Long-term Irrigation Research Articles

Remediation and mitigation measures to counteract orchard soil degradation by treated wastewater irrigation

Recent studies have shown that long-term irrigation with treated wastewater (TWW11Treated wastewater irrigation (TWW): Freshwater (FW): Blended TWW:FW in a 1:1 ratio (MIX): Low-frequency TWW-irrigation (LFI): TWW irrigated tuff trenches (TUF)) can lead to land degradation and reduction of crop performance in clayey soils due to additions of salts and organic compounds. This study investigated the effects of two remediation and two mitigation methods intended to alleviate the damage to soil properties following long-term irrigation with TWW. The experiment was conducted in a ‘Hass’ avocado orchard (Persea americana Mill.) grown on a clayey soil irrigated with TWW since 2009. The treatments implemented in 2016 included: TWW (control), freshwater (FW), blended TWW:FW in a 1:1 ratio (MIX), low-frequency TWW-irrigation (LFI), and TWW irrigated tuff trenches (TUF). The results showed that FW and MIX significantly reduced total salinity, salinity-related ions (Na and Cl), and sodium adsorption ratio (SAR) to (i) depths of 90 cm and 30 cm under drippers, respectively, and (ii) depths of 60 cm (except for chloride) and 30 cm between drippers, respectively, compared with TWW. TUF and LFI reduced soil salinity and sodicity under drippers but not between drippers compared with TWW. Moreover, FW significantly increased aggregate stability to a depth of 30 cm. TUF had the highest oxygen concentration in the root zone (35 cm depth), followed by FW. Considering the scarcity of freshwater, MIX and TUF are suggested as possible measures for reducing soil salinity and sodicity, and increasing aeration of clayey soils under long-term irrigation with TWW, respectively. Our findings contribute valuable insights into strategies for remediating and mitigating the detrimental effects of TWW irrigation on soil, thus promoting sustainable agriculture in regions facing water scarcity.

Absence of canopy temperature variation despite stomatal adjustment in Pinus sylvestris under multidecadal soil moisture manipulation.

Global warming and droughts push forests closer to their thermal limits, altering tree carbon uptake and growth. To prevent critical overheating, trees can adjust their thermotolerance (Tcrit ), temperature and photosynthetic optima (Topt and Aopt ), and canopy temperature (Tcan ) to stay below damaging thresholds. However, we lack an understanding of how soil droughts affect photosynthetic thermal plasticity and Tcan regulation. In this study, we measured the effect of soil moisture on the seasonal and diurnal dynamics of net photosynthesis (A), stomatal conductance (gs ), and Tcan , as well as the thermal plasticity of photosynthesis (Tcrit , Topt , and Aopt ), over the course of 1 yr using a long-term irrigation experiment in a drought-prone Pinus sylvestris forest in Switzerland. Irrigation resulted in higher needle-level A, gs , Topt , and Aopt compared with naturally drought-exposed trees. No daily or seasonal differences in Tcan were observed between treatments. Trees operated below their thermal thresholds (Tcrit ), independently of soil moisture content. Despite strong Tcan and Tair coupling, we provide evidence that drought reduces trees' temperature optimum due to a substantial reduction of gs during warm and dry periods of the year. These findings provide important insights regarding the effects of soil drought on the thermal tolerance of P. sylvestris.

Accumulation of arsenic and other metals in soil and human consumable foods of Meherpur district, southwestern Bangladesh, and associated health risk assessment

