bluuebunny/crossref_metadata_2025 huggingface dataset:
Grain Yield of Subsurface Microirrigated Corn as Affected by Irrigation Line Spacing
Authors: Powell Norris L. , Wright F. Scott
Published: July 2010

Without irrigation, crop yields are usually water‐limited on the acid soils of the southeastern USA. Economically feasible irrigation systems that require less water are needed. As part of a feasibility study of subsurface microirrigation for corn (Zea mays L.) production, the effects of irrigation line spacing and irrigation water amount were investigated in a 5‐yr study at Suffolk, VA. The soil was a Uchee loamy sand (loamy, siliceous, thermic Arenic Hapludult) with inclusions of Emporia loamy sand (fine‐loamy, siliceous, thermic Typic Hapludult). Treatments were three line spacings (0.91, 1.82, and 2.74 in apart, buried 0.38 m below and parallel to the crop row), low and high water amounts (about 41 and 62% of average pan evaporation, respectively), and a nonirrigated control. Nonirrigated grain yields ranged from 3.12 Mg ha−1 (1987) to 9.73 Mg ha−1 (1989). Irrigated grain yields ranged from 8.27 to 12.02 Mg ha−1. Except for 1987 (the driest year), there was no significant difference between the low and high water application amounts. In 1987, corn irrigated with the higher rate yielded 34% more. Grain yields were highest with irrigation lines placed under each row (narrow spacing) and ranged from a low of 8.55 Mg ha−1 (wide spacing) in 1989 to a high of 12.25 Mg ha−1 (narrow spacing) in 1990. Increased amounts of irrigation water were needed with the wider line spacing to obtain corn grain yields comparable with the other two spacings. It is unlikely that the lowered yield or increased irrigation water required with wide line spacing could offset additional installation costs for the narrow spacing. Irrigation lines spaced in alternate corn row middles (1.83 m) or under the third row (2.74 m) are recommended.
Fall Tillage Method: Effect on Short‐Term Carbon Dioxide Flux from Soil
Authors: Reicosky Donald C. , Lindstrom Michael J.
Published: July 2010

The increasing concern for rising CO2 concentrations from agricultural activities has prompted the need to better understand the flux of greenhouse gases to the atmosphere. This work determines the effect of four fall tillage methods on short‐term CO2 flux from a Hamerly clay loam (fine‐loamy, frigid Aeric Calciaquoll) in the northern Corn Belt. Moldboard plow only, moldboard plow plus disk harrow twice, disk harrow once, and chisel plow once using standard tillage equipment following a wheat (Triticum aestivum L.) crop were compared with no‐tillage. The CO2 flux was measured with a large portable system commonly used to measure canopy gas exchange of field crops. Measurements of CO2 flux were initiated within 5 min after tillage completion for each tillage treatment and continued intermittently for 19 d. Moldboard plow had the roughest soil surface and the highest initial CO2 flux (29 g m−2 h−1) and maintained the highest flux throughout the study. Moldboard plow plus disking twice and chisel plow had similar initial rates (7 and 6 g m−2 h−1, respectively) that were greater than disk harrow and no‐tillage. The high initial CO2 fluxes were more related to depth of soil disturbance that resulted in a rougher surface and larger voids than to residue incorporation. The differences in CO2 flux between tillage treatments were small but consistent 19 d after initial tillage and 64 mm rain. Lower CO2 flux rates caused by tillage were associated with low soil disturbance and/or small voids. Tillage methods affected the initial CO2 flux differently and suggest improved soil management can minimize agriculture's impact on global CO2 increase.
Crop Rotation and Tillage Effects on Soil Water and Cotton Yield
Authors: Bordovsky J. P. , Lyle W. M. , Keeling J. W.
Published: July 2010

The Texas Southern High Plains is a major cotton (Gossypium hirsutum L.) producing area where a monoculture of conventionally tilled continuous cotton is thought to be causing a downward trend in yields. A factorial experiment with split plot design evaluated the main and interactive effects of (i) cotton‐wheat (Triticum aestivum L.)‐fallow rotation vs. continuous cotton, (ii) no tillage vs. conventional tillage, and (iii) furrow diking vs. no diking on cotton yield and soil water. Effects were determined for both dryland and irrigated production. Of the main factors considered, the cotton–wheat rotation had the greatest positive effect on yield and also on soil water variables. Rotation increased dryland and irrigated lint yields 12.6 and 12.8%, respectively. No tillage significantly increased yields (6.9 and 5.5% for dryland and irrigated, respectively) and enhanced seasonal soil water status. Yield increase due to diking was not statistically significant (P > 0.05) under continuous cotton production or when wheat was rotated with cotton. The greatest cotton lint yield and soil water increases were obtained when no tillage was combined with the cotton–wheat rotation (20–25% increases). Percent yield increase was directly associated with improved soil water relations resulting from the cropping and tillage treatments.
Bermudagrass and Cool‐Season Turfgrass Mixtures: Response to Simulated Traffic
Authors: Dunn John H. , Minner David D. , Fresenburg Brad F. , Bughrara Suleiman S.
Published: July 2010

