bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Japanese BeetlePopillia japonicaLarvae and Fungal Endophytes on Competition between Turfgrasses and Dandelion
Authors: Richmond Douglas S. , Grewal Parwinder S. , Cardina John
Published: July 2014

In a series of greenhouse experiments, we examined the influence of below‐ground herbivory by larvae of the Japanese beetle,Popillia japonicaNewman, on performance and competitive interactions between dandelion,Taraxacum officinaleWeber, and two turfgrass species,Lolium perenneL. (perennial ryegrass) andFestuca arundinaceaSchreb. (tall fescue) infected or uninfected byNeotyphodiumendophytes. In doing so, we aimed to determine how below‐ground insect feeding and endophyte infection might influence the ability of dandelion to act as a turfgrass weed. In monocultures of perennial ryegrass or tall fescue, herbivory significantly reduced the number of tillers per plant and above‐ and below‐ground biomass. Endophyte infection significantly reduced perennial ryegrass tillers but significantly increased the number of tall fescue tillers and above‐ and below‐ground biomass. Herbivory had no significant influence on dandelion growth parameters in monocultures. In mixtures of dandelion and either grass species, herbivory significantly reduced the number of grass tillers and above‐ and below‐ground biomass, whereas endophyte infection significantly reduced the number of perennial ryegrass tillers but had little influence on tall fescue. Herbivory significantly increased the number of dandelion leaves and above‐ and below‐ground biomass in mixtures with perennial ryegrass or tall fescue. Endophyte infection had no significant influence on Japanese beetle larval survival or biomass in monocultures or mixtures. Findings indicate that below‐ground herbivory by Japanese beetle larvae alters competitive interactions between grasses and dandelion in a way that favors dandelion. Data support the view that endophyte‐related effects on interactions between plants may not always be predictable and that below‐ground herbivory may not affect endophyte‐infected and uninfected plants differentially.
Introgression in Common Bean × Tepary Bean Interspecific Congruity‐Backcross Lines as Measured by AFLP Markers
Authors: Muñoz L. C. , Blair M. W. , Duque M. C. , Tohme J. , Roca W.
Published: July 2014

Congruity and recurrent backcross interspecific hybrids between common bean (Phaseolus vulgaris L.) and tepary bean (P. acutifolius A. Gray) were compared for the amount of introgression occurring between genomes by amplified fragment length polymorphism (AFLP) markers. A total of 60 genotypes were analyzed of which 34 were obtained by congruity backcrossing, four by single backcrossing and 14 by recurrent backcrossing, with parental and representative tepary and common bean genotypes used as controls. The level of introgression of tepary bean marker bands into the common bean genome background was higher in the congruity backcross lines than in the recurrent backcross derived genotypes. Congruity backcross lines derived from five cycles of interspecific hybridization showed an average introgression of 8.8% of AFLP bands while lines derived from a single backcross with the same parents showed an average introgression of only 5.2% of the bands. For both types of backcrossing, these levels of introgression were significantly below those expected. A multiple correspondence analysis showed three major clusters consisting of the common bean accessions and interspecifics with low rates of introgression, an intermediate group of interspecific congruity backcross lines with higher rates of introgression and a more distant group that included all the tepary bean accessions. These results suggest that congruity backcrossing can be used to increase introgression rates between the species and to transfer favorable oligogenic traits from tepary bean to common bean but that levels of introgression between the species remains low.
Molecular Characterization, Compositional Analysis, and Germination Evaluation of a High‐Oleic Soybean Generated by the Suppression ofFAD2‐1Expression
Authors: Brink Kent , Chui Chok‐Fun , Cressman Robert F. , Garcia Patrick , Henderson Nancy , Hong Bonnie , Maxwell Carl A. , Meyer Knut , Mickelson James , Stecca Kevin L. , Tyree Cheri W. , Weber Natalie , Zeng Weiqing , Zhong Cathy X.
Published: July 2014

Soybean [Glycine max(L.) Merr.] oil is one of the most consumed and highest produced vegetable oils. However, the high percentage of polyunsaturated fatty acids in soybean oil limits its stability and shelf life. Here we report the generation and characterization of a high oleic acid soybean event (305423 soybean) that has an elevated content of monounsaturated oleic acid and reduced presence of polyunsaturated linoleic acid and linolenic acid. This transgenic event was generated by the insertion of a soybean ω‐6 desaturase (FAD2) gene fragment (gm‐fad2‐1), resulting in the suppression of endogenousFAD2‐1expression, and a modified version of the soybeanacetolactate synthase(ALS) gene (gm‐hra), used as a selectable marker. Molecular characterization revealed that 305423 soybean harbors four DNA inserts containing multiple copies of complete and partialgm‐fad2‐1gene cassettes and a single copy of the intactgm‐hragene cassette. However, these DNA inserts seemed to be inherited together without segregation. The suppression of endogenousFAD2‐1led to an increase of oleic acid (18:1) from 211 to 765 g kg–1along with concurrent reduction of both linoleic acid (18:2) from 525 to 36.2 g kg–1and linolenic acid (18:3) from 93.5 to 53.9 g kg–1out of total fatty acyl groups. The 305423 soybean was also subjected to nutrient composition analyses and phenotypic and agronomic performance evaluations and found to be comparable to the control soybean except for the expected traits.
Genotype × Environment Interaction of Maize Grain Yield Using AMMI Biplots
Authors: Ndhlela Thokozile , Herselman Liezel , Magorokosho Cosmos , Setimela Peter , Mutimaamba Charles , Labuschagne Maryke
Published: July 2014

