Soil Surface Temperature Research Articles

An optimized two source energy balance model based on complementary concept and canopy conductance

In this study, we revised a two source energy balance model (Gc-TSEB) that is based on canopy conductance and soil moisture in evapotranspiration (ET) estimation. We estimate soil evaporation (E) using the complementary concept and soil surface temperature, therefore, the revised Gc-TSEB requires no soil moisture as input. We tested Gc-TSEB at 10 flux sites under various land cover and climate conditions. The flux-calibrated Gc-TSEB performed well in ET predictions, with determinant coefficients (R2) larger than 0.9 at most of the sites. The modeled transpiration was highly correlated with the Gross Primary Production, indicating the usefulness of the model in ET partitioning. More importantly, Gc-TSEB can be calibrated against the land surface temperature (LST), which is operationally available using remote sensing technique. Overall, daily ET that was predicted by the LST-calibrated Gc-TSEB generally matched the trends of the ET measurements at most of the sites, and R2 range from 0.63 to 0.93, with a median of 0.80, at all sites. Transpiration estimation was highly consistent with the simulations from the flux-calibrated model. Moreover, in vegetated surfaces, soil evaporation was estimated reasonably well using the LST-calibrated Gc-TSEB. However, positive biases are prevalent when vegetated fraction is smaller than 0.2, especially in cold regions because of the dramatic differences in evaporation process between summer and winter. To improve model performances, calibrating Gc-TSEB model in separated periods and using prior knowledge as constraints proved to be useful.

Global observed and modelled impacts of irrigation on surface temperature

Agricultural irrigation has significant potential for altering local climate by reducing soil albedo, increasing evapotranspiration, and enabling greater leaf area. Numerous studies using regional or global climate models have demonstrated the cooling effects of irrigation on mean and extreme temperature, especially over regions where irrigation is extensive. However, these model‐based results have not been well validated due to the limitations of observational data sets. In this study, multiple satellite‐based products, including the Moderate Resolution Imaging Spectroradiometer (MODIS) and Soil Moisture Active Passive (SMAP) data sets, are used to isolate and quantify the local impacts of irrigation on surface climate over irrigated regions, which are derived from the Global Map of Irrigation Areas (GMIA). The relationships among soil moisture, albedo, evapotranspiration, and surface temperature are explored. Strong evaporative cooling by irrigation lowers daytime surface temperature over arid and semi‐arid regions, such as California's Central Valley, the Great Plains, central Asia, and northwestern India. However, the cooling effects are less evident in areas of eastern China and the Lower Mississippi River Basin despite extensive irrigation over these regions. Results are also compared with irrigation experiments using the Community Earth System Model (CESM) to assess the model's ability to represent land–atmosphere interactions in regards to irrigation. CESM greatly underestimates the surface temperature response to irrigation. The comparison between the offline and coupled simulations suggests that the irrigation‐induced cooling can be regulated by the interactions between land surface and atmosphere, and amplified signals are found over the “hot spot” regions. Meanwhile, model resolution can also influence the magnitude of the local cooling by irrigation.

The Urban Heat Island in an Urban Context: A Case Study of Mashhad, Iran.

In this study, the spatio-temporal changes of urban heat island (UHI) in a mega city located in a semi-arid region and the relationships with normalized difference vegetation index (NDVI) and normalized difference built-up index (NDBI) are appraised using Landsat TM/OLI images with the help of ENVI and ArcGIS software. The results reveal that the relationships between NDBI, NDVI and land surface temperature (LST) varied by year in the study area and they are not suitable indices to study the land surface temperature in arid and semi-arid regions. The study also highlights the importance of weather conditions when appraising the relationship of these indices with land surface temperature. Overall, it can be concluded that LST in arid and steppe regions is most influenced by barren soil. As a result, built-up areas surrounded by soil or bituminous asphalt experience higher land surface temperatures compared to densely built-up areas. Therefore, apart from setting-up more green areas, an effective way to reduce the intensity of UHI in these regions is to develop the use of cool and smart pavements. The experiences from this paper may be of use to cities, many of which are struggling to adapt to a changing climate.

