31st May 2023
CONSERVATION ACTIVITIES & PRACTICES
164 Improved Management of Drainage Water Design, 447 Irrigation and Drainage Tailwater
Recovery, 554 Drainage Water Management, 587 Structure for Water Control, 604 Saturated
Buffer, 605 Denitrifying Bioreactor, 606 Subsurface Drain, 620 Underground Outlet
Agricultural drainage is one of the cornerstones of healthy agricultural soils and underpins much
of our soil health improvement and climate change adaptation/mitigation efforts in the
agricultural sector. Conservation drainage is a suite of practices (listed above) that provides
both the drainage necessary for crop production while addressing the negative water quality
impacts that are associated with traditional agricultural drainage. Drainage and water
management practices can provide the most durable approach at reducing greenhouse gas
(GHG) emissions from the agricultural sector as it is the greatest tool in limiting nitrous oxide
It is well documented that nitrous oxide is the largest contributor to GHG emissions from the
agricultural sector and accounts for ~5% of the total GHG emissions produced by the United
States. Conservation drainage, specifically drainage water management (DWM), has the
potential to greatly reduce nitrous oxide emissions and increase nitrogen fertilizer use efficiency
from crop production by reducing excess soil water after fertilizer application (#1 reason for
nitrous oxide emissions). Managed drainage improves soil nutrient cycling, driving down the
amount of nitrogen needed to produce high yields and reducing GHG emissions. Reduction of
synthetic nitrogen fertilizer application reduces the need to produce synthetic nitrogen fertilizer.
At present, synthetic nitrogen fertilizer production across approximately 400 plants worldwide
accounts for 2% of the total global energy consumption and 1% of global GHG emissions.
DWM is also an effective companion practice to many notable greenhouse gas reduction
practices such as cover crops and no till, and enables the effective implementation of the
nutrient management 4 Rs (right time, right rate, right source, and right place) by allowing better
trafficability of fields for timely application, ensuring improved nutrient use efficiency and
reducing potential losses to the atmosphere and water. Using DWM prescriptively will allow for
optimal root growth and has the potential to increase subsoil carbon sequestration, which is
much more stable than surface soil carbon sequestration and management.
N2O/GHG Production and Nutrient Use Efficiency (NUE)
Water management and drainage can provide the most durable approach to reducing greenhouse
gas emissions from the agricultural sector as it is the greatest management tool in limiting
nitrous oxide (N2O) emissions. Two thirds of all greenhouse gas emissions from agriculture stem
from nitrogen. In the short term, uncontrolled/conventional drainage alone increases carbon
emissions, but this impact is quickly offset by more substantial reductions in N20 – which is
approximately 287 times as powerful as a GHG. By implementing conservation drainage practices
comprehensively, as opposed to uncontrolled drainage, the soil carbon structure is better
protected while reducing N2O emissions, helping reduce the potential negative effects of
● Nitrogen (N) fertilizer is the primary source of N2O emissions in cereal cropping systems,
and most N2O emitted from soil mineralization stems from denitrification near the soil
● N2O losses increase rapidly when weather conditions impact a crop’s ability to efficiently
use applied N fertilizer, and compounding this is the uncertainty of optimum N input that
is >100 kg N ha-1 from field to field and year to year.
● Research from Iowa State University demonstrates that DWM (554) designed under DIA
164 that uses structure for water control (587) with facilitating components 606 and/or
620 had the greatest agronomic efficiency (kg grain per kg N) and the least yield
variability. The study demonstrated that drainage reduces the amount and interannual
variability of N fertilizer requirements while also reducing interannual variability in yields
● Average annual agronomic optimum N fertilizer rate (AONR) for corn in drained vs.
undrained is 169 lb N/ac vs 191 lb N/ac., an almost 12% decrease (2). This 22 lbs.
reduction in N fertilizer provides 107.14 lbs. CO2-e reduction (each pound of nitrogen
applied is assumed to result in CO2-e emissions of 4.87 lbs.) (3).
● Excluding the effect on soil organic carbon (SOC), drainage reduces annual emission of
CO2 by ~2,000 kg CO2e ha-1 yr-1 due to lower N fertilizer inputs and N2O emissions (2).
Enhances CSAF Practices
● Adapting to a changing climate will necessitate updating agricultural drainage systems
to meet more intense and variable precipitation events (2).
● Drainage research at Purdue University documented an increased cover crop biomass
for drained vs. undrained farm land (4).
● A good drainage system (a system that incorporates conservation drainage and is
designed to meet future precipitation patterns) is a necessary first step to improving
crop yields and soil health on naturally poorly drained soils (4).
● It is critical that producers are able to design new conservation drainage systems with
the support of experienced technical services, and using NRCS technical standards,
guidance and funding resources. Access to CSAF, funding for the conservation drainage
practices listed above is a critical first step to providing the necessary tools to our
producers to both adapt to a changing climate and contribute to climate change
● Aging agricultural drainage infrastructure compounded by a changing climate will
necessitate major updates to agricultural drainage to meet future production needs. This
creates an opportunity for systems to be designed to achieve production, water quality,
and climate change goals.
● A systems-based approach to drainage that utilizes conservation drainage practices and
is designed for more intense precipitation events can consistently increase NUE, reduce
N2O, while maintaining or increasing crop production, helping to reduce GHG emissions,
maintain long-term farmer profitability, and achieve environmental goals.
- Ellen D.v.L. Maas, Sotirios V. Archontoulis, Matthew J. Helmers, Javed Iqbal, Carl H.
Pederson, Hanna J. Poffenbarger, Kristina J. TeBockhorst, Michael J. Castellano,
Subsurface drainage reduces the amount and interannual variability of optimum nitrogen
fertilizer input to maize cropping systems in southeast Iowa, USA, Field Crops Research,
Volume 288, 2022, 108663, ISSN 0378-4290, https://doi.org/10.1016/j.fcr.2022.108663.
- Castellano, M.J., Archontoulis, S.V., Helmers, M.J. et al. Sustainable intensification of
agricultural drainage. Nat Sustain 2, 914–921 (2019).
- Claassen, Roger, John Horowitz, Eric Duquette, and Kohei Ueda. Additionality in U.S.
Agricultural Conservation and Regulatory Offset Programs, ERR-170, U.S. Department of
Agriculture, Economic Research Service, July 2014.
- Kladivko, Eileen, Soil Drainage Impacts on Cover Crop Growth and Soil Improvement,
Insights from Long-Term SEPAC study.