Maize (Zea mays) is the most important cereal crop in Zimbabwe and is grown by both large‐ and small‐scale farmers who are located in different agro‐ecological zones of the country. The development and dissemination of adapted and high‐yielding maize cultivars to these agro‐ecological zones involves conducting multi‐environment trials (METs). This study was conducted with the objectives of i) understanding complex G × E interaction and stability of single cross hybrids generated using CIMMYT elite drought tolerant lines and Department of Research and Specialist Services (DR&SS) elite drought susceptible lines for grain yield across stress and nonstress environments and ii) to identify genotypes to recommend for further use in the breeding program. Initially, yield data of 80 maize single cross hybrids tested across seven environments during the 2009 to 2010 and 2010 to 2011 seasons were analyzed using the additive main effects and multiplicative interaction (AMMI) biplot method. The analysis was further done for 20 best performing genotypes to facilitate less congested graphical presentation. Combined analysis of variance showed highly significant differences for the G × E interaction, indicating the possibility of selection for stable genotypes. The five AMMI interaction principal component analyses (IPCAs; IPCA1, IPCA2, IPCA3, IPCA4, and IPCA5) explained 82.41% of the variation and they were highly significant. The results showed three genotypes with high yield performance and broad adaptability whilst narrow adaptations were also observed. Agricultural Research Trust Farm was the most powerful site in discriminating among genotypes and the most representative environment.
Characterization of a Multiseeded (msd1) Mutant of Sorghum for Increasing Grain Yield
Authors: Burow Gloria , Xin Zhanguo , Hayes Chad , Burke John
Published: July 2014

Sorghum [Sorghum bicolor (L.) Moench] has branched panicles with primary, secondary, and tertiary branches. These inflorescence branches are composed of a terminal triplet spikelet, consisting of one sessile (directly attached to the branch) and two pedicellate (spikelets attached to the branch through a short pedicel), followed by one or more spikelet pairs (one sessile and one pedicellate). In BTx623, and most sorghum lines, only the sessile spikelets can develop into seeds and the pedicellate spikelets, occasionally developing anthers, eventually abort. Here, we report the isolation and characterization of a stable multiseeded (msd1) mutant of sorghum (in BTx623 background, referred to as wild‐type [WT]) in which both sessile and pedicellate spikelets are fertile. In addition, this mutant displayed increased length and total number of primary and secondary inflorescence branches. Genetic analysis showed that this multiseeded mutation is a recessive trait. Pedicellate spikelets in msd1 mutants exhibited complete flower with functional ovary and anthers, of which 75 to 95% can develop into viable seeds. The individual msd1 seeds are smaller than WT; however, the results indicated that this reduction in seed weight can be compensated by the increase in seed number. The total seed weight per panicle in msd1 mutants was increased by 30 to 40% as compared to the WT. Further experiments are needed to demonstrate whether the msd1 mutation can increase grain yield under field conditions.
Prediction of Dry Matter Yield of Hybrid Forage Corn Grown for Silage
Authors: Islam M.R. , Garcia S.C.
Published: July 2014

Predicting yield at an early growth stage will allow producers to optimize the amount and timing of N to maximize crop yield. The objective of this study was to evaluate the usefulness of individual measurements and combinations of normalized difference vegetation index (NDVI) and plant height (PH) as early stage predictors of corn (Zea mays L.) dry matter (DM) yield for silage. Corn was grown during 2 yr in Camden, Australia with different rates of pre‐and post‐sown N fertilizer, with or without irrigation, and harvested for silage at physiological maturity. In both years, NDVI and PH data were collected at 3‐, 5‐, 6‐ and 8‐leaf stages (V) and their relative values were calculated by using the reference treatment (nonlimiting N and water). In contrast to the actual data, the relative DM yield data in both years settled on the same regression line against relative NDVI indicating that expressing DM yield and NDVI in relative terms reduces the variation due to year and may be more useful than the actual values for prediction purposes. The accuracy of prediction was higher for PH than NDVI data. However, the best accuracy in DM yield prediction at V6 stage was obtained with combinations of relative PH × NDVI (r2 ≥ 0.78). As slopes of all indicators were similar in stages from V6 to V8 stages, all indicators may be used to predict DM yield of forage corn grown for silage as early as V6 stage. Plant height and PH × NDVI can be used to predict DM yield of forage corn at V5 stage because slopes of these indicators were similar from V5 to V8 stages.
Intercropping Wheat and Beans: Effects on Agronomic Performance and Land Productivity
Authors: Chapagain Tejendra , Riseman Andrew
Published: July 2014