Dynamical effects of plastic mulch on evapotranspiration partitioning in a mulched agriculture ecosystem: Measurement with numerical modeling

Mulching is a common and effective practice to artificially reduce evaporation for the purposes of water conservation in arid/semiarid ecosystems. Few studies have quantified the effects of plastic mulch on evapotranspiration (ET) partitioning impacted by different biophysical processes between bare and mulch-covered soil within a soil-mulch–plant-atmosphere continuum. Here, we partitioned ET flux into bare soil evaporation (Ebs), mulch-covered soil evaporation (Ems) and transpiration (T) in an oasis cropland ecosystem that was partially covered by plastic film, using an improved multisource energy balance model. The modeled water/energy fluxes agreed well with those measured by the eddy covariance. The modeled surface temperatures of both bare soil and mulch-covered soil were also consistent with measured fluxes, with a high R2 (0.81). During the growing season, the mean fractional contribution to total ET was 21 ± 12%, 6 ± 4%, and 73 ± 14% for Ebs, Ems and T, respectively. Comparisons of modeled output with and without considering mulching effects indicate that mulching increases the T/ET by decreasing E (0.02 ± 0.02 mm h−1), with a mean value of 7.2% and a range of 0–16% during the growing season. Mulching also increases soil temperature, while decreasing available energy at the land surface. These results show that the effects of mulching on ET partitioning varied with leaf development and were more sensitive during periods characterized by a lower leaf area index (e.g., the initial growing period and the period after clear cutting). Without considering mulch effects, the ET (E/ET) flux would be an overestimate, mainly because soil resistance and the availability of soil water would be underestimated. This study highlights the potential of plastic film mulch as a viable management option for soil water conservation and improving soil temperature, which is crucial for plant growth in arid and semiarid ecosystems.

Water percolation in a thick unsaturated loess layer considering the ground‐atmosphere interaction

AbstractThe key objective of this paper is to advance our present understanding of how surface water infiltrates in thick unsaturated loess, which is found in arid and semiarid regions of the world, considering the ground‐atmosphere interaction. In situ data for a period of 1 year in thick loess layer at a site in the Loess Plateau of China that has groundwater table at 97.5 m depth were collected for achieving this objective. Climate factors, mainly rainfall and actual evaporation, were measured. In addition, variations of soil temperature and water content at different depths in the unsaturated zone were also measured. The data were used to interpret the water percolation characteristics by dividing the thick unsaturated zone into three zones; namely, (i) surface zone, which constitutes the top 1.0 m, (ii) unsteady zone, which is from 1.0 to 7.0 m, and (iii) steady zone, which is below 7.0 m. In the surface zone, soil temperature and water content are sensitive to climate factors. There is a variation of water content associated with the cumulative influence of infiltration and evaporation in the precipitation and nonprecipitation periods, respectively. In the unsteady zone, the water content is relatively constant; however, temperature varies in different seasons. Water percolation in this zone is both in liquid and vapour phases. In the steady zone, both soil temperature and water content are constant during the entire investigation period. The percolation velocity in this zone is approximately 1.23 × 10−8 m/s or 0.39 m/year, which suggests that it will take approximately 230.8 years for surface water to pass through the thick unsaturated zone and recharge the groundwater.

Modeling water and heat transfer in soil-plant-atmosphere continuum applied to maize growth under plastic film mulching

