bluuebunny/crossref_metadata_2025 huggingface dataset:
Wind‐Protected Sprayer for Single‐ and Multiple‐Row Field Plot Nurseries
Authors: Jollife Gary D. , Seddigh Majid , Crane Jimmie M.
Published: July 2010

Research plot size and proximity limit postemergence application of nonselective herbicides close to single rows, between plots, and in alleys. We had a wind‐protected spray applicator built to fit a fourwheel all‐terrain vehicle. This equipment has proven versatile, practical, and economical for chemical control of weeds within 10 mm of plants spaced 0.15 m apart in 0.6‐ to 0.9‐m rows, and around research plots.
Integrating Mechanical Weeding with Reduced Herbicide Use in Conservation Tillage Corn Production Systems
Authors: Buhler Douglas D. , Doll Jerry D. , Proost Richard T. , Visocky Mark R.
Published: July 2010

Integrated weed management for conservation tillage systems is needed so producers can minimize the environmental impacts of crop production while maintaining effective weed control and profitability. Reduced levels of herbicides and rotary hoeing were evaluated in combination with interrow cultivation for weed control in corn (Zea mays L.) planted into chisel‐plowed or untilled seedbeds. Atrazine [6‐chloro‐N‐ethyl‐N'‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine] at 1.1 kg a.i. ha−1 or cyanazine{2‐[[4‐chloro‐6‐(ethylamino)‐l,3,5‐triazin‐2‐yl]amino]‐2‐methylpropanenitrile} at 1.7 kg a.i. ha−1 applied within 2 d after corn planting greatly reduced weed growth compared with no herbicide use. These reduced herbicide treatments often controlled weeds as well as a standard full‐rate treatment (atrazine at 1.6 kg ha−1 plus 2.0 kg a.i. ha−1 metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐l‐methylethyl) acetamide]) prior to cultivation in both tillage systems. In the chisel‐plow experiment, rotary hoeing was not as effective as atrazine or cyanazine in reducing early‐season weed growth. In most cases, one or two interrow cultivations following atrazine or cyanazine increased weed control and corn grain yield to levels similar to the full‐rate treatment in both the chisel‐plow and no‐tillage systems. Integrating interrow cultivation with reduced levels of herbicide maintained weed control and corn yield compared with the full‐rate treatment and is an effective weed management option for corn planted in conservation tillage systems.
Residue Removal Method and Herbicides for Tall Fescue Seed Production: I. Weed Control
Authors: Mueller‐Warrant George W. , Young William C. , Mellbye Mark E.
Published: July 2010

Pacific Northwest grass seed production is in transition from reliance on open‐field burning to new systems integrating chemical weed control with mechanical removal of crop residues. Field tests were initiated in 1989 to ascertain if these systems can meet seed trade expectations for genetic purity while maintaining normal seed yields. Fourteen herbicide treatment sequences plus an untreated check were evaluated under five residue removal methods at two sites during two consecutive growing seasons. Residue removal included two methods of burning and three nonburn systems varying in thoroughness of removal. Acceptable control (>90% reduction in ground cover) of volunteer seedling tall fescue (Festuca arundinacea Schreb.), the most abundant weed in all tests, was achieved by nearly all herbicide treatments at one site. At the other site, however, thorough residue removal or aggressive herbicide treatments were required to achieve this same degree of control. Over sites and years, acceptable control without use of herbicides was achieved in one case out of four for the most thorough mechanical residue removal system (vacuum‐sweep, VS) and twice by open‐field burning (FB). Preemergence (PRE) application of pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine] provided acceptable control following VS, FB, and propane flaming (PP). Oxyfluorfen [2‐chloro‐1‐(3‐ethoxy‐4‐nitrophenoxy)‐4‐(trifluoromethyl)benzene] applied postemergence (POST) at 0.28 kg a.i. ha−1 plus diuron [N′‐(3,4‐dichlorophenyl)‐N,N‐dimethylurea] at 2.7 kg a.i. ha−1 controlled weeds in all residue removal methods at one site, and for VS, FB, and PP at the other site. Applied in sequence after each of four PRE herbicides, POST application of 0.14 kg ha−1 oxyfluorfen plus 1.8 kg ha−1 diuron controlled volunteer seedling tall fescue better than POST application of 2.7 kg ha−1 diuron without oxyfluorfen. With properly chosen herbicide treatments, seed trade standards for tall fescue can be met without field burning.
A Comparison of Two Nitrogen Credit Methods: Traditional vs. Difference
Authors: Lory John A. , Russelle Michael P. , Peterson Todd A.
Published: July 2010

Cereals and other nonlegumes typically require less fertilizer N when grown following a legume. Nitrogen credits for a previous legume crop often are used to reduce fertilizer N recommendations in combination with other site‐specific information. Researchers continue to use two methods of determining N credits, the traditional and difference techniques, which often produce unequal estimates. Our objective was to clarify when each method provides accurate N credit estimates. The traditional method compares yield of a nonfertilized nonlegume crop grown in rotation to the fertilizer N response curve of the continuously cropped nonlegume. This approach assumes that fertilizer N compensates for all benefits of rotation. The difference method compares the economic N rate of the nonlegume crop grown in rotation with that of the continuously cropped nonlegume. We use examples from the literature to demonstrate that when non‐N rotation effects are present, N credit estimates from the two methods will differ. The difference method is more accurate and should be used unless it has been demonstrated that non‐N rotation effects are not present.
Water Stress and Clipping Management Effects on Guineagrass: I. Growth and Biomass Allocation
Authors: Páez Alejandra , González O. María E. , Yrausquín Xiomara , Salazar Arturo , Casanova Angel
Published: July 2010

