Effects Of Drainage Water Management Research Articles

Effects of Drainage Water Management in a Corn–Soy Rotation on Soil N2O and CH4 Fluxes

Drainage water management (DWM), also known as controlled drainage, is a best management practice (BMP) deployed on drainage ditches with demonstrated success at reducing dissolved nitrogen export from agricultural fields. By slowing discharge from agricultural ditches, subsequent anaerobic soil conditions provide an environment for nitrate to be reduced via denitrification. Despite this success, incomplete denitrification might increase nitrous oxide (N2O) emissions and more reducing conditions might increase methanogenesis, resulting in increased methane (CH4) emissions. These two gases, N2O and CH4, are potent greenhouse gases (GHG) and N2O also depletes stratospheric ozone. This potential pollution swapping of nitrate reduction for GHG production could negatively impact the desirability of this BMP. We conducted three years of static chamber measurements of GHG emissions from the soil surface in farm plots with and without DWM in a corn–soybean rotation on the Delmarva Peninsula. We found that DWM raised the water table at the drainage ditch edge, but had no statistically significant effect on water-filled pore space in the field soil surface. Nor did we find a significant effect of DWM on GHG emissions. These findings are encouraging and suggest that, at least for this farm site, DWM can be used to remove nitrate without a significant tradeoff of increased GHG emissions.

Effect of Drainage Water Management on Nitrate Nitrogen Loss to Tile Drains in North Carolina

Abstract. Short-term studies have demonstrated that drainage water management (DWM), or controlled drainage (CD), can be used to substantially reduce the loss of nitrogen (N) from drained lands for a wide range of soils, crops, locations, and climates. Long-term studies on the effects of the practice are limited. This article presents results on the effects of CD on nitrate-N (NO3-N) losses for three crops, corn ( L.), wheat ( L.), and soybean ( [L.] Merr.), in a two-year rotation in North Carolina. Nitrate losses were measured on replicated plots under CD and conventional, or free drainage (FD), treatments for nine years between 1992 and 2012 on a tile-drained site near Plymouth, North Carolina. The site is on a Portsmouth sandy loam soil with parallel drains 22.9 m apart and 1.15 m deep. The subsurface drainage characteristics under FD were drainage intensity (DI) = 8 mm d-1, drainage coefficient (DC) = 14 mm d-1, and Kirkham coefficient (KC) = 18 mm d-1. Compared to FD, CD reduced annual drainage outflow by 33% and NO3-N export by 30%, with an average annual reduction of 6.3 kg ha-1 year-1. CD increased average NO3-N concentrations by 0.9 mg L-1, but the difference was not significant. The reduction in NO3-N export observed in the CD treatment was equal to the increase in N removed by the harvested grain. The results document the effects of CD on NO3-N export over a wide range of weather conditions during the nine-year study. While the average 30% reduction in NO3-N losses in drainage water is in the midrange of that reported by previous studies for different soils and climates, this is believed to be the first time such a reduction has been attributed to the effect of CD on increasing yields and N removed in the harvested grain. Keywords: Controlled drainage (CD), Corn, Drainage water, Drainage water management (DWM), Nitrate, Nitrogen, Soybean, Water quality, Wheat.

Dissolved organic carbon loading from the field to watershed scale in tile-drained landscapes

Subsurface tile drains influence watershed fluxes of nitrogen, phosphorus, and pesticides, but few studies have examined the role of subsurface tile drains and drainage water management practices on watershed dissolved organic carbon (DOC) export. The objective of this study was therefore to quantify the contribution of subsurface tile drains to watershed DOC export and to evaluate the effect of drainage water management of DOC concentrations and loads in tile-drained fields. Discharge and DOC concentration were measured at the outlet of an agricultural headwater watershed (3.9km2) in Ohio, USA and all of the subsurface tile drains (6 total) within the watershed over an 8-year period. Results showed that DOC concentration in both subsurface tile drains and stream water were highly variable (0.1–44.4mgL−1), with mean DOC concentrations ranging from 5.7 to 8.2mgL−1. Intra-annual variability in subsurface tile drain and watershed hydrology yielded seasonal differences in DOC loading. Over the study period, 81.7% and 92.4% of watershed and subsurface tile drain DOC loading, respectively, occurred during 20% of the time, typically during winter and spring high flow events. Mean annual DOC loading from the drainage network was 19.6kgha−1, while mean annual DOC loading at the watershed outlet was 43.9kgha−1. On average, subsurface tile drainage comprised 33% of monthly watershed DOC export (<1–82%). Implementing drainage water management at one of the subsurface tile drains decreased discharge (179mm; 22%) and DOC loading (6.8kgha−1; 26%) compared to an adjacent free draining subsurface tile drain. Findings from this study demonstrate the utility of simultaneously monitoring solute fluxes from both field and watershed scales, and indicate that subsurface tile drains are a significant source of DOC to headwater agricultural streams. Further, results suggest that drainage water management can significantly decrease DOC losses from tile-drained fields.

