Louisiana Soils Research Articles

Soil dissipation and efficacy on itchgrass of soil-applied residual herbicides pendimethalin and clomazone in Louisiana sugarcane.

Sugarcane (Saccharum sp.) growers in Louisiana report that the widely used soil residual herbicide, pendimethalin, is less effective at controlling itchgrass (Rottboellia chochinchinensis), possibly through accelerated dissipation from repeated applications. Some growers have started to use another herbicide, clomazone, in place of pendimethalin for itchgrass control when pendimethalin does not provide the necessary control. Little is known about the dissipation of these two herbicides, especially when applied together, in diverse sugarcane soils in Louisiana. Thus, the objective of the research was to measure the dissipation of pendimethalin and clomazone in soils having high itchgrass pressure. Soil samples from five fields were fortified (4 μg g-1) with clomazone and pendimethalin and monitored over the course of 163 days under laboratory conditions. Herbicide levels were determined by extracting the herbicides from soil with acetonitrile and analyzing the extracts with high performance liquid chromatography (HPLC). The results indicate that clomazone is persistent in the soils studied, with a degradation half-life (DT50) of ≥79 days. Pendimethalin dissipates more rapidly in soil with a DT50 ranging from 7 to 59 days. All itchgrass plants showed injury to herbicide but many grew out of symptoms, and responses were not consistent between soil types. Pendimethalin dissipation varied greatly between soil types, yet clomazone was generally persistent in each soil tested. However, when these soils were seeded with itchgrass, pendimethalin was more effective at controlling itchgrass than clomazone. Although persistent in the soils tested, the leaching potential of clomazone may limit its long-term effectiveness. Published 2024. This article is a U.S. Government work and is in the public domain in the USA.

Identification and profiling of silicate-solubilizing bacteria for plant growth-promoting traits and rhizosphere competence

Excessive use of synthetic fertilizers may negatively affect overall soil health and the environment. There is a need to come up with alternative strategies to ensure competitive yields of crops and at the same time maintain soil ecological balance. The use of soil microorganisms as microbial inoculants in agriculture is considered an alternative approach to enhance crop growth. Soil is a good source of microorganisms that are capable of producing different beneficial enzymes such as silicase, phosphatase and other growth-promoting enzymes which are important in crop growth. Soil beneficial microorganisms such as silicate-solubilizing bacteria play an important role in solubilizing insoluble forms of silicates that are important in crop growth. This study was conducted to identify and profile silicate-solubilizing bacteria (SSB) in Louisiana soils and to document the colonization potential of SSB in rice (Oryza sativa) plants. Bacterial isolates were spot-inoculated on silica agar medium and incubated at 37 °C for 48 h. The clearing zone around colonies was measured and used to compute for solubilization index (SI), i.e., halo diameter (mm)/colony diameter (mm). Despite of the abundance of microorganisms found in these soils only 20 bacterial isolates are capable of solubilizing silicates; 16 were with low (SI < 2.0) and 4 with intermediate (2.00 < SI < 4.00) solubilization capacities. Further analysis also revealed that three of the isolates with intermediate silicate solubilization capacities also produced plant growth-promoting enzymes: phosphatase, 1-aminocyclopropane-1-carboxylic acid deaminase and indole-3-acetic acid enzyme. Based on the sequencing information and the phylogenetic tree, the putative SSB were identified into four genera: Aeromonas, Bacillus, Enterobacter and Pseudomonas. The fluorescent microscopy analysis revealed that the GFP-tagged SSB can colonize roots of young rice seedlings, a good indicator of SSB potential as seed treatment for scaling up its application in production field. Furthermore, information on the survival of SSB inoculates in different soil-plant systems in Louisiana and impact of management practices on SSB activity and population are needed to fully develop this bio-based approach to improve Si nutrition in soil and plants.