Availability of newer, more competitive cool‐season grasses has renewed interest in persistent, balanced warm‐ and cool‐season species mixtures for sports turf. In this Missouri study, one‐time overseedings of blends and mixtures of Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), Chewings fescue (Festuca rubra L. subsp. commutata Gaud.), hard fescue (Festuca longifolia Thuill.), and creeping red fescue (Festuca rubra L. subsp. rubra Gaud.) were made on established plots of KSU S‐16 and ‘Midiron’ bermudagrass [Cynodon dactylon (L.) Pers.]. One‐half of each plot was subjected to simulated traffic beginning 18 mon after overseeding, using a modified Brinkman traffic simulator. Quality of four mixtures (bermudagrass + Kentucky bluegrass, bermudagrass + perennial ryegrass, bermudagrass + perennial ryegrass + Kentucky bluegrass, and bermudagrass + perennial ryegrass + Kentucky bluegrass + Chewings fescue) remained in an acceptable range at most observation dates after 3 yr of spring‐and‐fall traffic. Bermudagrass control plots were in poor or marginal condition at most observation dates during the same period. Bermudagrass plus fine leaf fescues were severely damaged by simulated traffic. Quality of turf receiving no simulated traffic was generally good and varied seasonally in response to changing environmental conditions. Higher‐impact absorption measurements, based on peak deceleration (maximum g) on turf receiving simulated traffic vs. no traffic, were consistent with decreasing thatch and verdure. Traction (in N·m) decreased on trafficked turf as thatch and aboveground biomass deteriorated. Kentucky bluegrass and perennial ryegrass dominated mixtures with bermudagrass after 3 yr, and showed good tolerance to simulated traffic.
Ammonium and Nitrate Nitrogen in Soil Profiles of Long‐Term Winter Wheat Fertilization Experiments
Authors: Westerman Robert L. , Boman Randal K. , Raun William R. , Johnson Gordon V.
Published: July 2010

Accumulation of NH+4 ‐N and NO‐3 ‐N in soils has not been thoroughly evaluated in long‐term continuous winter wheat (Triticum aestivum L.) production systems. The objectives of this study were to determine long‐term response of winter wheat to N fertilization and to evaluate accumulation of NH+4 ‐N and NO‐3 ‐N in the soil profile. Four long‐term winter wheat soil fertility experiments on thermic Ustoll soils that received annual applications of N for > 18 yr at selected N rates were sampled. At each location, one soil core 4.4 cm in diameter was taken to a depth of 240 cm from plots receiving variable N rates. Cores were separated into 30‐cm increments and analyzed for 2 M KCI‐extractable NH+4 ‐N and NO‐3‐N. At all locations, NH+4 ‐N levels were not significantly different from the check (no fertilizer N) when rates were applied at or below yield goal requirements (90 or 45 kg N ha−1 vs. 0 N). At N rates >90 kg N ha−1, surface (0–15 cm) NH+4 ‐N increased compared with the check, while subsurface NH+4 ‐N did not. Similarly, when N rates were <90 kg N ha−1, no significant differences in either surface or subsurface NO‐3 ‐N were found. At N rates >90 kg N ha−1, NO‐3 ‐N accumulated in the subsurface soil profile (>30 cm). Estimates of N rates determined from simultaneous solutions of NO‐3 ‐N accumulation minimums and yield maximums generated from quadratic regression were greater than N rates currently recommended to achieve yield goals at all locations. For these long‐term continuous winter wheat experiments, no accumulation of NH+4‐N and NO‐3 ‐N occurred at recommended N rates where near maximum yields were obtained.
Plasmid Profiles of Rhizobia Used in Inoculants and Isolated from Clover Fields
Authors: Moënne‐Loccoz Yvan , Sen Dipankar , Krause Erica S. , Weaver Richard W.
Published: July 2010

The persistence of inoculant strains of Rhizobium is a factor determining the need for inoculation of legumes. Four pastures in east Texas, with known histories of arrowleaf [Trifolium vesiculosum Savi] and crimson [T. incarnatum L.] clover planting and inoculation with R. leguminosarum bv. trifolii, were used to investigate the prevalence of inoculant strains in clover root nodules. Three pastures had mixed stands of the two clover species, and the fourth had only arrowleaf clover. Using plasmid profiles as a means of identifying rhizobial strains, we analyzed 50 rhizobial isolates made from root nodules of each clover species in each of the pastures. Sixty‐six plasmid profile types were obtained from the 350 isolates. For the first three sites, only 2 of 300 isolates had plasmid profiles matching that of an inoculant strain, and 5 others had profiles similar but not identical to that of another inoculant strain. More than one‐half of the plasmid profile types corresponded to variations of a single type, distinctly different from that of any inoculant strain. At the site where only arrowleaf clover had been grown, 70% of the isolates had a plasmid profile identical to that of an inoculant strain not used at the site. The instability of the plasmid profile of the latter, when grown in vitro, and the similarity of its plasmid and total soluble protein profiles to those of the inoculant strains used at this site, indicate that the prevalent type probably originated from one of them. The inoculant strains failed to persist as such in the field, regardless of the frequency of inoculation.
Allelopathic Characteristics of Three Cool‐Season Grass Species in the Forage Ecosystem
Authors: Smith A. E. , Martin L. D.
Published: July 2010

