Intact Soil Research Articles

Antagonistic activity of Trichoderma crassum Gmaxr1 against Macrophomina phaseolina Gmax20 of the Soybean Crop

Charcoal rot is a fungal disease of soybean caused by Macrophomina phaseolina. Soybean contains proteins, vitamins and fats. It is an important source of nutrition in developing countries. In the present study, Macrophomina phaseolina Gmax20 was isolated from soybean-infected plant whereas Aspergillus niger, Aspergillus flavus, Aspergillus fumigatus and Trichoderma crassum Gmaxr1 were isolated from a healthy soybean plant’s intact rhizospheric soil. The isolated antagonists were tested against the Macrophomina phaseolina Gmax20 under in vitro conditions. The results showed that T. crassum Gmaxr1 showed the highest inhibition percentage (16.98%, 23.08% and 54.04%) on 1st, 2nd and 3rd day than other selected antagonists against M. phaseolina Gmax20. Thus, due to the maximum inhibition percentage of T. crassum Gmaxr1 against M. phaseolina Gmax20, it can be exploited as a proficient bioagent for the management of charcoal rot disease.

Response of the nitrogen processing bacterial community to water level fluctuation and nitrate availability in an intact marsh soil column.

Wetlands are known to experience fluctuations in water levels and receive exogenous nitrogen inputs that affect various organisms, including soil microorganisms. To study the impact of these factors on microbial diversity, we collected intact soil columns from a Phragmites australis-dominated site in the Qixing River National Nature Reserve in Northeast China. In a laboratory experiment, we simulated water level fluctuations and exogenous nitrogen inputs to the soil columns and examined the associated changes in the relative abundance of 51 bacterial genera involved in nitrogen cycling processes. Our findings revealed that different bacterial genera exhibited varying relative abundances across treatments. Specifically, Massilia showed the highest total relative abundance at the genus level, while Planctomyces had the second highest, and Campylobacter had the lowest abundance. The DESeq2 model, based on negative binomial distribution, revealed that the tags of bacterial genera were significantly correlated with soil depth, but not with water levels or nitrogen concentrations. However, the addition of a 30mg/L nitrate solution caused a decrease in the relative abundances of bacterial genera with decreasing water levels, while a 60mg/L concentration of nitrogen resulted in a decrease and then an increase in the relative abundances of bacterial genera with decreasing water levels. Our study provides valuable insights into the response of nitrogen-cycling bacteria to changes in different environmental conditions.

Fine root decomposition and macronutrient release in temperate forests: Examining the litter bag and intact soil core approaches and their relationship with fungal community composition

Accurate measurement of decomposition of fine roots in forests is important for understanding nutrient cycling, carbon dynamics and biotic responses; however, various sources of error or bias interfere with commonly used approaches. Most studies of fine root decomposition have used the buried root litter bag method, but this method may underestimate decay rates based on comparisons with the less disruptive, intact soil core approach. We compared these two methods for one year for seven temperate forest trees growing in twelve monospecific plantations in central New York. The experimental design included four species that form arbuscular mycorrhizae (sugar maple, red maple, cherry, tulip poplar) and three with ectomycorrhizae (pine, spruce, oak). We also examined macronutrients (N, P) release and fungal community composition of decaying fine roots using Illumina sequencing. Across the seven species and 12 plots, fine root decay rate was significantly higher for intact cores than litter bags, with the difference being approximately 12 %, a smaller disparity than that observed in previous comparisons. However, one species (Norway spruce) showed the opposite trend. Similarly, N and P release from decaying roots was significantly greater for the intact core method, but again with an exception (red oak). No consistent effects of mycorrhizal type on the method effect or decay rate and nutrient release were detected. Fungal communities in decaying roots differed between the two methods; nevertheless, Mycena spp. dominated most plots for both methods. These results further emphasize the notion that decay rates and nutrient mobilization of fine roots in forests are usually underestimated by the litter bag approach.

