bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Effects on Interspecific Interference among Two Native Wetland Grasses and Tall Fescue
Authors: Steiner Jeffrey J. , Brewer Tim G. , Griffith Stephen M.
Published: July 2010

Successful reintroduction of native species into landscapes requires an understanding of how introduced species invaded and became established. This study was conducted to determine the effect of temperature on interspecific seedling interference of two wetland grasses [sloughgrass (Beckmannia syzigachneSteud.) and tufted hairgrass (Deschampsia caespitosaL.)] native to the Pacific Northwest and tall fescue (Festuca arundinaceaeSchreb. cv. Titan), a non‐native grass species. The relationships of species interference to the thermal response of Photosystem II (PS II) fluorescence reappearance ratio (FRR) and glutathione reductase (GR) thermal stability were also investigated using the Mantel product moment correlation (rm). Three combinations of two‐species replacement series experiments (sloughgrass–hairgrass mixture, sloughgrass–tall fescue mixture, and hairgrass–tall fescue mixture) were conduced in growth chambers, planted in five proportions (0.0:1.0, 0.25:0.75, 0.5:0.5, 0.75:0.25, and 1.0:0.0), and grown at four temperatures (5, 10, 20, and 30°C). The FRR and GR were measured at eight temperatures ranging from 5 to 40°C. Tall fescue aggressiveness, relative to sloughgrass and hairgrass, increased with increasing temperature. Sloughgrass and hairgrass ranked second and third, respectively, and were only more aggressive than tall fescue at 5°C. Peak FRR occurred at 15, 20, and 22.5°C for sloughgrass, hairgrass, and tall fescue, respectively. Seedling dry mass of species was correlated with the stability of GR and the average efficiency of the PS II apparatus over the range of growing temperatures (rm= −1.00 and 0.96, respectively). Tall fescue had greater PS II efficiency and GR stability under elevated temperatures than sloughgrass and hairgrass, which may explain why tall fescue has been able to dominate some wetland landscapes of the temperate Pacific Northwest.
Responses of High‐Oil and Hybrid Corn to Rootworm Beetles during Pollination
Authors: Strachan Stephen D. , Kaplan Stuart L.
Published: July 2010

High‐oil corn (Zea mays L.) may be produced as a physical mixture consisting of 91% male‐sterile hybrid plants and 9% pollinator plants. Two field studies were conducted to determine if corn blends consisting of only 9% pollinator plants are more sensitive to high populations of rootworms (Diabrotica spp.) feeding on silks during pollination than hybrid blends consisting of 50 to 100% male‐fertile plants. In one study, silks of hybrid corn and silks of the male‐sterile hybrid within the high‐oil corn blend were clipped daily during pollination to simulate silk clipping caused by rootworms. In a separate study, 165 locations of high‐oil corn and 134 locations of hybrid corn were monitored for rootworm population and severity of silk clipping during pollination. Grain yield was significantly reduced (P ≤ 0.05) if average lengths of exserted silks were <37 mm for high‐oil blends with 9% pollinator plants and <25 mm for hybrid corn. Oil, protein, and starch concentrations of the high‐oil grain were not significantly different from those of the untreated check if exserted silks were at least 25 mm during pollination. Severity of beetle infestation correlated poorly with daily average silk length (r = −0.06) and with grain yield (r = −0.01). Economic thresholds for grain yield were crossed, and appropriate pest control measures should be considered when rootworm beetles consistently clip exserted silks to <37 mm for high‐oil blends with 9% pollinator plants or <25 mm for hybrid corn.
Fall Dormancy and Snow Depth Effects on Winterkill of Alfalfa
Authors: Leep Richard H. , Andresen Jeffrey A. , Jeranyama Peter
Published: July 2010

The lack of a definitive method to assess winter hardiness in alfalfa (Medicago sativa L.) remains a challenge in the north‐central region of the USA where winterkill of alfalfa can be severe. The reliability of fall dormancy ratings for describing alfalfa cultivar susceptibility to winter injury and the role of snow depth in moderating temperatures near the plant were investigated at Chatham, MI on a Chatham Stony loam (Typic Haplorthod). Four cultivars were selected with a range of fall dormancy ratings: ‘Nitro’, ‘Magnum IV’, ‘Saranac’, and ‘Vernal’. The cultivars were planted in 1993–1994, 1994–1995, and 1995–1996 seasons in plots over which 0‐, 10‐, and 20‐cm winter snow depths were maintained. Temperatures were monitored for each plot, and stand counts were made each fall and spring to assess winter injury. Nitro suffered the most winterkill across snow cover treatments. The total yield range was 0 to 9 Mg ha−1 in the absence of a snow cover and 0.4 to 12 Mg ha−1 for a snow depth of at least 10 cm, except in 1996. Extreme minimum canopy‐level (6 cm) temperatures for 10‐cm snow depth averaged over three winter seasons were 12.1°C higher than the 0‐cm snow cover treatment, which translated into higher yields. The results suggest that snow cover of 10 cm adequately protects alfalfa from winter injury. Cultivars within the same fall dormancy rating did not necessarily perform similarly, suggesting the need to develop other methods for assessing winter survival.
Dairy Effluent Effects on Herbage Yield and Nutritive Value of Forage Cropping Systems
Authors: Macoon Bisoondat , Woodard Kenneth R. , Sollenberger Lynn E. , French Edwin C. , Portier Kenneth M. , Graetz Donald A. , Prine Gordon M. , Van Horn Harold H.
Published: July 2010

