Drainmod-Linked Interface for Evaluating Drainage System Response to Climate Scenarios

This article presents the development of a drainage-climate interface that incorporates climatological data, crop drainage requirements, and drainage theory into a procedure for characterizing drainage system response under different climate scenarios. The drainage-climate interface is suitable for assessing potential county-level impacts of climate change on crop production, soil hydrology and subsequently on subsurface drainage design. Climate model projections from two general circulation models (GCMs), namely CCSM4 (Community Climate System Model) and MIROC5 (Model for Interdisciplinary Research on Climate), were used to create the climatological database for the drainage-climate interface. DRAINMOD was integrated into the Visual Basic for Applications (VBA) portion of the interface to simulate the performance of subsurface drainage systems in Illinois for the near future (2040 to 2069) and the far future (2070 to 2099) periods. Case studies were developed with the interface for Adams and Champaign Counties in Illinois for their predominant soil types. Hydrologic simulations from the interface were used to determine the optimal depth and spacing of tile drains that maximize crop yield for corn and soybean during the mid and late 21st century. Drainage water management (DWM) was incorporated into the drainage-climate interface to investigate the potential of DWM in the future climate scenarios to maintain water quality, reduce nutrient losses and minimize pollutant loading from drained fields by controlling the timing and amount of water discharged from agricultural drainage systems. Results from DRAINMOD simulations with MIROC5 show a significant decline in crop yield due to extreme heat stress. Corn yield in the future showed a severe reduction while the yield for soybean demonstrated a gradual decline over the years. DWM had only a minimal effect on future crop yield trends. The drainage-climate interface simulated subsurface drainage conditions and made evident the consequences of environmental conditions on crop physiological processes under scenarios of climate change predicted by MIROC5. Keywords: Agricultural system models, Climate change impacts, Drainage-climate interface, Drainage water management, Subsurface drainage, Tile drain depth, Tile drain spacing.

Sustainable Water Management in Agriculture—The Impact of Drainage Water Management on Groundwater Table Dynamics and Subsurface Outflow

The paper presents the results of the effects of control drainage (CD) on the groundwater table and subsurface outflow in Central Poland. The hydrologic model DRAINMOD was used to simulate soil water balance with drain spacing of 7 and 14 m, different initial groundwater Table 40, 60 and 80 cm b.s.l., and dates at the beginning of control drainage of 1 March, 15 March, 1 April, and 15 April. The CD restricts flow at the drain outlet to maintain a water table during the growing season. Simulations were made for the periods from March to September for the years 2014, 2017, and 2018, which were average, wet, and dry, respectively. The simulations showed a significant influence of the initial groundwater tables and date blocking the outflow from the drainage network on the obtained results. In the conditions of central Poland, the use of CD is rational only when it is started between 1 and 15 March. In this case, the groundwater table can be increased from 10 to 33 cm (7 m spacing) and from 10 to 41 cm (14 m spacing) in relation to the conventional system (free drainage—FD). In the case of blocking the outflow on 1 March, the reduction is about 80% on average in the period from March to September. With a delay in blocking the outflow, the impact of CDs decreases and ranges from 8% to 50%. Studies have shown that the proper use of the drainage network infrastructure complies with the idea of sustainable development, as it allows efficient water management, by reduction of the outflow and, thus, nitrates from agricultural areas. Furthermore, CD solutions can contribute to mitigating the effects of climate change on agriculture by reducing drought and flood risk.

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

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.

Effects of Subsurface Drainage Systems on Water and Nitrogen Footprints Simulated with RZWQM2

Developing drainage water management (DWM) systems in the Midwest to reduce nitrogen (N) transport to the northern Gulf of Mexico hypoxic zone requires understanding of the long-term performance of these systems. Few studies have evaluated long-term impacts of DWM, and the simulation of controlled drainage (CD) with the Root Zone Water Quality Model (RZWQM) is limited, while shallow drainage (SD) has not been examined. We tested RZWQM using nine years (2007-2015) of field data from southeast Iowa for CD, SD, conventional drainage (DD), and undrained (ND) systems and simulated the long-term (1971-2015) impacts. RZWQM accurately simulated N loss in subsurface drainage, and the simulations agreed with field data that CD and SD substantially reduced N loss to drainage. As indicated by the field data, the SD N concentration was predicted to be greater than DD and CD, likely due to reduced time of travel to shallower drains. The long-term simulations show that CD and SD reduced annual N lost via tile drainage by 26% and 40%, respectively. Annual reductions in N lost via tile drainage ranged from 28% in the driest years to 22% in the wettest years for CD and from 56% in the driest years to 35% in the wettest years for SD. Considering spring N loading for the purpose of addressing hypoxia in the Gulf of Mexico, CD was found to be less effective than SD, and in many years CD exported more N in the spring than DD. Spring N loading (April through June) was indicated by the EPA Science Advisory Board to have the greatest impact on hypoxia in the northern Gulf of Mexico. Therefore, improvement of CD systems within the months of April through June to reduce N loss via drainage across the upper Midwest landscape may be required. Limited research in the upper Midwest has addressed spring N loading under controlled drainage systems (CD). This research will help model developers, model users, and agricultural scientists more clearly understand N transport under different systems, including CD, SD, and ND, which will aid in developing the design and management of drainage systems to reduce N transport from tile-drained agriculture to surface waters. Keywords: Agricultural simulation model, Drainage water management, Nonpoint-source pollution, Northern Gulf of Mexico hypoxic zone, Nutrient reduction, Subsurface drainage.