bluuebunny/crossref_metadata_2025 huggingface dataset:
Crop Rotation with Tagetes sp. is an Alternative to Chemical Fumigation for Control of Root‐Lesion Nematodes
Authors: Reynolds L.Bruce , Potter John W. , Ball‐Coelho Bonnie R.
Published: July 2010

The root‐lesion nematode (Pratylenchus penetrans Cobb) is a significant pest of many crops in Ontario. For example, more than 25 000 ha of land cropped to flue‐cured tobacco (Nicotiana tabacum L.) is fumigated annually at a mean cost for the fumigant materials alone of $484 ha−1. The objectives of these trials were to develop and evaluate a marigold (Tagetes sp.) rotation cropping system for the biological control of root‐lesion nematodes. In 1995 (site A) and 1996 (site B), field plots of Tagetes patula L. cv. Creole and Tagetes erecta L. cv. CrackerJack were established as rotation crops in comparison with the traditional rye rotation crop plus chemical fumigation prior to transplanting flue‐cured tobacco. Within 75 d of seeding marigold, P. penetrans population densities were reduced to less than 100 kg−1 soil, below the economic threshold of 500 P. penetrans kg−1 soil for tobacco. A marigold plant density of about 20 plants m−2 reduced P. penetrans population densities to levels below the economic threshold for the rotation crop year and the two following years. Tobacco yield was increased by a mean of 197 kg ha−1 by marigold rotation crops compared with rye plus chemical fumigation. The seed cost for a marigold crop at 20 plants m−2 varied from $221 ha−1 for T. patula to $294 ha−1 for T. erecta This new cropping system for the biological control of root‐lesion nematodes is a functional alternative to chemical fumigation for Ontario flue‐cured tobacco growers.
Optimizing Wheat Harvest Cutting Height for Harvest Efficiency and Soil and Water Conservation
Authors: McMaster Gregory S. , Aiken Robert M. , Nielsen David C.
Published: July 2010

Winter wheat (Triticum aestivum L.) productivity is frequently limited by water availability and degraded by wind erosion. Managers of harvest operations must balance soil and water‐conservation benefits of maintaining sufficient stubble height with the risk of losing grain yield due to unharvested spikes below the combine cutting height. This study calculated the relationship between expected harvest losses and conservation of soil and water at various combine cutting heights. Mature wheat spike height frequency distributions for 5 yr were collected for different tillage and residue‐cover levels. Wind‐velocity profiles were measured for different stem frequencies and heights at three sites with harvested wheat stubble. Potential evaporation of water was calculated by PENFLUX, a Penman‐type energy balance model. Potential soil loss was computed from the relative friction velocity (RFV). Stem heights were generally normally distributed, regardless of year or treatment. Quantifying RFVs at the soil surface and relative evaporation rates showed that combine cutting heights <0.1 m offered little protection from erosive winds for sparse stands with <280 stems m−2. Higher cutting heights of 0.3 or 0.5 m increased protection, especially for sparse stands, but the relative benefits of increasing stem frequencies declined with higher cutting heights. Under normal sowing rates and conditions, harvesting wheat with a cutting‐type header at two‐thirds of its height will give 80% of the maximum soil and water conservation protection. Harvesting with a stripper‐header combine attachment might be a potential new technology to further maximize soil and water conservation while minimizing harvest losses.
Nonstructural Carbohydrates in Tall Fescue Cultivars: Relationship to Animal Preference
Authors: Mayland Henry F. , Shewmaker Glenn E. , Harrison Philip A. , Chatterton N. Jerry
Published: July 2010

Grazing animals prefer some plants to others. These choices are likely related to physical and chemical factors such as energy‐dense carbohydrates contained in plants. This study quantified the nonstructural carbohydrate fractions in each of eight vegetatively growing, endophyte‐free, tall fescue cultivars (Festuca arundinacea Schreb.) and relates their sugar concentrations to cattle grazing preferences. The experimental area consisted of eight cultivar plots replicated three times in each of three pastures. Within each pasture, forage was sampled between 0830 and 1000 h mountain daylight time (MDT) during each of four seasons and 2 yr. Freeze‐dried forage samples were extracted with hot water and an amylase (Clarase) solution. Sugars were quantified colorimetrically using potassium‐ferricyanide and glucose‐oxidase methods. Cattle grazing preferences among these tall fescue cultivars were related to the concentrations of total nonstructural carbohydrates (TNC) Other sugar fractions were not significantly related to grazing preference in this study. The nonstructural carbohydrate concentrations averaged over the entire study were glucose, 14; fructose, 5; sucrose, 40; fructan, 23; insoluble starch, 24; and TNC, 129 g kg−1. A forage selection criterion should include measures of the TNC because of their close relationship to animal grazing preference.
Joint Multifractal Analysis of Crop Yield and Terrain Slope
Authors: Kravchenko Alexandra N. , Bullock Donald G. , Boast Charles W.
Published: July 2010