Allelopathy, the direct or indirect effect of one plant on another through the production of chemical compounds that escape into the environment, occurs widely in natural plant communities and is postulated to be one mechanism by which weeds interfere with crop growth. The purpose of this research was to determine the potential allelopathic influence of selected cool‐season grass species on species interseeded into the pasture ecosystem. Aqueous extracts of tall fescue (Festuca arundinacea Schreb.), Italian ryegrass (Lolium multiflorum Lam.), and little barley [Critesion pusillum (Nutt.) A. Löve; syn. Hordeum pusillum Nutt.] leaf and stem tissue harvested at the mature stage of plant development reduced seed germination and seedling growth of alfalfa (Medicago sativa L.) and Italian ryegrass. It was estimated that 2.8 and 2.5 g L−1 aqueous extracts of mature tall fescue stem tissue, resulted in a 50% reduction in alfalfa seed germination and seedling growth, respectively. For the extracts from Italian ryegrass and little barley, it was estimated that tissue concentrations of near 5.0 g L−1 resulted in a 50% reduction in seed germination and seedling growth for the two bioassay species. Leaf and stem tissue concentrations of the three grasses >7.0 g L−1, resulted in complete inhibition of alfalfa seedling growth. The potential concentration for foliage tissue in soil solution of the pasture ecosystem for tall fescue, Italian ryegrass, and little barley would be 28, 23, and 9 g dry wt. L−1, respectively. Therefore, the allelopathic characteristics of these species could be of economic importance in the pasture ecosystem when overseeding the pasture with annual ryegrass or alfalfa.
Turfgrass Root Systems Evaluated Using the Minirhizotron and Video Recording Methods
Authors: Murphy James A. , Hendricks Michael G. , Rieke Paul E. , Smucker Alvin J. M. , Branham Bruce E.
Published: July 2010

Nondestructive evaluations of turfgrass root systems have been limited to large rhizotrons. Recent developments in the minirhizotron and associated microvideo camera technologies provide opportunities for quantifying in situ root systems of turfgrass field plots. Minirhizotron root counts were compared with destructive core sampling for root length and weight densities of ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.) grown under putting green and fairway conditions, and annual bluegrass [Poa annua L. var. reptans (Hausskn.) Timm] grown under fairway conditions. Correlations between minirhizotron root counts and root length density (cm root/cm3 soil), minirhizotron root counts and root weight density (mg root/cm3 soil), and root weight density and root length density (r2 = 0.861, 0.843, and 0.955, respectively) were very highly significant when data were combined across all depth zones for an October sampling of the bentgrass green. Total root numbers observed along minirhizotrons were greatest early in the growing season, followed by a decline during July. Annual bluegrass root measurements were lower than either of the creeping bentgrass turfs. The root system of the creeping bentgrass turfs recovered during late summer, whereas the annual bluegrass turf showed little recovery from summer root decline. Data indicated that minirhizotron estimates provided an acceptable means for characterizing the profile distribution of turfgrass root systems from the soil surface to 300 mm, and possibly deeper into the soil profile.
Effect of Weed Interference and Soil Nitrogen on Four Maize Hybrids
Authors: Tollenaar M. , Nissanka S. P. , Aguilera A. , Weise S. F. , Swanton C. J.
Published: July 2010

In a mixture of crop and weeds, competition exists between plants for incident solar radiation, soil nutrients, and soil moisture. Integrated weed management manipulates cropping‐system factors such that the competitive relationship favors growth of the crop at the expense of the weeds; however, relatively few studies have been reported on the influence of cropping‐system factors on crop‐weed competition. The objectives of this study were to evaluate the impact of weed interference on the performance of four maize (Zea mays L.) hybrids and to examine the influence of soil N level on the competitiveness of the hybrids. Experiments were conducted during 1990, 1991, and 1992 at the Elora Research Station, Elora, ON, on a London loam (Aquic Hapludalf) soil that had been tile drained. Maize hybrids included an old hybrid (Pride 5, released in 1959) and three more recently released hybrids (Pioneer 3902, DEA, and Pioneer 3953). The maize hybrids were grown at 7 plants m−2 under three weed pressures and at two soil N levels. Weed pressures were established by varying the weed‐free period after planting: all season (weed free), planting to 5‐ to 7‐leaf stage of maize (medium weed pressure), and planting to 3‐ to 4‐leaf stage of maize (high weed pressure). Maize dry matter accumulation and grain yield were measured. Mean grain yield of four hybrids across 3 yr was 65% higher in the high‐N, weed‐free treatment than in the low‐N, high‐weed‐pressure treatment. The effect of weed interference on maize grain yield was higher at low than at high N. Maize hybrids responded differently to N level and weed interference; yield of the old hybrid was reduced more by low N and weed interference than yields of the new hybrids. Consequently, selection of maize hybrid and soil N level should be an integral part in the design of a weed management system.
Nitrogen Source, Timing of Application, and Placement: Effects on Winter Wheat Production
Authors: Mahler Robert L. , Koehler Fred E. , Lutcher L. K.
Published: July 2010

Studies to increase profitability and N use efficiency in winter wheat (Triticum aestivum L.) production are needed to develop more sustainable agricultural systems in the 480‐ to 650‐mm precipitation zone of northern Idaho and eastern Washington. Field experiments were conducted on Latahco silt loam (fine‐silty, mixed, frigid Argiaquic Xeric Argialboll) soils east of Moscow, ID, during the 1982–1983, 1983–1984, 1985–1986 and 1986–1987 growing seasons. Fifteen different N placement‐source‐application timing treatments were arranged in a randomized complete block design with five replications. Fertilizer placements were (i) surface broadcast, (ii) band 50 mm below the seed, and (iii) combinations of surface broadcast and banded below the seed placements. Times of application treatments were (i) fall, (ii) spring, and (iii) various fall‐spring splits. All treatments were evaluated with two N sources: NH4NO3 (AN) and urea (U). Parameters evaluated were (i) winter wheat stand counts, (ii) early‐season plant biomass, (iii) grain yield, and (iv) apparent N use efficiency (NUE). Placement, N source and time of application had minimal impacts on winter wheat stand counts and early season biomass production. Both winter wheat grain yield and apparent NUE were greatest when N applications were split between fall and spring. Splitting time of N application resulted in apparent NUE of 58 to 61%, compared with 52 to 55% and 51 to 53% for fall only and spring only N applications, respectively. Grain yield and apparent NUE differences attributable to N source and N placement were not significant. Based on this study, ideal N management in the 480‐ to 650‐mm precipitation zone would utilize AN, U, or comparable N sources and split N applications where as little as 25% of the N is banded below the seed or surface broadcast in the fall, with the remainder applied as a spring topdress prior to Zadoks growth stage 24. This proposed management will improve both profitability and water quality by increasing both grain yield and N use efficiency when compared with systems currently employed.
Investigating Short‐Term Carbon Flows in the Rhizospheres of Different Plant Species, Using Isotopic Trapping
Authors: Cheng Weixin , Coleman David C. , Carroll C. Ronald , Hoffman Carol A.
Published: July 2010

