Plain Irrigation Research Articles

Examining Crop Yield Losses in Iğdır Plain Irrigation Systems in Türkiye Amidst Water Constraints

Water stands as a crucial component of agricultural production. This study aims to propose water efficiency measures in agriculture as an essential element for climate change adaptation. In this study, yield losses in staple crops in agricultural regions are analyzed by using the most suitable methodologies, particularly in agriculture-reliant developing nations. Furthermore, this study seeks to determine the financial consequences of such losses. The methodology applied for this purpose was implemented in Türkiye’s Iğdır Plain, selected as the study site. As the first step, the yields of the first three most cultivated products in each product group were assessed under normal climatic conditions in terms of their crop water requirements and irrigation water requirements. Subsequently, the irrigation water supply was reduced by 10%, and the resulting yield losses were calculated per hectare. Then, the overall crop losses after applying the 10% water constraint were determined in the total cultivation area. Among the crops cultivated in the region, the analysis reveals that clover from the field crops category exhibits the highest water dependence, while apricot demonstrates the least reliance on water resources. As a result, the recommended crop rotation for the Iğdır Plain under water constraints comprises wheat, apricot, watermelon, maize, melon, apple, tomato, peach, and clover. The following measures are proposed to ensure sustainable use of water resources and reduce exposure to climate change: increasing the water transmission efficiency and water use efficiency in irrigation areas, allocating more space to water-stress-resistant crops in the crop pattern in basins, and substituting crops requiring excessive water with less water-dependent crops.

Assessing the Convective Environment over Irrigated and Nonirrigated Land Use with Land–Atmosphere Coupling Metrics: Results from GRAINEX

Abstract Land-use land-cover change affects weather and climate. This paper quantifies land–atmosphere interactions over irrigated and nonirrigated land uses during the Great Plains Irrigation Experiment (GRAINEX). Three coupling metrics were used to quantify land–atmosphere interactions as they relate to convection. They include the convective triggering potential (CTP), the low-level humidity index (HIlow), and the lifting condensation level (LCL) deficit. These metrics were calculated from the rawinsonde data obtained from the Integrated Sounding Systems (ISSs) for Rogers Farm and York Airport along with soundings launched from the three Doppler on Wheels (DOW) sites. Each metric was categorized by intensive observation period (IOP), cloud cover, and time of day. Results show that with higher CTP, lower HIlow, and lower LCL deficit, conditions were more favorable for convective development over irrigated land use. When metrics were grouped and analyzed by IOP, compared to nonirrigated land use, HIlow was found to be lower for irrigated land use, suggesting favorable conditions for convective development. Furthermore, when metrics were grouped and analyzed by clear and nonclear days, CTP values were higher over irrigated cropland than nonirrigated land use. In addition, compared to nonirrigated land use, the LCL deficit during the peak growing season was lower over irrigated land use, suggesting a favorable condition for convection. It is found that with the transition from the early summer to the mid/peak summer and increased irrigation, the environment became more favorable for convective development over irrigated land use. Finally, it was found that regardless of background atmospheric conditions, irrigated land use provided a favorable environment for convective development.

Winter irrigation in Indo-Gangetic Plain heightens fog in Delhi

Winter irrigation in Indo-Gangetic Plain heightens fog in Delhi

Irrigated Agriculture Significantly Modifies Seasonal Boundary Layer Atmosphere and Lower-Tropospheric Convective Environment

