several visual indicators of soybean pod development to PM and yield of field populations. Plants of three cultivars (‘Williams’, ‘Kent’, and ‘Essex’) were grown in a Maury silt loam soil (Typic Paleudalfs, fine, mixed, mesic) in 1977 and 1978 and harvested when 50% of the population had reached or exceeded the following growth stages: 1) a completely expanded green pod at one or more of the four uppermost nodes, 2) one yellow pod per plant, and 3) one normal pod on the main stem that has reached its mature pod color (growth stage R7). A check harvest was made after full maturity. In 1979, seven cultivars representing maturity groups OO to V and both determinant and indeterminate growth habits were grown in the same soil type and harvested at growth stage R7 and at full maturity.

Plants harvested at the green pod growth stage exhibited significantly smaller seed and lower yield compared to those harvested at full maturity. Even though there was no significant reduction in seed size and yield for plants harvested at the yellow pod growth stage, in 1978 there was a consistent trend across cultivars for lower yields at this harvest. There was no reduction in seed size or yield for plants harvested at growth stage R7 in all 3 years compared to harvests at full maturity. Growth stage R7 (one mature pod per plant) was a more accurate indicator of PM than the yellow pod growth stage (one yellow pod per plant), since a greater percentage of pods (64%) and seed (55%) had reached or exceeded complete yellow coloration indicating that those pods and seed were physiologically mature. The appearance of one normal pod on the main stem that has reached its mature pod color (growth stage R7) represents an accurate, easy to recognize visual indicator of PM. This criteria should provide farmers, researchers, and others with a useful tool for determining PM for a single plant or a field population.
Recoverability of Cotton Following Simulated Hail Damage1
Authors: Smith C. Wayne , Varvil J. J.
Published: July 2010

Many areas of the so‐called cotton belt frequently receive hail sufficient to cause measurable damage to cotton (Gossypium hirsutum L.). The indeterminant growth habit of cotton allows for varying degrees of recoverability from hail damage depending upon the stage of growth of the plants when damaged and the severity of damage.

Research was initiated in 1977 to evaluate the recoverability of cotton from simulated hail damage. These tests were conducted at three locations in Arkansas representing several silt loam soils with one site being severely infested with verticillium wilt [Verticillium albo‐atrum (Reinke and Berth)].

Upon developing the 4th, 7th, and 10th true leaves, plants were hand cut to immediately above the cotyledonary node (CC type damage) or immediately above the second true leaf node (C2). At the Marianna location only, plants with 10, 12, and 14 true leaves also were damaged (C5 and C7) to assess recoverability of plants just prior to flowering, approximately at flowering, and just after flowering. The field design was a randomized complete block with four replications of plots 12 to 15 m in length.

The degree of recoverability decreased as the severity of damage increased or as the same damage was applied to older plants. Plants infested with Verticillium wilt did not recover from simulated hail damage as well as plants at the other two locations indicating an accumulative effect of yield limiting stresses. Stepwise regression analysis indicated that 79% of the variability in seedcotton yields following the early season treatments could be accounted for by the number of nodes removed and the stage of plant development at the time of injury. Recoverability of plants damaged when near flowering could not be predicted by the number of nodes removed and/or stage of growth. Quality characteristics of the fiber were affected little.
Influence of Windbreak‐shelter on Soybean Production under Rainfed Conditions1
Authors: Ogbuehi S. N. , Brandle J. R.
Published: July 2010

Research indicates that a combination of windbreak and irrigation gives significant soybean yield increases in comparison to an irrigated open field. Little data is available to determine the yield advantage of soybean production under sheltered and rainfed conditions. The field study reported here was conducted at the University of Nebraska Field Laboratory, Mead, Nebraska, during 1978 and 1979 growing seasons to determine the influence of windbreak‐shelter on soil water content and soybean [Glycine max (L.) Merr.] yield under rainfed conditions. Shelter from wind was provided by a system of east‐west oriented shelterbelts, 6 m high, 60% dense, and consisting of green ash (Fraxinus pennsylvanica L.), Austrian pine (Pinus nigra Arnold), and eastern red cedar (Juniperus virginiana L.). The prevailing winds in Nebraska during the summer months come mainly from the south. The soil was a Typic Argiudoll.