Based on our previous work modeling crop growth (CropSPAC) and water and heat transfer in the soil-plant-atmosphere continuum (SPAC), the model was improved by considering the effect of plastic film mulching applied to field-grown maize in North-west China. In CropSPAC, a single layer canopy model and a multi-layer soil model were adopted to simulate the energy partition between the canopy and water and heat transfer in the soil, respectively. The maize growth module included photosynthesis, growth stage calculation, biomass accumulation, and participation. The CropSPAC model coupled the maize growth module and SPAC water and heat transfer module through leaf area index (LAI), plant height and soil moisture condition in the root zone. The LAI and plant height were calculated from the maize growth module and used as input for the SPAC water and heat transfer module, and the SPAC module output for soil water stress conditions used as an input for maize growth module. We used <i>r</i>_<i>s</i>, the representation of evaporation resistance, instead of the commonly used evaporation resistance <i>r</i>_<i>s</i>0 to reflect the change of latent heat flux of soil evaporation under film mulching as well as the induced change in energy partition. The model was tested in a maize field at Yingke irrigation area in North-west China. Results showed reasonable agreement between the simulations and measurements of LAI, above-ground biomass and soil water content. Compared with the original model, the modified model was more reliable for maize growth simulation under film mulching and showed better accuracy for the LAI (with the coefficient of determination <i>R</i>² = 0.92, the root mean square of error RMSE= 1.23, and the Nush-Suttclife efficiency E_ns = 0.87), the above-ground biomass (with <i>R</i>² = 0.96, RMSE= 7.17 t·ha⁻¹ and E_ns = 0.95) and the soil water content in 0–1 m soil layer (with <i>R</i>² = 0.78, RMSE= 49.44 mm and E_ns = 0.26). Scenarios were considered to simulate the influence of future climate change and film mulching on crop growth, soil water and heat conditions, and crop yield. The simulations indicated that the change of LAI, leaf biomass and yield are negatively correlated with temperature change, but the growing degree-days, evaporation, soil water content and soil temperature are positively correlated with temperature change. With an increase in the ratio of film mulching area, the evaporation will decrease, while the impact of film mulching on crop transpiration is not significant. In general, film mulching is effective in saving water, preserving soil moisture, increasing soil surface temperature, shortening the potential growth period, and increasing the potential yield of maize.

Assessment of climatic trend of air temperature at the earth surface in the context of stable development (case of Gyumri city)

Formulation of the problem. The study and assessment of air temperature fluctuations, especially in conditions of expected climate change, is of particular relevance and haste. At the same time, the assessment of temporary changes in air temperature is important as a guarantee of stable development and a long-term economic development. The purpose of the article. The purpose of this work is to find out, analyze and evaluate the patterns of the dynamic changes in air temperature in Gyumri city. To solve this problem, the results of actual observations of the air temperature of the Gyumri weather station, stored at the Ministry of Emergency Situations of the Republic of Armenia «Service for Hydrometeorology and active influence on atmospheric phenomena» have been collected, refined and analyzed. Methods. In the course of research we analyzed and clarified appropriate literary sources, using mathematical-statistical, extrapolation, complex, analyze and correlation methods. Results. A multifactorial correlation relationship was obtained between the average annual air temperature and its absolute maximum and minimum values of Gyumri city. A close correlation was also obtained between the average annual air temperature and its absolute maximum and minimum values of Gyumri city, between the average annual and extreme values of the surface air temperature and the absolute maximum and minimum values of the soil surface of Gyumri city. This makes it possible to calculate the value of any temperature characteristic, while having the other one. Note that in winter the average air temperature values do not differ much from the average soil surface temperature values. This difference grows and reaches its maximum in summer (July – August). As a result of the research, it turned out that according to the actual data on the air temperature in Gyumri city, there was a tendency for the average annual values and absolute maximum of the air temperature to rise, while the absolute minimum values showed a downward trend (in the absolute sense). That is, in the study area in the warm season, an increase in aridity is expected on climate drainage, and in the cold season – a softening. In the work we tried to define the monthly average values of air temperature in Gyumri in 2030, 2070, 2100, using the extrapolation method. The result shows that if the changing process continues, the annual average values of air temperature will increase with comparison to current normal: in 2030 – 0.09 ºC (1.37 %), in 2050 – 0.27 ºC (4.12 %), in 2070 – 0.48 ºC (7.32 %), in 2100 – 0.85 ºC (13 %). This pattern is also characteristic of other regions of the republic. Therefore, it is necessary to implement integrated measures to adapt to the effects of air temperature changes and take this into account when working out programs for social, environmental and economic development.