Leaching of soil legacy nitrogen in intact soil columns and significance of soil macropore structure

Excessive application of chemical fertilizers accumulates nitrogen in soil (soil legacy nitrogen), and its release has a long-term impact on environmental quality. The information regarding leaching of soil legacy nitrogen and role of soil pore structure is scarce. Fifteen undisturbed soil cores with a depth of ~200 mm were collected from five paddy fields in a subtropical area of China, and soil pore structure was characterized with X-ray computed tomography. The batch leaching column experiments were conducted to investigate the nitrogen leaching from the soil cores. In the leachate, inorganic nitrogen (NO3−–N and NH4+–N) accounted for 73–85 % of total dissolved nitrogen (TDN), which showed small variations among the five sampling sites. The NO3−–N, NH4+–N and TDN concentrations in the leachate over the number of leaching times could be well fitted with the Gaussian, exponential or linear models, suggesting that different nitrogen forms showed variable leaching dynamics. NO3−–N and TDN leaching losses continued to increase with the number of leaching times, whereas NH4+–N leaching from the soil had a threshold value. Combination of changes in soil nitrogen content after leaching, the lagging effect of soil legacy nitrogen may be partly attributed to the continuous transformation of NH4+–N and organic nitrogen into NO3−–N in the soils. Besides the nitrogen content in the soil, the most important factor of soil pore structure controlling NO3−–N and TDN leaching loss was the fractal dimension; NH4+–N was mainly controlled by connectivity. The present study highlighted the importance of soil pore structure and nitrogen format transformation in the leaching of soil legacy nitrogen.

Life in the dark: Impact of future winter warming scenarios on carbon and nitrogen cycling in Arctic soils

The high Arctic region is warming faster than other areas globally, with widespread decreases in snow cover and longer growing seasons. This is expected to greatly influence plant-microbial carbon (C) and nitrogen (N) cycling and thus ecosystem functioning, particularly when soils remain unfrozen during the dark winter period and no photosynthesis is possible. To better understand this response, we studied the effects of different winter warming scenarios on soil C and N dynamics. We collected intact soils cores from two contrasting biomes from Svalbard, namely a moss-dominated peat mire and purple saxifrage-dominated dry tundra heath. In the laboratory, we used an Arctic annual light regime and three contrasting winter temperature regimes to simulate a range of climate scenarios: (i) current climate in which the soils were frozen in winter and thawed in the summer, (ii) a year 2050 regime in which the soils were both frozen and thawed in winter, and (iii) a year 2100 regime in which the soils remained unfrozen during winter. We monitored greenhouse gas (GHG) emissions (CO2, CH4 and N2O) and nutrients in soil solution (DOC, NO3−, NH4+, P) over a one-year period. In the peat mire, warmer winters increased CO2 emissions due to increased microbial activity but had little effect on methane or N2O fluxes. Warmer winters also decreased dissolved organic carbon and nutrients in soil solution. In the dry tundra heath, warmer winters increased nitrate availability but did not greatly alter CO2, CH4 or N2O gas fluxes or other nutrients. Warming in the dry tundra health induced earlier spring flowering and shifts in vegetation composition. Overall, we present clear evidence that warmer winter conditions are likely to alter C and N cycling in Arctic soils, with implications for plant productivity and vegetation community composition.

The effect of antecedent soil moisture conditions on soil nitrous oxide and dinitrogen dynamics after wetting: An intact soil core study

Ruminant excreta urinary‑nitrogen (N) deposited onto pasture soil generates inorganic-N concentrations in excess of the pasture's immediate requirements. Consequently, nitrous oxide (N2O) and dinitrogen (N2) may be emitted from the urine-affected soil via denitrification. Soil moisture plays a key role in determining the end-product of denitrification. Although the effects of soil moisture and drying-wetting cycles on soil N2O production have been widely studied using sieved soils in a controlled environment, these experiments may not reflect the actual conditions in the field due to the lack of plant cover and the disturbed soil structure. To address this an experiment was performed using intact soil cores (7.5 cm depth), with pasture plants present, under controlled environmental conditions (20 °C, 8 h of light per day). The 15N flux method was used to investigate how antecedent soil moisture affected soil N2O production and consumption in a pasture soil after wetting with a nitrate (NO3−) solution. The results showed that the antecedent dry condition (25 % WFPS, Dp/Do = 0.1783) increased the magnitude of the N2O flux peak after the soil was wetted (75 % WFPS, Dp/Do = 0.006) when compared to antecedent wet conditions (50 % WFPS, Dp/Do = 0.0503). There were no differences in the denitrification and nitrification related functional gene abundances between the two antecedent conditions post-wetting, indicating that the effect was not regulated by microbial changes but by the intensity of the “Birch effect” induced by soil wetting. The N2O reduction related gene (nosZII) abundance decreased after wetting with the NO3− solution, indicating a suppression effect on N2O consumption from the NO3− applied that overrode the potential “Birch effect” on N2 emission. The results of the study indicate that rewetting of antecedent dry soil increase N2O emissions but not N2 emissions when the soil NO3− concentration is high.

