Soil Science

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Research from the Department of Soil Science. The department is part of the School of Natural Resources, and their website may be found at https://www.ndsu.edu/snrs/

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Advancing Soil Health: Linking Belowground Microbial Processes to Aboveground Land Management
(North Dakota State University, 2016) Dose, Heather Lynn
Advancing soil health lies at the intersection of belowground microbial processes and aboveground land management. However, linking microbial processes to land use is difficult. Understanding the response of soil microbes to management factors will provide agricultural producers and land managers with information regarding best management practices that not only improve soil health, but also maximize profitability. This study advances the understanding of microbial responses to land management by measuring microbial response to a) amendment application and tile drainage to remediate sodic soils, b) cover crop growth and tile drainage to ameliorate saline soils and c) tillage and fertilizer management factors on Bradyrhizobium japonicum, a symbiotic bacteria needed for biological N fixation in soybeans (Glycine max L.). Multiple time point measurements of soil microbial enzymes and functional gene copy numbers from three field experiments were used to determine microbial responses to land management. Key findings indicate that gypsum amendment applications, although effective at reducing sodicity, reduce soil enzyme activity levels in the short-term while tile drainage has no effect on microbial response to sodic soils. This work also demonstrates that the quantity of nitrifiers and denitrifiers can be used as either short–term or long–term indicators of soil health which reflect overall ecosystem health in sodic soils. In contrast to sodic soils, nitrifiers and denitrifiers are not useful indicators of soil health in saline soils as these microbial communities exhibit salinity induced community tolerance. Finally, tillage system and N availability have the greatest effect on B. japonicum numbers and activity in the soil. The lower amount of N obtained from biological N fixation in soybeans grown under no till systems reflects the reduced reliance on B. japonicum for plant N needs. Inoculated populations of B. japonicum are important for early season biological N fixation, but persistent and diverse populations of B. japonicum play an important role in late season N fixation in the lateral soybean root nodules. Overall, this work demonstrates that monitoring soil microbial activity can be useful for producers and land managers looking to improve soil health.
Association and Bioavailability of 17β-Estradiol with Soil and Manure Aqueous Dissolved and Colloidal Fractions
(North Dakota State University, 2014) Chambers, Katrin Bella
Steroidal estrogens in the environment exert toxicological effects at very low concentrations. Furthermore, dissolved and colloidal fractions of soil and manure play an important role in the environmental fate and transport of steroidal estrogens. One objective of this study was to quantify the association of the natural estrogen, 17β-estradiol (E2), with the dissolved fraction and colloidal fraction isolated from liquid swine manure (LSM), soil, and soil+LSM mixtures. The second objective of this study was to evaluate whether the E2 associated with the dissolved fraction/colloidal fraction, dissolved fraction and colloidal fraction of the various media could induce an estrogenic response. Estrogenicity was assessed using an E2 receptor (ER) competitor assay, which provided E2 equivalent concentration (EEQ) of dissolved fraction/colloidal fraction, dissolved fraction and colloidal fraction solutions created from the Soil, Soil+LSM and LSM.
The Biogeochemistry of Soil at Depth Within the Wetland Landscape of the Prairie Pothole Region
(North Dakota State University, 2021) Werkmeister, Carrie Elaine
The impact of agricultural practices on wetland ecosystems in the Prairie Pothole Region (PPR) has long been recognized but little is understood about impacts on the biogeochemistry of the wetlands at depth. Understanding the relationship of multi-elements within the wetland and surrounding landscape can aid in wetland restoration and provide guidance for wetland management. The objectives of this study were to: 1) identify biogeochemical characteristics of PPR wetlands; 2) identifying differences or similarities in biogeochemical characteristics of the landscape; 3) assess the vertical variation in chemical composition at depth in wetland, wetland and fringe, footslope and backslope soils; and 4) interpret the soil chemistry of undisturbed sites (good quality; prairie vegetation) and disturbed sites (poor quality; cultivated) relative to differences in landscape position locations. A field study was conducted on six disturbed (DW) and 6 undisturbed (UW) wetlands with evaluation of fringe (F), footslope (FS), or backslope (BS) positions. Using redundancy analysis (RDA) with selected environmental variables models of element concentrations at depth in each position were generated. The RDA ordination plots of element concentrations to depth of 1m was constrained by variables sand, silt, clay, depth, bulk density, site, organic matter, electrical conductivity, and pH. Pearson correlation coefficients between soil properties and the five most prominent soil elements differed between landscape positions. Anthropogenic activity likely influenced the subsurface hydrology but differed in physical and chemical properties. These differences appear to be related to the vegetation, levels of soil disturbance of surrounding landscapes and unique chemical and physical characteristics of parent material.