There were no statistically significant differences (P = 0.05) between treatments in available soil water and plant water use. In spite of this, sheltered soybeans had higher leaf water potential and stomatal conductance, and lower leaf temperature. These differences between treatments were attributable, entirely, to shelter‐induced modification of the growing season microclimate. Leaf area index, dry matter production, and bean yield were significantly increased in shelter during both years. Bean yield in shelter was 20 and 26% higher than in exposed plots in 1978 and 1979, respectively. Bean production per ha‐cm of water used in 1979 was 58 kg for sheltered soybeans and 47 kg for those in exposed plots

Results of this study indicated that under rainfed conditions, increased water‐use efficiency, and significant increases in bean yield can be expected from sheltered soybeans.
Canopy Temperatures, Water Use, and Water Use Efficiency of Corn Genotypes1
Authors: Mtui T. A. , Kanemasu E. T. , Wassom C.
Published: July 2010

It is desirable to describe and characterize physiological properties of corn (Zea mays L.) genotypes that will permit a basis for selecting genotypes. The objective of this field study was to compare two hybrids (Mo17 ✕ B73, A619 ✕ A632) and their respective inbred parents under irrigated and nonirrigated conditions. Measurements of canopy temperature, stomatal diffusive resistance, xylem water potential, leaf area index, ear dry weight, and grain yield were determined. Water use was determined from neutron moderation measurements of the soil‐water profile. The soil was a fine silty, mixed mesic, Pachic Haplustoll that holds approximately 250 mm of plant available water.

Hybrids had higher grain yield, water use, and water use efficiency than the inbred parents under both irrigated and nonirrigated conditions. Estimates of water use by both hybrids and inbreds were greater for irrigated than for nonirrigated treatments. Early ear dry weight appeared to be an indicator of final ear weight, and in this particular study, was an indicator of final grain weight. Canopy temperatures were cooler for hybrids than for the inbreds which is consistent with greater water use by the hybrids. Stomatal resistance and xylem water potential were not significantly different among genotypes.
The Effect of N Fertilizer Source on Grain Yield, N Uptake, Soil pH, and Lime Requirement in No‐Till Corn1
Authors: Fox R. H. , Hoffman L. D.
Published: July 2010

The increasing use of no‐till crop production with urea based N fertilizers in the Northeast makes it imperative that we obtain a more quantitative understanding of both the magnitude of apparent NH3 losses from nonincorporated urea fertilizers in the field and of the factors that contribute to those losses. A 4‐year field study was conducted on a Murrill silt loam (Typic Hapludult) to compare the yields and N uptake by no‐till corn (Zea mays L.) receiving five rates of broadcast, unincorporated N (0 to 202 kg/ha) as NH4NO3, urea, urea‐NH4NO3 solution (UAN), or (NH4)2SO4. The effects of these sources on the soil pH of the 0 to 2.5 cm and 0 to 17 cm layers and on the lime requirement (LR) in the 0 to 17 cm layer were also measured. In 2 of the 4 years, either urea, UAN, or both produced signifcantly lower yields and N uptake than the non‐urea sources at the higher (101 and 202 kg/ha) N rates. Apparent N volatilization losses ranged from 0 to 35%. Comparing the results from this experiment with those from other field experiments reported in the literature where the effect of rainfall after N application on apparent N volatilization losses could be measured showed that the following observations applied to all: (1) there was insignificant NH3, volatilization loss from unincorporated urea fertilizers if at least 10 mm of rain fell within 48 hours after fertilizer application; (2) if 10 mm or more rain fell 3 days after the urea was applied, volatilization losses were slight (<10%); (3) if 3 to 5 mm of rain fell within 5 days, or 7 to 9 mm within 9 days, volatilization losses could be moderate (10 to 30%); and (4) if no rain fell within 6 days, the loss could be substantial (>30%).

