Maximum Soil Temperature Research Articles

Evaluation of the long-term performance of the deep U-type borehole heat exchanger on different geological parameters using the Taguchi method

In recent years, deep geothermal energy has become a solid option for building heating worldwide. For the densely populated urban area, a novel closed-loop system of the deep U-type borehole heat exchanger (DUBHE) has attracted attention in northern China. In order to achieve the evaluation of geological parameters on the long-term performance of DUBHE, thermal conductivity, geothermal gradient, specific heat capacity, groundwater flow direction, and Darcy velocity are selected in this paper and all the parameters are set in three levels. And orthogonal test L18(35) is established by adopting the Taguchi method for the reduction of simulation time cost. Three evaluation indexes are introduced to investigate the impacts of geological parameters on the performance of DUBHE and obtain the optimal set, including average outlet temperature Tout, maximum cumulative heat extraction amount Qtotal and soil temperature decay rate Dsoil. Results show that the geothermal gradient has the most significant effect on Tout and Qtotal, and its contribution degree is 70.14% and 62.10% respectively. As for the Dsoil index, the most influential parameter is specific heat capacity and the corresponding contribution ratio is 92.41% determined by the analysis of variance (ANOVA) method. For the optimized combination by adopting matrix analysis, the Tout reaches 33.92°C, the Qtotal is 284.08TJ and the Dsoil of the optimized scenario is 12.66% after the long-term operation. In addition, according to the orthogonal test results, this study intuitively discusses the potential of carbon emission reduction for the DUBHE under the typical geological conditions in northern China. The study results presented in this work can guide the system design of DUBHE and serve as the reference for the decision-maker in the application of deep geothermal heating technology.

Response of Soil Moisture to Infrequent Heavy Defoliation of Chemically Thinned Juniper Woodland

In semiarid regions of the western United States, there is heightened interest in tree removal to increase water availability for other uses such as forage growth and groundwater recharge. This study was conducted in central New Mexico to determine the effects of heavy infrequent defoliation of chemically thinned juniper woodland (Juniperus monosperma) on soil moisture. Each of three cattle-grazing exclosures (CD, FG, and KI) was instrumented: 1) beneath trees with a set of three soil moisture probes (0−25, 25−50, and 50−75 cm depth) and one soil temperature probe under live trees (control) and dead trees (herbicide-treated); and 2) between trees with one soil moisture and one soil temperature probe in control and herbicide-treated intercanopy plots. Each plot had three clipped and three unclipped subplots. Mean daily maximum surface soil temperature was highest (17.19°C) in intercanopy, intermediate (16.13°C) under herbicide-treated, and lowest (14.90°C) under control trees. Topsoil moisture (0−25 cm depth) was different among treatment combinations from late July to early September 2006. Thus, the control unclipped combination had the highest topsoil moisture while the herbicide-treated unclipped combination had the lowest topsoil moisture. Comparing other depths, control unclipped plots had higher soil moisture in the middle layer (25−50 cm) and bottom layer (50−75 cm) than at the top from late August to early November 2006. Results imply that clipping on chemically thinned juniper woodlands does not increase soil moisture at any depth, yet macropore flow and water absorption on deep soil layers, underneath live trees, might help to store soil moisture for longer periods in water-limited environments.

Effects of heat waves on soil temperatures in Slovenia

Soil temperature regulates the rate of plant growth and tells us much about the climatic characteristics of a particular site. Climate variability and extremes need to be studied and there is a large gap in knowledge about soil temperature during heat waves. Agricultural land is highly dependent on heat waves, which are becoming longer, more intense and more frequent, and it is important to monitor soil temperatures in situ to understand their changes during heat waves. Therefore, the aim of this work was to investigate how soil temperatures change at different depths during and after heat waves. Average daily air and soil temperature data for the 25-year period 1992-2016 were evaluated at four agrometeorological stations in three climate zones in Slovenia and analyzed during heat waves determined according to the Slovenian definition. During the period 1992-2016, 53 (Lesce) to 76 (Ljubljana) heat waves were identified. Analysis of average air and soil temperatures before, during and after heat waves showed higher responsiveness of the upper part of the soils and an increase in the time lag between maximum air temperature and maximum soil temperature with depth. The maximum temperature during the heat wave was reached on average in three to nine days, depending on the depth. Only in Moderate climate of the hilly region, the average daily temperatures at a depth of 100 cm remained below 20°C during and after the heat wave. The temperature rise in the deeper layers of the soil lasts longer than in the shallower layers.

