Sandy Loam Field Research Articles

Effects of applying potassium at different growth stages on dry matter accumulation and yield of winter wheat in different soil-texture fields

<p indent=0mm>To investigate the effects of potassium applying on the grain yield formation of winter wheat, the experiments were carried out on different soil textures with high-yield winter wheat variety Taimai 198. To analyze the effects of potassium application at different stages on winter wheat flag leaf photosynthetic characteristics, dry matter accumulation and distribution, and grain yield under different soil texture conditions, two soil texture test fields [sandy loam (S) and silty loam (F)] and three treatments [no potassium fertilizer (K0), potassium fertilizer base application (100% applicating at sowing, K1), and split application (50% applicating at sowing stage + 50% topdressing at the jointing stage, K2)] was arranged. The results showed that the interaction of soil texture and potassium application significantly affected the grain number per spike and dry matter assimilated after anthesis and grain yield. Under the two soil texture conditions, potassium application significantly increased the grain yield of winter wheat, and K2 treatment had the highest yield. Compared with K1 treatment, the grains number per ear, the SPAD and net photosynthetic rate of flag leaves after anthesis, the accumulation of dry matter per stem after anthesis, and the transfer of assimilation to the grain after anthesis were increased under K2 treatment. Under sandy loam conditions, grain yield of K2 treatment was by 12.4% and 10.4% higher than that of K1 treatment, respectively. Under silt loam conditions, grain yield was by 5.2% and 5.4% higher than that of K1 treatment. Those results indicated that wheat yield was significantly increased by changing potassium fertilizer base application to 50% base application with 50% topdressing at jointing stage, and the wheat yield was higher in sandy loam field.

A simulation of variable rate nitrogen application in winter wheat with soil and sensor information - An economic feasibility study

CONTEXTVariable rate nitrogen (N) management strategies are often based on information about soil texture or information from canopy sensors, mounted on ground-based vehicles or satellites. However, disentangling the effect of each information type on N management strategy with experimental studies is often difficult, as results are only valid for the specific experimental conditions as well as the weather conditions for specific years. An alternative to this is to use deterministic crop growth models to generate a wider range of weather x treatment combinations. OBJECTIVEThis study examines if ‘static’ soil profile information or ‘dynamic’ canopy sensor type information provide a better basis for decision making concerning N-application at the subfield level. METHODSThe DAISY model was used to simulate crop growth in a five-year crop rotation on six soil profiles found in a heterogeneous sandy loam field. A range of management descriptions and simulations were made using 5 × 500 years of synthetic weather data with each crop in a five-year rotation set at the first year of the five parallel simulations. Simulated growth variables were used as proxies for a ‘dynamic’ canopy sensor information system. The differential gross margin was then calculated for a range of price relations between fertilizer (model input) and wheat yield (model output), including wheat price adjustments according to protein content. From regressions and backward induction analysis, the N application that maximizes the expected grain revenue minus fertilizer expenditure was estimated for four information cases; Case 1) Uniform application, assuming no prior information, Case 2) application based on soil type information, Case 3) application based on canopy sensor information and Case 4) application based on combined soil and canopy sensor information. RESULTS AND CONCLUSIONSFindings from this study indicated that decisions with soil information alone provide an annual differential gross margin of variable rate application (without considering cost of information and technology) between 3.88 and 13.30 € ha−1 across price and soil variation. This margin approximately doubled with applications based on canopy sensor information and further doubled again with applications based on both soil and canopy sensor information. SIGNIFICANCEThus, knowledge of the soil has the potential to improve interpretation of sensor signals for fertilization planning. The results may guide developers to decide on what type of information should be included in their decision support systems.

