Silt Loam Research Articles

Simulation of Subsurface Drainage in the Sugarcane Crop under Different Spacing and Drain Depths

Agricultural land drainage is an instrument for growing production and a tool for the conservation of land resources. The performance of land drainage systems is thus critical for achieving sustainable agricultural production Recently, many types of software have been developed in this field for modeling and simulating the performance of these systems. SISDRENA is a simulation model of the performance of underground drainage systems. The main objectives of this paper are to simulate different combination of depths and spaces between drains and to analyze their impact on potential sugarcane productivity in the western plains of Venezuela using a land drainage system model. Therefore, three climatic scenarios were defined by annual precipitation: dry years (25% below average), normal (mean) and humid (75% above average). The scenarios were implemented in three different soil types: sandy loam, loam and silt loam, with a hydraulic conductivity of 0.19, 0.26 and 0.04 m day−1, respectively. The simulation of the yield related to soil deficit (YRD) and water stress (YRW) indicated that the highest yields were reached for the larger spacing between drains and the high conductivity hydraulic of soils. In relation to the average relative productivity (YT), it was shown that in soils with a greater water retention capacity there is an inversely proportional relationship between the spacing between drains and the productivity. We concluded that in order to reach the maximum sugarcane yield, the effect of hydraulic conductivity is more important than the changes in the precipitation pattern.

The synergistic effect of nitrogen and phosphorus starter fertilization sub-surface banded at sowing on the early vigor, grain yield and quality of maize

Maize grain yields and profitability are enhanced in temperate growing areas as a result of an early sowing. However, cool conditions may constrain the uptake of nitrogen (N) and phosphorus (P) by the root system during the early and more susceptible growth stages. The application of starter fertilizers near the plant roots could ensure better N and P availability and improve early vigor of the crop. The aim of this study has been to quantify the overall benefits of a localized starter fertilization with N or P, or their combination, on maize (early development, grain yield, grain quality and sanitary traits). A 4-year field experiment was conducted in NW Italy during the 2014–17 growing seasons. The trial compared the sub-surface placement of N, P and NP in bands close to the maize seed furrows, as a starter fertilization strategy, with unfertilized controls on sandy silt loam (SSL), silt loam (SL) and silty clay loam (SCL) soils. These soils were placed side by side, and were characterized by low, high and medium N and plant-available P contents, respectively. The results showed that when N and P were applied together, the early vigor (plant height) and canopy development (NDVI values) of the maize were significantly enhanced, compared to both the controls and to the application of the single elements in all the soils. The positive growth responses to starter NP fertilization were combined with accelerated crop phenological development, so that anthesis occurred 2.4–3.1 days earlier. Thus, the grain yield was enhanced following the NP sub-surface placement (+7%, +15% and +11%, in SSL, SL and SCL, respectively), mainly due to an increase in the number of kernels per ear (+10%), while the grain moisture content was reduced, compared to the controls, in all the soils (−2.2%). The application of N or P alone did not consistently affect either the grain yield or the moisture content in any of the three soils. The starter fertilization strategy also affected both the qualitative and sanitary grain traits. NP and N both resulted in an increase in the grain hardness in the SL and SCL soils, but when P was applied alone, no significant effects were observed. The use of NP starter fertilization significantly reduced the ear injuries caused by European Corn Borer in all three soils (−44%), and reduced ear rot severity in the SSL and SL soils and the fumonisin content (−72%) in the SL and SCL soils, compared to the untreated controls. The synergistic effect of N and P applied as a sub-surface band at sowing had a consistent positive effect on the advancement of the flowering dates at different sites in different years, even in soils that have tested high to P or N. Thus, the application of NP starter fertilizer is a crop practice that should be considered in North Italy and for similar soils and environments.

