bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Water Use and Growth of Russian Thistle after Wheat Harvest
Authors: Schillinger William F. , Young Frank L.
Published: July 2010

Russian thistle (Salsola iberica Sennen and Pau) is a major broadleaf weed in dryland crops (<300 mm annual precipitation) in the Pacific Northwest of the USA. Russian thistle frequently infests wheat (Triticum aestivum L.) and other spring‐sown crops, especially during drought. Quantitative information on water use, biomass accumulation, and seed production of Russian thistle after wheat harvest is lacking. In a 2‐yr field study at Lind, Washington, Russian thistle plants were allowed to grow yearly in spring wheat in a grid pattern without competition from other weeds. Individual Russian thistle plants used 70 L of soil water while growing with the crop. From wheat harvest in early August until killing frost in late October, each Russian thistle used an additional 100 L of soil water. Water use occurred within a 1.5‐m radius of the Russian thistle. Spring wheat competed with Russian thistle for water at shallow soil depths; most water use by Russian thistle was from deeper than 1.0 m. Russian thistle dry weight increased from 170 to 1280 g per plant between grain harvest and killing frost. Russian thistle seeds were either not produced or germinable until mid‐September. By late October, individual plants had produced 67000 and 25000 seeds in 1996 and 1997, respectively. In low crop residue situations, rapid post‐harvest growth by Russian thistle (before seed production) provides valuable surface cover for erosion control, but with the prospect that soil water may be reduced for the subsequent crop.
Correlation of Corn and Soybean Grain Yield with Topography and Soil Properties
Authors: Kravchenko Alexandra N. , Bullock Donald G.
Published: July 2010

Analysis of yield variability is an important issue in agricultural research, and topographical land features are among the most important yield‐affecting factors. The objective of this study was to determine how useful topographical information can be, alone or together with selected soil properties, for explaining yield variability on a field scale. Yield–topography–soil relationships were analyzed using dense corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yield data collected from 1994 to 1997, a detailed terrain map, and relatively densely sampled soil organic matter (OM) content, cation exchange capacity (CEC), and P and K soil test concentrations from eight fields in central Illinois and eastern Indiana. Soils of the Illinois fields were classified as Haplaquolls and Argiudolls; soils of the Indiana fields were classified as Hapludalfs. Topographical land features used in the study included elevation, measured with survey grid global positioning system (GPS) and land‐based laser, and slope, curvature, and flow accumulation, derived from elevation data. Soil properties explained about 30% of yield variability (from 5 to 71% for different fields), with OM content influencing yield the most. The cumulative effect of the topographical features explained about 20% of the yield variability (6–54%). Elevation had the most influence on yield, with higher yields consistently observed at lower landscape positions. Curvature, slope, and flow accumulation significantly affected yield only in certain conditions, such as extreme topographical locations (undrained depressions or eroded hilltops) combined with very high or low precipitation. Soil properties and topography explained about 40% of yield variability (10–78%).
Intercepted Radiation at Flowering and Kernel Number in Maize
Authors: Andrade Fernando H. , Otegui María E. , Vega Claudia
Published: July 2010

When water and nutrients are not limiting growth, kernel number per plant (KNP) can be calculated for maize (Zea mays L.) using linear models based on intercepted photosynthetically active radiation per plant (IPARP). These models do not include the concept of a threshold IPARP for KNP. Our objective was to study the response of KNP to IPARP in order to improve current models. Published information from several field experiments, performed with two maize hybrids in the temperate region of Argentina, was used for the analysis. Both linear and curvilinear (inverse linear and exponential) models based on IPARP explained more than 75% of the variability in KNP and kernel number per apical ear (KNA). Curvilinear models gave a better fit at low (<0.5 MJ plant−1 d−1) and intermediate (1.3‐2 MJ plant−1 d−1) values of IPARP than a simple two‐line linear model. Models allowed the estimation of maximum KNA and maximum KNP, and the minimum IPARP to reach them, but only curvilinear models allowed the estimation of a threshold IPARP (0.31‐0.37 MJ plant−1 d−1) to avoid plant barrenness. The inverse linear model gave a better prediction of maximum kernel number than the other two models. The exponential model allowed a better estimation of the initial value (2.16 MJ plant−1 d−1) for expressing prolificacy (ears plant−1) > 1. The relationship between KNP and IPARP did not improve when IPARP was expressed on a thermal time basis (photothermal quotient), probably because air temperature did not vary much among the situations explored in this work.
Early Impact of Topsoil Removal and Soil Amendments on Crop Productivity
Authors: Larney Francis J. , Olson Barry M. , Janzen H.Henry , Lindwall C.Wayne
Published: July 2010

