Silt Loam Soil Research Articles

Nutrient Leaching Losses from Continuous Application of Washed Rice Water on Three Contrasting Soil Textures

Washed rice water (WRW) is often used as liquid plant fertilizer. However, there is no study on nutrient leaching of soils due to frequent WRW application. Therefore, a column study was undertaken to evaluate the rate of nutrient leaching losses, nutrient retention, and recovery of elements in leachates of three different soil textures irrigated with WRW. The treatments were 3 soil textures and 2 water types. The treatments were evaluated for 8 weeks, and the soils and leachates were measured biweekly. Factorial and repeated measurements in a completely randomized design were therefore employed. Higher cumulative leaching of the elements was found in sandy clay loam soil with 666.29, 378.13, 138.51, 50.82, 44.61, and 27.30 mg L-1 of K, P, Mg, Ca, NH4+-N, and NO3--N, respectively. Higher percentages of elements recovery in leachate were found in the sandy clay loam soil with a range of increase by 37.8–283.1% than the other two soil textures. In contrast, after 8 weeks of WRW application, the clay and silt loam soils had a range of increase in nutrient retention by 0.43–1358.5% than the sandy clay loam, with P and NO3--N being the highest and the lowest elements retained, respectively, for all soil textures. This study showed that frequent WRW disposal on sandy textured soils risks higher environmental contamination, mainly due to the soil’s lower water retention and nutrients, leading to nutrient leaching. Therefore, organic amendments should be added to sandy textured soils.

Empirical approach for developing production environment soil health benchmarks

Defining quantitative soil health benchmarks can support efforts to improve soil quality and meet broader ecosystem services goals, while simultaneously helping field-level benchmarking of soil health on farms. However, soil health metrics in agricultural systems require edaphic context, notably climate, soil texture and classification, as well as cropping system information for optimal interpretation. Soil samples (n = 1328) from New York State (USA) with Land Resource Regions (LRR), texture, and cropping system information were analyzed for eight physical and biological soil health indicators (i.e., soil organic matter, permanganate-oxidizable carbon, respiration, protein, available water capacity, wet aggregate stability from 0 to 15 cm depth, and penetration resistance from 0 to 15 and 15–45 cm), from which population distribution functions were determined. Production environment soil health (PESH) benchmarks were derived as potential management goals for four soil texture groups and six cropping systems by proposing the 75th and 90th percentile for each factorial class. Finer-textured (sand content <50%) soils and Pasture and Mixed Vegetable cropping systems generally had the highest values for soil health benchmarks, followed by Dairy Crop and Orchard systems, then Annual Grain, and lastly Processing Vegetable systems. Soil organic matter PESH benchmarks for silt loam soils, defined by the 75th percentile, ranged from 4.2% (Annual Grain and Processing Vegetable) to 5.9% (Pasture). Long Island (LRR-S) had soil organic matter PESH benchmarks that were, on average, 0.7% numerically lower than the rest of New York State (LRRs-L&R). This implies that regional PESH benchmarks within a state or region may be warranted if edaphic context is considerably different.

Root exudation of organic acid anions and recruitment of beneficial actinobacteria facilitate phosphorus uptake by maize in compacted silt loam soil

Soil compaction restricts root growth and plant nutrient uptake, but the effects on the abundance and diversity of soil microbiome are poorly understood. A field study with maize (Zea mays L.) was conducted with two soil-compaction treatments (NC: non-compacted; C: compacted) to investigate the interactions of root exudates and microorganisms and the effect on P uptake at two growth stages (seedling and flowering). At the seedling stage, shoot P concentration was decreased by 13.7% in the C treatment compared with the NC. Root growth and arbuscular mycorrhizal fungi colonization were reduced probably due to the decreased soil porosity after compaction. However, root organic acid anions (OAAs) levels were increased by 170%. Several genera of actinobacteria were specifically enriched in the rhizosphere and their abundance was significantly correlated with the concentration of OAAs. However, the positive correlations of concentration of OAAs and abundance of microorganisms or plant P uptake were not observed at flowering stage. Our results indicated that besides the well-known function of exuded organic acid anions on soil P mobilization, maize might also select for microorganisms associated with the facilitation of P acquisition, and mitigating P deficiency at the early growth stage of the plant in compacted soil.

