Subsurface Drainage Research Articles

Assessing Endokarst Potential in the Northern Sector of Santo António Plateau (Estremadura Limestone Massif, Central Portugal)

Karst is a peculiar natural landscape arising from high rock solubility and well-developed underground solutional channel porosity. It is unique for its surface relief (exokarst) and subsurface drainage, including cave systems (endokarst). In Portugal, karst areas mainly consist of marginal or low-density territories with great fragility and vulnerability and great geo-environmental richness that merits better policies and practices regarding their geo-conservation. Endokarst potential assessments can provide decision-makers and local authorities insight into present and future territorial management and planning. In this context, the main objective of this study was to produce a cartographic model to identify areas with a greater probability of containing karstic caves—i.e., a greater endokarst potential—in the northern sector of the Santo António Plateau (Estremadura Limestone Massif, Central Portugal). Geological, topographic, hydrogeological, and land cover data were collected, processed, and integrated into a spatial database using a Geographic Information System. The locations of known cave entrances in the study area were also identified from local public institutions and speleological team records. Subsequently, four conditioning factors were extracted from the data: lithostratigraphic units, fracture density, relief energy, and land cover. Using a multi-criteria decision-making analysis, each previously chosen conditioning factor and its respective classes were weighted using an analytic hierarchy process. The locations of known cave entrances served to evaluate the cartographic model built, with results showing an agreement of 81.9%. This prototype of the endokarst potential map for the study area may be used for strategic and operational environmental planning (at least on a local scale) to assist decision-makers, competent authorities, and local speleological teams. Its application may promote a more accurate and thoughtful definition of areas to be investigated, substantially reducing the time and costs associated with field prospecting.

Stephen Foster and Radu Gogu. Groundwater assessment and management for sustainable water-supply and coordinated subsurface drainage: a guidebook for water utilities and municipal authorities

Stephen Foster and Radu Gogu. Groundwater assessment and management for sustainable water-supply and coordinated subsurface drainage: a guidebook for water utilities and municipal authorities

Estimating natural soil drainage classes in the Wisconsin till plain of the Midwestern U.S.A. based on lidar derived terrain indices: Evaluating prediction accuracy of multinomial logistic regression and machine learning algorithms

Accurate spatial prediction of natural soil drainage condition is not only important for agriculture and hydrological modeling but also for installing subsurface drainage and onsite waste disposal systems. For this research, 154 sites were selected based on a stratified random sampling method. For each site, drainage class was identified based on visual examination of soil cores. A digital elevation model developed from lidar data was used to derive seven terrain indices. Terrain indices were used to predict drainage class using four prediction models: multinomial logistic regression and three machine learning algorithms (random forest, C5.0, and artificial neural network). Based on 30% random hold-back validation data, all digital soil mapping (DSM) models provided similar results. The artificial neural network provided relatively higher overall accuracy of 70%, a kappa coefficient of 0.59, and a Brier score of 0.34. The rest of the DSM models as well as SSURGO provided an accuracy that ranged between 64 and 66%, a kappa coefficient that ranged between 0.52 and 0.54, and a Brier score that ranged between 0.41 and 0.46.

Efficient desalination method using a subsurface drainage pipe with rice husk in paddy fields

The 2011 tsunami from the Great East Japan Earthquake caused severe soil salinization in agricultural lands. Soil salt removal using a subsurface drainage pipe with rice husk has been widely used in many paddy fields. However, desalination was frequently decided based on the expertise of construction contractors in Japan resulting in inefficient desalination methods that led to a significant wastage of freshwater resources and a long duration for agricultural restoration. Previous studies have either simulated conventional subsurface drainage without considering the rice husk zone or focused only on rice husk subsurface drainage systems excluding pipes. However, no quantitative research on a subsurface drainage pipe with rice husk has been conducted using numerical simulations. Accordingly, this study proposes highly efficient desalination methods for reducing freshwater wastage using an indoor experiment and numerical simulation. The indoor experiment of the subsurface drainage pipe with rice husk was set up in a soil tank of 900 × 200 × 900 mm (length × width × height), with reproduced salinization using NaCl solution inundation and soil desalination using freshwater. Thereafter, calibration and validation using HYDRUS-2D confirmed the model's accuracy in reproducing the movement of water and salt in the soil profile. The effects at a ponding water depth of 50–300 mm under various conditions on desalination efficiency and leaching water quantity were simulated. The results suggested that as the same desalination effect is achieved, low ponding water depths with multiple desalting cycles will reduce the quantity of leaching water. Moreover, under low ponding water depth conditions, prolonging the flooding duration will cause a decrease in the desalination effect. In addition, for the same quantity of leaching water, increasing the pipe burial depth is more beneficial to desalination than expanding the rice husk zone width. This study provides theoretical guidance for water conservation and high-efficiency desalination using the subsurface drainage pipe with rice husk for post-disaster early restoration of paddy fields.

