bluuebunny/crossref_metadata_2025 huggingface dataset:
Uptake, Distribution, and Remobilization of 15N‐labeled Urea Applied to Maize Canopies1
Authors: Below F. E. , Crafts‐Brandner S. J. , Harper J. E. , Hageman R. H.
Published: July 2010

Field‐grown maize (Zea mays L.) plants (hybrid B73 X Mo17) were sprayed with 15N‐enriched urea to determine recovery and subsequent distribution within the plant. Plants were sprayed with 15N enriched urea at 7 days pre‐ (treatment 1) and post‐anthesis (treatment 2) to provide a total of 22.3 kg N ha−1 (350 mg N plant−1). Unsprayed plants were used as controls. Plots were located on Flannigan silt loam (fine, montmorillontic mesic Aquic Argiudoll) at stands equivalent to 63 800 plants ha−1. Timing of spray treatment had no effect on grain yield, stover weight, visible leaf senescence, or N content of the plant parts, relative to controls. About one‐third (29% in treatment 1, 30% in treatment 2) of the foliarly applied urea was absorbed and incorporated by the plant. The amounts and distribution patterns within plant parts of foliarly applied N and of total N (N derived from soil uptake and foliarly applied urea N) indicated that leaves were the organs of uptake, and that the stalk served as a conduit for passage of urea‐derived N from leaves to the ear rather than as a storage organ for foliarly applied N. The greater initial rates of loss and the final extent of depletion of N from leaves was greater for foliarly applied N than for total N. This indicated that the foliarly applied N was incorporated into a different pool of N than had been formed earlier by unenriched soil derived N. This observation provides possible explanation for the failure of foliar N applications to increase grain yields of maize.
Fall Cutting of Alfalfa in the North Central USA1
Authors: Tesar M. B. , Yager James L.
Published: July 2010

The North Central (NC) and Northeast (NE) states produce almost two‐thirds of the alfalfa (Medicago sativaL.) in the USA. Three cuttings by early September is the most popular management system. A third cutting in mid‐September to early October has been considered deleterious to subsequent yield and persistence compared with cutting in late August or early September. Our objective was to determine the effects of the final cutting date on subsequent yields and persistence of fertilized and unfertilized hardy and moderately hardy cultivars in a three‐cut system in southern Michigan. Hardy (‘Vernal’ and ‘Cayuga’) and moderately hardy (‘DuPuits’, ‘Saranac’, and ‘Honeoye’) alfalfa cultivars were used in four separate experiments on well‐drained Conover loam (fine‐loamy, mixed mesic Udollic Ochraqualfs). Third cuttings made on 15 September or 1 or 15 October for three consecutive years did not reduce the subsequent year's yield or persistence compared with the control cutting date of 1 September if the cultivar was resistant to bacterial wilt [Corynebacterium insidiosum(McCull) H.L. Jens] and fertilized with K. Yields were reduced if the cultivar was wilt‐susceptible and was cut on 15 September. Levels of total available carbohydrates (TAC) followed similar bi‐monthly trends between 6 September and 13 December for both cultivars. Average TAC content of the two cultivars increased to 304 g kg−1on 1 November and then decreased to 271 g kg−1on 13 December when alfalfa was dormant. On 13 December, levels of TAC were the same within cultivars for all fall cutting treatments and lower for DuPuits than for Vernal. Yields and persistence were not reduced by variable dates of fall cutting after a second cutting in mid‐July if the cultivar was wilt‐resistant, hardy or moderately hardy, and the soil had been well fertilized with K. The present recommendation of not cutting in September and early October or 4 to 6 weeks before the first killing frost in the NC and NE states should be reevaluated.
Resistance of Plant Roots to Water Loss1
Authors: Baker J. M. , van Bavel C. H. M.
Published: July 2010

In an attempt to resolve questions about the relative magnitudes of root resistance to uptake and exudation, an experiment was conducted in which the root zone of a bermudagrass (Cynodon dactylon ✕ Cynodon transvaalensis L. Pers.) sod was divided by a barrier in such a manner that water could move from one side to the other only through the lateral stems of the connected plants. A large difference in soil water potential between the two sides was created by watering one side only. Under such circumstances nocturnal transfer of significant amounts of water from one side to the other, through the plant system, was observed repeatedly with a gamma probe. A separately measured resistance to uptake allowed calculations of the exudation resistance, which was found to be 1.2 ✕ 107 MPa s−1 m−1, slightly larger, but of the same magnitude as the resistance to uptake. It was concluded that water will move from root to soil if the potential gradient is in that direction, though other factors such as soil hydraulic conductivity may become limiting.
Cotton Fruiting Modification with Mepiquat Chloride1
Authors: Kerby T. A. , Hake Kater , Keeley Mark
Published: July 2010