Three-Dimensional Dynamic Variations of Ground/Air Surface Temperatures and Their Correlation with Large-Scale Circulation Indexes in Southwest China (1980–2019)

Air/soil temperatures play important roles in land–atmosphere interactions. The three-dimensional (temporal, spatial, and vertical) variations of maximum, mean, and minimum ground soil temperature at 0 cm (GSTx, GSTm, and GSTn, respectively), surface air temperature at 2 m (SATx, SATm, and SATn, respectively), and soil–air temperature difference (SATDx, SATDm, and SATDn, respectively) and their potential linkages with large-scale indexes in Southwest China during 1980–2019 were analyzed. Variations of GST and SAT at the majority of stations (pixels) exhibited significant (p ≤ 0.05) warming, albeit at different rates; consequently, SATD exhibited different variation. Moreover, the period of GST, SAT, and SATD was similar in intra-annual and interannual oscillation but was different in interdecadal oscillation. The variation rate of GST, SAT, and SATD exhibited significant (p ≤ 0.05) correlation with elevation, but with different variation gradient. Notably, asymmetric variation of SATDx (downward trend) and of SATDn (upward trend) with elevation was found at elevations >3 km. Wavelet coherence showed that the Atlantic Multidecadal Oscillation is the dominant factor affecting GST and SAT, whereas the Pacific Decadal Oscillation and the North Atlantic Oscillation make the greatest contributions to SATD. It was found that GST, SAT, and SATD exhibit different variations under the effects of global warming, the driving mechanism of which requires further study.

The relationship of some heat parameters of the soil with the maximum soil temperature

Toprak özelliklerinin değişimi, bitki gelişimi için optimum toprak ortamının oluşturulması, toprak oluşum süreçlerinin açıklanması vb. topraktaki maksimum sıcaklıkla ilişkili olup, topraktaki maksimum sıcaklığın teorik ve deneysel olarak belirlenmesi gereklidir. Bu çalışmada, toprağın ısı iletkenliği denkleminin çözümünden elde edilen maksimum toprak sıcaklığının analitik ifadesinin uygulanabilirliği incelenmiştir. Teorik olarak maksimum toprak sıcaklığının, toprak derinliğinin ortalama sıcaklığının, birim alandan geçen ısı miktarının, kütle yoğunluğunun, özgül ısı kapasitesinin ve derinliğin bir fonksiyonu olduğu gösterilmiştir. Toprağın 0-50 cm derinliğinde ölçülen ve hesaplanan maksimum sıcaklıklar sırasıyla 16.6-35.8 °C ve 16.4-38.4 °C aralıklarında; birim alandan geçen ısı miktarı 3.716•106-17.857•106 J m-2 aralığında; özgül ısı kapasitesi ise 950.404 J kg-1 °C-1 olarak saptanmıştır. Ölçülen ve hesaplanan maksimum toprak sıcaklıkları arasındaki ilişki yüksek (R2=0.9106) bulunmuştur. Ayrıca, nispi hatanın 0.012-0.148 aralığında; ortalama nispi hata ise 0.086 olarak tespit edilmiştir.

Three-Dimensional Model of Soil Water and Heat Transfer in Orchard Root Zone under Water Storage Pit Irrigation

