Abstract
Winter cover crops, like cereal rye ( Secale cereale ), are one of the most promising solutions to environmental sustainability in the maize ( Zea mays L.)-soybean ( Glycine max L. merr.) cropping systems of the Midwestern US. However, one of the largest barriers to adoption is the “yield drag,” or decrease in cash crop yield that occurs when following cereal rye (especially with maize). Reports of maize yield drag are inconsistent, and the underlying mechanisms are unclear. Our primary research questions were: i. Does fertilizer N alleviate maize yield drag? ii. does hillslope position change soil N dynamics and maize N needs after cereal rye cover crop? iii. what factors across site-years and hillslopes best predict maize yields? We conducted a split-plot experiment [cover/no-cover × six nitrogen (N) rates] across three hillslope positions (summit, backslope, and toeslope) over three site-years. Fertilizer N rates ranged from 0 to 336 kg N ha −1 . In response, we measured soil N dynamics (net N mineralization, inorganic and organic N pools), crop grain yield, and response to N fertilizer. We also ran a random forest model to identify the most important factors affecting yield drag. There were few, weak interactive effects of hillslope position and cover crops on soil N dynamics. Toeslope positions tended to increase soil N pools. Cover crops had weaker effects on soil N dynamics but did decrease soil nitrate by 26%, on average, across the field. There were more complex hillslope × cover crop interactions on maize yield response to N fertilizer. While fertilizer N partially alleviated maize yield drag, yields remained consistently lower under cover crops compared to winter fallow, particularly at summit and backslope positions characterized by lower soil organic matter (SOM). Random forest modeling identified N application rate, cereal rye biomass, soil test phosphorus, and SOM as key predictors of maize yield, and revealed complex interactions between management and hillslope factors (i.e., soil properties). Our findings emphasize the importance of considering landscape variability when optimizing N management in cereal rye-maize systems to mitigate yield penalties and enhance nutrient use efficiency. The soil variation that comes from hillslope positions has complex interactions with cover crops and fertilizer N. These interactions need to be considered, and managed appropriately, to ensure farmers have reliable maize crop yields when following a cereal rye winter cover crop. • Hillslope position strongly regulates soil organic and inorganic N pools and maize N needs. • Cereal rye reduces inorganic soil N and causes consistent maize yield drag that is not fully reversed by fertilizer N. • Soil test P and organic matter are important factors regulating maize yield. • Precision management and conservation are key to reliable yields and efficient N fertilizer use.
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Claims 8
Claim · model-written summary
Hillslope and cover crop interactions had few weak effects on soil nitrogen dynamics.
Zea maysNot reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There were few, weak interactive effects of hillslope position and cover crops on soil N dynamics”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Toeslope positions tended to increase soil nitrogen pools.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Toeslope positions tended to increase soil N pools”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Cover crops decreased soil nitrate by 26% on average across the field.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cover crops had weaker effects on soil N dynamics but did decrease soil nitrate by 26%, on average, across the field”
e1“maize ( Zea mays L.)”
e2“cover/no-cover”
Claim · model-written summary
Hillslope and cover crop conditions interacted in maize yield response to nitrogen fertilizer.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There were more complex hillslope × cover crop interactions on maize yield response to N fertilizer”
Claim · model-written summary
Nitrogen fertilizer partially alleviated maize yield drag after cover crops.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“fertilizer N partially alleviated maize yield drag”
e1“maize ( Zea mays L.)”
e2“six nitrogen (N) rates”
Claim · model-written summary
Maize yields under cover crops remained below winter fallow, particularly on summit and backslope positions.
- Treatment
- cover cropse0
- Outcome
- yieldse0
- Direction
- lowere0
- Comparator
- winter fallowe0
- Setting
- summit and backslope positionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yields remained consistently lower under cover crops compared to winter fallow, particularly at summit and backslope positions characterized by lower soil organic matter (SOM)”
e1“maize ( Zea mays L.)”
Claim · model-written summary
Random forest modeling identified nitrogen application rate, rye biomass, soil phosphorus and organic matter as key maize yield predictors.
- Outcome
- key predictors of maize yielde0
- Value
- N application rate, cereal rye biomass, soil test phosphorus, and SOMe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Random forest modeling identified N application rate, cereal rye biomass, soil test phosphorus, and SOM as key predictors of maize yield”
e1“maize ( Zea mays L.)”
Claim · model-written summary
The authors recommend accounting for landscape variability when optimizing nitrogen management after cereal rye.
- Outcome
- considering landscape variability when optimizing N managemente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“considering landscape variability when optimizing N management in cereal rye-maize systems to mitigate yield penalties and enhance nutrient use efficiency”
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