Fruiting of cotton (Gossypium hirsutum L.) was evaluated by main stem node and branch position in 11 experiments over a 4‐yr period to determine if mepiquat chloride (MC) (1,1‐dimethylpiperidinium chloride) altered fruiting position development or retention. Fruiting events were monitored for main stem nodes 7 to 20 for first fruiting position on sympodial branches (SB1), secondary fruiting positions on sympodial branches (SB>1), and fruiting positions on monopodial branches (MB). Ten consecutive plants were plant mapped from each of four replications in each experiment and combined as a 40‐plant total for analysis of treatment and node effects using experiments as replications. Mepiquat chloride was applied at 49 g ha−1 when average plant height was 0.57 m and plants averaged 0.9 white blooms m−2. Summed across nodes, plant zones SB1, SB>1, and MB accounted for 60, 26, and 13% of all harvestable bolls, produced 37, 46, and 17% of all fruiting positions, and set 45, 16, and 23% of all fruiting positions as harvestable bolls, respectively. Application of MC did not increase total number of bolls. The interaction of MC treatment and nodes was significant for SB1 and SB>1, with MC treated plants setting more bolls at lower nodes but fewer at upper nodes. The maximum cumulative benefit occurred at node 12 where MC treated plants had 15% more bolls matured than control plants (58.3 and 50.6 bolls m−2, respectively). This advantage from MC treatment was not maintained as upper nodes matured fewer bolls than control plants. Plants treated with MC produced 3.1% fewer (P = 0.07) fruiting positions than control plants (288 and 279 m−2 respectively). Treatment by node interactions were significant for SB1 and SB>1, with MC increasing fruiting positions up to node 15 at SB1 and up to node 9 for SB>1, but having fewer at the remaining nodes. Early boll load was stimulated by MC. Late season boll load was decreased, apparently not by limited initiation of fruiting positions, but rather by increased abortion of fruiting forms. Use of MC according to the rate and timing of these tests would be of benefit when length of the season is a primary constraint to yield potential. In full‐season, non‐rank cotton, however, the early benefit in boll load is lost.
Subsoiling for Nitrogen Applications to Corn Grown in a Conservation Tillage System1
Authors: Reeves D. W. , Touchton J. T.
Published: July 2010

Subsoiling not only improves root penetration and water infiltration but may also provide an efficient means of applying N fertilizer. Field studies were conducted 2 yr on a Norfolk sandy loam (fineloamy, siliceous, thermic Typic Paleudults) and 1 yr on a Dothan fine‐sandy loam (fine‐loamy, siliceous, thermic Plinthic Paleudults) to determine the effect of N source and application method, subsoiling placement, and time of subsoiling and N application on the efficiency of N applied to no‐till corn (Zea mays L.). Urea and NH4N03 (157 kg ha−1) were applied (i) surface‐banded at planting, (ii) in the in‐row subsoil track at planting, (iii) surface‐banded 5 weeks after planting, or (iv) interrow with subsoilers 5 weeks after planting. Nitrification inhibitors, dicyandiamide (cyanoguanidine) (DCD) and ethylene dibromide (1‐2‐dibromoethane) (EDB), were also used with urea applied in subsoil tracks. Neither inhibitor affected grain yields. Applying N in the subsoil track proved an effective application method. Generally, highest yields (8204 to 9486 kg ha−1) were obtained by applying N 5 weeks after planting with in‐row subsoiling. Results indicate no benefit to subsoiling interrow if in‐row subsoiling was done at planting; however, if corn was planted without in‐row subsoiling, subsoiling interrow 5 weeks later improved yields. Interrow subsoiling may be a practical alternate management tool, especially when used to apply sidedressed N, for growers in years when subsoiling at planting is not feasible.
Velvetleaf Control for Solid‐Seeded Soybean in Three Corn Residue Management Systems1
Authors: Freed B. E. , Oplinger E. S. , Buhler D. D.
Published: July 2010

Lack of adequate weed control is considered one of the most important factors limiting acceptance of solid‐seeded soybean [Glycine max (L.) Merr.] and reduced tillage systems. Recent interest in combining these two production practices further complicates weed control. Field research was conducted at Arlington and Janesville, WI, during 1982 and 1983 to evaluate the effectiveness of preemergence and postemergence herbicide treatments for velvetleaf (Abutilon theophrasti Medic.) control in solid‐seeded soybean in three corn (Zea mays L.) residue management systems. Soybean were planted in 0.20‐m‐wide rows following complete tillage (moldboard plow, cultipack), mulch tillage (chisel plow, field cultivate), and no tillage. Preemergence herbicide treatments included combinations of alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl)acetamide] or pendimethalin [N‐(l‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine] with chloramben (3‐amino‐2,5‐dichlorobenzoic acid) or metribuzin [4‐amino‐6‐(l,l‐dimethylethyl)‐3‐(methylthio)‐l,2,4‐triazin‐5(4H)‐one]. Postemergence herbicide treatments included tank‐mix and sequential applications of sethoxydim {2‐[l‐(ethoxyimino)butyl]‐5‐[2‐(ethylthio)propyl]‐3‐hydroxy‐2‐cyclohexen‐l‐one} or fluazifop‐butyl [butyl(±)‐2‐(4‐{[5‐(trifluoromethyl)‐2‐pyridinyl]oxy}phenoxy) propanoic acid] in combination with acifluorfen {5‐[2‐chloro‐4‐(trifluoromethyl)phenoxy]‐2‐nitrobenzoic acid} or bentazon [3‐(1‐methylethyl)‐(1H)‐2,1,3‐benzothiadiazin‐4(3H)‐one 2,2‐dioxide]or both. Preemergence treatments did not completely control velvetleaf and were influenced by residue management. All treatments containing bentazon afforded near complete velvetleaf control without soybean injury, regardless of residue management. Acifluorfen did not completely control velvetleaf and resulted in soybean injury. Soybean yields were not affected by residue management when velvetleaf was controlled. These data indicate that soybean can be successfully produced in a conservation tillage, solid‐seeded system.
Effect of Supplemental Irrigation on the Yield of Coastal Bermudagrass in the Southeastern United States1
Authors: Burton G. W. , Butler J. L. , Hellwig R. E.
Published: July 2010