Abstract Modification of grasslands into irrigated and nonirrigated agriculture in the Great Plains resulted in significant impacts on weather and climate. However, there has been lack of observational data–based studies solely focused on impacts of irrigation on the PBL and convective conditions. The Great Plains Irrigation Experiment (GRAINEX), conducted during the 2018 growing season, collected data over irrigated and nonirrigated land uses over Nebraska to understand these impacts. Specifically, the objective was to determine whether the impacts of irrigation are sustained throughout the growing season. The data analyzed include latent and sensible heat flux, air temperature, dewpoint temperature, equivalent temperature (moist enthalpy), PBL height, lifting condensation level (LCL), level of free convection (LFC), and PBL mixing ratio. Results show increased partitioning of energy into latent heat relative to sensible heat over irrigated areas while average maximum air temperature was decreased and dewpoint temperature was increased from the early to peak growing season. Radiosonde data suggest reduced planetary boundary layer (PBL) heights at all launch sites from the early to peak growing season. However, reduction of PBL height was much greater over irrigated areas than over nonirrigated croplands. Relative to the early growing period, LCL and LFC heights were also lower during the peak growing period over irrigated areas. Results note, for the first time, that the impacts of irrigation on PBL evolution and convective environment can be sustained throughout the growing season and regardless of background atmospheric conditions. These are important findings and applicable to other irrigated areas in the world. Significance Statement To meet the ever-increasing demand for food, many regions of the world have adopted widespread irrigation. The High Plains Aquifer (HPA) region, located within the Great Plains of the United States, is one of the most extensively irrigated regions. In this study, for the first time, we have conducted a detailed irrigation-focused land surface and atmospheric data collection campaign to determine irrigation impacts on the atmosphere. This research demonstrates that irrigation significantly alters lower atmospheric characteristics and creates favorable cloud and convection development conditions during the growing season. The results clearly show first-order impacts of irrigation on regional weather and climate and hence warrant further attention so that we can minimize negative impacts and achieve sustainable irrigation.

Impacts of irrigation on a precipitation event during GRAINEX in the High Plains Aquifer Region

Land use land cover change, including irrigation, impacts weather and climate. In this paper a precipitation event that occurred on the morning of 23 July 2018 during the Great Plains Irrigation Experiment (GRAINEX) is investigated. Six Weather and Research Forecasting (WRF) model-based experiments were conducted, which involved the increase or decrease of soil moisture by 5 % and up to 15 % over the irrigated croplands. These changes approximated soil moisture content in response to different levels of irrigation applications. An additional experiment, where irrigated land use was changed to grassland, was conducted to capture pre-irrigation land use and its impacts. It was found that regardless of strength of irrigation, precipitation decreased. In addition, the model did not produce precipitation over non-irrigated land use. When grassland replaced irrigated agriculture, increases in precipitation were estimated. With increased irrigation, latent heat flux increased compared to the control simulation and decreased when irrigation decreased. On the other hand, sensible heat flux was decreased compared to control when irrigation increased. The planetary boundary layer over irrigated land use was shallower than over non-irrigated land use while over grassland it was higher than irrigated but lower than non-irrigated land use. The changes in precipitation, the surface energy balance, and the planetary boundary layer served as a reminder of irrigation's complex effects on the atmosphere. Additional analysis of other precipitation events during GRAINEX would be helpful to better understand the effects of irrigation.

Effects of straw return with potassium fertilizer on the stem lodging resistance, grain quality and yield of spring maize (Zea mays L.)

This experiment aimed to study the effects of straw return combined with potassium fertilizer on stem lodging resistance, grain quality, and yield of spring maize. The objective was to provide a scientific basis for the rational utilization of Inner Mongolia spring maize straw and potassium fertilizer resources. The test material used was ‘Xianyu 335’, and the study was conducted in three ecological regions from east to west of Inner Mongolia (Tumochuan Plain Irrigation Area, Hetao Plain Irrigation Area, and Lingnan Warm Dry Zone). A split-plot design was employed, with the straw return method as the main plot and potassium fertilizer dosage as the secondary plot. We determined the stem resistance index, grain quality, and yield. The results showed that both straw return and potassium application improved stem lodging resistance, grain quality, and maize yield. Combining straw return with the reasonable application of potassium fertilizer enhanced the effectiveness of potassium fertilizer, increased lodging resistance, maize yield, and improved grain quality and yield stability. Under the straw return treatment, with potassium application compared to no potassium application, significant increases were observed in maize plant height, stem diameter, dry weight of stems, stem compressive strength, stem bending strength, grain protein content, yield, straw potassium accumulation content, and soil available potassium content. These increases were up to 30.79 cm, 2.63 mm, 15.40 g, 74.93 N/mm2, 99.65 N/mm2, 13.68%, 3142.43 kg/hm2, 57.97 kg/hm2, and 19.80 mg/kg, respectively. Therefore, the interaction of straw return and potassium fertilizer was found to be the most effective measure for maintaining high-yield and stress-resistant cultivation, improving grain quality, and optimizing the management of straw and potassium fertilizer resources. This approach is suitable for promotion and application in the spring maize growing areas of Inner Mongolia.

