Irrigation In Region Research Articles

Optimal coupling combinations between dripper discharge and irrigation interval of maize for seed production under plastic film-mulched drip irrigation in an arid region

Optimal coupling combinations between dripper discharge and irrigation interval of maize for seed production under plastic film-mulched drip irrigation in an arid region

Ecological security characteristics of main irrigated agricultural areas on the Loess Plateau based on remote sensing information

Ecological security is an important guarantee for the sustainable development of regional economy and society. We analyzed the change characteristics of fraction vegetation coverage (FVC) and remote sensing ecological index (RSEI) of four irrigated agriculture regions of the Loess Plateau (Yinchuan Plain, Hetao Plain, Fenhe River Valley and Weihe River Plain) based on the remote sensing data from 2000 to 2018. The results showed that the FVC decreased in the study area from 2000 to 2018. The variation trend of FVC differed among the four irrigated agricultural distribution areas. The RSEI of the whole area showed an overall downward trend, the RSEI of Yinchuan Plain (down 0.06) and Weihe River Plain (down 0.07) decreased significantly, and the RSEI of Hetao Plain remained stable. The RSEI of Fenhe River Valley showed an increased trend. The ecological stability of Yinchuan Plain and Fenhe River Valley was relatively low, the ecological environment of Hetao Plain was relatively stable, and the ecological environment of Weihe River Plain continued to degrade. The results were important for regional ecological environment protection and agricultural sustainable development.

Impact of climate change on irrigation water requirement of wheat growth – A case study of the Beijing-Tianjin-Hebei region in China

This study analyzes the irrigation water requirement of wheat in the Beijing-Tianjin-Hebei region under the changes of meteorological factors conditions, using the growth period data, and meteorological data from 197 meteorological stations, from 1960 to 2019. The results show that: (1) The annual average precipitation, average wind speed, and average relative humidity of the growth period in the Beijing-Tianjin-Hebei region show a downward variation trend, while the temperature variation shows an upward trend. Moreover, relative humidity and radiation exhibit a negative spatial correlation. (2) Wheat irrigation water requirement in the Beijing-Tianjin-Hebei region gradually decreases from north to south and east to west. However, the eastern region shows a gradually increasing trend, while the western region shows a decreasing trend. (3) Meteorological factors are negatively correlated with irrigation water requirement, potential evapotranspiration, effective precipitation, and relative humidity, and significantly positively correlated with sunshine hours, average temperature, and wind speed. The overall variation in irrigation water requirement has the highest correlation with potential evapotranspiration. However, the yearly variations in regional irrigation water requirement are dependent on factors such as wind speed, relative humidity, and radiation.

Modelling Salinity and Sodicity Risks of Long-Term Use of Recycled Water for Irrigation of Horticultural Crops

