Soil Water Plant Research Articles

Enhancing soil water retention and plant growth with thermal crosslinked silk sericin-based hydrogel

In this study, a simple and clean crosslinking method was evaluated as a novel strategy to improve the structural stability of sericin-based hydrogels for soil water retention. The hydrogels were prepared by casting a polymer mixture of silk sericin (SS), carboxymethylcellulose (CMC), and polyvinyl alcohol (PVA). The films (HF) were heated at 90 °C for 4 h to obtain a thermally crosslinked hydrogel (HFT). The HFT was evaluated using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM). The changes in water absorption, gel fraction, and swelling behavior after crosslinking were also analyzed. The biodegradability of the HFT and its performance as a soil conditioner were evaluated through burial tests and in vivo assays using Chilli plants (Capsicum annuum), respectively. According to the results, the thermal crosslinking of HF is the result of the formation of microcrystals in the SS and PVA fractions, as well as the development of a dense network of H-bonds. Both mechanisms promoted the formation of a more stable pore structure in the HFT, which proved to be potentially biodegradable and suitable for improving soil water retention and supporting plant growth. Regarding HFT biodegradability, rapid weight loss was noted during the first 14 days of the soil burial test. On the other hand, HFT improved the availability of soil water and nutrients, favoring leaf growth and likely chlorophyll production.

Soil–Plant–Water Systems and Interactions

To comprehend the soil–plant–water system and how its constituents interact with each other, it is essential to better understand its effect on ecosystems [...]

Soil, climate, and landscape drivers of base cation concentrations in green stormwater infrastructure soils

Deicing practices and infrastructure weathering can impact plants, soil, and water quality through the input and transport of base cations. Base cation accumulation in green stormwater infrastructure (GSI) soils has the potential to decrease soil infiltration rates and plant water uptake or to promote leaching of metals and nutrients. To understand base cation retention in GSI soils and its drivers, we sampled 14 GSI soils of different age, contributing areas, and infiltration areas, across 3 years. We hypothesized that soil, climate, and landscape drivers explain the spatial and temporal variability of GSI soil base cation concentrations. Sodium (Na), Calcium (Ca), and Magnesium (Mg) concentrations in GSI soils were higher than in reference soils, while Ca and Mg were similar to an urban floodplain soil. Neither the contributing area, contributing impervious area, nor their ratios to infiltration area predicted base cation concentrations. Age predicted the spatial variability of Potassium (K) concentrations. Ca and Mg were moderately predicted by sand and silt, while clay predicted Mg, and sand predicted K. However, no soil characteristics predicted Na concentrations. A subset of sites had elevated Na in Fall 2019, which followed a winter with many freezing events and higher-than-average deicer salt application. K in sites with elevated Na was lower than in non-elevated sites, suggesting that transient spikes of Na driven by deicer salt decreased the ability of GSI soils to accumulate K. These findings demonstrate the large variability of GSI soil base cation concentrations and the relative importance of soil, climate, and landscape drivers of base cation dynamics. High variability in GSI soil data is commonly observed and further research is needed to reduce uncertainties for modeling studies and design. Improved understanding of how GSI soil properties evolve over time, and their relation to GSI performance, will benefit GSI design and maintenance practices.

Biocha Soil Amendment: Effect on Soil, Crop Performance, and Diseases Resistance

One of the main challenges facing developing countries is an ever-increasing gap between population growth and food supply. Diseases, insects, and weeds decrease the production of crops worldwide by 36%. Hence, control of crop pests contributes to increased crop production. Organic amendments to the soil have direct impacts on crop productivity and plant health as it enhances soil fertility, water, and nutrient retention and plant disease defense mechanisms. Biochar is an important organic amendment. It is produced by the pyrolysis process, whereby organic substances are broken down at higher temperatures in low oxygen conditions. Biohar improved soil nutrient availability and water retention capacity, and induced plant resistance against broad ranges of plant pathogenic organisms including fungi, nematodes, and bacteria. Biochar soil amendment also enhances root-associated microbes such as flavobacterium and arbuscular mycorrhizae. Biochar amendments can increase soil essential nutrients for crop productivity and suppress plant pathogens. Suppression of plant pathogens is attributed to the stimulation of beneficial soil microbes, providing nutrients, and inducing plant defense. The objectives of the review are to depict the importance of biochar soil amendment on crop performance, disease resistance, and soil properties.