Impacts of biostimulation and bioaugmentation on woodchip bioreactor microbiomes.

Nitrate pollution is a serious problem in agricultural areas in the U.S. Midwest and other parts of the world. Woodchip bioreactor is a promising technology that uses microbial denitrification to remove nitrate from agricultural subsurface drainage, although the reactor's nitrate removal performance is limited under cold conditions. This study showed that the inoculation of cold-adapted denitrifiers (i.e., bioaugmentation) and the addition of labile carbon (i.e., biostimulation) can influence the microbial populations and enhance the reactor's performance under cold conditions. This finding will help establish a strategy to mitigate nitrate pollution.

Predicting the effect of weir management on the discharge of a controlled drainage system in a changing climate

Subsurface drainage in humid areas prevents field waterlogging but also transports nutrients to freshwater systems. Controlled drainage (CD) reduces drainage discharge and nutrient transport from fields. Some regions are expected to experience increased precipitation in the future, requiring CD to be evaluated under a changing climate. The objective of this study was to compare the performance of CD under two weir managements for a future period (2030–2059) and historical period (1992-2021) in southeast Michigan, USA. Climate projections were obtained for the shared socioeconomic pathway 245 emission scenario. Aggressive management involved maintaining the weir height at 40 cm during the growing season and 15 cm during the non-growing season, with a longer period of managed flow compared to common management, which maintained the weir height at 50 cm during the growing season and 30 cm during the non-growing season. It was predicted that the 30-year average annual precipitation would not change significantly in the future. The 30-year average mean monthly temperature would increase by 3.0°C in the future compared to the historical period. We performed simulations using the calibrated Root Zone Water Quality Model 2 (RZWQM2). The average drainage discharge in the future indicated a 20% increase in the 30-year average drainage discharge for a field with free drainage. The CD with common and aggressive managements reduced drainage discharge by 59% and 67% for the historical period, whereas the performance of CD was even better for the future period (63% and 72%, respectively). The improved future performance of CD can be attributed to a shift in precipitation patterns, with reduced precipitation during the growing season and increased precipitation during the non-growing season. As a result, the more aggressive weir management during this period created additional opportunities for reducing drainage discharge. In conclusion, aggressive management resulted in a slightly better flow-reducing performance than common management while indicating that both methods would effectively reduce drainage discharge in the likely future scenario.

Challenges in modernizing the subsurface drainage systems in Egypt

Challenges in modernizing the subsurface drainage systems in Egypt

Contribution of water erosion to organic carbon and total nitrogen loads in agricultural discharge from boreal mineral soils

While organic carbon (OC) in agricultural mineral soils is widely studied in terms of soil carbon sequestration and gaseous emissions, discharge-induced OC loss from soil is still poorly understood and estimations of boreal soil OC loads within water erosion are lacking. Loss of organic matter from arable soils is a concern for surface water quality, climate change and soil productivity. The main aim of this study was to quantify the role of water erosion in total OC and nitrogen (N) loads exported in agricultural discharge from boreal mineral soils under various cultivation practices. Surface water and subsurface drainage were collected near-continually over 2 years in two clayey and one sandy soil in Finland. Eroded sediment was mechanically separated by centrifugation from all discharge samples to detect sediment OC% and N% by dry-combustion method. Dissolved OC and N concentrations in selected discharge samples were measured with high-temperature catalytic oxidation of unfiltered supernatant. A multiple linear regression model was used to study the significant factors affecting dissolved, sediment and total OC loads. In the clayey soils, the sediment OC (2–24 kg ha−1 y−1) and N (0.2–1.1 kg ha−1 y−1) export accounted for up to 35 % and 20 % of the annual discharge-induced total loads of OC (19–85 kg ha−1) and N (2–8 kg ha−1), respectively. In the sandy soil, erosion was negligible and dissolved loads of 17–35 kg OC ha−1 y−1and 4–7 kg N ha−1 y−1 were detected. Subsurface drainage exported most of the sediment-associated OC and N loads from clayey soils. For the total OC loads, the distribution varied between the discharge routes, while the total N loads were mostly exported in subsurface drainage in both soil types. Sediment OC and N exports were related to soil plowing and discharge intensity, while dissolved OC loss was promoted by high surface soil OC%. Our results also indicated that a single cultivation practice may affect sediment and dissolved loads in opposite ways. These findings can be used to complement carbon budget estimations for mineral agricultural soils, and to assess soil management effects on terrestrial organic matter loading to boreal surface waters.

