Search Results (49)

This study analyzes the dynamics of temperature and moisture in a cylindrical silo with a conical roof and floor used for storing corn in the Bajío region of Mexico, considering conditions both with and without aeration. The model incorporates external temperature fluctuations, solar radiation, grain moisture equilibrium with air humidity through the sorption isotherm (water activity), and grain respiration to simulate real storage conditions. The model is based on continuity, momentum, energy, and moisture conservation equations in porous media. This model was solved using the finite element method (FEM) to evaluate temperature and interstitial humidity variations during January and May, representing cold and warm environmental conditions, respectively. The simulations show that, without aeration, grain temperature progressively accumulates in the center and bottom region of the silo, reaching critical values for safe storage. In January, the low ambient temperature favors the natural dissipation of heat. In contrast, in May, the combination of high ambient temperatures and solar radiation intensifies thermal accumulation, increasing the risk of grain deterioration. However, implementing aeration periods allowed for a reduction in the silo’s internal temperature, achieving more homogeneous cooling and reducing the threats of mold and insect proliferation. For January, an airflow rate of 0.15 m³/(min·ton) was optimal for maintaining the temperature within the safe storage range (≤17 °C). In contrast, in May, neither this airflow rate nor the accumulation of 120 h of aeration was sufficient to achieve optimal storage temperatures. This indicates that, under warm conditions, the aeration strategy needs to be reconsidered, assessing whether a higher airflow rate, longer periods, or a combination of both could improve heat dissipation. The results also show that interstitial relative humidity remains stable with nocturnal aeration, minimizing moisture absorption in January and preventing excessive drying in May. However, it was identified that aeration period management must be adaptive, taking environmental conditions into account to avoid issues such as re-wetting or excessive grain drying. Full article

Wetlands frequently experience drying and rewetting (DRW) alternation, which intricately influences the physical, chemical, and biological processes within the soil matrix. The conversion of agricultural land into wetland ecosystems has raised significant concerns regarding the release of phosphorus. However, a significant knowledge gap persists in understanding the implications of this phenomenon for phosphorus transformation and release dynamics within soils situated in the freeze–thaw zone of Northeast China. To address this gap, we conducted a series of experiments involving the simulation of varying intensities and frequencies of DRW alternation using soil column samples collected from restored wetlands. This study evaluated phosphorus fractions with different levels of mobility and availability using methods based on standardized chemical extraction. We subsequently analyzed the impacts of these alterations on phosphorus fractions from the perspectives of soil chemical properties and microbial community changes. DRW events were found to facilitate the conversion of labile inorganic phosphorus into organic phosphorus fractions, driving the transformation of mobile phosphorus into potentially mobile fractions. Moderate drought events showed a significant increase in soil bacterial diversity and abundance, while both normal and extreme drought events caused a decrease in bacterial diversity. Moreover, DRW treatment increased the relative abundance of Proteobacteria and decreased the relative abundance of Chloroflexi. Redundancy analysis identified organic carbon and bacterial diversity as key drivers influencing phosphorus fractions. Overall, this study contributes to our understanding of the intricate relationships among soil characteristics, microbial ecosystems, and the complex behavior of phosphorus under various DRW regimes in restored wetlands. Full article

Oxidation of methane by soil microorganisms is an important mechanism controlling the content of this potent greenhouse gas in the atmosphere. Agricultural soils operate under stressful conditions, and ammonium (N-fertilization) and drying (global warming) may have a significant impact on methane oxidation. In order to investigate how soil methanotrophs respond to drying–rewetting (DW), ammonium addition (100 mg/g) (A), and their combined action (MS), agricultural soil microcosms were incubated over the three months and methane oxidation was measured before and after perturbations, while community composition was monitoring using 16S rRNA gene sequencing. A significant decline in the methane-oxidation activity after perturbations was found, with subsequent restoration, and the combined treatment was more effective than the sum of individual treatments, indicating a synergistic effect. After rewetting, the structure of the bacterial community returned to pre-dry-down levels, but the application of ammonia and combined action lead to irreversible changes in the structure of soil methanotrophic communities. Methanotroph Methylomicrobium were significantly reduced under disturbances, while there was a significant increase in the representation of Methylobacter accompanied by the facultative methylotroph Methylovorus. We concluded that methanotrophic communities in agricultural soil demonstrated flexibility, and even when the abundance of dominant populations drops, ecosystem functions can recover. Full article