The Impact of Climate Change and Soil Classification on Benzene Concentration in Groundwater Due to Surface Spills of Hydraulic Fracturing Fluids

Hydraulic fracturing drilling technology can cause a high risk of surface spill accidents and thus water contamination. Climate change together with the high water demand and rapid increase in industrial and agricultural activities are valued reasons why we should all care about the availability of water resources and protect them from contamination. Hence, the purpose of this study is to estimate the risk associated with a site contaminated with benzene from oil spillage and its potential impact on groundwater. This study focused on investigating the impact of soil variability and water table depth on groundwater contamination. Temperature-dependent parameters, such as soil water content and the diffusion of pollutants, were considered as key input factors for the HYDRUS 1D numerical model to simulate benzene migration through three types of soil (loamy, sandy clay loam, and silt loam) and evaluate its concentration in the water aquifer. The results indicated that an anticipated increase in earth’s average surface temperature by 4 °C due to climate change could lead to a rise in the level of groundwater pollution in the study area by 0.017 mg/L in loamy soil, 0.00046 mg/L in sandy clay loam soil, and 0.00023 mg/L in silt loam soil. It was found that climate change can reduce the amount of benzene absorbed from 10 to 0.07% in loamy soil, 14 to 0.07% in sandy clay loam soil, and 60 to 53% in silt loam soil. The results showed that the soil properties and solute characteristics that depend on the temperature have a major and important role in determining the level of groundwater pollutants.

Effects of soil surface electrochemical properties on soil detachment regulated by soil types and plants

Soil surface electrochemical properties play an important role in soil detachment. However, the effects of soil surface electrochemical properties on soil detachment have received little attention. This study selected three typical soil types (sandy loam, silt loam and silt clay loam) and two typical herbaceous plants (Stipa bungeana Trin. and Artemisia gmelinii Web. ex Stechm., with an abandoned cropland) to quantify the effects of varied soil surface electrochemical properties caused by soil types and plants on soil detachment on the Loess Plateau, China. A hydraulic flume test was conducted under five flow discharges (0.1, 0.2, 0.3, 0.4 and 0.6 L s−1) on a 15° slope. The results showed that large differences in soil surface electrochemical properties occurred among different soil types and plant species. The exchangeable sodium percentage (ESP), cation exchange capacity (CEC), specific surface area (S), surface charge density (σ0), surface potential (φ0) and surface electric field strength (E0) ranged from 1.02% to 2.26%, from 7.26 to 24.34 cmolc kg−1, from 8.32 to 147.38 m2 g−1, from 0.09 to 2.02C m−2, from −81.33 to −149.92 mV and from 1.23 × 108 to 28.46 × 108 V m−1, respectively. The soil detachment capacity (Dc) was significantly correlated with ESP (P < 0.01), E0 (P < 0.01) and |φ0| (the absolute value) (P < 0.05). Moreover, Dc exponentially increased with |φ0| (R2 = 0.99) and linearly increased with ESP (R2 = 0.85) and E0 (R2 = 0.95). Therefore, soil surface electrochemical properties greatly varied with soil types and plants and had a significant effect on soil detachment.

Influence of living grass Roots and endophytic fungal hyphae on soil hydraulic properties

Soil hydraulic properties are often estimated based on laboratory data or pedotransfer functions dependent on soil physical properties, which often do not consider potential impacts of soil roots or fungal hyphae. Here, we first review current knowledge of how these soil biotic components affect hydraulic properties, then we conducted laboratory experiments to specifically test if the presence of roots and mycorrhizal fungi had a significant effect on the hydraulic properties of two soils with contrasting textures: Flint sand and Hamblen silt loam. Soil cores were seeded with (Panicum virgatum) and grown in a greenhouse over three separate growth periods. The endophytic fungus Serendipita indica was injected as liquid inoculant into designated mycorrhizal cores. Saturated hydraulic conductivity (Ksat) measurements were made with a constant head permeameter, and soil water retention curves were obtained by the evaporation method, supplemented at the dry end for Hamblen silt loam with water activity meter data. Retention curve parameters were obtained by fitting the van Genuchten equation to the resulting measurements. Mean root volume ratios were higher in the mycorrhizal inoculated treatment than in the uninoculated treatment for both soils. For Flint sand, analysis of variance revealed that Ksat was reduced by the presence of roots as compared to bare soil. This was likely due to roots clogging soil pores. Results also indicated the presence of roots changed the shape of the water retention curve for Flint sand by increasing water content at saturation and by reducing the slope of the curve. These changes suggested roots created additional porosity and broadened the pore-size distribution. The presence of mycorrhizal fungi accentuated the root effects. The influence of roots and mycorrhizal fungi on hydraulic properties was less obvious for the Hamblen silt loam, as none of the treatments differed from each other at p < 0.05. The results highlight the necessity to consider the impact of root and fungal structures on models of soil hydraulic properties.