Many difficulties exist in studying rhizosphere carbon flows in situ because of limited methodologies. Current photosynthate allocation to root respiration, rhizosphere microbial respiration and soluble root exudates in the rhizospheres of winter wheat (Triticum aestivum L.), tall fescue (Festuca arundinacea Schreb.), and buffalo gourd (Cucurbita foetidissima HBK) were investigated using an isotopic trapping procedure. Plants were grown in containers with 165 g of sandy clay loam soil for 3 wk before the time of 14C pulse labeling. Most root exudates were utilized by the microbes in the immediate rhizosphere and released as 14CO2. Only a small amount of exudates was found in the bulk soil (2.7, 2.5, and 3.7% in the control treatments of wheat, tall fescue, and buffalo gourd respectively). The isotopic trapping mechanism was valid for all three species even though the patterns of total rhizosphere respiration (measured as total 14CO2) rates during the initial 8 h of tracing for the three plant species were different in peak time and peak height. The isotopic trapping procedure can be used in rhizosphere studies for various plant species in principle. Some modifications to the procedure may be needed for different plant‐soil systems.
A Computer Program to Analyze Single‐Season Crop Model Outputs
Authors: Thornton Philip K. , Hoogenboom Gerrit
Published: July 2010

Computer simulation models of the growth, development, and yield of annual crops can produce large quantities of data, especially if a simulation experiment involves many treatments and replications across different years. Computer software was written to perform simple analyses of such experiments, allowing the user to identify those treatments that are productive, stable, economically attractive, environmentally sound, or otherwise suitable for the purposes of the investigator. The computer program, which runs on a DOS (IBM‐compatible) personal computer, can interface with output files produced by any crop model run on any other computer that conforms to a common output file structure. Summary statistics for a wide variety of model output variables are calculated and presented to the user in a number of tabular and graphical forms. Net monetary returns and gross margins can also be calculated, and price‐cost variability can be taken into account in the analysis. The user can perform an economic comparison of simulation treatments using mean‐Gini stochastic dominance or, visually, meanvariance analysis. The results of all calculations and analyses are written to an output file that can be manipulated by the user to provide input to a spreadsheet or statistical package for further analysis of the simulated data. The program allows rapid, preliminary analysis of treatments from replicated simulation experiments and can help the user to identify particularly promising treatments that warrant further evaluation.
Calcium Stimulation of Ammonium Absorption and Growth by Beet
Authors: Fenn L. B. , Taylor R. M. , Burks C. M.
Published: July 2010

Inefficiency in N use by plants contributes to environmental degradation. We examined the use of Ca2+ as a means of increasing NH+4 absorption in beet (Beta vulgaris cv. Detroit dark red). Ammonium absorption was measured in greenhouse and field studies. In the greenhouse, beet plants received full‐strength nutrient solutions with Ca2+: NH+4 molar ratios (MR) of 0, 0.25, 0.5 and 1.0 (Ca2+:NH+4) and a NO‐3 check. Absorption of 15NH+4 was monitored over a 30‐h period. The field production trials occurred over 3 yr on a calcareous Saneli silty clay loam [clayey over sandy or sandy‐skeletal, montmorillonitic (calcareous), thermic Vertic Torrifluvent]. The 15NH+4 absorption study showed the greatest plant weight at the molar ratio (MR) of 1.0 in tops (except in seedlings) and at 0.5 in bulbs. In seedlings, a biomass reallocation occurred in the root‐bulbs from the tops. In both the intermediate and mature growth stages the weight of roots, tops and bulbs greatly increased. In the 15NH+4 absorption studies N concentrations were unchanged or decreased as the Ca2+ concentrations increased, but total N increased. Seedling bulb‐root weight increases were apparenlly metabolite transfer from tops. The intermediate and mature beet plants showed increases in total N. In the greenhouse growth test, vegetative matter increased in excess of 300% at the MR of 0.5 over the check (MR:0). Growth of beet in the 0.5 MR treatment exceeded that on the NO‐3 comparison by 14%. In field testing at a MR of 0.25 (CaCl2:urea), yields increases averaged 26% over 3 yr when compared with urea alone.
Mycorrhizal Dependency and Nutrient Uptake by Improved and Unimproved Corn and Soybean Cultivars
Authors: Khalil Samina , Loynachan Thomas E. , Tabatabai M. Ali
Published: July 2010