The pH in the surface 2.5 cm of soil in the plots receiving 202 kg/ha/year of N as NH4NO3 urea, or UAN for 5 years was approximately 5.7 or one unit below that in the check. In the plots receiving this rate of (NH4)2SO4, the soil pH in the 0 to 2.5 cm layer was 4.7. As expected, the 101 kg N/ha/year rate produced half was much lowering of pH as the 202 kg/ha rate.

Lime requirement measurements in the surface 17 cm of soil receiving 202 kg N/ha/year for 5 years indicated that approximately 67% of the acidity theoretically produced in the nitrification of NH4+ remained to be neutralized with the less acidifying sources (NH4O3, urea, and UAN) and that approximately 100% of that from (NH4)2SO4 required neutralization.
Post‐dormancy Growth of Bermudagrass as Influenced by Low Temperatures and Selected Preemergence Herbicides1
Authors: Breuninger J. M. , Schmidt R. E.
Published: July 2010

Turf managers in the upper south of the USA must often contend with slow recovery of bermudagrass (Cynodon sp.) following winter dormancy. It is, therefore, essential to identify factors which may contribute to reduced recovery from dormancy if bermudagrass is continued to be grown in this region. In this study, three experiments were conducted to determine the influence of the herbicides DCPA (dimethyl tetrachloroterephthalate), benefin (N‐butyl‐N‐ethyl‐α,α,α‐trifluoro‐2,6 dinitro‐ρ‐toluidine) and oxadiazon [2‐tert‐butyl‐4 (2,4‐dichloro‐5‐isopropoxyphenyl) ‐∆2−1,3,4‐oxadiazolin‐5‐one] on cold temperature tolerance and post‐dormancy growth of three bermudagrass cultivars, ‘Tifway,’ ‘Vamont,’ and ‘Midiron.’

Two laboratory studies were designed to determine the influence of different rates of herbicides on the recovery of dormant bermudagrass that was subject to low temperatures. Herbicides were applied immediately before dormancy was initiated or prior to post‐dormancy growth. A field acclimated study was also conducted to ascertain the effects of herbicide application on post‐dormancy growth of two bermudagrass.

From these experiments it was found that the preemergence herbicides DCPA, benefin, and oxadiazon reduce the cold temperature tolerance of Tifway bermudagrass. Post‐dormant root growth of Tifway bermudagrass was inhibited when new roots came into contact with a herbicide residue from an application prior to dormancy. The most severe root reduction occurred by applications of herbicides to dormant bermudagrass turf made after a laboratory freeze.

Less phytotoxicity was obtained when low dosages of herbicides were applied to dormant Vamont bermudagrass that was not frozen. However, when herbicides were applied after Vamont bermudagrass was frozen, both low and high dosages produced similar results.

Midiron and Vamont bermudagrass differed in their susceptibility to herbicide injury following freezing conditions. Vamont post‐dormancy recovery was decreased by the herbicides applied in this study, but Midiron was not.
Growth Response of Wheat to CO2 Enrichment and Different Levels of Mineral Nutrition1
Authors: Sionit Nasser , Mortensen D. A. , Strain B. R. , Hellmers H.
Published: July 2010

Most previous studies on the influence of CO2 concentration on plant growth have investigated the effect of atmospheric CO2 enrichment alone. Little attention has been given to possible interactions between CO2 enrichment and nutrient supply. The objective of this study was to characterize the long‐term effects of atmospheric CO2 enrichment on growth components of wheat (Triticum aestivum L.) grown under different nutritional levels.

Growth and yield responses of spring wheat (cv. GWO1809) to two (350 and 675 ppm) CO2 and four (full strength, 1/2, 1/8, or 1/16 strength Hoagland's solution No. 1) nutritional levels were measured in controlled environment chambers at day/night temperature of 26/20 C. Plants were grown from seed and were irrigated with respective nutrient solutions three times daily until maturity.