Effects of salicylic acid and humic material preharvest treatments on postharvest physiological properties of statice cut flowers

Statice ornamental plants have a great potential for use in urban landscapes, producing cut flowers and flowering pot plants. Based on the previous reports, it was our hypothesis that the use of humic materials (HM) and salicylic acid (SA) can improve the growth and yield, and also the resistance of static plants to many harsh environmental conditions. Therefore, the effect of HM at 4 concentrations of 0 (control), 2, 4 and 6 g.m−2 (which were added as basal at the beginning of planting at the transplanting stage) and the effect of SA at 4 concentrations of 0 (control), 1, 2 and 3 mM (applied as a foliar solution every two weeks until the flowering stage was started) were evaluated on the growth characteristics of Limonium sinuatum (L.) Mill. cv. Qis Mix (Graines Voltz, France) in the research station of Horticultural department, University of Tehran in 2017−2018. Statice seeds first were planted in 45 cells trays, 50 mL volume each, containing equal volumes of peat and perlite, and 30 days’ later seedlings transferred to the pots (4 L of volume) containing sandy loam field soil and kept grown for 4 months in the field condition inside the hole in the soil level prepared for the pots. The results showed that number of cut flowers produced per pot and growth traits was significantly increased under 1 mM treatment of SA and 6 g m−2 treatment of HM compared to control, but physiologically responded in terms of reduced ion leakage, less malone dialdehyde accumulation, less accumulation of hydrogen peroxide, and improved antioxidant enzymes activity with 1 mM of SA and with 4 g m−2 of HM. Findings reveal that a given concentration of SA foliar application could be an alternative improvement treatment instead basal application of HM in case facing harsh environmental conditions during statice cultivation.

Effects of Different Fertilizer Application Methods on Yield and Quality of “Kenroku” Sweet Potato in Sandy Loam Fields

Effects of Different Fertilizer Application Methods on Yield and Quality of “Kenroku” Sweet Potato in Sandy Loam Fields

Phytotoxicity of copper oxide nanoparticles in soil with and without biosolid amendment

Copper-engineered nanomaterials (ENM) are being used in many applications, some of which are expected to release these materials to the wastewater stream, potentially resulting in their build-up in biosolids destined for agricultural fields. Using a sandy loam field soil, we investigated the phytotoxicity of nano-CuO (<50 nm, nominal size) to Trifolium pratense and Elymus lanceolatus in two exposure scenarios (added directly to soil, added via biosolids amendment to soil) compared to similar exposures prepared with the readily soluble Cu form, CuSO4. Copper free ion activity (Cu2+) was measured in KNO3 extracts using a Cu2+ selective electrode at three time points: beginning of plant bioassays, and ends of T. pratense (14 d) and E. lanceolatus (21 d) tests. Extractable Cu2+ was generally lower in the biosolids-amended soils, regardless of Cu form, at the beginning of tests. By the end of the tests (d 14 or 21), Cu2+ activity remained consistent or increased in nCuO exposures, whereas Cu2+ activity of soluble Cu increased overtime in biosolids-amended soils, but decreased in the soil only exposures. Based on median effect levels (EC50's), exposures with nano-CuO were equally, or less, toxic than CuSO4 exposures, regardless of plant species, with root elongation being the most sensitive endpoint. Expressing toxicity in terms of Cu2+ generally resulted in no difference in toxicity between biosolids-amended and non-amended soils. In total, these data contribute to the mounting evidence that the assessment of nano-CuO toxicity in soils fits into current risk assessment models that utilize bioavailable Cu parameters (e.g., Cu2+).

Multi-Year Field Evaluation of Fluorinated Nematicides Against Meloidogyne incognita in Carrots.

California grows approximately 80% of the U.S. carrot production. The primary production challenges derive from root-knot nematodes (Meloidogyne spp.). Between 2013 and 2016, we evaluated three novel fluorinated nonfumigant nematicides in five field trials. Fluensulfone, fluopyram, and fluazaindolizine were applied as product-ready formulations at various rates, dates, and formulations. They were rated for their efficacy against the Southern root-knot nematode (M. incognita), their ability to mitigate nematode-caused crop damage, and potential to produce marketable carrot yield under high disease pressure. All trials were conducted in randomized complete block designs in M. incognita-infested, sandy-loam fields. Soil population of M. incognita at seeding and harvest, midseason plant vigor and fibrous root galling, harvest taproot galling, and marketable carrot yield were analyzed by ANOVA. Midseason gall ratings were indicative of disease ratings at harvest. All fluazaindolizine and fluensulfone treatments reduced at-harvest galling compared with the untreated controls. Fluopyram resulted in less galling but did not sufficiently protect the lower part of the taproot. Overall, fluazaindolizine at 2.24 kg/ha resulted in the most consistent and highest marketable carrot yield, followed by fluensulfone at 2.95 kg/ha. Both fluazaindolizine and fluensulfone will likely provide effective and target-selective crop protection against root-knot nematodes in fresh carrot production.