Plants in nutrient‐deficient soils often benefit when colonized by vesicular‐arbuscular mycorrhizal fungi (VAMF). Plants vary, however, in responsiveness or mycorrhizal dependency (MD). The objective of this work was to evaluate MD within corn and soybean cultivars. Three improved and three unimproved corn (Zea mays L.) and three improved and two unimproved soybean [Glycine soja Siebold & Zucc. and Glycine max (L.) Merr.] cultivars were evaluated for growth response, nutrient uptake (N, P, K, Ca, Mg, and Zn), and root phosphatase activity. Greenhouse studies were conducted with VAMF (Gigaspora margarita or Glomus intraradices) and without inoculation in a Iow‐P soil. The VAMF colonization of roots with inoculation ranged from 62 to 87% for soybean and 49 to 68% for corn. Soybean had a higher MD than corn, but considerable variation occurred within soybean cultivars. Relative growth of the two unimproved soybean cultivars was significantly greater with VAMF colonization than without (Soja, >1900%; Mandarin, >400%). Among improved cultivars, relative growth was less enhanced with colonization (BSR 201, Richland, and Swift cultivars averaged ≈ 200% greater growth with VAMF than without VAMF colonization). An unimproved corn cultivar, Reid Yellow Dent, was unresponsive to mycorrhizal colonization, whereas another unimproved cultivar, Argentine Pop, increased growth 400% with colonization. Total uptakes of N, P, K, Ca, Mg, and Zn were significantly greater (P < 0.001) in mycorrhizal plants, but the concentrations (mg g−1) of N, Mg, and Ca were lower in mycorrhizal plants than in nonmycorrhizal plants. These results suggest that considerable variability exists in MD of corn and soybean cultivars when grown in P‐deficient soils, and the variability extends across both improved and unimproved cultivars.
Development and Growth of White Lupin: Implications for Crop Management
Authors: Duthion Claude , Ney Bertrand , Munier‐Jolain Nicolas M.
Published: July 2010

Grain yield of spring white lupin (Lupinus albus L.) varies greatly with sowing date and density. These effects seem to be related to variability of the canopy architecture. To explain and predict such effects, plant growth and development were characterized at different sowing dates and densities and were related to the distribution of seed number between the main stem and branches. ‘Lublanc’ white lupin was sown in field environments for 9 yr, in the greenhouse for 2 yr, and in a growth cabinet for 1 yr at different densities and at different dates within seasons. Current management techniques were applied. Measurements included successive numbers of main‐stem leaf primordia, successive numbers of main‐stem leaves, date of flower initiation on the main stem, date of flowering on the main stem (SF), absorbed photosynthetically active radiation (PAR) by linear sensors (1 yr) or by leaf area index measurement (2 yr), and weekly accumulated dry matter (DM). Flowering date varied between 366 and 621 degree‐days (base 3°C) from emergence and was closely related to the final number of main‐stem leaves. Leaf number was linked to cumulative vernalizing degree‐days received by the apex. Thus, SF was dependent on temperatures during early growth. Absorption efficiency of PAR (εa) varied with plant density, but at high plant densities, regardless of the year, a single curve represented εa change over time. This limit curve gives the maximum possible εa at a given date. Until seed filling began, the coefficient of absorbed PAR conversion was 1.90 g DM MJ−1. Our results contribute to improved management of lupin crops by suggesting cultural practices to minimize climatic hazards from drought and high temperatures.
Mechanisms Responsible for Soybean Yield Response to Equidistant Planting Patterns
Authors: Egli Dennis B.
Published: July 2010

Increased soybean [Glycine max (L.) Merrill] yields in narrow rows can occur without an increase in light interception during reproductive growth. Experiments were conducted for 3 yr in the field to investigate mechanisms responsible for this response. Two Maturity Group IV cultivars (Pennyrile, indeterminate growth habit, and Ripley, determinate growth habit) were grown in 0.76‐m rows or an equidistant planting pattern (each plant ≈0.2 m from all neighboring plants) at a population of 27 plants m−2. Seeds were planted on 5 June 1990, 22 May 1991 and 15 May 1992. The experiment included irrigated and nonirrigated treatments; however, rainfall was above normal every year, and there was no effect of irrigation on yield. Light interception at growth stage R2 was higher (14%) in the equidistant pattern for both cultivars but there was no difference at growth stage R5. Yield of Ripley in the equidistant pattern was significantly higher (9‐19%) than the rows every year, while Pennyrile showed a significant increase only in 1990. The increase in yield occurred because of an increase in seeds per square meter; seeds per square meter was significantly linearly related to fertile nodes (nodes with at least one normal pod) per square meter for Ripley (r2 = 0.42), but not Pennyrile. Ripley showed an increase in fertile nodes per square meter in the equidistant pattern but Pennyrile did not. The data suggest that the increase in seeds per square meter occurred as a result of a more efficient utilization of assimilate associated with more nodes per square meter.
Degradation of Three Warm‐Season Grasses in a Prepared Cellulase Solution
Authors: Magai Margaret M. , Sleper David A. , Beuselinck Paul R.
Published: July 2010

Information is needed on the relationship between anatomical structure and the rate and extent of cell wall degradation in warm‐season forage grasses. The objective was to study the pattern, rate, and extent of tissue degradation of three warm‐season grasses in a prepared cellulase solution, using light microscopy. Most recent fully collared leaf blades from field‐grown big bluestem (Andropogon gerardii Vitman), indiangrass [Sorghastrum nutans (L.) Nash] and switchgrass (Panicum virgatum L.) were cut into 5‐cm sections and digested in 10 mL prepared cellulase solution with an acid‐pepsin pretreatment. All material was in a vegetative state. Leaf segments were retrieved after 3, 9, 24, 48, and 72 h incubation and prepared for light microscopy by fixation, dehydration and embedding in Spurr's low‐viscosity resin. Sections 5 μm thick were made using an ultramicrotome, and undigested tissues in cross section were measured with a computer‐based image analysis system. The proportion of undigested tissue in cross section after 72 h incubation ranged from 25.4% in big bluestem to 35.0% in switchgrass. Switchgrass contained a higher percentage of parenchyma bundle sheath tissue than either big bluestem or indiangrass. Digestion of all tissues except mesophyll and phloem was delayed until after 24 h incubation. Differences among species tended to be greater in extent of digestion than in rate. Degradation of the parenchyma bundle sheath was significantly less in switchgrass than in either big bluestem or indiangrass after 72 h incubation. Digestion of the abaxial epidermis was nearly complete in big bluestem after 72 h incubation. The adaxial epidermis was more readily degraded than the abaxial epidermis. These results imply that differences in digestibility among the three warm‐season grasses could be attributed to differences in the degradation of their individual tissue types.
Soybean Yield Reductions Caused by Defoliation during Mid to Late Seed Filling
Authors: Board James E. , Wier Alan T. , Boethel David J.
Published: July 2010