Groundwater and soil contaminated with arsenic (As) are significant environmental health concerns worldwide and have become a serious health issue for millions of Bangladeshis. This contaminated groundwater is commonly used for Boro rice production during the dry season in Bangladesh, leading to long-term As deposition in soils. The consequences of long-term irrigation with As-contaminated groundwater for bioaccumulation in food crops and hence dietary exposure to As and other metals are a threat to the resident. Highly arsenic (292 µg L−1) contaminated groundwater used to irrigate in the study area increases the As content (mean: 24.5 mg kg−1) in irrigated soil than non-irrigated soil (mean: 8.43 mg kg−1). The high enrichment factor (mean: 16.8) and geo-accumulation index (mean: 2.33) revealed that the soil of that particular area is strongly contaminated by As. In paddy, roots showed the maximum As concentration (mean: 139.8 mg kg−1) followed by straws (mean: 5.25 mg kg−1) and grains (mean: 1.23 mg kg−1) where 85–95% As exist in the roots of paddy, and only 0.8–1% As translocate to the harvesting part of the rice in the study area. In food samples, two rice grains (R-1, R-3) and a drumstick (FS-5) exceed the Indian standard of As concentration (As: 1.1 mg kg−1) in food. According to World Health Organization, the metals concentrations in all food samples exceeded the permissible limit except for Cu and Pb in red amaranth; Cr, Cd, and Pb in guava; and Cu and Cd in drumsticks. Higher values of bioaccumulation factor (BAF: 2.94) and the net translocation coefficient (NTC: 6.17) indicate As-accumulation in food from adjacent contaminated soil. Daily metal intake from food consumption suggests that the heavy metal(loid)s like As, Ni, and Pb represent high concentrations and exceed the daily ingestion limits (As: 3 µg kg−1 day−1, Ni: 1.3 µg kg−1 day−1, and Pb: 3.57 µg kg−1 day−1) developed by the Food and Agriculture Organization and European Food Safety Authority. Carcinogenic (> 10–6) and non-carcinogenic (HQ > 1) health risks of As, Pb, Cd, and Cu suggest that the community was at potential health risk according to the United States Environmental Protection Agency.

Simulation of Biophysicochemical Characteristics of the Soils Using Geoelectrical Measurements near the Sewage Station, Assiut City, Egypt

Numerous farmers regularly irrigate their farms with inadequately treated sewage water pumped from the sewage system in the Arab El-Madabegh district of Assiut City, Egypt. According to previous studies, long-term irrigation with partially treated sewage water resulted in significant changes in the physicochemical properties of soil. The principal goals of this study are (1) to infer empirical equations between geoelectrical resistivity measurements and certain biophysicochemical parameters of some soil samples, and (2) to use these empirical equations to calculate the biophysicochemical parameters of the unknown samples for the same location. For this purpose, 27 soil samples at different depth levels (0 to 25, 25 to 60, and 60 to 90 cm) were collected from eleven locations at the sewage station. Physical properties including water content and particle size distribution, chemical properties including soil pH, electrical conductivity (EC), and the heavy metals concentrations, biological properties including total coliform counts, and geoelectrical resistivity measurements were estimated and analyzed for these samples. Electrical resistivity measurements and biophysicochemical properties were cross-correlated using the exponential trend line to fit the cross-correlated data, and the empirical relationships were obtained. These empirical relationships in conjunction with the measured electrical resistivity measurements were used to calculate the biophysicochemical values of the other three random soil samples. The biophysicochemical values of the former three samples were measured by the same normal procedures as 27 samples. Then, the calculated values were correlated with the measured ones. Good correlations between the estimated and the measured values for biophysicochemical features were obtained. Therefore, this method can be employed to calculate the biophysicochemical parameters for any unknown samples that have the same geological conditions for estimating and monitoring soil contamination.

LiDAR DEM and HEC-RAS On-Grid Rainfall Hydrograph Model for Irrigation System

The capacity of the Saddang River Irrigation Canal will be increased by 30% to accommodate long-term irrigation discharge needs. Analysis of the hydraulic model of the irrigation and discharge channels is examined in this study. High resolution LiDAR Digital Elevation and HEC-RAS Model are used to estimate the flow depth and velocities in the event of rain with extreme intensity. HEC-RAS Model solves the 2-D depth-averaged St.Venant equations that are mainly used for river simulation. The HEC-RAS model uses on-grid precipitation hydrograph and flexible meshes that may contain arbitrarily quadrilateral and triangular cells. A hybrid mesh may achieve the best compromise between solution accuracy and computing demand. The HEC-RAS model solved variables include water surface elevation, water depth, depth averaged velocity, Froude number, and bed shear stress. The optimization of the model is useful for improving the drainage modulus, lining channel, drain time period and the performance of the irrigation and drainage channels.