Wetting and drainage cycles in two New Zealand soil types: Effects on relative gas diffusivity and N2O emissions

Nitrous oxide (N2O) is a potent greenhouse gas generated in agricultural soils by microbial processes that vary according to soil redox. Soil oxygen (O2) supply and demand strongly influence soil redox. Migration of O2 into the soil primarily occurs via gas diffusion, expressed as relative gas diffusivity (Dp/Do), and is influenced by soil structure (air-filled porosity and tortuosity of pores) and soil water content. Soil N2O emissions have been shown to increase at low values of Dp/Do but detailed studies examining the relationship between Dp/Do and soil N2O emissions remain limited, with relatively few soil types examined, and no studies of repeated wetting-drainage cycles. Thus, the objectives of this study were to examine how successive wetting-drainage cycles affected both Dp/Do dynamics and associated N2O emissions in two New Zealand soils; a pallic silt loam and an allophanic loam, with the latter also having a higher organic matter content. Soil cores, repacked to varying density, were wetted up with 15N enriched NO3− solution and placed on tension tables where they underwent two consecutive 12-day wetting-drainage cycles from saturation to field capacity (0 to −10 kPa). Over time measurements were made of N2O, N2, inorganic-N and soluble carbon, while Dp/Do was modelled using soil physical characteristics. For both soils each wetting-drainage cycle induced N2O fluxes but with 5-fold lower fluxes in the allophanic soil. Greater aggregation and sand content in the allophanic soil generated higher porosity and Dp/Do values that were almost always greater than recognized anaerobic limits. Thus, wetting-induced N2O fluxes observed in the allophanic soil during early drainage were concluded to result from anaerobic or hypoxic pathways of N2O production potentially within the intra-aggregate zone. While wetting-drainage events induce N2O emissions by altering Dp/Do and the soil aeration status, the draining of soils, especially soils high in organic matter, may enhance O2 demand generating anaerobic zones conducive to denitrification. Further detailed studies examining the interaction between soil structure and soil organic matter content and their effect on N2O emissions under wetting-drainage events, with measures of soil O2, are needed.

Morphogenesis, physico-chemical properties, mineralogical composition and nature of parent materials of some alluvial soils of the Lower Niger River plain, Nigeria

Nine pedons of alluvial origin in the Lower Niger River floodplains of Nigeria were examined for morphogenesis, physicochemical properties, mineralogical composition, and heterogeneity of the parent materials. The soils were stratified with redoximorphic features observed in the different layers reaching A-horizon with subsurface grayization. Soils that received annual alluvial enrichment were found to be structurally weak while others were moderately strong. Soil characteristics showed varying degrees of heterogeneity with source of parent materials and degrees of hydromorphism, moulding morphogenesis and gleization as major soil-forming processes. Silt loam was the predominant soil texture except ELM3 and TFN3 dominated by sandy loam and loamy sand textures. Soils were strongly acid to neutral [pH (H2O), 4.94 – 7.00], having very low to medium organic matter (0.13 – 4.02 %), and low to very high K (0.10 – 2.13 cmol/kg). Quartz dominated the identified mineral phases followed by kaolinite, indicating the dominance of low activity clays and low ferromagnesian minerals presence. The presence of several K-bearing minerals in the pedons (micas and feldspars) suggest that the K pool could naturally be replenished. Textural diversity between the different SMUs is ascribed to different sources of the water-borne sediments and the flow rate of the floodwater at the time of deposition of the parent materials. Organic carbon distribution patterns indicated stratification and heterogeneity of parent materials. Wetness, flooding, and soil chemical and physical fertility were major constraints to increased and sustainable crop production in the Lower Niger River floodplain soils.