The objective of this study was to determine the effect of supplemental irrigation on the yield of Coastal bermudagrass [Cynodon dactylon (L.) Pers.] when fertilized annually with 700 kg/ha of N plus adequate P and K, and usually cut at 24‐day intervals. Paired plots, one irrigated to keep soil moisture above 25 MPa, the other not irrigated and replicated six times, received 100 kg/ha of N in mid‐March and after the first six cuts in 1966, 1967, and 1968 when respective annual rainfall was 97, 81, and 82% of the 44‐yr average, and rainfall for the 210‐day test period was 92, 87, and 77% of the 44‐yr average. Irrigation significantly increased the yield on only two of the 23 cuts made during the 3‐yr test period and failed to increase the total yield in 1966, 1967, or 1968. Three‐year respective average annual yields were 13 750 and 13 860 kg/ha for the irrigated and nonirrigated treatments. Irrigation had no effect on protein content or the pelleting properties of the forage produced.
Photoperiod Influence on Development in Sunflower Genotypes1
Authors: Goyne Philip J. , Schneiter A. A.
Published: July 2010

Synchronization of anthesis of male and female inbred sunflower (Helianthus annuus L.) lines to be crossed in either breeding nurseries or seed production fields is important. Research was conducted to determine the influence of photoperiod on phenological development in a diverse group of sunflower genotypes. An understanding of this response would allow the development of a model to predict sunflower anthesis. Sixteen sunflower genotypes, including hybrid and inbred lines, were classified for photoperiod response in greenhouse plantings carried out over a 2‐yr period at Fargo, ND (latitude 46°54′N, elevation 183 m). Plantings were made so that emergence occurred each time natural photoperiod changed by about 1 h. Although some genotypes displayed long‐day, short‐day, or insensitive photoperiodic reactions for the period from emergence to floral bud development, many of the genotypes appeared to be ambiphotoperiodic, with 11 through 13 h at emergence being the photoperiods delaying time to flower bud development. This delay could be of consequence to breeding programs in those latitudes where planting dates may result in emergence and early growth of the sunflower coinciding with these intermediate photoperiods.
Planting Date and Tillage Effects on Corn Following Corn1
Authors: Imholte A. A. , Carter P.R.
Published: July 2010

Crop residue remaining on the soil surface for erosion control under no‐tillage (NT) corn (Zea mays L.) production depresses early season soil temperatures compared to conventional tillage (CT). This has resulted in questions concerning planting date recommendations for NT in the northern United States. The objective of this study was to determine the influence of planting date on crop development and grain yield when corn produced under CT and NT follows corn. Conventional and no‐till systems were compared during 1983 to 1985 at Arlington, WI, on a Plano silt loam (fine‐silty, mixed, mesic Typic Argiudoll). Planting dates were 26 April to 6 May (early), 14 to 19 May (medium), and 27 May to 6 June (late). Plots were overplanted and stands were thinned to constant densities following complete emergence. Daily seed‐zone soil temperature and seedling emergence were measured. Colder soil temperatures under NT were associated with reduced corn emergence, delayed emergence and silking, and increased harvest grain moisture compared to CT, for early planting. With medium and late planting dates, differences between tillage systems for emergence and silk date were less pronounced or inconsistent between years, or both. For both tillage systems, highest grain yields were generally obtained when planting was completed by early May, with yield declining as planting was delayed. Decreased grain yields with NT or delayed planting, or both, were related to reduced cumulative air growing degree days between silk and the first 0°C frost. These results suggest that for corn following corn in northern U.S. regions, current recommendations for early planting under CT are applicable to NT. However, increased seeding rates may be required to overcome reduced emergence with NT systems.
Contributions of Ground Cover, Dry Matter, and Nitrogen from Intercrops and Cover Crops in a Corn Polyculture System1
Authors: Scott T. W. , Mt. Pleasant J. , Burt R. F. , Otis D. J.
Published: July 2010

Continuous corn (Zea mays L.) grown on sloping land and harvested for silage, returns few residues to the soil and leaves the soil unprotected against erosion for most of the year. Three field experiments were conducted on a Lima loam (a fine‐loamy, mixed, mesic Glossoboric Hapludalf) to determine the contributions from various intercrops and cover crops towards ground cover, dry matter, and N. In Exp. 1 and Exp. 2, the effects of intercrops and cover crops were measured by determining corn grain yields following the plow down of the various crops. Corn grain yields following the incorporation of various crops were compared to yields of corn where no cover crops had been incorporated but N rates of 0, 56 or 112 kg ha−1 had been applied. In Exp. 3, the effects of intercrops and cover crops on corn yields were measured over a 5‐yr period. First‐year corn grain yields were neither increased nor decreased as a result of seeding intercrops when the corn was 0.15 to 0.30 m high. All intercrop and cover crop treatments in Exp. 3 provided significantly more ground cover than the control treatment. Annual ryegrass (Lolium multiflorum Lam.), medium red clover (Trifolium pratense L.), and a combination of the two were the most effective in terms of ground cover and dry matter production.
Aerial Parts of Hard Red Spring Wheat. I. Dry Matter Distribution by Plant Development Stage1
Authors: Bauer Armand , Frank A. B. , Black A. L.
Published: July 2010

Information is lacking on the proportionate mass distribution of dry matter among aerial components of spring wheat (Triticum aestivum L.) over its life cycle at recognized plant development stages. Benefits of such an assessment would accrue to segments of the agricultural industry and modelers/forecasters of crop development and yield. Measurements of aerial components were made weekly from the three‐leaf to kernel‐hard stage of three spring wheat cultivars grown on Williams loam (fine‐loamy, mixed Typic Argiborolls) with three fertilizer N and three water levels in 1981 and 1982. Relations were determined of total aerial dry mass percent in leaves, stems, and spikes, of tillers per plant, fresh and dry leaf mass, and leaf area index (LAI) to the Haun scale expanded to include grain filling, and, as well, fresh and dry leaf mass to LAI. Development stage accounted for 92,96,85, and 79% of the change in total aerial dry mass and in percent of aerial dry mass in leaves, stems, and spikes, respectively, and 52, 85, 59, and 59% of tillers per plant, LAI, dry leaf mass, and fresh leaf mass, respectively. About 50% of aerial dry mass at flag leaf was distributed in each of leaves and stems, while maximum tiller number occurred one Haun stage earlier, and maximum LAI at boot stage. Water and N variables altered the magnitude of mass change, but did not cause a shift in development stage when maximums occurred. Through flag‐leaf‐extension stage, LAI changed one unit for each increase of 37 and 237 g m−2 of dry and fresh leaf mass, respectively.
Nitrogen from Soybean for Dryland Sorghum1
Authors: Gakale L. P. , Clegg M. D.
Published: July 2010