Drainage water management effects on tile discharge and water quality

Drainage water management (DWM) has received considerable attention as a potential best management practice (BMP) for improving water quality in tile drained landscapes. The objective of this study was to evaluate the effects of DWM on subsurface drain discharge as well as on nitrogen (N) and phosphorus (P) loads in drainage water. Tile discharge and nutrient concentrations were measured from two adjacent tile drainage outlets in an Ohio, USA headwater watershed for 7 years (2006–2012). A control structure was installed in 2009 to allow DWM at one of the outlets from 2009 to 2012. A before–after control–impact (BACI) study design was used to assess the impact of DWM on tile discharge and nutrient loads. Results showed that DWM significantly decreased annual tile discharge between 11 and 178mm, which was equivalent to an 8 to 34% reduction in flow. DWM significantly decreased annual NO3N loads by −1.3 to 26.8kgha−1 (−8 to 44%) and annual dissolved P loads by 0.04 to 0.51kgha−1 (40 to 68%). Nutrient concentrations were not significantly affected by DWM indicating that decreases in nutrient loads were primarily due to reductions in tile discharge rather than changes in concentration. Results from the current study support the use of DWM as a BMP to decrease N and P loads in subsurface drain discharge throughout the U.S. Midwest. Future research should focus on quantifying the effect of DWM on nutrient transport in other flow paths (e.g., lateral seepage, surface runoff) to further evaluate its use as a BMP in tile drained landscapes.

Effects of drainage water management on crop yields in North Carolina

Research studies on a wide range of soils, crops, locations, and climates have shown that drainage water management (DWM), or controlled drainage (CD), can be used to substantially reduce the loss of nitrogen (N), and in some cases, phosphorus (P) from drained agricultural lands to surface waters. The adoption and widespread application of DWM depends on a variety of factors including its impact on crop yields. This paper presents results from a long term field study on the effect of DWM or CD on crop yields in a three-crop, two-year corn/wheat–soybean rotation. Yields were measured on replicated field scale plots under CD and conventional or free drainage (FD) treatments for a total of 18 crops on two experimental sites during the period from 1990 to 2011. Data were collected on 7 corn (<i>Zea mays</i> L.) crops, 5 wheat (<i>Triticum aestivum</i> L.) crops, and 6 soybean (<i>Glycine max</i> L.) crops. Controlled drainage had no significant effect on yields of winter wheat, which in North Carolina is grown in the wettest, coolest part of the year. Controlled drainage increased corn yields compared to FD in all seven years. The average yield increase for corn was 11%. Controlled drainage also increased soybean yield in all years with an average increase of 10% compared to FD. Such yield responses will promote the application of DWM, which will result in both economic and environmental benefits.

Measuring and modeling the effects of drainage water management on soil greenhouse gas fluxes from corn and soybean fields

Controlled tile drainage can boost crop yields and improve water quality, but it also has the potential to increase GHG emissions. This study compared in-situ chamber-based measures of soil CH4, N2O, and CO2 fluxes for silt loam soil under corn and soybean cropping with conventional tile drainage (UTD) and controlled tile drainage (CTD). A semi-empirical model (NEMIS-NOE) was also used to predict soil N2O fluxes from soils using observed soil data. Observed N2O and CH4 fluxes between UTD and CTD fields during the farming season were not significantly different at 0.05 level. Soils were primarily a sink for CH4 but in some cases a source (sources were associated exclusively with CTD). The average N2O fluxes measured ranged between 0.003 and 0.028 kg N ha−1 day−1. There were some significantly higher (p ≤ 0.05) CO2 fluxes associated with CTD relative to UTD during some years of study. Correlation analyses indicated that the shallower the water table, the greater the CO2 fluxes. Higher corn plant C for CTD tended to offset estimated higher CTD CO2 C losses via soil respiration by ∼100–300 kg C ha−1. There were good fits between observed and predicted (NEMIS–NOE) N2O fluxes for corn (R2 = 0.70) and soybean (R2 = 0.53). Predicted N2O fluxes were higher for CTD for approximately 70% of the paired-field study periods suggesting that soil physical factors, such as water-filled pore space, imposed by CTD have potentially strong impacts on net N fluxes. Model predictions of daily cumulative N2O fluxes for the agronomically-active study period for corn-CTD and corn-UTD, as a percentage of total N fertilizer applied, were 3.1% and 2.6%, respectively. For predicted N2O fluxes on basis of yield units, indices were 0.0005 and 0.0004 (kg N kg−1 crop grain yield) for CTD and UTD corn fields, respectively, and 0.0011 and 0.0005 for CTD and UTD soybean fields, respectively.