Biological Response to Sulfate Salinity in Richland County, North Dakota
(North Dakota State University, 2016) Butcher, Kirsten R.
Soil salinization is a major threat to agricultural ecosystems. Consequently, an understanding of agro-ecosystem functions affected by increasing levels of soil salinity is critical for land management. The purpose of this research was to determine the effects of soil salinity on corn and soybean growth and soil microbial activity in southeastern North Dakota soils with naturally occurring soil salinity. A field study assessed corn and soybean yield, and a laboratory study assessed microbial respiration in response to increasing salinization. Both corn and soybean yield were significantly impacted by salinity in sandy loam soils, declining after a threshold of 4.57 dS m-1 and 2.98 dS m-1, respectively. These thresholds are higher and lower than previously established threshold tolerances for corn and soybean, respectively. Microbial respiration in sandy loam soils could not be significantly explained by ECe, potentially indicating a community composition that has acclimated to sulfate-based salinity in these soils.
Brine-Contaminated Soils in Western North Dakota: Site Assessment Methodology and a New In-Situ Remediation Method
(North Dakota State University, 2016) Klaustermeier, Aaron Wallace
Anthropogenic soil salinity caused by produced water (i.e., brine) contamination is an issue in all oil and gas producing regions. The objectives of this research are to develop soil electrical conductivity (EC) conversion equations for rapid site assessment of brine spills and to determine the efficacy of crystallization inhibitors as an in-situ remediation method. Conversion equations were developed for soil-to-water suspensions and saturated paste extracts (ECe) on brine-contaminated soils. These new equations provided the best prediction of ECe when compared to 14 other equations reported in the literature. A crystallization inhibitor (C18Fe7N18) applied to NaCl-contaminated soils using various concentrations and methods of application yielded dendritic salt crystals above the soil surface. On average, between 0.29 and 0.57 g g-1 of NaCl salts effloresced when surface applying a 0.01M concentration of the crystallization inhibitor. Results from these studies will guide consultants and researchers in the assessment and remediation of brine-contaminated soils.
Calcium Acetate: An Alternative to Gypsum for Brine Impacted Soils
(North Dakota State University, 2022) Peterson, Annalie
With North Dakota being ranked as a leading producer of oil and natural gas in the United States, the possibility of accidental produced water (aka “brine” or “salt water”) spills is a continuous concern. Brine water poses numerous threats to soil properties as it has the potential of causing soil dispersion by increased concentrations of sodium. The goal of this research was to compare the effectiveness of several calcium amendments: calcium acetate, flue gas desulphurization gypsum and pelletized gypsum, on improving the saturated hydraulic conductivity (Ks) and removing sodium of three brine impacted soils. Ultimately, increasing rates of calcium acetate had the greatest effect on increasing the Ks but, in general, increasing rates of any amendment increased the Ks and removed sodium. A secondary goal was to produce a resource about the origin of brine water in the Williston basin for those affected by or interested in this topic.
Can Soil Microbial Activity Be Improved With the Use of Amendments?
(North Dakota State University, 2020) Kruger, Matthew Wayne
Low microbial activity and associated nutrient cycling are concerns in agricultural problem soils. The objectives of this study were to investigate microbial response on problem soils to amendments, drying-wetting cycles, and the interaction of amendments and drying-wetting cycles. In this laboratory study, soil carbon dioxide (CO2) flux was measured from thermal desorption treated soils and saline soils in response to Proganics, spent lime, and composted beef manure applications. Microbial activity was measured through CO2 flux and its rate of change, permanganate oxidizable C, and residual inorganic nitrogen. Proganics had the greatest ability to elevate and sustain microbial activity on problem soils, but spent lime and compost had the greatest potential to improve microbial mediated nitrogen mineralization. In conclusion, spent lime and compost can be effective amendments for improving soil quality of saline and thermal desorption treated problem soils to increase microbial activity and associated nitrogen cycling.