Sugarcane growth variation based on rainfall and soil permeability in Takalar, Indonesia

The germination and sprouting phases of sugar cane are critical periods that determine productivity. This phase occurs when the sugar cane is 1-3 months old and requires an adequate supply of water to support the formation of shoots. Poor soil conditions and high rainfall can cause the failure of bud formation. This study aims to determine the relationship between rainfall and soil permeability in successfully constructing sugarcane shoots. We divided the 1 ha research area into nine points (A, B, C, D, E, F, G, H, I) to observe plant growth and soil permeability. The growth factors measured included the number of stems, diameter, and plant height, measured by zigzag. Intact soil samples at a 0-15 cm depth were then analyzed in the laboratory using Darcy’s law to determine the value of soil permeability. The results showed variations in sugarcane growth in the nine study plots. The average number of sugarcane stalks is eight stalks/meter with a height of 159 cm and a diameter of 3 cm. The low soil permeability value of 0.13-0.5 cm/hour cannot compensate for the average rainfall during the budding phase, thereby suppressing plant growth by up to 50% of the average productivity that should be.

Tracing Low‐CO2 Fluxes in Soil Incubation and 13C Labeling Experiments: A Simplified Gas Sampling System for Respiration and Photosynthesis Measurements

AbstractQuantifying carbon dioxide (CO2) fluxes between soil and atmosphere is key in understanding net ecosystem C exchange and biogeochemical C cycling in plant‐soil systems. In ecosystems with low primary production and sparse vegetation, for example, dry lands or subpolar regions where C fluxes are small, measurement sensitivity is key—even so when measurements are combined with isotopic labeling. Here, we present a simplified gas sampling system developed to facilitate sampling and measurement of low soil CO2 fluxes as well as in situ 13CO2 labeling in the same setup. The capacity of the system was tested in a set of feature tests along with gas measurements of dryland soil‐biocrust systems. The system's sensitivity to capture minor changes in CO2 concentration was confirmed in respiration and photosynthesis measurements of soil‐biocrust systems, where fluxes down to 0.1 μmol CO2 m−2 s−1 were quantified. A balloon, implemented to counterbalance underpressure build‐up during gas withdrawal, mitigated 72% of pressure differences at sampling. The overall system volume was reduced to a minimum to limit contamination caused by residual air, and the design enabled one‐step flushing and evacuation of system compartments and gas sample bags, successfully ruling out cross‐contamination between samples. Ultimately, this system offers a flexible and accessible solution for CO2 measurements that can be applied not only on arid soils with low biological activity and turnover rates, but also on plant‐soil systems. The modifications enabled larger, and thereby more representative, sample volumes to be collected while limiting incubation, contamination, and pressure effects on the intact soil system.

Phosphorus Mobility in Heavily Manured and Waterlogged Soil Cultivated with Ryegrass (Lolium multiflorum)

Extended waterlogging (WL) conditions in heavily manured soils can change soil phosphorus (P) dynamics. We assessed the effects of soil moisture regimes (field capacity (FC) and WL) and P rates on (i) dry matter (DM) yield and P offtake of ryegrass, (ii) changes in soil Fe3+, Fe2+, and soil P, and (iii) risk of P leaching. The treatments were tested in a four-month greenhouse experiment using intact soil columns and annual ryegrass (Lolium multiflorum). The DM yield and P offtake were lower under WL compared with FC. The concentration of Fe3+ was 1984 mg kg−1 (0–30 cm) under FC, but 1213 mg kg−1 at 0–5 cm and 2024 mg kg−1 at 25–30 cm depth under WL. The concentration of Fe2+ was 244 mg kg−1 (0–30 cm) under FC, but 2897 at 0–5 cm and 687 mg kg−1 at 25–30 cm under WL. The water extractable P (Pw) was 12.7 mg kg−1 at 0–5 cm and 9.5 mg kg−1 at 25–30 cm under FC, but 8.6 mg kg−1 at 0–5 cm and 10.5 mg kg−1 at 25–30 cm under WL. The P saturation index (PSI) was 27.2% at 0–5 cm and 17.4% at 25–30 cm under FC, but averaged 11.9% at 0–30 cm under WL. We can conclude that extended WL associated with flooding creates reducing conditions in the soil, thus decreasing the concentration of Fe3+, but increasing the concentrations of Fe2+ and the solubility of P which can exacerbate the risk of P loss with runoff and leaching.