Crop and soil data were collected for 2 yr (1984–1985) from a soybean [Glycine max (L.) Merr.]‐grain sorghum [Sorghum bicolor (L.) Moench] rotation experiment established in 1974, to evaluate the residual effects of soybean on N uptake, some agronomic characters, and yield of the sorghum crop and residual soil N accumulation. The soil at the experimental site was a Sharpsburg silt clay loam (fine, montmorillonitic, mesic Typic Argiudoll). Fertilizer rates of 0, 56, 112, and 168 kg N ha−1 were applied to the sorghum crop in both the continuous sorghum and rotation cropping sequences. Total N uptake by sorghum was significantly increased by rotation cropping (P<0.05) when the N fertilizer rate was 112 kg ha−1 or less. Sorghum grown in rotation or with the application of 56 kg N ha−1 or more flowered 6.1 days earlier than continuously grown sorghum without N. At the zero level of fertilizer N, sorghum after soybean yielded 85% more grain than did continuous sorghum. Rotation with soybean increased subsequent sorghum grain 14% compared to continuous sorghum when averaged over 2 yr. At or above the 112 kg N ha−1 level, differences between the cropping systems were not different. Estimates of residual soil N as NO−3−N in 1985 showed that after soybean there was 50 to 60 kg N ha−1 more than after continuous sorghum when 56 kg N ha−1 or less had been applied.
Forage Yield, Nonstructural Carbohydrate Levels, and Quality Trends of Caucasian Bluestem
Authors: Forwood J. R. , Matches A. G. , Nelson C. J.
Published: July 2010

Information is limited on growth pattern and the effects of management on regrowth yield, quality, and total nonstructural carbohydrate (TNC) levels of Caucasian bluestem [Bothriochloa caucasica (Trin.) C.E. Hubb.] grown in the southern Corn Belt. Field studies on a Creldon silt loam soil (fine, mixed, mesic Mollic Fraguidalf) were conducted to determine trends of the above parameters under various primary growth harvests (one‐time harvests at 0, 14, 28, 42, and 56 d after 4 June) and summer and late‐season regrowth harvests (initial harvest on 18 June and 16 July, respectively, with regrowth harvests 14, 28, 42, 56, 70, and 84 d later). Yield increased linearly (104 and 55 kg ha−1 d−1, respectively) for primary growth and summer regrowth, while late‐season regrowth yield had a cubic trend (y = 201 − 11x + 2.3x2 − 0.02x3; x = days after initial harvest). In vitro dry matter digestibility declined linearly with time (2.9 g kg−1 d−1) in primary growth, but the rate of decline varied depending on length of delay for summer and late‐season regrowth (y = 548 − 4.0x + 0.26x2; y = 436 + 0.9x − 0.19x2, respectively). Crude protein declined quadratically under all treatments (y = 125 − 1.0x − 0.005x2; y = 137 − 3x + 0.001x2;y = 71.2 + 1x − 0.001x2, respectively, for primary growth and summer and late‐season regrowth). Neutral detergent fiber levels increased linearly for primary growth and late‐season regrowth (y = 668 + 1.9x;y = 662 + 1.1x, respectively), while summer regrowth response was quadratic (y = 637 + 2.7x − 0.002x2). Digestible dry matter yield increased throughout the season until it declined in late September. Total nonstructural carbohydrate levels were lower than previously found in native C4 grasses and may not be as important for survival in Caucasian bluestem. Our data indicate that a mid‐June defoliation, with further defoliation up to late summer, may optimize Caucasian bluestem's potential in livestock grazing systems.
Photoperiod Requirements for Flowering and Flower Production in Soybean
Authors: Board J. E. , Settimi J. R.
Published: July 2010

Photoperiod has been recognized as playing a major role in soybean [Glycine max (L.) Merr.] growth and development. The objective of these studies was to determine the number of short days (13.5 h) representative of early spring daylengths in the southeastern United States necessary to cause anthesis and adequate flower production in soybean. Growth chamber studies were conducted at the Phytotron at North Carolina State University, during the first 26 wk of 1985. The soybean cultivar Tracy‐M and the delayed flowering genotype D77‐12480 were subjected to treatments in which they were transferred either from short‐day (13.5‐h) to long‐day (16‐h) or long‐day to short‐day treatments at different times of their development. The number of days to first flower and the rate of flower production were taken. Results indicated that Tracy‐M and D77‐12480 appeared to become responsive to short‐day induction at 8 to 12 and 8 to 16 d after emergence, respectively. While flowering occurred in Tracy‐M with as few as eight short days, optimal flower production required short‐day treatment up to and past first flowering. In D77‐ 12480, application of long days before first flowering inhibited any flower production. As in Tracy‐M, short days were required throughout the flowering period for maximum flower production. Results indicate that under field conditions, diminished flower production can be expected if long days occur before or during the flowering period, or both. Short‐day treatment sufficient to cause anthesis was not necessarily adequate for ample flower production.
Variation among Soybean Breeding Lines in Relation to Yield and Seed‐Fill Duration
Authors: Smith James R. , Nelson Randall L. , Vasilas Bruce L.
Published: July 2010