Research on water quality improvement of plain irrigation area based on multi-scenario simulation.

Water diversion projects have proven to be effective interventions to improve water quality in irrigation ditches. This study focused on quantifying the water quality improvement by utilizing a hydrodynamic water quality model in Funing County, Yancheng City. The model performed a spatial analysis of pollution concentrations across the study area. Various optimization scenarios were designed based on the diversion project and hydrological structure connectivity. The model was used to simulate changes in nutrient concentrations under different scenarios. The findings of this study were as follows: (1) Rural areas had lower nutrient concentrations and superior hydrological connectivity than urban areas. (2) The effect of water quality improvement correlated positively with increased flow rates introduced by the diversion project. Specifically, when the flow rate increased by 50%, the average reductions were 20% for NH4+, 5.2% for TN, and 5.1% for TP. Furthermore, introduced clean water led to more pronounced improvements in the overall regional water quality. (3) Although increasing the number of ditches improved water pollution concentration, the impact was not significant. (4) Model simulation results showed that 18 to 45% water diversion intensity effectively improved water quality, and the optimal water diversion intensity was 27 to 30%. The optimal water diversion intensities offered valuable insights for managing this region. The study's methods contributed to the promotion of sustainable development in regional water resources and the integrated management of the water environment.

Characterization of the marine‐air intrusion Marinada in the eastern Ebro sub‐basin

AbstractThe eastern Ebro basin is composed of an extensive irrigated plain, surrounded by rainfed slopes and wooden mountain ranges and open to the west to the agricultural western Ebro basin. The sea breeze generated at the coast is able to surmount the Catalan prelitoral range through its lowest heights, reaching the basin by its easternmost part. It is a well‐known feature in the region, called Marinada. A network of Automatic Weather Stations is used here to analyse a period of 19 years (2003–2021). A filtering procedure is developed which selects the events when the Marinada is present, based on detecting clear sky, weak wind conditions and the wind direction from the coast in the afternoon. The analysis of these days show that the Marinada propagates along the basin in the afternoon meanwhile observations of the specific humidity show a sudden increase as the temperature cools down, resulting on a cold and humid advection. It is also found that the timing of the arrival of the Marinada depends on the mesoscale/synoptical circulations already present in the region (westerlies or a thermal low).

Population Exposure Changes to Mean and Extreme Climate Events Over Pakistan and Associated Mechanisms.

The increasing prevalence of warmer trends and climate extremes exacerbate the population's exposure to urban settlements. This work investigated population exposure changes to mean and extreme climate events in different Agro-Ecological Zones (AEZs) of Pakistan and associated mechanisms (1979-2020). Spatiotemporal trends in mean and extreme temperatures revealed significant warming mainly over northern, northeastern, and southern AEZs. In contrast, mean-to-extreme precipitation changes showed non-uniform patterns with a significant increase in the northeast AEZs. Population exposure to mean (extreme) temperature and precipitation events increased two-fold during 2000-2020. The AEZs in urban settlements (i.e., Indus Delta, Northern Irrigated Plain, and Barani/Rainfall) show a maximum exposure to extreme temperatures of about 70-100×106 (person-days) in the reference period (1979-1999), which increases to 140-200×106 person-days in the recent period (2000-2020). In addition, the highest exposure to extreme precipitation days also increases to 40-200×106 person-days during 2000-2020 than 1979-1999 (20-100×106) person-days. Relative changes in exposure are large (60%-90%) for the AEZs across northeast Pakistan, justifying the spatial population patterns over these zones. Overall, the observed changes in exposure are primarily attributed to the climate effect (50%) over most AEZs except Northern Irrigated Plain for R10 and R20 events, where the interaction effect takes the lead. The population exposure rapidly increased over major AEZs of Pakistan, which could be more vulnerable to extreme events due to rapid urbanization and population growth in the near future.