The utilization of dairy waste effluent provides nutrients and water for crop growth and allows producers to comply with regulations governing on‐farm recycling of nutrients. Dry matter (DM) yield and nutritive value were measured for forages from five year‐round cropping systems at effluent N rates of 450, 675, and 900 kg ha−1 yr−1 during 4 yr on a Kershaw fine sand (coated, thermic Typic Quartzipsamments) in northern Florida. Cropping systems were rye (Secale cereale L.) grown in tandem with either bermudagrass (Cynodon spp.), corn (Zea mays L.)–bermudagrass (CBR), corn–forage sorghum [Sorghum bicolor (L.) Moench; CSR], rhizoma peanut (Arachis glabrata Benth.; PR), or corn–rhizoma peanut (CPR). Annual yields increased with N level in Years 1 and 2, but not during Years 3 and 4. Yields were similar among BR, CBR, and CSR (25.9 Mg ha−1) in Year 1. In Year 2, BR (31.2 Mg ha−1) had the greatest yield followed by CBR and CSR (avg. 25.5 Mg ha−1). In Years 3 and 4, yields of BR (21.1 Mg ha−1) and CBR (20.7 Mg ha−1) declined while yield of CSR remained constant. Systems CPR and PR yielded less during the 4 yr (17.6 Mg ha−1). In vitro digestibility of BR (580 g kg−1) was lower than for the other systems (mean of 653 g kg−1). Cropping system had a major impact on forage yield and nutritive value, but N rates above 450 kg ha−1 had relatively little effect on these responses.
Weed Control for Stand Duration Perennial Ryegrass Seed Production
Authors: Mueller‐Warrant George W. , Rosato S. Caprice
Published: July 2010

Novel alternatives to open‐field burning recently adopted by Oregon grass seed growers included retaining postharvest residues chopped into mulch. Because herbicide performance had never been tested under such conditions, research objectives included determining (i) efficacy of preemergence and postemergence herbicides on volunteer perennial ryegrass seedlings, (ii) whether treatments could be reapplied annually without damaging stands, (iii) whether common weeds would increase over time, and (iv) effects of volunteer seedlings on crop yield. Techniques were developed to incorporate pendimethalin [N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine] through crop residue. Tests were conducted in three commercial perennial ryegrass (Lolium perenne L.) fields sown in 1991. Preemergence‐incorporated pendimethalin at 2.2 kg a.i. ha−1 improved control of volunteer perennial ryegrass seedlings over postemergence treatments applied alone in 28 out of 46 comparisons, and 12 out of 18 failures to improve control occurred when postemergence treatments themselves adequately controlled weeds (avg. 5.5% ground cover by volunteer perennial ryegrass seedlings, or 93% control). Weed control by postemergence treatments varied greatly among years and sites. Early postemergence oxyfluorfen [2‐chloro‐1‐(3‐ethoxy‐4‐nitrophenoxy)‐4‐(trifluoromethyl)benzene] plus metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylethyl)acetamide] followed by late postemergence diuron [N′‐(3,4‐dichlorophenyl)‐N, N‐dimethylurea] was the most effective postemergence treatment (avg. 92% control), but damaged the crop in several instances. Uncontrolled volunteer seedlings reduced seed yield in no‐postemergence checks compared with treatments including postemergence applications in 19 out of 30 instances the first year, 24 out of 30 instances the second year, but only 3 out of 24 instances the third year. Susceptibility of perennial ryegrass to injury by herbicides increased with stand age but varied among sites.
An Indicator of Solar Radiation Model Performance based on a Fuzzy Expert System
Authors: Bellocchi Gianni , Acutis Marco , Fila Gianni , Donatelli Marcello
Published: July 2010

When evaluating models, various indices or test statistics are computed, quantifying the magnitude of model residuals, the correlation between estimates and measurements, patterns of residuals over external variables, etc. Such indices are variously related to each other, thus making model comparison difficult. Problems of this type emerge when testing solar radiation models. This paper proposes a fuzzy expert system to calculate a modular indicator, Irad, which reflects an expert perception about the quality of the performance of solar radiation models. Three modules were formulated reflecting the magnitude of residuals (Accuracy), the correlation estimates and measurements (Correlation), and the presence or absence of patterns in the residuals against independent variables (Pattern), respectively. The modules Accuracy and Pattern resulted from the aggregation of three (relative root mean square error, modeling efficiency, and t‐Student probability) and two (pattern index vs. day of the year and pattern index vs. minimum air temperature) indices, respectively, while the module Correlation was identified by a single index (Pearson's correlation coefficient). For each index, two functions describing membership to the fuzzy subsets Favorable (F) and Unfavorable (U) have been defined. The expert system calculates the modules according to both the degree of membership of the indices to the subsets F and U and a set of decision rules. Then the modules are aggregated into the indicator Irad. Sensitivity analysis is presented, along with module and Irad scores for some application cases.
Reduced Seeding Rate for Glyphosate‐Resistant, Drilled Soybean on the Southeastern Coastal Plain
Authors: Norsworthy Jason K. , Frederick James R.
Published: July 2010