Little is known about soybean [Glycine max (L.) Merr.] yield response to defoliation during the last half of the seed‐filling period (R6.3 to R7) and how it is affected by source/sink ratio. Because defoliating insect pests in the southeastern USA frequently attack soybean during this period, greater knowledge of yield responses to defoliation at this time would aid in making management decisions. Therefore, the objectives of this field study were to (i) determine yield losses to total defoliation near the temporal midpoint (R6.3) and three‐quarter point (R6.6) of the seed‐filling period; (ii) determine if alterations in source/sink ratio affect this response; and (iii) determine yield component mechanisms responsible for the yield reduction. ‘Centennial’ soybean was planted in 1991 and 1992 near St. Gabriel, LA. Treatments were no defoliation (control), 100% defoliation at R6.3, and 100% defoliation at R6.6 arranged as split plots within high, normal, and low source/sink ratios during seed filling (main plots). Defoliation at R6.3 resulted in 40% yield reduction, whereas defoliation at R6.6 caused a 20% yield loss. Lower yield resulted from reduced seed size. Source/sink ratio did not affect this response. Smaller seed size in both defoliation treatments resulted partly from reduced seed‐filling rate (28% less than control). Shorter effective filling period also contributed to smaller seed size, but this effect was influenced by treatments and years. In conclusion, 100% defoliation during R6.3 to R6.6 must be avoided to maintain optimum yield.
A Criterion for Acceptance of Narrow‐Row Culture in Soybean
Authors: Board James E. , Harville Bobby G.
Published: July 2010

Soybean [Glycine max (L.) Merr.] yield response to narrow compared with wide rows in the southeastern USA has usually been greater for late than for optimal plantings. Identification of growth responses explaining this pattern could help develop criteria for acceptance of narrow‐row culture. Narrow‐row yield responses result from increased pod number created by greater light interception and crop growth rate between first flowering and seed initiation (R1 to R5). Lack of yield response to greater light interception in narrow rows in optimal plantings may be related to the association between pod number and total dry matter at harvest maturity (R8). Our objectives were to determine if total dry matter at R8 [TDM(R8)] could be used as a criterion for acceptance of narrow‐row culture and to identify the morphological relation between pod number and TDM(R8). Field studies conducted in 1987 through 1990 used optimal and late planting dates, two soybean cultivars, and several row spacing‐plant density combinations. Results indicate a quadratic response of pod number to TDM(R8). Narrow‐row yield responses occurred when light interception (R1 to R5) increased crop growth rate (R1 to R5) to ≤ 15 g m−2 d−1 and increased TDM(R8) to ≤ 800 g m−2. The ratio of pod number to TDM(R8) declined as TDM(R8) approached 800 g m−2, because of a reduced ratio of branch nodes to branch dry matter. In conclusion, narrow‐row yield responses can be expected if TDM(R8) in wide rows is <800 g m−2.
Simulated Hail Damage to Rice: I. Susceptible Growth Stages
Authors: Counce Paul A. , Wells Bobby R. , Norman Richard J.
Published: July 2010

Hail damage often occurs to rice (Oryza sativa L.) and crop insurance adjusters need guidelines to assess likely yield reductions. Moreover, defoliation and other types of crop damage can also occur from insects and wind and potential yield effects need to be determined for crop management decisions. Field experiments designed to evaluate effects of simulated hail damage were conducted on a Crowley silt loam soil (fine, montmorillonitic, thermic Typic Albaqualfs) near Stuttgart, AR, from 1980 through 1984. Treatments began with attempts to simulate hail damage and were refined over time based on data from earlier studies. Preflood N fertilization treatments were tested to determine whether vegetative defoliation yield reductions could be remedial. Simulated hail damage at vegetative growth stages resulted in highly variable yield responses. In one treatment, however, leaf removal prior to reproductive growth was remedied by additional preflood N. Significant yield reductions were consistently found for simulated hail damage treatments during reproductive stages of growth. The most severe damage resulted from defoliation followed by culm severing; the least damage was caused by culm bending. These experiments established that yield losses from simulated hail damage could be documented for four stages of growth (panicle initiation, booting, heading, and some time during grain‐filling) for three different kinds of damage (leaf removal, culm severing, and culm bending).
Yield and Nitrogen Requirement of No‐Tillage Corn as Influenced by Cultural Practices
Authors: Eckert Donald J. , Martin Victor L.
Published: July 2010