There are exceptions to the positive relationship between seedfilling period (SFP) and seed yield in soybean [Glycine max (L.) Merr.]. Studying genotypes that do not show a positive relationship between SFP and yield may aid in identifying factors that influence seed yield or SFP, or both. The objective of this research was to analyze groups of soybean genotypes that differed in their SFP‐yield relationship, and determine which factors affected seed yield. Eight experimental lines were selected from a ‘Williams’ ✕ ‘Kanrich’ cross to represent the four SFP‐yield combinations of long or short SFP and high or low yield. Replicated field plots were grown in 1984 and 1985 at Urbana, IL, on a Flanagan silt loam (fine, montmorillonitic, mesic Aquic Argiudoll). Data taken in each year included: SFP, seed yield, harvest indices for dry matter and N, total flowers, total pods at three stages (5 mm long, pod containing a seed 3 mm long, and mature pod), and total N and dry matter at the beginning and end of SFP. Early flowering was related to SFP, but not to yield. Rate as well as duration of seed fill can influence seed yield. Total N in the plant at the end of SFP was related to yield, but not to SFP. Total N and dry matter assimilated during SFP, harvest indices for N and dry matter, and final seed yield were all related.
Seasonal Carbon and Nitrogen Accumulation in Relation to Net Carbon Dioxide Exchange in a Carbon Dioxide‐Enriched Soybean Canopy
Authors: Reddy V. R. , Acock B. , Acock M. C.
Published: July 2010

Crop modelers routinely equate net CO2 exchange (CE) in crop canopies with biomass to simulate crop growth and productivity. This study was initiated to validate this relationship experimentally by monitoring CE during a whole‐season C02‐enrichment study on soybean [Glycine max (L.) Merr. cv. Forrest]. Dry weights of soybhean grown in sunlit plant growth chambers in C02 concentrations ([CO2]) of 330,450,600, or 800 μL L−1 were sampled at 25 d after emergence (DAE) and after physiological maturity. Photosynthetic nates (P) and respiration rates were calculated from CE rates measured at 0.25‐h intervals, day and night, throughout an entire season. The accuracy of CE measurements was tested by plotting gross P against [CO2] at 28,54, and 80 DAE (days when light flux density was at least 1300 μmol photons m−2 s−1). Gross P had the expected hyperbolic dependence on [CO2] with all estimated coefficients of determination >0.93. The net CO2 required for producing various plant parts was calculated from measurements of dry weight and N content and from assumptions about carbohydrate, oil, mineral, and lignin content. The amount of C required to fix 1.0 g of N symbiotically has been reported to be anywhere from 2.5 to 19.4 g. In this sludy the relationship between CO2 fixation and biomass was closest when calculations were based on the theoretical value of 2.0 g of C for each gram of N reduced for all [CO2] treatments except 800 μL L−1, where a value of 4.0 g of C per gram of N fitted the data better.
Sunflower Genotype Response to Photoperiod and Temperature in Field Environments
Authors: Goyne P. J. , Schneiter A. A. , Cleary K. C. , Creelman R. A. , Stegmeier W. D. , Wooding F. J.
Published: July 2010

Sunflower (Helianthus annuus L.) is cultivated over a wide range of photoperiod and temperature conditions. The objective of this research was to determine the response of 16 diverse sunflower genotypes to varying photoperiod and temperature. Field research sites were at five locations including Argentina, Alaska, and Hawaii. The photoperiod (daylength + twilight hours) at vegetative emergence (VE) for most sites, except Hawaii and Alaska, ranged from 14.5 to 16.2 h. Within this range there was no evidence that photoperiod affected the time from VE to bud visible stage (R1). Instead, differences in temperature at various sites were responsible for differing rates of development. However, the short photoperiods at VE at Hawaii (11.2 h) decreased development rate and long photoperiods at Alaska (24 h) increased development rate dramatically. A nonparametric method was applied to rank the genotypes into temperature response groups. Four distinct groups resulted for the VE to R1 growth stage intervals, which were classed as very quick, quick, medium, and slow with respect to the time taken to reach R1 from VE. Four groups also resulted for the R1 to anthesis (R5.1) time period. The groups for R1 to R5.1 differed from those for VE to R1. Genotypes within these groups were dissimilar to those for VE to R1. It was concluded that models used to predict phenological development in sunflower could be based on temperature alone provided photoperiod was within the 14.5 to 16.2 h range, To predict development outside this photoperiod range would require photoperiod be included in the model.
Crop Response to Lime and Phosphorus on New Bench Terraces in the Tropics
Authors: Schmidt D. R. , Casler M. D. , Saefuddin A.
Published: July 2010