Fate of enteric bacteria and viruses in silt loam soil amended with biofertilizers made from human feces and urine for crop production

Human excreta can be used as biofertilizers due to their nutrient and organic matter content. Nevertheless, the behavior of microorganisms should be investigated, as enteric pathogens can accumulate in the soil. Therefore, we evaluated the survival and transport of two enteric bacteria (E. coli and Salmonella enterica) and two enteric virus surrogates (MS2 and ΦX-174 bacteriophages) when applied as contaminants of four biofertilizers on Lactuca sativa production. The study was carried out in lysimeters outdoors with repacked silt loam soil, using a randomized block design (RBD) with six treatments and three replicates. Biofertilizers were urea-treated feces, feces composted with organic waste, stored liquid urine, and struvite and were inoculated at 106–107 cfu/pfu g−1 of E. coli and bacteriophages strains and 107–109 of S. enterica. Soil amended with composted feces exhibited the lowest decimal reductions (T90) for the microorganisms evaluated, with 10.2 days for E. coli, 11.9 days for S. enterica, 22.2 days for MS2, and 3.7 days for ΦX-174. Urea-treated feces temporarily hindered the growth and survival of E. coli and S. enterica in the soil. However, both bacteria were present after one month, while MS2 showed a stable concentration with this biofertilizer. E. coli presented a stable behavior when applied with urine, whereas MS2 was stable with urea-treated feces, urine, and struvite. ΦX-174 and S. enterica were not considered good representatives of most resistant enteric pathogens’ behavior in the soil during food production since they were not detected in leachate and showed a rapid die-off in soil. E. coli leached faster and in higher concentrations than MS2, which presented higher concentrations in deeper soil layers, from 10 to 20 cm. Therefore, using urine, struvite, and urea-treated faces implied a higher chance of infection, as a decimal reduction time was not observed during the 36 days of the experiment. As a result, in short-term cultures, it is recommended that additional hygiene barriers are taken to avoid infection since E. coli and MS2 were still detected at the end of the experiment. An interval of 90 days between fertilizing and harvesting is recommended to prevent pathogen infection. These results are the basis for a quantitative risk assessment of human excreta-based biofertilizers for food production.

Winter Survival, Yield and Yield Components of Alfalfa as Affected by Phosphorus Supply in Two Alkaline Soils

Alfalfa (Medicago sativa L.) is an important forage for the development of herbivorous animal husbandry, which is widely planted in the cold climate areas of northern China, where there is low overwintering and forage yield in production, and fertilization is a vital production strategy. A field study was conducted to determine the response of alfalfa’s winter survival rate, yield, and yield components to different gradients of phosphate (P) fertilizer (0, 45, 90, and 135 kg P2O5 ha−1) in two types of low-phosphorus alkaline soils. The results show that the winter survival rates and forage yield increased at first and then decreased with the increase of P application; the greater winter survival rates were achieved at 45~90 kg ha−1 of P fertilizer applied, while the greater forage yield were achieved at 90 kg ha−1 in the two sites, and the suitable P fertilizer application rates for greater winter survival were less than those for greater forage yield; plant height and shoot mass made a greater contribution to forage yield than other yield components. To pursue greater forage yield, the suitable P fertilization rates for aeolian sandy soil and silt loam soil are 108.1 and 78.3 kg ha−1, respectively, based on the regression equations. Therefore, in cold winter and soil P deficiency areas, applying P fertilizer can be used as an effective strategy to improve alfalfa’s forage yield and persistence, and the most appropriate amount of fertilizer should be determined according to climate and soil conditions.

Molecular Detection of Cyclospora cayetanensis in Two Main Types of Farm Soil Using Real-Time PCR Assays and Method Modification for Commercial Potting Mix.