Response of soil water in deep dry soil layers to monthly precipitation, plant species, and surface mulch in a semi-arid hilly loess region of China

Large-scale deep soil desiccation has occurred in the Loess Plateau caused by large-scale introduced vegetation rehabilitation over many years. Consequently, this occurrence has raised concerns among scholars regarding the obstacles to plant succession that may result from deep soil desiccation following large-scale artificial vegetation construction. In order to answer the question of whether vegetation can be replanted and water can be restored in the deep dry soil environment in this region, large soil columns in the field were used to simulate dry soil in the 0–1000 cm layer. Some soil columns were planted with Robinia pseudoacacia, Caragana korshinskii, alfalfa (Medicago sativa L.), jujube (Zizyphus jujuba Mill.), and Poa annua, while other columns were covered with stones, branches, ground cloth, and white plastic film. Bare soil columns were used as the control treatment (CK). Dynamic changes of soil water in the 0–1000 cm soil layer of the soil columns were regularly observed, and five years (2014–2018) of continuous observation data were analyzed. The results showed that: (1) Under the condition of severe desiccation of the deep soil layer in the semi-arid loess region of China, reintroducing plants can be successful, and the reintroduced plants can grow normally depending on the amount of local precipitation; (2) Due to the different water consumption amounts of reintroduced plants, a new soil water balance can emerge in the dry soil layer. Plants with high water consumption planted on dry soil can result in more severe soil desiccation, while plants with low water consumption planted on dry soil can alleviate soil desiccation. (3) The use of soil surface mulching had a strong effect on soil water restoration, with the order of effectiveness for soil desiccation remediation being white plastic film > ground cloth > branches ≈ stones > control (CK). In particular, the use of white plastic film can transform severely desiccated soil in the 0–640 cm layer into a non-desiccated state. These research findings directly address long-standing concerns of ecologists regarding plant succession and soil water restoration in deep desiccated soil, and can serve as a reference for the sustainable development of ecological construction in the Loess Plateau of China.

Indirect regulation of topsoil nutrient cycling by groundwater depth: impacts on sand-fixing vegetation and rhizosphere bacterial communities.

The impact of groundwater table depth (GTD) on bacterial communities and soil nutrition in revegetated areas remains unclear. We investigated the impacts of plant growth and soil physicochemical factors on rhizosphere bacterial communities under different GTD. The four plant growth indices (Pielou, Margalef, Simpson, and Shannon-Wiener indices) and soil water content (SWC) at the Artem and Salix sites all showed a decreasing trend with increasing GTD. Salix had a higher nutrient content than Artem. The response of plant rhizosphere bacterial communities to GTD changes were as follows. Rhizosphere bacteria at the Artem and Salix sites exhibited higher relative abundance and alpha diversity in SW (GTD < 5 m) compared than in DW (GTD > 5 m). Functional microbial predictions indicated that the rhizosphere bacterial communities of Artem and Salix promoted carbon metabolism in the SW. In contrast, Artem facilitated nitrogen cycling, whereas Salix enhanced both nitrogen cycling and phototrophic metabolism in the DW. Mantel test analysis revealed that in the SW of Artem sites, SWC primarily governed the diversity of rhizosphere and functional bacteria involved in the nitrogen cycle by affecting plant growth. In DW, functional bacteria increase soil organic carbon (SOC) to meet nutrient demands. However, higher carbon and nitrogen availability in the rhizosphere soil was observed in the SW of the Salix sites, whereas in DW, carbon nutrient availability correlated with keystone bacteria, and changes in nitrogen content could be attributed to nitrogen mineralization. This indicates that fluctuations in the groundwater table play a role in regulating microbes and the distribution of soil carbon and nitrogen nutrients in arid environments.

