Contrasting cropping system effects on phenology and ecophysiology attributes in the northern Great Plains

Authors: Whippo, Craig; Saliendra, Nicanor; Liebig, Mark

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/18/2023
Publication Date: 8/7/2023
Citation: Whippo, C.W., Saliendra, N.Z., Liebig, M.A. 2023. Contrasting cropping system effects on phenology and ecophysiology attributes in the northern Great Plains. Meeting Abstract. 1.

Interpretive Summary:

Technical Abstract: Cropping systems in the northern Great plains are increasingly dominated by input-intensive low-diversity crop rotations. However, this management approach can negatively impact long-term productivity, soil health, and environmental quality. Therefore, it is important to develop and compare common cropping practices with alternative cropping practices intended to improve sustainability and ecosystem functioning. We established an experiment comparing a prevailing cropping system with an alternative that included cover crops and dynamic nutrient and pest-management practices. To understand how these contrasting practices impact crop phenology and physiology, we integrated PhenoCam observations with eddy covariance and meteorological measurements to compare how management affects the phenological and physiological attributes of spring wheat (Triticum aestivum L.) corn (Zea mays L)., and soybean (Glycine max (L.) Merr) in a three-year crop rotation. Phenophase transition dates were identified from the green-chromatic-coordinate time series. Ecophysiology attributes were calculated from eddy covariance and metrological measurements using the ‘big-leaf’ framework to calculate surface conductance, stomatal slope parameters, stomatal sensitivity to vapor pressure deficit (VPD), canopy photosynthetic capacity, water-use-efficiency, and light use efficiency. The largest phenological and physiological differences between the prevailing and alternative cropping practices were observed for soybean during a growing season with an unusually high VPD. Soybean in the alternative system reached the green-up transition date two days sooner and stayed green one day longer providing three additional days of photosynthesis. At peak greenness, soybean grown in the alternative cropping system also had a 56 to 66 percent higher photosynthetic capacity (Vcmax25 and Jmax25), 62 percent higher gross primary productivity under saturating light conditions, 21 percent higher ecosystem quantum yield, and 15% higher water-use efficiency. These results indicate that alternative cropping practices may lengthen the growing period and improve the physiological status of crops in the northern Great Plains under conditions of high atmospheric evaporative demand.