Cyclospora cayetanensis is a foodborne protozoan parasite that causes outbreaks of diarrheal illness (cyclosporiasis) with clear seasonality worldwide. In the environment, C. cayetanensis oocysts are very robust, and contact with contaminated soil may serve as an important vehicle in the transmission of this organism, and it is considered a risk factor for this infection. The present study evaluated a flotation concentration method, previously shown to provide the best detection results when compared with DNA isolation directly from soil samples, in two main types of farm soil, silt loam soil and sandy clay loam, as well as in commercial potting mix samples inoculated with different numbers of C. cayetanensis oocysts. The flotation method was able to detect as few as 10 oocysts in 10 g of either type of farm soil without modifications, but needed an extra wash and samples of reduced size for the processing of the commercial potting mix to be able to detect 20 oocysts/5 g. A recently modified real-time PCR method for the detection of C. cayetanensis based on a mitochondrial gene target was also evaluated using selected samples of each type of soil. This comparative study confirmed that the concentration of oocysts in soil samples by flotation in high-density sucrose solutions is a sensitive method that can detect low numbers of oocysts in different types of soil.

The Effect of Biochar Applied Alone and in Combination with Mineral and Organic Fertilisers on the Yield of White Cabbage and Soil Properties

The study aimed to investigate the effectiveness of biochar application on fertile soils in a temperate climate during the first year of application. The field trial was conducted on a nutrient-rich silt loam soil at two experimental sites in north-eastern Slovenia (Biš and Skorba). The effect of biochar applied alone or in combination with compost or mineral fertiliser on soil properties and yield of white cabbage was studied. In addition to the control (C), the soil received five treatments including biochar (B; 1.5 t/ha), compost (CO; 1.5 t/ha), biochar-mixed compost (BCO; 3.0 t/ha), standard mineral fertilisers (NPK; NPK 0.35 t/ha, potassium sulphate 0.25 t/ha and calcium ammonium nitrate 0.25 t/ha) and combined application of half the amountof NPK and BCO (NPK+BCO). The results showed that the applied treatments had no significant influence on the measured soil chemical parameters, except for the amount of total organic carbon, electrical conductivity and pH in Biš and total carbon in Skorba. All investigated parameters (cabbage head weight, head circumference, total and market yield) were higher at the experimental site Skorba. Statistically significant differences were found only at the experimental site Biš, where the treatment influenced all parameters (p &lt; 0.01), except for the head circumference of the cabbage. The NPK and NPK+BCO treatments produced significantly higher total yields (66.7 t/ha and 65.8 t/ha, respectively) and marketable yields (53.2 t/ha and 51.8 t/ha, respectively) compared to the other treatments (41.3-52.6 t/ha and 30.5-42.4 t/ha, respectively). Although the differences between the other treatments were insignificant, a trend of decreasing cabbage yields towards CO &gt; BCO &gt; B was observed. Similar results were also obtained when analysing the average data of the two experimental sites.

Nematodes require space: The relationship between nematode community assemblage and soil carbon across varying aggregate fractions

Soil aggregates are critical for soil carbon (C) sequestration and serve as a habitat for microorganisms, including free-living nematodes. Yet, the interactions between nematode community composition and soil C cycling across aggregate fractions is rarely assessed. The objectives of this study were to 1) determine how soil type alters nematode community dispersal across aggregate fractions, 2) understand how soil type may alter the relationship between nematode communities and labile C pools, and 3) assess the impact that tillage intensity has on nematode community assemblage across aggregate fractions. Soil cores were taken at two identical long-term trials located in Ohio (silt loam vs. clay). Each trial compared two different tillage intensities (chisel till vs. no-till). Soils were fractionated into three aggregate fractions (>2000 μm, 2000–250 μm, and <250 μm). For each fraction, nematode communities were identified to feeding group and permanganate oxidizable carbon (POXC) was measured. Results indicated that silt loam soils had greater bacterivore nematodes in the >250 μm aggregate fraction (p < 0.05) and relatively lower predator-omnivore nematode proportions when compared to clay soils. Tillage did not have a significant effect on nematode feeding groups. Correlation analyses revealed that predator-omnivore nematodes and POXC were positively correlated in clay soils, but only in the largest aggregate fraction (p < 0.05). Bacterivore nematodes were positively correlated with POXC in clay soils but negatively correlated in silt loam soils (p < 0.05). These findings reveal that predator-prey dynamics likely drive soil C accumulation in larger sized aggregates. Moreover, shifts in nematode community composition by soil type demonstrates how inherent properties influence soil food web structure and ultimately, soil C cycling.