Digital Technologies Determination Effectiveness for the Productivity of Organic Winter Wheat Production in Low Soil Performance Indicator

The most important aspect of precision farming is the prediction of crop yield and quality. Digital technologies (soil maps and combine harvester with telemetry functions) were used to determinate the yield of organically grown winter wheat (variety Skagen) in two fields of 18.8 and 4.5 ha in Lithuanian regional conditions, in an area classified as low-performance for farming. The objective of the research was to determine the effectiveness of digital technologies (soil maps and combine harvester with telemetry functions) in assessment of the dynamics of soil pH, P2O5, and K2O, humus and organic winter wheat (variety Skagen) productivity, and grain crude-protein dependence in low-performance soils. Haplic Luvisol soils predominated, while Eutric Gleysols, Haplic Arenosols, and Eutric Planosols soils intervened in smaller areas, and the granulometric composition of the soil in the arable layer and the subsoil varied from sand to sandy loam, loam, and silt loam. In the sandy areas of Haplic Arenosols and in the lower parts of the field, where Eutric Gleysols, intervened in predominant Haplic Luvisols soils, winter wheat crude protein content and grain yield were lower. The biggest grain yield of 6.95 t ha−1 was obtained in Haplic Luvisols soils. Crude protein of winter wheat grains varied from 9.70 to 13.34%. Although both technologies reflected the non-uniform yields of the fields and correlation between them well, the information on the soil cover of the field better explained the reasons for lower yields. In the case of this research, sand inclusions and lower areas in winter wheat fields, causing plants to soak during winter, were identified. The combination of two digital technologies (soil maps and combine harvester with telemetry functions) made it possible to determine yields accurately, and quickly. Moreover, there is a need, in the future, to evaluate the reasons for yield variation and address changes in yields due to the improvement of certain low-performance soil areas. The complex use of these technologies can be beneficial in terms of labour and economy. However, the accurate benefit of labour time and economic should be investigated.

Different contributions of ammonia oxidizing archaea and bacteria to nitrification in soils amended with equivalent amounts of either ammonium-N or organic-N

Although considerable knowledge exists on the impact of crop residues on soil N availability, information about their impact on nitrification specifically is lacking. The unique physiologies of ammonia oxidizing archaea (AOA) suggests their activities might respond differently to crop residue amendment compared to ammonia oxidizing bacteria (AOB). An incubation study was conducted on two widely distributed Oregon agricultural silt loam soils of the Walla Walla (WW) and Woodburn (CC) series, amended with a fertilizer rate of 70 μg N g−1 soil in the form of (1) NH4+-N, (2) clover stems (C:N ~ 25), or (3) clover leaves (C:N ~ 13). NH4+ accumulation in the presence of acetylene, and the relative amounts of AOA and AOB activities, in the presence of the selective AOB inhibitor, 1-octyne, were examined over a 28-31d incubation. Nitrifying activity in the crop residue-amended WW soil matched the rate of ammonification and was predominately octyne-resistant suggesting that nitrifying activity was dominated by AOA. In CC soil, the relative contributions of AOA and AOB to emergent activities was influenced by the nature of the residue and in a soil specific manner. In leaf amended CC soil, AOB contributed the majority of initial nitrifying activity over 0-7d, with the contribution of AOA activity increasing post 7d to represent 100% of the total rate. In stem amended CC soil, emergence of nitrifying and ammonifying activities were delayed, but after 7d incubation AOA activity emerged at a rate greater than the accompanying rate of ammonification. In NH4+-N amended soils, AOB activity emerged quickly at rates greater than when N was supplied by residues. The response of AOA activity to NH4+-N was soil specific being immediate and at a greater rate than leaf residue supported activity in WW soil, whereas in CC soil, AOA activity was temporally delayed (as with residue treatment) and emerged at a rate similar to that supported by leaf residue. From a practical perspective, the findings of this study show that an application of 70 μg N g−1 soil as crop residues can prevent AOB driven nitrifying activity from reaching its potential compared to an inorganic NH4+-N application, and also suggest the potential of AOA activity to be modified by residues in a soil specific manner.