Quantifying the spatial variability of crop yields and yield‐affecting factors are important issues in precision agriculture. Topography is frequently one of the most important factors affecting yields, and topographical data are much easier to obtain than time and labor‐consuming measurements of soil properties. In this study, yield variability and the relationships between yields and terrain slopes were analyzed using theories of multifractal and joint multifractal measures. Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yield data from 1994 to 1998 were collected via yield monitors from a central 6.6 ha section of an agricultural field in eastern Indiana. Slopes were derived from a field terrain map using a GIS. Multifractal analysis of yield and slope maps revealed that both yield and slope distributions were multifractal measures. Hence, joint multifractal analysis was applied to evaluate the effect of slope on crop‐yield spatial variability. Joint multifractal analysis facilitated (i) the ability to differentiate between yield distributions corresponding to field locations with high and low slopes, and (ii) the ability to make inferences about slope distributions that affect grain yield the most. Multifractal analysis revealed that during four growing seasons with moderate and dry weather conditions, larger yields were observed at low slope locations while a wide range of yield values was observed at sites with moderate and high slopes. During the wet growing season, lower yields prevailed at locations with low slopes. Joint multifractal theory was useful for the study of yield/topography relationships and was an applicable tool for the analysis of spatially distributed data.
Season‐Long Characterization of Vertical Distribution of Leaf Area in Corn
Authors: Boedhram Nandkishor , Arkebauer Timothy J. , Batchelor William D.
Published: July 2010

Amount and vertical distribution of leaf area are essential for estimating radiation interception for canopy photosynthesis modeling. The objective of this study was to quantify vertical distribution of leaf area in corn (Zea mays L.) during the entire growing season. Field experiments were conducted in 1994 and 1995 near Mead, NE. Treatments included irrigation vs. no irrigation and three N rates (0, 68, and 135 kg ha−1). A leaf‐dissecting device was built for accurate clipping and collection of leaves at 0.10‐m height intervals. A normal curve gave an excellent fit to measured vertical distributions of leaf area index (LAI) at 0.10‐m height intervals (r2 > 0.94), regardless of applied N, soil moisture, crop developmental stage, or year. It was concluded that corn LAI was distributed symmetrically in the vertical from crop emergence to maturity. Plots of LAI vertical distributions indicated not only the onset and magnitude of differences among treatments, but also how stress was shared among all canopy layers. Of the three fitted curve parameters, height of symmetry and measure of green‐canopy spread were good indicators of plant growth, but LAI in interval containing height of the symmetry axis was not. The existence of a symmetrical vertical distribution of LAI fulfilled the requirement for applying the three‐point Gaussian method of integration in corn.
Incorporating Bias Error in Calculating Solar Irradiance
Authors: Weiss Albert , Hays Cynthia J. , Hu Qi , Easterling William E.
Published: July 2010

Solar irradiance is an important input parameter to many crop simulation models. It is not measured at the same spatial density as air temperature and precipitation, which has lead to the development of algorithms to calculate solar irradiance from air temperature and precipitation data. Fourteen algorithms were evaluated using 10 yr of measured air temperature, precipitation, and solar irradiance data from Mead, NE. All algorithms had similar root mean square errors (RMSE). When the bias error (the difference between measured and simulated values) was plotted against day of year, only one version of the algorithm showed a simple pattern not dependent on fitting a Fourier series to the data. This pattern of the bias error formed the basis for a correction factor that was applied to all calculations of solar irradiance. Using independent meteorological data from nine locations in eastern and western portions of Kansas, Nebraska, and South Dakota, the corrected algorithm developed from the Mead data calculated solar irradiance with RMSE ranging from 3.6 to 4.7 MJ m−2 d−1. Using the Erosion Productivity Impact Calculator, simulated yields of wheat (Triticum aestivum L.), maize (Zea mays L.), and soybean [Glycine max (L.) Merr.] were significantly different when using the measured and uncorrected solar irradiance; however, the yields were not significantly different when using the measured and modified solar irradiance. Using this modification, solar irradiance measured at one location can be used to calculate solar irradiance at locations up to 600 km away in the U.S. Great Plains.
Rice Parameters Describing Crop Performance of Four U.S. Cultivars
Authors: Kiniry James R. , McCauley Garry , Xie Yun , Arnold Jeffrey G.
Published: July 2010

Parameters describing processes of crop growth and yield production provide modelers with the means to simulate crops and provide breeders with a system of comparing cultivars. Such values for rice (Oryza sativa L.) are especially important for some regions in the southern USA. Accordingly, the objective of this study was to quantify key biomass and yield production processes of four rice cultivars common in this region. We measured the leaf area index (LAI), the light extinction coefficient (k) for Beer's law, N concentrations, and the harvest index (HI) for the main and ratoon crops in 1999 and 2000 at Eagle Lake, TX. Dry matter was linearly related to intercepted photosynthetically active radiation (IPAR) for all of the data sets. The mean radiation use efficiency (RUE) was 2.39 g aboveground biomass MJ−1 IPAR. Maximum LAI values ranged from 9.8 to 12.7, and the mean k value for the main crop was 0.37. The highest main crop yields were 7.04 Mg ha−1 for Cocodrie in 1999 and 7.22 Mg ha−1 for Jefferson in 2000. Yield differences among cultivars were due to HI differences and were not related to RUE values. The mean HI was 0.32 for all four cultivars over the two harvests in each of the 2 yr. Consistency in values of RUE, k, N concentrations, and HI among the cultivars in this study and between this study and values reported in the literature will aid modelers simulating rice development and yield and aid breeders in identifying key traits critical to rice grain yield improvement.
Germination and Seedling Cold Tolerance in Sorghum
Authors: Tiryaki Iskender , Andrews David J.
Published: July 2010