Wind erosion remains a common form of soil degradation on the semiarid northern Great Plains. This study was conducted to ascertain the effects of erosion on soil productivity and methods for its amelioration. Incremental depths (0, 5, 10, 15, and 20 cm) of surface soil or cuts were mechanically removed to simulate erosion at four sites (three dryland, one irrigated) in southern Alberta in 1990–1991. Three amendment treatments (N + P fertilizer, 5 cm of topsoil, or 75 Mg ha−1 of feedlot manure) and a check were superimposed on each of the cuts. In the first three years (1990–1992), there were highly significant relationships between cut and spring wheat (Triticum aestivum L.) yield parameters (midseason biomass, grain and straw yield, head density, tillering capacity, and grain elemental concentrations). Removal of 20 cm of topsoil reduced grain yield by 53% (an average of 11 site‐years). Manure proved the best amendment for restoring productivity (e.g., an 11‐site‐year average increase of 158% in grain yield on the 20‐cm cut), with N + P fertilizer being the least effective (40% grain yield increase on the 20‐cm cut). Manure's ability to supply crop P, Mg, Mn, and Zn may partially explain its positive effect. Topsoil addition was intermediate in its restorative powers (89% yield increase after 20 cm topsoil removal). The study reinforces the need to prevent erosion and indicates that application of livestock manure is an option for restoring soil productivity in the short term.
Physiological and Biochemical Mechanism of Allelopathy of Secalonic Acid F on Higher Plants
Authors: Zeng Ren Sen , Luo Shi Ming , Shi Yue Hong , Shi Mu Biao , Tu Cong Yong
Published: July 2010

Our previous work indicated that secalonic acid F (SAF) was the major allelochemical produced by Aspergillus japonicus Studies showed that SAF markedly inhibited the seedling growth of sorghum (Sorghum vulgare Pers.), hairy beggarticks (Bidens pilosa L.), and barnyardgrass (Echinochloa crus‐galli (L.) Beauv.). It significantly reduced the activities of superoxide dismutase (SOD) and peroxidase (POD) at a concentration of 0.3 mM Secalonic acid F enhanced malondialdehyde (MDA) contents, but it lowered the content of chlorophyll (CHL) a and b as well as the photosynthetic rates of tested plants. Respiration, membrane permeability, and abscisic acid (ABA) content increased after treatment with SAF, but the reduction activity of the root system was lowered. There is no remarkable change in the soluble proteins of plants that are treated with SAF. Transmission electron microscope (TEM) observations showed that treated plants exhibited amorphous mitochondria without integral membranes and swelling chloroplasts without membranes in a disorderly arrangement. The SAF treatment also damaged the stratiform structure of the chloroplasts and the membranes and structure of the nuclei. These results suggest that SAF may weaken the protective ability of plant tissues against membrane lipid peroxidation and damage the whole membrane system of plants, resulting in the ultrastructure destruction of chloroplasts, mitochondria, and nuclei. Cell ultrastructure destruction causes a reduction of photosynthesis and root activities and an increase in respiration. These abnormal physiological processes contribute to the inhibition of plant growth.
Nitrogen Replacement Values of Kura Clover and Birdsfoot Trefoil in Mixtures with Cool‐Season Grasses
Authors: Zemenchik Robert A. , Albrecht Kenneth A. , Schultz Melissa K.
Published: July 2010

Kura clover (Trifolium ambiguum M. Bieb.) is a perennial legume that, when grown in mixture with grass, may improve forage yield while providing biologically fixed N. Kura clover's value as an alternative to N fertilization of cool‐season grasses for improved yield is unknown. Fertilizer N replacement values (FNRVs) of kura clover and birdsfoot trefoil (Lotus corniculatus L.), in terms of total season forage yield, were compared when grown in binary mixtures with Kentucky bluegrass (Poa pratensis L.), smooth bromegrass (Bromus inermis Leyss.), or orchardgrass (Dactylis glomerata L.). Separate experiments for each grass were conducted from 1994 through 1996 near Arlington and Lancaster, WI. Treatments in each experiment included six levels of N fertilizer on grass monocultures and two non‐N‐fertilized binary mixtures of grass with either legume. The FNRV for either kura clover or birdsfoot trefoil correlated positively with total season legume yield. When averaged across locations, kura clover–smooth bromegrass mixtures had annual FNRVs that ranged from 74 to 325 kg N ha−1 while those of birdsfoot trefoil–smooth bromegrass mixtures ranged from 147 to 295 kg N ha−1. When averaged across years and locations, FNRVs for kura clover and birdsfoot trefoil were 251 and 269 kg N ha−1 in orchardgrass, respectively. Grass yields in mixtures were similar to grass monocultures receiving no fertilizer N. Because kura clover outyielded birdsfoot trefoil in all 1996 mixtures, we expect the FNRV of kura clover to exceed that of birdsfoot trefoil in the long term.
Growth, Development, and Yield of Soybean Lines Developed for Forage
Authors: Darmosarkoro Witjaksana , Harbur Matthew M. , Buxton Dwayne R. , Moore Kenneth J. , Devine Thomas E. , Anderson Irvin C.
Published: July 2010

Recently, soybean [Glycine max (L.) Merr.] cultivars have been developed specifically for use as a forage crop. The objective of this study was to determine the effect of maturity group on and compare the agronomic performance of forage and grain soybean cultivars in Iowa. In 1994, 13 forage‐ and five grain‐type cultivars were studied. In 1995, one additional forage cultivar and grain cultivar were each evaluated. Node number, plant height, lodging, and dry matter accumulation were measured biweekly during the growing season. By 135 days after planting (DAP), forage cultivars yielded 5 to 19% more dry matter than ‘Sherman’, which had the greatest yield among grain cultivars. Forage cultivars were 37 to 69% taller than ‘Biloxi’, the tallest grain cultivar, which may partially explain the greater lodging of the forage cultivars compared with the grain cultivars. Forage cultivars initiated reproductive growth 60 to 88 DAP, whereas the locally adapted Sherman cultivar initiated reproductive growth 55 DAP. Forage cultivars produced more dry matter than grain cultivars, but had a lower leaf/stem ratio and leaf + pod/stem ratio in August and September, respectively, which may reduce forage quality. Forage cultivars developed in Pennsylvania generally accumulated more dry matter than forage cultivars developed in Virginia by late August, but initiated reproductive growth sooner and produced less dry matter by late September. The significant productivity differences observed between forage and grain cultivars suggest the potential of breeding to improve the forage potential of soybean.
Simulating Soybean Water Stress Effects with RZWQM and CROPGRO Models
Authors: Nielsen David C. , Ma Liwang , Ahuja Lajpat R. , Hoogenboom Gerrit
Published: July 2010