Multilevel life cycle assessment to evaluate prospective agricultural development scenarios in a semi-arid irrigated region of Tunisia

CONTEXTTo design policies for sustainable irrigation planning, public decision-makers need knowledge about the potential environmental impacts of irrigated farming systems. In a previous paper, we proposed to couple Life Cycle Assessment (LCA) and Agrarian System Diagnosis (ASD) to build the Life Cycle Inventory (LCI) of a farming region in a context of data scarcity and farming system diversity. This method was applied to the semi-arid irrigated plain of Kairouan (Tunisia). OBJECTIVESThe aim of the present paper is to demonstrate how this new ASD-based LCA method is used to conduct the impact assessment of this farming region, under current conditions and for two prospective scenarios. METHODSTwo functional units (FU) were used: the area and the gross product generated. Life Cycle Impact Assessment (LCIA) was conducted based on a multilevel process, by converting LCI data collected for each cropping/ livestock system into LCIA outputs, which were then consolidated at the farming system (FS) and at the regional scales. Two scenarios, based on observed trends, were assessed: the “agrarian” scenario (driven by a shift from family to corporate farming) and the “hydrological” scenario (driven by a water table drawdown). RESULTSEnvironmental hotspots were identified at each scale: the most impactful FS was the “mixed family farming” (intermediate access to water), because of its large share of land at the regional scale (45%). In this FS, the most harmful cropping system was input-intensive olive groves intercropped with a melon-pepper/ cereal/ tomato rotation, in which most impacts (35%) were attributable to the input-intensive “melon” crop, and more particularly to “manufacture and transport of fertilizer”, including farmyard manure. Globally, the most harmful processes were water and fertilizer use (fertilizer manufacturing and transportation). This downscaling is very useful to inform public policies on the most harmful productions. The impacts in human, ecosystem and resource endpoints increased by 11%, 2%, 9% and 23%, 27% and 40%, for the agrarian and hydrological scenarios respectively. SIGNIFICANCEThese results show that observed trends in farming practices evolution (more irrigation) should be stopped. Our method has three main strengths: i) inter-farms synergies are accounted for in the LCIA, which is essential to promote circularity; ii) thanks to the innovative and multilevel approach, the origins of environmental hotspots can be investigated and later mitigated by future policies; iii) ASD helps to design sustainable scenarios by identifying current trends and regional thresholds (resources, pollution and workforce) that cannot be overcome.

Distribution of mosquito species in various agro-ecological zones of Punjab

BackgroundThe presence and behavior of mosquitoes in various agro-ecological zones of Punjab are influenced by a combination of seasonal and topographical patterns, cropping schemes, and human settlement. These modifications have a significant impact on the occurrence of diseases. Therefore, determining the distribution of these species could help in halting their spread and disease outbreaks. MethodsUnder these prevailing conditions, surveillance studies were carried out at six zones of Punjab, to know the distribution of mosquitoes. Samples were collected in various seasons (once in winter and rainy seasons, and twice in summer), from all possible habitats, having stagnant water. ResultsOut of twenty-four (24) recorded species, three were included in Anophelinae and Culicinae, eleven from tribe Aedini, eight from Culicini and one each from Ficulbiini and Mansoniini. Sampling was done from 91 m (Ahmed Pur East) elevation to 1759 m (Fort Monroe). High and diversified population was recorded during rainy season. The Anopheline mosquitoes were found in rural as well as urban habitats, including rainfed, wet mountains and irrigated plains whereas Aedine species were confined to northern irrigated plains and mostly recorded from Changa Manga National Forest. Culicine species were more diversified and abundant, in all seasons. However, M. chamberlaini was collected from urban (rainfed lands) and rural (northern irrigated plains) settings. C. crassipes was recorded only from rainfed lands. ConclusionTwenty-four mosquito species from the Anophelinae and Culicinae subfamilies were observed in the current investigation. Anophelinae subfamily contained three species. Eleven species of Culicinae belonged to the tribe Aedini, eight to the Culicini, and one each to the Mansoniini and Ficalbiini.