Effects of aerated subsurface drip irrigation on rhizosphere soil environment and pepper (Capsicum annum L.) growth in three soil types

ABSTRACT Aerated subsurface drip irrigation (ASDI) has been considered an effective method to unlock the growth potential of crops. An experiment was undertaken to monitor the effects of three aeration rates (40% aeration rate, 15% aeration rate, CK: no-aeration) on rhizosphere soil environment and growth parameters of pepper in three soil types (YC: yellow clay, SL: silt loam, HL: heavy loam). ASDI significantly increased the soil enzyme and microbial abundance, and enhanced the soil respiration compared to the control. ASDI significantly increased the pepper yield, fruit quality, and biomass of stem and leaf. The 40% aeration rate was more beneficial to these parameters than that of 15% aeration rate in YC and SL, whereas, in HL, the 40% was less effective than 15% aeration rate. Soil type significantly affected pepper rhizosphere soil environment and the yield, quality, and biomass of stem and leaf. The benefits of ASDI in YC were better than those in SL and HL. However, aeration rate and soil type had no significant effects on the fresh/dry weight of pepper root. The recommended ASDI patterns for pepper in YC and SL were 40% aeration rates, while in HL it was the 15% aeration rate.

Importance of accessory minerals for the vertical distribution of uranium and thorium in soil profiles: A case study of durbachite from the Třebíč Pluton (Czech Republic)

The mineralogical character of a parent rock strongly affects the uranium (U) and thorium (Th) contents of soils. We have selected five representative soil profiles developed on amphibole–biotite to biotite durbachites in the Třebíč Pluton (eastern part of the Czech Republic) to characterize the radioactivity and variable-intensity weathering. The Endoskeletic Cambisols with a silt loam to loamy sand texture and a well-developed subsurface Bw horizon represented the most common product of the pedogenetic processes on durbachites. All studied soil profiles showed the evidence of pedogenetic alteration with intrasoil weathering. They were moderately deep (70–80 cm) with high rock-fragment concentrations within the B and C horizons. The predominant grain size fractions were silt (12% to 83%) or sand (8% to 87%), and the percentage of clay was up to 15%. A feldspar–quartz–vermiculite (biotite)–amphibole–kaolinite–Fe–Mn (oxy) hydroxide assemblage was typical for the most weathered parts of the profiles. Variation in the U and Th contents within the studied soil profiles resulted predominantly from the changes in the amounts of primary accessory minerals at different depth levels. Uraninite, monazite, thorite, allanite, zircon, thorogummite, REE-(Rare Earth Elements) fluorocarbonates, and minerals of the rhabdophane group were the main carriers of radioactive elements in the parent durbachite and overlying soil profiles. The gamma-ray spectrometry, geochemical and mineralogical analyses show that uraninite was stable only in the parent durbachite and disappeared at the rocks–C horizon interface. This process was followed by the gradual alteration of allanites, thorites, brabantites and secondary U- and Th-rich minerals (e.g., thorogummite, bastnäsite) toward the soil surface.

Estimating particle-size distribution from limited soil texture data: Introducing two new methods

Most soil databases present the mass fractions of sand, silt, and clay particles without detailed primary particle-size distribution (PSD). In the present paper two simple methods are introduced to estimate the PSD using the fractions of sand, silt, clay, and very coarse sand. A total of 504 soil samples with different texture classes from different regions, i.e., southern Iran (245), south-eastern Brazil (116), and UNSODA database (143) were used. PSD of the Iranian and Brazilian soil samples were determined using a combination of wet-sieving and sedimentation (hydrometer for Iranian and pipette for Brazilian soils) approaches and that of the others extracted from UNSODA database. We developed two new methods including very coarse sand-dependent (VCS-D) and very coarse sand-independent (VCS–I) to predict PSD of the soils. PSD were also predicted using the revised Skaggs method (R-Skaggs) and compared with the measured ones. Both VCS-D and VCS-I approaches with very simple equations accurately estimated full range of PSD in a wide range of the fine to medium textured soils)clay, clay loam, loam, silty clay, silty clay loam, silt loam, and silt texture classes). Accuracy of predictions was slightly lower in coarse textured soils (sandy clay, sandy clay loam, sandy loam, loamy sand, and sand textures) than that of the other texture classes. For these coarse textured soils, it is strongly recommended that the fraction of particles between 0.05 and 2 mm diameters be estimated using the VCS-D or VCS-I methods and the fraction of particles between 0.002 and 0.05 mm diameters be estimated using the R-Skaggs method. The R-Skaggs method could only predict the PSD in the soils with nearly 25–60% sand content, accurately. Whereas, the new proposed methods could predict full range of PSD with high accuracy (NRMSE <10%) in soils with sand content less than 53%. Overall, the proposed methods could accurately predict full range of PSD curve by using only the content of primary soil particles in nearly 73% of soil classes in texture triangle. • New methods (VCS-D and VCS-I) proposed to estimate particle-size distribution (PSD). • The methods are very simple and accurate to estimate PSD from limited texture data. • The methods are very accurate to estimate PSD in 73% of soil texture triangle. • The methods excellently estimate PSD in fine and medium textured soils. • The methods were more accurate than R-Skaggs in fine and medium textured soils.