Long-term use of recycled water (RW) for irrigation in arid and semiarid regions usually changes the soil solution composition and soil exchange characteristics, enhancing the risk for salinity and sodicity hazards in soils. This modelling study focuses on developing alternative management options that can reduce the potentially harmful impacts of RW use on the irrigation of wine grapes and almonds. The multicomponent UNSATCHEM add-on module for HYDRUS-1D was used to evaluate the impact of long-term (2018–2050) use of irrigation waters of different compositions: good-quality low-salinity (175 mg/L) water (GW), recycled water with 1200 mg/L salinity (RW), blended water of GW and RW in the 1:1 proportion (B), and monthly (Alt1) and half-yearly (Alt6) alternate use of GW and RW. The management options include different levels of annual gypsum applications (0, 1.7, 4.3, and 8.6 t/ha soil) to the calcareous (Cal) and hard red-brown (HRB) soils occurring in the Northern Adelaide Plain (NAP) region, South Australia. Additional management scenarios involve considering different leaching fractions (LF) (0.2, 0.3, 0.4, and 0.5) to reduce the salinity build-up in the soil. A new routine in UNSATCHEM to simulate annual gypsum applications was developed and tested for its applicability for ameliorating irrigation-induced soil sodicity. The 1970–2017 period with GW irrigation was used as a warmup period for the model. The water quality was switched from 2018 onwards to reflect different irrigation water qualities, gypsum applications, and LF levels. The data showed that the GW, B, Alt1, and Alt6 irrigation scenarios resulted in lower soil solution salinity (ECsw) than the RW irrigation scenario, which led to increased ECsw values (4.1–6.6 dS/m) in the soil. Annual gypsum applications of 1.7, 4.3, and 8.6 t/ha reduced pH, SAR, and ESP in both soils and reduced the adverse impacts of irrigation, especially in surface soils. A combination of water blending or cyclic water use with 3.8 t/ha annual gypsum applications showed promise for the SAR and ESP control. Additionally, irrigation with RW, a 0.2 LF, and annual gypsum applications limited the harmful salinity impacts in the soils. However, in the RW irrigation scenario, ECsw and ESP at the bottom of the crop root zone (90–120 cm depth) in the HRB soil were still higher than the wine grape and almond salinity thresholds. Thus, annual amendment applications, combined with the long-term use of blended water or cyclic use of RW and GW, represent a sustainable management option for crop production at the calcareous and hard red-brown soils.

Response of cotton to irrigation, fertilization and plant density in a semi-arid region of Iran

Response of cotton to irrigation, fertilization and plant density in a semi-arid region of Iran

Impact of organic matter on arsenic mobilization induced by irrigation in the unsaturated and saturated zones

Organic matter (OM) plays an important role in the biogeochemical transformation of arsenic (As) in groundwater and sediments. High-As groundwater used for irrigation introduces dissolved As into the ground. Moreover, water table fluctuations and variations in redox conditions affect As mobilization in both the unsaturated and saturated zones. A field experiment was conducted at the DY site, Datong Basin, China to explore the effect of OM on As and iron (Fe) mobilization and transformation in the unsaturated and saturated zones during irrigation. Soil water/groundwater and sediments sampled at different depths during the experiment were analyzed to investigate the hydrochemical processes and correlations between As, Fe, and OM concentrations. Irrigation activities led to the accumulation of aqueous As in the saturated zone and increasing As content in the topsoil. Analyses of Fourier-transform infrared (FTIR) spectra suggest the existence of As-Fe-OM ternary complexation. Parallel factor analysis (PARAFAC) of the three-dimensional fluorescence excitation–emission matrix (EEM) reveals that water-extractable organic matter (WEOM) of sediments comprises three major components, two terrestrial humic-like components (C1 and C2) and one protein-like component (C3). And terrestrial humic-like components with high molecular weight promotes As-Fe-OM complexation reactions. The results of this study demonstrate As mobilization under irrigation conditions and contribute to a better understanding of the role of OM under high-As groundwater irrigation. This study has implications for controlling and managing OM or As-contaminated water for irrigation in high-As groundwater regions.

A stochastic modeling approach for analyzing water resources systems

Many uncertain factors exist in the water resource systems, leading to dynamic characteristics of the water distribution process. Especially for the watershed including irrigation area with multiple water sources and water users, it is complicated that the joint risk among available water from each water source and multi-uncertainties under water resource allocation among multiple water users. In this research, an approach is developed that a copula-based interval multi-stage fuzzy stochastic programming (CIMFSP) model. This research aims at figuring out the planning of a case study for water-resources management. In the multi-sources water supply subsystem, the copula function is introduced to tackle the interaction of water availability between two water sources (i.e., A &B). Joint risk was set 0.05, 0.10, 0.15 to reflect the shortage risk of total available water at diverse levels. An interval parameter multi-stage fuzzy stochastic programming (IMFSP) model is developed for water resource distribution in a multi-users water-demand subsystem. Through this model, uncertainties presented as interval numbers and probability distributions, as well as fuzzy sets, were handled. The dynamics of the entire water resource system can be reflected by multi-stage discrete trees. A series of solutions can be generated under multiple scenarios (i.e., joint risk and α-cut levels). The modeling results will produce a series of alternatives under a battery of scenarios and help the decision-makers get an insight into the tradeoff between the system economic benefit and financial penalties under the corresponding risk level. This approach is valuable for improving the feasibility of optimal results in the watershed with irrigation region water resource management.

