Coarse-textured Soils Research Articles

The amendment value of pulp and paper mill sludges in Finnish coarse-textured soil

As a source of exogenous organic matter, pulp and/or paper mill sludges (PPMS) may have beneficial effects on crop productivity and soil chemical and physical properties. This study's aim was to assess the impacts of two different PPMS materials on crop yields, the quality of percolation water, and soil chemical and hydraulic properties in a three-year field experiment on a silt loam soil in East Central Finland. Fresh (FPMS) and lime-stabilized (LPMS) sludges were applied once at rates of 21–28 fresh-Mg ha−1 in the spring prior to the sowing of grass ley under barley as a cover crop and incorporated into the upper 7 cm soil layer. Supplemental nitrogen (N) was applied at levels of 40 and 80 kg ha−1. A decrease of barley grain yield due to N immobilization was observed at the N level 40 kg ha−1, but the standard N application rate (80 kg ha−1) connected with a moderate C:N ratio (FPMS 27:1, LPMS 24:1) was adequate to avoid significant yield losses. In the second and third year following the PPMS applications, there was a tendency for positive residual effects on the total dry matter yield of grass ley, which could be attributed to slow mineralization of sludge-N. The application of LPMS increased the pH in surface soil by 0.5–0.7-units and Ca concentration by 240–660 mg L−1 of soil relative to the non-amended control over the study period. In the year of PPMS applications, the amendments produced a significant increase (about 2.0 g kg−1) in the total carbon (C) concentrations in the uppermost 10 cm soil layer relative to the non-amended soil. During the following years, the change in soil C was no longer measurable, indicating relatively fast decomposition of sludge-C. Saturated hydraulic conductivity tended to be 1.4 to 2.3 times higher in the PPMS-treated soils than in the non-amended soil. Except for the decline in readily plant-available water, the other common water retention parameters were not significantly affected by the PPMS amendments. There were significant positive treatment effects on the amount of water retained between −13 and − 316 kPa matric potentials, suggesting an increase in medium-sized pores contributing to water storage in the soil. To maintain or enhance the beneficial direct and indirect effects of PPMS on crop yields and soil physico-chemical properties, repeated applications of PPMS are required, possibly combined with the use of organic fertilizers, especially during grass ley years.

Rainfall depth dominates overland flow and sediment yields of the coarse-textured soil: A case study in Southern China

Soil degradation, particularly due to water erosion, is a significant issue in many regions, including the mountainous areas of Southern China. This study investigated the response of overland flow and sediment yield to different rainfall patterns on a coarse-textured soil slope in Southern China. Three distinct rainfall regimes were identified through K-means clustering analysis, based on event rainfall depth, duration, and maximum 30-min intensity (I30). The results showed that rainfall regime II, characterized by moderate rainfall depth, duration, and I30, generated the highest accumulated surface runoff (97.3 mm) and soil erosion (1584.9 t km−2). Further analysis revealed that overland flow and sediment yield were positively correlated with various rainfall characteristics, including rainfall depth, mean intensity, duration, I30, rainfall energy, and rainfall erosivity. However, rainfall depth was identified as the dominant factor, exhibiting the stronger correlations with both the runoff depth (R2 = 0.77, RMSE = 0.396) and the erosion (R2 = 0.58, RMSE = 0.658) than did the mean rainfall intensity, I30, and duration. Note that RMSE values were expressed in logarithmic units in this study. Piecewise regression models were developed to predict overland flow and sediment yield based on rainfall depth, and these models were validated through in-situ rainfall simulation experiments. The results showed that these models produced acceptable soil and water loss predictions, with a mean bias of −0.093 mm and RMSE of 0.197 mm for the runoff depth, and a mean bias of −0.156 t km−2 and RMSE of 0.456 t km−2 for the sediment yield. Thus, rainfall depth is the dominant driver of soil and water loss in the coarse-textured soils of Southern China, and the developed regression models can be used to estimate overland flow and sediment yield in similar environments.