Simulation of Soil Freezing and Thawing for Different Groundwater Table Depths

Core Ideas The SHAW model was used to simulate the freeze–thaw process during freeze–thaw periods. It revealed the effects of soil texture and groundwater table depth on soil freezing and thawing. The frost depth and accumulated negative soil surface temperature relationship was determined. During freeze–thaw periods, the transformation between phreatic water and soil water will change the soil hydrothermal properties and affect the soil freezing and thawing in shallow groundwater areas. The purpose of this study was to determine the effect of four different groundwater table depths (GTDs) and two soil textures on the process of soil freezing and thawing during two successive freeze–thaw periods using the Simultaneous Heat and Water (SHAW) model. The results show that the frost depth was the maximum when the GTD was 1.0 m, and the maximum frost depths of sandy loam and fine sand were 97.6 and 98.9 cm, respectively. When the GTD was larger than 1.5 m, the maximum frost depth decreased with an increase in GTD, and the maximum frost depth of the soil profile was more sensitive to changes in the air temperature. The frost depth of the soil profile was linear with the square root of the accumulated negative soil surface temperature (ANST) under different GTDs. The ANST was influenced by the phreatic evaporation, and the soil freezing rate increased with an increase in GTD under the same ANST. This research is significant for the rational development of soil water and heat resources and the study of soil water–heat transfer in shallow groundwater areas.

Evaluation of performance of drought prediction in Indonesia based on TRMM and MERRA-2 using machine learning methods

East Nusa Tenggara Province is one of the most vulnerable regions in Indonesia to drought. Drought prediction is definitely needed as a mitigation action to minimize the risk of drought. However, a sparse dataset has led to difficulties in accurately predicting future droughts in areas without meteorological stations, and hence a dataset with a finer resolution is required. This research investigates the performance of a 3-month Standardized Precipitation Index (SPI) derived from the Tropical Rainfall Measuring Mission (TRMM) and Modern-Era Retrospective analysis for Research and Applications (MERRA-2) to predict drought. CART and Random Forest are applied as the classification methods. Using several predictors, the analysis finds that CART has lower predictability than Random Forest. The average accuracy of the prediction using Random Forest reaches 100% with an average Area Under Curve (AUC) of about 0.8. The analysis also shows that predictions using the MERRA-2 dataset lead to higher accuracy and AUC than those using the TRMM. Therefore, using the MERRA-2 dataset predicted by Random Forest can be an optimal way to predict drought in East Nusa Tenggara. The methods confirmed that average soil surface temperature (day and night), Multivariate ENSO Index (MEI), Arctic Oscillation Index (AOI) and Normalized Difference Vegetation Index (NDVI) are strong predictors of drought. The performance of CART and Random Forest is improved with the Synthetic Minority Over-Sampling Technique (SMOTE).The techniques described:•translate drought information and predictors of drought into a base classifier that optimizes the AUC;•allow drought to be predicted for many grid points efficiently and with high accuracy; and•are computationally efficient and easy to implement.

Surface soil temperatures of various land cover types within the Chianan Plain, southern Taiwan

Surface soil temperatures of various land cover types within the Chianan Plain, southern Taiwan

Annual ecosystem respiration of maize was primarily driven by crop growth and soil water conditions

In the context of global warming, carbon dioxide emissions have become a global concern. Cropland respiration is an important component of carbon dioxide emissions from terrestrial ecosystem. A large number of studies have investigated cropland respiration, although many controversies remain about its interannual variations and mechanisms.In this study, an eddy covariance instrument was used to observe carbon fluxes in a maize field for four consecutive years (2014–2017) in the arid region of Northwest China. The night-time respiration rates measured by eddy covariance were used to validate the accuracy of the Van’t Hoff, Arrhenius, and Taylor models in estimating the respiration rate of a maize field.All three models performed well, although the Van’t Hoff model had the highest accuracy. The three models were used to simultaneously estimate the respiration rate of the maize field throughout the growth season. The results showed that in the years 2014, 2015, 2016, and 2017, the annual respiration rates were 485, 1063, 711, and 651 g m−2y-1, respectively. Surprisingly, the respiration rate in 2015 was markedly higher than that in the other three years, and the values were 119%, 49%, and 63% higher than the rates in 2014, 2016, and 2017, respectively. To interpret this observation, this article analyzed the relationships between the respiration rate in the maize field ecosystem and the maximum leaf area index, air temperature, soil surface temperature, and soil water content. The results show that at the interannual scale, the ecosystem respiration showed significant linear positive correlations with the maximum leaf area index and soil water content. The highest values for canopy area, net radiation, irrigation rate, and soil water content were observed in 2015; the crop biomass in 2015 was also greater than that in the other three years, which significantly increased the crop respiration and caused 2015 to have the highest respiration rate.The results showed that at the interannual scale, crop growth and soil surface water conditions were the critical determinants of respiration. This study provided a new perspective and a basis for an in-depth understanding of the mechanism of carbon dioxide emission in croplands.

