Infiltration Of Irrigation Water Research Articles

Remote sensing monitoring of irrigated area in the non-growth season and of water consumption analysis in a large-scale irrigation district

Globally, water scarcity threatens food security, especially in arid and semi-arid food-producing regions, such as the Hetao Irrigation District (HID), where the water consumption during the non-growth season (spring irrigation, autumn irrigation) accounts for more than 30 % of the total irrigation volume. Meanwhile, mapping the characteristics of spatial and temporal evolution of the area of cropland irrigated in the spring and autumn and the pattern of water consumption is crucial for strengthening the management of agricultural water use. Evaporation and infiltration of irrigation water are difficult to capture in time due to insufficient timeliness or accuracy of single remote sensing data. This study integrates seven remote sensing datasets (Landsat5, Landsat7, Landsat8, HJ-1A/B, GF-1, Sentinel-2 and MODIS) for the first time to build a high spatial-temporal resolution dataset, and combines the water index NDWI and MNDWI to extract the maximum water range formed after irrigation by manually adjusting the threshold method. In addition to the global land use/cover dataset (GLC FCS30–1985_2020), the cropland layer was superimposed to accurately identify the cropland spring irrigation and autumn irrigation range from 2000 to 2021 in the HID. In the past 20 years, spring-irrigated (SI) areas increased by 1012.60 km2 (+49.96 %), and the autumn-irrigated (AI) areas decreased by 512.63 km2 (-11.02 %). Combined with the quantity of water diversion and displacement, the characteristics of irrigation water consumption in the non-growth season were further analysed. The results showed that the water consumption of spring irrigation increased by 0.67×108 m3 (+22.26 %), and that of autumn irrigation increased by 4.34×108 m3 (+38.82 %). The decrease of autumn- irrigated area and the increase of water consumption were mainly related to the stability of autumn irrigation water, imperfect irrigation and drainage conditions and insufficient field water management. In 2020­2021, the area of non-growth “autumn irrigation - spring irrigation” repeated irrigation is about 1271.52 km2, which can be used as a key control area. This study provides a theoretical basis and direction for rational water use in non-growth seasons of irrigation districts.

Development of a coupled surface water–groundwater model for the spatiotemporal simulation of river–aquifer interactions

AbstractIntegrating surface and groundwater use is a crucial part of water management. When one type of water is depleted, the other follows suit because of the constant movement and interaction between them. Therefore, the primary objective of this research is to establish a method by which the water evaluation and planning system (WEAP) surface water model and the MODFLOW groundwater model can communicate with one another. This article aims to demonstrate the interdependence of groundwater and surface water. Here, we use MODFLOW to model the saturated soil region and the soil moisture method to model the unsaturated soil region. The interaction between surface water and groundwater will affect the region's water resources and how they will operate under the continuance of existing practices. The simulation of saturated and unsaturated soil zones using a connected model of surface and groundwater employing all the hydroclimatology balance components is one of the most significant accomplishments of this research. The findings show that the (Iran) Sonqor Plain's maximum aquifer recharge throughout the months of November to May during a period of 30 years (October 1991 to September 2020) ranges between 1.5 and 2.6 million m³. A lack of recharge from irrigation water infiltration occurs in some of these months in addition to rain. The highest rate of groundwater level increase in this area is 4.5 m yr⁻¹ as a result of the distribution of irrigation water provided from the dam in the north‐western region.