Pore Structures in Detritusphere of Soils Under Switchgrass and Restored Prairie Vegetation Community

ABSTRACTRoot detritusphere, that is, the soil in the vicinity of decomposing root residues, plays an important role in soil microbial activity and C sequestration. Pore structure (size distributions and connectivity of soil pores) in the detritusphere serves as a major driver for these processes and, in turn, is influenced by the physical characteristics of both soil and roots. This study compared pore structure characteristics in the root detritusphere of soils of contrasting texture and mineralogy subjected to > 6 years of contrasting vegetation: monoculture switchgrass and polyculture prairie systems. Soil samples were collected from five experimental sites in the US Midwest representing three soil types. Soil texture and mineralogy were measured using a hydrometer and x‐ray powder diffraction, respectively. The intact cores were scanned with x‐ray computed micro‐tomography to identify visible soil pores, biopores, and particulate organic matter (POM). We specifically focused on pore structure within the detritusphere around the POM of root origin. Results showed that the detritusphere of coarser textured soils, characterized by high sand and quartz contents, had lower porosity in the vicinity of POM compared with finer textured soils. POM vicinities in finer textured soils had high proportions of large (> 300 μm diameter) pores, and their pores were better connected than in the coarser soils. Lower porosity in the outer (> 1 mm) parts of the detritusphere of switchgrass than of prairie suggested soil compaction by roots, with the effect especially pronounced in the coarser soils. The results demonstrated that soil texture and mineralogy played a major, while vegetation played a more modest, role in defining the pore structure in the root detritusphere.

Water dispersible carbon nanomaterials reduced N, P, and K leaching potential in sandy soils: A column leaching study

Carbon nanomaterials (CNMs) — amendments with carbon in nanoscale form —could potentially enhance fertilizer delivery efficiency in agriculture, but their interaction with soil properties and nutrient co-mobility, especially in coarse-textured soils, remain poorly understood. We conducted a column leaching study in repacked soil columns to compare the co-leaching of novel water-dispersible CNMs and soil nutrients across two levels of CNMs applications (200 & 400 mg kg−1), two fertilization rates (low:80 mg kg−1 of N, P and K and high: 200 mg N kg−1, 100 mg P kg−1, 200 mg K kg−1, applied as ammonium nitrate, potassium phosphate, and potassium nitrate) and two soils (Spodosol with pH = 5.1, Alfisol with pH = 6.5). We imposed 12 leaching events to each column, with each leaching event adding water equivalent to the soil-pore volume (250 mL), resulting in cumulative leaching of 3000 mL of water through each column. CNMs applications reduced cumulative leaching losses of NO3-N (Spodosol: 8–12 %, Alfisol: 9–19 %), NH4-N (Spodosol: 2–14 %, Alfisol: 9–14 %), P (Spodosol: 23–27 %, Alfisol: 23–36 %) and K (Spodosol: 17–23 %, Alfisol: 24–26 %) compared to fertilized columns without CNMs. CNMs increased soil pH by up to 0.3 units (Spodosol) or 0.5 units (Alfisol), while lowering electrical conductivity by 15–20 % at the high fertilization rate in both soils. Columns with water-dispersible CNMs accumulated 25–30 % more total C in the base sections of the Alfisol compared to the Spodosol, indicating faster downward movement through the soil profile. Overall, we demonstrated that CNMs have the potential to reduce nutrient leaching in coarse-textured soils, which could be particularly beneficial in high-input intensive agricultural systems.

Distribution of soil fertility indices in aggregate size fractions under different land-use types for coarse-textured soils of the derived savannah

The research investigated the distribution of soil fertility indices among aggregate-size fractions across three land-use types (forested, cultivated, and fallow lands) for loamy sand at Ede-Oballa, a derived savannah in southeastern Nigeria. Surface soil samples from these land-use types were air-dried and separated into <0.25 mm, 0.25-0.5 mm, 0.5-1.0 mm, 1.0-2.0 mm, 2.0-4.0 mm, and 4.0-8.0 mm aggregates before analyses. There were significant interaction effects of land-use type and aggregate-size fraction on the distribution of soil particle sizes (sand, silt, and clay) and contents of total nitrogen, available phosphorus, exchangeable bases (Mg2+ and Na+), and exchangeable acidity as well as apparent cation exchange capacity (CEC). Land-use type affected soil pH, K+, Ca+, and percent base saturation but not soil organic carbon (SOC), which was rather unevenly distributed among the aggregate-size fractions. The distribution of most fertility indices, those defining CEC, and SOC content favoured >2.0 mm (large), 0.25-0.5 mm and <0.25 mm (micro-) aggregates, respectively, under cultivated land. However, soil total nitrogen and exchangeable acidity contents were best improved in the largest (4.0-8.0 mm) aggregates under forested and fallow lands, respectively. The study highlights the potential of land-use types generally and arable-crop cultivation specifically to engender aggregates of different sizes with specific roles in improving soil quality and fertility.