Effects of Subsurface Pipe Drainage Spacing on Soil Salinity Movement in Jiangsu Coastal Reclamation Area

The agricultural development of reclaimed coastal areas in Jiangsu Province is significantly hindered by high soil salinity and an inadequate irrigation and drainage infrastructure. Optimizing the layout of subsurface drainage systems has been identified as an effective means of reducing soil salinity, with the proper designation of engineering parameters being crucial. This study applied 12 treatments (T1–T12) consisting of four different spacings of subsurface drainage pipes (6 m, 11 m, 15 m, and no subsurface drainage pipes) and three observation wells at varying distances from the drainage outlet (5 m, 25 m, and 45 m). Results showed that all three subsurface pipe spacing treatments significantly reduced soil salinity compared to natural drainage, with a smaller subsurface pipe spacing treatment leading to better salt-reducing effects. The farther the distance from the measuring point to the drain, the higher the salinity. As the burial depth of the outlet decreased and spacing between the subsurface drainage pipes decreased, the salinization rate of the 0–60 cm soil layer was higher, while the salt accumulation in the 60–80 cm soil layer was more severe. Therefore, a subsurface drainage pipe spacing of 6 m and an outlet burial depth of 40 cm are recommended as more suitable choices to effectively control salt concentration in the soil. The research aimed to provide scientific reference data and technical support for the optimized design of subsurface drainage engineering parameters while promoting efficient desalination of saline-alkali areas worldwide.

Estimating US farmers' speed of climate change adaptation: the case of subsurface tile drainage

PurposeClimate change is expected to cause larger and more frequent precipitation events in key agricultural regions of the United States, damaging crops and soils. Subsurface tile drainage is an important technology for mitigating the risks of a wetter climate in crop production. In this study, the authors examine how quickly farmers adapt to increased precipitation by investing in drainage technology.Design/methodology/approachUsing farm-level data from the 2018 Agricultural Resource Management Survey (ARMS) of soybean producers, the authors construct a drainage adoption timeline based on when the operator began farming their land and when tile drainage was installed, if at all. The authors examine both the initial investment decision and the speed with which drainage is installed by adopters. A Heckman-style Poisson regression is used to model the count nature of adoption speed (measured in years taken to install tile drainage) and to correct for potential sample-selection bias.FindingsThe authors find that local precipitation is not a significant determinant of the drainage investment decision but may be highly influential in the timing of adoption among drainage users. Farms exposed to crop-damaging levels of precipitation install tile drainage faster than those with low to moderate levels of rainfall. Estimates of farm adaptation speeds are heterogeneous across farm and operator characteristics, most notably land tenure status.Originality/valueUnderstanding how US farmers adapt to extreme weather through technology adoption is key to predicting the long-term impacts of climate change on America's food system. This study extends the existing climate adaptation literature by focusing on the speed of adoption of an important and increasingly common climate-mitigating technology – subsurface tile drainage.

Simulating the impact of subsurface pipe drainage systems on crop water productivity at a regional scale in the upper Yellow River Basin

AbstractSubsurface pipe drainage (SPD) could provide a suitable environment for crop production in arid and semi‐arid agricultural areas; however, less attention has been given to the design layout of SPD on the regional scale in Hetao Irrigation District (HID). In this study, the appropriate layout of the final subsurface pipe was determined using the distributed SWAP‐WOFOST (Soil–Water–Atmosphere–Plant and WOrld FOod STudies) model in HID. Subsequently, the impact of the proper SPD on crop yield and water productivity (WP) were evaluated. Finally, the crop zoning was adjusted to further enhance crop WP, and the corresponding newly added cultivated land area was preliminarily estimated based on the suggested SPD. The results indicated that after zoning in the suggested SPD, the annual average yields of spring wheat, spring corn and sunflower increased by 19%, 7% and 11%, respectively, and WP improved by 13%, 5% and 10%, respectively, compared to the traditional layout. The newly added cultivated land area was estimated to be approximately 3489 ha through the replacement of traditional end ditches with subsurface pipes in HID. Therefore, the suggested subsurface pipe designs and cropping pattern adjustment improved crop growth and led to an increase in the cultivated land area in HID.

