Soybean Water Status and Canopy Microclimate Relationships at Four Row Spacings¹

Abstract

There is little field data relating plant water status and canopy microclimate of determinate soybean [Glycine max (L.) Merr.] cultivars grown in humid environments. Also, few observations of these parameters have been reported for the period prior to complete canopy closure. A field study was conducted in South Carolina in 1979 to determine these basic relationships for two determinate soybean cultivars, Davis (Group VI) and Coker 338 (Group VIII) grown in 1.02, 0.76, 0.51 and 0.36‐m row spacings. The experiments were conducted on a Norfolk loamy sand (fine‐loamy, siliceous, thermic, Typic Paleudult). Thermistor‐determined leaf temperatures (TL) and ambient temperatures (TA) were highly correlated, and no significant improvement in the correlation resulted from treating row spacing or diurnal periods separately. Both TL and ΔT (TL – TA) were highly correlated with pressure chamber determination of xylem pressure potential (ΨX). Parallel leaf diffusive resistance (R5) was not highly correlated with any of the canopy microclimate or water status parameters observed. Atmospheric vapor pressure deficit (VPD) was correlated with ΔT. Xylem pressure potential was very highly correlated with leaf vapor pressure deficit (LVPD). No row spacing effect on Ψx was observed, but mean seasonal midday Ψx was 0.10 MPa lower for Coker 338 than for Davis (P≤0.001) and osmotic potential was 0.20 MPa lower for Coker 338 than for Davis (P≤0.01). The authors propose that the slope of ΔT vs. VPD may be influenced by high prevailing relative humidity and heating of the canopy from exposed soil between rows in the period prior to complete canopy coverage.

Biostimulant Effect of Marine Macroalgae Bioextract on Pepper Grown in Greenhouse

“…The stomatal conductance (SC) was obtained according to the Ohm's law analogy, through the sum of SC in parallel of the two leaf surfaces, methodology used by Sharpe [15] and Sojka and Parsons [16] referring to the equation:…”

Development of integrated pest management techniques: Insect pest management on soybean

“…The soybean injury response to aphid feeding has been well described in wide-row soybean production , and it has been validated in subsequent studies . There still exists the possibility that an interaction could occur between soybean aphid populations and row spacing or plant yield and row spacing due to altered plant architecture (Legere and Schreiber 1989) and canopy microclimate (Sojka and Parsons 1983).…”

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Canopy temperature and yield relationships of water-deficit-stressed alfalfa

“…Other researchers who established a direct relationship between leaf temperature (Tl) and plant-water potential were Sojka and Parsons (1983) . A linear relationship of plant-water potential on leaf temperature for soybeans showed an r-squared of 0.838 over the course of a day.…”