Salinity distribution in agricultural land by geophysical, hydrochemical and geostatistical approaches: a pilot area located in Qelabshowah–Belqas, East Nile Delta region, Egypt

The study area is situated in the Qelabshowah–Belqas region, known for its Quaternary deposits. This research aims to demonstrate the two-dimensional (2D) variation of subsurface layers and salinity distribution using geoelectrical data, hydrochemical analysis, and geostatistical analysis. DC resistivity measurements were taken at fifteen vertical electrical sounding (VES) survey points using a Schlumberger array (AB/2 = 100 m) along three profiles. In addition, an electrical resistivity tomography (ERT) survey was conducted with a dipole–dipole array across one profile. Seven surface water samples were collected in the area. From the 1D and 2D inversion of VES and ERT data sets, three-to-four geoelectric layers were identified, including unconsolidated surface deposits, saturated clayey sand, saturated sand, and a salt-rich layer. The 2D inversion of VES data revealed an ancient salt-rich layer deposited in swampy conditions over a conductive wet sand layer along profile one due to salt mineral infiltration and dissolution. The 2D inversion of ERT data showed accurate lateral geometric accuracy compared to the 2D inversion of VES data, highlighting geological features, such as caves in the second layer and a buried water canal on the ground surface. Surface water samples showed high salinity levels with sodium hazards, indicating an Na–Cl composition. Geoelectric and hydrochemical data sets were geostatistically analyzed using spherical variogram supported ordinary Kriging interpolation. The analysis indicated weak to moderate spatial dependency for true resistivity parameters, while sodium content (SC) and permeability index (PI) showed strong spatial correlation. The 2D spatial distribution resistivity maps based on the 1D inversion of VES data displayed a general decrease in resistivity with depth, likely due to clay minerals or moist soil in the second layer and saline irrigation water infiltration in the third layer. The 2D spatial distribution of SC and PI showed a high concentration zone, posing a potential risk to agricultural crops regardless of soil permeability. It is recommended to use these maps when cultivating plants that can tolerate high sodium levels during the reclamation process.

Assessing the efficiency of the irrigation system in a horticulture field through time-lapse electrical resistivity tomography

AbstractThe characterization by means of geophysical techniques of agricultural soils subjected to continuous irrigation cycles makes it possible to study the heterogeneity of a soil and the preferential pathways of water flows without disturbing soil and plants. A better knowledge of soil heterogeneity enables optimal water resource management in terms of crop, yield, and sustainability. In this study, time-lapse monitoring using electrical resistivity tomographies (ERT) is proposed as a reliable and non-invasive technique to quantify the movement of water flows and thus the variation of soil water content during the irrigation process. ERT surveys have been conducted in melon-growing soils in southern Tuscany (Italy). Five survey campaigns have been carried out between June and August 2022, in which ERT data have been collected by taking measurements before (T0), during (T1), and after (T2) the irrigation phase. The interpretation of the ERT results provided information on the spatial and temporal distribution of water fluxes in the soil and root zone of melons during the irrigation phases. The investigation made it possible to identify the preferential pathways of infiltration of irrigation water, the points where water is absorbed by the roots, and the points where water follows a preferential pathway instead distributing itself entirely below the root growth zone. Thus, this research suggests that the ERT technique can be used to evaluate the efficiency of the irrigation system in order to achieve optimal management of the water resource, avoiding preferential flow paths that lead to less water availability for the plant.