To reveal the water and heat transfer characteristics of the orchard soil under water storage pit irrigation and to regulate the distribution of soil water and heat for improving apple quality and increasing yield, a 3D soil water and heat transfer model of orchards under water storage pit irrigation was established. The model not only considered the influences of root water uptake, precipitation, evaporation, and irrigation, but also simulated the infiltration process of the variable water head in the pit according to the principle of mass conservation and introduced the pit coefficient to simulate the difference in radiation in the pit to describe the influence of the pit on the model. Verify and analyze the simulation results. Results showed that the variation trend of simulated soil moisture and heat was consistent with that of measured data. The mean absolute percentage error, root mean square error, and mean absolute deviation were 3.23%, 0.9460, and 0.6984 for soil temperature and 10.05%, 0.0269, and 0.0214 for water content after irrigation, respectively. The simulation results have high accuracy and show that the soil moisture content centers on the pit with an ellipsoid distribution and tends to be uniform over time. The soil temperature was higher in the 4–5 cm area near the soil surface and the wall of pit, and it remarkably changed with time. The intraday variation of soil temperature was mainly affected by atmospheric temperature, but a certain lag was observed compared with the change of atmospheric temperature. With the increase of the irrigation amount, the distribution range of soil moisture content and water high value area increased, while the average and maximum soil temperature decreased. With the increase of irrigation water temperature to 18–24 h after irrigation, the soil temperature in the ellipsoidal area around the pit remarkably increased. The model established in this paper can be used to simulate the hydrothermal status of the soil in the field under water storage pit irrigation. The results prove that the water storage pit irrigation can effectively improve the hydrothermal status of the middle-deep soil and promote the root system of fruit trees to absorb water.

Influence of Climate Changes on Hydrothermal Regime of Dark Gray Podzolized Soil of Western Forest Steppe

Thermal properties of soil are important conditions that determine the nature and intensity of soil processes, but the features of the formation of thermal and water regimes of dark gray podzolized soil of the Ukrainian Forest Steppe are insufficiently studied. The purpose of the presented materials is to highlight the dynamics of the annual course of temperature and humidity of the air and dark gray podzolized soil to determine the peculiarities of the formation of its hydrothermal regime in modern agro-climatic conditions of the Forest Steppe zone. The study of soil temperature was carried out during 2008-2019 in the Rivne region using generally accepted standards and methods (DSTU ISO 11464-2007, DSTU ISO 11465-2001, DSTU B B.2.1-17:2009, DSTU B B.2.1-25:2009). Surface air temperature observations throughout the study period indicate an increase in average annual temperature, and five-year averages of the sum of effective air temperatures above 10°C show tends to increase. The study of the relationship between the temperature of the surface air layer and dark gray soil in the Rivne region confirmed that the correlation of these indicators is linear. Analyzing the dynamics of temperature indicators, it should be noted a significant increase in maximum soil temperatures, due to which there is an increase in average annual temperatures. Detailing of soil warming indicators according to the data of ten years showed that during 2008-2017 the soils warmed up much more than in the average during the whole period of meteorological observations. According to the accepted classification, the studied soils belong to the seasonally freezing type, moderately warm subtype and genus with medium heat supply. The results obtained during the study allow to justify changes in the hydrothermal conditions of dark gray podzolized soil and determine the needs for corrective measures in crop production to maintain sustainable yields and ensure enhanced fertility reproduction

Soil steaming to disinfect barnyardgrass-infested soil masses

AbstractReusing soil can reduce environmental impacts associated with obtaining natural fresh soil during road construction and analogous activities. However, the movement and reuse of soils can spread numerous plant diseases and pests, including propagules of weeds and invasive alien plant species. To avoid the spread of barnyardgrass in reused soil, its seeds must be killed before that soil is spread to new areas. We investigated the possibility of thermal control of barnyardgrass seeds using a prototype of a stationary soil steaming device. One Polish and four Norwegian seed populations were examined for thermal sensitivity. To mimic a natural range in seed moisture content, dried seeds were moistened for 0, 12, 24, or 48 h before steaming. To find effective soil temperatures and whether exposure duration is important, we tested target soil temperatures in the range 60 to 99 C at an exposure duration of 90 s (Experiment 1) and exposure durations of 30, 90, or 180 s with a target temperature of 99 C (Experiment 2). In a third experiment, we tested exposure durations of 90, 180, and 540 s at 99 C (Experiment 3). Obtaining target temperatures was challenging. For target temperatures of 60, 70, 80, and 99 C, the actual temperatures obtained were 59 to 69, 74 to 76, 77 to 83, and 94 to 99 C, respectively. After steaming treatments, seed germination was followed for 28 d in a greenhouse. Maximum soil temperature affected seed germination, but exposure duration did not. Seed premoistening was of influence but varied among temperatures and populations. The relationships between maximum soil temperature and seed germination were described by a common dose–response function. Seed germination was reduced by 50% when the maximum soil temperature reached 62 to 68 C and 90% at 76 to 86 C. For total weed control, 94 C was required in four populations, whereas 79 C was sufficient in one Norwegian population.