Seeding‐rate recommendations for narrow‐row (<76 cm) soybean [Glycine max (L.) Merr.] on the southeastern Coastal Plain are almost double those of more traditional, wider row widths. A 2‐yr field study was conducted on a Dothan loamy sand soil to assess how main‐stem and branch yield fractions of four glyphosate‐resistant cultivars, ranging from maturity group (MG) V through mid‐MG VII, would respond to a lower‐than‐recommended seeding rate for narrow‐row culture. The cultivars Pioneer 95B32 (early MG V), Hartz 6255 (early MG VI), Delta and Pine Land 6880 (late MG VI), and Hartz 7550 (mid‐MG VII) were seeded at 370 000 seeds ha−1 and at the recommended rate of 620 000 seeds ha−1. Total seed yield of all cultivars was usually similar for the two seeding rates. Less seed yield from the main‐stem fraction with the lower seeding rate was usually compensated for by a higher seed yield from the branch fraction, except when insufficient rainfall occurred during critical periods of the growing season. Branch seed yield was more closely correlated with total seed yield at the low seeding rate (r = 0.675) than at the recommended seeding rate (r = 0.453) while the correlation between total seed yield and seed yield from the main‐stem fraction was similar for the two seeding rates (r = 0.579–0.613). In the absence of prolonged periods of drought stress, seeding rates for glyphosate‐resistant soybean grown in full‐season, narrow‐row systems can be reduced below current recommendations, thereby lowering seeding costs without decreasing seed yields.
Gypsum and Compost Effects on Sugarcane Root Growth, Yield, and Plant Nutrients
Authors: Viator R. P. , Kovar J. L. , Hallmark W. B.
Published: July 2010

Louisiana sugarcane (Saccharum spp.) is produced mainly on heavy‐textured soils that offer less than ideal conditions for growth and function of the root system. Cultural practices that improve the soil environment could benefit sugarcane production by increasing root growth and reducing the incidence of ratoon decline. The objective of our research was to determine the effect of gypsum and composted, municipal‐biosolids application on root growth, crop yields, and leaf nutrient concentrations of sugarcane grown on a silty clay loam soil. Gypsum mixed into the rows at 2.24, 4.48, and 8.96 Mg ha−1 did not affect (P > 0.05) root growth or cane and sugar yields. Likewise, both subsoil‐ and within‐row applied compost at a rate of 44.8 Mg ha−1 did not affect cane or sugar yields compared with the control. Gypsum increased Ca, S, Mn, and Zn leaf concentrations, but had no effect on N, P, K, Mg, Cu, and Fe concentrations. Subsoil and within‐row compost increased leaf S concentration; within‐row compost increased leaf K; and subsoil compost increased leaf Zn, but reduced leaf Mn compared with the control. Compost application did not increase Mn, Cu, Fe, or Zn concentrations in sugarcane leaf tissue beyond acceptable limits. Within‐row applied compost reduced (P < 0.05) root surface area compared with the control, and reduced sugar yields compared with the subsoil compost treatment. This suggests that, at the compost rate used in our study, subsoil rather than within‐row application of compost, is the preferred practice for sugarcane grown on this soil.
Planting Time For Early‐Season Pearl Millet and Grain Sorghum in Nebraska
Authors: Pale Sìebou , Mason Stephen C. , Galusha Tom D.
Published: July 2010

Pearl millet [Pennisetum glaucum (L.) R. Br.] is a potential crop for the Great Plains, but there are few studies on production practices. The research objective was to determine the optimal planting time for pearl millet in Nebraska relative to sorghum [Sorghum bicolor (L.) Moench]. This would optimize pearl millet yields, thus increasing the prospect for pearl millet as a crop. Studies were conducted on Sharpsburg silty clay loam (fine, smectitic, mesic, Typic Argiudoll) and Ortello sandy loam (coarse‐loamy, mixed, mesic, Udic Haplustoll) soils between 1995 and 2001. Optimal planting times were determined by relating yields with calendar date, cumulative air heat units, cumulative soil heat units, and soil temperatures. Relative yields related to air or soil heat units were effective in determining the optimal planting time. Optimum pearl millet planting times were 399 air heat units or 410 soil heat units after 1 April for the Sharpsburg soil and 406 soil heat units for the Ortello soil. The optimal sorghum planting time was 308 air heat units or 307 soil heat units after 1 April for the Sharpsburg soil and 402 air heat units after 1 April for the Ortello soil. Both crops had large planting time windows, allowing flexibility in planting time. Sorghum outyielded pearl millet for May and early‐to mid‐June planting times by 0.57 to 2.32 Mg ha−1 while pearl millet had higher yields by 0.95 to 1.20 Mg ha−1 for late June and July planting times. Sorghum produced greater yields than pearl millet for most planting times while pearl millet produced greater yields than sorghum for very late planting times.
Dynamics of Competition between Wheat and Oat
Authors: Cousens Roger D. , Rebetzke Greg J. , Barnett Allan G.
Published: July 2010

Previous studies in the United Kingdom (UK) and Australia have led to the hypotheses that reversals in competitive hierarchy between wheat (Triticum aestivum L.) and oat (Avena spp.) could occur only in situations in which (i) there is a reversal in the relative heights of the competitors during the year and (ii) there is strong competition for light. Reversals in competitive hierarchy should not, therefore, occur where the wheat is either taller or shorter than oat throughout growth. We grew near‐isogenic lines of wheat for height in monoculture and in replacement mixtures with oat (A. sativa L. and A. strigosa Schreb.) in 2 yr. In the drier year and with a late‐maturing oat cultivar, height of wheat had no influence over its competitive superiority, which was maintained throughout the season. In a somewhat wetter year and with an earlier‐maturing oat cultivar, the shortest wheat lines were less competitive than corresponding taller near‐isolines. Results were consistent for near‐isogenic lines in three contrasting genetic backgrounds. Partial reversals in competitive hierarchy were seen in a late sowing, but these did not correspond with patterns in the relative height growth of the species.
A SMALL‐PLOT SEEDER AND FERTILIZER APPLICATOR
Authors: Engel Richard E. , Fischer Thomas , Miller John , Jackson Grant
Published: July 2010