Property Risk Assessment for Expansive Soils in Louisiana

The physical properties of soil can affect the stability of construction. In particular, soil swelling potential (a term which includes swelling/shrinking) is often overlooked as a natural hazard. Similar to risk assessment for other hazards, assessing risk for soil swelling can be defined as the product of the probability of the hazard and the value of property subjected to the hazard. This research utilizes past engineering and geological assessments of soil swelling potential, along with economic data from the U.S. Census, to assess the risk for soil swelling at the census-block level in Louisiana, a U.S. state with a relatively dense population that is vulnerable to expansive soils. Results suggest that the coastal parts of the state face the highest risk, particularly in the areas of greater population concentrations, but that all developed parts of the state have some risk. The annual historical property loss, per capita property loss, and per building property loss are all concentrated in southeastern Louisiana and extreme southwestern Louisiana, but the concentration of wealth in cities increases the historical property loss in most of the urban areas. Projections of loss by 2050 show a similar pattern, but with increased per building loss in and around a swath of cities across southwestern and south-central Louisiana. These results may assist engineers, architects, and developers as they strive to enhance the resilience of buildings and infrastructure to the multitude of environmental hazards in Louisiana.

Draft Genome Sequences of 20 Aspergillus flavus Isolates from Corn Kernels and Cornfield Soils in Louisiana.

Aspergillus flavus is a common saprophyte and opportunistic fungal pathogen that infects plants, animals, and humans. It also produces numerous toxic and nontoxic secondary metabolites. Here, we report the draft genome sequences of 20 A. flavus isolates, belonging to 16 vegetative compatibility groups, from Louisiana corn kernels and cornfield soils.

Modified Time Factor to Estimate the Duration of Pile Setup

Pile setup is defined as the increase in pile capacity with time. This increase in pile capacity starts immediately after end of driving (EOD). Majority of the setup conducted during the consolidation period followed by a small amount during the post-consolidation period. However, there is no available methodology to estimate the duration of setup during the consolidation period, and to establish a theoretical upper time limit for pile setup capacity beyond which pile setup capacity can be neglected. This paper examines or focuses to develop a methodology to estimate the time duration of pile setup. Three instrumented test piles (TPs) were driven mainly in clayey soil in Louisiana besides regular bridge construction projects. The piles were instrumented with sister bar strain gages to measure the load transfer along the piles’ length, and four sets of pressure cells and piezometers were installed on each pile face to measure the total stress, effective stress and excess pore water pressure (PWP) with time. Dynamic and Static load tests were performed for a duration of 6 months after EOD and hence study setup. Piezocone dissipation tests were performed at each TP locations at different depths to measure the horizontal coefficient of consolidation (ch) besides the regular laboratory and in situ cone penetration test (CPT) to characterize the subsurface soil condition. The piezometers that were installed on the pile face showed that the dissipation continued from 2.5 h to 90 days after EOD depending on the soil properties. The equation that was proposed by Teh and Houlsby (Geotechnique 41(1):17–34, 1991) for dissipation test of piezocone was adopted to calibrate the time factor for pile. A new modified time factor for pile (Tpile*) was proposed in this study to estimate the duration of pile setup.

Sorption and Desorption Characteristics of Tylosin in Three Louisiana Soils.

The macrolide antibiotic tylosin is widely used in animal production, but its environmental fate is not fully understood. Objectives of this study were to determine the effect of pH on tylosin A sorption and desorption in three sandy loam soils from Louisiana, USA, that had long histories of poultry waste application, to model sorption and desorption, and to estimate the effect of high soil organic matter on sorption. Twenty-four-hour sorption isotherms (5 to 200 mg L in 0.01 M CaCl) at pH 4.5, 6.0, and pH 7.5 were described by the Freundlich model. Desorption from the 200-mg L set at constant pH by 10 24-h extractions with 0.01 M CaCl recovered 43 to 98% of the added tylosin A, and further desorption with methanol increased recovery from 66 to 100%. Single-point distribution coefficient, as a function of pH from 4 to 9 in 0.01 M CaCl exhibited maxima from pH 6 to 7, reflecting increasing sorption of the positively charged form with increasing pH up to about the pKa. The data were well described, modeling pH-dependent negative charge according to Henderson-Hasselbalch along with tylosin speciation. Using soil from which organic matter had been removed by HO gave three to six times greater K at pH 6 to 7, but without or with reduced maxima. The data could be approximately described without invoking pH-dependent surface charge. Further study is needed to confirm whether an increase in soil organic matter with poultry waste application decreases tylosin sorption, thus increasing environmental risk.