Growth and biomass allocation of grasses depend greatly on their management and water status. This study was conducted to determine the short‐term interacting effects of clipping height and frequency with water stress on growth and biomass allocation of guineagrass (Panicum maximum Jacq.). After seedling establishment, plants were clipped at four frequencies and three heights, followed by exposure to water stress. Some plants were reirrigated to determine recovery. Plants were harvested after the water stress and reirrigation periods. In response to water stress, plants clipped at greater heights experienced a greater reduction of leaf and culm biomass than plants clipped at lower heights. Root biomass of stressed plants increased linearly with increasing clipping height. Leaf area declined linearly in stressed plants and increased in unstressed plants as clipping height increased and frequency decreased. Leaf area ratio (LAR) and specific leaf weight (SLW) of unstressed plants varied little; for stressed plants, however, LAR decreased and SLW increased as clipping height increased and frequency decreased. In well‐watered plants, the root‐to‐shoot ratio (R/S) was lowest with higher clipping; in the stressed plants, R/S increased with increasing clipping heights. During rewatering, a height ✕ stress interaction for leaf and culm biomass and leaf area was due to a smaller recovery for higher‐clipped than for lower‐clipped plants. Water stress decreased leaf and culm biomass and leaf area, reducing LAR and increasing SLW. These effects were greater in plants cut to greater heights and less frequently. Water stress also enhanced root biomass, suggesting photosynthate migration toward the roots.
Influence of Core Aerification, Topdressing, and Nitrogen on Mat, Roots, and Quality of ‘Meyer’ Zoysiagrass
Authors: Dunn John H. , Minner David D. , Fresenburg Brad F. , Bughrara S.S. , Hohnstrater Chris H.
Published: July 2010

Thatch accumulation is a common occurrence in lawn and sports turf and is usually detrimental. We initiated aerification, topdressing, and N treatments in July 1987, to investigate their influence on thatch, mat, quality, and color of zoysiagrass (Zoysia japonica Steud. cv. Meyer). Turfgrass color responses to N were positive and strongly linear. Turfgrass quality was generally good to excellent in response to N. However, trends were not as well defined as color responses and varied according to month and year. The aerification + topdressing combination according to N level was nonsignificant for turfgrass quality in all months and significant for color only in October. Weight of mat, which consisted mostly of rhizomes, and root weights declined linearly in response to increasing N. The root weight response is consistent with research reports of C3 turfgrasses but inconsistent with earlier studies of C4 turfgrasses where root weights increased with increasing N. Mat depth averaged over N was equal in response to topdressing vs. no topdressing. Root weights and mat weight were significantly greater with topdressing. Mat organic matter (OM) was greater with no topdressing. Our results suggest that maintenance of zoysiagrass with only enough N to provide acceptable turfgrass density and color will give the best root development in nonsandy soils. Annual topdressing with soil similar to that of the growing site may further enhance root development.
Cotton Flowering and Boll Retention in Different Planting Configurations and Leaf Shapes
Authors: Heitholt James J.
Published: July 2010

Narrow rows have the potential to increase boll numbers and lint yield of cotton (Gossypium hirsutum L.) compared with conventional row spacing. To optimize production in this system, it is important to know whether narrow‐row‐induced boll number increases are a result of increased seasonal flowering or increased boll retention. The objective of this study was to determine flower production (no. m−2), boll retention [(bolls/flowers) ✕ 1001, main stem node number, and yield as affected by row spacing and plant density. Field experiments were conducted in 1991 and 1992 on a Bosket fine sandy loam in narrow (51 or 76 cm) and wide rows (102 cm) using the normal‐ and okra‐leaf isolines of DES 24‐8 ne cotton. Plant densities were 5, 10, 15, and 20 plants m−2 in 1991 and 2, 3, 5, 10, and 15 plants m−2 in 1992. Averaged across leaf types and plant densities, 51‐cm rows increased the number of flowers by 12% and yield by 4% compared with 102‐cm rows in 1991. Boll retention was 40% for both row spacings. In 1992, averaged across leaf types and plant densities, 76‐cm rows increased the number of flowers by 21% and yield by 6% compared with 102‐cm rows. Boll retention was actually higher in 102‐cm rows (42%) than 76‐cm rows (36%). In general, plant density and the number of main stem nodes had little effect on flower numbers or boll retention. High plant densities tended to reduce the number of main stem nodes per plant. Averaged across row spacings, plant densities, and years, boll retention for normal‐leaf was higher than for okra‐leaf (50 vs. 29%). Results indicate that increased flower production rather than increased boll retention was responsible for the small narrow‐row yield increase.
Pod Yield and Stem Rot Evaluation of Peanut Cultivars Treated with Tebuconazole
Authors: Branch William D. , Brenneman Timothy B.
Published: July 2010