Population growth in many tropical areas has led to the cultivation of steeply sloped hillsides. Soil disturbance from construction of conservation terraces to reduce land degradation in humid tropical areas often intensifies P deficiency and problems related to acidity. This trial measured the response of food crops to lime and P application for 2.5 yr following construction of bench terraces. Factorial combinations of 0, 2, and 4 Mg ha−1 lime and 0, 10, 20 and 40 kg P ha−1 were applied on a deep, well‐drained clay of volcanic origin (Typic Haplumbrept) at Andapraja, West Java, Indonesia. A pretrial soil test indicated pH of 5.0, available P (Bray 1) of 5.9 mg kg−1 and exchangeable Al saturation of 17%. Upland rice (Oryza sativa L.) responded strongly to P application. Three crops averaged 0.35, 2.45, 2.89 and 3.46 Mg ha− of unmilled grain from respective applications of 0, 10, 20 and 40 kg P ha−1. Lime had no effect on rice yield. Soybean [Glycine max (L.) Merr.] and cowpea [Vigna unguiculata (L.) Walp.] responded to both lime and P but yields were low because of disease. Mean lime and no‐lime yields were 0.48 and 0.62 Mg ha−1 for soybean. Cowpea yields were maximum (0.15 Mg ha−1) at the 2 Mg ha−1 lime rate. Mean P and no‐P yields were 0.13 and 0.64 Mg ha−1 for soybean and 0.01 and 0.13 Mg ha−1 for cowpea. Cassava (Manihot esculenta Crantz) root yield response to P was less pronounced than the response by rice and the legumes, and was the only crop to show a lime ✕ P interaction. This was attributed to limited response to P when lime was applied, significant response to P with zero lime and marked response to lime with zero P. The efficiency of return from applied P indicated that the 10 kg P ha−1 rate applied to rice, soybean or cassava had the highest efficiency, producing yields 70 to 80% of the 40 kg P ha−1 rate.
Localized Dry Spots as Caused by Hydrophobic Sands on Bentgrass Greens
Authors: Tucker K. A. , Karnok K. J. , Radcliffe D. E. , Landry G. , Roncadori R. W. , Tan K. H.
Published: July 2010

Construction of creeping bentgrass (Agrostis palustris Huds.) golf greens with topsoil mixtures that contain 90% or more sand has led to the appearance of irregularly shaped areas of wilted or dead turfgrass known as localized dry spots (LDS). Objectives were to determine by means of a survey the association between management practices and the severity of LDS, and to compare the chemical and physical properties of LDS and adjacent healthy areas (HA) of greens. Turf managers from ten golf courses and the University of Georgia Turfgrass Plots completed a 34‐question survey pertaining to management practices used on their respective greens. Four of the golf courses and the University Turf Plots were selected as sampling sites for soil from both LDS and HA. Soid was analyzed for moisture content, and particle size, as well as hydrophobicity via the water droplet penetration time, and contact angle methods. Soil organic matter, soluble salts, pH, P, K, Ca, Mg, Zn, Mn, B, and NO3, were also determined. In addition, soil from each area was viewed with a scanning electron microscope. Dry spots occurred at all locations surveyed and no correlation was observed between management practices and the severity of LDS. No differences in soil chemical properties were found between LDS and HA, but water droplet penetration time and contact angle were greater in LDS compared to HA. This hydrophobic condition was confined to the top 50 mm of soil in the dry spot samples and coincided with the presence of an organic coating on sand grains that was observed by scanning electron microscopy.
Quantitative Reduction and Inclusion of Plant Tissue Nitrates in Kjeldahl Digestion
Authors: Goyal Sham S. , Hafez Ahmed A.
Published: July 2010

This study was prompted by controversy over the accuracy of the existing predigestion methods to include NO3‐N in Kjeldahl digestion. A system for quantitative reduction of NO−3 to NH+4 using the Zn metal and Cu2+ in 2 M H3PO4 was developed and was used as a predigestion treatment. Using four different acids in a Zn metal and Cu ion system, the efficiency of NO3 reduction was found to be depenndent on the acid type and its concentration. The Cu ions catalyze the Zn‐acid reaction and improved reproducibility compared to treatments with no Cu2+ added. Four milliters 2M H3PO4 containing 40 mg Cu2+ as CuCl2˙2H2O and 0.3 g Zn recovered 100% of the NO−3‐N in plant materials containing as high as 2.51% NO−3–N (200 mg sample). Tissues containing higher levels of NO−3–N may be analyzed using smaller size sample, e.g. 150 mg. The digestion procedure includes acidified H2O2 treatment at low temperature to solubilize unused Zn and partially oxidize plant organic matter to control foaming and frothing. Small digestion tubes (50‐mL) and a digestion block were used for greater efficiency. The method is simple, highly reproducible and convenient.
Sprinkler vs. Flood Irrigation in Traditional Rice Production Regions of Southeast Texas
Authors: McCauley G. N.
Published: July 2010

Sprinkler irrigation of rice (Oryza sativa L.) could conserve water and lower production costs. Tests were conducted for 3 yr (1982–1984) on a Beaumont clay soil (Entic Pelludert) to evaluate 12 rice cultivars under flood and three levels of sprinkler irrigation. Plant growth (height), plant development (days to heading and harvest), yield, yield components, and quality were monitored. Irrigation treatments were main plots and cultivars were subplots. Irrigation treatments 100, 50, and 25 replaced 100, 50, and 25% of estimated evapotranspiration (ETe). Total water applied was 931 mm (1982), 1171 mm (1983), and 1061 mm (1984) for Treatment 100. These applications exceeded the ETe of flooded rice by 331 to 571 mm. Compared to flood irrigation, sprinkler treatments reduced plant height by 0.09 to 0.28 m. Days to heading varied by cultivar and irrigation treatment while days to harvest was not affected by the irrigation treatments. Milled grain was not influenced by irrigation. Compared to the average yield for flood irrigation, sprinkler irrigation reduced yield over 20% with Treatment 100 and key cultivar yields were reduced 28%. Yield loss from Treatment 100 could not be attributed to weeds, diseases, or water availability. Yield loss was due to reduced florets/panicle and reduced fertile florets. With a yield differential in excess of 20%, sprinkler irrigation does not appear to be a viable alternative to conventional flood irrigation in traditional rice‐growing areas.
Carbohydrate and Lignin Partitioning in Sorghum Stems and Blades
Authors: McBee G. G. , Miller F. R.
Published: July 2010