Bacterial community diversity for three selected land use systems as affected by soil moisture regime

Despite their important role in soil nutrient cycling, soil bacterial communities' response to land management practices and soil hydrologic fluctuations are not sufficiently studied. The effects of land use and soil moisture regime on soil bacterial community structure and diversity in the Missouri River Floodplain have been investigated in this study. Three land use systems represented riparian forest (RF), pecan (Carya illinoinensis) orchard/hay agroforestry system (AF), and row crop corn [Zea mays L.]/soybean [Glycine max (L.) Merr.] agriculture system (AG). Microbial diversity indices and the abundance of selected bacterial phyla were investigated in bulk soil samples by performing 16 s rRNA amplicon sequencing. Soil samples were collected from three selected land use systems in September 2020 and May 2021. To simulate the hydrological dynamics of the riparian systems, intact soil cores were subjected to two different soil moisture regimes: saturated (FD) and alternately saturated and field capacity (FL) for 8 weeks of incubation. A control sample was maintained at field capacity for the entire duration of the experiment. Soil physicochemical properties substantially differed among land use. Soil organic matter (OM%) was significantly greater in AF and RF than in AG. Proteobacteria, Actinobacteriota, and Acidobacteriota were found to be the most dominant bacterial phyla across all samples. The bacterial richness and Shannon indices were not considerably different among land use systems. Soil FD conditions considerably increased the abundance of Actinobacteriota in AF soils. The abundance of these phyla was strikingly higher in AF with the greatest organic matter relative to AG and RF under all three water regimes. Further work may be needed to assess the effects of hydrological events on floodplain soils' microbial community indices.

Chernozem Land Use Differentiation by Temperature-Dependent IR Spectra

Granulometric aggregate fractions (20 µm–2 mm) of chernozem soils with different agriculture-use histories (native steppe, permanent bare fallow, arable land, and shelterbelt) were investigated in mid-IR and far IR regions (4000–100 cm−1) by heating in the air from 25 to 215 °C, using ATR FTIR and linear discriminant analysis to differentiate the land-use samples without chemical perturbation. The temperature dependences of the band maxima significantly differed for bands of silicate matrix and bands with the contribution of soil organic matter and were more stable to experimental conditions compared to the absolute positions. The thermal behavior of the integral intensities of the IR bands at 790–750 cm−1 and 440–420 cm−1 that was different compared to pure quartz, may be attributed to –C–H bending of alkanes and (poly)aromatic structures and skeletal bending, and could be used to distinguish intact soils from agriculturally used samples. The different temperature behaviors of the bands for fractions of soils with different land use are shown, with the maximum difference in fractions below 20–50 µm and medium fractions (50–200 µm). Changes in the band-maximum frequencies and the integral intensities of the bands were reversible for a heating–cooling cycle. The linear discriminant analysis of the spectra obtained for granulometric fractions of chernozem soils made it possible to separate the samples of native steppe, arable land, bare fallow, and shelterbelt with a high probability based on the type of vegetation and agrogenic load, mainly on the basis of the spectral ranges associated with biogenic forms of quartz and phytoliths.

Effects of nitrogen addition on greenhouse gas fluxes during continuous freeze-thaw cycles in a cold temperate forest.

Both nitrogen (N) deposition and soil freeze-thaw cycles (FTCs) induce pulses of greenhouse gas (GHG) emissions in cold temperate zones due to changes in soil carbon (C) and nitrogen (N) turnover. However, the combined effects of N addition and FTCs on GHG fluxes have received little research attention, particularly in boreal forests. We conducted a laboratory incubation experiment using intact soil cores from Rhododendron dauricum-Larix dahurica plots to investigate the GHG flux response to these combined effects. We separated the soil samples into seven groups (no, low, medium, and high sodium nitrate addition and low, medium, and high ammonium chloride addition) and exposed each group to continuous FTC conditions. The N2O and CO2 emissions were eventually stimulated by the FTCs, while CH4 uptake was inhibited by FTCs but responded differently under different N addition treatments. All the treatments had substantially increased N2O emissions compared to the control. However, the soil respiration rate significantly increased only with medium sodium nitrate addition, and high levels of N addition (regardless of form) inhibited CH4 uptake. These findings demonstrate that FTCs and N addition (in various forms and levels) have considerable effects on GHG emissions in temperate forest ecosystems. Moreover, dissolved organic carbon (DOC), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and inorganic nitrogen in soil are potential factors that drive GHG emissions and are necessary considerations in predicting future feedback effects of GHG emissions on climate change.