The Root Zone Water Quality Model (RZWQM) and CROPGRO‐Soybean simulate soybean [Glycine max (L.) Merr.] growth, development, and yield. The models require calibration for soybean grown in the specific environmental conditions of the central Great Plains before any long‐term assessments can be made of dryland soybean yield potential under the highly variable precipitation patterns of this area. The objective of this study was to calibrate and test RZWQM and CROPGRO‐Soybean for soybean growth, yield, and water use under a range of water stress conditions normally encountered by dryland production systems in the central Great Plains. Data from five experiments, each with four levels of water availability (20 data sets), were used to evaluate leaf area, plant height, aboveground biomass, evapotranspiration (ET), soil water extraction, and yield of soybean. Data from one water level of one experiment was used to calibrate the models, and the other 19 data sets were used as evaluation data sets. Both models correctly predicted the time course of volumetric water content, leaf area development, and plant and height biomass increase although RZWQM more accurately simulated water extraction in the lower soil profile. The decline in ET that is a result of decreased water availability was generally predicted well by both models. The models generally estimated the yield to within 10 to 15% of measured values. The models should be useful tools in evaluating the potential for soybean as an alternative crop in dryland rotations in the central Great Plains.
Tillage System and Crop Rotation Effects on Dryland Crop Yields and Soil Carbon in the Central Great Plains
Authors: Halvorson Ardell D. , Peterson Gary A. , Reule Curtis A.
Published: July 2010

Winter wheat (Triticum aestivum L.)–fallow (WF) using conventional stubble mulch tillage (CT) is the predominant production practice in the central Great Plains and has resulted in high erosion potential and decreased soil organic C (SOC) contents. This study, conducted from 1990 through 1994 on a Weld silt loam (Aridic Argiustoll) near Akron, CO, evaluated the effect of WF tillage system with varying degrees of soil disturbance [no‐till (NT), reduced till (RT), CT, and bare fallow (BF)] and crop rotation [WF, NT wheat–corn (Zea mays L.)–fallow (WCF), and NT continuous corn (CC)] on winter wheat and corn yields, aboveground residue additions to the soil at harvest, surface residue amounts at planting, and SOC. Neither tillage nor crop rotation affected winter wheat yields, which averaged 2930 kg ha−1. Corn grain yields for the CC (NT) and WCF (NT) rotations averaged 1980 and 3520 kg ha−1, respectively. The WCF (NT) rotation returned 8870 kg ha−1 residue to the soil in each 3‐yr cycle, which is 2960 kg ha−1 on an annualized basis. Annualized residue return in WF averaged 2520 kg ha−1, which was 15% less than WCF (NT). Annualized corn residue returned to the soil was 3190 kg ha−1 for the CC (NT) rotation. At wheat planting, surface crop residues varied with year, tillage, and rotation, averaging WCF (NT) (5120 kg ha−1) > WF (NT) (3380 kg ha−1) > WF (RT) (2140 kg ha−1) > WF (CT) (1420 kg ha−1) > WF (BF) (50 kg ha−1). Soil erosion potential was lessened with WCF (NT), CC (NT), and WF (NT) systems because of the large amounts of residue cover. Levels of SOC in descending order in 1994 were CC (NT) ≥ WCF (NT) ≥ WF (NT) = WF (RT) = WF (CT) > WF (BF). Although not statistically significant, the CC (NT) treatment appeared to be accumulating more SOC than any of the rotations that included a fallow period, even more rapidly than WCF (NT), which had a similar amount of annualized C addition. Reduced tillage and intensified cropping increased SOC and reduced soil erosion potential.
Carbon Dioxide and Temperature Effects on Evapotranspiration and Water Use Efficiency of Soybean
Authors: Allen L. H. , Pan Deyun , Boote K. J. , Pickering N. B. , Jones J. W.
Published: July 2010

Rising CO2 and potential global warming will cause changes in evapotranspiration (ET). Our research objective was to determine the impact of CO2 and air temperature on canopy ET, water use efficiency (WUE), foliage temperature, and canopy resistance (Rc) of soybean [Glycine max (L.) Merr.]. Plants were grown in sunlit, controlled‐environment chambers at cyclic maximum/minimum air temperatures from 28/18°C to 44/34°C and CO2 of 350 or 700 μmol mol−1 Maximum ET rate in the early afternoon at 35 d after planting ranged from 7.5 mol m−2 s−1 at 28/18°C to 19.0 mol m−2 s−1 at 44/34°C. Daily ET during the middle of the season ranged from 260 mol H2O m−2 d−1 (4.7 mm d−1) at 28/18°C to 660 mol H2O m−2 d−1 (11.9 mm d−1) at 44/34°C. Mean daily ET was linearly related to mean air temperature (Tair) as: [Mean daily ET = 21.4 × Tair − 306, r2 = 0.99 (mol H2O m−2 d−1), or mean daily ET = 0.385 × Tair − 5.5 (mm d−1)]. Doubled CO2 caused a 9% decrease in ET at 28/18°C, but CO2 had little effect at 40/30°C or 44/34°C. Whole‐day WUE declined linearly with air temperature, with a slope of −0.150 [(μmol CO2 mmol−1 H2O) °C−1]. Changes in ET and WUE were governed by changes in foliage temperature and Rc. In conclusion, increases in temperature anticipated by climate change could more than offset decreases of ET that would be caused by increases in CO2
Pesticide Free Production of Field Crops
Authors: Nazarko Orla M. , Van Acker Rene C. , Entz Martin H. , Schoofs Allison , Martens Gary
Published: July 2010