Responses of Soil Respiration to the Interactive Effects of Warming and Drought in Alfalfa Grassland on the Loess Plateau

Elevated temperature and frequent drought events under global climate change may seriously affect soil respiration. However, the underlying mechanism of the effects of warming and drought on soil respiration is not fully understood in the context of the Loess Plateau. This study examined the response of soil respiration (Rs) to multiple factors, including warming (W), drought (P), and their interaction (WP), in the semi-arid grassland of the Loess Plateau in Northwest China. The research period was from May to November 2022, with an open-top heating box used for warming and a rain shelter used for drought. The results showed the following: (1) Rs ranged from 1.67 μmol m−2 s−1 to 4.77 μmol m−2 s−1, with an average of 3.36 ± 0.07 μmol m−2 s−1. The cumulative soil carbon flux ranged from 500.97 g C·m−2 to 566.97 g C·m−2, and the average cumulative soil respiration was 535.28 ± 35.44 g C·m−2. (2) Warming increased Rs by 5.04 ± 3.11%, but drought inhibited Rs by 3.40 ± 3.14%, and the interaction between warming and drought significantly reduced soil respiration by 11.27 ± 3.89%. (3) The content of particulate organic carbon (POC), dissolved organic carbon (DOC), soil organic carbon (SOC), and readily oxidized carbon (ROC) decreased with the increased soil depth. ROC after W and WP treatments was significantly higher than that of the control, and POC after P treatment was significantly higher than CK (p &lt; 0.05). (4) The seasonal variation of soil respiration was positively correlated with soil temperature, soil water content, plant height, and leaf area index (p &lt; 0.05), but the response rules differed during different regeneration periods. Soil water content; soil water content and leaf area index; and soil water content, soil temperature, and leaf area index were the factors that regulated the variation in soil respiration in the first, second, and third regeneration periods, respectively. These results clearly showed the limiting effect of drought stress on the coupling between temperature and soil respiration, especially in semi-arid regions. Collectively, the variations in soil respiration under warming, drought, and their interactions were further regulated by different biotic and abiotic factors. Considering future warming, when coupled with increased drought, our findings indicate the importance of considering the interactive effects of climate change on soil respiration and its components in arid and semi-arid regions over the next decade.

Mean transit time of water bodies in a typical soil-plant-atmosphere continuum of the subtropical monsoon region

The mean transit time (MTT) is a good indicator of water cycle processes. We know little about the MTT of different water bodies within the soil-plant-atmosphere continuum (SPAC) in the subtropical monsoon region. We estimated the MTT of stratified soil water at different depths as well as the xylem water and leaf water in typical Cinnamomum camphora woodland located in Changsha City from March 2017 to October 2019. The main methods used in this study included the stable isotope technology, the linear mixed model and the sine wave fitting method. The results showed that the stable isotopes were more depleted in summer and enriched in winter for different water bodies within the SPAC. The δ2H values of soil water gradually decreased as depth increased. The δ2H values of xylem water closely resembled those of soil water, but the δ2H values of leaf water were more positive and exhibited larger variation. Results of the linear mixed model indicated that the lower MTT values of soil water and plant water occurred between June and September, while the higher values were often observed around January and from April to May. The precipitation replenishment exhibited a significant negative correlation with the MTT. The MTT of soil water generally increased with depth, although preferential flow could enhance the replenishment of deeper soil water and subsequently reduce the MTT. The mean MTT values of xylem water and leaf water were similar. Results of the sine wave fitting method showed that the young water fraction (Fyw) of soil water gradually decreased as depth increased, while the MTT of soil water gradually increased as depth increased. The Fyw and MTT of xylem water were lower and higher than those of leaf water, respectively. Both the mean MTT values of soil water based on the linear mixed model or the sine wave fitting method increased from the surface to the deeper soil layers. The former exhibited a smaller variation range and the latter showed a larger variation range. The mean MTT value of xylem water based on the linear mixed model was 2.4 days less than that of leaf water, while the MTT value of xylem water in the sine wave fitting method was 87.4 days higher than that of leaf water. These differences may be due to the parameterization of "new/young water", the uncertainty of results, and the effect of evaporative fractionation. This study contributes to a better understanding of water transport and consumption processes within the SPAC and provides valuable insights for agricultural production and water resources management in the subtropical monsoon region.

