Leaf and canopy stomatal resistance, aerodynamic resistance, and evapotranspiration of irrigated continuous no-till and disk-till maize

The impact of no-till (NT) management as compared with conventional tillage practices (e.g., disk till [DT]) on plant stomatal behavior in relation to model estimation of crop evapotranspiration (ETc) and plant physiological functions has not been sufficiently evaluated. This research investigated the effects of NT and DT management on maize (Zea mays L.) physiological parameters and ETc losses. We also tested the methodology to estimate ETc using a one-step Penman-Monteith (PM) model with measured variable resistance from scaled-up leaf stomatal resistance (R-L) to canopy resistance (R-C) with Bowen Ratio Energy Balance System (BREBS)-measured ETc. Photosynthetic photon flux density (PPFD) explained 76 and 79% of the variability in R-L for NT and DT maize, respectively, which varied with growth stage. Disk-till maize R-L was 29, 5, 25, and 4% higher than NT maize R-L during the vegetative, tasseling and silking, reproductive, and near-physiological-maturity stages, respectively. The seasonal average scaled-up R-C values for NT and DT maize were 102.4 and 128.6 s m(-1), respectively. The PM-estimated ETc correlated strongly with the BREBS-measured ETc, with the PM model estimates being 8 and 6% within the BREBS measurements on an hourly and daily basis, respectively. To the best of our knowledge, this research is the first to develop the response curves (PPFD vs. R-L) for maize for different growth stages under NT and DT. The analyses presented here can provide invaluable data and information for plant physiology research, crop modeling, determining crop response to different management, and environmental drivers.