Drying and rewetting of soil stimulates soil carbon emission. The Birch effect, driven by these cycles, leads to CO₂ efflux, which can be monitored using real-time mass spectrometry (RTMS). Although soil fungi retain water during droughts, their contribution to CO₂ release during drying–rewetting cycles remains unclear. In this study, we present the first demonstration of integrating micromodels with RTMS to monitor the Birch effect by simulating drought and rewetting. Micromodels were inoculated with axenic fungal culture and dried to assess moisture retention. After drying, RTMS quantified CO₂ release upon rewetting with H₂¹⁸O mixtures. Our results showed that soil fungi released CO₂ upon rehydration and immediately utilized the external water source at the pore scale by generating subsequent ⁴⁶CO₂. This work is the first to integrate RTMS with microsystems to investigate pore-scale biogeochemistry and the involvement of fungi in the Birch effect. Full article

Studies of the impact of nitrification inhibitors (NIs), specifically DMPP and DMPSA, on N₂O emissions during “hot moments” have produced conflicting results regarding their effectiveness after rewetting. This study aimed to clarify the effectiveness of NIs in reducing N₂O emissions by assessing residual DMP concentration and its influence on ammonia-oxidizing bacteria (AOB) in two pot experiments using calcareous (Soil C, Calcic Haploxerept) and acidic soils (Soil A, Dystric Xerochrepts). Fertilizer treatments included urea (U), DMPP, and DMPSA. The experiments were divided into Phase I (water application to dry period, 44 days) and Phase II (rewetting from days 101 to 121). In both phases for Soil C, total N₂O emissions were reduced by 88% and 90% for DMPP and DMPSA, respectively, compared with U alone. While in Phase I, the efficacy of NIs was linked to the regulation of AOB populations, in Phase II this group was not affected by NIs, suggesting that nitrification may not be the predominant process after rewetting. In Soil A, higher concentrations of DMP from DMPP were maintained compared to Soil C at the end of each phase. Despite this, NIs had no significant effect due to low nitrification rates and limited amoA gene abundance, indicating unfavorable conditions for nitrifiers. The study highlights the need to optimize NIs to reduce N₂O emissions and improve nitrogen efficiency, while understanding their interactions with the soil. This knowledge is necessary in order to design fertilization strategies that improve the sustainability of agriculture under climate change. Full article

The summer drought in the United Kingdom (UK) in 2022 produced significant speculation concerning how its termination may impact and interact with the soil resource. Whilst knowledge regarding soils and droughts exists in the scientific literature, a coherent understanding of the wider range of impacts on soil properties and functions has not been compiled for temperate soils. Here, we draw together knowledge from studies in the UK and other temperate countries to understand how soils respond to drought, and importantly what and where our knowledge gaps are. First, we define the different types of droughts and their frequency in the UK and provide a brief overview on the likely societal impacts that droughts place on the soil and related ecosystems. Our focus is on ‘agricultural and ecosystem drought’, as this is when soils experience dry periods affecting crops and ecosystem function, followed by rewetting. The behaviour of moisture in soils and the key processes that contribute to its storage and transport are examined. The principal changes in the physical, chemical, and biological properties of soils resulting from drought, and rewetting (i.e., drought termination) are discussed and their extensive interactions are demonstrated. Processes that are involved in the rewetting of soils are explored for soil and catchment-scale soil responses. Lastly, soils’ recovery after drought is considered, knowledge gaps are identified, and areas to improve understanding are highlighted. Full article