Tebuconazole {α‐[2‐(4‐chlorophenyl)ethyl]‐α‐(1,1‐dimethylethyl)‐1H‐1,2,4‐triazole‐1‐ethanol} has been registered by the U.S. Environmental Protection Agency for use in peanut (Arachis hypogaea L.) production as a new sterol‐inhibiting fungicide, under the trade name Folicur 3.6F. It is labeled to be used as four consecutive sprays between two applications of non‐sterol‐inhibiting fungicides for control of Phaeoisariopsis personata (Berk. & M.A. Curtis) Arx [syn. Cercosporidium personatum (Berk. & M.A. Curtis) Deighton], Sclerotium rolfsii Sacc., and Rhizoctonia solani Kühn. The combination of such new fungicides with improved peanut cultivars could be very beneficial for integrated pest management (IPM) practices. In 1992 to 1994, yield tests were conducted at the University of Georgia Coastal Plain Experiment Station following recommended applications of tebuconazole to determine which 10 runner‐type and 6 virginia‐type peanut cultivars had the highest pod yield and the lowest incidence of southern stem rot or white mold caused by S. rolfsii when grown with and without irrigation. Stem rot incidence was approximately twice as high in the irrigated as in the nonirrigated tests, and the highest incidence of stem rot was observed in the year with the greatest frequency of irrigation. The Georgia Browne and Georgia Green cultivars had the greatest yields and lowest stem rot incidence among the runner types, and Georgia Green had the greatest dollar value of all cultivars under both irrigated and nonirrigated conditions. Among the virginia types, NC 10C consistently had the highest incidence of stem rot over all 3 yr, and NC 7, VA‐C 92R, and NC‐V 11 had the greatest yields. These results show that certain runner and virginia‐type peanut cultivars perform significantly better than others using the current recommended application of tebuconazole.
Sugar Beet Production as Influenced by Row Orientation
Authors: Anda Angéla , Stephens William
Published: July 2010

In some crops, row orientation has been shown to influence yield through the effects on soil temperature. There has been no similar work on sugar beet (Beta vulgaris L.); thus, an experiment was conducted from 1992 to 1994 to determine the effects of row orientation on the growth and production of sugar beet in Hungary. Sugar beet was grown in large field plots oriented either north‐south (N‐S) or east‐west (E‐W) on a silty clay loam soil. Leaf area development, soil and canopy temperatures, and stomatal resistance were monitored during the growing season from April to October, and root yield, sucrose concentration, and sugar yield were recorded at harvest. All three seasons were warmer and drier than normal, so large soil water deficits developed during July to October each year. Significant differences in growth were observed, with rows oriented E‐W developing 15 to 21% larger leaf area indices. The E‐W rows also had greater canopy and interrow soil temperatures and lower stomatal resistances than N‐S rows, except during the middle of the day. On days with northerly winds >2 ms−1,, air and soil surface temperatures in E‐W oriented rows were greater than in N‐S rows throughout the day. Root and sugar yields were consistently greater in N‐S rows despite having a lower sucrose concentration than beet in the E‐W oriented rows. In 1994, sugar yields were 70% less than in 1993 as a result of Cercospora beticola infestation. In all years, the reduced yield in the E‐W rows was caused by more severe water stress compared to the N‐S rows. The higher temperatures also may have led to reduced partitioning of assimilate to roots with a consequent loss of harvestable yield. The results show that, in dry years, farmers may obtain up to 9% increases in sugar yield by planting sugar beet in N‐S rows. However, these conclusions need confirmation under wetter conditions.
Nitrogen in Sugarbeet Tops and the Growth of a Subsequent Wheat Crop
Authors: Moraghan John T. , Smith Larry J.
Published: July 2010

Nitrogen in sugarbeet (Beta vulgaris L.) tops can influence the yield of subsequent small‐grain crops. The objective of this field study was to determine the influence ofsugarbeet tops differing in N concentration on available soil N and plant growth. Responses of spring wheat (Triticum aestivum L.) to fall‐applied urea and high‐N (34.8 g N kg−1 in 1992 and 25.8 g N kg−1 in 1993) and low‐N (14.8 g N kg−1 in 1992 and 12.6 g N kg−1 in 1993) sugarbeet tops were compared on two Calciaquolls in Minnesota during 1993 and 1994. Application of 135 kg N ha−1, the optimal fertilizer rate in both years, increased wheat grain yields by 1832 kg ha−1 in 1993 and by 1518 kg ha−1 in 1994. High‐N sugarbeet tops, which contained 271 and 208 kg N ha−1 in the 1993 and 1994 experiments, respectively, increased grain yields by 2108 kg ha−1 in 1993 and by 1579 kg ha−1 in 1994. The corresponding responses with low‐N sugarbeet tops, which contained 64 kg N ha−1 in 1993 and 85 kg N ha−1 in 1994, were 424 and 392 kg ha−1. These latter responses were equivalent to only 42 and 51%, respectively, of the 1993 and 1994 increases obtained with 45 kg urea N ha−1. Separate field experiments in fallow microplots indicated that fall‐applied, high‐N sugarbeet tops mineralized appreciable quantities of NO3‐N by the following spring. Most of this mineralized NO3 was located in the upper 30 cm of soil. In contrast, considerable Cl added in sugarbeet tops was located in both the 0‐ to 30‐cm and 30‐ to 60‐cm soil depths. Sugarbeet tops can reduce the N‐fertilizer requirement of subsequent crops, and must be considered in relation to possible NO3 pollution of groundwater.
Intercropping Annual Medic with Conventional Height and Semidwarf Barley Grown for Grain
Authors: Moynihan Jones M. , Simmons Steve R. , Sheaffer Craig C.
Published: July 2010

