Evaluation of DRAINMOD-DSSAT simulated effects of controlled drainage on crop yield, water balance, and water quality for a corn-soybean cropping system in central Iowa

Authors: NEGM, LAMYAA - North Carolina State University; YOUSSEF, MOHAMED - North Carolina State University; Jaynes, Dan

Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2017
Publication Date: 6/1/2017
Publication URL: http://handle.nal.usda.gov/10113/5646415
Citation: Negm, L., Youssef, M.A., Jaynes, D.B. 2017. Evaluation of DRAINMOD-DSSAT simulated effects of controlled drainage on crop yield, water balance, and water quality for a corn-soybean cropping system in central Iowa. Agricultural Water Management. 187:57-68. https://doi.org/10.1016/j.agwat.2017.03.010.

Interpretive Summary: The upper Midwest is the dominant source of nitrate to the Mississippi River and most of this nitrate enters surface waters through the extensive network of agricultural, subsurface drain pipes underlying the region. Drainage water management (DWM) is a potentially effective practice for reducing nitrate losses from artificial (tile) drainage, but its performance varies by climate, soils, and farming system. To fully evaluate the potential of DWM to improve water quality, computer modeling is required to test all the potential climate X soils X management combinations across the cornbelt. We tested the model DRAINMOD-DSSAT against four years of measured data to show that the model performs very well and is simulating DWM performance in central Iowa. If further testing at other sites across the cornbelt are as successful, we will have a valuable tool for estimating the water quality and crop yield benefits of DWM that can be used by farmers, researchers, and state and federal action agencies.

Technical Abstract: Controlled drainage (CD) has been identified as a sustainable management practice whereby more soil water can be conserved and fewer nutrients are leached; alongside its potential benefit of alleviating drought stress and increasing yield. More than 12 million hectares of cropland in the US Midwest are suitable for implementing CD; however, the effectiveness of the practice can vary across the region with the variation in environmental conditions and management practices. The main objective of the current study; the first among a series of ongoing similar studies across the U.S. Midwest, is to evaluate the performance of the integrated agro-ecosystem model; DRAINMOD-DSSAT, for simulating the effects of CD on drainage flow, nitrogen losses via drainage water and crop yield. Herein, we utilized a 4-yr dataset (2006-2009) that was collected from a corn–soybean cropping system near Story City, Iowa that is artificially drained, under free drainage (FD) and CD treatments. The model was calibrated using the data collected from the free drainage (FD) plots, and validated for the CD plots. DRAINMOD-DSSAT predictions of drainage flow and nitrate-nitrogen (NO3-N) losses were in good agreement with measured values under FD and CD, with the former treatment showed slightly better performance. The modeling efficiencies (NSE’s) for simulating monthly drainage flows were 0.81 and 0.60 for FD and CD, respectively. Monthly NO3–N mass losses were simulated with NSE’s of 0.76 and 0.66 for FD and CD, respectively. CD-induced percent reductions in annual drainage flow (measured = 24.6%, simulated= 27.1%), and NO3-N losses (measured=34.8%, simulated=33.5%) were well simulated by DRAINMOD-DSSAT. Low percent error (PE) values were associated with the model predictions of corn yields (-1.3 = PE = 1.3) and soybean yields (-6.0 = PE = 12.6). Overall, results obtained from this relatively short-term modeling evaluation study were promising and demonstrated the potential use of DRAINMOD-DSSAT as a management design tool. Yet, further model testing CD effectiveness under different conditions is critically needed to establish a higher credibility in model predictions.