Pollution source identification of nitrogen and phosphorus in the lower West Main Canal, the Ganfu Plain irrigation district (South China).

The degradation of surface water quality has been a widespread concern around the world. However, irrigation canal water does not attract much attention although it is important to agriculture and population. In this study, a 5-year water quality monitoring of surface water was conducted in the lower West Main Canal of the Ganfu Plain irrigation district to identify the levels and pollution sources of nitrogen and phosphorus.Over 75% of samples had total phosphorus (TP) concentrations of > 0.02mg/L, and all samples had total nitrogen (TN) concentrations of > 0.2mg/L, indicating a risk of eutrophication. The concentrations of NO3--N and NH4+-N averagely occupied 57% and 18% of TN, respectively. PCA analysis showed that phosphorus and nitrogen in canal water were associated with meteorological factors, urban life and surface runoff, agricultural cultivation, livestock-poultry breeding, and water-sediment interaction in the wet season, whereas they were affected by meteorological factors, industrial effluent, urban domestic sewage, and livestock-poultry breeding in the dry season. Absolute principal component score-multiple linear regression (APCS-MLR) model results revealed that (1) agricultural cultivation plus livestock-poultry breeding contributed 43.2% of TP in canal water in the wet season, while livestock-poultry breeding contributed 52.9% in the dry season, and (2) domestic sewage plus surface runoff contributed 29.4% of TN in the wet season, while livestock-poultry breeding contributed 45.9% in the dry season. The unidentified sources had significant contributions of > 20% for almost all variables. So further investigations are required for determining unidentified sources, and anthropogenic pollution control is imperative for canal water quality protection.

Investigating the response of land–atmosphere interactions and feedbacks to spatial representation of irrigation in a coupled modeling framework

Abstract. The transport of water, heat, and momentum from the surface to the atmosphere is dependent, in part, on the characteristics of the land surface. Along with the model physics, parameterization schemes, and parameters employed, land datasets determine the spatial variability in land surface states (i.e., soil moisture and temperature) and fluxes. Despite the importance of these datasets, they are often chosen out of convenience or owing to regional limitations, without due assessment of their impacts on model results. Irrigation is an anthropogenic form of land heterogeneity that has been shown to alter the land surface energy balance, ambient weather, and local circulations. As such, irrigation schemes are becoming more prevalent in weather and climate models, with rapid developments in dataset availability and parameterization scheme complexity. Thus, to address pragmatic issues related to modeling irrigation, this study uses a high-resolution, regional coupled modeling system to investigate the impacts of irrigation dataset selection on land–atmosphere (L–A) coupling using a case study from the Great Plains Irrigation Experiment (GRAINEX) field campaign. The simulations are assessed in the context of irrigated vs. nonirrigated regions, subregions across the irrigation gradient, and sub-grid-scale process representation in coarser-scale models. The results show that L–A coupling is sensitive to the choice of irrigation dataset and resolution and that the irrigation impact on surface fluxes and near-surface meteorology can be dominant, conditioned on the details of the irrigation map (e.g., boundaries and heterogeneity), or minimal. A consistent finding across several analyses was that even a low percentage of irrigation fraction (i.e., 4 %–16 %) can have significant local and downstream atmospheric impacts (e.g., lower planetary boundary layer, PBL, height), suggesting that the representation of boundaries and heterogeneous areas within irrigated regions is particularly important for the modeling of irrigation impacts on the atmosphere in this model. When viewing the simulations presented here as a proxy for “ideal” tiling in an Earth-system-model-scale grid box, the results show that some “tiles” will reach critical nonlinear moisture and PBL thresholds that could be important for clouds and convection, implying that heterogeneity resulting from irrigation should be taken into consideration in new sub-grid L–A exchange parameterizations.