Soil type-driven variable effects on cover- and rotation-crops, nematodes and soil food web in sugar beet fields reveal a roadmap for developing healthy soils

Improving soil health and managing beneficial and harmful nematodes using cover crops such as oilseed radish and mustard integrated with maize and soybean as rotation crops are major priorities in US sugar beet production. Despite extensive research on effects of rotation- and cover-crops on soil health, variable outcomes remain a problem. Using sandy clay loam and loam fields with known SBCN infestation, we tested how two each of oilseed (‘Defender’ and ‘Tillage’), mustard (‘Pacific Gold’ and ‘Ida Gold’), sugar beet (‘B-18RR4N’ and ‘B-10RR34’) and soybean (‘92Y80’ and ‘92M91’), and a maize (‘P9910R’) variety affect nematode community and soil food web in the 2013 and 2014 growing seasons. Each treatment (crop) was replicated six times. Maize is a non-host and Defender and Pacific Gold are poor hosts for SBCN. Nematode community composition at intervals during growing seasons and soil physiochemical properties at the end of year 1 were measured. The crops had no effect on nematodes. Nematode abundance and community indices varied by sampling time, growing season and/or soil type. Principal component analysis showed that the crops distinctly separated by soil type and only a few nematode community indices and/or soil physiochemical parameters overlapped with crop. Soil food web analysis showed depleted and degraded conditions in the sandy loam soil and disturbed and approaching enrichment in the loam soil. The study suggests a roadmap to get to agrobiologically suitable soil conditions to meet industry priorities for healthy soils.

Can conservation tillage reduce N2O emissions on cropland transitioning to organic vegetable production?

Nitrous oxide (N2O) is an important greenhouse gas and a catalyst of stratospheric ozone decay. Agricultural soils are the source of 75% of anthropogenic N2O emissions globally. Recently, significant attention has been directed at examining effects of conservation tillage on carbon sequestration in agricultural systems. However, limited knowledge is available regarding how these practices impact N2O emissions, especially for organic vegetable production systems. In this context, a three-year study was conducted in a well-drained sandy loam field transitioning to organic vegetable production in the Mid-Atlantic coastal plain of USA to investigate impacts of conservation tillage [strip till (ST) and no-till (NT)] and conventional tillage (CT) [with black plastic mulch (CT-BP) and bare-ground (CT-BG)] on N2O emissions. Each year, a winter cover crop mixture (forage radish: Raphanus sativus var. longipinnatus, crimson clover: Trifolium incarnatum L., and rye: Secale cereale L.) was grown and flail-mowed in the spring. Nearly 80% of annual N2O-nitrogen (N) emissions occurred during the vegetable growing season for all treatments. Annual N2O-N emissions were greater in CT-BP than in ST and NT, and greater in CT-BG than in NT, but not different between CT-BG and CT-BP, ST and NT, or CT-BG and ST. Conventional tillage promoted N mineralization and plastic mulch increased soil temperature, which contributed to greater N2O-N fluxes. Though water filled porosity in NT was higher and correlated well with N2O-N fluxes, annual N2O-N emissions were lowest in NT suggesting a lack of substrates for nitrification and denitrification processes. Crop yield was lowest in NT in Year 1 and CT-BP in Year 3 but yield-scaled N2O-N emissions were consistently greatest in CT-BP and lowest in NT each year. Our results suggest that for coarse-textured soils in the coastal plain with winter cover crops, conservation tillage practices may reduce N2O emissions in organic vegetable production systems.

Improving Effects of Mild Cold Stress and Salicylic acid on Growth and Physiology of Periwinkle (Catharanthus roseus Don.)

