Plant-to-plant biomass and yield variability in corn–soybean rotations under three tillage regimes

Authors: O'Brien, Peter; HATFIELD, JERRY - Retired ARS Employee

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2020
Publication Date: 1/21/2021
Publication URL: https://handle.nal.usda.gov/10113/7709370
Citation: O'Brien, P.L., Hatfield, J.L. 2021. Plant-to-plant biomass and yield variability in corn–soybean rotations under three tillage regimes. Agronomy Journal. 113(1):370-380. https://doi.org/10.1002/agj2.20514.
DOI: https://doi.org/10.1002/agj2.20514

Interpretive Summary: The demand for food, fuel, and fiber production from agricultural production systems is increasing with continuing human population growth and development of bioenergy capacity. This demand should not be met by converting more land to agricultural production both because of the severe environmental consequences and, in some cases, no more land is available for conversion. Thus, management practices must target improved production efficiency on existing agricultural land. One possible metric to assess efficiency in high-yielding corn (Zea mays L.)-soybean (Glycine max [Merr.] L.) rotation systems is plant-to-plant variability, as it represents how well management practices provide homogenous distribution, access, and uptake of resources. Numerous factors affect plant-to-plant variability, and the interaction of management practices under changing climate conditions is not well understood. This study examines the effects of a common management practice, tillage, on plant-to-plant variability from 2010-2013 in central Iowa. In three different tillage systems, conventional tillage, strip tillage, and no-tillage, corn and soybean plants were sampled at three different developmental stages each season, early-season (V6 growth stage), mid-season (VT in corn and R3 in soybean), and harvest. Plant-to-plant variability was assessed using the coefficient of variation (CV) for each group of plants taken from each experimental plot; 5-7 corn plants or 10 soybean plants were used as a representative sample from each plot. Plant-to-plant variability in neither biomass nor grain yield were affected by tillage practices, but they were different among each year, indicating that climate conditions influenced plant-to-plant variability more than tillage practices. Notably, in-season variability of plant biomass did not necessarily reflect differences in yield, as plant-to-plant variability in corn declined throughout the growing season but increased in soybean. Overall, corn grain yields increased as CV decreased, but soybean grain yield did not have a relationship with CV, indicating that crop stand uniformity is important to maintain high yielding corn stands but not soybean stands. These findings indicate that tillage practices in these systems are not driving plant-to-plant variability, such that attempts to manipulate crop stand uniformity should focus on other management practices. Land managers and producers will find this information useful in determining how their tillage practices are affecting plant-to-plant variability and crop yield.

Technical Abstract: Maintaining efficient, highly productive agroecosystems is essential to meet the increasing demand for food, fuel, and fiber caused by human population growth and expanding biofuels production. Since expanding land under agricultural production is not possible in some areas, management practices must target improved production efficiency. One possible metric to assess efficiency in high-yielding row crop systems is plant-to-plant variability, as it represents how well management practices provide homogenous distribution, access, and uptake of resources. Numerous factors affect plant-to-plant variability, and the interaction of management practices under changing climate conditions is not well understood. This experiment examines plant-to-plant variability at three developmental stages in corn (Zea mays L.)-soybean (Glycine max [Merr.] L.) rotations under conventional tillage, strip tillage, and no tillage. Plant-to-plant variability, as measured by the coefficient of variation (CV), did not differ among tillage systems for any developmental stage but did change among the four years of the experiment, indicating that climate conditions influenced plant-to-plant variability more than tillage practices. Notably, in-season variability of plant biomass did not necessarily reflect differences in yield, as plant-to-plant variability in corn declined throughout the growing season but increased in soybean. Overall, corn grain yields increased as CV decreased, but soybean grain yield did not have a relationship with CV, indicating that crop stand uniformity is important to maintain high yielding corn stands but not soybean stands. These findings indicate that tillage practices in these systems are not driving plant-to-plant variability, such that attempts to manipulate crop stand uniformity should focus on other management practices.