Cereal grain investigators frequently include multiple cultivars and fertility levels in field experiments. Greater flexibility in experimental design and setup could be achieved with equipment that enables quick changes in cultivar and fertilizer rates from one plot to the next. A small‐plot seeder was constructed to meet this objective. The unit consists of the following basic components: the hitch, a tool‐bar for pulling a set of six blade coulter or fertilizer knives, a squeeze pump for liquid fertilizer applications, an operators chair and work rack, two belt cones for granular fertilizer and seed distribution, a grain box, and a set of six double‐disc or spear‐point openers plus press wheels. The seeder (794 kg) currently is being pulled with a 41 kW tractor, and has been successfully used in no‐till applications with blade coulters mounted on the front tool‐bar. Under normal conditions two people can fertilize and seed 60 plots (7–10 m long) in 1 h changing crop cultivars–species, fertilizer sources (granular material only), and fertilizer rates.
Modeling Sensible and Latent Heat Transport in Crop and Residue Canopies
Authors: Campbell G. S.
Published: July 2010

Modeling of latent and sensible heat exchange in crop and residue canopies is complicated by the fact that the equations for the two processes are strongly coupled and require simultaneous solution. We derive a set of uncoupled equations where the new fluxes are enthalpy and isothermal latent heat and the new driving forces are equivalent temperature and vapor pressure deficit. The canopy network equations, using the new driving variables, are reduced, using Thevenin's theorem, to a single potential and a single resistance for each flux.
Weed and Insect Communities in Wheat Crops with Different Management Practices
Authors: de la Fuente Elba B. , Suárez Susana A. , Ghersa Claudio M.
Published: July 2010

Biotic adjustments to changes in crop management practices are reflected in the presence or absence of weed and insect populations. The pattern of response and the causes that drive them are important to reveal the main factors involved in molding the structure of an agroecosystem and its dynamics. In this study, weed and insect communities were characterized in wheat (Triticum aestivum L.) crops from the Rolling Pampas with different cropping histories. Surveys were performed in fields that were selected randomly from those located on highlands with typical Argiudol soils and cultivated with conventional tillage. Fields, weeds, and insects were classified with cluster analysis, and weed and insect associations were determined using agronomic variables with canonical correspondence analysis (CCA). The classification of the data resulted in six floristic groups and seven insect groups that characterized different weed and insect communities. Three weed and insect communities associated with the number of years with annual cropping after a pasture that lasted for several years, the duration of wheat crop cycle, and soybean as a preceding crop were identified.
Weed Management in Nonirrigated Glyphosate‐Resistant and Non‐Resistant Soybean following Deep and Shallow Fall Tillage
Authors: Heatherly Larry G. , Spurlock Stan R. , Reddy Krishna N.
Published: July 2010

Management inputs that maximize economic return from the early plantings of soybean [Glycine max (L.) Merr.] in the midsouthern USA have not been evaluated fully. The objective was to compare perennial weed control in and yields and economic returns from plantings of maturity group (MG) IV and V soybean cultivars grown in the field under different weed management systems (WMS) following shallow (ST) and deep (DT) fall tillage. Adjacent experiments were conducted on Tunica clay (clayey over loamy, smectitic, nonacid, thermic Vertic Haplaquept) near Stoneville, MS (lat. 33°26′N). Weed management systems were (i) glyphosate [N‐(phosphonomethyl)glycine]‐resistant (GR) cultivars with preemergent (PRE) nonglyphosate herbicides followed by postemergent (POST) glyphosate; (ii) GR cultivars with POST glyphosate; (iii) non‐GR cultivars with PRE plus POST nonglyphosate herbicides; and (iv) non‐GR cultivars with POST nonglyphosate herbicides. Control of perennial redvine [Brunnichia ovata (Walt.) Shinners] declined in the ST environment when non‐GR cultivars were used, but this did not result in a yield decline. Control of perennial johnsongrass [Sorghum halepense (L.) Pers.] at the end of the study period averaged <40% when non‐GR cultivars were used and >93% when GR cultivars were used regardless of tillage treatment, and this was associated with lower yield. Use of PRE + POST vs. POST‐only weed management sometimes resulted in lower profits regardless of fall tillage treatment. The fall tillage treatment × WMS interaction was not significant for yield or net return, which indicates that use of DT for perennial weed management is not economical.
Germination Characteristics of Polymer‐Coated Canola (Brassica napus L.) Seeds Subjected to Moisture Stress at Different Temperatures
Authors: Willenborg Christian J. , Gulden Robert H. , Johnson Eric N. , Shirtliffe Steven J.
Published: July 2010