Existing strategies for pesticide use reduction in the northern Great Plains have suffered from limited adoption. A novel approach, Pesticide Free Production (PFP), was recently developed in Manitoba, Canada. A participatory, on‐farm study was conducted to assess the potential of PFP to be implemented on typical farms and the level of success farmers experienced with PFP. Pesticide Free Production prohibits the use of in‐crop pesticide and seed treatments during one crop year as well as prior use of residual pesticides. Synthetic fertilizer use is permitted, as are pre‐emergent applications of nonresidual pesticides. A total of 71 farmers, representing 120 fields and 11 crops, participated in the study. Fields and farmers were grouped based on whether or not fields (i) achieved PFP certification and (ii) were in transition to organic production. Certification was achieved for 83% of the participating area. Spring cereals were the most likely crops to achieve PFP certification. Yields in all groups were slightly lower than conventional averages in Manitoba but were not significantly different among groups. Weed densities were higher (P = 0.065) in noncertifiable fields than in certifiable fields. Most farmers reported manageable weed densities in the year following PFP. Soil conservation practices were used on a high proportion of PFP fields. Management practices associated with PFP included the use of delayed seeding, forages in rotation, and increased seeding rates. Agronomic and demographic characteristics of participating fields and farmers were typical for Manitoba. Pesticide Free Production demonstrates considerable potential to be successfully adopted by mainstream farmers.
Dynamics of Competition between Wheat and Oat
Authors: Cousens Roger D. , Barnett Allan G. , Barry Geoffrey C.
Published: July 2010

Supply and demand for resources change dynamically throughout the growing season. If we are to understand the differences in competitiveness among crop cultivars, we need to study the dynamics of species interactions, not just their outcomes. We examined the temporal patterns in competition between wheat (Triticum aestivum L.) and oat (Avena sativa L.) in a series of field experiments. The combined effects of shifts in height growth and phenological development were described for monocultures and mixtures by varying the sowing dates of the species. Similar observations were made for oat competing with wheat lines differing in flowering time and for wheat competing with a range of Avena taxa. In contrast to earlier work, no reversals of competitive hierarchy were seen during the season. The species that achieved the greater biomass early on remained the better competitor throughout growth. The hypothesis that a delay in emergence will move the timing of such reversals was thus not supported. There were few differences in patterns of the dynamics of competition among Avena taxa and no observable differences in competitiveness among wheat lines differing by up to 6 d in flowering date. Overall, the results support the idea that reversals in competitive hierarchy during the season are caused by relative patterns in plant height growth of competitors and may occur only in systems in which competition for light is dominant. Otherwise, an early competitive hierarchy will be maintained throughout the growing season.
Effects of Nitrogen Rate, Irrigation Rate, and Plant Population on Corn Yield and Water Use Efficiency
Authors: Al‐Kaisi Mahdi M. , Yin Xinhua
Published: July 2010

Improper N and irrigation management are major factors contributing to water quality and shortage problems in the Great Plains. This study was conducted on the Irrigation Research Farm in Yuma, CO, from 1998 through 2000 to establish an accurate irrigation and N management system for corn (Zea mays L.) production in the Great Plains aimed at high yield and water use efficiency (WUE) simultaneously. A field experiment was conducted on a center‐pivot–irrigated, well‐drained Haxtun sandy loam soil (fine‐loamy, mixed, superactive, mesic Pachic Argiustolls) by using a randomized complete block split‐split plot design, with irrigation rates [0.60, 0.80, and 1.00 of the estimated evapotranspiration (ET)], N fertility rates (30, 140, 250, and 360 kg ha−1, including N from soil, fertilizer, and irrigation water), and plant populations (57000, 69000, and 81000 plants ha−1) as the main‐plot, split‐plot, and split‐split plot treatments, respectively. A combination of 0.80ET to 1.00ET, 140 to 250 kg N ha−1, and 57000 to 69000 plants ha−1 population provided optimum corn yield. Irrigation treatment 0.80ET, accompanied by 140 to 250 kg N ha−1, and 57000 to 69000 plants ha−1 population was the best management system for optimum WUE. No significant differences in water extraction from the soil profile for the entire season and soil moisture content at harvest between the 0.80ET and 1.00ET irrigation treatments were additional indications that 0.80ET is superior to 1.00ET. To preserve the Ogallala Aquifer, the best management system aimed at optimum WUE should be used for corn production in the Great Plains region.
Monitoring Maize (Zea mays L.) Phenology with Remote Sensing
Authors: Viña Andrés , Gitelson Anatoly A. , Rundquist Donald C. , Keydan Galina , Leavitt Bryan , Schepers James
Published: July 2010