Transcriptomic and metabolomic analysis of changes in grain weight potential induced by water stress in wheat

The sink strength of developing ovaries in wheat determines the grain weight potential. The period from booting to the grain setting stage is critical for ovary growth and development and potential sink capacity determination. However, the underlying regulatory mechanism during this period by which the wheat plant balances and coordinates the floret number and ovary/grain weight under water stress has not been clarified. Therefore, we designed two irrigation treatments of W0 (no seasonal irrigation) and W1 (additional 75 mm of irrigation at the jointing stage) and analyzed the responses of the ovary/grain weight to water stress at the phenotypic, metabolomic, and transcriptomic levels. The results showed that the W0 irrigation treatment reduced the soil water content, plant height, and green area of the flag leaf, thus reducing grain number, especially for the inferior grains. However, it improved the grain weight of the superior and inferior grains as well as average grain weight at maturity, while the average ovary/grain weight and volume during –3 to 10 days after anthesis (DAA) also increased. Transcriptomic analysis indicated that the genes involved in both sucrose metabolism and phytohormone signal transduction were prominently accelerated by the W0 treatment, accompanied by greater enzymatic activities of soluble acid invertase (SAI) and sucrose synthase (Sus) and elevated abscisic acid (ABA) and indole-3-acetic acid (IAA) levels. Thus, the sucrose content decreased, while the glucose and fructose contents increased. In addition, several TaTPP genes (especially TaTPP-6) were down-regulated and the IAA biosynthesis genes TaTAR1 and TaTAR2 were up-regulated under the W0 treatment before anthesis, which further increased the IAA level. Collectively, water stress reduced the growth of vegetative organs and eliminated most of the inferior grains, but increased the ABA and IAA levels of the surviving ovaries/grains, promoting the enzymatic activity of Sus and degrading sucrose into glucose and fructose. As a result, the strong sucrose utilization ability, the enhanced enzymatic activity of SAI and the ABA- and IAA-mediated signaling jointly increased the weight and volume of the surviving ovaries/grains, and ultimately achieved the trade-off between ovary/grain weight and number in wheat under water stress.

Higher soil moisture increases microclimate temperature buffering in temperate broadleaf forests

Forest canopies can buffer the understory against temperature extremes, often creating cooler microclimates during warm summer days compared to temperatures outside the forest. The buffering of maximum temperatures in the understory results from a combination of canopy shading and air cooling through soil water evaporation and plant transpiration. Therefore, buffering capacity of forests depends on canopy cover and soil moisture content, which are increasingly affected by more frequent and severe canopy disturbances and soil droughts. The extent to which this buffering will be maintained in future conditions is unclear due to the lack of understanding about the relationship between soil moisture and air temperature buffering in interaction with canopy cover and topographic settings. We explored how soil moisture variability affects temperature offsets between outside and inside the forest on a daily basis, using temperature and soil moisture data from 54 sites in temperate broadleaf forests in Central Europe over four climatically different summer seasons. Daily maximum temperatures in forest understories were on average 2 °C cooler than outside temperatures. The buffering of understory temperatures was more effective when soil moisture was higher, and the offsets were more sensitive to soil moisture on sites with drier soils and on sun-exposed slopes with high topographic heat load. Based on these results, the soil–water limitation to forest temperature buffering will become more prevalent under future warmer conditions and will likely lead to changes in understory communities. Thus, our results highlight the urgent need to include soil moisture in models and predictions of forest microclimate, understory biodiversity and tree regeneration, to provide a more precise estimate of the effects of climate change.