Modelling and comparing 3-D soil stratigraphy using subsurface borings and cone penetrometer tests in coastal Louisiana, USA

ABSTRACTComplex subsurface geology of coastal Louisiana, formed under fluvial, deltaic, and sea level influences, increases the uncertainty in design and construction of hard and natural infrastructure. In this study, twenty-four (24) collocated soil borings and CPTs at the Inner Harbor Navigation Canal (IHNC) in New Orleans, Louisiana were used to construct multiple three-dimensional (3-D) soil stratigraphy models by ordinary kriging. To explore the spatial distribution of soils at the site, four soil stratigraphy models were established, including the unified soil classification system (USCS) from borings and three constructed using soil behaviour type (SBT) correlations. The SBT correlation using friction ratio () and corrected cone resistance () was found to better represent organic soils pervasive in coastal Louisiana compared using normalised friction ratio with normalised cone resistance, and using soil classification boundary. The comparison shows that the normalisation of sleeve resistance translates the data to higher normalised friction ratio compared to values. The boring and CPTu sounding comparisons suggest that extending the from 8% to 20% in the Rf–qt chart to better capture the organic-rich soils in coastal Louisiana.

Comparing carbon accumulation in restored and natural wetland soils of coastal Louisiana

Louisiana's chronic wetland deterioration has resulted in massive soil organic matter loss and subsequent carbon release through oxidation. To combat these losses, and reestablish ecosystem function, goods, and services, many restoration projects have been constructed or planned throughout coastal Louisiana. There are significant data gaps and conflicting results regarding wetland contributions to global warming, especially related to carbon sequestration in restored wetlands. An exceptionally large data set was used to derive carbon accumulation rates from key soil characteristics and processes. Assessments and comparisons of bulk density, organic matter, total carbon, vertical accretion (short- and longer-term), and carbon accumulation rates were made across time (chronosequence) and space (i.e., coastwide, watershed basins, and vegetation zones). Carbon accumulation rates in the Louisiana coastal zone were generally correlated to hydrogeomorphology, with higher rates occurring in zones of high river connectivity or in swamp or higher salinity tolerant marsh. On average, naturally occurring wetlands had higher carbon accumulation rates than restoration sites. Although some restoration measures were higher, and most showed increasing carbon accumulation rates over time. Results demonstrate that although wetland restoration provides many ecosystem benefits, the associated carbon sequestration may also provide useful measures for climate change management.

A Numerical Study on Installation Effects and Long-Term Shaft Resistance of Pre-Bored Piles in Cohesive Soils

Pre-boring is a technique widely used to facilitate large displacement pile driving in hard/dense soils, but usually at the expense of reducing the long-term shaft resistance of the pile. In the US, it is a routine practice for large displacement pile to be driven through dense cohesive soils with the ultimate capacity of pre-bored piles usually being determined based on empiricism and local experience. Understanding and quantifying the impacts of pre-boring installation on pile capacity can greatly help geotechnical design engineers to understand the interactions among the factors of pre-boring, pile size, soil conditions, and so forth and to improve the design and construction qualities of pile foundations in hard/dense soils. Due to the high cost and time involved with field instrumentation and testing on pre-bored piles, a numerical analysis study was funded by the Louisiana Department of Transportation and Development (DOTD) as a first step to exploring the impacts of pre-bore size on the long-term shaft resistance reduction of piles. This study was conducted using a practical finite element model that integrates the entire process from pile installation through subsequent consolidation to pile loading. The long-term shaft resistance was then examined after full consolidation by applying a vertical shear displacement on the soil element adjacent to the pile until the ultimate state was reached. Based on the numerical simulations, a set of reduction factor curves were then developed for a typical Louisiana soil stratum, which may provide guidelines for better design and construction of pre-bored piles in Louisiana.

Predicting the Performance of Highway Embankment Slopes

Resilience of transportation infrastructure, such as highway embankments, is critical to avoiding commuter delays and costly repairs. The majority of highway embankments in Louisiana and Texas are in marginal condition because the high-plasticity clays that are used during construction will moisten with time to significantly lower strengths. The ring shear tests demonstrate that the Gamez and Stark [1] empirical correlations are applicable to Texas and Louisiana soils. The soil water retention curves at each site were fitted to the Van Genuchten model [2]. For example, the air entry values vary from 0.013 to 0.053 kPa-1 in Louisiana and from 0.008 to 0.01 kPa-1 in Texas. The implications of this wide range of air entry values is that the matric suction pressure required to saturate and desaturate controls the pore-water pressure build-up during a rainfall event.