Plants grown in a 675 ppm CO2 atmosphere produced more total dry matter at each nutrient level compared to those grown in 350 ppm CO2. The root:shoot ratio decreased with increased nutritional level in both CO2 concentrations. Total weight and number of seeds produced in high CO2 were greater than those produced in low CO2 under similar nutrition. In low CO2, seed weight and number increased with each increase in nutrient concentration up to the one‐half strength level and then decreased with full strength. In high CO2, however, increasing the nutritional level from one‐half to full strength did not decrease seed weight and number significantly. As the plants grew older, the increments of increase in total plant dry weight during harvest intervals were always greater in plants grown in 675 ppm CO2 than those grown in 350 ppm CO2.
Modeling Biomass Production of Sweet Sorghum1
Authors: Shih S. F. , Gascho G. J. , Rahi G. S.
Published: July 2010

Sweet sorghum [Sorghum bicolor (L.) Moench] is a leading contender in biomass production energy systems because of its high biomass yield, high percentage of easily fermentable sugars and combustible organics, tolerance to water stress, and low fertilizer requirements. However, scientific information on growth factors is limited and precludes establishing valid interrelationships for predicting biomass production. With that objective in mind, a field study on sweet sorghum was conducted to investigate the relationships among stalk length, leaf area index, and dry biomass. Cultivar Mer 71‐7 was planted using two row configurations of single rows on 71‐cm centers and double rows on 142 cm centers on Pahokee muck (Lithic Medisaprist). The spacing between double rows was 30 cm. Leaf area, stalk length, and dry leaf biomass were periodically monitored. Six equations involving leaf area were developed. The first equation estimated leaf area (A) from the length of leaf (L) and the maximum width of leaf (W), i.e., A = 0.741 LW. The second equation estimated leaf area from the length of leaf alone, i.e., A = 0.083 L2. The third equation estimated leaf area per stalk (Y) from stalk length (X), i.e., Y = Exp[X/(2.106 + 0.093X + 0.629X × 10‐4X2)]. The fourth equation showed the dry leaf biomass accumulation (DAR) as a function of time (T), i.e., DAR = 0.764 × 10‐3T0.481. The fifth equation predicted the leaf dry biomass (LDB) from DAR and leaf area index (LAI), i.e., LDB = DAR × LAI. The sixth equation estimated total dry biomass (TDB) from LDB and ratio of dry leaf biomass to total dry biomass (DBPL), i.e., TDB = LDB/DBPL. The relationships developed appeared to be useful for estimating sweet sorghum biomass. However, further testing is needed to evaluate the effects of diverse growing conditions and varieties and to determine the utility of the method in comparison to determining the mean plant weights and populations.
Leaflet Orientation in Water‐stressed Soybeans1
Authors: Meyer Wayne S. , Walker Sue
Published: July 2010

Terminal leaflets of soybeans [Glycine max (L.) Merr.] were observed to become erect and then to invert during a period of soil drying. This study examined the interaction between this movement, abaxial and adaxial stomatal response, water potential, and surface reflectance of terminal leaflets as plant water status decreased. Observations were made on plants in a field with a Rhodic Paleustalf soil type and in which was located a weighing lysimeter.

Terminal leaflets first assumed an erect orientation and then an inverted position as total plant available water decreased below 40%. With more severe water stress a greater proportion of leaflets were affected and lateral leaflets also become inverted. The onset of terminal leaflet inversion occurred over a range of leaf water potential values of −1,400 to −1,725 kPa. Inversion of the leaflets exposed the abaxial surface which was more reflective and which maintained a higher level of diffusive conductance under water stress conditions than did the adaxial surface. Leaflet reorientation in water−stressed soybeans may be a mechanism by which water loss is reduced while still maintaining some level of productivity.
Combination of Herbicides for Winter and Summer Weed Control in Turf1
Authors: Johnson B. J.
Published: July 2010

It is usually necessary to apply herbicides to control both winter and summer weeds in bermudagrass [Cynodon dactylon (L.) Pers. ‘Common’] turf. A study was conducted on a Cecil (Typic Hapludult) loam or sandy clay loam at Griffin, Ga. to determine whether combinations of preemergence type herbicides for summer weeds and postemergence type herbicides for winter weeds would control both type weeds as effectively as when each herbicide was applied singly.