Using Stormwater in a Sponge City as a New Wing of Urban Water Supply—A Case Study

Rapid and even disruptive innovations are needed to make cities fit for the future. The particular challenge will be to transform existing urban spaces in order to increase climate resilience. Along these lines, rainwater harvesting has taken place insufficiently to date, even when Sponge City concepts are implemented. Thus, the concept presented here addresses existing urban neighborhoods and proposes to collect rainwater from nearby rooftops and treat it in decentral treatment units called “City Water Hubs” (CWH) equipped with modular coupled low-energy technologies to produce various customized “City Water” qualities, and store it until it can be used or distributed. A feasibility study with a focus on the campus area at the main building of the Leibniz University of Hannover, the determined rainwater qualities, and the results from investigations with two laboratory test plants provided the basis for the technical design of the pursued concept. The feasibility study showed how sufficient rainwater for irrigation purposes can be made available for the listed large university park even under extreme dry and heat wave conditions. If large portions of the roof area (11,737 m2) of the university’s main building were activated, even in a dry year with only 49.8% of the average precipitation, only 19.8% of the harvested stormwater would be needed for irrigation. The rainwater samples showed TSS concentrations of up to 7.54 mg/L, COD of up to 58.5 mg/L, and NH4 of up to 2.21 mg/L, which was in line with data reported in the literature. The treatment technologies used for the two pilot plants are proven approaches for stormwater treatment and were composed as follows: (1) gravity-driven membrane filtration (GDM) and (2) slow sand filter with integrated activated carbon (AC) layer. The treatment with both (1) and (2) clearly improved the rainwater quality. The GDM reduced turbidity by 90.4% and the Sand/AC filter by 20.4%. With regard to COD, the studies for GDM did not show a clear elimination trend; the Sand/AC filter reduced the COD by 77%. Taken together, decentralized low-energy rainwater treatment can reliably provide quality-assured City Water for any specific use. Regarding the treatment design, GDM is preferable and can be better operated with downstream UV disinfection, which might be needed to reduce the pathogenic load, e.g., for local heat control measures. The research steps presented here will pioneer the development of a city-wide rainwater harvesting infrastructure on the way of establishing stormwater as a resource for a new wing of urban water supply. The presented findings will now result in the implementation of a full-scale CHW on the campus to ensure long-term irrigation of the listed park, relieving the public drinking water supply.

Ecotoxicological monitoring of potentially toxic elements contamination in Eucalyptus forest plantation subjected to long-term irrigation with recycled wastewater

Afforestation is an evergreen technology for restraining greenhouse gases (GHGs) emission and improving soil carbon sink in arid and semi-arid regions. Nonetheless, the long-term impact of woody forests irrigation using recycled wastewater resources remains inconclusive so far. For this purpose, the ecological risk benchmarks of potentially toxic elements (PTEs) were investigated on Eucalyptus forest plantation in order to gauge their bioavailability in the rhizospheric layer of Typic Torripsammentsoil and their accretion capacity in the biosphere. Water quality guidelines pointed to a moderate degree of restriction on use with elevated levels of PTEs. Notably, concentrations of As, B, Cd, Cr, Cu, Mn, Ni, V and Zn were above the permissible limits for irrigation. The geospatial mapping of PTEs concentration in soil pointed to elevated levels of most PTEs, particularly in the deforestated areas. Some of PTEs (Cd, Cu, Hg and Zn) showed values above the permissible limits. A spectrum of ecological risk indices showed considerable to high degree of contamination. Among PTEs, the water–soluble and exchangeable fractions showed high values of As, Cd and Hg (20.7, 17.2 and 11.0%, respectively). Sequential extraction showed variations among PTEs in their tendency to bind with different soil geochemical fractions: (i) carbonate (Cd, Zn and Cu), (ii) Fe–Mn oxides (Pb, Zn and Mn) and (iii) organic matter (B, Pb and Hg). Eight fungal species including Aspergillus flavus, Fusarium solani, Cephalosporimsp., Penicilliumsp., Rhizoctonia solani, Aspergillus niger, Botrytissp. and Verticilliumsp. were dominated in soil. Meanwhile, Agrobacteriumsp., phosphate solubilizing bacteria, nitrogen fixing bacteria and Escherichia coli were the dominant bacterial strains. Values of bioaccumulation index varied among PTEs, wherein B (5.15), Ni (1.98), Mn (1.62) and Cd (1.02) exhibited higher phytoextraction potentials. Other PTEs, however, exhibited values below 1.0 confirming their low phytoextraction potentials. Findings of this investigation, therefore, provide insights into biochemical signals of PTEs contamination in woody forest plantations and the urgent need to contextualize the large-scale utilization of recycled wastewater resources in such vulnerable areas.