In-situ measuring and predicting dynamics of soil bulk density in a non-rigid soil as affected by tillage practices: Effects of soil subsidence and shrinkage

Non-rigid soils (e.g., Vertisols) present dynamics of bulk density (ρb) due to high shrinkage and swelling. However, the in-situ measurement and prediction of the dynamic of ρb in non-rigid soils are still great challenges. The objectives were to (1) evaluate the performance of the combined soil moisture and thermal property sensors in estimating in-situ ρb dynamics under different tillage practices, (2) and establish mathematic equations to predict the ρb dynamics associated with soil subsidence and shrink-swelling processes during wetting and drying cycles. The in-situ ρb monitoring and periodical intact soil core sampling were conducted in the 0–10 cm and 10–20 cm layers in a Vertisol under three tillage treatments, containing no-tillage (NT), rotary tillage (RT) and deep ploughing (DP). Our results showed that the dual-sensor combination provided accurate ρb estimates in the field over 2021–2022 year (R2 > 0.487, RMSE < 0.177 g cm−3), except for the early stage after deep tillage. The ρb dynamics in the 0–20 cm in the NT and the 10–20 cm layer in RT treatment were mainly caused by shrink-swelling. Whereas the ρb dynamics in the 0–10 cm and 10–20 cm in the DP and the 0–10 cm layer in RT treatment were predominantly determined by soil subsidence first and then shrink-swelling when the accumulative rainfall (Pt) reached 131.8 mm, 186.1 mm, and 79.3 mm, respectively. The ρb dynamics during soil subsidence were well-fitted by an exponential equation related to accumulative rainfall (R2 > 699, P < 0.01), while the ρb dynamics during shrink-swelling were well-fitted by a newly proposed SSCρb equation derived from the Peng and Horn soil shrinkage model (R2 > 589, P < 0.05). Combined with the long-term monitored rainfall and soil moisture, The SSCρb equation and the two-stage equation involving subsidence and SSCρb exhibited good prediction of ρb dynamic from 2017 to 2022 (R2 > 0.453, RMSE < 0.070 g cm−3). The soil subsidence and shrink-swelling process accounted for 3.32%− 12.5% and 2.84%− 14.8% of the ρb variation in tilled non-rigid soils, respectively. Our results demonstrated that the dual-sensor combination can be applied for field ρb monitoring in non-rigid soil. The proposed two-stage equation has great potential for predicting the field dynamics of ρb.

Stress-dependent water retention behaviour of two intact aeolian soils with multi-modal pore size distributions

The water retention curve (WRC) of unsaturated soils plays a significant role in evaluating rainfall-induced geohazards in geological and geotechnical engineering, such as ground subsidence and slope failure. Stress can affect WRC because loading/unloading alters not only density but also pore size distribution (PSD). Previous studies of stress-dependent WRC focused on soils with mono- and bi-modal PSDs only. In this study, the WRCs of intact paleosol and intact loess with quadri- and tri-modal PSDs were measured using suction- and stress-controlled pressure plate tests. The full-range PSDs of tested specimens were determined by combining X-ray computed tomography (CT) and mercury intrusion porosimetry (MIP). Experimental results show that the multi-modal PSDs and hence WRCs of both soils are strongly affected by stress in a similar approach. For instance, the relationship between degree of hysteresis and suction showed a double-humped pattern, in which the Peak-I and Peak-II were identified at the relatively low (0.1–20 kPa) and high (20–400 kPa) suctions, respectively. The application of stress resulted in a decrease of hysteresis in the Peak-I (about 30%) but an increase in the Peak-II (about 31%). The increase of hysteresis in the Peak-II differs from the behaviour of soils with mono- and bi-modal PSDs, mainly because the reduction of mega- and macro-pore diameters upon loading increases pore non-uniformity in the range corresponding to the Peak-II.

BONCAT-FACS-Seq reveals the active fraction of a biocrust community undergoing a wet-up event.