Cocksfoot (Dactylis glomerata L.) is becoming increasingly important for grassland farming due to climate change, which alters precipitation and increases droughts. Although it is generally considered to be drought-tolerant, little is known about the differences between cultivars. This study aimed to investigate the effects of four different field capacity (FC) levels (80%, 60%, 40%, and rewetting to 80% after a period of 40% FC) on the yield, crude protein content, water consumption, water use efficiency (WUE), and drought susceptibility index of five European cocksfoot cultivars (cv). A pot experiment was conducted in a greenhouse subjected to the specified irrigation treatments over three growth periods. The results revealed significant differences in the cultivars’ responses to the irrigation treatments. Dry matter yield decreased under simulated drought conditions, while crude protein content and WUE increased. Prolana cv achieved the highest yield under drought conditions, Tandem cv had the highest WUE, and Laban cv exhibited the highest crude protein content. Rewetting to 80% FC in the last growth period resulted in similar dry matter and crude protein yields for all cultivars compared to full irrigation. These findings highlight the importance of selecting and breeding drought-tolerant cocksfoot cultivars to maintain high yields and quality in perennial grassland farming under future climate conditions. Full article

The temperature and moisture content inside a grain pile are two important indicators for judging the safety of grain storage. To accurately predict the temperature and moisture content inside a grain pile, a numerical simulation was carried out of the drying process of a mesoscale wheat grain soil based on a thin-layer drying method, considering non-uniform porosity. The effectiveness of this method for wheat piles was verified through a comparison with the experimental data. The influence of different ventilation cage heights and ventilation temperatures on heat and moisture transfer in the wheat grain pile were also studied. The results show the following points. The numerical simulation method in this paper can effectively predict the temperature and moisture content of a wheat grain pile. The non-uniform porosity distribution model can better reproduce the state of ventilation during storage of wheat grain piles than the uniform porosity distribution model. The distribution patterns of flow lines in silos with different ventilation cage heights have certain similarities, but the high-speed airflow area will decrease as the height of the ventilation cage increases. Different ventilation temperatures will significantly affect the areas of high temperature and the rewetting inside a wheat grain pile. Full article

Because methane is a potent greenhouse gas (GHG), understanding controls on methane emissions from reservoirs is an important goal. Yet, reservoirs are complex ecosystems, and mechanisms by which reservoir operations influence methane emissions are poorly understood. In part, this is because emissions occur in ‘hot spots’ and ‘hot moments’. In this study, we address three research questions, ‘What are the causal pathways through which reservoir operations and resulting water level fluctuations (WLF) influence methane emissions?’; ‘How do influences from WLF differ for seasonal drawdown and diurnal hydropeaking operations?’; and ‘How does understanding causal pathways inform practical options for mitigation?’. A graphical conceptual model is presented that links WLF in reservoirs to methane emissions via four causal pathways: (1) water-column mixing (2) drying–rewetting cycles, (3) sediment delivery and redistribution, and (4) littoral vegetation. We review what is known about linkages for WLF at seasonal and diurnal resolutions generate research questions, and hypothesize strategies for moderating methane emissions by interrupting each causal pathway. Those related to flow management involve basin-scale management of tributary flows, seasonal timing of hydropeaking (pathway #1), timing and rates of drawdown (pathway #2). In addition, we describe how sediment (pathway #3) and vegetation management (pathway #4) could interrupt linkages between WLF and emissions. We demonstrate the strength of conceptual modeling as a tool for generating plausible hypotheses and suggesting mitigation strategies. Future research is needed to develop simpler models at appropriate timescales that can be validated and used to manage flow releases from reservoirs. Full article