PHYSICAL PROTECTOR IN DIRECT SOWING OF BARU INFLUENCING IN THE INITIAL GROWTH OF THE SEEDLINGS

The objective of this study was to evaluate the influence of using physical protectors on the emergence and initial growth of Baru seedlings in a direct sowing system. The experiment was installed in a randomized complete block design, testing the use of physical protectors (no protection, P0; plastic cup (500 mL) without the bottom, P1; laminated wood, P2), with 12 repetitions. Weekly soil temperature monitoring was carried out in the morning and in the afternoon in the period between 14 and 56 days after sowing (DAS). Daily emergence follow-up was also performed, and the stem diameter, total height and number of leaves were measured at 81 DAS. The use of physical protectors in the direct seeding of Baru interfered in the soil surface temperature on the sowing point, on the seedling emergence speed index, seedling survival, stem diameter and seedling height. Implementing protectors slowed the seedling emergence speed, however it provided higher percentages of emergence, survival and greater growth in diameter and height.

Influence of streambank fencing on vegetation and soil of the Mixed prairie component in a complex corridor pasture

A 5 yr (2011–2015) field study was conducted to test the hypothesis that streambank fencing had a significant effect on selected vegetation and soil properties of the Mixed prairie component of a complex corridor pasture. The grazing treatments [ungrazed (UG) – periodic grazing (PG)] inside the corridor pasture were 11 yr (2001–2012) of cattle exclusion (UG), followed by 3 yr (2013–2015) of periodic grazing (PG) when the riparian soil was dry. A control treatment outside the fencing was continuous grazing (CG). Selected vegetation and soil properties were measured over the growing season at 10 paired locations in each treatment (nonreplicated) pasture over 5 yr (2011–2015), and rangeland health was measured in 2011. The UG–PG treatment significantly (P ≤ 0.10) increased the total biomass by 2- to 5-fold in all 5 yr compared with CG treatment and improved the rangeland health score of the UG phase of the UG–PG (63%) treatment compared with the CG treatment (50%) in 2011. It also significantly reduced surface soil temperature by 2.2–5.2 °C, significantly increased volumetric water content of the surface soil by 7%–10% in 3 of 5 yr, and significantly increased surface soil CO2 efflux (instantaneous) by 17%–60% in all 5 yr. Overall, the UG–PG treatment improved rangeland health, increased total biomass, soil water, and soil CO2 efflux of the Mixed prairie, but decreased soil temperature compared with the CG treatment. Excessive dead biomass, greater fire risk, and an increase in noxious weeds caused by cattle exclusion suggested that periodic grazing may be the preferred option.

Field Measurements and Satellite Remote Sensing of Daily Soil Surface Temperature Variations in the Lower Colorado Desert of California

The purpose of this study was to better understand the relationships between diurnal variations of air temperature measured hourly at the soil surface, compared with the thermal infra-red (TIR) emission properties of soil surfaces located in the Lower Colorado Desert of California, eastern Riverside County. Fifty air temperature loggers were deployed in January of 2017 on wooden stakes that were driven into the sandy or rocky desert soils at both Ford Dry Lake and the southern McCoy Mountains wash. The land surface temperature (LST) derived from Landsat satellite images was compared to measured air temperatures at 1 m and at the soil surface on 14 separate dates, until mid-September, 2017. Results showed that it is feasible to derive estimated temperatures at the soil surface from hourly air temperatures, recorded at 1 m above the surface (ambient). The study further correlated Landsat LST closely with site measurements of air and surface temperatures in these solar energy development zones of southern California, allowing inter-conversion with ground-based measurements for use in ecosystem change and animal population biology studies.