Nitrogen fertilizer use efficiency in corn (Zea mays L.) production could be improved if farmers adjusted N fertilizer rates for different yield potentials caused by variations in cultural practices. Five studies were conducted in Ohio, three on Hoytville silty clay (fine, illitic, mesic Mollic Ochraqualf) and two on Riddles silt loam (fine‐loamy, mixed, mesic Typic Hapludalf), to assess the effects of planting date, plant population, N rate, and timing of N application on yield of two corn hybrids grown using no‐tillage methods. Increasing plant population increased grain yield in only one of five site‐year comparisons, but did not increase the amount of N required to produce maximum yield. Crop yield potential varied depending on site‐year, with maximum grain yield indicated by response functions ranging from 5.5 to 11.3 Mg ha−1 for early‐planted corn, and 3.0 to 10.1 Mg ha−1 for late‐planted corn. Nitrogen rates needed to achieve maximum yield varied from 0 to 205 kg N ha−1 for early‐planted corn and from 0 to 175 kg N ha−1 for late‐planted corn, depending on site‐year. In most site‐years, late‐planted corn required less N to achieve maximum yield than early‐planted corn. The reduction in N requirement averaged 60 kg N ha−1, and was directly related to the magnitude of the yield reduction associated with delayed planting. Split applications of N generally produced yields equivalent to application of all N at planting. Split application can offer many farmers a way to use lower N rates to compensate for delayed planting.
Conservation‐Tillage Grain Drill for Furrow‐Irrigated Cropping Systems
Authors: Pearson Calvin H. , Hammon Robert W. , Golus Harold M. , Hain James P.
Published: July 2010

Conservation‐tillage grain drills, used in research and commercial production, have been designed mainly for rainfed conditions. A no‐till grain drill was fabricated at Colorado State University that can be used for both research and commercial plantings in furrow‐irrigated cropping systems. The drill is 4.58 m long, 3.25 m wide, 1.83 m high, and weighs 2200 kg. It has adjustable drive wheels, lift assist wheels, and seed openers to accommodate various furrow row spacings, seed row spacings, and individual seed opener planting depths. The grain drill has the capability to plant alfalfa (Medicago sativa L.), barley (Hordeum vulgare L.), wheat (Triticum aestivum L. emend. Thell.), oat (Avena sativa L.), soybean [Glycine max (L.) Merr.], dry bean (Phaseolus vulgaris L.), and possibly other seeds. The grain drill has performed well in residue conditions as high as 5 Mg ha−1. Most drill adjustments require ≈1 h.
Response of Hybrid and Open‐Pollinated Safflower to Plant Population
Authors: Gonzalez Jose L. , Schneiter Albert A. , Johnson Burton L. , Riveland Neil R.
Published: July 2010

Four safflower (Carthamus tinctorius L.) cultivars were evaluated at five plant populations in experiments over 2 yr at three North Dakota locations. Differences in achene yield due to plant population were not significant. Hybrid AGC‐353 produced significantly higher achene yield than the other cultivars. Number of capitula per plant and achenes per capitulum were the yield components most influenced by plant population. Cultivar effects were significant for all yield components. Plant population did not influence achene oil content; however, significant differences among genotypes occurred. Cultivar S‐541 and hybrid AGC‐353 produced significantly higher and lower achene oil percent, respectively, than the other cultivars. The significantly higher hull content of hybrid AGC‐353 compared with the other cultivars caused the low oil content.
Crop Net Carbon Dioxide Exchange Rate and Radiation Use Efficiency in Soybean
Authors: Rochette Philippe , Desjardins Raymond L. , Pattey Elizabeth , Lessard Robert
Published: July 2010

Plant growth is directly related to the fraction of the C fixed by photosynthesis that is converted into phytomass. We report here the results of a study aiming at the estimation of the net CO2 exchange rates (CNCER) of a soybean crop over the growing season. Hourly values of CNCER were estimated based on eddy correlation measurements of CO2 fluxes above the canopy, on chamber measurements of CO2 fluxes at the soil surface, and on the assumption that root respiration can be computed as a fraction of plant daily photosynthesis. Mean daytime CNCER varied between 0.70 and 0.83 mg m−2s−1 for a leaf area index (LAI) greater than 1, with a maximum hourly value of 1.48 mg m−2s−1. Absolute mean nighttime CNCER values were usually <20% of daytime values. Hourly CNCER varied nonlinearly with intercepted photosynthetically active radiation (IPAR). The accuracy of the CNCER estimates was evaluated by comparing the radiation use efficiency of the soybean crop calculated using CNCER estimates with radiation use efficiency calculated using phytomass accumulation. Agreement between the two approaches was within 10% for LAI>2, but calculated CNCER overestimated radiation use efficiency based on phytomass accumulation for smaller values of LAI.
Barley, Canola, and Weed Growth with Decreasing Tillage in a Cold, Semiarid Climate
Authors: Arshad M. A. , Gill K. S. , Coy G. R.
Published: July 2010

Conventional tillage systems are reported to cause soil degradation, yet appropriate conservation tillage practices have not been developed for cold regions of the northern Canadian Prairies. Effects of conventional, reduced, and zero tillage systems (CT, RT, and ZT) on the growth of dryland spring barley (Hordeum vulgare L.), canola (Brassica campestris L.), and weeds were studied on a clay soil (Natriboralf) near Rycroft in northern Alberta. Each crop‐tillage combination was fixed in space from 1989 through 1991. Each season, the CT plots were tilled once in the preceding fall and twice in the spring prior to seeding; the RT plots were tilled once prior to seeding in the spring; the ZT plots received a preseeding glyphosate [N‐(phosphonomethyl)glycine] application in the spring. Crop residue in ZT was spread evenly by harrowing in the spring just prior to seeding. The 1991 available NO3‐N, NH4‐N, and P in soil or total plant N and P were unaffected by tillage, except that NO3‐N was lower under ZT canola. No consistent effect of tillage was detected on total soil moisture, except for lower moisture in the 0‐ to 10‐cm depth under CT in dry periods. As the study progressed, there was a trend of increased weed population response to tillage, relatively greater weed density under ZT, and a shift in species composition. Mean barley total dry matter (TDM) yield was 3.37, 3.09, and 2.93 Mg ha−1 and grain yield was 1.59, 1.41, and 1.35 35 Mg ha−1 under RT, ZT, and CT, respectively. Mean canola TDM yield was 2.92, 2.36, and 2.12 Mg ha−1 and grain yield was 0.84, 0.66, and 0.59 Mg ha−1, under RT, CT, and ZT, respectively. In most cases, however, tillage effects on mean crop yields were nonsignificant (P < 0.05). Overall, RT was considered to be agronomically and environmentally desirable, due to somewhat better crop yield than either CT or ZT systems and two fewer cultivations than CT.
Estimation of Leaf and Stem Area in the Wind Erosion Prediction System (WEPS)
Authors: Retta Amare , Armbrust Dean V.
Published: July 2010