Polymer coatings have recently been developed to prevent germination and thereby reduce undesirable emergence of fall‐seeded canola (Brassica napus L.) in western Canada. However, recent observations suggest that if seeds are not exposed to moist soil conditions in the fall, these polymer coats may prevent imbibition and subsequent germination during the following spring. Our objective was to determine the effects of moisture stress and polymer coat on canola seed germination characteristics in the laboratory. Polymer‐coated and non‐polymer‐coated canola seeds were germinated in polyethylene glycol (PEG 8000) solutions with initial osmotic potentials ranging from 0 to −1.25 MPa at 5 and 15°C. Polymer coat treatments caused higher median germination times and lower final germination percentages compared with film‐coated and uncoated control seeds. Germination characteristics of polymer‐coated seeds were negatively influenced by decreasing initial osmotic potential, particularly at 5°C. Although not always significantly different from the uncoated control, film‐coated control seeds behaved similarly to those coated with polymers. Among the three polymer coat treatments examined, one polymer coat treatment consistently exhibited higher germination compared with the other two. The results of this study help explain the occurrence of low spring seedling populations of fall‐seeded, polymer‐coated canola following a dry fall, particularly under low spring soil temperatures.
Barley Biomass and Grain Yield and Canola Seed Yield Response to Land Application of Wood Ash
Authors: Patterson Shane J. , Acharya Surya N. , Thomas James E. , Bertschi Al B. , Rothwell Richard L.
Published: July 2010

Wood ash is considered a waste product that accumulates from the burning of wood waste for energy production. Field studies were conducted on acidic Boralf and Eutrochrept soils and in the greenhouse using material from the surface of these soils in randomized complete block designs to evaluate the effectiveness of wood ash as a liming material for improving crop production. For the greenhouse study, soil was treated with the equivalent of 0 to 200 t ha−1 (w/w) wood ash. Barley (Hordeum vulgare L.) yielded up to 50% more dry matter in this study. Based on these findings, a 3‐yr field study was done to determine the effect of single applications of 6, 12.5, and 25 t ha−1 wood ash to Boralf soils in central Alberta. Significant increases in barley dry matter and grain yield and oil seed yields of canola (Brassica rapa L.) were observed when soil was supplemented with 12.5 or 25 t ha−1 along with N fertilizer. Increases of 72 and 50% in barley dry matter and grain yield were observed while canola oilseed yield increased 124% due to wood ash application. Applications up to 25 t ha−1 did not have a deleterious effect on biomass or seed production in barley or canola crops. Results show that land application of wood ash increased pH and nutrient content of acid soils while having a beneficial effect on crop production. Land application of wood ash can provide timber companies with a viable alternative to landfill disposal.
A HYDRAULIC CORING SYSTEM FOR SOIL‐ROOT STUDIES
Authors: Prior S. A. , Runion G. B. , Torbert H. A. , Erbach D. C.
Published: July 2010

Reliable sampling of belowground components in the field is essential to agroecosystem research. Factors such as hardpans and dry soil conditions often increase sampling time and impede adequate sampling. The objective was to design and construct a soil coring system for rapid field sampling that minimized such limitations. Cores were extracted using a custom‐made telescoping hydraulic cylinder device assisted by a hydraulic post driver mounted to the front of a small tractor. The telescoping device inserted the core tube into the ground, and the post driver was activated only when insertion had been slowed or stopped. The tractor's hydraulics powered the telescoping device and the post driver; both were controlled by the tractor operator. Custom driving heads were constructed to fit the upper end of core tubes to collect large‐diameter soil samples (25 cm diam. by 0.6 m deep) or small samples (3.8 cm diam. by 1.0 m deep). As many as 14 large cores or 24 small cores per hour could be collected with this system. The coring system has been successfully used on various soil types and to sample both agricultural and forest sites for a number of experimental objectives.
Impact of Defoliation on Corn Forage Yield
Authors: Lauer J. G. , Roth G. W. , Bertram M. G.
Published: July 2010

Farmers, agronomists, and crop insurance adjusters question whether leaf defoliation damage caused by hail or other factors affects corn (Zea mays L.) forage yield the same as grain yield. Our objective was to evaluate the effects of defoliation on corn grown for forage production. In studies conducted during 3 yr at two sites in Wisconsin and one site in Pennsylvania, forage yield decreased as leaf removal increased in severity, and as time of defoliation neared silking. Forage yield response to increasing levels of defoliation was quadratic. Averaged across all environments, forage yield decreased 16% when 100% defoliation occurred at V7. Likewise 100% defoliation decreased forage yield 43, 70, and 40% at V10, R1, and R4 growth stages, respectively. Greater forage yield decreases are measured with early defoliation (V7–V10) than predicted grain yield decreases currently used by hail adjusters. This likely occurred because both increased leaf removal and decreased grain yield combine to reduce forage yield. The response to defoliation from simulated hail damage is different between corn forage and corn grain. Alternative predictive models for estimating forage yield losses should be used by insurance adjusters.
Water Use and Root Length Density of Cuphea spp. Influenced by Row Spacing and Sowing Date
Authors: Sharratt Brenton S. , Gesch Russ W.
Published: July 2010

Cuphea (Cuphea viscosissima Jacq. × C. lanceolata f. silenoides W.T. Aiton) is a potential new crop, but little is known concerning best agricultural management practices for this crop in temperate regions. A field study was initiated in Minnesota to determine the impact of sowing date and row spacing on soil water use and rooting characteristics of Cuphea spp. Cuphea spp. were sown on 4, 18, and 30 May 2001 and 30 April, 14 May, and 28 May 2002 in rows 200, 400, and 600 mm apart. Aboveground biomass, seed yield, and water use were bolstered by sowing Cuphea spp. in late April or early May rather than in late May. Water use for early sown and late‐sown Cuphea spp. was respectively 366 and 311 mm. Sowing date also influenced water use efficiency (WUE) but only in 2002 when WUE of early sown and late‐sown Cuphea spp. was respectively 1.87 and 1.64 kg ha−1 mm−1. Sowing earlier in the spring also bolstered root growth as root length density in the upper 0.2 m of the soil profile was 24 km m−3 for the early sowing and 17 km m−3 for the late sowing. Row spacing did not affect seed yield, water use, or root length. This study indicates that biomass, seed yield, water use, and root growth of Cuphea spp. are favored by sowing early in the spring. Although early sowing resulted in greater water use, a tendency existed for Cuphea spp. to utilize water more efficiently in seed production when sown earlier in the spring.
Modeling Diurnal Canopy Temperature Dynamics Using One‐Time‐of‐Day Measurements and a Reference Temperature Curve
Authors: Peters R. Troy , Evett Steven R.
Published: July 2010