Soil quality assessment and constraint diagnosis of salinized farmland in the Yellow River irrigation area in northwestern China

The widespread occurrence of saline soils in arid and semi-arid agricultural regions necessitates the development of simple and practical methods for assessing soil quality in salinized farmland where soil constraints vary depending on farmland type. Herein six different salinized farmland types were selected from the Hetao Plain irrigation area in the upper reaches of the Yellow River plain (Ningxia, China) to assess the soil quality and diagnose potential soil constraints. An integrated quality index (IQI) was calculated using four combinations of nonlinear scoring (SNL) and linear scoring (SL) functions with the total data set (TDS) and minimum data set (MDS) methods. Sixteen indicators of soil physical and chemical properties were included in the TDS, seven of which were selected as MDS indicators, including sand content, total nitrogen, electrical conductivity, and cation exchange capacity. IQI values derived from the MDS method mirrored the results from the TDS method. The soil quality assessed by the four different methods showed consistent spatial patterns across the six farmland types, despite differences in details. In most cases, the highest IQI values were obtained based on TDS-SL, whereas MDS-SL yielded the lowest IQI values. Compared with the results of MDS-SL, IQI values derived from MDS-SNL were closer to those from TDS-SNL. When assessed using the MDS-SNL method, medium- and low-quality soils accounted for >98.0% of Calcic Solonchaks and Takyr Solonetzs. Fluvic Solonchaks had the largest proportion of medium-quality soils (86.5%). The major soil constraint was soil texture for Calcic Solonchaks and Haplic Solonchaks, nutrient limitation for Takyr Solonetzs, saline stress for Haplic Solonetzs, and co-existing soil texture and nutrient limitation for Fluvic Solonchaks and Stagnic Solonchaks. This study unravels multiple soil constraints across various salinized farmland types with medium-to-low soil quality in a major commercial grain base in northwestern China. MDS-SNL-based IQI can be useful for large-scale soil quality assessment in salinized farmland in the Yellow River irrigation area.

Socioeconomic Determinants and Perceptions of Smallholder Farmers towards Agroforestry Adoption in Northern Irrigated Plain, Pakistan

Amid the epoch of global overpopulation, the agroforestry system can intervene as a novel practice that can safeguard agricultural sustainability, provide a means of livelihood, yield ecological benefits, and contribute to household food security. However, the adoption of sustained agroforestry practices requires an understanding of both farmers’ personal characteristics and perceived statuses, constituting a difficult task to anticipate, analyze, and visualize. To this end, it is crucial to understand and identify the most significant factors driving the adoption of agroforestry. This research attempts to examine the determinants and psychological drivers of smallholder farmers’ intention to plant trees on farmland and the factors that may discourage them from doing so. The conceptual framework of the study was developed based on the theory of planned behavior. We draw on survey data from 400 smallholder farmers in a northern irrigated plain of Pakistan. A binary logistic regression model was employed to explore how socio-psychological drivers influence farmers’ decision to adopt agroforestry practices. The study results reveal that 60.5% of the respondents prefer to adopt agroforestry practices. The results from a logit estimation showed that socio-economic variables such as family size, land ownership, subsidies, livestock rearing, sources of energy, and total income had a significant positive influence on the planting of trees on farmland, while age had a negative influence. Moreover, runoff control and the control of heat significantly affect the perceptions of farmers regarding the adoption of agroforestry. The findings suggest that implementing policies that enhance the delivery of robust agricultural extension services and training programs for farmers could disseminate the agroforestry system countrywide, which might offer substantial benefits for farmers in the long term while maintaining environmental integrity.

Effects of Different Soil Moisture-Holding Strategies on Growth Characteristics, Yield and Quality of Winter-Seeded Spring Wheat