Effect of Silicate Slag Application on Wheat Grown Under Two Nitrogen Rates.

Field studies were established on the alluvial floodplain soils in Louisiana, from 2013 to 2015, to evaluate the effect of silicate slag applications on productivity of wheat (Triticum aestivum), under sufficient and high nitrogen (N) application rates. Treatments were arranged in a randomized complete block design, with four replications consisting of twelve treatments: a factorial combination of two N (101 and 145 kg N ha−1) and five silicate slag rates (0, 1, 2, 4.5, and 9 Mg ha−1), and two control plots (with and without lime). Nitrogen had a greater impact on wheat productivity than silicate slag application. Wheat grain yield reached over 7000 kg ha−1 with applications of 145 kg N, and 9 Mg silicate slag per ha for soil having Si level <20 mg kg−1. Yield increases due to N or Si were attributed to the increase in number of spike m−2 and grain number spike−1. Silicate slag application effectively raised soil pH, and availability of several plant-essential nutrients, including plant-available N (nitrate, NO3−), demonstrating the benefits of slag application are beyond increasing plant-available Si. The benefits of silicate slag application were clearly observed in wheat supplied with high N, and on soil with low plant-available Si.

Survey of the plant-available silicon status of agricultural soils in Louisiana

ABSTRACTAdequate silicon nutrition in plants has shown positive effects on the growth and yield of the crop and physico-chemical properties of the soil. Hence, this study was initiated to survey the plant-available silicon in the agricultural soils of different parishes of Louisiana. Soil samples were collected from 212 representative agricultural fields of 27 agrarian parishes of Louisiana. Poor correlations between deionized water, calcium chloride, and other extractants suggest that the unbuffered calcium chloride extraction may reflect only a transient status of soil soluble silicon similar to deionized water extraction procedure. Also, acetic acid-2 extraction procedure may reflect the net effects of the sorption/desorption reactions by extracting the readily as well as the slowly releasable silicon that control solubility, thus giving a true measure of current availability. Compared to the previously established critical soil silicon levels, several agricultural fields of Louisiana were deemed to be low in plant-available silicon.

Crude Oil Effects on Redox Status of Salt Marsh Soil in Louisiana

Core Ideas Crude oil did not lower redox status of wetland soil. Crude oil delayed return to aerobic threshold after draining. Oil in marsh soil can depress redox during low water events. In 2010, the Deepwater Horizon (DWH) oil spill triggered extensive research on crude oil impacts on flora and fauna of the Gulf of Mexico. Little research has investigated impact of spilled oil on redox condition of wetland soil. Redox condition is an excellent proxy for oxygen levels, which control biogeochemical functions linked to valuable ecosystem services. The goal of this study was to quantify effects of crude oil on wetland soil redox conditions in cores collected from a salt marsh in Barataria Bay, LA. Treatments tested were nonoiled control, weathered crude oil at the soil surface, fresh crude oil at the soil surface, and a layer of buried weathered crude oil 5 cm beneath the soil surface to mimic the presence of buried oil found in marshes. No significant differences in redox potentials were detected among treatments at any depth at the end of the 35‐d flooded, anaerobic study. After drainage of the cores began, redox was measured to the time to reach the aerobic threshold (+300 mV) within the rhizosphere. Mean redox values for control cores reached +300 mV after 193 h. Both fresh and weathered crude oil surface treatments reached +300 mV after 316 h while the buried crude oil treatment reached the aerobic threshold after 370 h. These results suggest the presence and location of crude oil in the soil profile can impact soil redox conditions which could alter biogeochemical processes over the long term and induce oxygen stress on wetland vegetation and organisms in the soil.