Soil Microbial Composition and Soil Health of Reverse-Osmosis-Concentrate and Brackish-Groundwater Irrigated Soils in Southern New Mexico

The phospholipid fatty acid method was used to determine the shifts in microbial biomass due to irrigation with reverse-osmosis (RO) concentrate (or highly saline reject water) and brackish groundwater (BGW). In this greenhouse study, RO concentrate and BGW were applied to irrigate pecan trees for 8 months for two consecutive seasons. The objectives of the study were to (i) evaluate how irrigation with RO concentrate and BGW impacts soil microbial composition in pecan rhizospheres using microbial phospholipid fatty acid (PLFA) biomarkers as indicators, and (ii) evaluate its implications on soil health. Three treatments of RO concentrate (EC = 8.0 dS/m), BGW (EC = 4.0 dS/m), and the city of Las Cruces’s water (EC = 0.8 dS/m) as a control were used to irrigate pecan trees. EC, pH, and organic matter (OM%) content of the soil samples were measured, and PLFA biomarkers for the microbial community were determined. Na-, Cl-, and K-ion concentrations were 26.16, 32.54, and 5.93 meq/L in 2017 and 25.44, 24.26, and 5.49 meq/L in 2018, respectively, in RO irrigation pots. For two seasons, gram-positive bacteria were dominant, while gram-negative bacteria were not detected in the second season. PLFA biomarkers of fungi were found among all three treatments in the first season; however, they appeared only with BGW in the second season. Actinomycetes were recorded in the first season while they were not seen in the second season. Increases in soil salinity and microbial shifts could have important implications for soil health. Irrigating with RO and BGW shifted the soil microbial composition; therefore, long-term irrigation with BGW and RO concentrate would be deleterious for pecan production and soil health.

Effects of long-term irrigation practice on soil quality, organic carbon and total nitrogen stocks in the drylands of Ethiopia

The study aimed at determining the effects of long-term irrigation practice on soil quality, soil organic carbon (SOC) and total Nitrogen (TN) stocks in the drylands of Ethiopia. Twenty composited and 18 undisturbed soil samples were collected from both irrigated and rain-fed plots at 0–30 cm soil depth. The collected soil samples were analyzed following standard procedures for soil property analysis. Data on soil quality parameters, SOC and TN were subjected to analysis of variance (ANOVA) and principal component analysis (PCA). Finally, soil quality index (SQI) as well as SOC and TN stocks were computed. The experimental results showed significantly higher value for most of the studied soil parameters in irrigated fields compared to the non-irrigated/rain-fed. Long-term irrigation increased SOC and TN stocks by 14.1% and 30%, respectively compared to the field under rain-fed production. A 40.1% increase in SQI was also recorded upon long-term irrigation practice. Overall, the study findings imply that shifting from rain-fed to irrigated production system improves soil quality, SOC and TN stocks in the long-run. For sustained development of the irrigated land use, further research on the impact of other factors such as irrigation method and salinity status of sub-surface soil layers is required.

The Current State of Irrigated Soils in the Central Fergana Desert under the Effect of Anthropogenic Factors

This article highlights the role of anthropogenic factors in the modern and stage-by-stage development of soils, using the meadow-marsh soils of Central Fergana as an example. Information on the anthropogenic evolution of desert subtropical soils under long-term irrigation is provided. Data on the component composition of readily soluble salts in soils are discussed. It has been revealed that marsh-meadow soils under the influence of long-term irrigation gradually evolve into the irrigated meadow-saz soils of deserts. It is necessary to organize and conduct monitoring, the results of which could be implemented for the selection of agricultural crops, the development of methods of their sowing and planting, and for development of soil protection methods. In the initial period of using hydromorphic soils for irrigation in desert landscapes, there is a decrease in humus and total nitrogen content. The agrogenic transformation of hydromorphic soils under long-term and intensive use leads to significant changes in a number of soil properties. Each region-specific, soil-climatic condition may have its own pattern of soil areal evolution which is closely linked with the geochemical landscapes and the dynamics of the soil fertility. It is therefore necessary to consider the trends of soil transformation and evolution to improve soil fertility.