Performance of drainage water management systems in Illinois, United States

Drainage water management (DWM) is the practice of varying the drainage intensity of a subsurface drainage system to ensure that no more water is transported from a field than is necessary for optimizing crop growth and for facilitating seedbed preparation and other agrotechnical practices. This variation is achieved by using stop logs in a control structure to adjust the outlet elevation of the drainage system. An experiment was set up to test the hypothesis that the implementation of this practice will reduce nitrate (NO₃) loads from subsurface drainage systems in Illinois, United States, without adversely affecting yields. This experiment consisted of instrumenting and collecting precipitation, flow, and water quality data from four pairs of fields on different soils in Illinois. Each pair consisted of one field with a conventional (free) drainage system and one field with a drainage system whose outlet was managed in accordance with the Illinois Practice Standard for DWM. Annual NO₃ load reductions from the managed fields ranged from 37% to 79%, with an average load reduction of 61%. However, because of difficulties in measuring flow under submerged outlet conditions and because water left the managed fields by pathways other than through the outlets of the drainage systems, the efficacy of the practice is likely less than these numbers would indicate. There were no consistent patterns to the relationship between DWM and yields. In some instances, yields increased on the managed fields, and in others, yields decreased. Because of confounding factors, such as weather and topography, studies of longer duration are required to determine the effect of DWM on yield.

Development and application of a distributed modeling approach to assess the watershed-scale impact of drainage water management

Drainage water management, also known as controlled drainage, is the practice of using a water table control structure at the end of the subsurface drain pipe to reduce subsurface drainage, and thereby nitrate losses. Methods to quantify the potential effects of drainage water management for entire watersheds are needed to evaluate the impacts of large-scale adoption. A distributed modeling approach was developed to apply the field-scale DRAINMOD model at the watershed scale, and used to assess the impact of drainage water management on nitrate load from an intensively subsurface drained agricultural watershed in west central Indiana. The watershed was divided into 6460 grid cells for which drain spacing, soil parent material, and cropping pattern were estimated, resulting in 600 unique field conditions. The annual edge-of-field nitrate load from each grid cell was estimated as the product of DRAINMOD-predicted drain flow and the average annual nitrate concentration in drain flow, estimated from observations from related drainage sites in northern Indiana. Predicted monthly streamflow was in good agreement with the observed streamflow (Nash–Sutcliffe efficiency of 0.87 and 0.84 during the calibration and validation periods, respectively) and the predicted drain flow matched well with the measured drain flow (77.1cm vs. 77.8cm and 121.3cm vs. 128.4cm). Drainage water management decreased the average annual (1985–2009) predicted drain flow from 11.0 to 5.9cm, and the total nitrate load through subsurface drainage from 236 to 126ton (both about 47% reduction). The percent reduction in nitrate load varied between 40% and 53% for all combinations of drain spacing, soil parent material and cropping patterns, with drain spacing and soil parent material having a greater effect than cropping pattern. The methodology developed in this study showed potential for predicting the watershed-scale effects of subsurface drainage and drainage water management in drained agricultural watersheds.