Water storage effect of soil freeze-thaw process and its impacts on soil hydro-thermal regime variations

In the soil freeze/thaw phenomenon, the soil water phase and energy budget change, which can affect the soil-vegetation-atmosphere system. Herein, the basic role of freeze–thaw–process (FTP) in soil water and heat transport and its impact on soil moisture and temperature variation were investigated using the observations and numerical experiments with and without FTP in Community Land Model version 4.5 (CLM4.5) on the Tibetan Plateau (TP). The results averaged over the whole TP revealed that no soil FTP (i.e., no water phase change occurred) resulted in lower surface soil temperature by about -1.02 ℃ in freeze-thaw (FT) period, while surface soil temperature is higher by about 0.91 ℃ and surface soil moisture is drier by about -0.02 mm3/mm3 in after-thaw (AT) period. Soil FTP has a water storage effect, the storage index (SI) can reach 0.95 at surface layer. Without soil FTP, the surface soil water content at the AT period can be reduced by ∼10% (SI is decreased by about -0.05) as a result of enhanced evaporation; the soil moisture memory was shortened by about -20 days in March. Accordingly, surface latent heat decreased by -1.07 W/m2, while the surface sensible heat increased by 4.72 W/m2. The effects of FTP on soil water and heat transport at deep layer are distinguished from that at the surface layer. These imply that the biases of soil temperature and moisture simulation in models during FT period could lead to large uncertainties in estimating climate effects of TP. Under climate warming background in recent decades, with the delaying of soil freeze-beginning date and advancing of soil thaw-end date, changes of soil FTP regime would lead to loss of spring soil moisture.

High biodiversity silvopastoral system as an alternative to improve the thermal environment in the dairy farms.

The aim of this work was to evaluate the influence of high biodiversity silvopastoral system (SPSnuclei) on microclimate and thermal comfort index thru a parallel with treeless pasture (TLP) during the four seasons of the year. Three conditions were determined for this study: shadowing area in SPSnuclei, sunny area in SPSnuclei, and sunny area in TLP. During two consecutive days in each season, the following microclimatic variables were collected: air temperature (°C), relative humidity (%), illuminance (lux), wind speed (m/s), and soil surface temperature (°C). The temperature and humidity index (THI) was calculated for each condition as indicative of thermal comfort. An influence analysis was carried out by generalized linear models to evaluate the system effects on the microclimatic variables. A confirmatory analysis was done with Wilcoxon-Mann-Whitney. Systems (SPSnuclei x TLP) influenced the microclimatic variables and THI (p < 0.05). The lowest means of air temperature, illuminance, wind speed, and soil surface temperature were found in SPSnuclei. As expected, autumn and winter presented a comfortable environment even on treeless pastureland. Only the SPSnuclei showed a comfortable environment for dairy production during spring. During summer, the TLP had a microclimate and thermal comfort index not suitable for dairy production already in the first hours of the day (THI between 79 and 85). We concluded that SPSnuclei provided better environment for pasture-based dairy production when compared to TLP. The high THI measured in TLP during summer could be a limiting factor on animal production.

Delineating Drought Risk Areas Using Remote Sensing and Geographic Information Systems– A Case Study of Western Highlands Province, Papua New Guinea

In the highlands of Papua New Guinea, rain-fed subsistence farming has been the main source of food and small cash earnings for the majority of the rural population. Consequently, as a result of elongated period of drought, reduction in food and water supply bring forth starvation / malnutrition led sickness and death, especially when authorities fail to intervene because inaccessibility and remoteness of the highly dissected terrain, as a result relief and basic services don’t reach the hungry mouth on time. Such conditions were reported recently in many parts of Papua New Guinea especially prevalent in coastal regions and uplands of the highlands region. In this study, GIS and Remote Sensing (RS) technology were employed in highlighting and demarcating potential drought risk zones in Western Highlands Province. Basically, several environmental factors like; soil types, NDVI, rainfall, terrain, population demography and surface temperature were prepared and integrated in GIS environment through multi-criteria evaluation techniques where risk areas were identified. The final output generated from factors integration were then assessed and reclassified to indicate levels of drought risk zones from Low, Medium and High. Hence, several built-up areas where then marked on each risk zones in an attempt to highlight the location, distribution and accessibility in respect to the risk areas identified.