Monitoring crop phenology is required for understanding intra‐ and interannual variations of agroecosystems, as well as for improving yield prediction models. The objective of this paper is to remotely evaluate the phenological development of maize (Zea mays L.) in terms of both biomass accumulation and reproductive organ appearance. Maize phenology was monitored by means of the recently developed visible atmospherically resistant indices, derived from spectral reflectance data. Visible atmospherically resistant indices provided significant information for crop phenology monitoring as they allowed us to detect: (i) changes due to biomass accumulation, (ii) changes induced by the appearance and development of reproductive organs, and (iii) the onset of senescence, earlier than widely used vegetation indices. Visible atmospherically resistant indices allowed the identification of the timing of phenological transitions that are related to the maize physiological development. They also allowed identification of the onset of the grain‐fill period, which is important since maximum yield potential of maize plants depends on optimal environmental conditions during this period.
Stockpiling Potential of Perennial Forage Species Adapted to the Canadian Western Prairie Parkland
Authors: Baron Vern S. , Dick A. Campbell , Bjorge Myron , Lastiwka Grant
Published: July 2010

Stockpiling perennial forages for fall and winter grazing is not generally practiced on the Prairie Parkland of Canada. The objective was to determine forage species with most potential for stockpiling in this short‐season region. The research was conducted for 3 yr at Lacombe, AB. Plots of adapted forage grasses and alfalfa (Medicago sativa L.) were clipped in early July. Regrowth forage mass was determined in mid‐September, mid‐October, and the following April. Forage quality measurements included in vitro digestible organic matter (IVDOM), crude protein, water‐soluble carbohydrates (WSC), and acid (ADF) and neutral (NDF) detergent fiber. Overwinter yield losses were lower with grasses (3–35%) than alfalfa (43%). Meadow bromegrass (Bromus riparius Rhem.) had stable stockpiled yields over both dry (5130 kg ha−1) and wet (5450 kg ha−1) years and retained nutritive value well into winter and spring. Timothy (Phleum pratense L.) provided greatest stockpiled yields in years of above‐average rainfall (9700 kg ha−1), but protein levels (<70 g kg−1) may be lower than desired in some years. Kentucky bluegrass (Poa pratensis L.) and creeping red fescue (Festuca rubra L.) had relatively low stockpiled yields (3160–5020 kg ha−1). However, quackgrass [Elytrigia repens (L.) Nevski] yielded well under good rainfall conditions (6180 kg ha−1), and dry matter loss (16%) was below average. Spring NDF (644 g kg−1) and IVDOM (495 g kg−1) concentrations of creeping red fescue were lowest and highest among species, respectively. Creeping red fescue and meadow bromegrass have the best chance of meeting cow nutritive requirements during winter and spring.
Nitrogen Balance as Affected by Application Time and Nitrogen Fertilizer Rate in Irrigated No‐Tillage Maize
Authors: Rozas Hernán R. Sainz , Echeverría Hernán E. , Barbieri Pablo A.
Published: July 2010

High N requirements of no‐tillage maize (Zea mays L.) make it imperative to develop management strategies that optimize crop production and N use efficiency (NUE). A 4‐yr field experiment was conducted at Balcarce (37°45′S, 58°18′W), Argentina, on a Typic Argiudoll and a Petrocalcic Paleudoll. The objective was to evaluate the effect of urea rate (0, 70, 140, and 210 kg N ha−1) at planting (FPL) or six‐leaf stage (FV6) on NH3 volatilization, denitrification, soil residual nitrate, soil microbial biomass N (MBN), N uptake, grain yield, and unaccounted N (UN). Grain yield was 10.5 and 11.2 Mg ha−1, and N uptake at physiological maturity was 168 and 192 kg N ha−1 (average of N rates) for FPL and FV6, respectively. Gaseous N losses ranged from 7.6 to 13.8% of applied N and were not affected by the fertilizer time. Relative to unfertilized control, fertilized treatments increased MBN (13.4 kg N ha−1) similarly for both fertilization times. For FPL, UN was 55, 69, 86, and 103 kg N ha−1 for 0, 70, 140, and 210 kg N ha−1, respectively. For FV6, UN was 55, 46, 49, and 34 kg N ha−1 for 0, 70, 140, and 210 kg N ha−1, respectively. The losses were attributed to nitrate (NO3) leaching. Results of this experiment show that high fertilizer NUE in combination with economically competitive grain yields can be obtained when N is applied at V6 because gaseous N losses are low (less than 13.8%) and NO3 leaching would be reduced.
A Procedure for Control of pH in Cation Uptake Studies with Excised Barley Roots
Authors: Parr J. F. , Norman A. G.
Published: July 2010

A procedure for the control of pH of salt solutions in cation uptake studies with excised roots is described. Through the addition of small increments of an anionic exchange resin in OH‐ form during the absorption period, it was possible to maintain the pH at a desirable physiological level and within quite narrow limits. Whole excised barley roots exhibited maximum K+ absorption activity when pH of solutions was resin‐controlled. The rapid change in external cation concentration which occurs in high root‐to‐solution ratio experiments is not accompanied by a reduction in uptake rate between the first and sixth hour. Good reproducibility was observed with this procedure not only between replicates but also with different batches of roots.