An assessment of potential pesticide transmission, considering the combined impact of soil texture and pesticide properties: A meta-analysis.

Pesticides are widely employed as a cost‐effective means of reducing the impacts of undesirable plants and animals. The aim of this paper is to develop a risk ranking of transmission of key pesticides through soil to waterways, taking into account physico‐chemical properties of the pesticides (soil half‐life and water solubility), soil permeability, and the relationship between adsorption of pesticides and soil texture. This may be used as a screening tool for land managers, as it allows assessment of the potential transmission risks associated with the use of specified pesticides across a spectrum of soil textures. The twenty‐eight pesticides examined were differentiated into three groups: herbicides, fungicides and insecticides. The highest risk of pesticide transmission through soils to waterways is associated with soils containing <20% clay or >45% sand. In a small number of cases, the resulting transmission risk is not influenced by soil texture alone. For example, for Phenmedipham, the transmission risk is higher for clay soils than for silt loam. The data generated in this paper may also be used in the identification of critical area sources, which have a high likelihood of pesticide transmission to waterways. Furthermore, they have the potential to be applied to GIS mapping, where the potential transmission risk values of the pesticides can be layered directly onto various soil textures.

Sensitivity of infiltration modelling to temporal resolution of rainfall data

AbstractThe sensitivity of infiltration predictions by Hydrus‐1D and Green‐Ampt models to rainfall discretisation was investigated by assessing the accuracy of infiltration predictions with rainfall rate profiles at step sizes D between 2 and 1440 min. Five peak rainfall profiles and one sine‐wave rainfall profile, all with a cumulative rainfall amount of 28.8 cm and a duration of 24 h were used. Discrete rainfall profiles were generated based on the peak rainfall profiles for several step sizes. The rainfall profiles were evaluated in a sandy loam with a high saturated hydraulic conductivity and a silt loam with a low saturated hydraulic conductivity for two initial pressure heads. For both models, insensitivity was found below a critical step size Dcrit, whereas high sensitivity was observed above it, Dcrit depending on soil hydraulic conductivity and rainfall peak intensity, regardless of initial pressure head. In the sandy loam, Dcrit was 20–30 (high‐intensity peak) and 70 min (low‐intensity peak); in the silt loam, values were 100 and 200–300 min, respectively. Therefore, rainfall data from common weather station data at D = 60 min allow accurate estimates of infiltration only in low‐conductivity soils or for low‐intensity rainfall. The disaggregation of daily cumulative rainfall into sine‐wave profiles improved predictions in more conductive soils. Results indicate that higher saturated hydraulic conductivity and intensity peak rainfall rate require smaller values of D for the accurate modelling of infiltration with Hydrus‐1D and Green‐Ampt models.Highlights Temporal resolution of rainfall data is important in infiltration modelling. Temporal resolution of rainfall data affects Green‐Ampt and Hydrus‐1D predicted infiltration Green‐Ampt and Hydrus‐1D cumulative infiltration predictions are insensitive for rainfall resolution ≤20 min Predictions are more sensitive to rainfall resolution &gt;20 min in soils with higher hydraulic conductivity.