Genetic improvement of sorghum [Sorghum bicolor (L.) Moench] for germination and seedling growth in cold conditions would permit earlier seeding, with a number of benefits. Field evaluation of germination and seedling cold tolerance, while ultimately necessary, is subject to unpredictable weather and limited to one period of the year. The objective of this study was to develop simple and reliable techniques capable of handling large numbers of genotypes, for estimating germination and seedling cold tolerance of sorghum in controlled environment, before field tests, and to compare results with seedling emergence in the field at low soil temperatures. Rate of germination, final germination percentage, and the rate of early shoot growth were evaluated as estimators of cold tolerance using 12 diverse genotypes and their test crosses. The largest difference among genotypes under both normal [25–30°C (day) and 20–25°C (night)] and cold stress conditions (constant 15°C) was shown by the rate of germination in petri dishes and of shoot growth in vertical plexiglass plates in normal conditions only. Rate of germination under controlled cold conditions was strongly correlated (P < 0.01) with rate of emergence in a field experiment seeded early in cold soil. This work indicated that the use of two tests under controlled conditions, (i) measuring shoot growth rate under normal temperatures followed by (ii) rate of germination at 15°C, and recording data at optimum times will greatly assist in efficiently screening genotypes for cold tolerance before final evaluation in the field.
Locating Genes Controlling Allelopathic Effects against Barnyardgrass in Upland Rice
Authors: Jensen Louise Bach , Courtois Brigitte , Shen Lishuang , Li Zhikang , Olofsdotter Maria , Mauleon Ramil P.
Published: July 2010

To understand the genetic control of allelopathy in rice (Oryza sativa L.), quantitative trait loci (QTL) mapping was performed using a population of 142 recombinant inbred lines derived from a cross between cultivar IAC 165 (japonica upland variety) and cultivar CO 39 (indica irrigated variety). The map contained 140 DNA markers. The relay seeding technique, which is a laboratory bioassay measuring the inhibition in weed root growth due to the presence of rice seedlings, was used to evaluate the allelopathic effect of the rice lines. Cultivar IAC 165 showed strong and consistent allelopathic activity against barnyardgrass [Echinochloa crus‐galli (L.) Beauv.], whereas CO 39 was weakly allelopathic. Transgressive segregation for allelopathic activity in both directions was observed in the population. No significant correlation was found between root morphology of the lines and their allelopathic potential, suggesting that allelopathy in rice was under genetic control independent from root morphology. Four main‐effect QTLs located on three chromosomes were identified, which collectively explained 35% of the total phenotypic variation of the allelopathic activity in the population. One pair of digenic epistatic loci, not involving any of the main‐effect loci, was also detected. Once confirmed, these QTLs may be useful for genetic improvement of allelopathy in rice using marker‐assisted selection.
Assessment of Climate Change and Agriculture in Spain Using Climate Models
Authors: Guereña Arantxa , Ruiz‐Ramos Margarita , Díaz‐Ambrona Carlos H. , Conde José R. , Mínguez M. Inés
Published: July 2010

The outputs of a general circulation model (GCM) and a regional climate model (RCM) were used as inputs for crop models to predict the impact of climate change and CO2 concentration (2×CO2 scenario) on crops and their water use in Spain. Two basins representative of irrigated agriculture were chosen to compare the phenology, aboveground biomass, yield, evapotranspiration (ET), and irrigation requirements for winter wheat (Triticum aestivum L.), winter barley (Hordeum vulgare L.), and maize (Zea mays L.) under (i) a GCM‐derived climate scenario and (ii) a RCM climate output. Spatial and temporal differences in crop performance could be enhanced by the higher resolution of the RCM. Crop phenology simulated in a 1×CO2 RCM scenario was closer to the observed phenology than the GCM‐derived one. In the 1×CO2 scenario, vegetative phenophases were shorter and reflected the higher air temperatures in the RCM. In the 2×CO2 GCM and RCM scenarios, the crop duration, ET, and irrigation requirements diminished, with no significant changes in the yield and biomass between scenarios of the same model. The higher temperatures in the RCM‐derived scenarios led to higher development rates and shorter phenophases. Nevertheless, the biomass was greater than in the GCM‐derived scenarios, especially in C3 crops. Higher temperatures in the southern areas led to a lack of vernalization in the future climate scenario, which was only detected by the RCM‐DSSAT (Decision Support System for Agrotechnology Transfer). The use of direct output of the GCM is questionable given the orography, land cover, and size of the Iberian Peninsula, and it makes the use of high‐resolution models necessary.
Growth Inhibitory Effects of Salal on Western Hemlock and Western Red Cedar
Authors: Mallik Azim U. , Prescott Cindy E.
Published: July 2010

Salal (Gaultheria shallon Pursh) regenerates vigorously after harvesting in the cedar–hemlock (CH) forests of coastal British Columbia, Canada. Eight years after harvesting, regenerating conifers on salal‐dominated sites exhibited stunted growth and chlorotic foliage. The potential inhibitory effect of salal on hemlock was tested by germinating and measuring the primary growth of seedlings in the presence of salal litter and different concentrations of the litter leachate. Effects of aboveground and belowground competition of salal and its presumed growth inhibitory effects on western hemlock [Tsuga heterophylla (Raf.) Sarg.] and western red cedar (Thuja plicata Donn ex D. Don) were tested with pot experiments under greenhouse conditions. Seed germination and primary growth of hemlock seedlings were not significantly affected by water leachates of salal leaf or litter, nor were they affected when grown directly on partially decomposed salal litter. The primary root growth of hemlock seedlings was significantly increased in CH humus. Salal litter had no significant effect on hemlock and cedar seedlings. Combined aboveground and belowground competition from salal had the strongest negative effects on both hemlock and cedar, causing significant reductions in stem height, basal diameter, and biomass. Belowground competition from salal affected the conifers more than aboveground competition. The results suggest that the growth inhibitory effect of salal on conifers is primarily due to competition for nutrients rather than allelopathic effects of litter.
Evapotranspiration in a Prairie Ecosystem
Authors: Bremer Dale J. , Auen Lisa M. , Ham Jay M. , Owensby Clenton E.
Published: July 2010