Microbial response to changing environmental factors influences the fate of soil organic carbon, and drought has been shown to affect microbial metabolism and respiration. We hypothesized that the access of microbes to different carbon pools in response to dry–rewet events occurs sequentially at different rates. We amended desiccated soils with ¹³C-labeled glucose and measured the rates of ¹²CO₂ and ¹³CO₂ respiration in real time after rewetting. Using these differentiated ¹²CO₂ and ¹³CO₂ respiration rate soils after rewetting, we were able to deduce when microbes are accessing different pools of carbon. Immediately upon rewetting, respiration of ¹²CO₂ occurred first, with negligible ¹³CO₂ respiration. Appreciable metabolism and respiration of the added ¹³C glucose did not occur until 15 min after rewetting. We conclude that, while all carbon pools are being accessed in the first 9 h after rewetting, the rate and timing at which new and existing carbon pools are being accessed varies. Within this study, using stable isotope-labeled substrates to discern which carbon pools are metabolized first uniquely illustrates how microorganisms access different carbon pools which has implications into understanding how carbon metabolism can further affect climate, carbon sequestration, and soil health. Full article

The solar drying process is a critical postharvest stage for preserving coffee quality and is widely used in coffee-producing countries. A descriptive exploratory study was carried out in zones with different annual solar brightness to determine the climate variability influence on solar drying. Variables related to the evolution of drying, physical and sensory quality, and the physicochemical characteristics of the Castillo^® coffee variety were analyzed. Coffee quality was assessed by means of SCA protocol. An automatic system was designed to record variables inside the dryers and mass loss. The drying rates were different by climatic zone above and below 0.52%∙h⁻¹. Drying time was significantly longer in less solar brightness zones (Wilcoxon test). An inverse linear relationship between rewetting percentage and bean moisture was observed. Regarding coffee quality, the average scores were 81.37 and 80.93 SCA points for the climatic zones with the lowest and highest solar brightness, respectively. The bean color, water activity, acidity, and fat content did not vary between climatic zones. The coffee quality was not affected by solar drying in contrasting climatic conditions, despite the differences in drying time. Solar drying behaviors were identified that allow for the development of strategies for improving the process efficiency and management of coffee. Full article

Greenhouse gas (GHG) emissions from paddy fields depend on water management practices and rice varieties. Lysimeter experiments were conducted to determine the effect of rice varieties (lowland; Koshihikari (KH) and upland; Dourado Precoce (DP)) on GHG emissions under two water management practices: alternate wetting and drying (AWD) and continuous flooding (CF). A repeated cycle of drying and wetting in AWD irrigation was performed by drying the soil to −40 kPa soil matric potential and then rewetting. Consequently, the closed chamber method was used to measure direct emissions of methane (CH₄), nitrous oxide (N₂O), and carbon dioxide (CO₂). The result revealed that water management significantly affected CH₄ and N₂O emissions (p < 0.05), while no significant effect was observed between different rice varieties. Although, AWD irrigation reduced CH₄ emissions, it increased N₂O emissions compared to CF irrigation, likely due to increased oxygen supply. AWD irrigation decreased GWP by 55.6% and 59.6% in KH and DP, respectively, compared to CF irrigation. Furthermore, CH₄ and N₂O emissions significantly correlated with soil redox potential and volumetric water content. These results suggest that AWD irrigation might be an effective water management method for mitigating GHG emissions from rice fields in central Japan. Full article