Delineating Drought Risk Areas Using Remote Sensing and Geographic Information Systems– A Case Study of Western Highlands Province, Papua New Guinea

In the highlands of Papua New Guinea, rain-fed subsistence farming has been the main source of food and small cash earnings for the majority of the rural population. Consequently, as a result of elongated period of drought, reduction in food and water supply bring forth starvation / malnutrition led sickness and death, especially when authorities fail to intervene because inaccessibility and remoteness of the highly dissected terrain, as a result relief and basic services don’t reach the hungry mouth on time. Such conditions were reported recently in many parts of Papua New Guinea especially prevalent in coastal regions and uplands of the highlands region. In this study, GIS and Remote Sensing (RS) technology were employed in highlighting and demarcating potential drought risk zones in Western Highlands Province. Basically, several environmental factors like; soil types, NDVI, rainfall, terrain, population demography and surface temperature were prepared and integrated in GIS environment through multi-criteria evaluation techniques where risk areas were identified. The final output generated from factors integration were then assessed and reclassified to indicate levels of drought risk zones from Low, Medium and High. Hence, several built-up areas where then marked on each risk zones in an attempt to highlight the location, distribution and accessibility in respect to the risk areas identified.

Can mulching of maize straw complement deficit irrigation to improve water use efficiency and productivity of winter wheat in North China Plain?

Improving resource-use efficiency is vital for sustainable agricultural production and food security in water-scarce regions such as North China Plain. The aim of this study was to assess the effects of irrigation and straw-mulch on accumulated intercepted photosynthetically active radiation (AIPAR), radiation-use efficiency (RUE) and water-use efficiency (WUE) of wheat. A two-factorial field experiment was carried out at Luancheng Research Station (China) during 2015–16 and 2016–17. The factors included three irrigation levels – full (FI), deficit (DI) and partial root-zone drying (PRD), which besides rainfall received 200, 100 and 100 mm of irrigation, respectively, and two mulching strategies – mulch and no-mulch: ∼8 and 0 Mg ha−1, respectively. The results showed that mulch reduced AIPAR (6–11%) and increased RUE for total aboveground dry biomass (3–9%). Mulch affected intercepted photosynthetically active radiation (IPAR) between the tillering and anthesis stages, largely because of reduced soil surface temperature (0.8–1.5 °C), which led to delayed growth/development and impaired light interception. No significant difference was observed between DI and PRD for grain yield; however, effects on WUE varied during the two seasons. DI led to higher WUE during season I compared to PRD, while PRD resulted in highest WUE during season II. AIPAR was reduced under DI and PRD; however, RUE remained unaffected for irrigation treatments. The complementary effects of mulch were observed only under DI where WUE was increased by 4–6%. The results imply that the PRD irrigation under field conditions is not as effective as it has been anticipated, especially in soils with high clay content. Mulch induced reduction in growth/development tends to nullify its positive effects through water conservation. Taken together, these results reiterate the need to further optimize mulching and PRD irrigation practices before recommending their use under field conditions, especially for small grain cereals.

Simulation of thermal performance of solar greenhouse in north-west of Iran: An experimental validation

Application of solar energy in greenhouse heating during the cold months could be of great importance. In this study, six shapes of greenhouses including: uneven span, even span, single span, vinery, quonset and arch type were compared from solar radiation availability point of view. A dynamic model was developed to predict all the internal greenhouse temperatures including inside air, soil surface and north wall temperatures for the selected greenhouse. In this model the radiation component of the heat transfer was used along with the other heat transfer modes. Experimental validation to obtain required parameters was conducted in single span greenhouse (in east-west orientation). The results showed that, as compared to other shapes, the single span shape greenhouse oriented in east-west orientation received about 8% more solar radiation during all the months in a year. It was also determined that using brick wall at north side of the greenhouse can reduce radiation energy loss in this type of greenhouse. The average value of the cover transmittance was estimated to be 0.76 during the period of the experiment. A good agreement was obtained comparing measured and predicted values.