Can We Increase Crop Yield Adopting Tile Drainage in Fargo Clay Soil?
(North Dakota State University, 2018) Acharya, Umesh
Subsurface drainage has recently become common for agriculturally productive soils and key to maintain and improve crop production in poorly drained, frigid clay soils. The first study was conducted for four years (2014-17) at Casselton, ND to determine best combination of drainage, tillage and crop rotation for higher corn yield. Our finding suggested corn yield was highest with no drainage, CS and CH combination in years with drought conditions. The second study was conducted for three years (2015-17) to evaluate subsurface drainage spacing (9, 12, and 15m) and depth (0.9 and 1.2m) combination on corn, soybean and sugarbeet yields and residual soil nitrate-nitrogen (NO3-N) contents. Results indicated that 9 m drain spacing produced highest corn and soybean yield when average across three years in contrast with drain depth that has no effect on corn and soybean yield except for sugarbeet where the 1.2m depth yielded higher than the 0.9m depth.
Characterizing Soil Microbial Communities of Reclaimed Roads in North Dakota
(North Dakota State University, 2012) Viall, Eric
Reclaimed roads on the Little Missouri National Grasslands of southwestern North Dakota have not returned to pre-disturbance conditions. Phospholipid fatty acid analysis was performed on soil samples collected from reclaimed roads and adjacent prairie to assess reclamation effects on the microbial community. Additionally, nutrient cycling capacity was measured by four enzyme assays. Ordination analysis of PLFA data identified a distance gradient indicating microbial communities of reclaimed roads were different from the prairie. Specifically, Gram-negative bacteria and arbuscular mycorrhizal fungi are associated with roads; soil organic matter was associated with prairie sites. Soil enzyme activities associated with prairie sites indicate greater nutrient cycling. The soils of reclaimed roads have not accumulated sufficient organic matter to sustain both plant and microbial communities characteristic of the surrounding prairie.
Chemical and Biological Characteristics of Thermally and Chemically Disturbed Soil in Northwestern North Dakota
(North Dakota State University, 2017) Ritter, Samantha Susan
Thermal desorption (TD) remediates hydrocarbon-contaminated soil by heating the soil (200 to 500 °C) to volatilize the hydrocarbons, effectively removing the contaminant from the soil. If the soil is then used for agricultural production, reclamation success can be determined by quantifying aspects of soil health. Cation exchange capacity (CEC), cation selectivity and Gibbs free energy (ΔGex) of TD-treated and untreated soil were compared. Although CEC and ΔGex differed, cation selectivities were not altered suggesting that alternative fertility management to retain previous soil productivity may not be needed. From field plots, N-transforming genes were lowered in contaminated and TD-treated soils as compared to non-contaminated soil, but the addition of surface soil (1:1 blends) increased N-cycling genes to levels reported in the literature. Thermal desorption may not alter soil chemical as much as biological metrics, but blending treated or contaminated soils with native surface soils can enhance soil function and, ultimately, productivity.
Corn Response to Sulfur Fertilizer in the Red River Valley
(North Dakota State University, 2018) Kaur, Jashandeep
A study was conducted at ten locations in North Dakota and Minnesota in 2016 and 2017 to evaluate corn response to different sulfur (S) application rates and to determine the relationship between corn yield and plant tests. Five S treatments of 0 (check), 11, 22, 33, and 44 kg S ha-1 were applied as ammonium sulfate granular fertilizer. Significant increase in corn yield occurred at only two sites (out of ten sites) in both years. Application of 33 kg S ha-1 (2016) and 44 kg S ha-1 (2017) increased corn yield by 3.4 Mg ha-1 and 1.3 Mg ha-1, respectively. Poor correlation was noticed between plant tests (tissue S and N/S) and corn yield. These results indicate that response to S varies from soil to soil and weather conditions may play the most important role in determining the response. Additional research should be conducted using different soils over multiple years.