Regional agricultural water resources management with respect to fuzzy return and energy constraint under uncertainty: An integrated optimization approach

In this study, an integrated framework is proposed for agricultural water and land resources management under uncertain circumstances and energy-water nexus. The framework has two components: the optimized interval solutions generation of unknown market quotation and environment situation through the novel interval fuzzy-expectation programming, and the post-optimization decision-making of the tradeoff between system risk and return through risk-explicit interval programming. An optimization model based on the framework was developed from a real description for agricultural water resources system of Guangdong province under considering various crop, multiple water sources, and the related energy consumption in irrigation and drainage. The impact of energy consumption and risk level control on water resources allocation among different crops and system benefits were analyzed. The results indicated that the preference for surface water resources as the main water sources can effectively reduce regional irrigation energy consumption, and the planting area of each crop would have different variations duo to resources endowment constraints. Risk tradeoff-based results can provide valuable information and additional concern for developing low carbon-oriented agricultural water resources management schemes.

Capability of Existing Drought Indices in Reflecting Agricultural Drought in China

AbstractA variety of drought indices have been constructed to monitor agricultural drought using ground‐based observations and satellite data. The drought indices focus on diverse aspects of agricultural drought and may have diverse applicability in different regions. We calculated seven popular drought indices and evaluated their performances on monitoring agricultural drought in the main agricultural regions of China (i.e., Northeast China, the North China Plain, the middle‐and‐lower reaches of the Yangtze River, and the Sichuan Basin). The independent assessment data used here included three aspects: soil moisture, vegetation photosynthesis (i.e., sun‐induced chlorophyll fluorescence, SIF), and crop yield. Results show that drought indices with one‐month time scale are more sensitive to topsoil moisture than drought indices with longer time scales. Drought indices based on regular meteorological data (DImet) and synthesized drought indices (DIsyn) show better performances on capturing drought impacts on the SIF than other drought indices. DIsyn is more appropriate for predicting drought impact on crop yield than other drought indices. In addition, drought impact on vegetation photosynthesis and crop yield is lessened in humid or irrigated regions. Our study sheds light on agricultural drought researches in the future.

Soursop production under supplementary irrigation and mulching in the semiarid region of Brazil

ABSTRACT Irregular rainfall in the semiarid region of Brazil and in the world exerts a limiting action on agricultural production, in general, including fruit species. Under these conditions, irrigation is the input that keeps the production system both economically and socially viable. This study was carried out from 2012 to 2014, in the municipality of Remígio, Paraíba State, Brazil, aiming at evaluating the production of ‘Morada’ soursop cultivated under rainfed and irrigated conditions, in soil with and without mulch, in two harvests. The treatments were distributed in randomized block design with three replicates in a 2 × 3 × 2 factorial scheme, corresponding to non-irrigated plants (0 mm water depth) and plants irrigated weekly (17.2 mm water depth) in soil without mulching, with cover crop residues, and with a sisal bagasse mulch in the 2012/2013 and 2013/2014 crop years. In the soil without mulching, irrigation increased yield from 5.3 to 34.7 t ha-1 in the first harvest and from 9.4 to 57.7 t ha-1 in the second harvest. The association between irrigation and mulch with sisal residue promoted the highest yield. The use of mulch of sisal residue increased the number and mean mass of fruits, production per plant and yield of ‘Morada’ soursop compared to the soil without mulch and covered by crop residues.