Linking horizontal crosshole GPR variability with root image information for maize crops

AbstractNon‐invasive imaging of processes within the soil–plant continuum, particularly root and soil water distributions, can help optimize agricultural practices such as irrigation and fertilization. In this study, in‐situ time‐lapse horizontal crosshole ground penetrating radar (GPR) measurements and root images were collected over three maize crop growing seasons at two minirhizotron facilities (Selhausen, Germany). Root development and GPR permittivity were monitored at six depths (0.1–1.2 m) for different treatments within two soil types. We processed these data in a new way that gave us the information of the “trend‐corrected spatial permittivity deviation of vegetated field,” allowing us to investigate whether the presence of roots increases the variability of GPR permittivity in the soil. This removed the main non‐root‐related influencing factors: static influences, such as soil heterogeneities and rhizotube deviations, and dynamic effects, such as seasonal moisture changes. This trend‐corrected spatial permittivity deviation showed a clear increase during the growing season, which could be linked with a similar increase in root volume fraction. Additionally, the corresponding probability density functions of the permittivity variability were derived and cross‐correlated with the root volume fraction, resulting in a coefficient of determination (R2) above 0.5 for 23 out of 46 correlation pairs. Although both facilities had different soil types and compaction levels, they had similar numbers of good correlations. A possible explanation for the observed correlation is that the presence of roots causes a redistribution of soil water, and therefore an increase in soil water variability.

Quantifying links between topsoil depth, plant water use, and yield in a rainfed maize field in the U. S. Midwest

Agricultural production in highly variable soils is a challenge, especially when those soils are shallow. Precision agriculture techniques were developed to improve yields and minimize spatial and interannual variability in profit. In the Central Claypan region of the Midwest United States, many of the precision agriculture techniques were based on the assumption that topsoil depth controlled plant available water, and therefore yield. But this assumption has not been empirically tested. In this study, we use measurements of sap flow installed on maize plants with a gradient in topsoil depth, caused by a claypan layer. We hypothesize that plants with higher water use have higher yield, plants in areas with thicker topsoil have higher water use, and soils in the areas with thicker topsoil have higher soil water content. Sap flow sensors were installed on 5 plants each at three locations with topsoil depths of 19.6 cm (shallow), 21.6 cm (medium), and 30.5 cm (deep) from June – September, 2022. An ANOVA analysis demonstrates that the average total season transpiration at the deep site (279 mm) was significantly larger than at the shallow site (151 mm), while the medium site was in the middle with transpiration not significantly different from either shallow or deep sites (218 mm). At the end of the season, the plants were harvested and total biomass and grain yield were measured. Increase in plant transpiration was significantly related to both increases in biomass and yield. Finally, we measured volumetric soil water content at each location and found higher soil water content at the site with thicker topsoil. Our results demonstrate the link between topsoil depth, soil water content, plant transpiration, and yield. These findings will help improve precision agriculture techniques in areas with highly variable topsoil thickness.

Artificial light at night (ALAN) causes shifts in soil communities and functions.

