Modeling the impact of cereal rye as a winter cover crop on water and nitrogen cycling in the corn-soybean system at various scales

Gupta, Rishabh

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https://hdl.handle.net/2142/117644 Copy

Description

Title

Modeling the impact of cereal rye as a winter cover crop on water and nitrogen cycling in the corn-soybean system at various scales

Author(s)

Gupta, Rishabh

Issue Date

2022-11-14

Director of Research (if dissertation) or Advisor (if thesis)

Bhattarai, Rabin

Doctoral Committee Chair(s)

Bhattarai, Rabin

Committee Member(s)

• Kalita, Prasanta K
• Dokoohaki, Hamze
• Armstrong, Shalamar

Department of Study

Engineering Administration

Discipline

Agricultural & Biological Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Climate Change
• DSSAT
• Nitrate-Nitrogen
• Nutrient Loss
• Tile Drainage.

Abstract

With the rise in population, the higher demand for food has amplified fertilizer use. Extensive subsurface drainage usage in the midwestern US combined with excess nitrogen fertilization has triggered nutrient loss and water quality issues in the region, which over time endorsed the hypoxia formation in the Gulf of Mexico. Previous studies encourage using cereal rye as a winter cover crop in the maize-soybean rotation as an eco-efficient solution for reducing the nitrate-nitrogen (NO3-N) loss via sub-surface drainage channels. With several incentives and cost-sharing benefits promoted by USDA and Illinois state government, an increasing trend of cover cropping practices adoption is noticed all over Illinois. To support the efforts by the government and several agencies, the research presented in this dissertation is broadly aimed to model the impact of cereal rye as a winter cover crop on water and nitrogen cycling in the maize-soybean system at various scales. We evaluated the impact of cereal rye as a winter cover crop in the maize-soybean system on reducing nutrient loss via tile drainage using the DSSAT model at the field scale. The experiments include four treatments developed using the combination of two different nitrogen (N) application timing with cover crop (CC) and without cover crop (NCC)- fall-applied N with NCC (FN), spring-applied N with NCC (SN), fall-applied N with CC (FCC) and spring-applied N with CC (SCC). The model was able to replicate the cereal rye growth (R2>0.91). The calibrated DSSAT model was utilized to assess the impact of the cover crop by comparing NO3-N losses and cash crop yields between CC and NCC for different N fertilization timing. The model successfully predicted the reduction in NO3-N loss via tile drainage [FCC vs FN: 43.6% (48.6% observed) and SCC vs SN: 45.4% (47.8% observed)] and tile drainage volume [FCC vs FN: 21.3% (30.2% observed) and SCC vs SN: 21.0% (19.4% observed)]. However, the model could not replicate the cover crop impact on the maize growth due to higher N mineralization. The unavailability of the chemical application module could be the possible reason for such results. We assessed the long-term impact of the cereal rye on soil water-N and cash crop growth in the maize-soybean system over the state of Illinois. The cereal rye impact was estimated by compiling weather-soil-crop information at the grid-scale (4 km) for the last two decades from 2001-2020 for the treatments: FA-SP-C, FA-SP-N, SP-SD-C, and SP-SD-N. The NO3-N loss via tile flow and leaching reduction were observed to be 30.6% and 29.4% on average in Illinois. The tile drainage volume decreased by 20.8%, whereas the deep percolation decreased by 5.3% due to cereal rye inclusion. The CC impact on the maize yield was higher in FA-SD-C vs. FA-SD-N than SP-SD-C vs. SP-SD-N treatments, associated with higher N stress on the maize plant in FA-SD-N than SP-SD-N treatment. The year 2012 (drought year) experienced massive variability in the CC impacts. Finally, we investigated the climate change impact on the cover crop effect on the agro-ecological system in Illinois. We used the multi-ensemble DSSAT outputs simulated using the future projections of five regional climate models (RCMs) for the two warming scenarios: rcp4.5 and rcp8.5, and two time scenarios: 2030s (2021-2040) and 2050s (2041-2060). The climate change could drastically increase the NO3-N loadings up to 43.1% in the high emission scenario by the 2050s. The climate change could be favorable for cereal rye growth which could reduce the NO3-N loadings from the subsurface drainage channel more substantially in all the warming scenarios and time scenarios. However, the findings suggest that the cover cropping practice might not be able to alleviate the climate change impact in the future. Overall, the CC impact results at the field scale and state level were optimistic. The climate change assessment on the cover crop impact cautions the stakeholders for a potential risk on the cover cropping benefits associated climate change mitigation in the future. The research suggests that DSSAT is a reliable process-based crop model to predict cereal rye growth. The model results were insightful in envisaging the soil water-nutrient dynamics in both CC and NCC systems. However, the model was not able to predict the impact of cereal rye on the cash crop accurately due to the absence of a chemical module for terminating cereal rye growth. Moreover, more research to assess the climate change impacts is needed combining several agricultural practices to select the best combination of practices sustainable in future climate scenarios.

Graduation Semester

2022-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Rishabh Gupta

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