Grazing by ungulates is common in grasslands and may influence evapotranspiration (ET). The Bowen ratio energy balance method (BREB) was used to measure ET from grazed (GR) and ungrazed (UGR) tallgrass prairie sites in northeastern Kansas, USA. Yearling steers were stocked on the GR site from day of year (DOY) 128 to 202 in 1999, and ET data were collected from DOY 141 to 295. Grazing reduced ET by 28% between DOY 179 and 207; mean ET values were 3.6 (GR) and 5.0 mm d−1 (UGR). During that period, leaf area index (LAI) was an average of 78% lower on the GR site, and below‐normal precipitation kept soil dry near the surface; hence, transpiration and evaporation of water from soil decreased. Lower ET during that period, conserved soil water in the 0‐ to 0.30‐m profile on the GR site. Before that (e.g., DOY 152–179), ET was similar between treatments, despite an average 70% lower LAI on the GR site compared with the UGR site. Above‐normal precipitation during that period probably maintained high evaporation of water from soil, thereby compensating for reductions in transpiration (via LAI removal) on the GR site. Cumulative ET values during the 155‐d study were estimated at 526 and 494 mm on the UGR and GR sites, respectively. Thus, grazing reduced seasonal ET by 6.1%. Late in the study, ET was higher on the GR site, despite a lower LAI compared with the UGR site. Younger leaves in regrowth after grazing resulted in delayed senescence, causing higher ET on the GR site.
Phenological Development of Spring Barley in a Short‐Season Growing Area
Authors: Juskiw Patricia E. , Jame Yih‐Wu , Kryzanowski Len
Published: July 2010

Understanding the phenological development of barley (Hordeum vulgare L.) grown under field conditions in its major growing area in the northern Great Plains, the Canadian province of Alberta, is important for the development of a crop model in this area. Five cultivars of barley registered for production on the Canadian Prairies were grown at three locations in Alberta (Botha, Lacombe, and Olds) from 1993 to 1996. Measurements and estimates were made of 12 growth stages, the final leaf number of the main culm, phyllochrons, and leaf area indices (LAIs). The average phyllochron was 69.1 growing degree days (GDD), and the final leaf number was 9.0. While location–year differences in GDD requirements to reach successive stages could be related to environmental conditions, the genotypic effects and genotype × environment (g × e) interactions would require that specific genotypic coefficients be introduced into the model. For instance, ‘Manley’ required only 129 GDD to emerge and 493 GDD to reach Apex 1 but required 1495 GDD to reach physiological maturity while ‘Tukwa’ required 133 GDD to emerge, 514 GDD to reach Apex 1, and only 1431 GDD to reach physiological maturity. Despite genotypic differences in reaching specific growth stages, all cultivars had very synchronous growth under the wide range of environments encountered in the 12 location‐years of these tests. This should allow for the development of a crop model for barley that will accurately predict growth stages and the allocation of resources to the growth and maintenance of plant structures (leaves, stems, spikes, and kernels).
Dryland Corn in Western Kansas
Authors: Norwood Charles A.
Published: July 2010

Dryland corn (Zea mays L.) yield in western Kansas is limited by high temperatures and low rainfall. The number of hectares has increased in recent years due to improved hybrids, acceptance of reduced‐ and no‐till practices, changes in the farm program, and favorable weather conditions. Research was conducted near Garden City, KS from 1996 through 1999 to determine the effects of hybrid maturity, planting date, and plant population on the yield of dryland corn. Five hybrids with maturities of 75 (H1), 92 (H2), 98 (H3), 106 (H4), and 110 d (H5) were planted in mid‐April (D1) and early May (D2) of each year (H1 and H2 were not planted in 1996) and thinned to populations of 30000 (P1), 45000 (P2), and 60000 (P3) plants ha−1 in a wheat (Triticum aestivum L.)–corn–fallow rotation. The early May planting date (D2) produced an average of 1.51 Mg ha−1 (31.9%) more grain than did D1. In the year of the poorest rainfall distribution, D2 resulted in 2.83 Mg ha−1 (96.8%) more grain. Yield usually increased with relative maturity and plant population. The average yield increases were 13.5% from P1 to P2 and 4.3% from P2 to P3. Yield increases with higher populations were greater for earlier hybrids than for later ones. Yield of H5 was 32.6% lower at P3 than P1 in the driest year. Dryland corn should be planted in early May in western Kansas. To minimize yield reductions in dry years, relative maturities should not exceed 106 d, and populations should not exceed P2.
Population Response of Soybean Cyst Nematode to Long Term Corn–Soybean Cropping Sequences in Minnesota
Authors: Porter Paul M. , Chen Senyu Y. , Reese Curt D. , Klossner Lee D.
Published: July 2010