A DRAINMOD-Based Method to Estimate Effects of Drainage Water Management on Annual Nitrogen Loss to Surface Water

Effects of drainage water management (DWM) on nitrogen (N) losses to surface waters can be estimated by multiplying the change in subsurface drainage and surface runoff, as predicted by DRAINMOD, by long-term mean nitrogen (N) concentration, which is a function of local site conditions (climate, soil, cropping system, farming practices, and drainage system). Consistent with experimental observations from several sources, this approximate method assumes that the effect of DWM on N losses is proportional to its effect on drainage and surface runoff volumes. The reliability of the method was evaluated by comparing estimated annual N losses for two sites (one in North Carolina and one in Illinois) to those predicted by the process-based nitrogen model DRAINMOD-NII. The long-term N concentrations used in the approximate method were based on DRAINMOD-NII predictions. DRAINMOD-NII simulations predicted that DWM would reduce long-term average N losses to surface waters by 35% for continuous corn (CC) and 33% for a corn-wheat-soybean (CWS) rotation in North Carolina and by 31% and 26% for CC and a corn-soybean (CS) rotation in Illinois. The approximate method estimated the annual effect of DWM on N losses within 3 kg ha-1 of that predicted by DRAINMOD-NII in over 68% of the years for the CWS and CS rotations at both sites and in over 51% of the years for CC. Overestimated effects in some years were balanced by underestimated effects in others. However, relatively large errors occurred in about 25% of the years when N concentrations in the drainage water varied significantly from the long-term average. These errors typically occurred following periods when crop yields deviated significantly from the average. When these outliers were excluded from the analyses, the goodness of fit between annual N losses predicted by DRAINMOD-NII and annual losses estimated by the approximate method was substantially improved (Nash-Sutcliffe EF values ranging from 0.54 to 0.79). Although more research is needed to improve the approximate method when concentrations vary significantly from the long-term average, the results presented herein indicate that the method provides a reliable means of assessing impacts of DWM under normal conditions.

Water Balance Investigation of Drainage Water Management in Non-Weighing Lysimeters

Artificial subsurface drainage systems are often used throughout the upper Midwest to remove excess precipitation and improve crop production. However, these drainage systems export nitrate-nitrogen (NO3-N) to downstream water resources. Management practices are needed to reduce this export of NO3-N with subsurface drainage water. One such practice being considered is the use of drainage water management where subsurface water is held in the soil profile during portions of the year. Previous research has shown that drainage water management has potential to reduce subsurface drainage volume but there is still a need to understand the performance of the practice and the pathways of water flow under varying conditions. The objectives of this study, therefore, were to quantify the pathways of water movement for conventional or free drainage (FD) and drainage water management (DWM) during the growing season. In this study, six non-weighing lysimeters (0.92 2.30 m) with a depth of 120 cm were monitored over a 3-yr period under natural and simulated rainfall conditions. The objectives were performed to measure the effects of drainage water management (DWM) on surface runoff, subsurface drainage, and crop yield. The in-season data from natural rainfall conditions showed that DWM reduced subsurface drainage by approximately 14%. The simulated rainfall data showed that DWM increased surface runoff by 54% when the water table was established at 90 cm below the soil surface, and by 87% when the water table was established at 60 cm below the soil surface. Overall DWM was found to have the potential to reduce subsurface drainage but there is the potential that at least a portion of this reduction may be reflected in an increase in surface runoff.

Predicting effects of drainage water management in Iowa's subsurface drained landscapes

Long-term hydrologic simulations are presented predicting the effects of drainage water management on subsurface drainage, surface runoff and crop production in Iowa's subsurface drained landscapes. The deterministic hydrologic model, DRAINMOD was used to simulate Webster (fine-loamy, mixed, superactive, mesic) soil in a Continuous Corn rotation (WEBS_CC) with different drain depths from 0.75 to 1.20 m and drain spacing from 10 to 50 m in a combination of free and controlled drainage over a weather record of 60 (1945–2004) years. Shallow drainage is defined as drains installed at a drain depth of 0.75 m, and controlled drainage with a drain depth of 1.20 m restricts flow at the drain outlet to maintain a water table at 0.60 m below surface level during the winter (November–March) and summer (June–August) months. These drainage design and management modifications were evaluated against conventional drainage system installed at a drain depth of 1.20 m with free drainage at the drain outlet. The simulation results indicate the potential of a tradeoff between subsurface drainage and surface runoff as a pathway to remove excess water from the system. While a reduction of subsurface drainage may occur through the use of shallow and controlled drainage, these practices may increase surface runoff in Iowa's subsurface drained landscapes. The simulations also indicate that shallow and controlled drainage might increase the excess water stress on crop production, and thereby result in slightly lower relative yields. Field experiments are needed to examine the pathways of water movement, total water balance, and crop production under shallow and controlled drainage in Iowa's subsurface drained landscapes.