Artificial light at night (ALAN) is increasing worldwide, but its effects on the soil system have not yet been investigated. We tested the influence of experimental manipulation of ALAN on two taxa of soil communities (microorganisms and soil nematodes) and three aspects of soil functioning (soil basal respiration, soil microbial biomass and carbon use efficiency) over four and a half months in a highly controlled Ecotron facility. We show that during peak plant biomass, increasing ALAN reduced plant biomass and was also associated with decreased soil water content. This further reduced soil respiration under high ALAN at peak plant biomass, but microbial communities maintained stable biomass across different levels of ALAN and times, demonstrating higher microbial carbon use efficiency under high ALAN. While ALAN did not affect microbial community structure, the abundance of plant-feeding nematodes increased and there was homogenization of nematode communities under higher levels of ALAN, indicating that soil communities may be more vulnerable to additional disturbances at high ALAN. In summary, the effects of ALAN reach into the soil system by altering soil communities and ecosystem functions, and these effects are mediated by changes in plant productivity and soil water content at peak plant biomass. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Porous fiber materials can alleviate the risk of farmland drought and flooding disasters and prompt crop growth.

Floods and droughts on farmland seriously damage agricultural production. Porous fiber materials (PFM) made from mineral rocks have high porosity, permeability, and water retention and are utilized widely in green roofs and agricultural production. Therefore, studying the impact of PFM on the improvement of farmland is of great importance for soil and water conservation. We set 64 extreme rainfalls to analyze the impact of PFM on soil water content (SWC), runoff, nutrient loss, microorganism, and plant growth. The results showed that PFM can effectively reduce runoff and improve soil water distribution, and enhance the soil water holding capacity. Furthermore, PFM reduced the loss of nitrogen and phosphorus by 18.3% to 97% in the runoff, and the soil erosion of summer corn was more strongly influenced by lower vegetation cover, compared with winter wheat. Finally, when PFM was buried in the soil, the wheat yield increased by -6.7%-20.4%, but the corn yield in some PFM groups decreased by 5.1% to 42.5% under short-duration irrigation conditions. Our study emphasizes that the effectiveness of PFM depends mainly on the following: First, PFM with high porosity can increase soil water holding capacity and timely replenish the water lost from the surrounding soil. Second, PFM with high permeability can increase infiltration during rainfall and decrease runoff and nutrient loss, reducing the risk of farmland flooding and pollution. Finally, PFM consists of gold ions and alkali metal oxides, which can stabilize agglomerates and improve soil enzyme activity, thereby increasing the relative abundance of some microbial strains and promoting crop growth. However, when the rainfall amount was low or PFM volume was large, PFM could not store water sufficiently during rainfall, which seriously reduced the maximum saturated moisture content and water absorption performance. Meanwhile, the PFM could not release water in time and replenish the soil water deficit, which increased drought risk. In conclusion, the appropriate volume of PFM and irrigation system may enhance soil water storage capacity, minimize agricultural pollution, and promote crop production.

Photodegradation modifies microplastic effects on soil properties and plant performance

Abstract Microplastics (MPs) in soil affect plant–soil systems depending on their shape and polymer type. However, previous research has not yet considered the effects of degraded plastics, which are the plastic materials actually present in the environment. We selected eight MPs representing different shapes (fibres, films and foams) and polymer types, and exposed them to UV‐C degradation. Each MP was mixed with soil at a concentration of 0.4% (w/w). The phytometer Daucus carota grew in each pot. At harvest, soil properties and plant biomass were measured. Photodegradation altered MP physical and chemical properties, impacting plant–soil systems. MP degradation effects on plant and soil were observed with fibres and foams, but there were negligible effects with films. The latter could be explained by the polymer structure of films and manufacturer's additives, potentially delaying their degradation. Degraded fibres increased soil respiration more than their non‐degraded counterparts, as photodegradation increased the positive effects of fibres on soil water retention. The emergence of oxygenated groups during degradation may have increased the hydrophilicity of fibres, enhancing their ability to retain water. Degraded foams increased soil respiration, which could be related to the possible leaching of organic substances with lower partition coefficients, which may promote soil microbial activity. In contrast, degraded foams decreased soil aggregation, likely as degradation produced larger holes increasing their permeability. Also, the increase in hydrophilic molecules could have decreased soil particle cohesiveness. Degraded fibres and foams increased shoot and root mass as a result of MP effects on soil properties. Photodegraded MPs affected root traits, which could be linked to MP effects on soil water status and plant coping strategies. Synthesis and applications. Photodegradation can intensify the effects that microplastics (MPs) have on plant–soil systems, which would have frequently been underestimated had we only worked with pristine MPs. Plastic companies, agricultural practitioners and researchers should consider that plastics are being degraded as they enter the soil. Policies should promote practices to minimize MP accumulation in soils and ensure their proper disposal.