Comparison of Bray‐1 and Mehlich‐3 extraction of P and K in Wisconsin silt loam soils

AbstractPhosphorous (P) and potassium (K) fertilizer rate recommendations are based on soil nutrient concentrations, which can be measured using a variety of lab methods. In Wisconsin, Bray‐1 extractant is used to measure soil test P (STP) and soil test K (STK), while most neighboring states measure STP and STK using Mehlich‐3 soil test extractant. This research aims to quantify the relationship between Bray‐1 and Mehlich‐3 extraction methods for both STP and STK for silt‐loam soils in southern Wisconsin. Soil samples were collected from three fields in November 2021. STK and soil test phosphorus STP were measured using both Bray‐1 and Mehlich‐3 extraction methods. The relationship between Bray‐1 and Mehlich‐3 extractants was quantified using linear regression. Soil test phosphorus as measured using Bray‐1 extractant was linearly related to STP as measured using Mehlich‐3 extractant (p &lt; 0.001; Adj. R2 = 0.97), and the relationship between STK results from Bray‐1 extraction and STK results from Mehlich‐3 extraction was also linear (p &lt; 0.001; Adj. R2 = 0.91). For the same soil samples, Mehlich‐3 extractant removed slightly more P and K as compared to Bray‐1 extractant. Due to the strong linear relationship between Mehlich‐3 and Bray‐1 extractants, simple regressions can be used to estimate Bray‐1 STP or STK from a soil test report that was generated using Mehlich‐3 lab methods, and vice versa, on WI silt‐loam soils.

Large root cortical cells and reduced cortical cell files improve growth under suboptimal nitrogen in silico.

Suboptimal nitrogen availability is a primary constraint to plant growth. We used OpenSimRoot, a functional-structural plant/soil model, to test the hypothesis that larger root cortical cell size (CCS), reduced cortical cell file number (CCFN), and their interactions with root cortical aerenchyma (RCA) and lateral root branching density (LRBD) are useful adaptations to suboptimal soil nitrogen availability in maize (Zea mays). Reduced CCFN increased shoot dry weight over 80%. Reduced respiration, reduced nitrogen content, and reduced root diameter accounted for 23%, 20%, and 33% of increased shoot biomass, respectively. Large CCS increased shoot biomass by 24% compared with small CCS. When simulated independently, reduced respiration and reduced nutrient content increased the shoot biomass by 14% and 3%, respectively. However, increased root diameter resulting from large CCS decreased shoot biomass by 4% due to an increase in root metabolic cost. Under moderate N stress, integrated phenotypes with reduced CCFN, large CCS, and high RCA improved shoot biomass in silt loam and loamy sand soils. In contrast, integrated phenotypes composed of reduced CCFN, large CCS, and reduced LRBD had the greatest growth in silt loam, while phenotypes with reduced CCFN, large CCS, and high LRBD were the best performers in loamy sands. Our results support the hypothesis that larger CCS, reduced CCFN, and their interactions with RCA and LRBD could increase nitrogen acquisition by reducing root respiration and root nutrient demand. Phene synergisms may exist between CCS, CCFN, and LRBD. CCS and CCFN merit consideration for breeding cereal crops with improved nitrogen acquisition, which is critical for global food security.