Drought during the overwintering period threatens the emergence rate and restricts the yield under the “winter-seeded spring wheat” cultivated model in the Hetao Plain Irrigation District in Inner Mongolia. To address this issue, from 2017 to 2019, six treatments were set up in the field to study the emergence rate, growth attributes, grain quality, yield and its percentage of winter-seeded spring wheat. These treatments were the (1) application of water-retaining agents under winter sowing (WRA), (2) soil amendments under winter sowing (SA) and wheat seed presoaking with amino acid water-soluble fertilizer under winter sowing (SP), (3) straw mulching under winter sowing (SM), (4) film-mulching hole sowing under winter sowing (FMHS), (5) blank control under winter sowing (CKW) and (6) conventional blank control under spring sowing (CKS). The results showed that the emergence rate of winter-seeded treatment was lower than CKS treatment, the emergence of WRA, SA, SM, and FMHS treatment increased by 5.4%, 2.3%, 6.5% and 10.8% compared with CKW treatment, respectively. The winter-seeded treatment is earlier than CKS treatment in the growth process, in which FMHS treatment is between 12 d and 16 d earlier in the emergence period, between 13 d and 15 d earlier in the maturation period, between 8 d and 12 d earlier than the CKW treatment in the emergence period, and between 8 d and 10 d earlier in the maturity period. Compared with CKW treatment, WRA, SA, SM, FMHS and CKS treatments increased yield by 13.49%, 11.42%, 14.75%, 21.61% and 28.15%, respectively. FMHS treatment significantly reduced the total water consumption and significantly improved water use efficiency. The protein content, wet gluten content, sedimentation value, dough ductility and maximum resistance in CKS treatment were significantly lower than other winter sowing treatments. The protein percentage and wet gluten percentage in FMHS treatment were the highest, and the difference with CKW treatment was significant. In summary, film-mulching hole sowing in winter improves soil water and the emergence rate, significantly accelerates the growth process of wheat, increases yield and promotes grain quality.

A GIS-based method for modeling methane emissions from paddy fields by fusing multiple sources of data

Quantification of regional methane (CH4) gas emission in the paddy fields is critical under climate warming. Mechanism models generally require numerous parameters while empirical models are too coarse. Based on the mechanism and structure of the widely used model CH4MOD, a GIS-based Regional CH4 Emission Calculation (GRMC) method was put forward by introducing multiple sources of remote sensing images, including MOD09A1, MOD11A2, MOD15A2H as well as local water management standards. The stress of soil moisture condition (f(water)) on CH4 emissions was quantified by calculating the redox potential (Eh) from days after flooding or falling dry. The f(water)-t curve was calculated under different exogenous organic matter addition. Combining the f(water)-t curve with local water management standards, the seasonal variation of f(water) was obtained. It was proven that f(water) was effective in reflecting the regulation role of soil moisture condition. The GRMC was tested at four Eddy Covariance (EC) sites: Nanchang (NC) in China, Twitchell (TWT) in the USA, Castellaro (CAS) in Italy and Cheorwon (CRK) in Korea and has been proven to well track the seasonal dynamics of CH4 emissions with R2 ranges of 0.738–0.848, RMSE ranges of 31.94–149.22 mg C/m2d and MBE ranges of −66.42- -14.79 mg C/m2d. The parameters obtained in Nanchang (NC) site in China were then applied to the Ganfu Plain Irrigation System (GFPIS), a typical rice planting area of China, to analyse the spatial-temporal variations of CH4 emissions. The total CH4 emissions of late rice in the GFPIS from 2001 to 2013 was in the range of 14.47–20.48 (103 t CH4-C). Ts caused spatial variation of CH4 production capacity, resulting in the spatial variability of CH4 emissions. Overall, the GRMC is effective in obtaining CH4 emissions from rice fields on a regional scale.

Land–Atmosphere Interactions during GRAINEX: Planetary Boundary Layer Evolution in the Presence of Irrigation

Abstract This paper analyzed observations from the Great Plains Irrigation Experiment (GRAINEX) to better understand land–atmosphere (L–A) interactions and PBL evolution. This study is focused on a day when the largest forcing on the boundary layer originated from the land surface/land use. To examine these impacts, we also applied the Weather Research and Forecasting (WRF) Model. Results from the observations show that compared to nonirrigated areas, air temperature, wind speed, and PBL height (PBLH) were lower while dewpoint temperature and latent heat flux were higher over irrigated areas. Findings suggest that entrainment layer drying and differences in energy partitioning over irrigated and nonirrigated areas played an important role in PBL evolution. In the final hours of the day, the PBL collapsed faster over nonirrigated areas compared to irrigated. The WRF Model simulations agree with these observations. They also show that the extent of irrigation [expressed as irrigation fraction (IF)] in an area impacts L–A response. Under ∼60% IF, the latent heat flux and mixing ratio reach their highest value while temperature and PBLH are at their lowest, and sensible heat flux is near its lowest value. Results are reversed for ∼2% IF. It is concluded that irrigation notably impacts L–A interactions and PBL evolution.