Corn Response to Sulfur in the Red River Valley
(North Dakota State University, 2022) Goyal, Diksha
Sulfur (S) deficiency symptoms are becoming common to crops grown in the Red River Valley of North Dakota and Minnesota. Corn (Zea mays L.) response to incremental sulfate-S (0, 11, 22, 33, and 44 kg S ha-1) was studied (n=12) during the 2018-2020 growing seasons in a series of experiments. Corn yield and S uptake did not respond to S fertilizer (P≥0.05) additions, but yield varied across sites. Ten out of 12 sites showed an increase in grain yield over control but not significant. Corn, spring wheat (Triticum aestivum L.), and sugar beet (Beta vulgaris L.) responses to S forms were also studied. Only spring wheat showed a significant (P≤0.05) response to S forms. Growers should follow the current recommendation to apply 11 kg S ha-1 to compensate for the grain S removal and avoid grain yield loss to S in susceptible areas of fields.
The Effect of Salinity on Soil Microbial Community Structure
(North Dakota State University, 2020) Ries, Mackenzie Lynn
Soil salinity is a widespread problem that affects crop productivity. We expect that saline soils also have altered microbial community structure, soil food webs and related soil properties. To test this, we sampled field soils across four farms in eastern North Dakota that host salinity gradients. We evaluated microbial biomass carbon, phospholipid fatty acid analysis and nematode counts in moderately saline and low saline soils. Additionally, we measured soil properties that represent potential food sources and habitat characteristics that influence microbial communities. We found higher microbial group abundance in moderately saline soils than in the lower saline soils. In contrast, we found lower nematode abundances in the moderately saline soils. We also observed increased labile carbon, nitrogen, phosphorus, and water content in the moderately saline soils. Based on our results, saline soils appear to have unique soil biological characteristics, which have implications for overall soil function along salinity gradients.
Effects of Major Flooding on Water and Sediment Characteristics in an Urban Enviromnent
(North Dakota State University, 2011) Guy, Adam Christopher
Spring flooding of the Red River of the North is a common phenomenon, but no infonnation exits on how these flooding events impact both water and sediment quality within an urban area. The objectives of this study were to assess if urban enviromnents affect floodwater quality and to determine the quality of sediment deposited in an urban environment after floodwaters recede. Water samples were taken on 12 dates from two locations before and after the city limits of Pargo, North Dakota and Moorhead, Minnesota (F-M), and were measured for 12 variables including total sediment, P04, 17/3-estradiol, and diesel range organics. Sediment and underlying soil samples were collected from three locations within F-M where, at each location, there were three equidistant transects parallel to the river channel, and analyzed for 40 variables including dry sediment mass, carbon, nitrogen, diesel and gasoline range organics, and trace elements. Considering river discharge and total sediment and P04 concentrations at each sampling date, about 4500 Mg of sediment and 30 Mg of P04 were estimated to have been deposited within F-M. l 7Bestradiol was detected in 9 of 24 water samples with an average concentration of0.61 ng L1 and diesel range organics were detected in 8 of 24 samples with an average concentration of 80.0 µg L-1. Average mass of sediment across locations and transects ranged from about 2 to 1 O kg m·2 where transects closest to the river channel had the higher mass deposits of sediment. Total carbon and nitrogen within the sediment was determined to be mostly organic and ranged from about 40 to 59 g kg' 1 and about 1,760 to 4,930 mg kg·1, respectively, with the highest concentrations occurring at the transect furthest from the river channel. No gasoline range organics were detected, but diesel range organics were detected in 26 of the 27 sediment samples analyzed with a maximum concentration of 49.2 µg g-1• Total Hg concentrations in the sediment and soil averaged about 55 and 61 ng g-1, respectively, and all trace elements detected in the sediments were within ranges for noncontaminated sites. Although sediments remaining after floodwaters recede can be unsightly and cleanup efforts can be labor intensive, these sediments can also provide essential plant nutrients for urban riverine ecosystems, which may include turf grass, fruits and vegetables, and horticultural plants.