Declining fossil fuel supplies has stimulated development of alternate energy sources from plant biomass. Sorghum [Sorghum bicolor (L.) Moench] has been recognized as an excellent crop for anaerobic fermentation to methane because of high carbohydrate content of the vegetative biomass. This study was conducted to determine quantities of hemicellulose (HC), cellulose (CL), lignin (LG), and nonstructural carbohydrates (NSC) partitioned between stems and blades of a spectrum of sorghums. Six entries, E35‐1, AT✕ 623 ✕ ‘Rio’ (primarily forage types), Giza‐114 (biomass type), RT✕432, AT✕623 ✕ RT✕432, and AT✕623 ✕ RT✕430 (grain types), were produced on a Ships clay (very‐fine, mixed, thermic Udic Chromustert). Plants were harvested at physiological maturity of the kernels, separated into stem and leaf blade fractions, and analyzed for HC, CL, LG, and NSC. Structural component content ranged from 716 to 516 g kg−1 for stems and 652 to 567 g kg−1 for the blades. Stems contained 12 to 39 g kg−1 more LG than blades across entries. Content of HC in blades exceeded that of stems, whereas CL levels were higher in stems than blades for all entries except E35‐1. The ratio of HC/CL ranged from 0.7 to 0.9 in the stems and 1.1 to 1.3 in the blades. Rind and pith of Giza‐114, AT✕623 ✕ Rio and AT✕623 ✕ RT✕430 contained more structural components in the rind. The quantity of NSC was 74 to 216 g kg−1 higher in the stems than blades for all entries. Sorghum stems may contain large quantities of NSC and structural components, but blades are low in NSC for purposes of digestion or methanogenesis.
Legume Species and Proportion Effects on Symbiotic Dinitrogen Fixation in Legume‐Grass Mixtures
Authors: Mallarino A. P. , Wedin W. F. , Goyenola R. S. , Perdomo C. H. , West C. P.
Published: July 2010

Optimal utilization of the N2‐fixation capability of legumes improves forage productivity and quality and reduces the need for N fertilizer. This research assessed N2 fixation in binary mixtures of white clover (Trifolium repens L.) (WC), red clover (Trifolium pratense L.) (RC), or bitdsfoot trefoil (Lotus corniculatus L.) (BT) with tall fescue (Festuca arundinacea Schreb.) (TF) at four legume proportions. Two identical experiments were established in Uruguay, one in 1983 (Exp. 1) and one in 1984 (Exp. 2) that were evaluated for 2 yr. The soil of the area was a fine, montmorillonitic, mesic, Typic Argiudoll. Symbiotically fixed N was estimated by 15N isotope dilution by using TF pure stands as nonfixing reference. The proportion of legume N derived from air (%Ndfa) was larger in winter and spring harvests (82‐95%) than in other harvests, and differences among legumes were minimal. In first harvests after seeding, %Ndfa was 58% for BT and 74% for WC or RC, whereas in summer, WC showed the least %Ndfa. Total fixed‐N yield over 2 yr was greatest for RC‐TF (390 and 330 kg ha−1 for Exp. 1 and Exp. 2) because of both large %Ndfa and legume yield. As legume proportion increased %Ndfa decreased linearly, usually with similar slopes for all legumes. Fixed‐N yield increased linearly as legume proportion increased for RC‐TF and BT‐TF mixtures. For WC‐TF, there were optimal WC proportions between 50 and 70% in seeding years. We conclude that %Ndfa was negatively and linearly related to legume proportion for the three mixtures and that legume‐dominant swards were required to maximize fixed N yields for RC‐TF and BT‐TF but not for WC‐TF. Red clover fixed the greatest amount of N2 under the conditions of this study.
Corn Response to Rye Cover Crop Management and Spring Tillage Systems
Authors: Raimbault B. A. , Vyn T. J. , Tollenaar M.
Published: July 2010

The use of a winter rye (Secale cereale L.) corn (Zea mays L.) doable cropping sequence in combination with appropriate tillage practices could increase biomass production and reduce soil erosion potential in southern Ontario. A 3‐yr study (1982–1984) was conducted at two locations to determine the potential of this sequence for double cropping, and to evaluate spring tillage systems and management of the rye residue on subsequent productivity of corn. Winter rye was planted in early October after corn silage harvest, and either chemically killed or harvested as silage in the spring before corn planting. Rye treatments consisted of no rye, rye harvested in the spring and rye residue left on the plots. Spring cultivation treatments were no‐till, tandem discing, and mold board plowing followed by secondary tillage. The use of a winter rye cover crop delayed corn development and reduced corn biomass yield by 11% at the Elora location and by 17% at the Woodstock location. The adverse effect of the rye crop was more pronounced under no‐till than where the soil was tilled. Removal or retention of the rye residue had no consistent effect on the subsequent corn crop. An allelopathic effect resulting from the rye crop may be one plausible explanation for the reduction in corn yield. Total biomass yield (rye + corn) was increased relative to corn alone, if the soil was cultivated. Therefore, a winter rye‐corn sequence may still be of interest, despite a reduction in corn yield, especially if advantages such as total biomass production and the potential for decreased soil erosion during fall and winter are considered.
Salinity Effects on Vegetative Growth, Seed Yield, and Fatty Acid Composition of Crambe
Authors: Francois L. E. , Kleiman R.
Published: July 2010