Tank mixture of paraquat (l,l′‐dimethyl‐4,4′‐bipyridinium ion) at 0.3 kg/ha with preemergence herbicide treatments generally controlled a higher percentage of winter annual broadleaf weeds than when paraquat was applied alone at the same rate. In contrast, glyphosate [N(phosphonomethyl)glycine] mixtures were less effective than glyphosate alone. Control of corn speedwell (Veronica arvensis L.) was significantly improved from tank mixture of 2,4‐D [(2,4‐dichlorophenoxy)acetic acid] + mecoprop {2[(4‐chloro‐o‐tolyl)oxy]propionic acid} + dicamba (3,6‐dichloro‐o‐anisic acid) with preemergence treatments than with postemergence treatment alone. Bensulide [O‐O‐diisopropyl phosphorodithioate S‐ester with N‐(2‐mercaptoethyl)benzenesulfonamid] and prosulfalin {N‐[[4‐(dipropylamino)‐3,5‐dinitrophenyl]sulfonyl]‐S,S‐dimethylsulfilimine} controlled large crabgrass [Digitaria sanguinalis (L.) Scop.] as effectively when applied as tank mixtures with postemergence herbicide treatments as when applied alone. However, combination of DCPA (dimethyl tetrachloroterephthalate) with the same postemergence treatments reduced large crabgrass control in 1 or more years. Control of goosegrass [Eleusine indica (L.) Gaertn.] from tank mixtures of preemergence treatments with postemergence treatments was just as effective as with preemergence treatments alone.
Yield, Yield Components, and Nutrient Content of Corn Grain as Influenced by Post‐Silking Moisture Stress1
Authors: Harder H. J. , Carlson R. E. , Shaw R. H.
Published: July 2010

Sensitivity of corn (Zea mays L.) grain development to moisture stress is related to the physiological stage of development when stress occurs. For this reason the time when moisture stress occurs is important in determining final grain yield; hence, timing of precipitation or irrigation becomes an important economic factor in corn production. The primary objective of this work was to determine the effect of successive, repetitive moisture‐stress treatments on yield and yield components. To accomplish this goal, experiments were conducted in the movable rain shelter facility at Ames, Iowa, during the summers of 1976 and 1977. With this facility, different soil‐moisture conditions were imposed simultaneously with plants growing under similar conditions of atmospheric demand. Corn plants were grown in containers with 100 liters of a Nicollet loam soil (an Aquic Hapludoll, fine‐loamy mixed mesic). Single and multiple periods of moisture stress were imposed after silking in one, two, or three successive stress cycles to study their effect on grain yield and yield components (kernels/plant and mass/kernel). Successive respective stress treatments on the same plants were included to observe plant response to moisture stress after sink size (kernel number) was altered because of previous stress.

Grain yield reductions of up to 33% depended primarily upon severity and duration of soil‐moisture stress. Additional stress cycles did not always cause an additive reduction in grain yield. Moisture stress that occurred within 2 weeks after silking reduced the number of kernels/plant by about 15% with little influence on final mass/kernel. Additional stress cycles had only minor effects on kernel number. Plants that were stressed shortly after silking and suffered reduction in kernels/plant had shorter, but uniformly filled ears, suggesting that stress‐inhibited development of kernels at the tip of the ear. Moisture stress influenced masskernel in a complex fashion. Decreases up to 20% were observed. The observed pattern for mass/kernel depended on the timing of stress in relation to silking date and previous moisture‐stress history of the plant. Moisture stress increased % N in the grain from 1.7% in controls to 1.8 and 1.9% in one and two repeated stress cycles, respectively, but did not significantly influence % P or % K in the grain at harvest.
Nitrogen Fertilizer Requirements of Irrigated Safflower in the Northern Great Plains1
Authors: Haby V. A. , Black A. L. , Bergman J. W. , Larson R. A.
Published: July 2010

Alternaria carthami‐resistant safflower varieties have been developed for irrigated production in the Northern Great Plains. Data were needed to determine the irrigation and fertilizer N requirements of this crop. Seven rates of N fertilizer in 45 kg/ha increments to 270 kg/ha of silty clay soil types, and two rates of K, 0 and 45 kg/ha, were applied as subplots in a split‐plot, randomized irrigation by N rate study in field research on safflower, Carthamus tinctorius, ‘Sidwill.’ Irrigation treatments were applied at specific plant growth stages. At only one of three sites was seed yield increased by irrigation. In that instance irrigation at early bud stage produced maximum seed yield. Pre‐irrigation and a water table at a depth of 1.5 m at Sites H7 and H8, and above normal precipitation at Site H8, may have limited yield response to irrigation. Test weight of seed was lowered and N, P, and K concentrations in safflower residue were increased by irrigation.