Assessment of Soil Aggregate Stability Methodologies in Calcareous Silt Loams

Highlights Three methods were used to measure soil aggregate stability in the calcareous silty loam soils of Idaho’s Magic Valley. No treatment differences were found using traditional wet sieving or SLAKES methods. Cornell Sprinkle Infiltrometer was more sensitive to the treatments compared to the other two methods. Abstract. Idaho’s Magic Valley is a highly productive agricultural region in the United States due to irrigation. The soils in this region are prone to crusting, have low organic matter, and are high in calcium carbonates, making them susceptible to erosion and water runoff. Soils need to be better managed to enhance aggregate stability to enable increased infiltration of irrigation water and decreased soil erosion in nearby waterways. However, to make management recommendations, the identification of appropriate measurements of aggregate stability needs to be identified, and few relevant studies exist. Thus, the overall goal of this project was to identify appropriate methods for the assessment of soil aggregate stability in the study region. The study sites were located in Southern Idaho and set up using common cropping rotations and agricultural management practices for the region using a variety of nutrient sources, tillage types, and cover cropping. Three methods were used to measure soil aggregate stability: wet sieving, simulated rainfall using a Cornell Sprinkle Infiltrometer (sprinkler height: 30, 90, and 150 cm), and the SLAKES mobile application. No differences in soil aggregate stability were found when the wet sieving or SLAKES methods were used at the three study sites, either due to the method or a general lack of differences between treatments. When using the Cornell Sprinkle Infiltrometer, no treatment differences were found at LT-Manure or GRACEnet; however, differences were observed between treatments at the Cover Crop study site at sprinkler heights of 30 and 90 cm. At a sprinkler height of 30 cm, the average mean weight diameter was the highest when winter forage crops (WFC) and solid dairy manure (SDM) were applied (3.73 mm) and the lowest in the control (3.12 mm). At a sprinkler height of 90 cm, the average mean weight diameter was the highest when WFC and SDM were applied (3.54 mm) and the lowest in the WFC Only treatment (2.46 mm). These results not only have implications for which methods are best for assessing progress but also for what management practices can be utilized to decrease soil erosion from irrigated cropland. This study highlighted that under these soils and management practices, simply increasing soil carbon does not increase aggregate stability, especially when root crops are included in the crop rotation with intensive tillage. In arid and semi-arid regions, the Cornell Sprinkle Infiltrometer may be a more sensitive method of measuring soil aggregate stability compared to traditional wet sieving. Keywords: Agricultural management practices, Calcareous soils, Mean weight diameter, Slake test, Soil aggregate stability.

Nitrate Source and Transformation in Groundwater under Urban and Agricultural Arid Environment in the Southeastern Nile Delta, Egypt

With the intensification of human activities, nitrate pollutants in groundwater are receiving increasing attention worldwide. Especially in the arid Nile Delta of Egypt, groundwater is one of the most valuable water resources in the region. Identifying the source of nitrate in groundwater with strong human disturbances is important to effective water resource management. This paper examined the stable isotopes (δ15N/δ18O-NO3 and δ2H/δ18O-H2O) and the hydrogeochemical parameters of the shallow groundwaters in the arid southeast of the Nile Delta to assess the potential sources and transformation processes of nitrate under severe urban and agricultural activities. The results revealed that the groundwaters were recharged by the Nile River. Meanwhile, the infiltration of irrigation water occurred in the west, while the mixing with the deep groundwater occurred in the east regions of the study area. The TDS, SO42−, NO3−, and Mn2+ concentrations of groundwaters (n = 55) exceeded the WHO permissible limit with 34.6%, 23.6%, 23.6%, and 65.5%, respectively. The NO3− concentrations in the shallow groundwaters ranged from 0.42 mg/L to 652 mg/L, and the higher levels were observed in the middle region of the study area where the unconfined condition prevailed. It extended to the deep groundwater and eastward of the study area in the groundwater flow direction. The δ15N-NO3 and δ18O-NO3 values suggested that the groundwater NO3− in the west and east regions of semi-confined condition were largely from the nitrification of soil organic nitrogen (SON) and chemical fertilizer (CF). In contrast, wastewater input (e.g., domestic sewage and unlined drains) and prevalent denitrification were identified in the middle region. The denitrification might be tightly coupled with the biogeochemical cycling of manganese. This study provides the first report on the groundwater NO3− dynamics in the Nile Delta, which generated valuable clues for effective water resource management in the arid region.

A hydrochemical and isotopic approach for source identification and health risk assessment of groundwater arsenic pollution in the central Yinchuan basin