Interseeding annual legumes with grain crops has been proposed as a cropping strategy to enhance ground cover, thereby reducing weed competition, suppressing soil erosion, and providing N for use by subsequent crops. The potential of annual medics (Medicago spp.) for intercropping in small‐grain cropping systems has not been adequately assessed for the north‐central United States. Our objective was to evaluate a spring barley (Hordeum vulgare L.)‐annual medic intercrop system for barley grain yield, fall biomass production, suppression of fall weeds, and quantity of N available for incorporation into the soil. Field experiments were conducted in four Minnesota environments (Becker, Morris, Rosemount, and St. Paul). Conventional height ‘Robust’ and semidwarf ‘Royal’ barley were intercropped with each of three medic species [‘George’ black medic (M. lupulina L.), ‘Mogul’ barrel medic (M. truncatula Gaertn.) and ‘Santiago’ burr medic (M. polymorpha L.)]. Intercropping with medics reduced barley yields by an average of 6% at Rosemount, 30% at St. Paul, and 76% at Becker, compared with monoculture barley fertilized with N. Medics increased yields by 9% at Morris. Intercropping with medic reduced fall weed mass by an average of 65% across environments, compared with the fertilized Royal monoculture. Nitrogen available for incorporation from the barley‐medic intercrops ranged from 66 to 140 kg ha−1 over the environments, whereas N available for incorporation from fertilized barley monoculture ranged from 22 to 80 kg ha−1. We conclude that the prospects for successfully intercropping with annual medic in a barley grain production system are mixed and depend in part on the medic species used and barley stature. A wider array of medic types should be evaluated for their suitability in intercropping with small grains.
Developing Guidelines for Replanting Grain Sorghum: II. Improved Methods of Simulating Caryopsis Weight and Tiller Number
Authors: Heiniger Ronnie W. , Vanderlip Richard L. , Welch Stephen M. , Muchow Russell C.
Published: July 2010

Enhancing the yield prediction accuracy of SORKAM, a growth model for sorghum [Sorghum bicolor(L.) Moench], requires improving the simulation of grain growth and the relationship between tiller number and minimum temperature. A new grain growth equation, developed from 1990 data collected at Manhattan, KS, relates grain‐filling rate to the rate of change of plant dry matter per caryopsis during the effective filling period. Additional functions are specified for the lag and leveling‐off phases of caryopsis growth, resulting in a new submodel, which was tested against data from Kansas and two Australian sites. The tiller number calculation was revised using three years of Manhattan data. After incorporating the new submodels, SORKAM outputs were compared with observed yields and yield components in three Kansas regions. The R2 values for yield increased from 0.27, 0.46, and 0.79 to 0.76, 0.69, and 0.90 for eastern, central, and western Kansas, respectively. Caryopsis weight comparisons showed that the revised model accounted for 48 to 72% of observed variability, up from 15 to 57% for the original model. Tiller number predictions also improved, although modestly.
Aboveground Carbohydrate and Nitrogen Partitioning in Common Vetch during Seed Filling
Authors: Caballero R. , Rebolé A. , Barro C. , Alzueta C. , Ortiz L. T.
Published: July 2010

During seed filling in annual legumes, changes in concentration of assimilates occur simultaneously with plant partitioning, leading to net changes in yield of assimilates derived from the processes of accumulation and redistribution. Field studies were conducted during two growing seasons (1991–1992 and 1992–1993) in central Spain with the objectives of determining models of change for assimilate concentrations with advancing maturity and assessing efficiency of assimilate harvest relative to seed maturation. Concentration of total N, starch, total soluble sugars (TSS), neutral‐detergent fiber (NDF), acid‐detergent fiber (ADF), and acid‐detergent lignin (ADL) were determined in plant parts (seed, pod‐shell, leaf, and stem) of common vetch (Vicia sativa L.) at seven maturity stages defined as progressively higher dry matter (DM) content in the seed (200–250, 250–300, 350–450, 450–550, 600–700, 700–800, and >800 g DM kg−1 seed). Concentration of assimilates in plant parts changed over the whole seed‐filling period. During the phase of rapid seed growth (from 200–250 to 450–550 g DM kg−1 seed), assimilation was dominant for starch (net gain of 1086 kg ha−1), redistribution for TSS (net loss of 104 kg ha−1), and both process were operative in total N (net gain of 193 kg ha−1). During the ripening phase (from 450–550 to >800 g DM kg−1 seed), most chemical components except ADL showed a net loss. Maximum total accumulation for most mobile fractions except TSS was reached at the 450 to 550 g DM kg−1 seed maturity stage. Harvesting common vetch at this stage would represent maximum efficiency for total N and starch. Concentrations of nonstructural chemical components had a nonlinear trend while concentration of fiber fractions and lignin in vegetative structures showed a linear increasing trend over the seed filling phase of common vetch.
Reducing DCPA Losses in Furrow Irrigation by Herbicide Banding and Straw Mulching
Authors: Shock Clinton C. , Seddigh Majid , Hobson Joe H. , Tinsley Ian J. , Shock Byron M. , Durand Lucia R.
Published: July 2010