Effect of Vegetation Restoration on Soil Iron‐Associated Carbon Dynamics: Insights From Different Soil Textures

AbstractSoil iron (Fe)‐associated carbon (C) (Fe‐OC) plays a vital role in the soil C cycle due to its high stability, but vegetation restoration might alter the composition and quantity of Fe‐OC by introducing a large amount of plant‐derived C and affecting soil properties. However, how vegetation restoration affects soil Fe‐OC remains unclear. Herein, plant and topsoil samples from grasslands, shrublands, and forestlands across three soil types (loam, loess, and sandy soil) since cropland conversions were collected to address this issue. The results showed soil Fe‐OC content decreased in loam soil but increased in loess and sandy soil following vegetation restoration. Additionally, the Fe‐OC accumulation efficiency induced by vegetation restoration increased with the coarser soil texture. Vegetation restoration promoted the accumulation of Fe‐OC by increasing soil microbial biomass C, dissolved organic C, aromatic‐C, and citric acid, but also disrupted the combination of Fe oxides and C by introducing oxalic acid, reducing Fe oxide content and iron trivalent (Fe(III)). There were two‐sided effects of vegetation restoration on Fe‐OC, but the overall effect depends on the soil types. Moreover, isotopic evidence indicated that microbial source C is the main source of Fe‐OC, but Fe oxides preferentially adsorbed dissolved organic matter (DOM) and root deposits from plants rather than microbial residues and metabolites following vegetation restoration. In addition, Fe oxides preferentially adsorbed aromatic‐C compared to other functional group components. These findings indicated that vegetation restoration in coarser‐texture soils, coupled with selecting species that increase soil microbial biomass, produce more root deposits, and enhance DOM, contribute to the accumulation of soil Fe‐OC.

Soybean responds infrequently to phosphorus fertilization in Manitoba

Soybean ( Glycine max (L.) Merr.) production in Manitoba has increased substantially over the last 20 years, raising questions about phosphorus (P) fertilization in this region. Between 2013 and 2015, a study was conducted across 28 sites in Manitoba to evaluate the effect of P fertilizer rate and placement on soybean plant stand and seed yield. Treatments were 22.5, 45, and 90 kg P2O5 ha−1 applied as monoammonium phosphate, seed-placed, side-banded or broadcast, plus an unfertilized control treatment. Plant stand reduction due to seed-placed fertilizer toxicity was observed at five of 28 site-years, typically at the rate of 90 kg P2O5 ha−1. Stand reduction was most frequent on medium- to coarse-textured soils, dry soils or when seeding equipment had low seedbed utilization. Seed yield was reduced at two site-years due to seed placing 90 kg P2O5 ha−1, which reduced plant stands below the recommended threshold of 247 000 plants ha−1. Phosphorus fertilization did not increase seed yield, regardless of P rate, P placement, or Olsen soil test P level, except for one site-year where 45 and 90 kg P2O5 ha−1 increased seed yield by 343 and 430 kg ha−1, respectively. The extremely infrequent response to P fertilizer in combination with the high rate of P removal indicates that soybeans can use soil P reservoirs that are less available to other crops. Nevertheless, soybean growers in Manitoba should consider strategies for applying supplemental P to soybean or other crops in their rotation to maintain P fertility in soil.