Declining land productivity associated with soil degradation is a significant issue for intensive wheat production. An intercropping system combining wheat and grain legumes may provide a farmwide production system that fulfills both economic and environmental concerns. We grew spring wheat (Triticum aestivum L. ‘Scarlet’) as a monoculture and intercropped with either a common bean cultivar (Phaseolus vulgaris L. ‘Red Kidney’ or ‘Black Turtle’) or a fava bean cultivar (Vicia faba L. ‘Bell’) without fertilizer in rows of wheat/bean 1:1 and 2:1 as well as broadcast arrangements during 2011 and 2012 to assess the impact of different genera (Vicia and Phaseolus) and cultivars (Red kidney or Black Turtle) on the wheat performance, land productivity, N and C accumulation in aboveground biomass, and soil mineral N balance. As baseline, the monoculture wheat plots yielded 3.2 t ha−1. However, wheat–fava bean plots displayed higher land equivalent ratio (LER) and total land outputs (TLO) with increased land productivity of 50% in the 1:1 and 32% in the 2:1 arrangements. Intercropped plots in row arrangements also improved wheat biomass nitrogen and grain protein content compared with monoculture plots. Wheat–fava bean in the 1:1 arrangement accumulated the highest N (34 kg ha−1, i.e., 176% higher) and organic C (2138 kg ha−1, i.e., 26% higher) in shoot biomass compared with monocultured wheat. Both NH4+ and NO3− pools were higher in intercrop plots with the highest mineral N balance in wheat‐fava bean in the 1:1 arrangement (+0.2 mg NH4+ and +1.1 mg NO3−kg‐1 dry soil). This study demonstrates that intercropping wheat with fava bean is an efficient strategy to increase land productivity while also increasing forage and soil quality.
Stocking Method, Animal Behavior, and Soil Nutrient Redistribution: How are They Linked?
Authors: Dubeux J.C.B. , Sollenberger L.E. , Vendramini J.M.B. , Interrante S.M. , Lira M.A.
Published: July 2014

Choice of stocking method may impact soil, plant, and animal responses. This 3‐yr study evaluated stocking method effects on animal behavior and soil nutrient concentration in ‘Pensacola’ bahiagrass (Paspalum notatum Flügge) pastures. Stocking methods were continuous stocking and rotational stocking with 1‐, 3‐, 7‐, and 21‐d grazing periods and a 21‐d resting period. Responses were measured in three zones based on distance from shade and water (Zone 1, 0–8 m; Zone 2, 8–16 m; Zone 3, >16 m). Indices were calculated to weight number of dung and urine events and time spent by cattle in a zone by the proportion of the total pasture and paddock area represented by that zone. Indices were most uniform (∼1) across zones for rotational stocking with short grazing periods and generally increased linearly in Zones 1 and 2 with increasing grazing period. Except for N, soil nutrient concentration was not affected by stocking method. In zones closest to shade and water, soil nutrients accumulated for all methods in the surface 8 cm but not in the 8‐ to 23‐cm layer. Air temperature, wind speed, and temperature–humidity index explained 49% of the variation in time cattle spent under shade, confirming the importance of the environment in animal behavior. In warm environments, structural features of stocking method (e.g., the position of shade and water) have a greater effect on animal behavior and distribution in the landscape than do stocking density‐mediated effects on competition for forage.
Stolon Type and Soil Burial Effects on ‘Tifton 85’ Bermudagrass Establishment
Authors: Baseggio M. , Newman Y.C. , Sollenberger L.E. , Fraisse C. , Obreza T.
Published: July 2014

‘Tifton 85’ bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt Davy] is a highly productive warm‐season grass, but it must be planted vegetatively using aboveground stems (stolons) or rhizomes. Use of stolons vs. rhizomes provides advantages of reduced cost, greater shoot production, and more planted area per hectare of nursery. However, establishment failures have been reported by producers under challenging environmental conditions common to the Coastal Plain region of the southeastern United States. Thus, strategies for harvesting and planting stolons need to be evaluated further. The objective was to assess the effect of stolon type (length and stolon position) and degree of stolon burial by soil (total or partial) at planting on Tifton 85 bermudagrass establishment. Partial burial of stolons at planting accelerated emergence and increased bermudagrass percentage cover and dry matter harvested at season end. Total burial resulted in only half as many shoots (3.5 vs. 7.8 m−2) as partial burial in 2011; total burial resulted in no emergence in 2012. Partial burial led to as much as 90% bermudagrass soil cover, while total burial provided 66 and 0% in 2011 and 2012, respectively. Also, partially buried stolons yielded 1000 kg ha−1 of forage more than totally buried in both years. This finding suggests the planting equipment should be set to achieve shallow planting, ensuring that some parts of the stolons remain uncovered. Stolon type is not as critical as the degree of soil cover on the stolons, which need to remain only partially but not totally buried.
Inversion of Soil Conductivity Profiles from Electromagnetic Induction Measurements
Authors: Hendrickx J. M. H. , Borchers B. , Corwin D. L. , Lesch S. M. , Hilgendorf A. C. , Schlue J.
Published: July 2014