Arsenic contamination of groundwater is becoming a major global issue as it can severely affect the safety of drinking water and human health. In this paper, 448 water samples were investigated to study the spatiotemporal distribution, source identification and human health risk of groundwater arsenic pollution in the central Yinchuan basin by applying a hydrochemical and isotopic approach. The results showed that arsenic concentrations in groundwater ranged from 0.7 μg/L to 26 μg/L with a mean of 2.19 μg/L, and 5.9% of samples were above 5 μg/L, indicating the arsenic pollution of groundwater in the study area. High arsenic groundwater was mainly distributed in the northern and eastern areas along the Yellow river. The main hydrochemistry type of high arsenic groundwater was HCO3·SO4–Na·Mg, and the dissolution of arsenic-bearing minerals in sediment, irrigation water infiltration and aquifer recharge from the Yellow river were the main sources of arsenic in groundwater. The arsenic enrichment was dominantly controlled by the TMn redox reaction and the competitive adsorption of HCO3−, and the influence of anthropogenic activities was limited. The health risk assessment suggested that the carcinogenic risk of As for children and adults greatly exceeded the acceptable risk threshold of 1E-6, displaying a high carcer risk, while the non-carcinogenic risks of As, F−, TFe, TMn and NO3− in 2019 were largely higher than the acceptable risk threshold (HQ > 1). The present study provides insight into the occurrence, hydrochemical processes and potential health risk of arsenic pollution in groundwater.

Роль и динамика инфильтрации в структуре влагообмена зоны аэрации орошаемого поля

Purpose: scientific and technical substantiation of the water balance components of an irrigated field in the particular case of connecting an aquifer and an aeration zone through a capillary fringe. Materials and methods. The research was carried out at Pobeda LLC, Bagaevsky district, Elkin farmstead, in 2018 and 2019. When organizing the research, an integrated approach was used: stationary and experimental sites were used. The climatic conditions of the research objects correspond to the semi-arid steppe zone, the soils are southern chernozems. Results. As a result of processing data from field experience, it was determined that with infiltration varying from 0.183 to 1.915 mm: the average daily water supply ranged from 0.8 to 7.33 mm/day; relative moisture reserves – from 0.61 to 1.20; average daily air temperature – from 8.0 to 23.0 °C; average daily air humidity deficit – from 2.1 to 12.0 mbar; average daily evaporation – from 1.3 to 7.34 mm/day. The correlation analysis determined that, according to the correlation coefficient, the infiltration value has the greatest correlation – 0.86 and 0.63 with water supply (M + P) and relative moisture reserves (W0), respectively; the smallest – 0.28; 0.38 and 0.37 with temperature (t), air humidity deficit (dφ) and evaporation (Eω), respectively. In turn, the multifactor correlation analysis determined that the formation of the infiltration runoff volume in the system of vertical moisture exchange of an irrigated field has the greatest connection with a paired change in the values of water supply and relative moisture reserves. Conclusions: infiltration of irrigation water and atmospheric precipitation beyond the root layer is determined by the obtained empirical dependence, is observed when the moisture reserves of this layer exceed the moisture reserves corresponding to the minimum moisture capacity and water supply, and has the greatest close relationship according to the coefficient of multiple determination (R²) 81 % (multiple correlation coefficient R = 0.899) with changes in these two factors.

Research on soil physical characteristics and dynamic response of groundwater to irrigation in typical irrigation area of Huangshui River Basin

Under the influence of the natural and human factors, water table of irrigated area Changes frequently, but it is mainly affected by irrigation water infiltration replenishment. Basic physical properties of different soil layer of the typical field were determined and analyzed, and 5 groundwater observation wells were constructed to carry out the experiment of the response of groundwater to irrigation. The results showed that the upper vertical 0-40 cm is loose, the 40-60 cm layer is relatively tight, and the lower part 60-200 cm tend to loose again. Soil saturated water holding capacity, capillary water holding capacity and field capacity showed increased first and then decreased trend with the increase of soil depth. They almost showed the same nearly evenly spaced degressive trend. The groundwater stage dynamic change rule of spring and seedling irrigation stage in the typical plot was fit to the hydrological geology condition of grade-Iterrace of Huangshui river valley. Lateral canal water direction formed a line effect. The rangeability of water table of spring irrigation period was significantly higher than that of seedling irrigation period.