Yield and protein content of the seed increased with increasing fertilizer N rates. The 270 kg/ha fertilizer N rate decreased seed oil content on the site with the highest residual and mineralizable soil N. Test weight response to N rates varied among sites. Increasing rates of N fertilizer increased the N and K but decreased the P concentrations in the safflower stubble. Statistically significant optimum yields were obtained when the sum of residual NO3‐N in the 0 to 1.22 m soil depth, mineralizable N from organic matter and previous crop residue, and fertilizer N equaled 274 kg/ha.
Quantitative Separation of Roots from Compacted Soil Profiles by the Hydropneumatic Elutriation System1
Authors: Smucker A. J. M. , McBurney S. L. , Srivastava A. K.
Published: July 2010

Knowledge of plant root responses to both favorable and unfavorable soil conditions is fundamental to our understanding of the complex root soil interface. One of the greatest hindrances to the frequent measurements of the morphological and physiological responses of plant roots to soil environmental conditions has been the absence of an inexpensive method for quantitatively separating the soil from roots and other biological materials.

The objectives of this study were to develop an inexpensive and quantitative method for separating roots from soils of field and greenhouse experiments and to determine the influence of soil type, pretreatment and plant type on the efficiency of separation.

A mechanized system which separated roots from soil materials was constructed which combines the kinetic energy of pressurized spray jets and the low energy of air flotation. Root elutriation systems were fabricated from commercially available components at a cost of less than $25 per unit excluding labor. A manifold of these units was assembled to increase operator efficiency. Quantitative separation of roots is achieved by a closed system of mechanical separations using water and air to isolate and deposit roots on a submerged sieve. Washing times range from 3 to 10 min and is a function of soil texture, plant species, concentration of the dispersing agent and soaking time. Utilizing a manifold of nine separation units and two personnel, an average of 60 samples could be separated per hour. Water consumption per unit ranges from 2.1 to 3.4 liters per minute. This method, in combination with a powered soil sampler, appears to provide a rapid, quantitative and inexpensive approach for measuring plant root responses to soil biological, chemical, and physical stresses.
Placement of Nitrogen Fertilizers for No‐Till and Conventional Till Corn1
Authors: Mengel D. B. , Nelson D. W. , Huber D. M.
Published: July 2010

High rates of N loss have been observed from N fertilizers applied directly on the surface in no‐till corn (Zea mays L.) production systems. Field experiments were conducted at four locations over a three‐year period to determine what effects N source and N placement had on N losses in both no‐till and conventional till corn production systems. Soils used were: Stoy loam, an Aquic Hapludalf; Clermont silt loam, a Typic Ochraqualf; Avonberg silt loam, an Aeric Fragiaqualf; Chalmers silty clay loam, a Typic Argiaquoll; and Lyles fine sandy loam, a Typic Haplaquoll. Nitrogen sources used were anhydrous ammonia (NH3), urea‐ammonium nitrate solutions (UAN), solid urea and solid ammonium nitrate (NH4NO3). Placement variables used were injection of NH3 and UAN 20 cm below the soil surface and broadcasting UAN, urea and NH4NO3 on the soil surface with no incorporation. Nitrogen rates used were 0 and 165 kg N/ha.

Injecting NH3, or UAN below the surface resulted in consistently higher corn grain yields than applying UAN, NH4NO3 or urea directly on the soil‐residue surface. Percent N in leaf and grain also reflected an increase in N use efficiency with subsurface N placement. Percent N in leaf was significantly higher where NH3 or UAN were injected as compared to UAN or urea surface applied.