The application of the temperature–time threshold (TTT) method of irrigation scheduling to self‐propelled irrigations systems requires a method of estimating the diurnal canopy temperature dynamics using only a one‐time‐of‐day measurement. Other research efforts such as the crop water stress index (CWSI) and field canopy temperature mapping using moving irrigation systems could also be served by the use of this method. This was accomplished using a stationary reference measurement to capture the canopy temperature dynamics. Two different methods were developed for estimating a temperature curve for a remote location from a one‐time‐of‐day measurement at that location. The first method (scaled method) uses the ratio between the reference temperature and the remote location temperature, referenced to the predawn temperature, to scale the reference curve to yield the predicted curve. In the second method (Gaussian difference method), a three‐parameter Gaussian equation was empirically fitted to the temperature differences between the reference and the measured remote canopy temperature curves. To test these two methods, canopy temperature data, sensed using stationary infrared thermometers, from three different crops {corn (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean [Glycine max (L.) Merr.]} were analyzed. For a few hours after dawn and before sunset, the scaled method was generally more accurate while during the middle of the day, the Gaussian difference method was more accurate. The average absolute value of the error between the predicted and actual temperatures from the best of both methods during daylight hours was roughly 0.5°C. For all 3 yr, the total irrigation for a season using the extrapolated temperatures were within 18 mm on average of those actually scheduled using the TTT method and measured data.
Large‐Scale Assessment of Symbiotic Dinitrogen Fixation by Crops: Soybean and Alfalfa in the Mississippi River Basin
Authors: Russelle Michael P. , Birr Adam S.
Published: July 2010

Human activities have increased the amount of earth's reactive N, resulting in significant improvements in crop yield and animal production but also in environmental degradation and ecosystem disruption in some areas. For example, agriculture has been cited as a major source of N that contributes to hypoxia in the Gulf of Mexico. Although other sources of N have been well characterized in large ecosystem studies, the contribution of legume crops to the N cycle has not. Furthermore, the role legumes play in reducing excess N is not widely recognized. Symbiotic N2 fixation is a facultative process that is reduced by plant N uptake from other sources. Using reported and estimated crop yield and protein concentration with published estimates of soil N mineralization and atmospheric N deposition, we estimated spatial patterns of symbiotic N2 fixation for soybean [Glycine max (L.) Merr.] and alfalfa (Medicago sativa L.) across the Mississippi River Basin, the largest in North America. We estimate that alfalfa haylage adds about 20% to total production of dry alfalfa hay and increases total land area in alfalfa by about 11% over that reported in the Census of Agriculture. Our analysis shows wide ranges in N2 fixation (0 to 185 kg N ha−1 for soybean and 45 to 470 kg N ha−1 for alfalfa), reasonable mean rates (84 kg N ha−1 for soybean and 152 kg N ha−1 for alfalfa), and suggests that about 2.9 million Mg of fixed N is harvested annually in these two cultivated legumes.
Sunn‐Hemp Utilized as a Legume Cover Crop for Corn Production
Authors: Balkcom Kipling S. , Reeves D. Wayne
Published: July 2010

The benefits of winter legumes as cover crops for corn (Zea mays L.) are diminished by the earliness of corn planting in relation to biomass and N production by the legumes. Tropical legumes may offer an alternative to winter legumes because they produce adequate biomass before corn planting. We determined the suitability of ‘Tropic Sunn’ sunn‐hemp (Crotalaria juncea L.) as a cover crop for corn on a Compass loamy sand (coarse‐loamy, siliceous, subactive, thermic Plinthic Paleudults) in central Alabama using a split‐plot treatment structure in a randomized complete block design with four replications from 1991 to 1993. Main plots were winter fallow and sunn‐hemp planted in mid‐August, and subplots were N (0, 56, 112, and 168 kg N ha−1) applied to corn 3 weeks after planting (WAP). Sunn‐hemp biomass production approximately 14 WAP (first frost) averaged 7.6 Mg ha−1 with an N content of 144 kg ha−1 in the first 2 yr of the study. Corn grain yield following sunn‐hemp averaged 6.9 Mg ha−1 whereas yield following winter fallow averaged 5.7 Mg ha−1. Grain N averaged 16.3 kg ha−1 greater for corn following sunn‐hemp than fallow plots. Before first frost, sunn‐hemp produced excellent biomass to serve as a winter cover crop in corn production while producing N equivalent to 58 kg ha−1 of N fertilizer during the 3‐yr period, based on corn yield and N response. Sunn‐hemp has potential to be utilized as an alternative to winter legumes for ground cover and as an N source for a subsequent corn crop in the Southeast.
Soil Heat Storage Measurements in Energy Balance Studies
Authors: Ochsner Tyson E. , Sauer Thomas J. , Horton Robert
Published: July 2010