A process‐oriented wind erosion prediction system (WEPS) is being developed. Among the processes to be simulated is the influence of biomass cover in dissipating wind energy at the soil surface. The wind speed profile within the canopy is a function of the distribution of leaf and stem areas by height. Relationships are needed to calculate leaf and stem areas and leaf and stem masses for use in area and mass by height distribution functions. Alfalfa (Medicago sativa L.), corn (Zea mays L.), oat (Avena sativa L.), sorghum [Sorghum bicolor (L.) Moench.], soybean [Glycine max (L.) Merr.], and winter wheat (Triticum aestivum L.) were planted in different years, soil types, and management regimes. The objective was to obtain relationships that could be used to simulate leaf and stem area growth. Measurements were made of leaf and stem areas and leaf and stem masses. Linear and nonlinear regressions of leaf dry weight on leaf area and of stem dry weight on stem area were performed. The linear model fit the leaf data for all crops and also fit the stem data for alfalfa, oat, soybean, and winter wheat, with r2 values ranging from 0.83 to 0.99. The stem data of corn and sorghum fit the nonlinear model (with r2 = 0.99 and 0.92, respectively). Regression parameters for stem appear to be less affected by environmental factors (e.g., management, different years, varieties, or soil types) than are the regression parameters for leaf. The linear and nonlinear relationships can be used to estimate leaf and stem area growth from their respective masses.
Yield Performance of Banana Irrigated with Fractions of Class A Pan Evaporation in a Semiarid Environment
Authors: Goenaga Ricardo , Irizarry Heber
Published: July 2010

There is a scarcity of information regarding the optimum water requirement for banana (Musa acuminata Colla, AAA group) grown under semiarid conditions with drip irrigation in the tropics. A 3‐yr study was conducted on a fine‐loamy, mixed, isohyperthermic Cumulic Haplustoll to determine water requirement, yield, and fruit‐quality traits of the plant crop (PC) and two ratoon crops (R1 and R2) of ‘Grande Naine’ banana subjected to five levels of irrigation. The irrigation treatments were based on Class A pan factors that ranged from 0.25 to 1.25 in increments of 0.25. Drip irrigation was supplied three times a week on alternate days. Results showed significant (P ≤ 0.01) irrigation treatment and crop effects for all yield components, fruit length and diameter, days to flower, and days from flowering to harvest. Highest marketable yield (86.3 Mg ha−1) was obtained from the R2 crop with water application according to a pan factor of 1.25. Plant crop and R1 plants irrigated using the same pan factor yielded 45.3 and 70.3 Mg ha−1, respectively. Increasing the pan factor from 0.25 to 1.25 resulted in weight gains of the third‐upper hand of 70% in PC, 90% in R1, and 122% in R2. Irrigation according to increasing pan factors resulted in significant increases on the number of hands per bunch and the length and diameter of fruits in the third‐upper and last hands in the bunch. It was concluded from this investigation that, to attain high yields, banana grown under semiarid conditions should be irrigated with a pan factor of not less than 1.0.
Critical Petiole Nitrate‐Nitrogen for Lint Yield and Enhanced Maturity in Pima Cotton
Authors: Tewolde Haile , Fernandez Carlos J. , Foss D. C. , Unruh Larry G.
Published: July 2010

Petiole NO3‐N concentration (PNN) has been recommended as an indicator of midseason N deficiency in upland cotton (Gossypium hirsutum L.). Its use in Pima cotton (G. barbadense L.) management, exspecially when early maturity is the goal, is not well documented. A 3‐yr study evaluated PNN as an indicator of N status in Pima cotton in order to identify a critical minimum PNN level for yield and early maturity. Treatments were five preplant applied N rates of 0 to 180 kg ha−1 in 1990 and 0 to 269 kg ha−1 in 1991 and 1992. The PNN was measured throughout boll development, starting ≈ 2 wk before or at first flower. Applied N significantly (P ≤ 0.05) affected PNN in 1991 and 1992, when residual soil N was low, but not in 1990, when residual N was high; differences among treatments in 1991 and 1992 were largest during early flowering. PNN was a good indicator of plant N status within but not across seasons. Based on early‐flowering samples, the critical PNN level for lint yield was 3.84 g kg−1 in 1991 and only 1.75 g kg−1 in 1992; in 1990, residual soil N alone resulted in PNN much higher than the critical levels in the other years. PNN < 2 g kg−1 in 1991 and < 1 g kg−1 in 1992 resulted in earlier maturity, but also resulted in less lint yield. Pima cotton PNN did not exceed an average of 11 g kg−1, in contrast to 24 to 30 g kg−1 reported for upland cotton. Plant growth or petiole anatomical variables that cause year‐to‐year variation in PNN should be identified and the necessary normalization made before PNN can be used as a midseason diagnostic tool in Pima cotton.