Soybean cyst nematode [Heterodera glycines Ichinohe] (SCN) can reduce soybean [Glycine max (L.) Merr.] yields. Rotating soybean with a nonhost crop usually reduces SCN populations. Cropping sequence experiments initiated in the early 1980s at two Minnesota locations were monitored in 1996, 1997, and 1998 for changes in SCN egg densities. Cropping sequences were: (i) 5‐yr consecutive corn (Zea mays L.) alternated with 5‐yr consecutive soybean, (ii) continuous monoculture of each crop, (iii) annual alternation of two cultivars within a continuous monoculture of each crop, and (iv) annual rotation of each crop. In 1989, SCN was detected in several of the plots at both locations. By 1996, all cropping sequences had detectable populations of SCN eggs at both locations, regardless of whether the land had been planted to continuous corn since the early 1980s. Lowest densities of SCN eggs were typically found in cropping sequences that involved continuous corn and where corn had been planted for the last three or more years, whereas highest levels of SCN eggs were found in cropping sequences that involved continuous soybean and where soybean had been planted for the last two or more years. These results suggest planting a nonhost to SCN for as long as 5 yr on infested land will not eliminate future problems with this pathogen. In addition, the results suggest that at least a portion of the crop sequence effects on yield has a soil microbiological basis involving mechanisms that are specific to a location.
Rooting Front and Water Depletion Depths in Grain Sorghum and Sunflower
Authors: Stone Loyd R. , Goodrum Dwayne E. , Jaafar Mahmad Nor , Khan Akhter H.
Published: July 2010

Rooting front advance and rooting depth are factors to consider in selecting a crop for effective use of stored soil water. Our objective was to compare rooting front development (advance rate and maximum depth) and water depletion depths of grain sorghum [Sorghum bicolor (L.) Moench] and sunflower (Helianthus annuus L.) in a field experiment. The study was near Manhattan, KS on Eudora silt loam soil (coarse‐silty, mixed, superactive, mesic Fluventic Hapludolls). Root development was quantified through multiple field samplings and the core‐break method. Water content was measured to 3.05 m by neutron attenuation. Rooting front depths of the two crops were similar from emergence to mid‐June [0 to 20 d after emergence (DAE)], but from late June, sunflower roots were deeper than sorghum roots. Maximum rooting depths were 1.85 m in sorghum and 2.49 m in sunflower (means of 2 yr). From 20 to 60 DAE, rooting front depth increased 25 and 41 mm d−1 in sorghum and sunflower, respectively. From 60 to 90 DAE, rooting front depth increased 8 and 6 mm d−1 in sorghum and sunflower, respectively. Net seasonal water depletion was greater in sunflower plots than in sorghum plots (by 103 mm in 1985 and 112 mm in 1986). Sunflower roots advanced downward from 0 to 60 DAE at a rate and depth 46 and 35% greater, respectively, than that of sorghum. The faster advance rate and deeper depth of rooting aid sunflower in drought avoidance and use of water from deeper soil depths.
Swine Lagoon Effluent as a Source of Nitrogen and Phosphorus for Summer Forage Grasses
Authors: Adeli Ardeshir , Varco Jac J.
Published: July 2010

Efficient crop utilization of N and P derived from anaerobic swine (Sus scrofa domesticus) lagoon effluent is critical to minimizing offsite nutrient movement. The objective of this study was to determine the effects of variable rates of swine lagoon effluent and fertilizer N and P on yield and nutrient utilization of forage grasses on an acid Vaiden silty clay (very fine, montmorillonitic, thermic, Vertic Hapludalf) and an alkaline Okolona silty clay (fine, montmorillonitic, thermic, Typic Chromudert). Treatments were multiple effluent irrigations resulting in four N and P rates from 0 to 665 and 0 to 94 kg ha−1 yr−1 N and P, respectively. Fertilizer treatments were also established at equivalent N and P rates. Similar growth responses were obtained for bermudagrass [Cynodon dactylon (L.) Pers.] or johnsongrass [Sorghum halepense (L.) Pers.] regardless of nutrient source. Application of either effluent or fertilizer at rates >448 kg N ha−1 did not effectively increase dry matter yield. Total N accumulation reflected both increasing dry matter yield and tissue N concentration while P accumulation depended primarily on increasing yield. Forage grass accumulation of N and P was similar between sources, but recovery efficiency for both elements declined with increasing rates. Similarity in N and P availability of effluent to fertilizer simplifies nutrient management although potential N loss by NH3 volatilization is likely greater for effluent while fertilizer may result in greater end‐of‐season soil NO−3–N levels at equivalent rates of applied N.
Comparison of Two Methods for Estimating Leaf Area Index on Common Bean
Authors: de Jesus Waldir Cintra , do Vale Francisco Xavier Ribeiro , Coelho Reginaldo Resende , Costa Luiz Claúdio
Published: July 2010

Measurement of leaf area index (LAI) is important in studies of plant growth. Based on this concept, the analysis of crop growth has moved from classical growth analysis to mechanistic models, via functional growth analysis. Leaf area index is a major variable in mechanistic crop growth models and in models that attempt to simulate loss caused by pathogens. A field experiment was carried out from May through August 1998, using common bean (Phaseolus vulgaris L. cv. Carioca), in a randomized complete block design with two methods of LAI evaluation and three replications. The objective of this study was to compare the applicability of the LAI‐2000 Plant Canopy Analyzer with the central leaflet width method used to estimate LAI in common bean. The high correlation (r2 = 0.97) observed between the two methods used to estimate LAI shows agreement between them. The results of this study indicated that the LAI‐2000 can be used to estimate the LAI of common bean.
Yield and Early Growth Responses to Starter Fertilizer in No‐Till Corn Assessed with Precision Agriculture Technologies
Authors: Bermudez Manuel , Mallarino Antonio P.
Published: July 2010