Noninvasive electromagnetic (EM) induction techniques are used for salinity monitoring of agricultural lands and contaminant detection in soils and shallow aquifers. This study has four objectives. The first objective is to summarize an earlier linear model of the response of the EM38 ground conductivity meter and to discuss a more accurate nonlinear response model. The second objective is to verify experimentally whether the linear and nonlinear models derived for homogeneous media are valid in heterogeneous soil profiles. The third objective is to present an inverse procedure that combines the nonlinear model with Tikhonov regularization. The fourth objective is the experimental verification of inverse procedures with the linear and nonlinear models for inversion of soil conductivity profiles using aboveground electromagnetic induction measurements on fourteen saline Californian soil profiles. The linear and nonlinear models derived for homogeneous media are indeed valid in heterogeneous soil profiles. However, since the errors of the linear model are approximately double those of the nonlinear model, the latter is the preferred one. A small difference was found in the errors of the inverse procedures between the linear and nonlinear models. In this study, the inverse procedures with the linear model and with the nonlinear model produce equally good solutions at EM38 measurements below 100 mS m−1, while at higher electrical conductivities the inverse procedure with the nonlinear model appears to yield slightly better results. The inverse procedure with the linear model is preferred for all conductivities since it needs considerably less computer resources.
Prediction of Dispersivity for Undisturbed Soil Columns from Water Retention Parameters
Authors: Perfect E. , Sukop M. C. , Haszler G. R.
Published: July 2014

Dispersivity (α) is a required input parameter in solute‐transport models based on the advection‐dispersion equation (ADE). Normally α is obtained from miscible‐displacement experiments. This dependency on inverse procedures imposes a severe limitation on our predictive capability. If solute breakthrough curves and soil hydraulic properties were measured simultaneously, pedotransfer functions could be developed to predict α from independent measurements. In this study, short (6 cm long) undisturbed columns were employed to investigate the relationship between α and the water‐retention curve as parameterized by the air‐entry value (ψa) and Campbell exponent (b). We worked with 69 columns from six soil types ranging in texture from loamy sand to silty clay, conventional‐till and no‐till management practices, steady‐state saturated flow conditions, and a step decrease in CaCl2 concentration from 0.009 to 0.001 M Breakthrough curves were measured by monitoring changes in effluent electrical conductivity using a computerized data acquisition system. Estimates of α (calculated using the method of moments) ranged from 1 to 192 mm for the six soil types. Stepwise multiple‐regression analysis explained ∼50% of the total variation in α, and indicated that dispersion increased as ψa and b increased. Since both ψa and b increase with increasing clay content, α also increases moving from coarse‐ to fine‐textured soils. Our regression equation can be used as a pedotransfer function to predict α from existing databases of soil hydraulic properties. Further research is needed to independently validate its predictive capability, and to develop strategies for upscaling the model predictions.
Spatial and Statistical Similarities of Local Soil Water Fluxes
Authors: Si Bing Cheng
Published: July 2014

Understanding the spatial and statistical distribution of soil water flux in a field is fundamental for stochastic modeling soil water flow and chemical transport in spatially variable soils. The objective of this study was to examine the persistence of the spatial pattern and statistical distribution of local soil water flux for different application rates during constant flux rainfall infiltrations. A series of constant flux‐infiltration experiments were conducted in a spatially variable field. The local soil water fluxes for each of the 0‐ to 0.2‐, 0‐ to 0.4‐, 0‐ to 0.6‐, and 0‐ to 0.8‐m depths were determined from the change of water storage as a function of time before the wetting front passes the end of vertically installed time domain reflectometry (TDR) probes. The spatial similarity (persistent spatial pattern) of the measured soil water flux for different application rates at four depths was examined using Spearman rank correlation coefficient. Results showed that there was no persistent spatial similarity among measured soil water fluxes for the 0‐ to 0.2‐, 0‐ to 0.4‐, 0‐ to 0.6‐, and 0‐ to 0.8‐m depths. This indicates that transient infiltration experiments with different application rates have different flow pathways for each of the 0‐ to 0.2‐, 0‐ to 0.4‐, 0‐ to 0.6‐, and 0‐ to 0.8‐m depths. The statistical similarity (persistent statistical distribution) of soil water flux for different application rates was examined using histograms. Chi‐square tests indicated that the histograms of soil water flux for different application rates were different for each of the 0‐ to 0.2‐, 0‐ to 0.4‐, 0‐ to 0.6‐, and 0‐ to 0.8‐m depths, suggesting the stochastic convective flow model may not be used to predict flow and transport in this field for different application rates.
Imaging Fluorescent Dye Concentrations on Soil Surfaces
Authors: Vanderborght Jan , Gähwiller Paul , Wydler Hannes , Schultze Ute , Flühler Hannes
Published: July 2014

To investigate transport processes in soils, detailed information about the spatial distribution of solutes is required. We describe a method to obtain concentration maps of fluorescent tracers on cross sections of soil cores with a high spatial resolution. The fluorescence signal of two dye tracers, brilliant sulfaflavine (BF; 1H‐Benz(de)isoquinoline‐5‐sulfonic acid, 2,3‐dihydro‐6‐amino‐1,3‐dioxo‐2‐(p‐tolyl)‐, monosodium salt) and sulforhodamine B (SB; xanthylium, 3,6‐bis(diethylamino)‐9‐(2,4‐disulfophenyl)‐, inner salt, sodium salt), was imaged on the exposed cross sections. The fluorescence signal was corrected for variable illumination light intensity and optical properties of the soil across the exposed surface. Correction factors for varying optical soil properties were derived from the image of the reflected excitation light at the exposed surface. Linear calibration relations related the corrected fluorescence image to the total tracer concentration (Ct) map, that is, mass of dye dissolved in the soil solution and sorbed to the soil particles per unit volume bulk soil. Corrections for varying optical properties of the soil surface were important to reduce the uncertainty of the concentration that was estimated from the fluorescence signal. For BF, the calibration relations were different for different soil materials and a soil specific calibration had to be used. Variations in background fluorescence were an important source of uncertainty of the BF concentration estimates but can be overcome by applying higher concentrations. For SB, variations in calibration relations and in the background fluorescence were considerably smaller, and so is the uncertainty of the estimated SB concentrations.
Desorption Kinetics of Cadmium2+ and Lead2+ from Goethite
Authors: Glover Leslie J. , Eick Matthew J. , Brady Patrick V.
Published: July 2014