Nonlinear site response analysis approach to investigate the effect of pore water pressure on liquefaction in Palu

On 28 September 2018, a M w 7.5 earthquake hit Donggala Regency, Indonesia province of central Sulawesi, resulting in extensive liquefaction, land subsidence, and flow slides. Extensive liquefaction is caused by an increased development of pore water pressure. During an earthquake, the development of pore water pressure (PWP) causes soil to become soft and potential liquefaction on loose sands. A PWP development model was combined with a generalized/Hyperbolic constitutive model (GQ/H+PWP) in a one-dimensional seismic site response to investigate pore water pressure development beneath the soil layer. This model provided reasonable estimates of pore water pressure increase and stress-strain role. Analysis was carried out for three boreholes in Balaroa, Petobo, and Jono Oge sites. The effective stress approach, nonlinear site response analysis was used to conduct a parametric study of soil profiles. The potential liquefaction at Balaroa and Petobo sites were 9 m and 10 meters in depth, respectively. With a groundwater level of 14 meters below the ground surface, the liquefaction potential in Jono Oge was 16-17 meters in depth. These results indicated that the liquefaction potential in Jono Oge was influenced by the infiltration of irrigation water from the surface which caused liquefaction to occur on the ground surface.

Groundwater Geochemistry and its Impacts on Groundwater Arsenic Enrichment, Variation, and Health Risks in Yongning County, Yinchuan Plain of Northwest China

High arsenic (As) groundwater is a serious environmental problem in Yinchuan Plain, northwest China. Though some measures have been taken to alleviate it, the detection rate of high As in groundwater is still high. In order to understand the occurrence and enrichment of As in groundwater and the hydrochemical evolution, correlation analysis and interpolation approach were used to interpret the spatiotemporal variation of major ions and contaminants in phreatic groundwater at 30 sampling sites during the dry season (March) and wet season (July). Some suggestions on the treatment of groundwater As pollution in the study area were put forward. The results reveal that the predominant hydrochemical type of groundwater in the study area is SO4·Cl-Ca·Mg, followed by HCO3-Ca·Mg type, and rock weathering is the main process regulating the hydrochemical characteristics. The content of groundwater As is low in the dry season but high in the wet season. However, the difference of As concentration between the dry and wet seasons is relatively small in the areas where surface water percolation is intense. The concentrations of HCO3−, NH4+, PO43−, and Mn have a significantly positive correlation with the As enrichment in the dry season, while HCO3−, Fe, and Mn have a strongly negative correlation with As in the wet season. The content of As in surface water influences greatly to the As enrichment in groundwater. In the dry season, high arsenic is enriched in areas close to surface water, while in the wet season, the infiltration of irrigation water makes arsenic expand to the western agricultural irrigation area. The mean lung cancer risk caused by As is higher than the maximum acceptable level in the study area. As such, necessary actions such as adopting nanocomposites as As removal material are to be carried out.

Inflation of water to the soil in the fields of drop irrigation

The article presents theoretical and field experimental data on determining the rates of infiltration and filtration of irrigation water in the soil - grounds of the calculated layer in the cotton fields of the Dzharkurgan massif in the Surkhandarya region. Based on the established values of the rates of infiltration of irrigation water, the drip irrigation regime for cotton of the new Sultan variety has been determined, the parameters of the innovative drip irrigation technology have been determined.

Study of irrigation characteristics and improvement of irrigation techniques using interpolymer complex-based anti-filtration screen

In the world, special attention is paid to targeted research on water resources management and efficient use of irrigation water resources. In this regard, one of the main tasks is to improve the technique of irrigation of fields using cheap chemical and technical means, the development of new methods of water-saving irrigation, the development of the theory of water-saving technologies in irrigation of fields. In this regard, the use of inexpensive interpolymers to reduce soil composition and irrigation water infiltration is of particular importance.