Thermal conductivity contrast effect of organic soils and its environmental implications

Thermal conduction control is important for retarding permafrost degradation and mitigating of frost geohazards. Similar to a thermodiode, high thermal conductivity contrast (HTCC) materials can serve as good thermal insulators. A preferred HTCC material for ground cooling is larger in thermal resistance in summer and smaller in winter. Because of contrasting thermal conductivity under frozen and thawed states, organic soil is blessed with such a property. This study quantified and reported the HTCC effects on a range of soil organic matter concentrations (SOMC) and soil moisture saturation degree (SMSD). Using the COMSOL, influences of different SOMC and SMSD on ground temperatures were simulated and compared with laboratory-measured properties. Simulation results demonstrated that with constant SMSD at 20% throughout the year, the thermal insulation effect was strengthened with increasing SOMC. A better insulating effect was judged by lower annual amplitudes and smaller depths of zero annual amplitude of ground temperatures. In case of low SMSD in summer (20%) and high SMSD in winter (60–80%), the HTCC effect of soil is enhanced with increasing SOMC. This enhancement was evidenced by increased thermal offsets and decreased maximum summer and average near-surface soil temperatures. With constant SOMC and increasing SMSD, the rising HTCC effect gradually cools the ground. An integral analysis indicates that the higher the SOMC and SMSD in winter, the larger the thermal offset and the lower the ground temperature, i.e., the greater the HTCC effect of organic soil. This study may provide geocryological bases for engineering and environmental applications in cold regions.

Evidences of soil warming from long-term trends (1951\u20132018) in North Rhine-Westphalia, Germany

Soil temperature (ST) is an important property of soils and driver of below ground biogeochemical processes. Global change is responsible that besides variable meteorological conditions, climate-driven shifts in ST are observed throughout the world. In this study, we examined long-term records in ST by a trend decomposition procedure from eleven stations in western Germany starting from earliest in 1951 until 2018. Concomitantly to ST data from multiple depths (5, 10, 20, 50, and 100 cm), various meteorological variables were measured and included in the multivariate statistical analysis to explain spatiotemporal trends in soil warming. A significant positive increase in temperature was more pronounced for ST (1.76 ± 0.59 °C) compared with air temperature (AT; 1.35 ± 0.35 °C) among all study sites. Air temperature was the best explanatory variable to explain trends in soil warming by an average 0.29 ± 0.21 °C per decade and the trend peaked during the period from 1991–2000. Especially, the summer months (June to August) contributed most to the soil warming effect, whereby the increase in maximum ST (STmax) was nearby fivefold with 4.89 °C compared with an increase of minimum ST (STmin) of 1.02 °C. This widening between STmax and STmin fostered enhanced diurnal ST fluctuations at ten out of eleven stations. Subsoil warming up to + 2.3 °C in 100-cm depth is critical in many ways for ecosystem behavior, e.g., by enhanced mineral weathering or organic carbon decomposition rates. Thus, spatiotemporal patterns of soil warming need to be evaluated by trend decomposition procedures under a changing climate.Graphical abstract

Can hemp hurd or paper mulch and biochar application improve weed management in matted-row strawberry production systems?