Influence of clay mineral weathering on green rust formation at iron-reducing conditions

Green rusts (GR) are important drivers for trace metal and nutrient cycling in suboxic environments. We investigated whether green rusts would incorporate aluminum (Al) or other elements from naturally-formed clay minerals containing easily-weatherable clay minerals (e.g. mica, interlayered clays). We isolated the clay minerals from a Matapeake silt loam soil by removal of silt and sand, organic matter, and reducible oxides to study mechanisms of interaction between Fe(II) and soil-sourced clay minerals. We conducted batch Fe(II) sorption experiments at multiple near-neutral pHs (6.5–7.5) and reaction times (2 h–365 days). Mineral transformations were characterized by selective extractions, X-ray diffraction (XRD), and Fe X-ray absorption spectroscopy (XAS) analyzed by shell-fitting and linear combination fitting (LCF) with natural and synthetic standards.Clay mineral fraction contained a mixture of quartz, kaolinite, interlayered vermiculite, mica, and chlorite with significant structural Fe (2.6% wt). Uptake of Fe(II) increased with pH and kinetics were rapid until 5 days, followed by slow continuous Fe(II) uptake. Citrate-bicarbonate desorption kinetics from Fe(II) sorbed clay released more Al and silicon (Si) compared with unreacted soil clay fraction whereas magnesium (Mg) and potassium (K) were unaffected. Citrate-bicarbonate extracted Fe contained more Fe(II) than an ideal GR with an Fe(II)/Fe(III) molar ratio of 5.50. Analysis of the Fe EXAFS by both LCF and shell fitting was best modeled as a combination of Fe(III)-clay reduction to Fe(II) and precipitation of GR and Fe(II)-Al LDH. After 7 days of Fe(II) sorption, LCF identified 55.2% total Fe in clay, 33.4% GR(Cl) and 11.4% Fe(II)-Al LDH. These results provide novel evidence of Fe(II)-Al LDHs precipitating on naturally-formed soil clay minerals as a minor phase to GR. The geochemical implications are that GRs formed in soils and sediments should be considered to have Al and Si as well as Mg substitutions affecting their structure and reactivity.

How Do Microplastics Affect Physical Properties of Silt Loam Soil under Wetting–Drying Cycles?

Soil physical properties are the main factors that influence soil fertility and directly affect the soil structure and water storage capacity. Microplastics (MPs), which have caused growing concern with respect to soil pollution, have readily been detected in cultivated soils. However, the current data regarding the effects of MPs on soil physical properties during wetting–drying cycles remain insufficient. Therefore, we aimed to explore the effects of different MP particle sizes (25, 150, 550, and 1000 μm) and concentrations (1, 3, and 5%, w/w) on soil physical properties under indoor wetting–drying cycle conditions. The addition of MPs was found to significantly reduce the saturated hydraulic conductivity and water holding capacity of soil, while impacting the bulk density, water content, and soil particle composition. The properties of soils treated with different MP particle sizes and concentrations exhibited significant differences, while the effects of wetting–drying cycles overshadowed those of MPs. Under the wetting–drying cycles, the saturated hydraulic conductivity and initial soil water content decreased significantly, the soil water holding capacity increased, and the soil bulk density showed a trend of increasing first and then decreasing. We attribute the change to a combination of the microplastics, soil particles, and frequent wetting–drying cycles. In this type of incubation, the constant change in the soil pore proportion results in a change in water and soil porosity, and finally alters the soil physical properties. These findings demonstrate that MP accumulation, together with dynamic environmental conditions, significantly impacts the physical properties of farm land soil.

