Carbon fluxes from a spring wheat–corn–soybean crop rotation under no‐tillage management

Abstract

The increase in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production in rainfed cropping systems of the northern Great Plains (NGP) has altered the delivery of ecosystem services from agricultural land. To date, there is limited understanding about how these crops affect the carbon (C) balance of cropping systems in the region when included in a short rotation window. This study sought to quantify C balance of a spring wheat (Triticum aestivum L.)–corn—soybean rotation under no‐tillage management using eddy covariance (EC) techniques. Paired field sites with the same soil type near Mandan, ND, were used for the study. Annual net ecosystem production (NEP) by crop was –34, 120, and 7 g C m–2 y–1 for spring wheat, corn, and soybean, respectively. Carbon removed in grain over the rotation was less than a third of C lost by ecosystem respiration (ER) (210 vs. 674 g C m–2 y–1). After accounting for grain C removal, net ecosystem carbon balance (NECB) was –164, –253, and –121 g m–2 y–1 for spring wheat, corn, and soybean, respectively, with a mean NECB of –179 ± 39 g C m–2 y–1 (P = .043; t test for difference from zero), implying the rotation was a net C source. Time associated with active crop growth each year was 27% for spring wheat, 41% for corn, and 28% for soybean. Management strategies that lengthen the period of biomass growth may mitigate C loss from spring wheat–corn–soybean rotations in the NGP.

Crop‐ and weather‐dependent yield and wind erosion benefits from a conservation practices system

“…Ten sampling sites were randomly selected in each field for biomass and grain yield measurements as established in 2016 (Liebig et al., 2022). This randomization area included the entire field excluding the wind erosion measurement area.…”

Cover crop inclusion and residue retention improves soybean production and physiology in drought conditions

“…From 1984 through 2015 fields were managed as rainfed cropping systems as reviewed by Liebig et al [ 3 ]. Between 2016 and 2018, both fields were cropped with a spring wheat – corn – soybean rotation under no-tillage management.…”

“…Continuous measurements of eddy covariance, meteorological, and soil moisture were undertaken in both 2018 and 2021 as previously described [ 3 , 29 ]. Briefly, a tripod held an n open-path gas analyzer (model LI-7500A; Li-Cor Inc., Lincoln, NE) and a sonic anemometer (model CSAT3; Campbell Scientific Inc., Logan, UT) 2.8 m above the ground.…”

“…production has been expanding westward in North Dakota due to a combination of climate change, the release of short-season and herbicide-resistant varieties, and the adoption of no-till management practices [ 1 ]. Over this time, soybean seed yield under near-normal precipitation conditions has increased nearly four-fold [ 2 , 3 ].…”

“…These measurements allow for site-level and network level comparisons between contrasting management practices. Carbon and water flux data from the NGP LTAR fields have two of these eddy covariance towers have been previously reported [ 3 , 24 , 25 ], including flux measurements from 2018, when soybean was planted in these fields using the business-as-usual management practices [ 3 ]. The NGP LTAR fields have the lowest mean annual temperature (5.1 °C), mean annual precipitation (496 mm), average annual gross primary production (GPP, 601 g m 2 ), and average annual ecosystem respiration (Reco, 595 g m −2 ) of the six LTAR locations growing soybean [ 24 ].…”