AbstractDuring 2015 and 2016, studies were conducted at Absaraka and Dickinson, North Dakota to evaluate the impacts of hemp (applied at 1156 m3 ha−1) and commercial paper mulch, as well as soil-applied biochar (applied at 11.25 m3 ha−1), on weed suppression and strawberry growth during the establishment year, and on weed suppression and strawberry yield during the production year, in a matted row production (MRP) system. During 2015, biochar influenced dry weed biomass only within the hemp mulch, with slightly more weed biomass associated with biochar application compared to zero biochar (3.1 vs 0.4 g m−2), suggesting that biochar may have increased weed germination and/or emergence from beneath hemp mulch. Biochar application also slightly increased soil pH, from 6.9 in non-amended soil to 7.0 in amended soil. Strawberry runner number during 2015 was greater in association with hemp or paper mulch compared to zero mulch (4.5 and 4.9 vs 2.4 runners plant −1, respectively). This result mirrored a similar differential in per berry mass across sites (7.6 and 7.4 vs 6.2 g berry −1 for hemp mulch, paper mulch and zero mulch, respectively). These results may be related to hemp and paper mulch reducing maximum soil temperatures during summer 2015. During the establishment year, both hemp and paper mulch suppressed weeds well compared to zero mulch, although at Absaraka hemp mulch provided slightly better weed suppression than paper mulch. During the production year, both mulches continued to suppress weeds compared to zero mulch at Dickinson. However, at Absaraka, only hemp mulch provided weed suppression compared to zero mulch, possibly because of faster paper degradation caused by greater numbers of large precipitation events and greater relative humidity at Absaraka compared to Dickinson. Weeds were removed from plots during 2015 to allow separation of weed suppression from other possible mulch impacts; therefore, yield data do not reveal striking differences among mulch treatments. Because previous research has demonstrated the impact of weed management during the establishment of strawberries in a matted row system, we concluded that hemp mulch may provide more durable weed suppression compared to paper mulch, which would increase strawberry yield protection in an MRP system. Material cost may be an issue for implementing hemp mulch, as hemp hurd cost was 25 times paper mulch at the application rates used in this study. However, hemp mulch could still be a beneficial option, especially for organic strawberry growers desiring a renewable and environmentally sound replacement for plastic mulch who are able to find affordable local sources of this material.

The effects of soil temperature from soil mulching and harvest age on phenol, flavonoid and antioxidant contents of Java tea (Orthosiphon aristatus B.)

BackgroundThe environmental conditions resulted by the agronomic management practices may govern the secondary metabolite contents of medicinal plants, including Java tea (Orthosiphon aristatus B). Abiotic factors such as temperatures have been known to determine the secondary metabolite contents of Java tea. This study aimed at evaluating the effects of soil temperature resulting from soil mulching and harvest age on total phenol, flavonoid and antioxidant contents of Java tea.MethodsThe research was arranged using nested (hierarchy design) with completely randomized design under a screen house at Karanganyar, Indonesia, from July to December 2019. The main factor was soil mulching (control; black plastic mulch, transparent plastic mulch, biodegradable mulch and rice straw mulch) with three replicates. The main factor was nested in the temporal hierarchy factor, namely harvest age which consisted of two levels, i.e., 80 and 100 days. The observation parameters were soil temperature of 10 min (maximum; mean; minimum and soil temperature-based Growing Degree Days, GDD) with sensors and logger; plant growth (plant height, number of leaves, fresh and dry weight); and secondary metabolites including phenol, flavonoids and antioxidant.ResultsThe results confirmed the order of the highest to the lowest mean soil temperature was resulted under the transparent plastic mulch > straw > black plastic mulch > control > biodegradable plastic mulch (26.69 > 26.29 > 26.10 > 26.07 > 25.68 °C, respectively). Overall, the harvest age 100 days resulted in higher plant growth, indicated by the higher fresh and dry weight of biomass, higher phenol and antioxidant contents than 80 days. Soil mulching, especially with plastic and biodegradable plastic mulches with long harvest age (100 days) effected into lower fresh and dry weight of plants. On the other hand, soil mulching indirectly resulted in lower phenol but higher flavonoid contents through higher soil temperature, while antioxidant contents were higher under the big soil temperature-based Growing Degree Day (GDD). The total phenol, flavonoids and antioxidant produced ranging from 193.75 to 412.50 mg GAE/ 100 g DW; 81.13 to 141.47 mg QE/ 100 g DW; and 1875.5–2144.4 µmol TE/g DW.ConclusionHigher maximum soil temperature resulted in lower phenol content, while higher minimum soil temperature and shorter harvest age increased total flavonoid. Longer harvest age produced more total phenol and antioxidant due to bigger soil temperature-based Growing Degree Day (GDD).Graphical

Influence of different organic mulches on soil hydrothermal and plant growth parameters in potato crop (Solanum tuberosum L.)