Soil water dynamics and plant water uptake: Primeval mature vs. debris flow-developed half-mature subalpine fir stands in the eastern Tibetan Plateau

Natural disaster can disrupt soil structure and replace established vegetation with younger plants, altering the local hydrological processes. We used hydrogen and oxygen stable isotopes to examine soil water dynamics and plant water uptake patterns in two adjacent fir stands in the eastern Qinghai-Tibet Plateau: a primeval mature stand (MF, finer- textured soil) and a debris flow-developed half-mature stand (HMF, coarser-textured soil). Our results showed that the isotopic composition and soil gravimetric water content (SWC) in deep soil water in MF exhibited a more pronounced hysteresis pattern in response to precipitation compared to HMF, indicating lower turnover rate of soil water in MF. This was also confirmed by a smaller contribution of preferential flow to deep soil water in MF compared to HMF. The higher water storage (higher SWC values) and lower turnover rate of soil water suggest a higher soil water buffer capacity in MF. Additionally, both stands showed no significant difference in plant water sources, but plants in MF used more winter precipitation due to the lower soil water turnover rate. These differences suggest MF may be more vulnerable to water disasters, while HMF may be more susceptible to seasonal droughts under climate change. Our insights enhance understanding of hydrological processes linked to changing surface conditions and offer valuable information for managing forest water resources in mountainous regions.

Towards an ecosystem capacity to stabilise organic carbon in soils.

Soil organic carbon (SOC) accrual, and particularly the formation of fine fraction carbon (OCfine), has a large potential to act as sink for atmospheric CO2. For reliable estimates of this potential and efficient policy advice, the major limiting factors for OCfine accrual need to be understood. The upper boundary of the correlation between fine mineral particles (silt + clay) and OCfine is widely used to estimate the maximum mineralogical capacity of soils to store OCfine, suggesting that mineral surfaces get C saturated. Using a dataset covering the temperate zone and partly other climates on OCfine contents and a SOC turnover model, we provide two independent lines of evidence, that this empirical upper boundary does not indicate C saturation. Firstly, the C loading of the silt + clay fraction was found to strongly exceed previous saturation estimates in coarse-textured soils, which raises the question of why this is not observed in fine-textured soils. Secondly, a subsequent modelling exercise revealed, that for 74% of all investigated soils, local net primary production (NPP) would not be sufficient to reach a C loading of 80 g C kg-1 silt + clay, which was previously assumed to be a general C saturation point. The proportion of soils with potentially enough NPP to reach that point decreased strongly with increasing silt + clay content. High C loadings can thus hardly be reached in more fine-textured soils, even if all NPP would be available as C input. As a pragmatic approach, we introduced texture-dependent, empirical maximum C loadings of the fine fraction, that decreased from 160 g kg-1 in coarse to 75 g kg-1 in most fine-textured soils. We conclude that OCfine accrual in soils is mainly limited by C inputs and is strongly modulated by texture, mineralogy, climate and other site properties, which could be formulated as an ecosystem capacity to stabilise SOC.

Rhizosphere hydraulic regulation in maize: tailoring rhizosphere properties to varying soil textures and moistures

Abstract Aims Motivated by recent studies highlighting the active role of plants in influencing the hydraulic properties of the rhizosphere through mucilage exudation, this study explored the effect of plant rhizosphere regulation on the emergent hydraulic properties of the rhizosphere under varying soil texture and moisture levels. Methods Maize (Zea mays) plants were cultivated in sand and loam soils exposed to varying moisture levels. Neutron radiography was employed to quantify the profile of water content ($${\theta }_{r})$$ θ r ) around lateral and crown roots. The $${\theta }_{r}$$ θ r were used to derive rhizosphere hydraulic indices such as rhizosphere extension ($${d}_{rh}$$ d rh ), water content at the root-soil interface ($${\theta }_{rs}$$ θ rs ), and water content in the rhizosphere ($${\theta }_{rh}$$ θ rh ). The latter two attributes were normalized by the respective bulk soil water contents ($${\theta }_{rs}^{*}$$ θ rs ∗ , $${\theta }_{rh}^{*}$$ θ rh ∗ ). Results Results showed a higher $${\theta }_{rs}^{*}$$ θ rs ∗ , $${\theta }_{rh}^{*}$$ θ rh ∗ and $${d}_{rh}$$ d rh in coarse-textured soil versus fine-textured soil. This indicates a more pronounced rhizosphere development in sand compared to loam, possibly via mucilage exudation to maintain better root-soil contact. In contrast, soil water content did not impact the rhizosphere properties of crown roots but impacted the rhizosphere properties of lateral roots. The derived rhizosphere water retention curves revealed a higher water-holding capacity of the rhizosphere in both soils compared to bulk soil. Conclusions Our study underscores that soil-grown maize plants dynamically adjust the hydraulic properties of their rhizosphere in response to external factors, primarily aiming to optimize root-soil contact. That leads to a more pronounced rhizosphere in coarser textures, interacting with the soil moisture.