Irrigation water infiltration modeling using machine learning

The present study proposes five standard artificial intelligence models including Artificial Neural Network (ANN), Adaptive Neuro-Fuzzy Inference System (ANFIS), Group Method of Data Handling (GMDH), Multivariate Linear Regression (MLR), and Support Vector Regression (SVR) as well as their integrative models combined with the nature-inspired Firefly Algorithm (FA) to forecast the infiltrated water in the furrow irrigation system. The FA functions as an optimizer tool in constructing the integrative models. Data for assessing these models was gathered from published literatures and field experiments conducted on researching farm at SBUK University, Kerman, Iran. The input parameters used in modeling were furrow length (L), the inflow rate (Q), advance time at the end of the furrow (TL), cross-sectional area of inflow (Ao) and infiltration opportunity time (To). The root mean square (RMSE), the mean absolute error (MAE), the correlation coefficient (R2), the Nash–Sutcliffe efficiency index (NSE), and the index of agreement (IA) were used to evaluate the predicting performance of the suggested models. The best values of the statistical criteria and in training and testing phase of the simulation imply that the MLPNN-FA and SVR-FA provided an excellent fit to the observed data. Comparison of the results revealed that the FA is able to boost the accuracy of the models so that the improvement in RMSE values was 5%, 1%, 4%, 47% in the ANFIS, GMDH, MLPNN, and SVR, respectively. Having the calculated value for the comprehensive synthesis index (SI) indicated that using the combination of the SVR and FA noticeably enhance the performance of the standard SVR model by 97%. Even though the FA algorithm had a trivial influence on the GMDH model; however, it can be introduced as a powerful tool to enhance the complicated modeling processes.

An Experimental and Numerical Study of Landslides Triggered by Agricultural Irrigation in Northwestern China

Chinese Loess Plateau (CLP) has become one of the high‐incidence areas of landslide disasters in China, especially at the edge of the tablelands where irrigation has been practiced at a large scale since the 1960s. Heifangtai tableland, located in the CLP in Yongjing County, Gansu Province, has been selected as a case, where more than 90 slidings occurred in the past three decades. Field monitoring and laboratory tests were conducted to obtain the soil‐water characteristic curve, unsaturated soil shear strength, irrigation water infiltration, and the groundwater level change. Based on these results, a three‐dimensional numerical model of the slope was established, and the change of seepage field and slope stability before and after irrigation was investigated using simulations and compared with the observed data. The results show that flood irrigation raised the water table, and the increase of soil moisture in the flooded area was more significant than that in the nonirrigated area. The rising speed of the groundwater level was about 0.25 m/yr, with an amplitude of 0.5 m. Near the slope, the hydraulic gradient of the concave slope was steeper than the convex slope. The shear strength of the loess decreased with increasing soil moisture, and the tensile strength was about 15% of the cohesion. Numerical results showed that after three years of continuous flood irrigation at the back of the slope, the slope stability coefficient decreased by 0.12. After irrigation, the potential slip zone slightly expanded. The reason why landslides often occurred at the back of the gully or the landslide was that the water table was shallower on concave slopes and the soil moisture of the concave slopes was more susceptible to irrigation.

Straw layer burial to alleviate salt stress in silty loam soils: Impacts of straw forms