Spatial multicriteria approach to support water resources management with multiple sources in semi-arid areas in Brazil

Semi-arid regions often face severe drought events that reduce agricultural and livestock production. In recent years, some international studies have used multicriteria decision analysis (MCDA) approaches combined with geographic information systems (GIS-MCDA) to support decision-makers in assessing the suitability of agricultural land for irrigation in semi-arid regions. Unlike previous studies, which have only considered a single source of water for crop irrigation, this study proposes a GIS-MCDA approach that considers all potentially available local water sources (e.g., groundwater, surface water, and wastewater) as possible alternatives for better multisource water resource management (MWRM) in regions facing water shortages. The geospatial multicriteria evaluation implemented in this study considers a series of technical, environmental, and agricultural productivity criteria using the analytical hierarchy process (AHP) method. Three independent baseline maps were generated, showing the spatial distribution of suitable areas for crop irrigation for each considered water source in the studied area. Surface water, groundwater, and wastewater offered suitable crop irrigation for 83%, 70%, and 26% of the study area, respectively. Overlapping these areas produced a final map showing all the feasible areas for each crop irrigation alternative at the same time. The MWRM approach considering all water sources increased the coverage of suitable areas to be irrigated in the study area by 2.2%, 20.4%, and more than 225% compared to considering surface water, groundwater, and wastewater, respectively, independently. The GIS-MCDA framework proposed in this study provides better support for decision-makers and stakeholders, favouring a reduction in possible conflicts over water scarcity, the diversification of irrigated crops, and an improvement in the quality-quantitative management of water resources in semi-arid regions.

Comparison of Different Interpolation Methods for Prediction of Soil Salinity in Arid Irrigation Region in Northern China

Numerous methods have been used in the spatial prediction of soil salinity. However, the most suitable method is still unknown in arid irrigation regions. In this paper, 78 locations were sampled in salt-affected land caused by irrigation in an arid area in northern China. The geostatistical characteristics of the soil pH, Sodium Adsorption Ratio (SAR), Total Salt Content (TSC), and Soil Organic Matter (SOM) of the surface (0–20 cm) and subsurface (20–40 cm) layers were analyzed. The abilities of the Inverse Distance Weighting (IDW), Ordinary Kriging (OK), and CoKriging (CK) interpolation methods were compared, and the Root Mean Square Error (RMSE) was used to justify the results of the methods. The results showed that the spatial distributions of the soil properties obtained using the different interpolation methods were similar. However, the surface layer exhibits more spatial heterogeneity than the subsurface layer. Based on the RSME, the nugget/sill value and range significantly affected which method was the most suitable. Lower nugget/sill values and lower ranges can be fitted using the IDW method, but higher nugget/sill values and higher ranges can be fitted using the OK method. These results provide a valuable reference for the prediction of soil salinity.

The impact of declining dairy fertility on calving patterns and farm systems: A case study from northern Victoria, Australia

CONTEXTFertility is crucial for pasture-based seasonal calving dairy herds, where cows are expected to calve in a single cohort at a time when peak milk production coincides with maximum pasture availability. However, dairy fertility has declined globally, and many Australian herds now use a split calving system, where non-pregnant cows are given additional opportunities to conceive by having two mating periods per year. Other factors prompting a move to split calving may include financial incentives for producing out-of-season milk, increasing levels of concentrate feeding, and pressure due to extreme seasonal conditions – all of which are particularly apparent in the northern Victorian irrigation region. OBJECTIVEThe aim of our study was to describe the fertility and herd characteristics of the study population and to examine changes in reproductive performance and calving systems that have occurred over the same period. METHODSOur study population included 38 herds from the northern Victorian irrigation region in Australia. We collected individual cow records from each herd from the date on which they started herd recording (with a median start year of 2000 for mating event data) up until December 2016, comprising both fertility-related data such as insemination records, calving dates, and pregnancy test results, and systems-related data such as production, herd size and calving pattern. RESULTS AND CONCLUSIONSFrom a relatively small number of herds, we were able to obtain a dataset comprising 438,578 mating and pregnancy test records for 86,974 cows. From 2003 to 2016, 6-week in-calf rate and first service conception rate declined in the study population for both Holstein-Friesians and Jerseys, while 3-week submission rate remained unchanged. At the same time, the proportion of split calving herds in our cohort markedly increased, with a significant expansion in herd size compared to their seasonal counterparts. The proportion of first parity heifers in herds also increased, which may be a function of increasing herd size, or involuntary culling due to poor fertility. SIGNIFICANCESplit calving represents a significant system change for herd managers, with concomitant effects on labour management, input costs, and the lifestyle they experience. However, if this change has been implemented due to poor fertility without considering whether the increased income outweighs increased input costs, then a suboptimal decision may have been made. Finally, high quality data remains underutilised on individual farms, with significant benefits to the Australian dairy industry if we can overcome the numerous challenges to access it.