Starter fertilization often is recommended to complement broadcast fertilization. This study evaluated no‐till corn (Zea mays L.) yield and early growth responses to starter fertilization using precision agriculture tools. Strip trials, yield monitors, intensive soil sampling, global positioning systems (GPS), and geographical information systems (GIS) were used to conduct 11 trials. Liquid N–P–K starter and no‐starter treatments were applied to the seed furrow in nine fields and beside and below the seeds in two fields. Grain yield and early plant growth data were analyzed with analyses of variance (ANOVA) with or without accounting for spatial correlation with nearest‐neighbor analysis (NNA). Use of NNA reduced standard errors of treatment means. Starter fertilization increased yield in seven fields, reduced yield in one field (−231 kg ha−1), and often increased early growth. Yield increases were large (200–671 kg ha−1) in field areas with low soil‐test P (STP) (<16 mg P kg−1, Bray‐P1). Responses in areas with high STP were small (80–194 kg ha−1) when the starter was applied in the furrow and larger (165–465 kg ha−1) when it was applied beside and below the seeds at higher N rates (16.3–27.2 kg N ha−1). Across fields, early growth response (32%) was linearly but poorly correlated (r = 0.44) with yield response (2.4%). The within‐field variation in yield and growth responses was not consistently related with starter treatments, soils, or soil tests other than STP. Large yield responses of no‐till corn to starter are likely when STP is below optimum or when preplant or sidedress N rates are deficient.
Computer Use and Satisfaction by Great Plains Producers
Authors: Ascough J. C. , Hoag D. L. , McMaster G. S. , Frasier W. M.
Published: July 2010

Agronomists rely increasingly on computers, and more than half of all producers have access to computers. Increasing farm computer ownership has resulted in intensified efforts to transfer new software technologies to producers; however, little is known about how satisfied producers are with computers and the extent to which computers are actually used. We extended our 1996 survey of Great Plains producers to examine producer computer use and satisfaction and discuss potential implications for agricultural software developers. Building on our earlier computer adoption research, we developed ordered logit models for user satisfaction, frequency of computer use, and number of software applications used. Despite using more robust ordered logit models that fit the data well, surprisingly few explanatory variables were significant. Greater computer skill significantly increased user satisfaction and number of software applications used. Greater education also increased user satisfaction and number of software applications used but reduced frequency of computer use. Farming experience showed similar conflicting results as education, i.e., greater number of years farming resulted in significantly increased computer satisfaction but lower frequency of use and number of software applications used. A few other explanatory variables (e.g., farm owner or operator as the primary computer user had a significant positive influence on frequency of use) were important in one of the three ordered logit models, but no consistent relationship between models was found. Generally, greater frequency of use and computer skill increased perceived usefulness of computers by producers. Implications of these results for agricultural software developers are discussed in the paper.
Optimum Nitrogen Fertilization of Cool‐Season Grasses in the Northeast USA
Authors: Hall M. H. , Beegle D. B. , Bowersox R. S. , Stout R. C.
Published: July 2010

Many studies have looked at the economically optimum N application rate (cost of N vs. increased yield) for cool‐season forage grasses, but few of these studies have also addressed the effect of N fertilization on livestock or environmental health. The objective of this study was to determine the N application rate to cool‐season grass species that optimizes economic return without elevating herbage or soil NO3–N levels. Four N rates were applied in split applications to established stands of orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromus inermis Leyss.), tall fescue (Festuca arundinacea Schreb.), and timothy (Phleum pratense L.) near State College, PA, on a Murrill silt loam (fine‐loamy, mixed, mesic Typic Hapludults) soil. Harvest treatments of three and four times per year were imposed on each Grass × N treatment. Economically optimum N rates (EONR) were 284, 368, and 299 kg N ha−1 or 26, 32, and 29 kg N Mg−1 of forage harvested for orchardgrass, tall fescue, and timothy, respectively. Smooth bromegrass did not reach an economic plateau at the highest (402 kg ha−1) N rate. At EONR, NO3–N concentration exceeded 1000 mg kg−1 in forage from early season harvests when four harvests per year were taken but not when three harvests per year were taken. Soil NO3–N concentration generally was not elevated above background levels when EONR was applied to orchardgrass or tall fescue. Our results, in conjunction with results from New York, indicate that the EONR for the cool‐season grasses and harvest systems evaluated is 5 to 10 kg N Mg−1 of dry forage greater than current recommendations in New York and Pennsylvania. However, continued research is needed in a wider range of climates and soil types using various N sources.
Combined Effects of Legumes with Rock Phosphorus on Rice in West Africa
Authors: Somado Eklou A. , Becker Mathias , Kuehne Ronald F. , Sahrawat Kanwar L. , Vlek Paul L. G.
Published: July 2010