Potassium absorption by whole excised roots and shorter root segments cut from the same barley root culture was compared. With the whole excised roots as a control, the amount of K+ absorbed at the end of 6 hours was reduced by 12% for 3‐cm. segments and by 25% in the case of 1‐cm. segments. Any apparent advantage of cutting roots into short segments to achieve greater homogeneity of subsamples is out‐weighed by a lowered net cation absorption capacity.
Photosynthesis in K‐ and Mg‐Deficient Maize (Zea mays L.) Leaves
Authors: Peaslee D. E. , Moss D. N.
Published: July 2010

Rates of photosynthesis in maize leaves were closely related to K or Mg concentrations in the leaf tissue. The critical concentrations were about 2 mg/g for K and 200 µg/g for Mg on a fresh weight basis. Normal‐appearing leaves of K‐stressed plants had sharply diminished photosynthesis rates, whereas Mg deficiency affected photosynthesis rates only after the appearance of chlorosis. Apparently Mg deficiency exerted an influence through chlorophyll deterioration while K deficiency decreased stomatal apertures. Application of the deficient nutrient caused marked recovery within 24 hours of K‐deficient leaves but not of Mg‐deficient leaves.
Sampling Soil and Foliage in a Pine Plantation
Authors: Metz Louis J. , Wells Carol G. , Swindel Benee F.
Published: July 2010

Analyses were made of N, P, K, Ca, and Mg on foliage from 256 young loblolly pine trees (Pinus taeda L.) growing in a plantation. Soil samples from beneath each tree were also analyzed for the same nutrients. Only a small portion of the variation in foliage content could be accounted for by variation in the nutrient level of the soil. Recommendations (number of plots and number of trees) are given for sampling both foliage and soil.
Generalizing Water Table Data
Authors: Nelson L. A. , Daniels R. B. , Gamble E. E.
Published: July 2010

A 17 variable multiple linear regression model was developed to predict water table levels over time for individual sites in the Coastal Plain of North Carolina. Because equations were developed individually for each site, the variables involved were mainly meteorological. They included month of year, cumulative rainfall, antecedent rainfall, and relative humidity. The model fit well in 42 of 48 sites.

By using the deviations from prediction for the datum points from which the regression equation for a site was developed, it is possible to isolate instances where the prediction was poor. These usually were cases where the water table was below the bottom of the test well for several weeks as it is frequently in wells ending in fragipan or plinthite horizons. For fall months the model tends to overpredict water levels in dry years and underpredict in wet years.

Advantages of the approach described are that it allows evaluation of the relative importance of the factors which together influence the water table, it allows comparisons among sites using the data for the same or different periods of time, and it is simple to use if electronic computational equipment is available.
Experimental Designs to Evaluate Crop Response on Adjacent Soil Mapping Units
Authors: Nelson L. A. , Buol S. W.
Published: July 2010

Soil mapping units are scaled representatives of naturally occurring soil properties and serve as reference units for technology transfer. To accurately evaluate the interactions between a given management practice and a range of soil properties represented by a soil mapping unit, tailoring of the experimental design is required. This paper identifies the design principles involved in setting up field experiments to compare the responses to different management treatments of crops grown on areas within different soil mapping units, and suggests experimental designs for this purpose. Representation of the entire soil mapping unit in the area studied is emphasized. Repetition of experiments across locations, years, or both is recommended if the inferences are to apply to more than one environment and if a test of the main effect of the area represented by the soil mapping unit is desired. Procedures for designing a series of experiments and analyzing the resulting data are discussed.
Monitoring Surface Changes of Bare Soils due to Slaking Using Spectral Measurements
Authors: Courault Dominique , Bertuzzi Patrick , Girard Michel‐Claude
Published: July 2010

The structural degradation of the soil surface due to rainfall makes the surface more susceptible to erosion. Loamy soils are particularly vulnerable to slaking, seal development, and crusting. The sealing process occurs in different stages. This study examined the possibility of using visible and near‐infrared reflectances for detecting these surface changes due to rainfall, and for defining optimal conditions for spectral measurements. Experimentation was conducted under field‐controlled conditions using a SPOT satellite simulation radiometer. Radiometric measurements were made at three solar altitudes: 0600, 1200, and 1800 h GMT, at five different stages of surface degradation following simulated rainfall. Ground measurements consisting of Munsell color, water content, and surface roughness were made simultaneously to characterize surface changes. The influence of these various factors on reflectance was analyzed. Soil water was the main source of variation in reflectance, while surface roughness was a factor of secondary importance. Reflectance increased with increased roughness and decreased soil water content. A combination of red and near‐infrared reflectances made it possible to identify different soil lines according to soil water content, solar angle, and slaking stage. Optimal conditions for monitoring surface changes were those where the solar altitude is the lowest for dry soils. Different slaking stages can also be detected by reflectances performed at 1200 h under dry conditions.
Fractal Dimension and Lacunarity of Bulk Density Determined with X‐ray Computed Tomography
Authors: Zeng Y. , Payton R. L. , Gantzer C. J. , Anderson S. H.
Published: July 2010