Impacts of a shallow saline water table on maize evapotranspiration and groundwater contribution using static water table lysimeters and the dual Kc water balance model SIMDualKc

The occurrence of shallow saline water tables in arid zones provides for groundwater-fed natural vegetation and for a substantial amount of irrigated crops’ water needs. This is the case of the Hetao plain, upper Yellow River Basin, Inner Mongolia, China, where one of the major irrigation systems of China and the World is installed. As reviewed, numerous irrigation and water management studies have been developed in Hetao and the upstream irrigated plain of Yinchuan, Ningxia. These studies have demonstrated the need for controlling salts through the autumn irrigation and the appropriate irrigation methods and scheduling. Moreover, studies evidenced the need for adopting irrigation schedules that consider groundwater contribution during the crop cycle but most of these studies were empirical, resulting difficult to transfer results. When models adopted were mechanistic, they are difficult to use for irrigation scheduling purposes comparatively with soil water balance (SWB) models. Thus, the current study used two sets of five static water table lysimeters cropped with maize and having water table depths (WTD) fixed between 0.85 and 2.25 m. It was therefore possible to observe the daily capillary rise fluxes from the water table, the dynamics of water and salts and to calibrate the SWB model SIMDualKc. Results show that the average electrical conductivity of the saturated extract of the soil ranged from 3.10 to 4.69 dS m−1 with the higher values observed when WTD was smaller, while the electrical conductivity of irrigation water ranged 1.73–1.87 dS m−1. Results also show that shallower WTD required less irrigation water but caused higher salinity impacts on crop growth and yields. Thus, the best WTD were around 1.75–2.00 m when basin irrigation was adopted in 2017 and 2018. In these crop seasons, the simulated groundwater contribution to actual crop evapotranspiration (ETc act) was up to 37% in the lysimeters having a shallow WTD (1.25 m), while in the lysimeters with deeper WTD (2.00–2.25 m) it was about 11% of the ETc act. Contrastingly, in 2019, when maize was not irrigated, the average groundwater contribution represented 73% and 49% of ETc act in the lysimeters with shallow and deep WTD, respectively. Results were obtained when a large leaching autumn irrigation (200 mm) was performed. Those experiments showed that, solutions for using basin flooding irrigation are ready but still require that irrigation scheduling is adjusted to provide for appropriate use of the saline groundwater contribution, which may be performed with the model SIMDualKc, as demonstrated by the high goodness-of-fit indicators used to evaluate the referred simulations.

Delineating the origins and processes of groundwater salinization and quality degradation in a coastal irrigated plain, Korba (Northeastern Tunisia)

From 2006 to 2020, groundwater investigations were conducted in the Korba coastal aquifer in northern Tunisia along two flow paths (transects S1 and S2), perpendicular to the shoreline. Groundwater sampling, hydrodynamic monitoring, and electrical tomography imaging were performed in situ. Geochemical analysis (Ionic ratios, ionic deltas, conventional diagrams, and stable isotopes) and modelling using PHREEQC, and multivariate statistical analysis were applied. The objective was to identify the potential origin of groundwater salinization (i.e., high TDS and NO3) and to study associated processes.The groundwater flow inversion was corroborated by the piezometric survey in transect S1, where a piezometric depression of 5 m was detected at 4000 m from the seashore. Seawater intrusion and agricultural contamination, mainly through N-fertilizers, both contribute to groundwater mineralization and consequently salinization, according to PCA analysis. The impacted geochemical area of seawater intrusion was estimated to be 4000 and 1500 m, respectively, along transect S1 and transect S2. Inversely, agricultural contamination acts in internal areas beginning at 2000 m and 1500 m from the shoreline for S1 and S2, respectively. Results of different scenarios of inverse geochemical modelling along flow paths indicated that mixing, ion exchange, dissolution of gypsum, and precipitation of dolomite and calcite are the main processes controlling the groundwater composition in the coastal study area.