Effects of Swine Slurry on Sorption of 17~-estradiol to Soil
(North Dakota State University, 2011) Zitnick-Anderson, Kimberly Korthauer
178-estradiol (E2) is a potent endocrine disrupting compound that is found in swine manure. Liquid swine manure or otherwise knov.n as swine slurry is commonly used as a form of fertilizer in agricultural practices. Laboratory studies have demonstrated that E2 binds readily and strongly to soil and degrades within hours. However, field studies detect E2 in the environment at frequencies that suggest its moderate mobility and persistence. The objective of this study was to determine if colloidal organic carbon (COC; < I kDa) and dissolved organic carbon (DOC;> I kDa to< 0.45μm) from swine slurry affect the sorption and persistence of E2 in soil. Batch experiments were used to determine the sorption of 14C labeled E2 in soil with slurry solution compared to the sorption of E2 in soil with only a 0.0IM CaCh solution. Samples were quantified for total radioactivity using liquid scintillation counting (LSC), and thin layer chromatography (TLC) was used to identify the formation of any E2 metabolites. Oxidation analysis was also used to determine the quantitative amounts of extractable and non-extractable E2 and metabolites at each time point in the aqueous and soil-bound phases. To determine ifE2 preferentially associated with a manure organic carbon fraction (DOC or COC), ultrafiltration was performed. Although E2 was present in both the slurry and CaCh solution phase after 14 d, the fractional recovery for E2 in the slurry solution was 12% and only 8% for the CaCh solution. 17~-estradiol persisted in the parent form and did not convert to its metabolite, estrone (El) in the slurry solution. In the CaCh solution, conversion ofE2 to El was complete after 3 d. Ultrafiltraion results indicated that E2 preferentially associated with the COC fraction of the slurry. Results suggest that the suspended COC fraction facilitates the persistence and potential mobility of E2 in the soil environment.
Evaluating Dynamic Soil Change in the Barnes Soil Series Across Eastern North Dakota
(North Dakota State University, 2015) Montgomery, Brandon
Quantifying long-term, global soil change is of the utmost importance as the human population continues growing and food security needs intensify. North Dakota presents a unique opportunity to study dynamic soil change because of its agricultural prominence and extensive soil survey data. A resampling method to characterize soil change from legacy soil survey data was utilized on a benchmark soil series, the Barnes, in North Dakota. Significant decreases (p<0.05) in soil organic carbon (SOC) were measured in surface horizons of three Barnes pedons, and depending upon management practices, morphologic changes ranged from highly eroded, with the complete loss of the A horizon, at two sites, to non-eroded conditions at sites returned to CRP 25 years ago. Additionally, using remotely sensed evapotranspiration (ET) data as a non-biased proxy for soil function shows modeling potential. These results serve as a proof of concept and demonstrate the need for more comprehensive research.
Evaluating Ornamental Grasses for the Challenging Rain Garden Environment
(North Dakota State University, 2022) Nelson, Randy
Four experiments were conducted to determine the growth and survival of seven species of perennial ornamental grasses, tufted hairgrass [Deschampsia cespitosa (L.) P. Beauv.], switchgrass (Panicum virgatum L.), big bluestem (Andropogan gerardii Vitman), Chinese silvergrass (Miscanthus sinensis Andersson), little bluestem [Schizachyrium scoparium (Michx.) Nash], blue grama grass [Bouteloua gracilis (Kunth) Lag. ex Griffiths], and feather reed grass [Calamagrostis x acutiflora (Schrad.) Rchb.], when subjected to cyclical flood and drought, varying submergence depths and durations, NaCl, and NaCl with petroleum hydrocarbons. Chinese silvergrass and switchgrass survived cyclical soil flooding and drought and submergence for 7-d at a depth of 30 cm while maintaining an acceptable amount of foliar damage. All grasses survived cyclical flood and drought when the soil VWC was maintained at 14% suggesting all seven grasses can withstand periodic soil flooding as long as the water is not too deep. As water depth and duration increased from 4-d to 7-d, little bluestem, blue grama grass, and feather reed grass suffered significant foliar damage. Tufted hair grass and big bluestem suffered significant foliar damage when submerged for 2-d. Switchgrass and feather reed grass survived NaCl loads of up to 6.7 Mg∙ha-1 and maintained a visual damage rating less than three making them suitable for planting in rain gardens or bioretention systems receiving NaCl runoff. Switchgrass also tolerated motor oil at rates up to 5% in combination with NaCl at rates up to 6.7 Mg∙ha-1. Switchgrass would be an ideal grass for planting in areas receiving both contaminates. Tufted hair grass has limited tolerance to NaCl or motor oil and should not be planted in areas that may receive those contaminates in stormwater runoff. Big bluestem and little bluestem have limited tolerance to NaCl but some tolerance to motor oil and may be candidates for planting in areas receiving only motor oil in stormwater runoff. Chinese silvergrass and blue grama grass can tolerate moderate levels of NaCl and motor oil while maintaining a visual damage rating of four or less and would be candidates for planting in areas that receive moderate amounts of both pollutants in stormwater runoff.