To study effects of salicylic acid (SA) treatments (0, 0.5, 1 and 2 mM) in two forms of seed priming (for 24 h) and spraying on seedling at 4-6 leaf stage an experiment was conducted on periwinkle (Catharanthus roseus Don.) with and without exposure to a mild cold stress of 8 °C (for 32 h). Seeds were sown in trays containing peat-based substrate (with 20% sandy loam field soil). Transplants of both groups were treated with mild cold. Seedlings were grown in greenhouse with an average day/night temperature of 25/20± 2°C until their blooming. Seed emergence rate and percentage, activities of catalase (CAT), guaiacol peroxidase (GPX), polyphenol oxidase (PPO), CAT gene expression, height and number of nodes per plant, and days to flowering were evaluated. Results showed that mild cold stress together with salicylic acid at 0.5 mM (as either seed priming or spray on seedling) was the best treatment to accelerate the flowering, and improve growth parameters and antioxidant enzymatic activities. Thus, mild cold stress enhanced the positive effects of SA treatments on cold acclimation of periwinkle (particularly when associated with spraying, which is a simple administration method). Accordingly, it might be recommended for its seedling production and cultivation in temperate climates to prevent late spring frost damages.

Roots of Cleistogenes songorica Improved Soil Aggregate Cohesion and Enhance Soil Water Erosion Resistance in Rainfall Simulation Experiments

Native grasses that have acceptable forage yield and quality can play an important role in the sustainable development and protection of soil ecosystem. In this study, we investigate a native grass of northern China, Cleistogenes songorica, showing promise for erosion control. We used a rainfall simulation method to compare the effects of C. songorica roots and tall fescue roots (Festuca arundinacea) on soil erosion in sandy loam field plots with irrigation during establishment in 2011 and under mild or severe drought treatments in 2012 and 2013. Root length (RL), root diameter (RD), soil bulk density (SBD), soil field capacity (FC), sediment yield (SY), and root biomass (RB) of each soil monolith were sampled in the topsoil layer (0–10 cm) with a rectangular geotome. The proportion of stable aggregates in soil and the soil anti-scouring properties were also evaluated. C. songorica had higher RD than tall fescue throughout the experiment and evolved higher RL and RB by 2013. Both C. songorica and tall fescue enhanced the erosion resistance of soil, but C. songorica stabilized soil more effectively than did tall fescue. The proportion of stable soil aggregates was greater in C. songorica plots than in tall fescue grassland under mild drought. The present study shows that C. songorica has great potential to be one of the biological resources for soil erosion resistance, water and soil conservation in arid and semi-arid areas.

NPS Pollution Reduction from Alpine Fields using Surface Cover Material and Soil Amendments

AbstractWe described the effects of straw mat cover and soil amendments on runoff, agricultural non‐point source nNPS) pollution and crop yield on sloping alpine fields in Korea. Two sandy loam field plots were prepared. One was a control plot and the other (SPG) was an experimental plot treated with rice straw, polyacrylamide (PAM) and gypsum (rice straw mat (3,300 kg/ha) + PAM (5 kg/ha) + gypsum (1 ton/ha)). Chinese cabbage was cultivated in the plots and seven rainfall‐runoff events were monitored during the growing season in 2012. Less runoff and a lower NPS pollution load were measured from the SPG plot, compared to those from the control plot. The SPG plot had 29.4% less runoff and the pollution load was reduced by 86.6% for suspended solids, 34.7% for total nitrogen and 39.1% for total phosphorus. The Chinese cabbage yield at the SPG plot was 39,600 kg/ha, which was about 40% higher than that at the control plot. These results indicated that the SPG treatment could not only reduce runoff and agricultural NPS pollution but also increase crop yield and be a best management practice for sandy loam sloping fields in Korea. © 2016 The Authors. Irrigation and Drainage Published by John wiley &amp; Sons Ltd.

Predictivity Strength of the Spatial Variability of Phenanthrene Sorption Across Two Sandy Loam Fields

Sorption is commonly agreed to be the major process underlying the transport and fate of polycyclic aromatic hydrocarbons (PAHs) in soils. However, there is still a scarcity of studies focusing on spatial variability at the field scale in particular. In order to investigate the variation in the field of phenanthrene sorption, bulk topsoil samples were taken in a 15 × 15-m grid from the plough layer in two sandy loam fields with different texture and organic carbon (OC) contents (140 samples in total). Batch experiments were performed using the adsorption method. Values for the partition coefficient K d (L kg−1) and the organic carbon partition coefficient K OC (L kg−1) agreed with the most frequently used models for PAH partitioning, as OC revealed a higher affinity for sorption. More complex models using different OC compartments, such as non-complexed organic carbon (NCOC) and complexed organic carbon (COC) separately, performed better than single K OC models, particularly for a subset including samples with Dexter n < 10 and OC <0.04 kg kg−1. The selected threshold revealed that K OC-based models proved to be applicable for more organic fields, while two-component models proved to be more accurate for the prediction of K d and retardation factor (R) for less organic soils. Moreover, OC did not fully reflect the changes in phenanthrene retardation in the field with lower OC content (Faardrup). Bulk density and available water content influenced the phenanthrene transport mechanism phenomenon.