Settlement-induced bending moments on pile-founded floodwalls

T-walls are pile-supported floodwalls commonly built in New Orleans. They are founded on long concrete or steel battered piles and include a sheet pile cut off for seepage and gradient control. Since soils in southern Louisiana contain soft and compressible silt and clay, these floodwalls need to be designed to resist flood loads and loads produced by consolidation of soft soil under the weight of new fill. In an attempt to develop a comprehensive T-wall design procedure that appropriately considers field conditions, the United States Army Corps of Engineers New Orleans District partnered with Rensselaer Polytechnic Institute and Virginia Polytechnic Institute and State University. A testing programme was developed to perform centrifuge tests that would provide insight into the mechanisms and magnitudes of settlement-induced bending moments and reliable datasets for validation of numerical models. This paper describes the experimental approach and presents two centrifuge tests with T-walls resting directly on clay. The bending moments on the battered piles significantly increased under the weight of the new fill. With settlement around the piles reaching values of 1·5 m, the bending moments at least doubled over the testing course, with maximum values observed at the top third of the pile length.

Establishing Soil Silicon Test Procedure and Critical Silicon Level for Rice in Louisiana Soils

ABSTRACTCalibration of crop responses to applied silicon (Si) serves as a basis for developing Si fertilizer recommendation guidelines. A greenhouse experiment was set up in a randomized complete block design with five replications, two sources of Si (wollastonite and slag) and four Si rates (0, 170, 340 and 680 kg ha−1) to calibrate plant-available Si for growing rice in Louisiana soils. Silicon concentrations were determined in soils using seven different extraction procedures. Based on a quadratic model (p < 0.05), the estimated soil Si critical level using 0.01 M calcium chloride (CaCl2) for Sharkey clay soil was 110 mg kg−1 while for Crowley silt loam and Commerce silt loam, levels were 37 and 43 mg kg−1, respectively. These results suggest that suitability of an extractant that gives the best estimate of plant-available Si could considerably depend on soil type and it is unlikely that there is a universal extractant for all soils.

Release and Sorption Pattern of Monosilicic Acid from Silicon Fertilizers in Different Soils of Louisiana: A Laboratory Incubation Study

ABSTRACTThe amount of monosilicic acid (H4SiO4), which is the plant-available form of silicon (Si), released from fertilizers can be influenced by Si source and soil properties. A series of laboratory experiments were conducted using six soil series from Louisiana to document the differences in the release characteristics of H4SiO4 from wollastonite and slag. Monosilicic acid in solution released from slag declined with time while wollastonite consistently increased its concentration across all soil suspensions well above 40 µg mL−1. Among these soil series, soils high in organic matter and clay were seen to have maximum percent sorption (up to 79%) with minimum polymerization of H4SiO4. The presence of ions like aluminum (Al) and magnesium (Mg) enhanced the process of H4SiO4 polymerization, which led to a decrease in H4SiO4 concentration in solution. Evident relationships were observed between H4SiO4 concentration in solution with added Si sources and sorbed quantity from soil solutions.

Phosphorus Runoff from Coastal Plain Forest Soil in Louisiana

ABSTRACTAlthough not a common practice, poultry litter (PL) may be used for forest fertilization. Despite usually low soil phosphorus (P) and runoff under forest, repeated or high rates of PL application may cause appreciable P loss. Phosphorus in natural runoff under loblolly pine (Pinus taeda L.) fertilized with PL, downslope P enrichment of surface soil, and P runoff during simulated rainfall (a) 5 years post-application and (b) where straw was harvested were measured. Relationships of runoff P (dissolved reactive, dissolved, and total) concentration and load to soil P (Bray 2 and water-extractable in two depths) and hydraulic conductivity were examined. Post-application loss of P was lower than reported for pasture. There was little downslope P movement. Runoff P was related to the corresponding form of soil P (R2 = 0.28–0.48) but likely affected by P leached from the O horizon. Loads could be estimated from regressions.