Rice (Oryza sativa L.) demand in West Africa is unmet because of insufficient production. Legume fixed N [biological N fixation (BNF)] may sustainably increase rice productivity in low‐input systems. However, P deficiency limits BNF on the acid soils encountered in the region, despite the prevalence of phosphate rock (PR). Pot and field experiments were conducted in Côte d'Ivoire in 1996–1998 to study the impact of combined legume and PR on rice performance. Triple superphosphate and PR were applied at rates of 60 (pot) and at 90 (field) kg P ha−1 to rice and the legume Aeschynomene afraspera grown for 8 wk and then incorporated before rice transplanting. Legume fixed N was determined by 15N isotope dilution. Under field conditions, addition of PR doubled the biomass of A. afraspera. Irrespective of P source, P application increased the amount of BNF‐N (three‐ to eightfold) to 36 mg N plant−l in pots and to 84 kg N ha−1 in the field. Nitrogen derived from the air was correlated with legume P uptake (r = 0.97∗∗∗, where ∗∗∗ = significant at the 0.001 level) and nodulation (r = 0.91∗∗, where ∗∗ = significant at the 0.01 level). The synergy of PR and BNF on N and P cycling improved P nutrition and total biomass of subsequent lowland rice under pot conditions. Combining legume green manure (GM) with PR enhanced soil extractable Bray‐1 P and may thus play an important role in improving the availability of PR. Under field conditions, due to asynchrony in GM nutrient release and demand, the impact of the combined GM–PR treatment on rice yield was minimal.
Barley, Oat, and Cereal–Pea Mixtures as Dryland Forages in the Northern Great Plains
Authors: Carr Patrick M. , Horsley Richard D. , Poland Woodrow W.
Published: July 2010

Oat (Avena spp.) is a popular cereal forage in cool semiarid regions. Barley (Hordeum vulgare L.) has produced equal or greater amounts of superior quality forage in subhumid regions. The importance of cereal crop, cultivar, and plant part on forage production was determined in low‐soil‐N environments in southwestern North Dakota. Barley and oat cultivars, along with intercrops of pea (Pisum sativum L. subsp. sativum) with barley and oat, were compared for forage yield and quality over 2 yr. Forage dry matter (DM) yield averaged 3.84 Mg ha−1 for oat compared with 2.91 Mg ha−1 for barley while crude protein (CP) concentration of oat forage averaged 61 g kg−1 compared with 90 g kg−1 for barley (P < 0.05). No difference in forage N yield occurred between barley and oat. Acid detergent fiber and neutral detergent fiber concentrations averaged 39 and 41 g kg−1 lower, respectively, for barley compared with oat forage while Ca and P concentrations were higher for barley forage. Cultivar selection within each crop species generally did not affect forage yield or quality. The relative contributions of stem, inflorescence, leaf blade, and leaf sheath to forage yield were similar between cereal species and averaged 20, 44, 14, and 22%, respectively. Intercropping with pea increased forage and N yield. These results suggest that forage yield is reduced but quality is enhanced when oat is replaced with barley in low‐soil‐N, unfertilized environments. Furthermore, the results indicate that forage yield and quality can be enhanced by intercropping barley or oat with pea.
Effect of Seeding Rate on Alfalfa Stand Longevity
Authors: Hall M. H. , Nelson C. J. , Coutts J. H. , Stout R. C.
Published: July 2010

Alfalfa (Medicago sativa L.) seeding rates greatly affect the number of surviving plants after 1 yr. The objective of this research was to determine what effect seeding rate has on alfalfa stand density two or more years after seeding. Different alfalfa cultivars were spring‐seeded at rates ranging from 3 to 27 kg ha−1 pure live seed into tilled seedbeds in Missouri and Pennsylvania to provide eight location‐years of data. After the seeding year, herbage was removed four or five times each year. Stand densities were determined one to three and five to eight months after planting (MAP) and annually in the spring thereafter for up to 7 yr after planting. Increasing seeding rates resulted in near linear increases in plant densities from 100 to 800 plants m−2 within 3 MAP. Higher plant densities experienced eight times higher plant deaths the first year after planting compared with lower plant densities. At all eight location‐years of this research, the period 24 to 36 MAP had the least amount of plant deaths regardless of seeding rate. Higher plant densities associated with seeding rates greater than 17 kg ha−1 did not persist beyond 6 MAP. Seeding rates of 10 and 17 kg ha−1 had similar plant densities by 24 MAP in 75% of the location‐years although further reductions in seeding rate reduced plant density for up to 4 yr after planting. Seeding rates greater or slightly less than those recommended have little to no effect on the life expectancy of an alfalfa stand.
Periodic Response of Soybean Yields and Economic Returns to Long‐Term No‐Tillage
Authors: Yin Xinhua , Al‐Kaisi Mahdi M.
Published: July 2010

Farmers have been encouraged to adopt no‐tillage (NT) because of its positive environmental effects compared with other conservation tillage systems. Nevertheless, poor crop performance under NT management has been reported in both short‐ and long‐term experiments. This study was conducted on six different soils (a poorly drained Taintor soil near Burlington, a moderately well‐drained Kenyon soil near Nashua, a well‐drained Clarion soil near Newell, a well‐drained Galva soil near Sutherland, and a well‐drained Nira soil and a poorly drained Kalona soil near Crawfordsville) in Iowa during 1978 to 2001. Soybean [Glycine max (L.) Merr.] response to long‐term NT management was evaluated by 5‐yr periods and on the average over the entire study in terms of grain yields and economic returns. The design of the field experiments was a randomized complete block or split plot. Eight tillage systems, including NT, moldboard plow, chisel plow, ridge tillage, alternative tillage, reduced tillage, field cultivation, and tillage‐plant were investigated in a corn (Zea mays L.)–soybean rotation. Differences between NT and other tillage systems in both soybean grain yields and economic returns remained the same over the entire period of each study, ranging from 8 to 15 yr. No‐tillage generally had less than 5% yield decrease and equal or greater economic returns compared with other tillage systems on well‐drained soils during each 5‐yr period and when averaged over the entire study. Therefore, economic returns favor the adoption of NT for soybean production from both short‐ and long‐term perspectives for well‐drained soils in Iowa.
Forage Potential of Intercropping Berseem Clover with Barley, Oat, or Triticale
Authors: Ross Shirley M. , King Jane R. , O’Donovan John T. , Spaner Dean
Published: July 2010