Evaluation of site position and tillage effects on global warming potential from furrow-irrigated rice in the mid-southern USA

Dynamic and spatially variable environmental conditions within furrow-irrigated rice (Oryza sativa) systems can exacerbate greenhouse gas (GHG) production. Few studies have been conducted to evaluate the combined emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) from furrow-irrigated rice production. The objective of this field study was to evaluate estimated global warming potential (GWP) over two growing seasons (2018 and 2019) under conventional tillage (CT) and no-tillage (NT) and at up-, mid-, and down-slope positions in a production-scale, furrow-irrigated rice field on a silt-loam soil (Typic Albaqualfs). Gas samples were collected weekly between planting and harvest using enclosed-headspace, static chambers. In 2018, season-long CO2 (25,391 kg CO2 ha−1), and CH4 (64.0 kg CH4 ha−1) emissions and estimated GWP (36,396 CO2 eq.) were greater from the down- than the up- and mid-slope positions. In 2019, season-long CH4 emissions (85.0 kg CH4 ha−1) were greatest from the down-slope position, while CO2 (23,496 kg CO2 ha−1) emissions were greatest from the down-slope/CT combination. In 2018, GWP from CT was 25% greater than from NT, and 75 and 59% greater at the down- than at the up- and mid-slope positions, respectively, while GWP in 2019 was only numerically greater from CT than from NT. Results suggested that, unless environmental conditions involve flooding, NT could be a useful mitigation practice for reducing both CH4 and N2O emissions. Results also suggested that GHG and GWP mitigation could be accomplished by tailoring management practices to the various site positions in a production-scale, furrow-irrigated rice field.

Does residue incorporation influence available nitrogen release from cereal rye and tillage radish cover crops under controlled conditions?

AbstractNitrogen (N) captured by cover crops can be recycled for use by the following crop via decomposition and net mineralization. This study assessed the magnitude of inorganic‐N released from radish (Raphanus sativus L.) and cereal rye (Secale cereale L.) residue. The experiment was designed using a five by two factorial treatment structure with five cover crop residue treatments (radish shoots, radish roots, whole radish, cereal rye shoots, and no cover crop) and two levels of residue incorporation (incorporated and surface applied). Cover crop residues were applied to a silt loam soil on an equivalent N basis, incubated for 25 weeks and sampled periodically. Generally, NH4‐N concentration increased for 7–11 days after residue application, after which, NH4‐N concentration declined and NO3‐N concentration increased due to nitrification. Mineralization during the later days (42–179 days after residue application) was negligible from radish residue, but cereal rye shoots and radish roots released significant amounts of NH4‐N, which decreased over the last 137 d. Radish roots generated significantly more NO3‐N from day 42 through 141 than any other residue, while cereal rye shoots mineralized the least amount of NO3‐N from day 42 through 86. Incorporating cereal rye residue increases the occurrence of immobilization within the first 35 days after residue application; however, incorporation increases the rate at which NO3‐N is released from residues between 42 and 179 days after residue addition, regardless of cover crop species. Incorporation of residue can increase N mineralization rate, but the effect varies across cover crop species.

Measuring Sediment Transport Capacity of Concentrated Flow with Erosion Feeding Method

Sediment transport capacity in rills is an important parameter for erosion modeling on hillslopes. It is difficult to measure, especially at gentle slopes with limited rill length. In this study, a special flume with variable slope gradients in upper and lower sections was implemented to measure the sediment transport capacity. The upper flume section with a higher slope gradient generates faster water flow that could scout more sediment to feed the water flow in the rill. The rest of the flume is set at the designated slopes to measure the transport capacity in different slope and runoff conditions. A series of flume experiments were conducted with silt-loam soil to verify the method. The sediment transport capacity was measured under slope gradients of 5°, 10°, 15°, 20°, and 25° and a flow rate of 2, 4, 8, and 16 L min−1. The measured sediment transport capacity values were compared with reference measurements from other rill erosion experiments with similar materials and setups. At high slope gradients of 15°, 20°, and 25°, the newly suggested method produced almost the same transport capacity values. Under the low slope gradients of 5° and 10°, the maximum sediment concentrations from the 8 m long flume with the uniform gradients in the previous experiments, rill erosion with an 8 m long flume produced were about 36% lower than the values measured with the new method, which is insufficient to make the flow reach sediment transport capacity. The sediment transport capacities at lower slopes measured with the new method followed the same trend as those at higher slopes. The new method can supply enough sediments to ensure the flow approach transport capacity measurement and, therefore, provides a feasible approach for estimating sediment transport capacity for conditions with relatively gentle slopes.