Long-term tillage and irrigation effects on aggregation and soil organic carbon stabilization mechanisms

Sustainable soil management practices are required in agriculture to enhance carbon sequestration and restore soil functions. Here, the aim was to investigate the effect of different tillage practices combined with or without irrigation on (i) soil organic carbon (SOC) content, (ii) fungal biomass and their relationships with aggregate size classes in the soil surface layer; further, (iii) the concept of soil particle saturation with SOC was tested to evaluate if a threshold was reached in a 14 year-experiment. Our hypothesis was that long-term irrigation, intensive tillage and their combination, would negatively affect soil aggregation and SOC stabilization. The experiment has started in 2003 on a research farm in Canterbury, New Zealand. The present work focused on two contrasting tillage practices –intensive tillage with 20–25 cm ploughing (IT) and direct drill (DD)– combined with sprinkler-irrigated and non-irrigated (hereafter called Rainfed) conditions in a split-plot experimental design. Soil samples (0–5 cm layer) were analyzed for pore size distribution, specific surface area and microbial biomass. Further, wet sieving was used to isolate large macroaggregates (LM, > 2000 μm), small macroaggregates (SM, 250–2000 μm), microaggregates (m, 53–250 μm), particle sized silt + clay fractions (s+c, < 53 μm) and Fine20 particles (<20 μm), followed by the analysis of aggregate morphology and SOC quantification in them. Results showed that both DD and Rainfed management increased total SOC content of the bulk soil. Only the LM fraction and the SOC therein (OC-LM) increased significantly in DD compared to IT, while m and s+c fractions and OC-m and OC-s+c did not differ between treatments. Macroaggregate breakdown processes and measured SOC therein had likely not reached steady-state conditions, as suggested by the lack of any SOC differences in the aggregate size classes < 250 µm. In contrast, the Fines20:SOC ratio differentiated between soils that had reached (i.e., DD) or not reached (i.e., IT) the saturation threshold. Finally, it was observed that a higher fungal:bacteria (F:B) ratio was generally accompanied by a greater LM fraction and mean weight aggregate diameter, highlighting the importance of fungi in the formation of LM. These results suggested that our hypothesis of detrimental effects on soil aggregation and SOC accumulation of both tillage and irrigation was not fully demonstrated yet. A longer study period would be required to better understand the effects of such practices of SOC storage.

Xylem anatomical and hydraulic traits vary within crown but not respond to water and nitrogen addition in Populus tomentosa

Nitrogen (N) and water availability are the two crucial factors confining tree growth and forest productivity. Irrigation, fertilization, and combined fertigation are commonly applied to plantation forests for improving productivity. However, how xylem vasculature responds to these management practices remains poorly understood. Here we investigated the responses of tree growth, xylem anatomical structure, and hydraulics of the upper, middle, and lower canopy branches in a 6-year-old Populus tomentosa plantation subjected to four years of irrigation and fertigation treatments. The results showed that an improvement in tree growth only occurred in the irrigation treatment while the addition of N in fertigation treatments did not have a cumulative effect on tree growth. Most of the xylem anatomical traits, including vessel hydraulic diameter (Dh), vessel density (VD), vessel fraction (VF), double vessel wall thickness (t), potential specific sapwood hydraulic conductivity (Kp), fiber wall to lumen ratio (Tf/Df), vessel wall reinforcement (t/b)2, and wood density (WD) all showed conserved plasticity to long-term irrigation and fertigation, despite different tree growth rate, implying that aboveground biomass accumulation may have decoupled from the branch-level xylem traits. Besides, the alterations of other factors, including stomatal regulation strategy and crown structure with soil water and N availabilities, might better explain the variation in tree growth. In contrast, greater variations in branch xylem traits were detected across canopy layers. The upper canopy showed greater hydraulic safety characterized by narrower and denser vessels, higher cell wall to lumen ratio, and higher wood density compared to the lower canopy, while hydraulic efficiency (Kp) remained constant across the crown, thus highlighting the priority of hydraulic safety over efficiency in the construction of branch xylem. Overall, our study revealed the response pattern of P. tomentosa xylem structure to long-term water and N management, which facilitates a comprehensive understanding on the mechanisms underpinning the influence of water and nutrients regulation on the performance of fast-growing tree species’ plantations.