Pore Structure Characteristics After 2 Years of Biochar Application to a Sandy Loam Field

Pore Structure Characteristics After 2 Years of Biochar Application to a Sandy Loam Field

Effects of agronomic practices on the timeline of Heterodera glycines establishment in a new location

How soybean cyst nematode (SCN,Heterodera glycines) adapts when introduced into a new location under tillage, rotation and crop treatments is unknown. SCN race 3 (Hg Type 0) was introduced into a sandy loam field at more than 4000 eggs (100 cm3soil)−1and observed over 6 years under till and no-till, and either maize (Zea mays; C), SCN race 3 resistant soybean (Glycine max; R) or susceptible soybean (S) monocrop, or RCRC and SCSC rotations. While SCN population density was lower in no-till than in tilled treatments, and highest in S and lowest in C or RC rotations, it was detected at less than 1 cyst (100 cm3soil)−1. This suggests a prolonged phase of decline from the introduced levels. The interaction effects of tillage, rotation and/or time on SCN suggest that outcomes vary by agronomic practice and time, providing agro-biologically-based understanding of SCN establishment in a new location.

CLONAL PROPAGATION OF OAK HYBRIDS USING A MODIFIED LAYERING TECHNIQUE©

Oak (Quercus) hybrids were created using over 40 diverse parent species. The developed hybrids were used as stock plants and asexually propagated annually over four years. This was done to measure the effectiveness of a modified stool bed layering technique on diverse members of the oak genus, and this study is part of a long-term project to select superior urban-tolerant oak hybrids for introduction as named cultivars into the nursery industry. The number of shoots produced by a stock plant each year and the probability for those shoots to root were found to vary between different maternal parent species. Results suggest the shoots of the hybrids that are the progeny of rhizomatous shrub Quercus spp. are more likely to develop roots when propagated using the described technique. This article also identifies and describes in detail a reliable technique to clone oaks. INTRODUCTION Oaks (Quercus spp.) are noted for their sexual infidelity, and natural hybrids commonly occur wherever two interfertile species from the same subgenera grow near each other (Sternberg, 2000). This tendency to hybridize is a useful trait that may be utilized by plant breeders to create hybrids with desirable characteristics such as attractive fall color, tolerance to site conditions, and hybrid vigor. Increasingly, a number of purported hybrid oak selections are becoming available in the nursery industry (JFSchmidt) (Dirr, 2010). Until recent years, relatively few selections of oaks have been made due to the difficulty involved in asexually propagating members of this genus by conventional methods. Oaks are notoriously difficult to bud or graft successfully, which compounds the problem of producing superior selections. Recently, a modified layering technique that incorporates juvenile shoots, etiolation, and treatment with indolebutyric acid (IBA) has shown promise in the asexual propagation of Quercus species (Amissah & Bassuk, 2009) (Hawver & Bassuk, 2000). A study examining the usefulness of this propagation method on numerous hybrid oaks was conducted at the research farms of Cornell University, in Ithaca, New York. The hybrids used represent crosses of over 40 diverse parent species, most of which are in the white oak group (subgenus Quercus). A previous study has shown that the rooting success of oaks propagated asexually using a similar method can differ between species (Amissah & Bassuk, 2007), and preliminary research suggests that the propagation success of individual hybrid oaks would vary depending on the parental species involved in each cross (Gao, 2011). The objective of this research was to measure the effectiveness of the modified stool bed layering technique on diverse members of the genus Quercus, as well as to provide insight into which, if any, parent species consistently yielded hybrid progeny that could be successfully propagated. Additionally, this article identifies and describes in detail a reliable technique to clone oaks. This experiment is part of a long-term project underway at Cornell’s Urban Horticulture Institute to select superior urban-tolerant oak hybrids for introduction as named cultivars into the nursery industry. Along with developing a reliable method to clone oaks, the project currently involves screening the developed hybrids for tolerance to alkaline soils (a common issue in urban landscapes) and making long-term observations on growth and landscape performance. MATERIALS AND METHODS Trees used in this study were hybrids grown from seed that were developed by Peter Podaras at Cornell University in Ithaca, New York (Podaras & Wells, 2008). During the years 2004, 2005, and 2006, controlled crosses were made by pollinating seven species of oak trees growing on the Cornell University campus with pollen from 36 species that are native throughout North America, Europe, and Asia. Table 1 details the number of hybrid seedlings developed from each cross. These seedlings were grown in containers for several years, and during the spring of 2008, 345 unique oak genotypes were planted out in a field of Arkport sandy loam with a pH of 6.2 for future use as stock plants. Starting in spring of 2009, and repeated yearly through 2012, these field-grown stock plants were propagated each year using a modified version of the oak propagation protocol developed by Amissah and Bassuk (2009). Table 1. Hybrid crosses performed and the resulting number of acorn-grown genotypes. Maternal Parent Paternal Parent Number of Genotypes Q. bicolor OPEN POLLINATED 7 Q. sp. (unidentified species) 9 Q. ×bebbiana 5 Q. muehlenbergii × Q. robur 6 Q. affinis 3 Q. aliena 27 Q. austrina 4 Q. chapmanii 4 Q. dentata 7 Q. fabri 14 Q. fruticosa 4 Q. fusiformis 2 Q. gambelii 5 Q. geminata 2 Q. glauca 1 Q. graciliformis 11 Q. libani 3 Q. lyrata 2 Q. macranthera 1 Q. minima 5 Q. mongolica var. grosserata 3 Q. muehlenbergii 22 Q. myrsinifolia 19 Q. phillyreoides 7 Q. polymorpha 4 Q. robur 14 Q. rugosa 13 Q. spinosa 2 Q. turbinella 6 Q. vaseyana 6