Laboratory observations for examining estimates of soil dry surface layer thickness with parsimonious models

ABSTRACT Soil dry surface layer (DSL) thickness is often considered a key parameter for land surface resistance to gas exchange. Commonly used, simple models for DSL thickness are typically empirical in nature and based on limited observational evidence. Laboratory experiments were performed to test soil condition and boundary effects on DSL formation. DSL thickness was analyzed in soil columns with varying texture, initial water content, and potential evaporation rate. DSLs formed to greater depth in fine-textured compared to coarse-textured soils, when beginning from similar initial water content. Based on experiments, we compared a simple but physically-based mass balance DSL model to an empirical DSL model from the literature. The mass balance model performed better than the empirical relative-wetness-based model, and is similar in structure to the current DSL parameterization in the Community Land Model. Results suggest soil resistance parameterizations can be improved by employing simple, but texture-dependent, physically-based DSL formulations.

Random forest approach to estimate soil thermal diffusivity: Evaluation and comparison with traditional pedotransfer functions

Pedotransfer functions (PTFs) are widely used in science and engineering to calculate soil thermal diffusivity (κ) as a function of soil moisture content and other soil physical properties. However, available data on κ are rather scarce and already developed PTFs suffer from significant uncertainties in applicability and performance. Few studies attempted to systematically review and evaluate these PTFs with large dataset of κ. The objectives of this study were to (1) review and collate currently available PTFs for κ; (2) compile a κ dataset to evaluate performance of these PTFs, (3) build a machine learning (ML) (i.e., random forest-RF) model with three classes of soil physical properties to determine soil physical properties most appropriate to use as predictors for calculating κ, and (4) compare the RF modelling with the traditional PTFs. The correlation coefficient (r), centered root-mean-square (E'), and standard deviation (SD) were used to evaluate the performance of the above PTFs. A total of nine PTFs were synthesized and assessed with a compiled dataset consisting of 998 measurements from 106 soils with a wide range of textures. In general, the PTFs of Lukiashchenko and Arkhangelskaya (2018) (LA2018–1 and LA2018–2) perform the best. While the quadratic equation of Mady and Shein (2018) (MS2018–1 and MS2018–2) showed better performance for coarse and medium textured soil. However, the overall performance of the nine PTFs for predicting κ was not as accurate as RF. RF can satisfactorily calculate κ taking into account sand, silt, clay contents, and soil moisture content as predictors.

Tillage and mulching effects on carbon stabilization in physical and chemical pools of soil organic matter in a coarse textured soil

Characterization of soil organic carbon (SOC) in terms of size, storage inside aggregates and chemical recalcitrance is vital to understand mechanisms of its stabilization and to devise climate smart agricultural management practices. Tillage and residue retention are known to influence carbon (C) storage within soil aggregates and its accumulation as particulate organic matter as well as organomineral complexes. However, the effect of tillage and crop residue retention on C stabilization in coarse textured soils through various mechanisms is not well understood. We studied the effect of conservation agriculture involving no tillage with surface residue mulch (NTM) in maize-wheat sequence on particulate (POC) and mineral associated organic C (MinOC), C storage within aggregates and acid non-hydrolysable C (NHC) in a sandy loam soil. Compared to conventional tillage without residue retention (CTM0), the NTM improved SOC stocks by 23% in top 15-cm soil and significantly increased coarse POC (∼92 to 284%) and fine POC (67 to 123%) with relatively little effect on MinOC. This indicated that MinOC had relatively small contribution towards SOC stabilization in coarse textured sandy loam soils with limited potential to form organomineral complexes. The results further showed that the effects of NTM were brought about by improved aggregate stability and C preservation inside macroaggregates of size >1 mm. Furthermore, greater amount of SOC (2.64 g C kg−1) and macroaggregate associated C (0.35–0.59 g C kg−1) occurred in recalcitrant forms (NHC) under NTM compared to conventional (CT) and deep tillage (DT). The NTM also impacted the belowground C input through improved root length density (RLD) and development of fibrous roots expressed as specific root length (SRL), which influenced SOC build-up and stabilization. It is concluded that compared to the existing practice of CTM0, the conservation agriculture involving NT with residue retention leads to SOC sequestration in coarse textured soils. Its large scale adoption, besides helping in climate change mitigation will lead to soil health improvement.