Intercropping berseem clover (Trifolium alexandrinum L.) with silage cereals may increase forage yield and quality. Berseem clover was intercropped with barley (Hordeum vulgare L.), oat (Avena sativa L.), or triticale (×Triticosecale rimpaui Wittm.) at 30, 60, 90, 120, and 240 cereal plants m−2 at Edmonton, Alberta, from 1998 to 2001. Cereals dominated Cut 1 (silage‐stage) yield, and berseem clover dominated regrowth yield. As cereal density decreased from 240 to 60 plants m−2, Cut 1 yield decreased from 10.5 to 9.3 Mg ha−1 dry matter (DM), berseem clover percentage of Cut 1 increased from 5 to 14%, and berseem clover regrowth yield (Cut 2) increased from 1.8 to 3.0 Mg ha−1 DM. Total season intercrop yields with barley or oat at 60 plants m−2 were ≥yields with 240 plants m−2. Total season intercrop DM yields did not differ among the three cereal species in 3 of 4 yr. Triticale intercrops had advantages of greater Cut 1 yield and greater berseem clover percentage in Cut 1. Barley intercrops had advantages of greater Cut 2 yield and greater total season protein yield. Greater Cut 2 yield with barley intercrops was related to earlier silage‐stage (Cut 1) harvest date. Intercropping berseem clover with reduced seeding rates of cereals improved Cut 1 forage quality. When berseem clover was 20% of Cut 1 yield, neutral detergent fiber was 25 to 45 g kg−1 less than with cereals alone. The crude protein of berseem clover regrowth averaged 210 g kg−1, providing high quality late‐season forage.
Scaling Properties of Topographic Indices and Crop Yield: Multifractal and Joint Multifractal Approaches
Authors: Zeleke Takele B. , Si Bing Cheng
Published: July 2010

Topography controls soil water distribution in semiarid environments where water is the major growth‐limiting factor. Identification of the topographic index that best represents the spatial variability and scaling properties of crop yield is important for precision farming. Our objective was to characterize the scaling properties of four topographic indices [relative elevation (RE), wetness index (WI), upslope length (USL), and curvature (CR)] and their relationships to wheat (Triticum aestivum L.) grain yield and biomass using multifractal and joint multifractal approaches. Wheat grain yield and terrain data were collected at 6‐m intervals along a 576‐m‐long transect on a nonlevel landscape with dominant soil type of Aridic Ustoll, under the semiarid environment of Saskatchewan, Canada. Results indicated that CR and RE had a fractal type of scaling only for a narrow range of moment orders. Wetness index showed a monofractal scaling with fractal dimension of 0.98; whereas yield, biomass, and USL showed a multifractal scaling. Joint multifractal analyses showed a high correlation coefficient between the scaling indices of grain yield and USL (r = 0.93). Wetness index appeared to be effective as a yield covariate only at low slope areas and depressions where it has similar scaling to that of USL. Results from this study suggested that USL was the best indicator of grain yield and biomass at any scale. The implication for precision farming is that USL can be used as a guideline for varying production inputs such as fertilizer as well as for yield prediction.
Seedbed Surface Geometry Effects on Soil Crusting and Seedling Emergence
Authors: Baumhardt R.L. , Unger P.W. , Dao T.H.
Published: July 2010

Seedling emergence is the crucial first step in crop establishment; however, crops frequently must penetrate or lift a thin, dense, soil layer called a crust, which is formed by drop impact or aggregate slaking during rainstorms and sprinkler irrigation. Shaping the soil surface into a small ridge or cap above the seed row may decrease crust strength and improve seedling emergence. Our objectives were to quantify the effects of surface soil geometry (25 mm high by 50 mm wide soil cap without removal) on (i) crust formation and strength, (ii) seedling emergence of selected crops, and (iii) seed zone soil temperature. Sieved (<12 mm) Pullman clay loam soil (Torrertic Paleustoll) was packed into columns (0.30 m wide by 0.45 m long by 0.15 m deep) and planted with grain sorghum [Sorghum bicolor (L.) Moench], corn (Zea mays L.), sunflower (Helianthus annuus L.), and wheat (Triticum aestivum L.) in rows with a flat or capped surface. Columns were mounted at a 5% slope on a turntable beneath a rotating disk‐type rain simulator that applied reverse osmosis water for 1 h at a 48 mm h−1 intensity with intercepted or normal drop impact energy. Compared with intercepted (INT) drop impact conditions, normal drop impact (DI) reduced infiltration 22% and formed 4.9 mm thicker crusts that prevented seedling emergence. Thickness, penetration resistance, and seedling emergence of DI soil crusts were unaffected by surface caps. Mean seed zone soil temperatures increased with INT drop impact, but was unaffected by capping. Our test shows that unremoved soil caps did not improve seedling emergence; however, intercepting raindrop impact increases seedling emergence.