Insights into water sustainability from a grey water footprint perspective in an irrigated region of the Yellow River Basin

Water sustainability is imperative for socio-economic development. The grey water footprint (GWF) is a useful indicator for quantifying how human activities influence freshwater systems. This study identified the change in GWF for Yinchuan City, an agricultural region in the Yellow River Basin, by the validation of acquired water-quality data. The driving forces of the GWF were analyzed using the logarithmic mean division index (LMDI) decomposition method. The results indicated that the total GWF showed a declining trend during the study period between 2002 and 2017 within the range of 12.6–21.5 × 108 m3/yr. The agricultural GWF had a relatively stable contribution (30–40%), and the focus should be on the increased proportion of domestic sector in this irrigated region. Economic development and technology effects were the dominant negative and positive factors, respectively, behind the decline in GWF. Although the water pollution levels (0.06–0.12) indicating that the waste assimilation capacity was sufficient to take up the pollutant load, the effect of pollution load on groundwater was cause for concern based on the actual water-quality data. A significant increase in NO3–N in the phreatic water was detected between 2003 and 2013. The dominance of NH4–N for the water supply wells in confined aquifers hinted at the deteriorating water quality, which was attributed to the aquifer leakage under pumping conditions. This study better reflected the current water pollution situation by combining GWF with understanding of the hydrological cycle and the actual water-quality data. Findings in this study will be valuable for addressing water quality threats and to develop sustainability strategies for local authorities.

Effects of deficit irrigation and organic fertilizer on yield, saponin and disease incidence in Panax notoginseng under shaded conditions

Panax notoginseng (Burk) F. H. Chen, called Sanqi, is a valuable herbal plant and is widely used in Chinese medicine. However, the yield and saponin content cannot be guaranteed due to irrational irrigation and fertilizer management in low-latitude regions in southwestern China. To obtain suitable irrigation and organic fertilizer modes for improving the yield and saponin content of the plant, a shelter experiment was conducted using a randomized complete block design with a factorial arrangement of treatments with three replications. Three irrigation regimes, DL, DM and DS (irrigation upper/lower limit: 65–50% θf, 50–35% θf, and 35–20% θf, respectively, where θf is the field capacity), three organic fertilizer levels, FL, FM and FH (33, 48 and 63 t ha−1, respectively), and a control group, CK (65–50% θf and 3 t ha−1), were applied in the two-year and eight-month growth cycles. With the paired comparison design, the results indicated that the flower dry yield, root dry yield and Panax notoginseng saponins (PNS) were significantly affected by different water deficit irrigation and organic fertilizer treatments, and they first increased and then decreased with increased water deficit or organic fertilizer. Compared with DLFH, DMFM reduced water use by 42.39% and fertilizer use by 23.81%, and the flower dry yield, root dry yield, PNS, water use efficiency and partial factor productivity of fertilizer increased by 19.67%, 22.52%, 54.33%, 149.72% and 91.83%, respectively. Under the DMFM treatment, the dry root yield and saponin content for 3-year-old P. notoginseng were 3039.19 kg ha−1 and 10.85%, respectively, which were higher than those resulting from other treatments. Additionally, the PNS resulting from DMFM exhibited the highest comprehensive score and comprehensive index based on principal component analysis and the TOPSIS model. This combination could create a higher yield of flowers and roots, provide a scientific management for planting, and improve the economic benefits for planters and the local government.