Hydrological and erosion responses of steep spoil heaps to taproot and fibrous root grasses under simulated rainfalls

Spoil heaps, resulting from excavation and backfilling activities at construction sites, are one of the most important risk sources of soil erosion, threatening local ecosystems and even leading to geological disasters. However, after revegetation, spoil heaps can be transformed into available land resources such as cultivated land and forest land. Previous studies have reported the runoff and sediment reduction benefits of different vegetation measures on spoil heaps, while little information has been documented about what differences in the taproot and fibrous root grasses were transferred into the differences in hydrological and erosion processes. This study compared the effects of taproot (Artemisia gmelinii (A. gmelinii)) and fibrous root (Cynodon dactylon (C. dactylon)) grasses on soil erosion and runoff production processes and the reduction benefits of spoil heaps with silt loam soil. A series of rainfall events at three intensities (0.8, 1.2, and 1.8 mm min−1) were simulated on runoff plots (length of 3.0 m and width of 1.0 m) under treatments of A. gmelinii, C. dactylon, and bare soil (BS, as control) (each treatment was replicated), and the initial runoff time (IRT), saturated hydraulic conductivity, runoff rate (RR), flow velocity, and soil loss rate (SLR) were measured. The results showed that grasses delayed the IRTs on spoil heaps by 0.69–12.96 min compared BS, and the delay effects were more significant for fibrous root grass than for taproot grass. The soil loss reduction benefits (91.1 %) of the two kinds of grass were approximately 2.2 times greater than those of runoff volume reduction (42.1 %), and shear stress could be used to predict the soil loss rate following power functions (R2 = 0.72–0.85) for the grass-covered plots. The taproot grass exhibited a higher erosion reduction than fibrous root grass and is thus preferred to control the soil erosion of spoil heaps. Taproot grass has a greater stem diameter and can insert deeper into spoil heaps to consolidate the soil particles, which can improve roughness and hydraulic resistance, thereby producing a lower effective hydraulic shear stress that is directly exerted on soil particles. This study enhances the understanding of different grasses on the water erosion process and mechanism of spoil heaps and provides scientific guidance for selecting erosion control practices.

Registration of ‘Pembroke 2021’ soft red winter wheat

AbstractKentucky's wheat (Triticum aestivum L.) crop is planted into a rotation in which corn (Zea mays L.) is followed by wheat, which is followed by double‐crop soybean [Glycine max (L.) Merr.]. The causal agent of Fusarium head blight (FHB), Fusarium graminearum Schwabe, overwinters in corn stubble; thus, the Kentucky wheat crop is always at risk for FHB. The preeminent goal of the University of Kentucky wheat breeding program is releasing FHB‐resistant winter wheat cultivars. ‘Pembroke 2021’ (Reg. no. CV‐1198, PI 701381) is an early‐maturing, semi‐dwarf, soft red winter wheat cultivar developed and released in 2020 by the Kentucky Agricultural Experiment Station for FHB resistance, high yield and test weight potential, and lodging resistance. Pembroke 2021, tested as KY 07C‐1145‐94‐12‐5, was developed from the cross ‘IL99‐15867’/B990081//KY97C‐0554‐04‐05. The pedigree of the KY parent is VA94‐54‐549/Roane//Kristy. Pembroke 2021 was named for the Pembroke silt loam soil series prevalent in the main wheat‐producing area of Kentucky. Pembroke 2021 was selected from F4:5 head rows using a modified bulk breeding method; selected rows carried the resistance allele at the following FHB resistance quantitative trait loci: 1B Jamestown, 1A Neuse, 4A Neuse, and 3B Massey. Pembroke 2021 was tested in Kentucky in multi‐location replicated yield trials, the Uniform Eastern Soft Red Winter Wheat Nursery, the Mason‐Dixon nursery, the Uniform Northern Winter Wheat Scab Nursery, and the Kentucky Wheat Variety Trial.