Spatial Distribution of Grain Size Characteristics and its Role in Interpreting the Sedimentary Depositional Environment, Kodaikanal Lake, Tamil Nadu, India

The surface sediments of Kodaikanal Lake is situated in the palani hills at an altitude of 2,285 m above sea level, the geo co-ordinates of the lake are lies between 10°14’ N latitude and 77°28’ E longitudes. In the present study determination of grain size and its deposition environment were carried out for surface sediments collected from different parts of the Lake. The study permits to infer the changes in the depositional environment during the period of infilling at the sites. The spatial distribution of Mean size of the sediments varies from medium sand to medium silt, moderately well sorted to very poorly sorted characteristics, near- symmetrical to very fine-skewed type, and falling in platykurtic to very leptokutic nature. United State Department of Agriculture (USDA) textural triangle plot expresses sediments are clustered tightly in silty sand variable, and its type ranges falls within the field of Loamy sand, sand, sandy loam and silty loam fractions. Thus, the Lake sediments are dominance of silt and sand fractions. Multivariant statistics (discriminant analysis) express that the plots fall scattered in Turbidite and Aeolian environment. The Bivariate textural plot falls in Quiet water environment. The polymodel nature of the sediments also implies that transportation by rolling, sliding, saltation and suspension processes in the Kodaikanal Lake.

Characteristics of TN and TP in Runoff from Reclaimed Paddy Field of Fine Sandy Loam

This study investigated the runoff from rice paddy located on reclaimed fine sandy loam soil to provide data for the development of policies to protect water quality of estuaries. Total N (TN), Total P (TP) concentrations and runoff loads at outlet were monitored from 2006 to 2008. Soil phosphate adsorptivity was measured and compared with typical paddy soil in watersheds. TP concentration of the paddy water and TP runoff loads were much greater than those of typical paddy field in watershed because phosphate adsoptivity in reclaimed paddy field of fine sandy loam appeared to be a third of those of typical paddy soils by relatively low soil OM and high sand content of the reclaimed soil. Thus, nutrient runoff, particularly phosphate from the reclaimed paddy field needs to be managed more thoroughly to protect estuarine water quality.