Prevention of degradation processes of soils irrigated with mineralized water through plastering

The long-term irrigation of extensive areas in the steppe zone of Ukraine using low-quality and mineralized water has caused degradation processes associated with soil salinization. To mitigate or alleviate these processes, researchers investigated the potential of chemical reclamation through the application of phosphogypsum. The study took place in the northern Steppe of Ukraine near the village of Oleksandrivka, Dnipro district, Dnipropetrovsk region. Over many years, field experiments were conducted, introducing phosphogypsum as a chemical meliorant. The experimental design included the application of phosphogypsum at rates of 1.4, 3.0, and 6.0 t/ha during different periods of the year. Standardized research methods were used for sampling, laboratory analysis, and processing of the results. The research identified a high salt content (0.35-0.48%) in the arable soil layer, signs of salinization (exchangeable sodium content of 3.64%), and unsatisfactory physical condition of the soil in the research areas. The application of phosphogypsum led to an increase in sulfate anions, as observed in the soil's sulfate chemistry, while the control areas exhibited a soda-sulfate type of salinity. The pH level of the water extract remained within neutral values throughout the years of the study. Positive changes were observed regarding the degree of soil salinity. Specifically, the application of phosphogypsum at rates of 3 and 6 t/ha in irrigated areas resulted in a change from moderate to slightly saline salinity levels. The research also demonstrated a positive effect on the sodium-adsorption ratio, particularly when phosphogypsum was applied during irrigation in the third year. The sodium-adsorption ratio decreased by 69% compared to the control options, indicating a better ameliorative effect of phosphogypsum during irrigation. Under the conditions of using water of class II quality for irrigation, the optimal application of phosphogypsum was found to be at doses of 3 t/ha for spring cultivation and 6 t/ha for the main cultivation in autumn. These application rates effectively reduced the degree of soil salinity and improved the ecological and meliorational conditions of the irrigated area

Drip Irrigation at a Soil Water Suction of 30 kPa Helps AMF and GRSP to Enhance Greenhouse Macro-Aggregates

Drip irrigation is fundamental in water-saving agricultural greenhouses, especially in tomato (Solanum lycopersicum L.) greenhouses. However, a long-term drip irrigation has been observed to be associated with soil degradation, concerning both soil aggregate structure and soil microbial community. To evaluate how drip irrigation scheduling influences the soil structure and arbuscular mycorrhizal fungi (AMF), a long-term irrigation experiment was carried out in a tomato greenhouse in 2011, using an irrigation program with dripping water starting when the soil reached a suction of 20 kPa (D20), 30 kPa (D30) and 40 kPa (D40). In 2017, we tested the AMF community and soil aggregate composition by soil wet sieving. Aggregates of 0.25–1 mm represented the main class of aggregates (32.4%–43.1%) in this experiment. At D30, we measured the highest mean weight diameter (MWD) and soil organic carbon (SOC) and glomalin-related soil protein (GRSP) levels. Thus, D30 promoted soil aggregate stability in the greenhouse. According to the high-throughput sequencing results of AMF, Glomus at D30 was the main factor leading to a high soil aggregate stability, because its OTU relative abundance was significantly higher than those of Ambispora and Paraglomus. Through redundancy analysis, the GRSP concentration was positively correlated with the SOC and total N (TN) levels and with the presence of the genera Ambispora, Glomus and Paraglomus. This evidenced that AMF and SOC helped to increase GRSP concentration and aggregate stability. Therefore, initiating irrigation when the soil reaches a water suction of 30 kPa could promote soil aggregate stability by favoring AMF abundance.