Sub-surface drainage: A win-win technology for achieving carbon neutrality and land amelioration in salt-affected Vertisols of India

This study aims to investigate the long-term impact of subsurface drainage (SSD) in restoring the soil quality and sugarcane productivity of waterlogged saline Vertisols. A combination of methodologies including analytical techniques, collection of soil and water samples and field survey with farmers was applied to collect the data, and drawing the inferences. The results indicated that successful long-term operation of SSD improved soil quality. A significant reduction in soil salinity (ECe) (Kavathesar site: 13.27 to 2.61, Shedshal site: 33.21 to 13.72 dS m−1) was observed. An appreciable improvement in soil bio-physico-chemical properties including organic carbon (OC%) (Kavathesar site: 0.48 to 0.63, Shedshal site: 0.22 to 0.44%) and dehydrogenase activity (DHA) (Kavathesar site:10.22 to 13.87, Shedshal site: 4.01 to 17.16 μg g−1 24 h−1), alkaline phosphatase (ALPA) (Kavathesar site:74.00 to 93.00, Shedshal site: 34.00 to 61.00 μg P-NP g−1 h−1), bulk density (BD) (Kavathesar site: 1.17 to 1.13, Shedshal site: 1.19 to 1.07 Mg m−3), saturated hydraulic conductivity (SHC) (Kavathesar site: 2.38 to 3.20, Shedshal site: 1.70 to 2.95 cm day−1) was found on surface (0–30 cm) layer comparing to their control sites (without SSD). The principal component analysis (PCA) showed that % OC, ECe, BD, and available K content were the most contributing factor for soil quality index (SQI). The improved soil quality has resulted in increasing the sugarcane yield by 226.8 and 585.5% at Kavathesar and Shedshal sites, respectively. The farmers' perception revealed that SSD technology (adopted on community scale) could play substantial role in improving the soil condition, and thereby enhancement in the yield of sugarcane crop. Thus, SSD technology was observed to have great potential in improving soil quality, crop (sugarcane) productivity, farmers' income and ensuring land degradation neutrality goal under saline Vertisols of India. Therefore, the large-scale adoption of SSD, managed with regional planning and strong cooperation among the stakeholders, may fulfil the promise of Sustainable Development Goals (SDGs) including Life on Land, No Poverty and Zero Hunger in degraded black saline soils.

Electrolysis characterization of saline wastewater discharged from a subsurface pipe in saline-alkali land

We improved the design of an ion membrane electrolysis device to assess its use for electrolytic desalination and hydrogen production utilizing wastewater discharged from a subsurface drainage pipe in saline-alkali land. The device can reduce the waste of water resources and agricultural non-point source pollution. The electrolysis performance is low due to the low concentration of salts and complex ionic species in the drainage water from subsurface pipes of farmland. A one-factor quantitative experimental study was conducted to assess the influence of the electrolysis parameters on the electrolytic characteristics. Multifactor synergistic optimization of the parameters was performed. The results indicate different degrees of linear correlations between the hydrogen and chlorine gas production rates and the current density (CD) for different process parameters. Different factors have different degrees of influence on the electrolysis characteristics, and factor interactions occur. The optimization model describing the effects of multiple factors on the final current density (FCD), pH value after reaction (ARP), and energy consumption rate (ECR) is reliable and stable. The optimized operating parameters included a brine concentration (BC) of 3.6 mol·L−1, before reaction pH (BRP) value of 9, working voltage (WV) of 12.2 V, and electrode immersion depth (EID) of 22.5 cm. Under these conditions, the FCD is 183.03 mA·cm−2, the ARP is 13.99, and the ECR is 24,586.50 kW·h/kg. The proposed method substantially improves the electrolysis performance. The results provide theoretical and technical support for utilizing saline wastewater discharged from saline-alkaline land.

Application of Simple Crested Weirs to Control Outflows from Tiles Drainage

Triangular sharp-crested weirs are commonly used to measure low-flow measurements in open channels. The flow over such a V-notch is proportional to the height of water above the weir on the upstream side. Therefore, it is relatively easy to calculate the flow from standard equations by using only recordings of water levels. Thus, these types of weirs can provide inexpensive measurements of flow volumes and resulting nutrient loads from subsurface drainage systems and associated conservation practices. The objective of this study was to develop appropriate weir equations for a 22.5° V-notch weir developed for a new tubular water level control structure in a controlled drainage system (CD). Analyses using this weir, with three typical slope angles of 30°, 45°, and 60°, were also conducted. There were no significant differences in the fitted parameters across the three analyzed slope angles. The coefficient of determination (R2) values were 0.9955, 0.9981, and 0.9980, respectively. However, the best-fitted equation for a 22.5° V-notch weir was for a slope angle of 45°. The flow equation was Q = 0.2235H2.4182, with Q in liters per minute and H in centimeters. This equation can be used for measuring flow through tubular-controlled drainage structures.