Attenuation of salt stress on the physiology and production of bell peppers by treatment with salicylic acid

The use of saline water for irrigation in semi-arid regions has become a reality due to the water scarcity that occurs in most of the year. In this scenario, exogenous application of salicylic acid may be a strategy to mitigate the deleterious effects of salt stress on plants and ensure the production of socioeconomically important crops in the semiarid region of Northeast Brazil, such as bell pepper. Thus, this study examines the osmoprotective effect of salicylic acid on gas exchanges, chloroplast pigments and production components of ‘All Big’ bell pepper plants irrigated with water with different saline levels. The experiment was carried out in greenhouse conditions in Campina Grande - PB, Brazil. Treatments consisted of four levels of electrical conductivity on the irrigation water (0.8, 1.6, 2.4 and 3.2 dS m-1) and four concentrations of salicylic acid (0, 1.2, 2.4 and 3.6 mM), which were distributed in a 4 × 4 factorial arrangement in a randomized block design with three replicates. Increases in irrigation water salinity from 0.8 dS m-1 resulted in changes in gas exchange and total chlorophyll levels of ‘All Big’ bell pepper plants. The estimated salicylic acid concentration of 1.7 mM reduced the effects of salinity on stomatal conductance, transpiration, CO2 assimilation rate, instantaneous carboxylation efficiency, total chlorophyll and fruit diameters. Irrigation with water of 1.8, 0.8 and 1.6 dS m-1 salinity associated with the estimated salicylic acid concentration of 1.6 mM increased the biosynthesis of chlorophylls a and b and the number of fruits, respectively, in bell pepper plants.

Long-term effects of irrigated agriculture on Luvisol pedogenesis in semi-arid region, northeastern Brazil

Long-term irrigation in semi-arid regions leads to shifts in the soil moisture regime, affecting soil attributes and pedogenesis. Drylands are expected to increase worldwide, possibly because of climate change. Few studies have investigated changes in the pedogenic processes due to extensive irrigation in the Brazilian semi-arid region. This study assesses the effects of land use changes (irrigation and cultivation) on the morphological, physical, chemical, and mineralogical properties of soils. We evaluated two soil profiles in the semi-arid region in northeastern Brazil. We investigated an irrigated profile (IP) with long-term irrigation (26 years) and cultivation, and another profile under natural conditions (rain-fed hyperxerophilic Caatinga), that is, a non-irrigated profile (N-IP). The results indicate that land use affected chemical and mineralogical attributes of soils as well as the pedogenetic processes. Both soil profiles showed different behaviors in relation to salts: (1) reduction in soil exchangeable Na content (solodization) in IP, and (2) accumulation of soluble salts (salinization) and increased soil exchangeable Na content (solonization) in N-IP. Land use, possibly irrigation, induced mineralogical alteration pathways, such as the progressive mineral transformations via R0 MLM (mixed-layered minerals), suggesting differences in weathering and mineral evolution. The K-I (kaolinite-illite) and I-V (illite-vermiculite) phases predominated in the clay fraction in both soils and exhibited a greater trend for progressive kaolinization in IP. The other two MLMs (kaolinite-vermiculite, K-V and illite-smectite, I-S) were detected in N-IP and could be a proxy for the lowest weathering degree. This is consistent with the trend for a slight reduction in the SiO2/Al2O3 molecular ratio in IP. Illite was possibly the precursor mineral for other phyllosilicates, such as kaolinite, in IP. Fe-enriched MLM was detected in the decreasing sequence: illite, smectite, and kaolinite layers. The pedogenic trends observed, such as mineral weathering, may be attributed to system response to climate change.