Neutral effect of nitrogen addition and negative effect of precipitation reduction on the soil faunal community in a temperate forest

ABSTRACT Nitrogen deposition can promote belowground soil carbon pools, and precipitation reduction can eliminate this positive effect. Soil fauna play crucial roles in regulating the dynamics of organic matter and maintaining biodiversity in ecosystems. However, it is not clear whether belowground soil fauna have similar responses to changes after long-term nitrogen deposition and drought. We simulated nitrogen deposition by applying fertilizer, and simulated drought by excluding 30% of the ambient precipitation in a temperate forest from 2009. Our results showed that experimental precipitation reduction alone significantly changed the composition and decreased the abundance of the soil faunal community. Precipitation reduction could also promote the soil food web in a fungal-dominated pathway by decreasing trophic groups of Isotomidae abundance. In contrast, although nitrogen addition treatment increased soil available nitrogen content, it had a neutral effect on the soil faunal community. Soil faunal community showed strong temporal variations in response to both nitrogen deposition and precipitation reduction treatments. Notably, interactions between precipitation reduction, nitrogen addition, and sampling time were significant for specific trophic groups, including saprozoites and omnivores. Shannon-Weiner diversity was not sensitive to these global change factors. Our results suggest that soil water content and plant richness may, directly and indirectly, regulate the soil faunal community.

Integrative effect of activated biochar to reduce water stress impact and enhance antioxidant capacity in crops

Biochar is a soil amendment that can change soil's physical and hydraulic properties. However, biochar application is far from being a ‘one size fits-all’ approach. The impact of the management practices is dependent on biochar type (feedstock and production conditions), application depth and method, climate and site characteristics. Hence, this study aims to enrich the available inconclusive information on how biochar could affect clay loamy soil and to assess the potential impact of the induced change on water stress mitigation of rain-fed durum wheat under the specific condition of the semi-arid environment of North West of Tunisia. A field experiment was investigated in which three biochar rates 0 (B0), 10 (equivalent to 0.5% of weight) (B1) and 20 t/ha (equivalent to 1% of weight), (B2), were tested. Other laboratory analysis allowed the evaluation of soil water retention curve (SWRC), saturated hydraulic conductivity (Ks), dry density (ρb) and biostress biomarkers such as glutathione-S-transferase (GST), catalase activities (CAT) and malondialdehyde content (MDA) as well as yield attributes. Results showed that treatment B2 significantly decreased ρb and Ks with relative change values of about −3.1% and −19%. Consequently, SWRC showed a better water retention capacity, mostly from saturation to matric potential value (h) of 33 kPa. Total (TAWC), plant (PAWC) and readily (RAWC) available water contents, significantly increased under B2 with relative changes of +6%, +44% and +44% respectively. Moreover, GST and CAT were also boosted under B2. Consequently, biological and grain yields as well as grain water use efficiency (GWUE) significantly increased. GWUE increased from 0.81 ± 0.04 in B0 to 1.09 ± 0.01 kg/m3 in B2. The correlation analysis showed a significant and positive correlation, between GWUE and soil water parameters (θs, θfc and θmre) suggesting the indirect effect of biochar on water-use efficiency for grain yield of wheat. Therefore, among the tested rates 20 t/ha could be suggested to improve plant soil water availability and reduce the harmful impact of drought stress on rain-fed durum wheat.