Effects of fertilization applications on soil aggregate organic carbon content and assessment of their influencing factors: A meta-analysis

Fertilizer application plays an important role in agricultural soil organic carbon (SOC) and its sustainable management. However, there is a lack of consensus about the mechanisms regarding fertilizer application in the soil on the procedure of carbon sequestration and sink enhancement in the aggregates. In this study, the extent by which various fertilization treatments, fertilization durations, climate conditions, soil texture, and land-use types affected the organic carbon (OC) content of different particle-size aggregates was quantitatively assessed using a meta-analysis of 696 treatment comparisons from 36 published studies. Based on the meta-analysis results, fertilization enhanced the OC contents of macroaggregates and clay and silt particles, particularly through replenishing organic material. Long-term fertilization increased the OC content of macroaggregates (>0.25 mm), while the OC content of the clay and silt particles (<0.053 mm) reached a maximum at 15.4 years of fertilization, after which it reached carbon saturation. Organic fertilizer effectively increased the OC content of small macroaggregates (0.25–2 mm) and microaggregates (0.053–0.25 mm) at lower temperatures and precipitation. Compared with inorganic fertilization, combined organic–inorganic fertilization increased OC contents of all sizes of aggregates in sandy or clay loam soils, but decreased OC contents of microaggregates and clay and silt particles in silt loam soils. All fertilization treatments increased the OC content of all particle-size aggregates in upland soils. In contrast, inorganic fertilization and mixed organic–inorganic fertilization reduced the OC content of microaggregates (0.053–0.25 mm) and clay and silt particles (<0.053 mm) in paddy field soils. In conclusion, the application of organic fertilizers is more conducive to the accumulation of OC in agricultural soil aggregates. Whereas the limiting factors for the accumulation of OC content in soil aggregates vary under different conditions, organic fertilizer inputs should be given more consideration, especially in dryland and coarse-textured soils.

Nitrifier controls on soil NO and N2O emissions in three chaparral ecosystems under contrasting atmospheric N inputs

High rates of atmospheric N deposition can increase ecosystem N availability and stimulate N losses from soils via nitric oxide (NO; an air pollutant at high concentrations) and nitrous oxide (N2O; a strong greenhouse gas) emissions as predicted by N saturation theory. However, it remains unclear whether theories developed in mesic ecosystems apply to drylands, where plant N uptake and N availability are often decoupled. NO and N2O are produced during the oxidation of ammonia (i.e., nitrification) by ammonia-oxidizing archaea (AOA) or ammonia-oxidizing bacteria (AOB). Because AOB may be favored in N-rich environments and may emit more NO and N2O than AOA, high atmospheric N inputs may favor both NO and N2O emissions. To assess whether atmospheric N deposition favors AOB- and AOA-derived N emissions, we selectively inhibited AOA and AOB and measured NO and N2O from soils collected from three dryland sites exposed to relatively low (3.8 kg ha−1 = Low N) or high (11.8 kg ha−1 = High N-A; 15.6 kg ha−1 = High N–B) atmospheric N inputs. We found that while the High N–B deposition site had the lowest AOA:AOB ratio (2.3 ± 0.6), consistent with expectations, this site did not emit the most NO and N2O. Rather, AOA emitted between 21 and 78% of the NO from our sites, with higher AOA-derived NO emissions from relatively coarse-textured soils in the Low N deposition site. In addition to nitrification, other processes also emitted NO and N2O, especially in the High N-A site where non-nitrifier NO and N2O emissions were ∼2–4 × higher than the other sites, and where finer textured soils may favor denitrification. Interactions between soil texture and N availability, rather than shifts in nitrifier communities, likely determine whether atmospheric N deposition is retained in these dryland sites or reemitted to the atmosphere as NO or N2O.