Salt stress can be alleviated by straw layer burial in the soil, but little is known of the appropriate form of the straw layer for optimal regulation of soil water and salinity because of the uncontrollability of field tests. Here, the following four straw forms with compaction thickness of 5 cm buried 40–45 deep were studied: no straw layer (CK), segmented straw (SL, 5 cm in length), straw pellet (SK), and straw powder (SF). The three straw forms (SL, SK and SF) significantly delayed the infiltration of irrigation water down the column profile by 71.20–134.3 h relative to CK and the migration velocity of the wetting front under SF was the slowest. It took longer for the wetting front to transcend SK than SL but shorter for it to reach the bottom of soil column after water crossed the straw layer. Compared with CK, the average volumetric water content in the 0–40 cm soil layer increased by 6.45% under SL, 1.77% under SK and 5.39% under SF. The desalination rates at the 0–40 and 0–100 cm soil layers increased by 5.85 and 3.76% under SL, 6.64 and 1.47% under SK and 5.97 and 4.82% under SF. However, there was no significant difference among straw forms in the 0–40 cm soil layer. Furthermore, the salt leaching efficiency (SLE, g mm−1 h−1) above the 40 cm layer under SL was 0.0097, being significantly higher than that under SF (0.0071) by 37.23%. Salt storage under SL, SK and SF in the 40–45 cm layer accounted for 4.50, 16.92 and 7.43% of total storage in the 1-m column profile. Cumulative evaporation under SL and SF decreased significantly by 41.20 and 49.00%, with both treatments having the most significant inhibition of salt accumulation (resalinization rate being 36.06 and 47.15% lower than CK) in the 0–40 cm soil layer. In conclusion, the different forms of straw layers have desalting effects under high irrigation level (446 mm). In particular, SL and SF performed better than SK in promoting deep salt leaching and inhibiting salt accumulation on the soil surface. However, SL was simpler to implement and its SLE was higher. Therefore, the segmented 5 cm straw can be recommended as an optimum physical form for establishing a straw layer for managing saline soils for crop production.

Dynamic Simulation of Soil Salt Transport in Arid Irrigation Areas under the HYDRUS-2D-Based Rotation Irrigation Mode

This research aims to explore the dynamic transport of water and salt in soil under different irrigation modes and disclose the desalting effect of different irrigation factors in inland arid irrigation areas. Jingdian Irrigation District in Gansu Province, which is located in the arid region of Northwest China, is selected as a typical experimental area. Soil water and salt dynamic migration model is constructed based on HYDRUS-2D software, and field irrigation experiments are designed according to actual irrigation conditions in crop growth period. The model is used to simulate the salt transport process between saturated soil and unsaturated soil as well as the effects of different irrigation quotas, irrigation rounds and quota allocations on soil desalting. Through simulation, the vertical movement pattern of water and salt in the soil of the test area is analyzed, and the optimal design of the soil desalting irrigation plan is carried out. The results demonstrate that: after two-round irrigation, the average soil salinity of the tillage layer at each test points decreases significantly under evapotranspiration; the infiltration of irrigation water has an obvious impact on soil desalting; the deviation between the simulated and the measured value is less than 0.5%, which proves the model fitting result reliable; with fixed irrigation cycle and times, the soil desalting efficiency is higher when the irrigation quota falls in the range of 4000 ~ 6000 m3/hm2; when the first round of irrigation water only saturates the moisture content and gradually increases the irrigation quota in the subsequent rounds, it is more conducive to the dissolution and discharge of soil salinity. In summary, the results of this study can provide technical support for the protection of water and soil resources, as well as the improvement of saline-alkali land in inland arid irrigation areas.

Dynamics and Distribution of Soil Salinity under Long-Term Mulched Drip Irrigation in an Arid Area of Northwestern China

Mulched drip irrigation has been widely used in agricultural planting in arid and semi-arid regions. The dynamics and distribution of soil salinity under mulched drip irrigation greatly affect crop growth and yield. However, there are still different views on the distribution and dynamics of soil salinity under long-term mulched drip irrigation due to complex factors (climate, groundwater, irrigation, and soil). Therefore, the soil salinity of newly reclaimed salt wasteland was monitored for 9 years (2008–2016), and the effects of soil water on soil salinity distribution under mulched drip irrigation have also been explored. The results indicated that the soil salinity decreased sharply in 3–4 years of implementation of mulched drip irrigation, and then began to fluctuate to different degrees and showed slight re-accumulation. During the growth period, soil salinity was relatively high at pre-sowing, and after a period of decline soil salinity tends to increase in the late harvest period. The vertical distribution of soil texture had a significant effect on the distribution of soil salinity. Salt accumulated near the soil layer transiting from coarse soil to fine soil. After a single irrigation, the soil water content in the 30–70 cm layer under the cotton plant undergoes a ‘high–low–high’ change pattern, and the soil salt firstly moved to the deep layer (below 70 cm), and then showed upward migration tendency with the weakening of irrigation water infiltration. The results may contribute to the scientific extension of mulched drip irrigation and the farmland management under long-term mulched drip irrigation.