It is generally accepted that trace metal concentrations in soil solution are primarily controlled by sorption and desorption reactions at the particle‐water interface. While numerous studies have been conducted to understand adsorption of these metals to soil minerals, less is known about long‐term adsorption‐desorption processes. The objective of this study was to examine the influence of residence time and organic acids on the desorption of Pb2+and Cd2+ from goethite. Adsorption experiments were conducted at pH 6.0 for 1 wk (short‐term) and 20 wk (long‐term). Lead adsorption was nearly complete after 4 h, with very little additional sorption occurring during a 20‐wk period. In contrast, Cd showed a continuous slight increase in the remaining adsorption. Desorption experiments were conducted at pH 4.5 and desorption kinetics for Pb2+and Cd2+ were slow compared with the sorption reaction. Trace metal removal from the goethite surface was not completely reversible during an 8‐h desorption period for all of the experiments, except for short‐term Cd2+ in the presence of salicylate. For all experiments except long‐term Pb2+ desorption, the quantity of metal desorbed from goethite followed the order salicylate > NaNO3 > oxalate. It is postulated that the greater effectiveness of salicylate compared with oxalate was related to the ability of oxalate to form bridging or ternary complexes between the metal and the goethite surface. For all experiments except Pb2+ sorption in the presence of oxalate a greater quantity of metal was desorbed for the short‐term compared with the long‐term experiment. However, these results were only statistically significant for Pb2+ in the presence of salicylate. These results suggest that residence time effects observed by many researchers are much less prevalent at low pH values, and hence natural or anthropogenic reduction in soil pH may reduce the ability of the soil to naturally sequester trace metal cations over time.
Management Effects on Barley Straw Decomposition, Nitrogen Release, and Crop Production
Authors: Beare M. H. , Wilson P. E. , Fraser P. M. , Butler R. C.
Published: July 2014

Development of sustainable‐crop production systems depends on identifying effective strategies for the management of postharvest crop residues. The effects of time‐of‐incorporation (autumn‐incorporated [AI] vs. spring‐incorporated [SI] and irrigation (irrigated[Irr] vs. nonirrigated[Nirr]) on barleyHordeum vulgareL. straw decomposition and microbial activity were investigated in relation to soil N availability and crop production over one cropping cycle in Canterbury, New Zealand. Over the winter‐fallow period, the weight loss of AI barley straw averaged 33% as compared with 18% for surface straw of SI treatments. By harvest, nearly all of the difference in mass loss between AI and SI straw (17%) from NIrr treatments could be attributed to decomposition in the fallow period. Irrigation increased straw decomposition during the cropping period by 68% in AI treatment compared with only 37% in SI treatment. The effect of winter‐straw placement on the response of barley straw to summer irrigation was related to the size of the residue‐borne microbial populations at the start of the cropping period. Although relatively little N was released (<5 kg N ha−1) from decaying barley straw, cultivation, and incorporation of straw in autumn (AI) did result in greater topsoil (0–25 cm) mineral N levels during the winter period as compared with the SI treatment. Overall, Irr and AI of straw increased the dry matter production and N uptake of the summer barley crop, resulting in a concomitant decrease in soil mineral N levels relative to Nirr SI treatments. The mechanisms that explain this difference in crop response to winter residue management require further investigation.
Soil Mineralogy and Texture Effects on Crust Micromorphology, Infiltration, and Erosion
Authors: Wakindiki I. I. C. , Ben-Hur M.
Published: July 2014

Soil mineralogy and texture have substantial effects on aggregate stability and, therefore, may influence infiltration rate (IR) and soil loss under rainfall. The objective was to study the effects of soil mineralogy and texture on crust micromorphology, infiltration, and erosion. Five soils with differing properties were subjected to 80 mm of simulated rainfall. The aggregate stability of these soils was determined by the fast wetting method. The mean‐weight diameters of the particles after the fast wetting were 2.8 mm in the clayey kaolinitic soil, 0.25 and 0.31 mm in the clayey and sandy loam montmorillonitic soils, respectively, and 0.84 and 0.87 mm in the clayey nonphyllosilicate soils. The final IR was 20.5 mm h−1in the clayey kaolinitic soil and ≤9.3 mm h−1in the remaining soils. Scanning electron microscope (SEM) observations indicated that the kaolinitic soil had a thin crust (∼0.1 mm) containing large particles (∼0.1 mm), whereas the montmorillonitic soils had thicker crusts (>0.2 mm) comprising either small (∼0.02 mm) particles with a very developed washed‐in zone underneath or large (∼0.2 mm) ones with fine material between them. The crust layer in the nonphyllosilicate soils was ∼0.2 mm thick and composed of fine particles ∼0.01 mm. The high aggregate stability and the low dispersivity of the kaolinitic soil, which minimized soil detachment, and its low runoff, which minimized its transport capacity, limited the soil loss to 0.33 kg m−2, whereas the low aggregate stability and high runoff of the montmorillonitic soils contributed to their soil losses of 1.24 and 1.14 kg m−2The intermediate aggregate stability and the high runoff of the nonphyllosilicate soils accounted for their intermediate soil losses of 0.75 and 0.8 kg m−2
Soil Analyses as Indicators of Phosphorus Response in Young Eucalypt Plantations
Authors: Mendham Daniel S. , Smethurst Philip J. , Holz Greg K. , Menary Robert C. , Grove Tim S. , Weston Chris , Baker Tom
Published: July 2014