Evaluation of 1:5 Soil to Water Extract Electrical Conductivity Methods and Comparison to Electrical Conductivity of Saturated Paste Extract
(North Dakota State University, 2011) He, Yangbo
Conducting a 1 :5 soil:water extract to measure electrical conductivity (EC) is an approach to assess salinity and is the preferred method used in Australia. However, the influence of salinity on plant growth is predominantly based on saturated paste extract electrical conductivity (ECe) and ECe is recommended as a general method for estimating soil salinity internationally, so it is necessary to convert EC1:s to ECe, The objectives of this research were to 1) compare methods of agitation (shaking plus centrifuging (shaking/centrifuging), shaking, and stirring) for determining EC1: 5; 2) determine optimal times for equilibration for each method across a range of salinity levels determined from saturated paste extracts (ECe) (objectives 1 and 2 are for paper 1); and 3) develop predictive models to convert ECu data to ECe based on four different 1 :5 extraction methods listed above and a USDA-NRCS equilibration technique ( objective 3 is for paper 2). The soils evaluated for the two studies were from north central North Dakota, USA, where 20 soil samples having ECe values ranging from 0.96 to 21 dS m-1were used for the first study (objectives 1 and 2), and 100 samples having ECe values ranging from 0.30 to 17.9 dS m-1were used in the second study (objective 3). In the first study, for each method, nine equilibrium times were used up to 48 hrs. In the second study, a uniform agitation time (8 hrs) was applied to the first three agitation methods, and 1 hr was also used for the USDA-NRCS method. For the first study, significant relationships (p < 0.05) existed between values ofEC1:s and agitation time across the three methods. Agitation methods were significantly different (p S 0.05) from each other for 65% of the soils and shaking/centrifuging was significantly different (p < 0.05) from stirring for all soils. In addition, for 75% of the soils, shaking/centrifuging was significantly different (p :S 0.05) from shaking. Based on these results, methods were analyzed separately for optimal equilibration times. The agitation times required for the three methods to reach 95 and 98% of equilibration were a function of the level of soil salinity. For soils with ECe values less than 4 dS m·1, over 24 hrs was needed to obtain both 95 and 98% of equilibration for the three methods. However, less than 3 and 8 hrs were needed to reach 95 and 98% equilibration, respectively, across methods for soils having ECe values greater than 4 dS m·1. These results indicate that establishing a standard method is necessary to help reduce variation across EC1:s measurements. In the second study, the value ofECe was highly correlated with EC1:s (p < 0.0001) across four agitation methods in non-transformed, log10- transformed, and dilution ratio models through regression analysis. The values of coefficient of determination (r2 ) were greatly improved and average about 0.87 using log10- transformation compared to other two models (r2 values of about 0.68 for the nontransformed models and 0.69 for the dilution ratio models). Since agitation methods were determined to be highly correlated with each other, any regression model determined under the four agitation methods were applicable for the estimation of ECe from another method. The results from this research indicate that comparing data across studies should be done with caution because both agitation method and time can influence results. Also, estimation ofECe from EC1:5 can be done with confidence, but models may not be transferrable across different soil orders or across various salt types.