Agronomic development and crop diversification may promote an increased acreage of crambe (Crambe abyssinica Hochst. ex R.E. Fries) in the USA. To determine whether crambe can be grown successfully on saline soils, a 2‐yr‐field‐plot study was conducted. Five cultivars and three germplasm releases were grown with four salinity treatments imposed on a Pachappa fine sandy loam (mixed, thermic, Mollic Haploxeralf). Electrical conductivities of the irrigation waters, containing NaCl and CaCl2 (1:1 by weight), were 0.9, 3.7, 5.4, and 7.9 dS m−1. Seed yield, vegetative growth, and fatty acid composition of the seed oil were measured. Seed yield showed no statistical reduction over the salinity range tested each harvest year. Differences between harvest years were statistically significant. Analysis of the combined 2‐yr data showed a 6.5% reduction of seed yield for each unit increase in soil salinity above 2.0 dS m−1. These results place crambe in the moderately sensitive salt tolerance category. Individual seed weight was significantly reduced by salinity for six of the eight cultivars or germplasms studied. Increased salinity did not significantly affect the erucic acid component of the seed oil, but did significantly reduce the oleic, linolenic, and eicosenoic components.
Significance of Ancient Agricultural Soils for Long‐Term Agronomic Studies and Sustainable Agriculture Research
Authors: Sandor J. A. , Eash N. S.
Published: July 2010

For agriculture to be sustainable, it must maintain productivity and environmental conservation for many generations. Long‐term field studies are essential to the development of sustainable agricultural systems because they are a primary source of scientific knowledge about agronomic conditions during long periods of farming. In addition to knowledge generated by monitoring fields during the past century, there is also a need for information on a longer time scale. Ancient agricultural sites are potential sources of information about agronomic conditions after centuries to millennia of use. Although only the end results of farming can be directly observed at these sites, partial reconstruction of the agricultural history is possible. Studies in Peru and New Mexico, in which ancient agricultural soils were evaluated relative to uncultivated soils, are presented here to illustrate the potential of ancient agricultural sites to extend the time perspective of long‐term research on soil tilth, fertility, and conservation. Studies of ancient agricultural sites can also contribute to ideas about land stewardship and agricultural sustainability.
Support for Long‐Term Agricultural Research
Authors: Army Thomas J. , Kemper* W. Doral
Published: July 2010

Agricultural research, like most present day science generally consists of short‐term studies. A sustainable agriculture, however, requires a long‐term field and laboratory approach to determine the, complex interactions of soils, plants, animals, climate, and management. Short‐term funding and pressures to publish are the major, factors discouraging the initiation of needed long term crop and animal research projects.
Soybean Cultivars' Response to Flood Irrigation of Clay Soil
Authors: Heatherly Larry G. , Pringle H. C.
Published: July 2010

Surface irrigation is widely used to increase seed yield of soybean [Glycine max (L.) Merr.] grown on clayey soils of the southern Mississippi River alluvial plain. A field study was conducted on Sharkey clay (Vertic Haplaquept, very‐fine, montmorillonitic, thermic) in 3 yr to measure the effect of flood irrigation of varying duration on yield and yield components of soybean. Treatments were (Treatment 0) nonirrigated; (Treatment I) 24 h to flood (soil submerged 24 h after onset of irrigation) and then drained; (Treatment 2) 24 h to flood plus 24‐h moving water flood, then drained; (Treatment 3) 24 h to flood plus 48‐h moving water flood, then drained, (Treatment 4) soil submerged with static water for 24 h, then drained; and (Treatment 5) soil submerged within 2 h of onset of irrigation, and then drained. All irrigation treatments commenced at first bloom and repeated whenever soil water potential of a treatment dropped below −70 kPa at 30cm depth. ‘Sharkey’ soybean was more responsive than was ‘Centennial’, but all irrigation treatments resulted in significant yield increases of both cultivars in years when rainfall was deficient during reproductive development. Treatment 3 flooding resulted in significantly lower seed yield than did Treatment 1 flooding, while Treatments 1 and 2 floodings achieved similar yield increases. In a rainy year (1988), Treatment 3 average yield was lower than yields from all other treatments. This indicates that even relatively short periods of flooding can be detrimental to soybean if complemented with untimely rainfall. Standing water for 24 h (Treatment 4) produced yield increases that equalled or exceeded those of all the moving water treatments. These results showed that flood inundation of less than 48 h will result in the consistently largest significant yield increase for soybean, and that soybean genotypes differ in their response to flood irrigation.
A Nitrogen‐Phosphorus‐Potassium Model For Forage Yield of Bermudagrass
Authors: Overman A. R. , Dagan A. , Martin F. G. , Wilkinson S. R.
Published: July 2010

A logistic equation was used to relate annual dry matter yield of Coastal bermudagrass [Cynodon dactylon (L.) Pers.] to applied N, P, and K. Yield data from a 4 ✕ 4 ✕ 4 (N ✕ P ✕ K) factorial experiment were analyzed. The second order Newton‐Raphson procedure for nonlinear regression was used to estimate the seven parameters of the model. A correlation coefficient of 0.9884 was obtained with the model for the 64 data points. A response surface for yield as related to N and K at P = 100 kg ha−1 was drawn from the model. Isoquants (constant yield) were drawn for annual yield of 10 Mg ha−1. A residuals diagram showed no trends, lending further validity to the model. These results have application to agricultural production and environmental quality.
Research Plot Planter for Furrow Irrigated Cropping Systems
Authors: Bjornestad Lyle R. , Lauer Joseph G.
Published: July 2010

Commercially available research plot planters are primarily designed for dryland and/or sprinkler irrigation systems. Research plot establishment in cropping systems involving furrow irrigation requires a planter with an adjustable drive system for diverse furrow spacings. Tool bars should have no interfering support brackets. These features will provide the flexibility needed for a wide range of row and furrow spacings. The planter was designed and constructed for establishing research plots in furrow‐irrigated cropping systems. The planter drive wheels provide flexibility for furrow spacings ranging from 0.25 to 2.2 m. Two tool bars with no interfering support brackets allow numerous row spacing arrangements for seed and furrow openers. The planter can be adjusted quickly (approximately 1h) for different furrow systems, and thus, used for research and/or extension demonstration purposes both on‐ and off‐station.