The use of P fertilizer in Eucalyptus plantations can result in significant and economically viable increases in timber production. Soil analyses could potentially indicate sites requiring more P fertilizer than is currently applied and prevent excess P fertilizer application on sites where little or no response would be obtained. The ability of several soil P analyses to predict first year growth responses of E. nitens and E. globulus to P fertilizer was assessed in 24 previously established field experiments situated in southeast and southwest Australia on a range of soil types. Soil P analyses that were assessed included an intensity‐based analysis (CaCl2 extracted P), quantity‐based analyses (total P, bicarbonate extracted P, and Bray No. 2 P), and quantity–intensity relationships (P adsorption curves). An excellent relationship was found between CaCl2‐extractable P (range: 26–162 μg kg−1, R2 = 0.83) and first year growth response to P applied at planting for 21 of the 24 field experiments. Quantity‐based P analyses, such as bicarbonate P (range: 2–63 μg g−1, R2 = 0.43), Bray No. 2 P (range: 0.1–15 μg g−1, R2 = 0.30), acid‐extractable P (range: 0.6–11 μg g−1, R2 = 0.37), and total P (range: 0.038–3.5 mg g−1, R2 = 0.39) did not correlate as well with plant growth response to P application. However, quantity‐based P analyses may be useful if specific calibrations were developed for a limited range of soils. Inclusion of P adsorption data in multiple regressions of soil P concentration against relative yield generally did not improve the relationships. The excellent relationship between plantation response to P fertilizer and soil P intensity suggested that such analyses may be useful for managing P fertilizer in eucalypt plantations across the wide range of sites where eucalypts are currently being planted.
Pathways of Soil Phosphorus Transformations after 8 Years of Cultivation under Contrasting Cropping Practices
Authors: Zheng Zhiming , Simard Régis R. , Lafond Jean , Parent Léon E.
Published: July 2014

The knowledge of P transformations is essential to understand the P behaviour in soils. Organic (Po) and inorganic (Pi) P fractions were obtained from the 0‐ to 30‐ and 30‐ to 90‐cm layers of a Labarre silty clay (fine, mixed, frigid, Humic Cryaquept) by a sequential extraction. Barley (Hordeum vulgare L.) monoculture and 3‐yr barley‐forage rotation as main plots, and two nutrient sources (mineral fertilizer and liquid dairy manure) as subplots were studied. Path analysis was used to describe soil P transformations between the falls of 1989 and 1997. Nutrient source was the main factor affecting P transformations in the 0‐ to 30‐cm soil layer, whereas crop rotation predominated in the subsoil. Pathways differed more for Po than for Pi pools. In the 0‐ to 30‐cm soil layer, 86 to 97% of the variation in resin‐P was the direct effect of added Pi The NaHCO3‐Pi and Po were sensitive to crop rotations and nutrient sources, and were transitory pools of soil P. The NaOH‐Pi was a sink for added Pi and a source of NaHCO3‐Pi Labile Pi tended to store as NaOH‐Po, which was the sink for added Po and immobilized soil Pi in the mineral fertilizer systems. Conversely, the NaOH‐Po was mineralized and contributed to labile Pi in dairy manure systems. The NaOH‐Po acted as store of subsoil Po in the monoculture but was the main source of labile P in the rotation systems. The P transformations in this Cryaquept were strongly influenced by nutrient sources and crop rotations.
Rapid water flow instrumentation
Authors: Troyer Wallace , Skopp J.
Published: July 2014

Measuring high flow rates for small quantities of water is useful when determining soil hydraulic properties. A system that measures such flow rates precisely and accurately is not currently on the market. We present a flow measuring system, which uses pressure transducers and a data logger. This flow system has three advantages over a scale: (i) an automated interface allows precise initiation and measurement of system response, (ii) the ability to measure intervals as short as a tenth of a second, and (iii) quick response. Tests show that the system is highly repeatable, accurate, and responsive. A direct comparison of the flow system and scale output collected simultaneously shows that the flow system was more responsive than the scale in the early stages of the test, though the total output of both was similar. The instrumentation is adaptable for both laboratory and field methods. The flow rate can be adjusted simply by changing the diameter of the cylinder used. The flow system is built from off‐the‐shelf parts, except the control circuitry, and can be built for less than $1000.
Pore‐Space Dynamics in a Soil Aggregate Bed under a Static External Load
Authors: Ghezzehei Teamrat A. , Or Dani
Published: July 2014