The de‐domestication of Ornithopus sativus Brot. to develop cultivars with physical dormancy (hardseed)

AbstractOrnithopus sativus Brot. (French serradella) is a forage legume that is well adapted to acidic coarse textured soils (sands) which are characterized by poor nutrition and an inability to retain water. During the process of domestication of O. sativus, there was an unintentional loss of seed physical dormancy (PY) thus compromising its self‐regeneration after a cropping interval. Through mass screening of seed, we identified for the first time that heritable sources of PY exist in three populations of O. sativus. This rare genetic material was then incorporated into suitable genetic backgrounds of differing maturity through targeted hybridization. We demonstrated that the heritability of PY was dominant in the population of 97ZAF5sat but inconsistently recessive in the population of cv. Emena. Flowering time was variable in each source population, with a large variation in time to emergence of first flowers (95–175 days). Selection for early flowering maturity was heritable and stable. F6 generations selected for PY in different maturity classes were then evaluated in situ to establish whether PY would allow a proportion of seeds to survive in the soil through consecutive seasons exposed to a Mediterranean climate. The breeding lines FHS3, 7 and 23 remained dormant, thus viable, in the soil for up to 3 years, indicating the likelihood that O. sativus with PY could survive and persist in a ley farming system. The de‐domestication program in O. sativus has resulted in commercially successful cultivars (most recently cv. Fran2o) suited to sustainable dryland agriculture in a Mediterranean climate.

Impacts of conservation agriculture on soil C and N stocks and organic matter fractions: comparing commercial producer fields with a long-term small-plot experiment in Brown Chernozems of Saskatchewan

Conservation agriculture (CA) is increasingly promoted to build soil organic matter (SOM) based on findings from predominantly small-plot long-term agroecosystem experiments (LTAEs), with minimal on-farm data. Using commercial producer fields ( n = 20) in the Brown Chernozemic soil zones of Saskatchewan, Canada, which were sampled before (1996) and after (2018) adopting direct-seeding and continuous cropping (1997), we examined changes in soil organic carbon (SOC) and soil total nitrogen (STN) stocks, along with C and N stocks in particulate (POM) and mineral-associated organic matter (MAOM), and compared them to an LTAE in the same soil zone. After 21 years, SOC and STN stocks (0–30 cm depth) increased by 13% and 21%, respectively, in commercial producer fields, and were more pronounced in finer- than coarser-textured soils. Conversely, there were no significant changes (0–30 cm depth) after 18 years (1998–2016) with CA (continuous wheat and pulse-wheat under no-tillage (PW-NT)) in the LTAE, except that STN stock for PW-NT decreased by 7.7%. The estimated rate of change to 30 cm depth was similar between the commercial fields and LTAE for SOC (0.28 and 0.16 Mg C ha−1 year−1, respectively), but not STN (0.04 and −0.03 Mg N ha−1 year−1, respectively). Changes were more evident in the MAOM than POM fraction in both cases. Although the impact of CA may be similar, as observed for SOC, actual on-farm changes will depend on site-specific factors, and specific CA practice. Therefore, on-farm monitoring studies are needed for more accurate assessments of SOM changes and C sequestration potentials.

Trade-offs between nitrogen and phosphorus removal with floodplain remediation in agricultural streams

To improve water quality and reduce instream erosion, floodplain remediation along agricultural streams can provide multiple ecosystem services through biogeochemical and fluvial processes. During floodplain inundation, longer water residence time and periodic anoxic conditions can lead to increased nitrogen (N) removal through denitrification but also mobilization of phosphorus (P), impeding overall water quality improvements. To investigate the capacity for N and P processing in remediated streams, we measured potential denitrification and nitrous oxide production and yields together with potential P desorption and P fractions in floodplain and stream sediments in ten catchments in Sweden. Sediment P desorption was measured as equilibrium P concentration, using P isotherm incubations. Denitrification rates were measured with the acetylene inhibition method. Sediment nutrient process rates were combined with hydrochemical monitoring along remediated streams and their paired upstream control reaches of trapezoidal shape to determine the impact of floodplains on water quality. The correlation between floodplain denitrification rates and P desorption (r = 0.53, p = 0.02) revealed a trade-off between soluble reactive P (SRP) and nitrate removal, driven by stream water connectivity to floodplains. Nitrous oxide production was not affected by differences in P processing, but nitrous oxide yields decreased with higher denitrification and P desorption. The release of SRP from floodplains (0.03 ± 0.41 mg P kg−1 day−1) was significantly lower than from trapezoidal stream banks (0.38 ± 0.37 mg P kg−1 day−1), predicted by long-term SRP concentrations in stream water and floodplain inundation frequency. The overall impact of SRP release from floodplains on stream SRP concentrations in remediated reaches was limited. However, the remediated reaches showing increased stream SRP concentrations were also frequently inundated and had higher labile P content and coarse soil texture in floodplain sediments. To fully realize the potential for water quality improvements with constructed floodplains in agricultural streams, the promotion of denitrification through increased inundation should be balanced against the risk of P release from sediments, particularly in streams with high SRP inputs.