Release of As, Ba, Cd, Cu, Pb, and Sr under pre-definite redox conditions in different rice paddy soils originating from the U.S.A. and Asia

The release dynamics of dissolved arsenic (As), barium (Ba), cadmium (Cd), copper (Cu), lead (Pb), and strontium (Sr) was determined in seven different paddy soils under controlled-redox conditions by using an automated biogeochemical microcosm apparatus. Seven surface soils were collected from five major rice-cultivating states in the United States (Arkansas, California, Louisiana, Mississippi, and Texas), and from two Asian regions: Hangzhou (China) and Java (Indonesia). The impact of redox potential (EH), pH, dissolved organic carbon (DOC), iron (Fe), manganese (Mn), and sulfur (S) on the release dynamics of the elements was quantified. The experiment was conducted stepwise from reducing (−270mV) to oxidizing (+676mV) soil conditions. Soil pH increased with decreasing soil EH. Concentrations of DOC and dissolved As, Fe, Mn were increased under reducing conditions as compared to oxidizing conditions. In opposite — the release of Ba, Cd, Cu, and Sr to soil solution increased under oxidizing conditions as compared to reducing conditions. The decrease of Ba, Cd, Cu, and Sr concentrations under reducing conditions could be caused by the relatively high pH and/or metal-sulfide precipitation. Lead showed an inconsistent trend with EH in the studied soils (All Soils). Factor analysis demonstrates that As, Fe, Mn, and DOC were associated in one group, while Ba, Sr, Cd, Cu, and EH were banded together in one cluster. These results indicate that the chemistry of DOC, Fe, and Mn might be stronger linked to the dynamics of As than to the dynamics of Ba, Cd, Cu, Pb, and Sr in these soils.The canonical discrimination analysis explained 85% of the variability of the geochemical behavior of the different soils and showed that the individual soils can clearly differentiate from each other. However, the Arkansas and Louisiana soils were relatively similar in their geochemical behavior, and the Indonesian and Texas soils were close, while and the California soil showed a different geochemical behavior. The behavior of Sr, Ba, S, DOC, and EH, respectively, was mainly responsible for the discrimination of the soils. In particular, our findings suggest that aerobic conditions can lead to a release of Ba, Cd, Cu, Pb, and Sr while a release of As under anaerobic conditions was observed. These results provide critical information on the potential risk of toxic elements for the sustainable management of paddy rice soils.

Growth and yield of corn grown on two alluvial soils of Louisiana applied with different phosphorus rates

ABSTRACTThe influence of soil properties on phosphorus (P) availability of Louisiana alluvial soils is not fully understood. A pot experiment was conducted in 2011 to evaluate the effect of different P fertilizer rate (0, 34, 67, 101 and 134 kg P2O5 ha−1) on corn growth and development on Perry clay and Commerce silt loam (sil) soils and relate Mehlich-3 and Bray-2 soil test P values with yield, total biomass, and P uptake of corn. The Bray-2 P values were six times higher than Mehlich-3 P values for Commerce sil while they were similar for Perry clay. Bray-2 and Mehlich-3 extractable-P of both soils increased with increasing P rate but only corn grown on Perry clay responded to P rate (P < 0.05). Implementation of appropriate testing procedure for estimating plant-available P in soil is an important component of effective P fertilization guidelines for corn.

Laboratory characterization of cementitiously treated/stabilized very weak subgrade soil under cyclic loading

This research study was performed to examine the appropriate treatment/stabilization schemes for very weak subgrade soils at high water contents, and to evaluate the corresponding performance-related properties [e.g., resilient modulus and permanent deformation] for use in the design and analysis of pavement structures. Five different soil types, that represent the typical range in subgrade soils in Louisiana, were collected and considered in this study. Three different moisture contents (at the wet side of optimum), producing a raw soil strength of 172kPa (25psi) or less, were selected for treatment/stabilization. The percentage of cementitious stabilizer (lime or cement) was determined to achieve a target 7-day strength value of 345kPa (50psi), as treatment for working table applications, and 1034kPa (150psi), as stabilization for subbase applications. Repeated load triaxial (RLT) tests were performed on the laboratory-molded treated/stabilized specimens in order to evaluate their resilient modulus and to study their deformation behavior under cyclic loading. A good correlation was observed between the water/cement ratio and both the resilient modulus and the permanent deformation of the specimens. The soil specimens were compacted at low water/cement ratios and showed better performances than those compacted at high water/cement ratios. The test results also showed that the use of a direct correlation between the unconfined compressive strength (UCS) and the resilient modulus for cementitiously stabilized soil can be misleading. In the case of heavily treated/stabilized subgrade soils for subbase applications, the permanent deformation of this layer can be ignored in pavement design.