Characterizing spatial, diurnal, and seasonal patterns of agricultural irrigation expansion-induced cooling in Northwest China from 2000 to 2020

In the last two decades, agricultural irrigation areas expanded rapidly in arid Northwest China (NWC, including North and South Xinjiang and Hexi Corridor) and altered local and regional climates. However, the increasing irrigation's climatic effects with underlying biophysical mechanisms have rarely been investigated. Here we characterized the impact patterns of irrigation expansion on land surface temperature (LST) in NWC from spatial, diurnal, and seasonal dimensions from 2000 to 2020; we then decomposed the LST changes related to multiple biophysical components using the energy balance equation and quantified the contributions of albedo and evapotranspiration (ET) to LST changes based on partial correlation and dominance analyses. We found the space-and-time method can better represent the cooling effects of long-term irrigation expansion than the space-for-time method, despite that they derived similar cooling trends. The cooling effects were most evident in South Xinjiang, followed by North Xinjiang and Hexi Corridor, and varied in different irrigation expansion sources. Specifically, more intensive cooling occurred in new irrigated areas from unused lands (-0.69 ± 0.02 K) than that from grasslands (-0.47 ± 0.05 K) and forests (-0.28 ± 0.04 K). The cooling effects were dominated by marked daytime cooling compared to negligible nighttime warming. Seasonally, the cooling effects were concentrated in the growing season (May to September), especially in July and August. LST changes related to latent heat and sensible heat fluxes significantly surpassed other biophysical components. The changes in ET and albedo jointly modulated LST variations and increased ET dominated the daytime cooling effect (r = 0.52, p < 0.001) with a relative importance of over 55%, especially in North Xinjiang. But the ET-dominated cooling would be dampened by enhanced precipitation, implying the non-trivial impact of background climate. This study can provide important references for evaluating the climatic effects caused by irrigation expansion in arid regions and for improving the climate models.

РОЛЬ СЕВООБОРОТОВ В ПОДДЕРЖАНИИ АГРОФИЗИЧЕСКИХ СВОЙСТВ ЧЕРНОЗЕМОВ, ОРОШАЕМЫХ СЛАБОМИНЕРАЛИЗОВАННОЙ ВОДОЙ

Purpose: to determine effects of grain-fodder and vegetable crop rotation on the agrophysical properties of chernozems irrigated with low-mineralized water, in comparison with the non-irrigated counterpart. Materials and methods. The studies were carried out in Neklinovsky district Rostov region on ordinary chernozems in grain-fodder crop rotations, non-irrigated (without irrigation) and irrigated with annual irrigation rates of 1500–2500 cubic m/ha and in vegetable crop rotation with annual irrigation rates of 3000–4000 cubic m/ha. The source of irrigation is the Miussky estuary with low-mineralized water. Soil samples were taken in autumn after crop rotations, their granulometric texture, aggregate water stability and humus were determined. In profile pits - the soil bulk density. The selection of soil samples, their analysis and evaluation were carried out according to generally accepted methods. Results. The deterioration of water-physical properties was most clearly manifested during long-term irrigation with low-mineralized water on a plot with vegetable crop rotations, where irrigation rates were more than 3500 cubic m/ha. The arable land of such chernozem is highly compacted (1.41 t/cubic m), the bulk density 40 cm deeper is 1.45–1.47 t/cubic m. By granulometric texture, the upper soil layers acquired the properties of medium loamy soils due to the leaching of clay particles. There are practically no water-stable aggregates along the soil profile (about 10 %). Soil porosity deteriorated to excessively low values. Conclusions. Studies have shown that the higher the water load in crop rotations, the more the negative agrophysical properties of chernozems progress, especially when irrigated with low-mineralized waters.

Effects of long-term irrigation on soil phosphorus fractions and microbial communities in &lt;i&gt;Populus euphratica&lt;/i&gt; plantations

Effects of long-term irrigation on soil phosphorus fractions and microbial communities in &lt;i&gt;Populus euphratica&lt;/i&gt; plantations

Воздействие орошаемого свиноводческими стоками массива на поверхностные, грунтовые и подземные воды прилегающей территории