Proximal Gamma-Ray Spectroscopy to Predict Soil Properties Using Windows and Full-Spectrum Analysis Methods

Fine-scale spatial information on soil properties is needed to successfully implement precision agriculture. Proximal gamma-ray spectroscopy has recently emerged as a promising tool to collect fine-scale soil information. The objective of this study was to evaluate a proximal gamma-ray spectrometer to predict several soil properties using energy-windows and full-spectrum analysis methods in two differently managed sandy loam fields: conventional and organic. In the conventional field, both methods predicted clay, pH and total nitrogen with a good accuracy (R2 ≥ 0.56) in the top 0–15 cm soil depth, whereas in the organic field, only clay content was predicted with such accuracy. The highest prediction accuracy was found for total nitrogen (R2 = 0.75) in the conventional field in the energy-windows method. Predictions were better in the top 0–15 cm soil depths than in the 15–30 cm soil depths for individual and combined fields. This implies that gamma-ray spectroscopy can generally benefit soil characterisation for annual crops where the condition of the seedbed is important. Small differences in soil structure (conventional vs. organic) cannot be determined. As for the methodology, we conclude that the energy-windows method can establish relations between radionuclide data and soil properties as accurate as the full-spectrum analysis method.

Investigation of Interactive Effects on Water Flow and Solute Transport in Sandy Loam Soil Using Time Domain Reflectometry

Surface-applied chemicals move through the unsaturated zone with complex flow and transport processes due to soil heterogeneity and reach the saturated zone, resulting in groundwater contamination. Such complex processes need to be studied by advanced measurement and modeling techniques to protect soil and water resources from contamination. In this study, the interactive effects of factors like soil structure, initial soil water content (SWC), and application rate on preferential flow and transport were studied in a sandy loam field soil using measurement (by time domain reflectometry (TDR)) and modeling (by MACRO and VS2DTI) techniques. In addition, statistical analyses were performed to compare the means of the measured and modeled SWC and EC, and solute transport parameters (pore water velocity and dispersion coefficient) in 12 treatments. Research results showed that even though the effects of soil structural conditions on water and solute transport were not so clear, the applied solution moved lower depths in the profiles of wet versus dry initial SWC and high application rate versus low application rates. The effects of soil structure and initial SWC on water and solute movement could be differentiated under the interactive conditions, but the effects of the application rates were difficult to differentiate under different soil structural and initial SWC conditions. Modeling results showed that MACRO had somewhat better performance than VS2DTI in the estimation of SWC and EC with space and time, but overall both models had relatively low performances. The means of SWC, EC, and solute transport parameters of the 12 treatments were divided into some groups based on the statistical analyses, indicating different flow and transport characteristics or a certain degree nonuniform or preferential flow and transport in the soil. Conducting field experiments with more interactive factors and applying the models with different approaches may allow better understanding of flow and transport processes in addition to the simulations of them in the unsaturated zone.

Soil microbial and physical properties and their relations along a steep copper gradient

Copper (Cu) is accumulating in agricultural soils because it is an essential component of mineral fertilizers and pesticides. This could lead to toxic effects on soil macro- and micro-organisms and impact soil structure development. We investigated the effect of historical Cu contamination (>80years; from background concentrations up to 3837mg Cukg−1) on soil microbial enzyme activity, physical properties and resilience to compression. Soil samples and cores were taken from a fallow sandy loam field in Denmark. Microbial activity was quantified using fluorescein diacetate (FDA) and dehydrogenase (DHA) assays. Water dispersible clay was measured on field moist and air dried samples. For the resilience assay, soil cores (drained to −100hPa) were subjected to uniaxial confined compression (200kPa) followed by wet–dry or freeze–thaw cycles. Microbial enzyme activity significantly decreased with Cu concentration ≳500mgkg−1 with the two microbial assays linearly correlated with each other as well as with the water dispersible clay. An effect concentration causing a 50% reduction (EC50) in enzyme activity was observed at 521mgkg−1 for FDA and 542mgkg−1 for DHA. Significant increases in water dispersible clay, bulk density and decreases in air-filled porosity and air permeability were observed from Cu≳900mgkg−1. The increased density of the contaminated soils led to greater compression resistance and resilience relative to the uncontaminated soil. The results suggest that a threshold level for Cu exists (∼500mgkg−1 for this soil type) beyond which microbial activity decreases and soil structure becomes more compact with reduced permeability to air.