Infiltration of irrigation water and energy saving test of maize

In view of the existing under mulch drip irrigation frequency, high energy consumption, low utilization rate of shallow soil moisture, plastic pollution problem, the irrigation infiltration characteristics of subsurface drip irrigation on irrigation with depth, irrigation quota, irrigation frequency, sowing depth of 4 factors and 3 levels for infiltration irrigation and CK1 orthogonal method (drip irrigation sowing depth of 5 cm), CK2 (sowing depth 5 cm membrane infiltration depth 15 cm) contrast test of maize field. The results show that: (1) no membrane infiltration irrigation corn average germination rate is 94.2% and the average germination rate of CK1 and CK2 between 97% and 95%, growth stage of maize plant height, leaf area index, root length, root dry weight, root diameter, cell physiology section was lower than that of CK1 and CK2, but with the difference of fertility to corn especially the mid asymptotic root length, root dry weight was higher than that of the control, the growth of normal corn sowing; (2) moisture infiltration irrigation quota of 4200 m3/hm2 irrigation 7 times, reduced by 30% and 7% respectively compared with CK1 irrigation with 10 times irrigation quota of 4500 m3/hm2, but the maize were significantly increased by 25.23%, and CK2 were not obviously, infiltration irrigation can reduce the irrigation frequency water quota and energy saving; (3) infiltration irrigation soil moisture and crop water consumption intensity showed a small increase in topsoil, lower steady state and just on the contrary, reflects the infiltration of irrigation soil moisture soil moisture diffusion drying operation Small and deep moisture effect, provides a useful exploration for energy-saving and environment-friendly agricultural efficient water-saving irrigation quality and efficiency.

Preferential flow pathways in paddy rice soils as hot spots for nutrient cycling

Crop rotations with maize and flooded rice lead to temporally aerobic soil conditions. This promotes the development of desiccation cracks in the soil, which can act as preferential flow pathways for water and solutes. We hypothesized that these cracks are enriched with organic carbon (C), plant nutrients and microbial residues (amino sugars) and that they can thus also serve as hot spots of fertilizer and C cycling. To test this hypothesis, we applied 13C-labelled rice straw and 15N-labelled urea to rice fields of the International Rice Research Institute (Los Baños, Philippines). We then traced the fate of the 13C-labelled rice straw and the 15N-labelled urea in crack and bulk soil and in microbial residues in two approaches, i) in the short term, i.e., 24 h after application of straw and fertilizer jointly with a dye tracer (Brilliant Blue) prior to maize seeding in the paddy - maize cropping system, as well as ii) in the long-term, i.e., during one year and for three different crop rotations (continuous paddy rice, paddy rice – maize, and paddy rice – maize with straw mulching and cover cropping). The short-term analyses of the dye tracer depth profiles showed that flow path areas decreased with increasing depth. A typical impermeable plough pan was not identified. Instead, we observed rapid infiltration of irrigation water down to 60 cm soil depth. The dyed flow paths were enriched in organic C (+12%) and plant nutrients (N: +21%, Ca2+: +59%, K+: +39%, Mg2+: +39%) relative to the bulk soil. The labelled straw and fertilizer quickly reached 60 cm depth with the dye tracer. We could not identify elevated microbial biomass along the flow paths, however, we did find larger microbial activities along the cracks in the long-term experiment than in the surrounding bulk soil. The increased activity fostered microbial uptake of fertilizer 15N along the cracks, which was detected mainly for fungal residues and only in the trials receiving straw (crack soil: 0.6 ± 0.1 mg glucosamine-15N kg soil−1, bulk soil: 0.2 ± 0.1 mg glucosamine-15N kg soil−1). We conclude that analysis of homogenized bulk soil samples can underestimate C and nutrient availability, as well as their microbial processing in paddy rice soils, when crack systems are not considered.