The conversion of cultivated fen peat soils into rewetted soils can mitigate global climate change. Specifically, carbon in newly formed peat can store atmospheric CO₂ for a long time in soil, but alterations in the quality of soil organic matter are not well known. To shed light on the complex processes of peat degradation or new formation under dry or rewetting conditions, we investigated and quantified saturated n-alkyl acids as an indicator compound class of peatlands response to the contrasting management practices. The concentrations of saturated n-alkyl acids from two soil layers of the drained and rewetted were determined in two soil layers of drained and rewetted fenland types such as Alder Carr forest, coastal peatland, and percolation mire. The analytical methods were solvent extraction, methylation with tetramethylammonium hydroxide, and gas chromatography/mass spectrometry. The saturated n-alkyl acid distribution pattern showed that the concentrations of long C-chain lengths were larger by factors of up to 28 relative to the short C-chain lengths. The effect of rewetting was reflected by the ratios of the summed concentrations of long (n-C_21:0 to n-C_34:0) to short (n-C_10:0 to n-C_20:0) C-chain saturated n-alkyl acids for drained and rewetted peat soil samples. These ratios were consistently lower in samples from the rewetted sites, indicating a higher input of microbial bio- and necromass to soil organic matter, likely from algae and anaerobic bacteria, under rewetting. The results suggest that the enrichment of microbial biomass and necromass in rewetted soils may be an important contributor to the formation of new peat in fenlands, irrespective of fenland type. Full article

Bareroot European beech (Fagus sylvatica L.) seedlings are frequently used in reforestation programs in Central Europe. However, beech outplanting is often unsuccessful due to drought stress. In this study, the effects of a simulated water deficit and of a hydrogel and ectomycorrhizal fungi (EMF) application were estimated on the development of 1 + 1 beech seedlings. The roots of 1-year-old bareroot seedlings were treated with the additives at the time of transplanting to pots in spring and then exposed to the whole growing season under different watering regimes: (i) full watering (FW; volumetric water content 70%), (ii) reduced watering (RW; 40%), (iii) periodic watering (PW; substrate rewetted to 70% after drying), and (iv) no watering (NW). Almost all FW seedlings survived the whole growing season, whereas all NW seedlings died after 17 weeks of desiccation. The survival and growth of FW and NW seedlings were significantly higher and lower, respectively, than those under both PW and RW treatments. The additives significantly increased survival in RW seedlings only but had no effect on growth. A promoting effect of FW on the chlorophyll a fluorescence parameters was found. The number and EMF colonization of the short roots were significantly lower in FW seedlings compared to the other watering treatments. The additives did not affect these parameters. The occurrence of neither treatment-specific EMF root morphotype nor fungi applied in the inoculum and traced by molecular analysis indicated the formation of ectomycorrhizas with native EMF in all treatments. The seedlings in the water-deficient treatments exhibited higher foliar nutrient concentrations than FW seedlings. The additives increased the concentration of nutrients in PW and phosphorus in NW seedlings. The results suggest the significant effect of the water supply, but a weaker effect of the additives tested on beech seedling development under experimental conditions. Full article

The interplay of surface and shallow subsurface fluxes plays a critical role in controlling water movement in hillslope agroecosystems and impacting soil and plant health during prolonged dry periods, demonstrating a need for in-field monitoring. This study was conducted for two years (2021–2022) by combining field monitoring of the grass-covered inter-row area (passive wick lysimeter, surface runoff, and meteorological data), laboratory determination of soil hydraulic properties (SHPs), and numerical modeling with the aim to explore near-surface fluxes at the SUPREHILL Critical Zone Observatory (CZO) located on a hillslope vineyard. Additionally, sensitivity analysis for basic root water uptake (RWU) parameters was conducted. The model was evaluated (R², RMSE, and NSE) with lysimeter (hillslope) and runoff (footslope) data, producing good agreement, but only after the inverse optimization of laboratory estimated hydraulic conductivity was conducted, demonstrating that adequate parameterization is required to capture the hydropedological response of erosion-affected soil systems. Results exhibit the dependence of runoff generation on hydraulic conductivity, rainfall, and soil moisture conditions. The data suggest different soil-rewetting scenarios based on temporal rainfall variability. Sensitivity analysis demonstrated that Leaf Area Index (LAI) was the most responsive parameter determining the RWU. The study offers an approach for the investigation of fluxes in the topsoil for similar sites and/or crops (and covers), presenting the methodology of self-constructed soil–water collection instruments. Full article