Quantification of soil structure is important for understanding soil behavior. The objectives of this study were to: (i) introduce the use of the point‐distribution method (PDM) for calculating fractal parameters of soil density (ρb), and (ii) introduce the use of fractal lacunarity in conjunction with the fractal dimension for quantifying small‐scale soil structure data collected with x‐ray computed tomography. Undisturbed silt loam soil cores were taken from forest and grassland sites. Additional silt loam soil collected from a nearby cultivated field was sieved and repacked in 76‐mm‐diam. cores. Four cores were packed with soil passing through a 2‐mm sieve but retained on a 1‐mm sieve (1–2 mm). Four additional cores were packed with the soil passing through a 1‐mm sieve (<1 mm). Computed tomography (CT) was used to measure small‐scale ρb of each 0.1 by 0.1 by 2 mm volume element (voxel) of a slice through a soil core. Calculation of fractal dimension and lacunarity was accomplished using the PDM on CT ρb data. Results show that CT ρb data are fractal when analyzed using the PDM. Mean fractal dimension (±SD) of the forest, grassland, <1 mm, and 1‐ to 2‐mm groups were 2.42 ± 0.13, 2.35 ± 0.14, 2.50 ± 0.025, and 2.47 ± 0.013, respectively. Corresponding mean fractal lacunarity of these four groups at a voxel size of 3.1 mm were 0.24 ± 0.025, 0.24 ± 0.019, 0.16 ± 0.005, and 0.20 ± 0.012. Fractal lacunarity, which reflects the second‐order statistics of ρb, or the uniformity of pores and aggregates within a soil core, is essential for discriminating soils of similar but slightly different structure.
In Situ Measurement of Ammonia Emissions from Organic Fertilizers in Plot Experiments
Authors: Vandré Robert , Kaupenjohann Martin
Published: July 2010

Ammonia volatilization from slurry in the field is either measured under open atmosphere from large field plots (integrated horizontal flux [IHF], mass balance) or in closed, ventilated chambers (e.g., wind tunnels), which allow the measuring of small plots but influence the climatic conditions. We conducted this study to evaluate a new method for measuring NH3 volatilization on small experimental plots under ambient climatic conditions (including rain and wind). Various pretreated cattle slurries were applied to small plots (2 by 2 m) in tillering winter wheat (Triticum aestivum L.). Ammonia collected by passive samplers on manured plots was compared with NH3 collected on standard plots, where known rates of NH3 were being released via a tubing system (standard comparison [SC] method). Forty‐five manured plots were measured simultaneously by comparison with two standard plots. The specific detection limit of this experiment was 2.5 µg NH3‐N m−2 s−1 (90 g NH3‐N ha−1 h−1). Below this value, the coefficient of variation of measured NH3 release exceeded 30%. Slurry was applied to plastic gutters on two control plots. Measured NH3 losses from these plots accounted for 78% of the absolute NH4‐N losses determined by sampling and analyzing slurry from the gutters. Measurement of the control plots was repeated during the ripening of the wheat. A strong deviation between the measurements of the two plots suggested that the accuracy of the new method is limited in dense vegetation. The results are discussed with respect to measurement accuracy and possible sources of error. A comparison with literature reports indicated that the accuracy of the SC method compared favorably to micrometeorological methods and wind‐tunnel systems.
Identification of Regional Soil Quality Factors and Indicators II. Northern Mississippi Loess Hills and Palouse Prairie
Authors: Brejda John J. , Karlen Douglas L. , Smith Jeffrey L. , Allan Deborah L.
Published: July 2010

Diversity of soil series present in a region may hinder identification of soil quality factors and indicators at a regional scale. Our objectives were (i) to identify soil quality factors for a diverse population of soils at the regional scale, (ii) to determine which factors vary significantly with land use, (iii) to select indicators from these factors that can be used with the National Resource Inventory (NRI) for monitoring soil quality, and (iv) to compare these results to a similar study involving only a single soil series. One hundred eighty‐six points representing 75 soil series in the Northern Mississippi Valley Loess Hills and 149 points representing 58 soil series in Palouse and Nez Perce Prairies were sampled from a statistically representative subset of NRI sample points and analyzed for 20 soil attributes. Factor analysis was used to identify soil quality factors and discriminant analysis was used to identify factors and indicators most sensitive to land use within each region. In the Northern Mississippi Valley Loess Hills, five soil quality factors were identified. Discriminant analysis selected potentially mineralizable N (PMN), microbial biomass C (MBC), water stable aggregates (WSA), and total organic C (TOC) as the most discriminating attributes between land uses. In the Palouse and Nez Perce Prairies, six factors were identified. Discriminant analysis selected TOC and total N as the most discriminating attributes between land uses. The soil quality factors were similar among three of the four regions, but TOC was the only indicator common to all regions for distinguishing among land uses.
Equilibrium and Nonequilibrium Transport of Boron in Soil
Authors: Communar G. , Keren R.
Published: July 2010