The loose and fragmented soil structure that results from tillage operations provides favorable physical conditions for plant growth. This desirable state is structurally unstable and deteriorates with time because of overburden, external stresses, and capillary forces. The objective of this study was to model these structural changes by coupling soil intrinsic rheological properties with geometry and arrangement of aggregates represented as monosized spheres. Calculations of interaggregate stresses and strains, and associated changes in density and porosity, were performed for a rhombohedral unit cell. Soil rheological properties determined by application of steady shear stress were used for calculations of strains under steady interaggregate stresses. The models developed herein correspond to the initial stage of deformation when discrete aggregates exist. At strains exceeding 0.12 the interaggregate voids are isolated and the current model no longer applies and an alternative approach is presented elsewhere. Unit cell calculations were up scaled to an aggregate‐bed scale by considering a one‐dimensional stack of unit cells, which allows only vertical stress transmission. The stress acting at an interaggregate contact is fully accommodated (dissipated) by viscous flow when it exceeds the yield stress (strength) of the aggregates. The stress is fully transmitted to subsequent unit cells when it is less than the yield stress. Plausibility of the models was demonstrated by illustrative examples that highlight the different features of the models. The results were in qualitative agreement with observations from the literature for deformation of either loose structure, and for highly dense cases close to maximal bulk density.
Linking Soil Microbial Activity to Water‐ and Air‐Phase Contents and Diffusivities
Authors: Schjønning Per , Thomsen Ingrid K. , Moldrup Per , Christensen Bent T.
Published: July 2014

Quantification of in situ soil microbial activity is indispensable to improve manipulation of nutrient turnover in soil and optimize crop nutrient supply. We sampled 100‐cm3 cores of undisturbed arable soil at three locations along a naturally occurring clay gradient (L1: 11% clay; L3: 22% clay; L5: 34% clay). The cores were drained to seven different matric potentials in the range −15 to −1500 hPa and gas diffusion determined prior to a 4‐wk incubation at 20°C in the dark. For all soils the net nitrification increased with water content to a maximum (L1, 12.1 μg NO3–N g−1 soil; L3, 10.3 μg NO3–N g−1 soil; and L5, 8.2 μg NO3–N g−1 soil) and then decreased with further increase in water content. The water content at maximum nitrification was 0.26, 0.37, and 0.42 m3 m−3, respectively. Calculations of water‐filled pore space (WFPS) did not normalize soil type differences in optima for microbial activity. The matric potential at peak net nitrification was −140, −170, and −430 hPa, respectively. No single correlation between CO2 evolution and soil water content existed across soil types. The relative solute diffusivity estimated by recently developed models offered a better description of CO2 evolution. The relative gas diffusivity was a better predictor of the increase in net nitrification than was the soil air content. A conceptual model balancing the effects of solute and gas diffusivity indicated that the relative trend in the observed optima of water contents across soil types was as expected. We advocate the use of the conceptual model including soil type dependent expressions for solute and gas diffusivity in future studies of aerobic microbial activity.
Drainage Network Analysis for Regional Partitions of Alluvial Paddy‐Field Soils
Authors: Ishida T. , Itagaki S. , Sasaki Y. , Ando H.
Published: July 2014

Terrain data on floodplains might be a useful source of ancillary information about soil properties at a regional scale. However, terrain data are not believed to be suitable for obtaining information on paddy‐field soils on floodplains, because the contrast in the topography of floodplains is only slight. This study was conducted in the Tsuruoka area, a part of the Shonai Plain in the northern part of Japan, to evaluate whether a division of floodplain into landform elements can provide useful information on delineation of paddy‐field soils. As source data for the division, a digital elevation model (DEM) was constructed based on a closely spaced differential global positioning system (DGPS) survey and geostatistical interpolation. By using the DEM, drainage network analysis was performed to delineate the landform units. To evaluate correspondence of soil classification with the land division, soil chemical data from 154 soil samples were classified by using a set of numerical procedures. The numerical procedures included principal component analysis and unsupervised classification techniques. In the land partition map created, each landform unit could satisfactorily represent a separate soil group as characterized by soil chemical properties. A statistical analysis revealed that the regional partition map was better than the conventional soil map inasmuch as the partition map described more satisfactorily the spatial distribution of soil chemical properties. However, this conclusion depends largely on the spatial resolution and precision of the DEM. The useful regional partition map could not be produced by different DEM that has lower resolution and accuracy.
Hillslope Soils and Organic Matter Dynamics within a Native American Agroecosystem on the Colorado Plateau
Authors: Norton J. B. , Sandor J. A. , White C. S.
Published: July 2014