Present study was conducted to investigate the effect of different mulching materials on soil hydrothermal environment and plant growth parameters for potato crop at field experimental station of National Institute of Technology, Hamirpur in the humid sub-tropical agro climate of Western Himalayas. The field experiments were conducted in a randomized complete block design with four mulching treatments; wheat straw mulch, pine needle mulch, rice straw mulch and no mulch in three replications. An increase in soil moisture retention ranging from 5.14% to 42% was observed depending upon the mulch material and depth of the soil layer in root zone. Mulching also reduced the daily maximum soil temperature up to 3.5ºC with an average temperature reduction of 1-2ºC during the period of tuber formation. Mulching produced beneficial effects on root depth, plant height, leaf area index and tuber yield. Mulching helped to bring about a yield surplus of 1.7-4.4 tonnes ha-1 over unmulched conditions and an increase in water use efficiency which varied from 13.5% in rice straw mulch to 34.9 % inwheat straw mulch.

​Effect of Planting Methods, Plastic Mulches, Training Systems, Soil Temperature and Soil Moisture on Tomato Yield

Background: Tomato is an important vegetable crop of Himachal Pradesh grown during summer and rainy seasons. Although the produce of the tomato fetches lucrative rates in the plains of Northern India, yet, the production is threatened by plethora of factors viz., diseases, insect-pests and weeds which ultimately affects yield and quality of fruits. The planting methods, mulches and training systems played enormous role in maintaining the soil temperature and moisture. Methods: The present investigation was carried out to study the performance of tomato (var. Solan Lalima) crop under open field conditions with two different planting methods, three types of mulch treatments and two types of training systems. This experiment was conducted at Vegetable Research Farm of DR YSP, UHF, Nauni, Solan during the period from March to September, 2017-18 and similarly for the period from March to September, 2018-19. Result: The maximum soil temperature was recorded under blackmulch followed by silver/black polythene mulch and control during the standard meteorological week (March to September, 2017-18 and 2019). Soil moisture was found to be maximum those treatments where silver or black mulch was used as compared to black mulch plot under the open field conditions. The maximum fruit yield (140.71 kg/plot) was obtained under the raised bed planting system, black mulch and two stem training system and the corresponding value being 136.16 kg/plot for raised bed planting method, silver/black mulch and two stem training system.

Environmental controls and influences of Pinus roxburghii Sarg. (Chir pine) plantation on temporal variation in soil carbon dioxide emission and soil organic carbon stock under humid subtropical region.

Soil carbon dioxide emission is a major component of ecosystem respiration, responsible for organic carbon losses from the ecosystem. In Pinus roxburghii Sarg. plantations, higher CO2 emission coincided with maximum soil moisture and soil temperature during the rainy season (4.23µmol CO2m-2s-1) followed by summer season (1.69µmol CO2m-2s-1) and winter season (1.35µmol CO2m-2s-1). The soil CO2 emission rates recorded during the rainy season differed significantly from other seasons (p < 0.05). Multiple linear regression revealed that rainfall was the main dominant factor affecting the soil CO2 emission. A significant positive correlation with minimum air temperature and average air temperature during the lag period, i.e., preceding 15days of data, was recorded. A significant positive correlation was also observed between annual soil CO2 emission rates with soil temperature, soil moisture, air temperature, and rainfall (p < 0.05). Vapor pressure and relative humidity at 14.19h also emerged as additional scientific variables affecting soil CO2 emission with significant positive correlations. Annual soil CO2 emission rates and soil properties were not significantly correlated but were positively correlated with organic carbon, exchangeable potassium and negatively correlated with available nitrogen and phosphorous (p > 0.05). Higher annual average carbon stock, 95.05 t ha-1 in P. roxburghii plantations than the yearly soil CO2 emission, 33.23 t ha-1 indicates that plantations sequester more carbon than the emissions.

