Contrasting Physiological and Environmental Controls of Evapotranspiration over Kernza Perennial Crop, Annual Crops, and C4 and Mixed C3/C4 Grasslands

Abstract

Perennial grain crops have been suggested as a more sustainable alternative to annual crops. Yet their water use and how they are impacted by environmental conditions have been seldom compared to those of annual crops and grasslands. Here, we identify the dominant mechanisms driving evapotranspiration (ET), and how they change with environmental conditions in a perennial Kernza crop (US-KLS), an annual crop field (US-ARM), a C4 grassland (US-KON), and a mixed C3/C4 grassland (US-KFS) in the Central US. More specifically, we have utilized the omega (Ω) decoupling factor, which reflects the dominant mechanisms responsible for the evapotranspiration (ET) of the canopy. Our results showed that the US-ARM site was the most coupled with the lowest decoupling values. We also observed differences in coupling mechanism variables, showing more sensitivity to the water fluctuation variables as opposed to the radiative flux variables. All of the sites showed their lowest Ω value in 2012, the year of the severe drought in the Central US. The 2012 results further indicate the dependence on the water fluctuation variables. This was especially true with the perennial Kernza crop, which displayed much higher soil moisture values. In this regard, we believe that the ability of perennial Kernza to resist water stress and retain higher soil moisture values is both a result of its deeper roots, in addition to its higher Ω value. Through the analysis of both the site comparison and the comparison of the differences in years, we conclude that the perennial Kernza crop (US-KLS) is more similar in its microclimate effects to the C4 (US-KON) and mixed C3/C4 (US-KFS) grassland sites as opposed to its annual counterpart (US-ARM). This has implications for the role of perennial agriculture for addressing agricultural resilience under changing climate conditions.

Responses in the Coupling of Carbon and Water Vapor Exchanges of Irrigated and Rainfed Andean Potato (<i>Solanum Tuberosum</i> Subsp. Andigenum) Agroecosystems

“…At the RF site, the VPD > 0.6 kPa indicates that the potato canopy experienced a larger saturation deficit and, as soon as VPD increased, Ra decreased, and Rc increased as the day progressed. The increase of midday Rc was up to 13 times larger than Rc at the FI site when the VPD increased around 0.8 kPa, revealing that under drought conditions, the plants increased the canopy resistance in response to high VPD (Aires et al, 2008;J D N Alves et al, 2022;Silva et al, 2017;Sutherlin et al, 2019b). Diurnal ET and GPP fluxes were highly restricted in all growth stages suggesting that in potatoes VPD could play a strong role in controlling GPP and ET by means of Rc (Aires et al, 2008).…”

“…At the DI site, Rc and Ra were similar to those found in the FI site. Despite water deficit events, Ra>Rc indicating that ET remains controlled by Ra and less by Rc and water content in the soil (Sutherlin et al, 2019a). Consequently, canopy was less capable to reduce evapotranspiration and avoid water losses (Spinelli et al, 2018a;Fereres and Soriano, 2007;Spinelli et al, 2018b), and ET continues at a high rate while there was a high restriction in the GPP and NEE fluxes.…”

The use of wheatgrass (<i>Thinopyrum intermedium</i>) in breeding

“…In comparison with annual crops such as maize and wheat, the variety Кеrnza also had a higher ability of maintaining the wateruse efficiency (WUE) and evapotranspiration (ET) -about 97 % throughout the whole growing season. This was achieved thanks to a strong root system and water uptake from deeper soil layers, which is an important mechanism of adaptation to water deficit conditions (Suyker, Verma, 2009;Abraha et al, 2015;Sutherlin et al, 2019).…”

Introducing Perennial Grain in Grain Crops Rotation: The Role of Rooting Pattern in Soil Quality Management

“…Its contribution to soil nitrogen accumulation may turn out to be substantial in the medium term (>2-3 years) as root litter inputs should increase with time, or following crop destruction, resulting in massive root litter inputs [78]. However, prior to crop destruction, the increased soil colonization of subsoil layers can be useful to mine leached nutrients, as well as to capture groundwater in times of water shortage [9,79,80]. The greater soil exploration and water capture allowed by perennials may, however, result first in mitigating yields variability and improve resiliency rather than increasing grain yields [11,81] due to the high root-shoot ratio and the low grain harvest index.…”