A spatially distributed hydrodynamic model framework for urban flood hydrological and hydraulic processes involving drainage flow quantification

Two-dimensional hydrodynamic models are increasingly used to predict overland surface water flooding in urban catchments. The complexity of urban surfaces and subsurface drainage systems poses great challenges to modelling urban rainfall-runoff and flood hydraulics. This work develops a spatially distributed hydrodynamic model framework incorporating both hydrological and hydraulic processes of surface and subsurface drainage processes during urban flooding. The model is built upon 2D full shallow water equations solved by a Godunov-type finite volume method with robust treatments of the bed source term. To properly involve drainage flow effects, we present three methods to quantify the drainage flow discharge and its delay time which affect both urban hydrology and surface inundation. Besides, a simple OpenMPI-based parallel algorithm is applied to accelerate the model and ensure computational efficiency when applied to real-world events. The model framework is justified through the validations with five benchmark cases. Benchmark results indicate that the well-balanced treatment of bed source term ensures the model applicability in irregular urban surfaces, the model can predict both urban surface inundation and flood hydrograph, and the proposed drainage flow treatments can well reproduce drainage flow hydrograph. The model framework is successfully applied to simulate rainstorm-induced flood events in a rural–urban catchment, the upper Shenzhen River catchment. Results further demonstrate the robust capability of the model in the quantification of flow exchange between surface and subsurface systems to some extent even in the absence of drainage information. Our framework provides a practical solution for urban flood simulation even when pipe data are scarce.

Is Controlled Drainage of Agricultural Land a Common Used Practice?—A Bibliographic Analysis

Controlled drainage (CD) is one of the basic techniques used to manage groundwater levels. Farmers can optimize water levels for crop growth at different stages of the growing season. Proper drainage water management can reduce the risk of soil erosion and surface water pollution. By controlling drainage, sediment and nutrient runoff can be minimized, leading to improved water quality in nearby streams and rivers. A mixed methods approach was used, which was based on the bibliometric analysis and content analysis of 462 articles using the bibliometrix R package and VOSviewer software. The article aimed to analyze the Author Keywords and KeyWords Plus to indicate the resulting clusters of complex interdependence that emerge from the main research areas. Continuous research continues to improve drainage techniques and systems to optimize agricultural water use. The results indicated the importance of researching the feasibility of CD for agriculture. The innovation of this study is that it points out the relevance of taking up the possibility of changing the use of unilateral subsurface drainage systems with another method of controlling drainage outflows as a current global challenge, contributing to filling this gap in the literature.

Leaching of nitrogen, phosphorus and other solutes from a controlled drainage cultivated peatland in Ruukki, Finland

Cultivated peatlands are important for grass production in Northern Europe, but the potential impact of nutrients leaching to surface waters is a major concern. Due to a lack of data on nitrogen (N), phosphorus (P) and organic carbon leaching, a monitoring programme was established at Ruukki (Siikajoki, Finland), an agricultural, subsurface drained peat site with a peat thickness of 20–80 cm. Concentrations and loading of N, P, and total organic carbon (TOC) were monitored, along with other water quality parameters for the field discharge, in 2018–2021. We observed N leaching from subsurface discharge to be 25 kg N ha−1 year−1 (range 11–40 kg N ha−1 year−1, 74 % as nitrate NO3-N). The least N leaching was recorded from plots of thinner peat topsoil and those with grass cover, while the majority of N leaching originated from thicker peat plots (bare or under barley) in spring. Leaching of N strongly decreased during periods of thick grass cover. Significant N leaching also occurred during the mild winter of 2019–2020, characterized by alternating freeze and thaw periods. Annual P loading from subsurface drainage was 0.30 kg P ha−1 (0.20–0.43 kg P ha−1), low compared to that of average cultivated soils in Finland. It was estimated that 13 % of the total N leaching and 50 % of the total P leaching occurred in surface runoff. Leaching of TOC was significant at 87 kg ha−1 year−1 (31–137 kg ha−1 year−1). Leaching of dissolved P and TOC increased with peat thickness. Abundant loading of sulfur and acidity indicates the oxidation of sulfidic material in the subsoil. Leaching concentrations correlated with discharge quantity, suggesting that mobilization processes during the dry periods resulted in leaching during high discharge periods. The results show the importance of avoiding bare peat soil for NO3-N leaching reduction, even during wintertime in cultivated peatlands.