Determining which microorganisms are active within soil communities remains a major technical endeavor in microbial ecology research. One promising method to accomplish this is coupling bioorthogonal non-canonical amino acid tagging (BONCAT) with fluorescence activated cell sorting (FACS) which sorts cells based on whether or not they are producing new proteins. Combined with shotgun metagenomic sequencing (Seq), we apply this method to profile the diversity and potential functional capabilities of both active and inactive microorganisms in a biocrust community after being resuscitated by a simulated rain event. We find that BONCAT-FACS-Seq is capable of discerning the pools of active and inactive microorganisms, especially within hours of applying the BONCAT probe. The active and inactive components of the biocrust community differed in species richness and composition at both 4 and 21 h after the wetting event. The active fraction of the biocrust community is marked by taxa commonly observed in other biocrust communities, many of which play important roles in species interactions and nutrient transformations. Among these, 11 families within the Firmicutes are enriched in the active fraction, supporting previous reports indicating that the Firmicutes are key early responders to biocrust wetting. We highlight the apparent inactivity of many Actinobacteria and Proteobacteria through 21 h after wetting, and note that members of the Chitinophagaceae, enriched in the active fraction, may play important ecological roles following wetting. Based on the enrichment of COGs in the active fraction, predation by phage and other bacterial members, as well as scavenging and recycling of labile nutrients, appear to be important ecological processes soon after wetting. To our knowledge, this is the first time BONCAT-FACS-Seq has been applied to biocrust samples, and therefore we discuss the potential advantages and shortcomings of coupling metagenomics to BONCAT to intact soil communities such as biocrust. In all, by pairing BONCAT-FACS and metagenomics, we are capable of highlighting the taxa and potential functions that typifies the microbes actively responding to a rain event.

Salinization, inundation and tree mortality interact to affect greenhouse gas emissions from stressed coastal forests

Sea level rise and intensifying storms cause salinization and freshwater inundation of coastal forest soils which can result in tree mortality and altered ecosystem carbon (C) cycling. However, it is not yet clear if increased salinity and inundation will affect greenhouse gas (GHG) emissions to feed back with climate change. To assess the impacts of in situ chronic and pulsed salinity on GHG fluxes from coastal forests, we made continuous measurements of carbon dioxide and methane fluxes from intact soil cores collected in 1) an upland forest dominated by loblolly pine (Pinus taeda) and a freshwater swamp dominated by baldcypress (Taxodium distichum) 2) adjacent forest stands within forest types experiencing high versus low salinization and associated tree mortality and 3) before and after pulsed salinity from a hurricane related storm surge. In lab mesocosms, all soil cores were exposed to three levels of rainwater addition to assess potential interactive effects between salinization and inundation. We found that chronic salinization and associated tree mortality decreased soil CO2 fluxes in loblolly, but not baldcypress forest with in situ soil inundation patterns potentially driving the site effect. Additionally, in an upland loblolly forest, pulsed salinity from a storm surge exhibited the potential to increase CH4 fluxes. Finally, the effect of rainwater inundation on CH4 fluxes was greater in low compared to high salinity stands suggesting that salinization may have suppressed the effects of rainwater inundation on CH4 fluxes. Overall, we show that complex interactions between biotic and abiotic conditions in stressed coastal forests can alter GHG emissions, highlighting a need for future research focused on understanding the mechanisms driving GHG fluxes from coastal forests under changing environmental conditions.

Short-term Effects of Indaziflam on Non-native Brome Grass (Bromus spp.), Biological Soil Crusts, and the Endangered Dwarf Bear Poppy (Arctomecon humilis)

Controlling invasive annual grasses is one of the top conservation priorities in the American West. Brome (Bromus spp.) has more recently invaded areas of White Dome Nature Preserve, a conservancy for endemic and endangered or threatened plants in Washington County, Utah, United States, where the use of herbicides could be effective in managing invasion. Ideal habitat for these plants is on gypsiferous soils that are largely associated with biological soil crusts. Intact biological soil crusts are important in a biological communities' ability to resist invasion by annual grasses and are critical for nutrient cycling. However, there is a lack of research on how herbicides affect biological soil crusts and specific rare plant species that are of high conservation priority. We found that indaziflam (Rejuvra, Bayer CropScience, Monheim am Rhein, Germany), applied as a preemergent, was effective at reducing brome density the first growing season after application. Indaziflam also did not initially injure the biological soil crusts. Indaziflam is reported to have multiyear effects of reducing annual grasses, which makes indaziflam a promising herbicide for conservation purposes in areas where the invasive species seed bank needs to be depleted with as little disturbance to biocrusts as possible.