Impact of Drought on Ecohydrology of Southern California Grassland and Shrubland

Through their rooting profiles and water demands, plants affect the distribution of water in the soil profile. Simultaneously, soil water content controls plant development and interactions within and between plant communities. These plant-soil water feedbacks might vary across plant communities with different rooting depths and species composition. In semiarid environments, understanding these differences will be essential to predict how ecosystems will respond to drought, which may become more frequent and severe with climate change. In this study, we tested how plant-soil water feedbacks responded to drought in two contrasting ecosystem types—grassland and shrubland—in the coastal foothills of southern California. During years 5–8 of an ongoing precipitation manipulation experiment, we measured changes in plant communities and soil moisture up to 2 m depth. We observed different water use patterns in grassland and shrubland communities with distinct plant functional types and water use strategies. Drought treatment did not affect perennial, deep-rooted shrubs because they could access deep soil water pools. However, mid-rooted shrubs were sensitive to drought and experienced decreased productivity and die-off. As a result, water content actually increased with drought at soil depths from 50–150 cm. In grassland, biomass production by annual species, including annual grasses and forbs, declined with drought, resulting in lower water uptake from the surface soil layer. An opportunistic “live fast, die young“ life strategy allowed these species to recover quickly once water availability increased. Our results show how drought interacts with plant community composition to affect the soil water balance of semiarid ecosystems, information that could be integrated into global scale models.

Effects of several polymeric materials on the improvement of the sandy soil under rainfall simulation

Poor cementation between soil particles is a fundamental cause of soil erosion and desertification. In recent decades, many polymers have been used to cement soil particles and improve the physical and chemical properties of soils. The contributions of polymers with different structures and functional groups to soil improvement vary considerably. In this study, a mixture comprising polyacrylamide (PAM), sodium polyacrylate (PAAS), hydroxypropyl methylcellulose (HPMC), and polyvinyl alcohol (PVA) was investigated to meet the requirements of soil water retention, erosion resistance, and plant growth. The results showed that the time required for the modified soil to reach drought conditions was extended by 4–7 days. The PAM/HPMC, PAM/PVA and PAM/PAAS experimental groups reduced the erosion rate by 99.57%, 98.3% and 96.38%, respectively, compared to that of the control group. The belowground plant biomass was significantly increased by PAM/HPMC, PAM/PAAS, and PAM/PVA, with increases of 115.92%, 145.23%, and 205.67%, respectively. HPMC contributed more to the soil erosion resistance and water-holding capacity, PAAS improved the soil porosity substantially, and PVA significantly increased the plant biomass. The rigid structures of the polymer chains enhanced the structural stability of the soil, and the hydrophilic functional groups increased the hydrophilicity of the amended soil. This study indicates different polymers that may be used to improve soil properties.

Seasonal variations and sources of the dew from stable isotopes in alpine meadows

AbstractThe dew is closely related to the micro‐use water of plants and the large‐scale hydrological processes, its formation on grassland plays a vital role especially in maintaining the eco‐hydrological cycle. We used structural equation modelling to investigate how environmental factors would affect dew formation on alpine graminoid‐Kobresia meadow in northern Qinghai‐Tibet Plateau. The stable isotope information of dew, ambient vapour, soil water, plant water, creek water and precipitation were tracked to explore the source of dew, the dew transport route of the six dominant species by Mix SIAR model. Our results showed that the frequency of dew on the graminoid‐Kobresia meadow in 2020 and 2021 was 42.86% and 45.83%, respectively. Both atmospheric pressure (r = 0.4) and temperature (r = 0.382) showed significant positive effects dew formation while wind speed (r = −0.309) had a negative effect. The contribution rates of soil water, plant water and ambient water vapour to dew were 48.20 ± 5.46%, 38.30 ± 5.07%, and 13.50 ± 1.82%, respectively. The proportion of dew utilization in the dominant species had no significant species differences. Our results provided an improved understanding of dew formation based on isotope technology on alpine meadow in northern Qinghai‐Tibet Plateau.