Subsurface drainage pipe detection using an ensemble learning approach and aerial images

Subsurface drainage pipe detection using an ensemble learning approach and aerial images

Design of subsurface drainage network with minimum overall cost using Lagrange multiplier optimization

AbstractSubsurface drainage is effective for not only controlling groundwater levels in agricultural lands but also alleviating soil salinity localized at the root zone, especially for arid and semi‐arid agro‐ecosystems. In this research, an optimization model that minimizes the overall costs of subsurface drainage systems subjected to design constraints was formulated. The Lagrange multiplier method for optimization was utilized to derive a general differential equation for obtaining the most economical design of the subsurface drainage system. Design charts for the minimum cost of the subsurface drainage network ($ ha−1) for lateral diameters (dL) of 2.5, 5, 7.5, 10 and 12.5 cm; hydraulic conductivities (K) of 0.5, 1, 2, 3 and 4 m day−1; different lateral lengths (LL) of 100, 150, 200, 250, and 300 m; a constant collector length (LC) of 1000 m (assuming laterals join the collector from both sides); drainage recharge (q) values of 1, 2, 3, 4 and 5 mm day−1; and excavation depths of 1.5 and 2.0 m were developed. The minimum computed subsurface drainage network (SSDN) costs observed at a lateral length (LL) of 300 m were 205, 246, 288, 331 and 374 ($ ha−1) for lateral diameters of 2.5, 5, 7.5, 10 and 12.5 cm, respectively, corresponding to lateral spacing of 175, 176, 177, 178 and 179 m. The suggested charts for the optimum design of a subsurface drainage system have lower overall costs than using conventional design approaches for pipelines and tube wells. The results will support solutions for designers to implement subsurface drainage systems with less and more affordable expenses in the old lands of the Nile delta of Egypt and other regions with similar agrosystems. Quality control during construction is very necessary for guaranteeing the effective and sustainable performance of subsurface drainage systems for many years.

N2O Emissions from Saline Soils in Response to Organic–Inorganic Fertilizer Application under Subsurface Drainage

Organic fertilizer applications and subsurface drainage are two important measures for improving coastal saline soil; however, nitrous oxide (N2O) emissions from saline soil under a combination of these two measures are seldom evaluated. In this study, saline soil cultivated with sunflowers (Helianthus annuus L.) was employed as an experimental system. Prior to the experiment, the saline soils were buried with three different spacings (10 m (S1), 15 m (S2), and 20 m (S3)) of subsurface drainage pipes. The nitrogen nutrients that are needed by sunflowers came from two different nitrogen sources (organic and inorganic fertilizer), including six application schemes of either 100% organic fertilizer (100%OF), 75% organic fertilizer combined with 25% inorganic fertilizer (75%OF), 50% organic fertilizer (50%OF), 25% organic fertilizer (25%OF), 0% organic fertilizer (0%OF), and no fertilizer (CK). The results show that the cumulative N2O emissions from the treatments under S1, S2, and S3 throughout the entire growth period were 8.9–15.8, 9.5–17.5, and 10.1–17.6 kg ha−1, respectively. A smaller spacing between adjacent drainage pipes or a higher replacement proportion of organic fertilizer reduced the accumulative N2O emissions. The increased replacement of organic fertilizer decreased the soil salinity, whereas it increased the C/N ratio and total carbon content. The fertilization treatments significantly increased the nitrogen uptake of sunflower plants, with increase ranges of 18.1–47.2%, 8.6–40.5%, and 8.8–34.5% under S1, S2, and S3, respectively, compared with CK. The highest yield of sunflowers was achieved under S2 combined with 25%OF, reaching 3.82 t ha−1. Correlation analysis showed that the N2O emission flux was positively correlated with the soil salinity, crop yield, and crop nitrogen uptake, whereas it was negatively correlated with the total carbon, C/N ratio, and organic carbon content. We concluded that using 25% organic fertilizer instead of inorganic fertilizer was beneficial for reducing N2O emissions while maintaining the crop yield under subsurface drainage.