The effect of amorphous silica on soil–plant–water relations in soils with contrasting textures

This study investigates how amorphous silica (ASi) influences soil–plant–water interactions in distinct soil textures. A sandy loam and silty clay soil were mixed with 0 and 2% ASi, and their impact on soil retention and soil hydraulic conductivity curves were determined. In parallel, tomato plants (Solanum lycopersicum L.) were grown in experimental pots under controlled conditions. When plants were established, the soil was saturated, and a controlled drying cycle ensued until plants reached their wilting points. Soil water content, soil water potential, plant transpiration rate, and leaf water potential were monitored during this process. Results indicate a positive impact of ASi on the sandy loam soil, enhancing soil water content at field capacity (FC, factor of 1.3 times) and at permanent wilting point (PWP, a factor of 3.5 times), while its effect in silty clay loam was negligible (< 1.05 times). In addition, the presence of ASi prevented a significant drop in soil hydraulic conductivity (Kh\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${K}_{h}$$\\end{document}) at dry conditions. The Kh\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${K}_{h}$$\\end{document} of ASi-treated sandy loam and silty clay at PWP were 4.3 times higher than their respective control. Transpiration rates in plants grown in ASi-treated sandy loam soil under soil drying conditions were higher than in the control, attributed to improved soil hydraulic conductivity. At the same time, no significant difference was observed in the transpiration of plants treated with ASi in silty clay soil. This suggests ASi boosts soil–plant–water relationships in coarse-textured soils by maintaining heightened hydraulic conductivity, with no significant effect on fine-textured soils.

Effectiveness of three nitrification inhibitors on mitigating trace gas emissions from different soil textures under surface and subsurface drip irrigation

Nitrification inhibitors (NIs) and drip irrigation are recommended to mitigate trace gas emissions from agricultural soils. However, studies comparing the effect of different NIs on the release of trace gases from soils with contrasting textures under subsurface (SBD) and surface (SD) drip irrigation are lacking. Therefore, this study aimed to assess the effectiveness of three NIs in mitigating nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) emissions from two soils with different textures under SBD, with pipe buried in 10 cm depth, and SD. Two greenhouse experiments were carried out with silt loam and loamy sand soil textures cultivated with wheat under SBD and SD to assess the effectiveness of the NIs Dicyandiamide (DCD), 3,4-Dimethylpyrazole phosphate (DMPP), and 3-Methylpyrazol combined with Triazol (MP + TZ). Ammonium sulfate was applied at a rate of 0.18 g N kg soil−1. The measured variables were daily and cumulative N2O–N, CO2–C, and CH4–C emissions, as well as soil NH4+-N and NO3−-N concentrations. The NIs and SBD had additive effects on reducing N2O–N emissions in the silt loam, but not in the loamy sand soil texture. Under SBD, total N2O–N emissions were 44% and 52% lower than under SD in the silt loam and loamy sand soil textures, respectively. Moreover, DMPP kept the highest NH4+-N concentrations and promoted the lowest N2O–N release. CO2–C and CH4–C total emissions were not affected by the treatments. Our findings supported the hypothesis that SBD decreases N2O–N emissions relative to SD. Among the investigated NIs, DMPP has the highest effectiveness in retarding nitrification and mitigating N2O–N release under the studied treatments. Finally, in coarse-textured soils, the use of NIs could be sufficient to significantly abate N2O–N emissions.