Alkali Lignin-Based Hydrogel: Synthesis, Characterization, and Impact on Soil Water Retention From Near Saturation to Dryness

Highlights A lignin-based hydrogel was synthesized and shown to possess a swelling ratio of 2013%. The hydrogel contained important hydrophilic hydroxyl groups and macropores for water retention. The hydrogel improved soil water retention in silt loam soil at high matric potentials and in the dry soil range. Increasing hydrogel concentration increased water retention in a loamy fine sand soil at high and low matric potentials. Abstract. Superabsorbent polymers (hydrogels) have been proposed as soil amendments to increase the amount of plant-available water in the soil. Synthetic hydrogels have been widely investigated for use in agriculture. Due to increasing environmental concerns related to synthetic hydrogels, naturally sourced hydrogels are of interest because of their potential for increased biodegradability and biocompatibility. A lignin-based hydrogel was synthesized for this study, and its swelling properties and water absorption capacity were determined. The hydrogel was characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and gas pycnometry. A hanging water column, pressure plate apparatus, and dew point potentiometer were used to measure the soil water retention curve from saturation to oven-dryness for silt loam and loamy fine sand soils after amendment with the lignin-based hydrogel. Results showed a maximum swelling ratio in deionized water of 2013% of the hydrogel’s original mass, 1092% in tap water, and 825% in a 0.9% NaCl solution. The FTIR spectra of the hydrogel showed the presence of O-H bonds from the lignin structure, which renders the hydrogel reactive to a crosslinker and forms insoluble bonds, thereby allowing the hydrogel to swell when exposed to water. SEM images of the lignin hydrogels indicate large macropores, which allowed for water absorption. Applying hydrogels significantly increased the soil's water-holding capacity at 0.3% (w/w) treatment. Hydrogel treatment significantly increased water retention at saturation or near saturation by 0.12 cm3 cm-3 and at field capacity by 0.08 cm3 cm-3 for silt loam soil at 1% (w/w) treatment compared to the control treatment with no added lignin hydrogel. Hydrogel application increased water retention over the range of the soil water retention curve from -3 to -15,000 cm for the loamy fine sand soil at 1% (w/w) treatment. However, the application of lignin-based hydrogel did not affect plant available water capacity (PAWC) in either soil tested. These results serve as preliminary evidence upon which further lignin-based hydrogel amendment studies could be built by testing higher concentrations of hydrogel in the soil. Keywords: Lignin, Soil water retention curve, Super absorbent polymers, Swelling capacity, Water retention.

Phosphorus Fertilizer Effects on Near-Surface Soil Aggregation in Furrow-Irrigated Rice on a Silt-Loam Soil

Phosphorus Fertilizer Effects on Near-Surface Soil Aggregation in Furrow-Irrigated Rice on a Silt-Loam Soil

A NEW FRACTAL MODEL FOR PREDICTING SATURATED SOIL PERMEABILITY UNDER DIFFERENT DEFORMATION

The permeability coefficient and air-entry value of saturated soil are important hydraulic properties, which play an important role in engineering applications. Subsoil supporting foundation is subjected to stress and undergoes deformation; the saturated permeability coefficient of such deformed soil is of practical importance. With the help of fractal theory, based on the different fractal forms of Tao–Kong model, CCG model, Mualem model, and soil–water characteristic curve, this paper derives the saturated permeability coefficient models under four deformation conditions, considering the saturation permeability coefficient is inversely proportional to the square of the air-entry value and directly proportional to the square of the maximum aperture of the soil. Combining the prediction method of air-entry value under deformation conditions, four prediction methods for the permeability coefficient of deformed saturated soil are established and the method proposed in this paper is validated by the measured value of the saturated permeability coefficient of the deformed soil. As observed, the predicted values of the four methods for clay, silt loam, sandy loam and sandy soil under deformed conditions are in acceptable agreement with the measured values, and the prediction results of the second prediction method are the closest to the measured values.