Time dependence of hydraulic parameters estimation from transient analysis of mini disc infiltrometer measurements

AbstractThe transient analysis of mini disc infiltrometer (MDI) measurements is an established method for characterising near‐surface hydraulic characteristics of soils. The reliability of hydraulic characteristics obtained from transient analysis depends on the (1) adequacy of model, (2) adequacy of data, (3) measurement time and (4) measurement footprint. The measurement time dependence recommendations are reported only for a few soil textures, initially wet samples and tension infiltrometer (TI) with a higher measurement footprint than the MDI. This study investigated the adequacy of infiltration data (using cumulative linearization [CL] and differentiated linearization [DL]) and measurement time influence on the hydraulic parameters determined from the transient analysis of MDI measurements for six soil textures. The objective of the study is to identify suitable MDI measurement durations for different soil textures for the initially dry state, considering both adequacy of data and time fractionation (measurement time influence). The data adequacy time obtained from the DL (TDL) was found to be 0.8 times less than the value obtained from CL (TCL). The marginal difference in TDL and TCL had a significant influence on the determination of infiltration equation coefficient C1 and negligible influence on coefficient C2. The time fractionation procedure adopted for identifying adequate MDI measurement time (Tm) was found to be comparable based on sorptivity (S0) and hydraulic conductivity (K0). The average Tm was also comparable with TDL and TCL with a strong positive correlation. The C2 values obtained based on Tm, TDL, and TCL were in better agreement than the corresponding C1 values. The adequate MDI measurement times identified by considering Tm, TDL, and TCL were texture dependent, ranging from 45 min for silt to 120 min for silt loam and silty clay loam. For loamy sand, it was 50 min; for sand, it was 70 min, followed by 60 min for loam.

Changes on Phosphorus Functional Fractions of Two Louisiana Alluvial Soils Grown with Corn at Different Phosphorus Rates

ABSTRACT Soils in Mississippi River alluvial plains is one of the distinct soil areas in Louisiana under corn (Zea mays) production. This study was conducted to evaluate the changes on Mehlich-3 extractable-phosphorus (P) and P-functional fractions of two Louisiana alluvial soils i.e., Commerce silt loam (Commerce sl) and Perry clay (Perry cl). Potted air-dried soils were mixed with different P rates (0, 34, 67, 101 and 134 kg P2O5 ha−1) and planted with corn seeds. Soil samples were collected 30 days after P application (30 DAP) and at harvest of corn. The Commerce sl and Perry cl differed considerably in the distribution of different P fractions. The unutilized P fertilizer was transformed into calcium (Ca)-P for Commerce sl while it transformed into iron (Fe)-P and reductant-P for Perry cl. Overall, the labile- and aluminum (Al)-P fractions before planting increased with increasing P rate while Fe-P with P rates increased only at harvest for both soils. With time across P rates, both soils built-up less readily available reductant-P. In terms of soil total P, residual-P and total inorganic P (Pi) components, Commerce sl and Perry cl soils differed significantly (P < .05) at 30 DAP and at harvest. On the other hand, the total P and residual-P were not affected by P rates at 30 DAP and at harvest for both soils. Phosphorus fertilization depending on soil properties, can promote certain P fractions in the soil wherein the contribution to corn P nutrition would likely have to come from the readily available P fractions.

Changes in microbial biomass and activity support ecological intensification of marginal land through cultivation of perennial wheat in organic agriculture

ABSTRACT Ecological intensification of agroecosystems on marginal land through cultivation of perennial wheat may provide greater belowground biomass than cultivation of annual wheat, and thus improve soil organic carbon (SOC) and consequently benefit soil microbial activity. However, little is known about how organically managed hybridised perennial wheat (Triticum aestivum L. × Thinopyrum spp.) stimulates SOC, microbial biomass and activity in marginal soils. Therefore, the effect of three organically managed cropping systems: i) sole perennial wheat; ii) perennial wheat with clover intercrop; and iii) annual wheat; were investigated at three sites in Germany on marginal soils with different textures (silt loam (SL) with impervious soil layer, clay loam (CL) with 30–35% stone content and sandy soil (SS) with low nutrient content). Soil samples, from each cropping system and site, were taken from A- and B-horizons after 3 years of cultivation and were evaluated for SOC, microbial biomass C and N (MBC, MBN), basal respiration, and C-enzyme activities. In CL and SS soils, perennial wheat with clover intercrop increased SOC in the A-horizon compared with annual wheat and sole perennial wheat. Varied effects were observed in the B-horizon, with sole perennial wheat in CL having higher SOC and MBC than the other two cropping systems. SOC storage stock in the B-horizon of perennial wheat was on average 18% higher relative to annual wheat, revealing a considerable C storage potential. Overall, the study showed that perennial wheat cultivation can improve microbial biomass and activity in marginal soils compared with cultivation of annual wheat.