Though B adsorption on soil is considered to be reversible and rapid, the use of models based on the assumption of local equilibrium often provide poor descriptions of B transport in soil columns. This study was conducted to reconcile inconsistencies between the findings of transport and batch‐adsorption experiments. The B displacement experiments in the loamy sand soil were conducted at various pH values (6.9, 8.3, and 9.3) and pore‐water velocities (3.6 and 0.16 cm h−1). The B transport in soil was strongly controlled by the pH‐dependent and rate‐limited adsorption (the soil heterogeneity was insignificant). The impact of rate‐limited adsorption was dependent on pore‐water velocity. The two‐site (local equilibrium–nonequilibrium [LE–NE]) model accounting for the existence of equilibrium and nonequilibrium adsorption sites was used to describe nonideal transport of B in loamy sand soil. The Keren's phenomenological equation was used to simulate B adsorption on equilibrium sites and the Langmuir rate equation was applied for the rate‐limited sites. The B adsorption parameters in the model were obtained from batch experiments. The fraction parameter f (representing the fraction of soil in which B adsorption is assumed to be rate‐limited) and the dimensionless rate coefficients γ0 (the Damkohler number) for B adsorption–desorption reactions were calculated by fitting the LE–NE model to the breakthrough curves (BTCs) for B measured from the fast‐velocity experiments. The fraction parameter was >0.9, indicating that most of B adsorption sites on the loamy sand soil are rate‐limited. The γ0 values calculated from B adsorption BTCs were greater than that for desorption, indicating that hysteresis in B adsorption–desorption processes can be observed during nonequilibrium B transport in soil. The LE–NE model well reproduced the general B transport behavior in the soil over the observed pH and velocity ranges.
Diversity and Distribution of Avifauna of Lakkavalli Range Forest, Bhadra Wildlife Sanctuary, Western Ghat, India
Authors: Harisha M. N. , Hosetti B. B.
Published: July 2010

A total of 132 species of birds belonging to 34 families under 11 orders were recorded during the study period between April 2007 to March 2008 in the Lakkavalli range forest, Bhadra Wildlife Sanctuary, Western Ghat, Karnataka, India. There were 112 resident, 12 winter migratory, 7 local migratory and one summer migratory birds, respectively. Among the birds recorded in the study area, about 49% were insectivores and other dominating types included mixed diet 25%, omnivores 11% carnivores 9%, granivores 3% and frugivores 3%, respectively. Species richness was maximum in the early winter and relatively less in other seasons. Key words: Western Ghat, Lakkavalli, avifauna diversity, landscape. DOI: 10.3126/eco.v16i0.3469ECOPRINT 16: 21-27, 2009
MISFEASANCE AS AN ORGANIZING NORMATIVE IDEA IN PRIVATE LAW
Authors: Benson Peter
Published: July 2010

The familiar principle that there is no liability for nonfeasance but only for misfeasance is often presented as reflecting a merely factual difference between acts and omissions and is discussed as a discrete issue in tort law, alongside and after the treatment of general principles. In striking contrast, Francis Bohlen took this distinction to be normative, not factual, and wrote that none is more deeply rooted in and more fundamental to the common law. This article investigates whether his contention is sound and, if so, how it might be accounted for. Its main thesis is that, properly understood, the misfeasance requirement is a central organizing normative idea in private law, providing a unifying moral framework for specifying the varieties of private-law relations. Part ii fixes the meaning and the role of misfeasance through a discussion of a variety of situations in which the law denies liability for even foreseeable loss. We see that the misfeasance requirement makes a certain kind of protected interest, namely, an exclusive ownership interest, the necessary condition of liability in private law. But the character of this ownership and of the sort of relation that holds between individuals as bearers of this interest requires explanation. Moreover, the fact that misfeasance makes this the only relevant conception of protected interest needs to be justified from a moral point of view. Part iii provides an account of the conceptual–normative genesis of the basic private-law relation of rights and correlative duties involving interests of this kind, with illustrations drawn from different areas of private law. Parts iv and v take up the further question of the moral acceptability of the misfeasance requirement from the standpoint of liberal justice.
Bartholomew Sulivan and early watercolours of Falkland Islands vegetation in the National Botanic Gardens, Dublin
Authors: MOORE D. M. , SCANNELL M. J. P.
Published: July 2010

Three hitherto undocumented watercolours in the possession of the National Botanic Gardens, Dublin, are found to depict botanically interesting views of Falkland Islands' vegetation and an historically important painting of Port Louis about 1842, when it was the capital of the archipelago. From the evidence available it seems clear that these paintings were prepared by either Bartholomew J. Sulivan or his wife during a surveying voyage to the Falkland Islands in 1842–43, when he commanded the brig Philomel. Some associated herbarium specimens seem to have been collected by B. J. Sulivan during 1838 when he visited the Falkland Islands as Lieutenant aboard the surveying ketch Arrow.
Mary Elizabeth Barber: South Africa's first lady natural historian
Authors: COHEN ALAN
Published: July 2010

An account of the life of a nineteenth century South African frontiers-woman who, without any formal education, made a name for herself as a plant collector and natural historian. Born in England, she emigrated as a child of 2 years of age with her family as one of the British settlers to the Grahamstown area in 1820. From the age of 20 she corresponded with several eminent English biologists, and had scientific papers on botany and entomology published in a number of journals. She was later involved in the early discoveries of diamonds and gold in South Africa. One of her sons was amongst the first to see and paint the Victoria Falls after their discovery by Livingstone. With her younger brother James Henry Bowker she collected and sent back a large number of plants, many of them previously unknown, to the herbarium of Trinity College, Dublin, and the Royal Botanic Gardens, Kew. She collaborated with her older brother Thomas Holden Bowker in building up one of the earliest collections of stone-age implements in South Africa, some of which are now in the British Museum.
Examining the association between delay in diagnosis and decreased survival in bladder cancer
Authors: Porter Michael P.
Published: July 2010

Delays in diagnosis and definitive treatment are associated with poorer survival in observational studies of patients with bladder cancer. Quality of care may be as important as tumor biology in explaining this association.