Cover crop and biofuel crop effects on hydraulic properties for claypan soils

AbstractPerennial biofuel and cover crops systems are important for enhancing soil health and can provide numerous soil, agricultural, and environmental benefits. The study objective was to investigate the effects of cover crops and biofuel crops on soil hydraulic properties relative to traditional management for claypan soils. The study site included selected management practices: cover crop (CC) and no cover crop (NC) with corn/soybean rotation, switchgrass (SW), and miscanthus (MI). The CC mixture consisted of cereal rye, hairy vetch, and Austrian winter pea. The research site was located at Bradford Research Center in Missouri, USA, and was implemented on a Mexico silt loam. Intact soil cores (76‐mm diam. by 76‐mm long) were taken from the 0–10, 10–20, 20–30, and 30–40 cm depths with three plot replicates and two sub‐samples per plot replicate per depth. Soil hydraulic properties evaluated for each sample included: saturated hydraulic conductivity (Ksat), water retention, bulk density, and pore size distributions. Results showed with the test of Duncan's least significant differences that treatments of MI (1.18 Mg m−3) and SW (1.21 Mg m−3) had lower values of bulk density averaging across soil depth than CC (1.27 Mg m−3) and NC (1.31 Mg m−3). Management systems significantly increased Ksat with the biofuel treatments at 0–10 cm compared to NC system. The MI management showed a significant increase in macroporosity and fine mesoporosity as compared to other management systems. Slight changes have occurred in the measured soil physical properties for CC system compared to NC plots. Overall, increasing soil organic matter from more plant roots from long‐term biofuel cropping systems can improve soil water storage and crop productivity.

Development of an extended Schnute model for more physically realistic representations of soil water retention and moisture capacity curves

Commonly used soil water retention, θ( h), and moisture capacity, C( h), functions implicitly assume that ( i) the θ( h) data curve is sigmoid-shaped with an inflection and ( ii) the C( h) data curve has a value of zero at soil saturation. Desorption measurements on intact soils indicate, however, that the θ( h) data curve is frequently convex-monotonic in shape with no inflection, and C( h) at saturation is often a finite negative value rather than zero. As these model-data mismatches may cause substantial error in simulation or prediction of near-saturated soil hydraulic properties and water flow, a new “Extended Schnute” θ( h)– C( h) function was proposed that can provide θ( h) curve shapes and saturated C( h) values which are consistent with θ( h) and C( h) measurements. The new function and/or its nested Schnute sub-model provided high-quality and physically realistic fits to desorption data collected from intact cores of coarse sand, loamy sand, loam, clay loam, sandy clay loam, clay, and organic clay soils; and it out-performed or equalled the three-parameter van Genuchten θ( h)– C( h) function for every data-set. The new function also provided accurate and physically realistic representations of θ( h) and C( h) data from structured soils containing macropores and strongly graded pore size distributions. It was concluded that the Extended Schnute model is capable of providing accurate and physically realistic representations for a wide range of θ( h) and C( h) data, and it was further recommended that this model be considered over other models when measurements indicate that θ( h) is convex-monotonic in shape and/or C( h) is not zero at soil saturation.

Growth of Invasive Lupinus polyphyllus (Fabaceae) is Not Affected by Site Invasion History

For invasive plant species that associate with mutualists, the presence of suitable partners or a lack thereof can be important to invasion success. We studied the effects of site invasion history and soil microbiota on the performance, folivore damage, and resistance to a fungal disease of the invasive legume Lupinus polyphyllus (Fabaceae). We discovered that the plant invader benefited from soil microbes: plants treated with an intact soil inoculum nodulated more than those grown in autoclaved soils, and tended to have higher biomass and a smaller relative investment in roots as compared with that in shoots. However, the origin of soil inoculum (previously invaded, uninvaded) had no effect on the invader's performance, the occurrence of folivory or resistance to fungal disease. Our results indicate that mutualistic associations in soils outweigh potential antagonistic interactions between plants and soil pathogens. Nevertheless, these mutualistic associations are not unique to previously invaded sites in the study area.