Investigation of the mechanical behavior of salinized agricultural soils using unsaturated triaxial tests and a constitutive framework

The salinization of agricultural soil is a common issue of concern. However, the coupling relationship between soil chemical properties and mechanical behavior has been largely ignored. A constant water content triaxial test was conducted by controlling suction on unsaturated agricultural soils collected from paddy fields. The soil samples were diluted with different salt solutions (a distilled water, a sodium chloride (NaCl) solution and a calcium chloride (CaCl2) solution) to investigate the influence of salinity on the mechanical behavior of soils. The pore water pressure of silt loam was significantly influenced by the pore water salinity, while the pore water pressure of silty clay was significantly influenced by the net normal stress. The results showed that the salt type and concentration significantly affected the cohesion value of silt loam. An empirical constitutive model that incorporated osmotic suction was presented in this paper to explain and quantify the effect of pore water salinity on the shear strength of silt loam. Osmotic suction was considered an independent stress variable in the constitutive model, unlike the salt type and concentration. The Barcelona unsaturated constitutive model explained how the pore water salinity affected the mechanical behavior of agricultural silt loam. With an increase in the osmotic suction in silt loam, the yield surface expanded to both sides of the original ellipses, resulting in an increase in cohesion. The constitutive framework considering osmotic suction provides an improved prediction of the mechanical behavior of agricultural soil under natural conditions subjected to salinization/desalinization. This framework can be implemented in a stabilization plan when the soil and salt are involved in agricultural activities.

Profitability of twin‐row planting and skip‐row irrigation in a humid climate

AbstractWe assessed the potential profitability of twin‐row (TR) planting geometry as a water productivity‐enhancing practice and of skip‐row irrigation (SRI) as a water‐conserving practice in furrow‐irrigated cotton (Gossypium hirsutum L.) and soybean (Glycine max L.). Data from agronomic experiments carried on Dundee silt loam soils indicate that, on average, TR planting increases profitability by US$344 ha−1 for all‐row irrigated (ARI), $401 ha−1 for SRI, and $334 ha−1 for rainfed (RF) cotton. For soybean, the gains were $178 ha−1 for ARI irrigated, $178 ha−1 for SRI, and $121 ha−1 for RF. Converting from ARI to SRI irrigation can conserve 88 mm of irrigation water on average for cotton and 91 mm of irrigation water on average for soybean, while improving cotton profits by $55–113 ha−1. Soybean growers can expect a reduction in profits from SRI of ∼$11 ha−1. Incentive payment for soybean growers of ∼$0.132 mm−1 of saved water would compensate farmers for the expected losses of adopting SRI in the Delta of Mississippi.

Lignite derived humic products and cattle manure biochar are effective soil amendments in cadmium contaminated and uncontaminated soils

Cadmium (Cd) contamination in soils is a global environmental concern. Amending soil with low cost carbonaceous materials, such as humic substances and biochars, may provide cost effective and environmentally sound alternatives to traditional remediation technologies. Two lignite derived humic substance products, nano humus and humic powder, and a cattle manure biochar, were used as amendments in loamy sand and silt loam soils to ascertain their impact on Cd, with barley (Hordeum vulgare L.) as the response organism in a greenhouse experiment. Soil Cd had the greatest influence on barley shoot biomass, decreasing by 28% in silt loam and 37% in loamy sand relative to the control. With or without Cd addition, the beneficial effect of nano humus and humic powder were pronounced. Nano humus and humic powder (high rate), increased root biomass by 248 and 100% in uncontaminated soils, respectively; and increased by 186 and 55% in Cd contaminated soils. Biochar increased shoot biomass in soils by 32% without Cd, and 127% with Cd. Barley responded differently to amendments in two textured soils. Results of this research will help develop cost effective remediation techniques using humic materials and cattle manure biochar as soil amendments in Cd contaminated soils.