Zuni farmers of western New Mexico demonstrate knowledge about soil and hydrological processes that link upland watersheds to alluvium‐derived soils that have crucial cultural, ecological, and hydrological functions. To define how hillslopes contribute to productivity of soils derived from alluvium, we studied soil‐vegetation‐landform parameters in three headwater drainages on the Zuni Indian Reservation. Analyses along eight summit to toeslope transects show that soil properties follow parabolic and linear trends with changes driven by elevation, lithology, and vegetation in the mesa‐canyon pinyon–juniper–Gambel oak (Pinus edulisEngelm.–Juniperusspp.–Quercus gambeliiNutt.) woodlands. Total organic C, N, and P concentrations in surface horizons follow negative parabolic trends and are highest on wooded backslopes and lowest on summits and toeslopes. Inorganic N and available P concentrations and total organic to inorganic N and P ratios increase linearly from summit to toeslope. Taken together, soil, landform, and vegetation data suggest: (i) summit positions are relatively stable with immobilizing microbial environments; (ii) inorganic nutrients increase progressively down steep and erodible backslopes as inputs of forest litter are mixed with surface soil; (iii) influx of mixed sediment and organic materials from backslopes maintains concentrations of inorganic nutrients on footslopes and toeslopes. Entrenchment of drainage ways can circumvent these translocation processes. Without the influx of organic materials, footslopes and toeslopes may become nutrient‐depleted as immobilization becomes the dominant microbial process. The results underscore the importance of functional connectivity between upland hillslopes and alluvial soils.
A Unified Framework For Water Erosion And Deposition Equations
Authors: Yu B.
Published: July 2014

Two modeling frameworks have been developed to describe and predict soil erosion and sediment deposition in recent years. The first is based on the concept of transport capacity. Deposition occurs only when the transport capacity is exceeded. This approach has been implemented in WEPP (Water Erosion Prediction Project) and several other physically based erosion prediction models. An alternative approach is based on simultaneous erosion and deposition. Net erosion or deposition is seen as a result of the dynamic interactions among all processes involved. The simultaneous erosion and deposition approach lays the foundation for GUEST (Griffith University Erosion System Template) and for recent studies of multi‐size sediment deposition. This paper uses the original governing equations for WEPP and GUEST to represent the two approaches to water erosion and deposition modeling. The paper shows analytically that the two sets of governing equations, while vastly different in their appearance, share an identical structure, and thus can be reduced to a common set of equations unifying both approaches. The unified framework involves four terms: (i) sediment concentration at the transport limit, (ii) flow detachment, (iii) sedimentation because of gravity, (iv) a rainfall‐driven sediment source term. The two modeling frameworks show only minor differences in how these four terms are formulated. Analytical solutions to the unified erosion and deposition equations show that the characteristic length for erosion is the ratio of maximum sediment discharge to maximum rate of detachment, and the characteristic length for deposition is the ratio of minimum sediment discharge to minimum rate of deposition, or simply the ratio of unit discharge to fall velocity. The paper clarifies and simplifies the current approaches to erosion and deposition modeling.
Modeling Slope Stability in Honduras
Authors: Zaitchik Benjamin F. , van Es Harold M. , Sullivan Patrick J.
Published: July 2014

Hurricane Mitch (1998) was the deadliest storm to strike the western hemisphere in over 200 yr, and landslides were a significant component of the storm impact, inflicting direct damage on steep lands and triggering mudslides that devastated valleys below. The stability index mapping (SINMAP) model was applied to a 46.1‐km2 agricultural area in Central Honduras to predict the spatial distribution of shallow debris slides based on the infinite slope stability model and a steady‐state hydrology module. The region was surveyed for geology and depth of bedrock, and 63 soil samples were collected on which bulk density, saturated shear strength, angle of soil friction, and saturated hydraulic conductivity were measured. A digital elevation model (DEM) was developed from digitized elevation contours. The natural variability of soil properties was accounted for in a set of model simulations based on parameter distributions, and results were presented in a distributed probability map (DPM) for slope failure that, in turn, was used to identify the spatial scale of variability captured by the model. Ripley's K‐function for distribution of a spatial point process was applied to mapped landslides and to simulated data based on the DPM. Observed landslide locations were more tightly clustered than those predicted by the physically based model, indicating that fine‐scale physical phenomena not captured by the model likely play a role in slope failure. Aggregation of observed landslides on a scale of 150 m made the comparison with model predictions more consistent. Both parameter variability and inventory scale are important considerations in the evaluation of a slope stability model.
Using Rare‐Earth Oxide Tracers for Studying Soil Erosion Dynamics
Authors: Zhang X. C. , Nearing M. A. , Polyakov V. O. , Friedrich J. M.
Published: July 2014

Spatially averaged soil erosion data provide little information on soil erosion dynamics. Dynamically varied, spatially distributed erosion data are needed to better understand erosion processes and thoroughly evaluate process‐based erosion prediction models. The objectives of this study are to examine the feasibility of direct mixing rare‐earth element (REE) oxides with soil materials to trace soil erosion at a plot scale and to explore further the potential of using this technique to study soil erosion dynamics. Five REE oxide powders were mixed with a Camden silt soil (fine, silty, mixed, mesic Typic Hapludalt) at five slope positions. Six rainstorms were applied to a 4 by 4 m soil bed at a 10% slope. Runoff was collected during the rains and surface soil was sampled after each rain. All samples were extracted for REE with a quick acid‐leaching method and extracts were analyzed by inductively coupled plasma mass spectrometry (ICPMS). Mean error of REE‐derived sediment discharge relative to measured total across six rainstorms was 14.5%. Our results demonstrate that the REE‐tracing technique is feasible and sound, being capable of producing both spatially and temporally distributed erosion data. Results indicate that the most severe erosion occurred in the upper middle section of a uniform slope, and total sediment delivery from each segment was positively related to amounts of sediment deposition on the entire slope from that segment. This technique has the potential to bring new perspectives to soil erosion research.