There are concerns about residues of DCPA (dimethyl 2,3,5,6‐tetrachloro‐1,4‐benzenedicarboxylate) and its two acid metabolites in surface runoff from furrow‐irrigated croplands. We studied the effects of mulching irrigation furrows with wheat (Triticum aestivum L.) straw on DCPA movement in runoff solution, with sediment, and in the soil profile. The study site had a Nyssa silt loam (coarse‐silty, mixed, mesic Xerollic Haplodurid) with a 3% slope. The field was planted to onion (Allium cepa L.) and was furrow‐irrigated 17 times. Prior to mulching, DCPA was either broadcast at 10 kg a.i. ha−1 or banded at 3.4 kg a.i. ha−1 on the top of beds between furrows. DCPA (parent plus metabolites) was measured in the runoff sediment of the first 6 irrigations, and in the runoff solution of the 1st, 3rd, and the 5th irrigation. Regardless of herbicide application method, mulching reduced DCPA losses in sediment of all irrigations and in the runoff solution of the fifth irrigation. Averaged across the 6 irrigations and the 2 herbicide application methods, mulching reduced DCPA transfer in sediment by about 90%. Straw mulch effects on DCPA losses were primarily through reductions in soil loss and runoff volume, whereas DCPA concentration was not affected in runoff solution and was increased in runoff sediment of some irrigations. Mulching increased infiltration of broadcast DCPA but tended to decrease infiltration of banded DCPA. Also, compared with broadcast DCPA, banding the herbicide reduced DCPA losses in sediment of some irrigations. We concluded that the combination of straw mulching and banding DCPA reduces herbicide transfer in surface runoff and movement into thesoil profile.
Effects of Surface‐Applied Limestone on the Efficiency of Urea‐Containing Nitrogen Sources for No‐Till Corn
Authors: Howard Donald D. , Essington Michael E.
Published: July 2010

Fertilizer N and lime amendments are commonly surface‐applied to no‐till (NT) production systems, but research on these practices under NT is limited. We examined the effect of surface‐applied limestone on the efficiency of urea, urea‐NH4NO3 (UAN), and NH4NO3 applied broadcast or injected for NT corn (Zea mays L.) production on loessal soils. No‐till field studies were established on two loessal soils in western Tennessee: a Memphis silt loam (fine‐silty, mixed, active, thermic Typic Hapludalf) that had been in NT for 7 yr and a Collins silt (coarse‐silty, mixed, acid, thermic Aquic Udifluvent) that had been under conventional tillage. Corn, with a wheat (Triticum aestivum L.) cover, was established on the Memphis soil in 1990. In 1994, corn was established on the Collins soil. The experimental design was a randomized complete block with a split‐plot arrangement of treatments. Agricultural limestone was surface‐applied at rates of 0 and 1.12 Mg ha−1, 1 to 3 wk before N treatment. The N treatments were UAN broadcast (UAN‐B), UAN injected (UAN‐I), urea broadcast or split‐applied (Urea‐B and Urea‐S), and NH4NO3 broadcast (AN‐B). Nitrogen treatments were applied at 168 kg ha−1 within 5 d after planting. For the split urea treatment, 84 kg ha−1 N was broadcast at planting and 84 kg ha−1 N was surface‐banded at the 8‐leaf growth stage. Applications of AN‐B, UAN‐B, and Urea‐B resulted in lower grain yields and leaf N concentrations than UAN‐I. These reductions were attributed to N immobilization and NH3 volatilization. Average yield reductions attributed to N immobilization were 8% on the Memphis soil and none on the Collins soil. Volatilization losses attributed to UAN‐B were 8 and 12% for the Memphis and Collins soils, respectively. Yield reductions attributed to NH3 volatilization from Urea‐B were 22 and 19% for the Memphis and Collins soils. Splitting the urea application increased yields relative to the Urea‐B treatment only on the Memphis soil. Surface application of limestone decreased Urea‐B yields.
Seed Yield and Seed Quality Response of Pensacola and Improved Bahiagrasses to Fertilization
Authors: Gates Roger N. , Burton Glenn W.
Published: July 2010

Availability of improved bahiagrass cultivars, such as ‘Tifton 9’, has increased the potential value of seed produced from bahiagrass. Seed yield response of improved entries to fertilizer inputs is unknown and the relationship of fertility to bahiagrass seed quality is poorly defined. Our objectives were to measure seed yield and seed quality response of three bahiagrass (Paspalum notatum Flügge var. saurae Parodi) entries, varying in forage yield, to fertilizer inputs. Bahiagrass was established in 1991 on Clarendon loamy sand (fine‐loamy, siliceous, thermic Plinthaquic Paleudults) near Tifton, GA. Forage production had been evaluated from 1992 to 1994. In 1995 and 1996, seed was harvested from ‘Pensacola’, Tifton 9 (T9), and RRPS Cycle 18 (T18) in July. Eight fertilizer treatments, identical to the 3‐yr forage yield study, included rates of 56, 112, 224, and 448 kg N ha−1; 25 and 49 kg P ha−1; and 47, 93, 139, 186, and 279 kg K ha−1. Seed yield was lower (P < 0.01) in 1995 than in 1996 and year and fertilizer treatment interacted (P < 0.01). Seed yield achieved with 224 kg N ha−1 and the lowest P and K rates was not improved by higher rates. Although fertilizer treatment and entry interacted (P < 0.01), optimal fertilizer inputs among entries were similar. Seed weight was greater in 1995 and was increased (P < 0.05) by spring application of 112 kg N ha−1 compared with 56 kg N ha−1, but not by higher rates. T18 seeds had greater (P < 0.05) emergence 7 or 14 days after planting (DAP) than Pensacola or T9. Emergence 14 DAP was greater with the highest N rates than the lowest rate. Emergence 35 DAP was only influenced by year (1996 > 1995). Moderate levels of N enhanced seed yield. Fertilizer treatment had no important effect on seed emergence or dormancy. Seed production and cumulative emergence of the three entries were similar.
Stabilizing Rainfed Wheat Yields with Supplemental Irrigation and Nitrogen in a Mediterranean Climate
Authors: Oweis Theib , Pala Mustafa , Ryan John
Published: July 2010