Purpose: to identify the impact of pig-breeding wastewater from the breeding-hybrid center (SGC) “Zadneprovsky”, Orsha district, Vitebsk region, on water bodies of the adjacent territory, namely on surface, ground and subsurface waters based on the results of many years of research, which gives an idea of the ecological state of the environment around large livestock complexes. Materials and methods: the influence of long-term irrigation with prepared pig wastewater has been edetermined based on studies of water quality samples from surface water sources near the complex, ground wells located at a distance of 800–1200 m from the area irrigated with wastewater, and from wells drilled to a depth of 80–230 m into the aquifer and located directly on the territory of the complex. Results. In the Krapivenka river, 500 m above the inflow of water from the Savishchino reservoir, ammonium nitrogen is found in an amount (mg per cubic dm) of 0.421 with a norm of 0.39, nitrite nitrogen – 0.025 with a maximum admissible concentration (MAC) of 0.024, phosphate phosphorus – 0.132 with a norm of 0.066 mg in cube dm. In the wells of the adjacent settlement of Krashino, located at a distance of 4600 m from the irrigation system of the Zadneprovsky SGC, excesses of MAC or nitrates were recorded. The nitrate content in well No. 1 was 1150 (mg per cubic dm), which is 25 times higher than the maximum admissible concentration. For wells No. 2 and 3, these values were 136 and 219, respectively, the excesses were 3 and 5 times. Exceeding the MAC for nutrients was not detected in subsurface water. Conclusions: pollution of surface waters located in close proximity to the pig-breeding complex is associated with violation of the technological regulations for storage and discharge of pig breeding wastewater. The increased content of nitrates in wells is due to their entry with groundwater, and pig waste does not have a significant impact on groundwater lying below the confining layer composed of clayey moraine deposits.

Effects of Mine Water Irrigation on Soil Salinity and Winter Wheat Growth

HighlightsMine water irrigation can promote the plant height growth of winter wheat, but inhibit the growth of leaf area.High salinity mine water irrigation will inhibit the growth and development of winter wheat and reduce the yield.Mixed irrigation of mine water and clean water (the ratio is 1:1) is beneficial to the growth of winter wheat.Short-term mine water irrigation will not cause soil salinization.Abstract. There is a serious shortage of irrigation water in the overlapped areas of crop and mineral production in North China. The key to solve the problem is to utilize mine water safely and efficiently. The effects of mine water irrigation (MI), mixed mine water and clean water irrigation (MIMC), rotational mine water and clean water irrigation, irrigated with mine water first, then clean water (RIMC) and clean water irrigation (CK) on winter wheat growth and soil salinity were studied through two years of field trials (2012 to 2014). The results showed that different models of mine water irrigation had no difference in plant height, but had obvious inhibitory effect on leaf area of wheat. Compared with CK, MI increased plant height by 1.0% to 3.4%, and leaf area was 69.5% to 81.9% of that of CK. Compared with CK, the yield of MIMC was increased by 2.6% to 6.67%, and the yield of RIMC and MI was decreased by 3.4% to 21.1% and 10.4% to 11.2%, respectively. The MI with high salinity could inhibit the growth and development of winter wheat, and reduce the yield and quality, while the yield of MIMC was higher than that of CK, and could improve the quality of winter wheat. Long-term irrigation of using mine water with high salinity will increase the risk of soil salinization, but MIMC can improve soil fertility. Keywords: Growth, Irrigation, Mine water, Soil salinity, Winter wheat.

Natural-human driving factors of groundwater salinization in a long-term irrigation area

Salinization of groundwater is a major challenge for groundwater management in long-term irrigation areas, decoupling its complex influencing factors can provide insights for the sustainable development of irrigation areas. In this study, the natural-human driving factors of groundwater salinization in the Yinchuan Plain, a typical irrigated area, were identified using isotope analysis, information entropy, and self-organizing map. Results show that groundwater in the study area is seriously salinized with obvious spatial heterogeneity. Multiple natural conditions and frequent human activities complicate the salinization characteristics of groundwater. On this basis, four typical natural influence units of groundwater were identified, namely, an evaporation and upward leakage zone, a runoff zone, an evaporation zone, and a runoff and upward leakage zone. Information entropy was proposed to quantify the complexity of groundwater resulting from human activities: The complexity difference between densely populated areas and natural dominant areas is mainly reflected in Na+, SO42−, and Cl−. Multiple human-made drivers of complex water environment were further separated into three patterns by the SOM model: blockage-evaporation type, leakage-evaporation type, and irrigation type. The blockage of drainage ditches and obstruction of salt discharge has the highest impact on the salinization of groundwater, followed by irrigation activities and transportation losses. Water excessive stagnation caused by blockage or irrigation is the root cause of groundwater salinization in the irrigated area, and its impact is greater than that of the traditional understanding of groundwater level rise. Based on the evaluation of irrigation water quality, management initiatives for irrigated areas should prioritize dredging and maintaining a healthy soil and groundwater environment in tandem.