Efficient IoT-Based Control for a Smart Subsurface Irrigation System to Enhance Irrigation Management of Date Palm.

Drought is the most severe problem for agricultural production, and the intensity of this problem is increasing in most cultivated areas around the world. Hence improving water productivity is the primary purpose of sustainable agriculture. This study aimed to use cloud IoT solutions to control a modern subsurface irrigation system for improving irrigation management of date palms in arid regions. To achieve this goal, we designed, constructed, and validated the performance of a fully automated controlled subsurface irrigation system (CSIS) to monitor and control the irrigation water amount remotely. The CSIS is based on an autonomous sensors network to instantly collect the climatic parameters and volumetric soil water content in the study area. Therefore, we employed the ThingSpeak cloud platform to host sensor readings, perform algorithmic analysis, instant visualize the live data, create event-based alerts to the user, and send instructions to the IoT devices. The validation of the CSIS proved that automatically irrigating date palm trees controlled by the sensor-based irrigation scheduling (S-BIS) is more efficient than the time-based irrigation scheduling (T-BIS). The S-BIS provided the date palm with the optimum irrigation water amount at the opportune time directly in the functional root zone. Generally, the S-BIS and T-BIS of CSIS reduced the applied irrigation water amount by 64.1% and 61.2%, respectively, compared with traditional surface irrigation (TSI). The total annual amount of applied irrigation water for CSIS with S-BIS method, CSIS with T-BIS method, and TSI was 21.04, 22.76, and 58.71 m3 palm−1, respectively. The water productivity at the CSIS with S-BIS (1.783 kg m−3) and T-BIS (1.44 kg m−3) methods was significantly higher compared to the TSI (0.531 kg m−3). The CSIS with the S-BIS method kept the volumetric water content in the functional root zone next to the field capacity compared to the T-BIS method. The deigned CSIS with the S-BIS method characterized by the positive impact on the irrigation water management and enhancement on fruit yield of the date palm is quite proper for date palm irrigation in the arid regions.

Nutrient and salinity management for spinach production under sprinkler irrigation in the low desert region of California

Nutrient and salinity management for spinach production under sprinkler irrigation in the low desert region of California

Summer temperature response to extreme soil water conditions in the Mediterranean transitional climate regime

Land surface and atmosphere are interlocked by the hydrological and energy cycles and the effects of soil water-air coupling can modulate near-surface temperatures. In this work, three paired experiments were designed to evaluate impacts of different soil moisture initial and boundary conditions on summer temperatures in the Mediterranean transitional climate regime region. In this area, evapotranspiration is not limited by solar radiation, rather by soil moisture, which therefore controls the boundary layer variability. Extremely dry, extremely wet and averagely humid ground conditions are imposed to two global climate models at the beginning of the warm and dry season. Then, sensitivity experiments, where atmosphere is alternatively interactive with and forced by land surface, are launched. The initial soil state largely affects summer near-surface temperatures: dry soils contribute to warm the lower atmosphere and exacerbate heat extremes, while wet terrains suppress thermal peaks, and both effects last for several months. Land-atmosphere coupling proves to be a fundamental ingredient to modulate the boundary layer state, through the partition between latent and sensible heat fluxes. In the coupled runs, early season heat waves are sustained by interactive dry soils, which respond to hot weather conditions with increased evaporative demand, resulting in longer-lasting extreme temperatures. On the other hand, when wet conditions are prescribed across the season, the occurrence of hot days is suppressed. The land surface prescribed by climatological precipitation forcing causes a temperature drop throughout the months, due to sustained evaporation of surface soil water. Results have implications for seasonal forecasts on both rain-fed and irrigated continental regions in transitional climate zones.