The West Asia‐North Africa (WANA) region, with a Mediterranean‐type climate, has an increasing deficit in cereal production, especially bread wheat (Triticum aestivum L.). Rainfed cropping coincides with the relatively cool, rainy winter season, usually from October to May. Cereal yields are low and variable in response to inadequate and erratic seasonal rainfall and associated management factors, such as lack of N and late sowing. In an area where water is limited, small amounts of supplemental irrigation (SI) water can make up for the deficits in seasonal rain and potentially produce satisfactory yields. This field study (1992–1993 to 1995–1996) on a deep clay soil (a Calcixerollic Xerochrept) in northern Syria was conducted for four growing seasons to assess the effects of SI (rainfed, 1/3, 2/3, and full irrigation) combined with N rate (0, 50, 100, and 150 kg ha−1) and sowing date (early, normal, and late) on one traditional (Mexipak 65) and three improved bread wheat cultivars (Cham 4, Cham 6, Gomam). Yields of rainfed wheat varied with seasonal rainfall and its distribution, with all main factors having significant effects. A delay in the sowing date from November to January consistently reduced yields and the response to both SI and N. With irrigation, crop responses were generally significant up to 100 kg N ha−1, while optimum response for rainfed conditions was with 50 kg N ha−1. An addition of only limited irrigation (1/3 full irrigation) significantly increased yields, but near maximum yields were obtained by 2/3 of full irrigation. Responses to N and SI were greatest for the higher‐yielding cultivars. Use efficiency for both water and N was greatly increased by SI. Thus, with minimum irrigation during the winter growing season combined with appropriate management, inputs, and varieties, wheat output could be substantially and consistently increased in the semiarid Mediterranean zone. Production functions developed from this dataset can help predict the effects of changing any of these parameters in other locations in the region.
Background of the MSEA‐RZWQM Modeling Project
Authors: Watts Darrell G. , Fausey Norman R. , Bucks D. A.
Published: July 2010

The Management Systems Evaluation Areas (MSEA) project was established in 1990 as a part of the Midwest Water Quality Initiative to evaluate the effect of agricultural management practices and systems on the quality of water resources, to increase understanding of processes affecting water contamination, and to develop cost‐effective strategies to reduce water contamination from pesticides and plant nutrients. The Midwest was chosen because it produces so much of the country's corn (>80%) and soybean (≈70%) crops, and consumes >50% of the N fertilizer and almost 60% of the herbicides applied. The MSEA project collected a large volume of data across a wide region. Properly calibrated and validated, simulation models could use this database to estimate water quality impacts over much longer periods than the expected life of the MSEA field program and to simulate responses for other combinations of soils, management systems, and weather conditions. The Root Zone Water Quality Model (RZWQM) was chosen for model improvement, calibration, and validation, to be followed by multilocation simulation of several specific management systems used in Midwest corn and corn‐soybean production. Model improvement was an iterative process across multiple locations. The next seven papers in this issue provide an overview of RZWQM Version 3.2, an explanation of the calibration‐validation process, and documentation of that process and the modeling at MSEA locations in Iowa, Minnesota, Missouri, Nebraska, Ohio, and Colorado.
Subsoil Nitrate and Bromide Uptake by Contrasting Alfalfa Entries
Authors: Blumenthal Jürg M. , Russelle Michael P. , Lamb JoAnn F.S.
Published: July 2010

Alfalfa (Medicago sativa L.) is a deeply rooted perennial legume that can protect the environment by absorbing nitrate (NO−3) both better than annual crops and from deeper in the soil. Our objectives were to characterize subsoil NO−3 removal by eight alfalfa entries differing in symbiotic efficiency, root system architecture, forage quality, and leaf morphology, and to evaluate Br− as an alternative tracer to 15N for monitoring NO−3 uptake. Low (=0.3 mM) or high (20 mM) NO−3‐N concentrations were supplied through a subsoil irrigation system installed in a Hubbard loamy sand soil (sandy, mixed Udorthentic Haploboroll) at Becker, MN. Nitrate uptake and N2 fixation were evaluated during two regrowth periods using 15N. We also added small concentrations of Br− to the subsoil NO−3 during three regrowth periods. Subsoil NO−3‐N removal was similar for the seven N2‐fixing entries, suggesting that selection for traits such as root system architecture, high forage quality, or multiple (>3) leaflets does not necessarily confer an advantage in NO−3 absorption. Even though ‘Ineffective Agate’ yielded less herbage than the N2‐fixing entries, this non‐N2 fixing cultivar removed about 38% more subsoil NO−3 than N2‐fixing entries over the growing season. These results confirm our earlier findings that non‐N2‐fixing alfalfa cultivars are likely to be more effective in phytoremediation of NO−3‐contaminated sites than are standard cultivars. It also confirms our earlier conclusion that the simple difference technique may underestimate rates of symbiotic N2 fixation when inorganic N supply is large. A strong correlation between 15N and Br− uptake in the herbage (mg excess Br− = 25.2 × mg excess 15N, r2 = 0.97) led us to conclude that Br‐ can be used as a tracer of NO−3 absorption by alfalfa in the field. This provides a new, dual‐tracer approach for such studies.
Validity and Efficiency of Neighbor Analyses in Comparison with Classical Complete and Incomplete Block Analyses of Field Experiments
Authors: Wu Tianxia , Dutilleul Pierre
Published: July 2010

