Click on image to view larger version.
Fig. 1. Soil matric potential (
M) for a 0.9-m soil profile of a Trix clay loam vs. day after 50% emergence (DAE) (i.e., calendar date same as DAE) for the (a) 1993 and (c) 1994 growing seasons. Symbols in legend for panels (a) and (c) refer to Control-Dry (CD), FACE-Dry (FD), Control-Wet, and FACE-Wet (FW) treatments (Control at 370 µmol CO2 mol–1 and FACE at 550 µmol CO2 mol–1; Dry at 50% and Wet at 100% replacement of evapotranspiration). Vertical dashed lines in panels (a) and (c) separate four individual soil dehydration cycles by development stages as follows: (1) seedling development, tillering, and stem elongation (DAE 1–71 during 1993; DAE 1–76 during 1994); (2) inflorescence emergence (DAE 72–85 during 1993; DAE 77–88 during 1994); (3) anthesis (DAE 86–103 during 1993; DAE 89–111 during 1994); and (4) grain filling through physiological maturity (DAE 104–136 during 1993; DAE 112–137 during 1994). Symbols in legend given in panel (b) refer to drip-tape irrigation for Dry and Wet treatments, rainfall amounts, and N fertilizer application dates during (b) 1993 and (d) 1994. 
Amount of fertilizer (kg N ha–1) applied is given in parenthesis above irrigation histograms at tillering, inflorescence emergence, and anthesis for (b) 1993 and (d) 1994. Cumulative distribution curves (Cum.) denoting the amount of water (drip-tape irrigation + rainfall) given by right-most y intercept for Dry and Wet treatments in panels (b) and (d). Onset of the differential irrigation denoted by separation in Cum. curves on 1 Mar. 1993 (DAE 60) in panel (b) and 20 Jan. 1994 (DAE 20) in panel (d). Up-pointing arrows in panels (b) and (d) denote DAE when gas exchange, water relation, and leaf tissue carbohydrate concentration measurements were measured, whereas parenthesis below up-pointing arrows denote number of days between measurement dates and the last irrigated for (Dry:Wet) treatments. 
Letters e through j in legend of panel (c) denote DAE and number of days between measurement dates and last irrigated for (Dry:Wet) treatments during the third (e, f) and fourth (g, h, i, and j) soil dehydration cycles when standard thermocouple psychometric techniques were employed to measure leaf total water and osmotic potentials during 1994. Given on the right-most y axis are the sources of variance in ANOVA, which include carbon dioxide (C) for main plot, irrigation (I) for split-plot, and C x I interaction effects in a strip-split-plot experimental design. Significance effects given within soil dehydration cycle as *, **, ***, and ns for P
0.05, P 0.01, P 0.001, and not significant, respectively. (ne for effect not estimated); actual probability of a greater F statistic by chance reported if P 
0.10 and P 0.25 
P 0.10. Each mean datum was derived from four replications (i.e., means based on n = 4, SE of replication means based on n = 4).