Effects of mulching on soil temperature and yield of winter wheat in the semiarid rainfed area

• Mulching significantly increased winter wheat productivity. • The cooling effect may be beneficial to vegetative growth and yield formation. • Mulching reduced the daily variable amplitude of soil temperature. • Mulching showed the warm effect in the season with lower air temperature. Mulching is a major production mode with highly effective use of water in the hydrothermal deficient area of northwest China. However, given the differences in environments and crop species among regions, it is important to further understand whether the mulching-induced changes in soil temperature are beneficial to crop production. Here, we used winter wheat to study the effect of mulching on soil temperature, soil water content, dry matter and yield. Two 3-year field experiments were conducted at two sites over 6 consecutive years (2012–2015 at site 1, and 2015–2018 at site 2) in the semiarid rainfed thermal deficient areas of northwest China. In each experiment, three mulching treatments, including straw strip mulching (SSM), plastic film mulching (PFM) and non-mulching (CK), were tested in a replicated randomized block design. Compared with CK, SSM and PFM significantly increased grain yield by 18.6–69.1 % and 35.5–61.3 % in 2012–2017 growing seasons, except that there was no significant difference in the wet year (2017–2018). In the SSM treatment, soil temperature generally decreased at different growth stages, resulting in a slight decline of 0.9–1.9 ℃ in the 0–25 cm soil layer, whereas in the PFM treatment, soil temperature increased before the jointing stage and decreased subsequently. SSM reduced the daily variable amplitude of soil temperature by decreasing the maximum soil temperature, whereas PFM produced the same effect by decreasing the maximum soil temperature and increasing the minimum soil temperature, which could promote the winter wheat vegetative growth and yield formation in the six experimental years. SSM and PFM decreased accumulated soil temperature from the overwintering stage to maturity stage by 60.1–234.6 ℃ and 30.5–148.5 ℃, respectively. The beneficial effect of the change in soil temperature in SSM and PFM plots expanded the storage capacity of winter wheat. Overall, the moderately cooling effect of mulching was conductive to promoting vegetative growth and expanding storage capacity, ultimately improving crop yield. Our results suggest that SSM can be adopted for sustainable winter wheat production in semiarid rainfed areas under thermal deficient conditions.

Rice Blast (Magnaporthe oryzae) Occurrence Prediction and the Key Factor Sensitivity Analysis by Machine Learning

This study aimed to establish a machine learning (ML)-based rice blast predicting model to decrease the appreciable losses based on short-term environment data. The average, highest and lowest air temperature, average relative humidity, soil temperature and solar energy were selected for model development. The developed multilayer perceptron (MLP), support vector machine (SVM), Elman recurrent neural network (Elman RNN) and probabilistic neural network (PNN) were evaluated by F-measures. Finally, a sensitivity analysis (SA) was conducted for the factor importance assessment. The study result shows that the PNN performed best with the F-measure (β = 2) of 96.8%. The SA was conducted in the PNN model resulting in the main effect period is 10 days before the rice blast happened. The key factors found are minimum air temperature, followed by solar energy and equaled sensitivity of average relative humidity, maximum air temperature and soil temperature. The temperature phase lag in air and soil may cause a lower dew point and suitable for rice blast pathogens growth. Through this study’s results, rice blast warnings can be issued 10 days in advance, increasing the response time for farmers preparing related preventive measures, further reducing the losses caused by rice blast.

Reduced sclerotial viability of Stromatinia cepivora and control of white rot disease of onion and garlic by means of soil bio-solarization

The suppressive effects of soil bio-solarization, which is a new method of soil disinfestation that combines soil bio-fumigation with soil solarization, against the sclerotial viability of Stromatinia cepivora and the subsequent control of white rot disease of onion and garlic were evaluated. Soil was bio-fumigated with fresh amendments of cow manure, chicken manure, horse manure, cruciferous plant residues, or Allium waste, at 30,000 kg/ha. After bio-fumigation, the soil was irrigated and covered with a 200 μm transparent plastic sheet for 60 days. Plots that received fresh amendment and remained uncovered and untreated served as controls. Solarization alone increased the maximum soil temperature to 55.3 °C, 50.3 °C and 46.3 °C at 10, 20, and 30 cm depths, respectively, which led to significant reductions (98.0%, 89.3%, and 62.7%, respectively) in the sclerotial viability of S. cepivora. Soil bio-solarization with cruciferous plant residues or Allium waste resulted in the strongest negative effects on the sclerotial viability of S. cepivora, with reductions of 100.0%, 98.7%, and 87.3% or 100.0%, 99.3%, and 87.7%, at 10, 20, and 30 cm depths, respectively. Compared to the non-treated control, these treatments significantly reduced the incidence of white rot disease in onion and garlic, which led to increases in onion and garlic yield in fields that were heavily infested by S. cepivora.