In classical block analysis, the assumption of independence between observations from neighboring plots within a block is violated when spatial autocorrelation is present, resulting in incorrect treatment effect estimates and an inflated error variance estimate. Before recommending any neighbor analysis designed to account for spatial autocorrelation, its validity in estimation and testing and its efficiency must be examined. Our main objective was to assess the validity and efficiency of five neighbor analyses in comparison with complete and incomplete block analyses, using 50 pseudo‐experiments for each of 50 data sets derived from two uniformity trials for soybean and wheat. The neighbor models were first difference with (FD‐EV) or without (FD) errors in variables, second difference with (SD‐EV) or without (SD) errors in variables, and first‐order autoregressive errors. Geostatistical analysis based on the normalized semivariance detected spatially structured variation at different degrees in the data sets. The first and second differences were effective in removing spatial trends and autocorrelation. Our simulation study showed that FD‐EV provided valid estimates of the error variance in all and SD‐EV in most of the data sets. On average, the observed significance level was slightly beyond the theoretical level for both analyses. The other neighbor analyses underestimated the error variance. Excluding SD, neighbor analyses had similar efficiency and were more efficient than complete and incomplete block analyses, with average relative efficiencies of about 300 and 130%, respectively. Relative efficiency tended to increase with decreasing normalized nugget effect (NC0) and increasing CV. When spatially structured variation is strong (i.e., NC0< 10%), highly rectangular plots must be preferred to nearly square plots in incomplete block and neighbor analyses. Considering validity and efficiency, the best method was FD‐EV, which is thus a reliable alternative to classical block analysis when spatial autocorrelation is present.
Nitrate Reductase Activity of Diverse Grain Sorghum Genotypes and Its Relationship to Nitrogen Use Efficiency
Authors: Traore Abdoulaye , Maranville Jerry W.
Published: July 2010

High crop N use efficiency is desirable for reducing the cost and reliance on fertilizer N, and it may help reduce ground water pollution. The objectives of this study were to (i) characterize and compare the seasonal trends in nitrate reductase activity (NRA) of seven grain sorghum [Sorghum bicolor (L.) Moench] genotypes of tropical and U.S. origin, (ii) determine how NRA is related to total plant N, dry matter, grain yield, and N use efficiency, and (iii) examine how NRA and plant N accumulation affect N use efficiency for biomass (NUE1) and grain production (NUE2). The genotypes were evaluated in field trials in 1994 and 1996 at applied N levels of 0 and 100 N kg ha−1 on a Sharpsburg silty clay loam soil (fine, smectitic, mesic Typic Argiudoll). Plant biomass, reduced N, NRA, NUE1, and NUE2 were determined at three growth stages (vegetative, anthesis, and physiological maturity). Genotypes did not differ for NRA at either N level; however, there was a definite tendency for the four tropical lines and two U.S. adapted lines to have greater NRA values at all growth stages than the one hybrid. Nitrate reductase activity decreased throughout the growing season, with the sharpest decline from anthesis to maturity. Nitrate reductase activity did not correlate with grain yield or shoot biomass, but did correlate with grain N concentration. Shoot and grain N concentration correlated with NUE1, while grain and shoot N contents and shoot N concentration were correlated with NUE2. Neither NUE1 nor NUE2 were significantly affected by the NRA level. Tropical lines had greater preanthesis N uptake accumulation (1.45 g plant−1) and greater NUE1 than the hybrid (0.90 g plant−1) and U.S. adapted lines (0.73 g plant−1). In terms of grain N use efficiency, the hybrid had a 14% greater value than U.S. adapted lines and a 17% greater value than the tropical lines. It appears that NRA is not a factor that limited N accumulation and use efficiency in grain sorghum.
Potential Effect of Soybean Heliotropism on Ultraviolet‐B Irradiance and Dose
Authors: Grant Richard H.
Published: July 2010

Assessing the potential for decreases in crop yield due to stratospheric ozone loss and concomitant increases in ultraviolet‐B (UVB) radiation requires knowledge of the characteristics of UVB irradiance above and within crops and the sensitivity of crops to the detrimental effects of the irradiance. Evaluations of the tolerance of many crops to increases in UVB irradiance have been made. The tolerance or intolerance of a crop to UVB irradiance is in part a result of physical characteristics of the plant. This study evaluated both the distribution of irradiance and the effects of plant leaf heliotropic movement of soybean [Glycine max (L.) Merr.] cultivars on the irradiance received on the leaf surface. Measurements of the above‐canopy UVB irradiance on planes having a wide range of slope and aspect were made under cloud‐free skies in a soybean field during the summer of 1990. Results showed that the relative irradiance was strongly dependent on the leaf inclination angle and could be modeled by a simple function having a relative irradiance accuracy of 0.14 (root mean square error); with greater model error at small incidence angles to the sun than at large incidence angles. The developed model was then used to evaluate the influence of heliotropy on the UVB dose received on the terminal leaflet. These results suggest that heliotropy in the leaflet acts to reduce irradiance. Since the more tolerant soybean cultivars appear to orient leaflets away from the sun, results suggest that the classification of UVB tolerance may be due in part to the capacity for paraheliotropic response reducing the UVB radiation received.
Growth Analysis of Soybean under No‐Tillage and Conventional Tillage Systems
Authors: Yusuf Raji I. , Siemens John C. , Bullock Donald G.
Published: July 2010