Evaluation of Active Optical Ground-Based Sensors to Detect Early Nitrogen Deficiencies in Corn
(North Dakota State University, 2014) Sharma, Lakesh Kumar
Corn (Zea mays, L) is an important world crop used as livestock feed, human consumption and ethanol production. Early in-season loss of nitrogen (N) continues to be a problem in corn. Ground-based active optical sensors (GBAO) have shown very promising results in predicting crop yield. In these experiments, two GBAO sensors GS and CC were used within forty-six established corn N-rate trials in North Dakota at the six (V6) and twelve (V12) leaf growth stages in 2011, 2012, and 2013. Corn height at V6 and V12 was recorded manually at each site in all three years. At V6, the GS relationship to yield and the INSEY (INSEY = in-season estimate of yield = sensor NDVI / growing degree days from planting date) value was often improved when the sensor NDVI was multiplied times corn height. Segregating the data sets into sites with eastern high clay conventional-till sites surface soil textures (clay more than 30%) and sites with more medium textures improved all INSEY relationships compared to pooling all sites. Eastern high clay conventional-till sites and eatstern medium textured converntional-till sites were further divided into those higher in productivity (yields greater than 10 Mg ha-1) and those lower in productivity (yields less than 10 Mg ha-1). The data categories differed in their sensor relationships to yield. Within all categories, the sensor relationships at V6 were weaker than those at V12. In the lower yielding eastern high clay conventional-till sites, lower yielding eastern medium-textured conventional-till sites, and the eastern no-till sites, no significant relationship was found at V6. At V12, a relatively weak relationship was only found in the low yielding eastern medium-textured coventional-till sites. The GS and CC were found to identify S deficiency at two sites in 2013. Both sensors detected that as N rate increased, the sensor readings generally decreased. This concept could be used by practitioners to screen sites with early season S deficiency, using an N rich strip in the field.
An Evaluation of Electrical Conductivity Meters for Making In-Field Soil Salinity Measurements
(North Dakota State University, 2010) Briese, Lee Galen
Soil electrical conductivity (EC) can be used as a parameter to assist agricultural producers in making economically important management decisions. Since particular crops and crop varieties respond dynamically to soluble salt levels in relation to crop growth stage and soil moisture content, many management decisions regarding crop type and variety must be made prior to planting. Some crop stress factors could be removed or mitigated if a handheld EC meter could be implemented during the growing season. The objectives of this research were to 1) determine the accuracy of four handheld EC meters for measuring soil EC across a range of environmental temperatures of 15, 20 and 25° C, soil clay concentrations of 10.2, 17.8, 19.3, 32.3 and 50.4 %, and salt solutions containing NaMg- SO4 or Na-Mg-Cl at concentrations of approximately 0, 1, 2, 4 and 8 dS m-1 under controlled laboratory conditions; 2) identify functional differences of the meters that might pose problems for in-field use; and 3) determine if meter price is related to accuracy. The EC values provided by three of the handheld EC meters were significantly different than the standard meter at all treatment levels. Measurements at different temperatures of the standard KCI calibration solution (known EC 1.413 dS m ·1 ) varied by ±0.15, -0.01 to +0.16, -0.14 to -0.03, and ±0.03 dS m-1, for the Hanna Black (Hl993310), Hanna Blue {Hl98331), Field Scout, and SenslON 5 meters, respectively. When salinity was 3 dS m-1 or greater the difference between the test meters and standard meter (EC Response} was larger. Test meter measurements for the salinity by clay interaction were different than the standard meter by ±0.5, ±1, and -2.5 to +1.5 dS m-1, for EC levels of less than 3, 3 to 4, and greater than 4 dS m-1, respectively. The SenslON 5 handheld was the only meter tested that was not significantly different than the standard meter {p::; 0.48}. Test meter accuracy was highly dependent on temperature. Therefore, the most important criteria for selecting a portable meter for in-field EC measurements is the accuracy of the specific meter's temperature measurement and temperature compensation model.

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