Genotype-by-year interaction for grain yield of Iranian wheat cultivars and its interpretation using Vrn and Ppd functional markers and environmental covariables

In the present study, fifty genotypes were evaluated over 5 years. The analysis of variance revealed significant interaction (P < 0.001) between genotype and year (GYI). The results of different stability statistics illustrate that the Kang’s rank-sum is a good statistic and based on that, Azadi, Roshan, Mahdavi, Marvdasht, and Naz identified as desirable cultivars. Seven environmental factors including maximum temperature, minimum temperature, average temperature, precipitation, relative humidity, daylight hours, and soil temperature over eleven twenty-day periods and sixteen molecular markers associated with vernalization and photoperiod were used as covariates to interpret the interaction. The Partial least square regression biplot with environmental covariates explained 28.23% and with genotypic covariates explained 40.24% of the GYI. The results also showed that genotypes do not respond similarly to environmental variables at different stages of development. Genotypes have been classified into three groups, the first group being more related to environmental factors at the end of the growing season, the second group being more influenced by environmental factors at the beginning of the season, and the third group being genotypes of environmental factors throughout the season, especially the mid-season was affected. Among environmental factors, relative humidity except for period 9 had a special role in GYI in all periods. On the other hand, Ppd.D1D001.KASP, Vrn.B1.B.KASP, Inter1.D.deletion, VRN.A1, Vrn.A1.E7.FT.KASP and Vrn.A1.E4.vern.KASP markers had the most impact on the GYI among the different molecular markers. This information on the causes of the GEI can be useful in future breeding and management programs.

Incorporating rock in surface covers improves the establishment of native pioneer vegetation on alkaline mine tailings

Background and aimsRates of tailings production and deposition around the world have increased markedly in recent decades, and have grown asynchronously with safe and environmentally suitable solutions for their storage. Tailings are often produced in regions harbouring biodiverse native plant communities adapted to old, highly-weathered soils. The highly-altered edaphic conditions of tailings compared with natural soils in these areas will likely select against many locally endemic plant species, making phytostabilisation, rehabilitation or ecological restoration of these landforms challenging. MethodsWe established four substrate cover composition treatments on a dry-stacked magnetite tailings storage facility in semi-arid Western Australia, representative of standard industry practices for rehabilitating or restoring post-mining landforms in the region. Plots were seeded with a selection of locally native plant species and monitored for five years to determine whether different substrate cover treatments yielded different edaphic conditions (soil moisture, substrate surface temperature and substrate chemistry) and influenced soil development and the success of native vegetation establishment. ResultsNo vegetation established from seeds on unamended tailings with no surface cover, and substrate chemistry changed minimally over five years. In contrast, rock-containing surface covers allowed establishment of up to 11 native plant species from broadcast seeds at densities of ca. 1.5 seedlings m−2, and up to 3.5 seedlings m−2 of five native pioneer chenopods from capture of wind-dispersed seeds from surrounding undisturbed native vegetation. Greater vegetation establishment in rock-containing surface covers resulted from increased heterogeneity (e.g., lower maximum soil temperature, greater water capture and retention, surface microtopography facilitating seed capture and retention, more niches for seed germination). Soil development and bio-weathering occurred most rapidly under the canopy of native pioneer plants on rock-containing surface covers, particularly increases in organic carbon, total nitrogen, and organo-bound aluminium and iron. ConclusionsSeed germination and seedling survival on tailings were limited by extreme thermal and hydrological conditions and a highly-altered biogeochemical environment. The design of surface cover layers appears crucial to achieving closure outcomes on tailings landforms, and designs should prioritise increasing surface heterogeneity through the incorporation of rock or other structure-improving amendments to assist the establishment of pioneer vegetation.