Soybean [Glycine max (L.) Merrill] plants grown with no‐tillage (NT) often appear smaller than those grown with conventional tillage (CT), yet they produce similar grain yield. Our objective was to test the hypothesis that the early‐season growth depression is offset by compensatory growth and changes in plant development. A 2‐yr field study was conducted at Urbana, IL, on a long‐term tillage experiment. Grain yield, moisture, protein, and oil content were similar for CT and NT treatments. Total plant, stem, leaf, and pod dry biomass were all initially about 15 to 20% greater under CT, but the difference declined until about R5 or R6; thus, compensatory growth did occur. At the initiation of sampling (V2) crop growth rate was about 20% greater under CT, but the difference declined until about R2. The advantage shifted to NT until about R6. Leaf area index (LAI) was greater for CT until about R4. Net assimilation rate was greater for NT until about R5. Increases in early‐season crop growth rate for CT was due to increased LAI. Greater crop growth rate for NT late in the season was due to increased net assimilation rate. Leaf weight ratio was larger for the CT crop until about R6. Specific leaf area was less in CT than NT. This work supports our hypothesis that compensatory growth and alterations in plant development occur when soybean is grown in NT systems and helps to explain why grain yield does not decrease with NT even though early‐season growth is affected.
Sampling Requirements for Forage Quality Characterization of Rectangular Hay Bales
Authors: Sheaffer Craig C. , Martin Neal P. , Jewett Jane Grimsbo , Halgerson James , Moon Roger D. , Cuomo Greg R.
Published: July 2010

Commercial lots of alfalfa (Medicago sativa L.) hay are often bought and sold on the basis of forage quality. Proper sampling is essential to obtain accurate forage quality results for pricing of alfalfa hay, but information about sampling is limited to small, 20‐ to 40‐kg rectangular bales. Our objectives were to determine the within‐bale variation in 400‐kg rectangular bales and to determine the number and distribution of core samples required to represent the crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and dry matter (DM) concentration in commercial lots of alfalfa hay. Four bales were selected from each of three hay lots and core sampled nine times per side for a total of 54 cores per bale. There was no consistent pattern of forage quality variation within bales. Averaged across lots, any portion of a bale was highly correlated with bale grand means for CP, ADF, NDF, and DM. Three lots of hay were probed six times per bale, one core per bale side from 55, 14, and 14 bales per lot. For determination of CP, ADF, NDF, and DM concentration, total core numbers required to achieve an acceptable standard error (SE) were minimized by sampling once per bale. Bootstrap analysis of data from the most variable hay lot suggested that forage quality of any lot of 400‐kg alfalfa hay bales should be adequately represented by 12 bales sampled once per bale.
Seedling Development of Chicory and Plantain
Authors: Sanderson Matt A. , Elwinger Gerald F.
Published: July 2010

Chicory (Cichorium intybus L.) and plantain (Plantago lanceolata L.) are perennial herbs for pastures. Knowledge of growth and development of these species is needed to develop appropriate management practices. We compared growth and development of chicory and plantain during establishment in growth chamber, greenhouse, and field studies. ‘Grasslands Puna’, ‘La Certa’, and ‘Forage Feast’ chicory and ‘Ceres Tonic’ and ‘Grasslands Lancelot’ plantain seedlings were destructively sampled weekly for 7 wk in the growth chamber and greenhouse beginning 8 to10 days after planting (DAP). The number and mass of leaves and roots (primary, lateral, basal, and adventitious; growth chamber only) were recorded. In the field, leaf development was measured during spring and fall of 1997, whereas leaf and root development were measured during spring of 1999. Puna chicory developed a larger root mass than plantains, whereas plantains had greater root length than chicory. Plantains developed 8 to 10 adventitious roots on the hypocotyl, but the chicory cultivars developed only one or two. Plantain and chicory developed only one or two basal roots per plant. Primary and lateral roots dominated the root systems of both species. Leaf development in fall 1997 was slower than in spring with only two leaves forming on each species by 49 DAP in fall compared with six to seven leaves during spring in the field. Across environments (except fall), seedlings developed three to four leaves by 40 to 50 DAP. Our data suggest that development of three to four leaves is required for successful establishment of chicory and plantain seedlings.
Spectral Vegetation Indices as Nondestructive Tools for Determining Durum Wheat Yield
Authors: Aparicio Nieves , Villegas Dolors , Casadesus Jaume , Araus José Luis , Royo Conxita
Published: July 2010

Remote sensing measurements may be a useful tool for quantifying crop development and yield. Our objective was to study the potential of using spectral reflectance indices to provide accurate and nondestructive estimates of physiological traits determining yield in durum wheat [Triticum turgidum L. subsp. durum (Desf.) Husn.]. Twenty‐five genotypes were grown under rainfed and irrigated conditions in northeastern Spain. Reflectance from the vegetation at different growth stages was measured and the following spectral indices calculated: simple ratio (SR), normalized difference vegetation index (NDVI), and photochemical reflectance index (PRI). Crop dry mass (CDM), leaf area index (LAI), and green area index (GAI) were measured. All the indices and grain yield were greater under irrigated than rainfed conditions. LAI was the crop growth trait that most closely correlated with the spectral reflectance indices, with SR and PRI being the best and the worst indices, respectively, for the assessment of crop growth and yield. In rainfed conditions, the spectral reflectance indices measured at any crop stage were positively correlated (P < 0.05) with LAI and yield. Under irrigation, correlations were only significant during the second half of the grain filling. The integration of either NDVI, SR, or PRI from heading to maturity explained 52, 59, and 39% of the variability in yield within genotypes in rainfed conditions and 39, 28, and 26% under irrigation. Our results suggest that for durum wheat, the usefulness of the SR and NDVI for calculating green area and grain yield is limited to LAI values < 3.