Energy balance studies require knowledge of the heat flux at the soil surface. This flux is determined by summing the heat flux at a reference depth (zr) some centimeters below the surface and the rate of change of heat storage in the soil above zr. The rate of change of heat storage, or heat storage for short (ΔS), is calculated from soil volumetric heat capacity (C) and temperature. The objectives of this study were to determine how choices regarding zr, C measurements, and ΔS calculations all affect the accuracy of ΔS data. Heat transfer theory and data from three field sites were used toward these ends. In some studies, shallow reference depths have been used and ΔS neglected. Our results indicate that when zr is sufficiently deep to permit accurate heat flux measurements, ΔS is too large to neglect. Three methods for determining C were evaluated: soil sampling, the ThetaProbe soil moisture sensor, and heat pulse sensors. When C was determined using all three methods simultaneously, the estimates agreed to within 6% on average; however, the temporal variability of C was best recorded with the automated heat pulse sensors. Three approaches for calculating ΔS were also tested. The common approach of letting C vary in time but neglecting its time derivative caused errors when soil water content was changing. These errors exceeded 200 W m−2 in some cases. The simple approach of assuming a constant C performed similarly. We introduce a third approach that accounts for the time derivative of C and yields the most accurate ΔS data.
Using On‐Farm Data to Validate Crop Management Recommendations and Implementation
Authors: Pruss J. A. , Beegle D. B. , Turgeon A. J. , Day R. L. , Weaver R. D.
Published: July 2010

Although farmers are encouraged to collect field‐specific crop management data to optimize on‐farm decisions, farm‐derived data are often discounted as a source of information for making broader management and environmental evaluations. This study was conducted to illustrate the use of on‐farm data for validating management recommendations and implementation. Data collected by farmers and crop management consultants from 1997 to 2000 from 1119 central Pennsylvania fields were used to evaluate the impact of soil series, potentially available added N (PAAN), and rainfall on corn (Zea mays L.) yield, N required to produce a unit of grain, and PAAN in excess or deficit of crop requirement. Results showed that although observed yields generally followed the same relative ranking as the established soil series yield capabilities, they were consistently lower by 13 to 30%. Also, the amount of PAAN per kilogram of corn grain observed was relatively consistent with PAAN recommendations for the most productive soils and about 25% higher for the least productive soils. Actual PAAN was on average 28 kg ha−1 higher than PAAN recommended for observed yields. The higher actual PAAN could be due to the difference between observed yields and established yield capabilities used by farmers to determine PAAN recommendations. Because data also showed that rainfall had a significant effect on observed yields, the inability to predict rainfall was another major cause for the difference between actual and recommended PAAN. The analysis showed the database was useful for evaluating corn yields and N management and confirmed that N practices are generally consistent with recommendations.
Establishment of Kura Clover No‐Tilled into Grass Pastures with Herbicide Sod Suppression and Nitrogen Fertilization
Authors: Laberge Guillaume , Seguin Philippe , Peterson Paul R. , Sheaffer Craig C. , Ehlke Nancy J. , Cuomo Gregory J. , Mathison Russell D.
Published: July 2010

Sod‐seeding legumes into grass‐dominated pastures improve forage productivity and quality. Identical field experiments were established in May 2001–2002 at two sites in Québec and three in Minnesota. Our objective was to compare the establishment in perennial cool‐season grass sods of two sod‐seeded cultivars (‘Cossack’ and ‘Endura’) of Kura clover (Trifolium ambiguum M.B.) against that of red clover (Trifolium pratense L.) and white clover (Trifolium repens L.) using different herbicide sod suppression intensities {paraquat, 1,1'‐dimethyl‐4,4'‐bipyridinium (0.9 kg a.i. ha−1) and glyphosate [N‐(phosphonomethyl) glycine] (0.8 or 3.3 kg a.i. ha−1)}, without or with N fertilization (110 kg N ha−1). Establishment year plant density and dry matter (DM) production of both Kura clover cultivars were similar (avg. 90 plants m−2, 390 kg DM ha−1), but were generally inferior to white clover (avg. 110 plants m−2, 740 kg DM ha−1) and red clover (avg. 170 plants m−2, 1450 kg DM ha−1). Paraquat did not sufficiently suppress the sod, resulting in lower legume populations and yields than glyphosate. Sod suppression using glyphosate, however, led to heavy seeding‐year weed infestation at two of three sites in Minnesota (avg. 2.2 Mg weed DM ha−1). Sod‐seeded Kura clover successfully established with glyphosate; however, its contribution to forage production in the sod‐seeding year remained minimal (<0.5 Mg ha−1 at four of five sites). Effects of N fertilization varied with species and herbicides; effects on Kura clover were inconsistent but rarely detrimental, while increasing total forage yields by an average of 40%. It is thus possible to establish Kura clover via sod‐seeding; however, its productivity in the seeding year remains minimal.
Crop Sequencing to Improve Use of Precipitation and Synergize Crop Growth
Authors: Tanaka D. L. , Anderson R. L. , Rao S. C.
Published: July 2010

Cropping systems will not be sustainable without change. Broad‐scope problems associated with developing sustainable cropping systems are how to choose and sequence crops in cropping systems. Our objectives were twofold: (i) evaluate impacts of crop sequencing on precipitation use and (ii) show how crop sequencing can accentuate synergistic interactions among crops. Crop–fallow systems that developed in the Great Plains resulted in precipitation storage efficiencies of about 20% in the early 1930s to about 40% in the late 1980s. Integrated crop–livestock systems have been developed in the southern Great Plains to take advantage of bimodal annual precipitation pattern to produce high quality pigeonpea [Cajanus cajan (L.) Millsp.] forage during the noncrop period between winter wheat (Triticum aestivum L.) harvest and seeding. Pigeonpea can be grown after a mid‐June winter wheat harvest since pigeonpea uses precipitation received from wheat harvest to late September and pigeonpea has a root system that allows it to use soil water below the effective rooting depth of wheat. In the central Great Plains, water‐use efficiency of winter wheat was improved 18 to 56% by including broadleaf crop in a grass‐based rotation. Cropping systems in the northern Great Plains tend to be more diverse, and research at Mandan, ND, suggests that seed yield of flax (Linum usitatissium L.) can be tripled with a safflower (Carthamus tinctorius L.)–flax crop sequence vs. a flax–flax crop sequence. Great Plains cropping systems of the future will not only need to take advantage of crop sequences through synergism, but also take advantage of the interactions associated with diversity in space (polyculture).
Weed Management in Glyphosate‐Resistant and Non‐Glyphosate‐Resistant Soybean Grown Continuously and in Rotation
Authors: Heatherly Larry G. , Reddy Krishna N. , Spurlock Stan R.
Published: July 2010

Management inputs that maximize economic return from the early soybean [Glycine max (L.) Merr.] production system have not been evaluated fully. Field studies were conducted near Stoneville, MS (33°26′ N lat.), to determine the effect of rotating maturity group (MG) IV and V glyphosate [N‐(phosphonomethyl)glycine]‐resistant (GR) and non‐GR cultivars on weed populations, soybean seed yields, and net returns from nonirrigated plantings. Eight management systems, each containing a MG IV or MG V GR or non‐GR cultivar grown continuously or in rotation with each other, and two weed management treatments [pre‐emergent followed by postemergent weed management (PRE + POST) and postemergent‐only weed management (POST)] were grown each year. Glyphosate‐resistant cultivars using POST‐only glyphosate was the most economical system each year. Maturity group effect on yield and net return resulted from weather differences during reproductive development. Rotating GR and non‐GR cultivars had no consistent effect on weed populations and no significant effect on yield or net return in this 4‐yr study. Using GR cultivars resulted in net returns that were greater than those from non‐GR cultivars. These results indicate that production systems using either GR or non‐GR cultivars grown continuously or in rotation with each other in this region can be utilized effectively with no effect on weed population shifts or reductions in seed yield and net return.
Tillage System, Preceding Crop, and Nitrogen Fertilizer in Wheat Crop: I. Soil Water Content
Authors: López‐Bellido Rafael J. , López‐Bellido Luis , Benítez‐Vega Jorge , López‐Bellido Francisco J.
Published: July 2010

Under rainfed Mediterranean conditions, water economy must be based on a suitable choice of agronomic techniques. A 6‐yr study was undertaken to determine the effects of tillage system, preceding crop, and N fertilizer on soil water at wheat (Triticum aestivum L.) planting and harvest in a Vertisol. Tillage treatments were no‐tillage and conventional tillage. Preceding crops, in 2‐yr rotations, were sunflower (Helianthus annuus L.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L.), fallow, and continuous wheat. Nitrogen fertilizer rates were 0, 50, 100, and 150 kg N ha−1 applied to wheat only. No‐tillage did not provide more water at wheat planting for any of the rotations. Preceding crop effect on soil water content (SWC) at planting was as follows: fallow ≥ faba bean > wheat ≥ chickpea > sunflower. At harvest, SWC was higher in continuous wheat. Only at harvest were there differences among N fertilizer rates for SWC. Besides, measurement of SWC at harvest for sunflower, chickpea, faba bean, and fallow were performed to determine soil water storage and precipitation storage efficiency (PSE) for 2 yr. Soil water storage was higher for rotations with sunflower or fallow. Nevertheless, fallow PSE was the lowest (10%). The mean PSE was 29%. Under the conditions of this study, no‐tillage is not more efficient than conventional tillage in soil water accumulation. Fallow is not a useful tool for increasing water availability.
Relation of Available Potassium to Soil Moisture
Authors: Luebs R. E. , Stanford G. , Scott A. D.
Published: July 2010

Preliminary studies revealed that exchangeable K levels in Iowa soils fluctuated in response to vapor pressure changes and air drying. This phenomenon was investigated in relation to (1) K nutrition of plants in the greenhouse and (2) the problem of predicting the relative K‐fertility status in a wide range of Iowa soils. The thirteen soils employed in the greenhouse study showed variable increases in exchangeable K content upon air drying. Accompanying increases occurred in K uptake by the corn plants. Effects on K absorption by plants associated with drying of the soils often were equivalent to applying 60 to 120 lbs. K per 2 million lbs. of soil.

Relative ability of the soils to supply K to plants under green‐house conditions was better correlated with exchangeable K content of undried than of air dried soils. This was true whether or not soils were air dried for cropping.

Under field conditions, fluctuations in soil moisture levels in the surface one‐inch layer were accompanied by marked changes in content of exchangeable K over an 11‐week period. Below this layer, exchangeable K remained nearly constant since moisture content did not drop so low as in the surface. Results obtained in both field and laboratory showed that not much increase in exchangeable K occurred until soil moisture level had dropped to near 5 per cent or below. On the basis of overall results obtained it is concluded that for Iowa soils exchangeable K values determined after air drying may not be as reliable as those determined on moist soils, in predicting K supplying abilities of soils. Additional field studies are needed, however, to evaluate effects of alternate drying and wetting of soil on K nutrition of the crop.