Effect Of Soil Matric Potential Research Articles

Soybean Water Extraction, Leaf Water Potential, and Evapotranspiration During Drought1

AbstractSoil water is often the most limiting factor in soybean production in the southeastern US. To increase wateruse efficiency in soybean production, it is necessary to characterize the plant's response to the evaporative demand and to soil water stress when the root distribution changes with depth. ‘Davis’ and ‘McNair 800’ soybean cultivars (Glycine max (L.) Merr.) were grown in a field experiment conducted on Norfolk sandy loam (Thermic Typic Paleudults) to evaluate the effect of irrigation on soybean yields and to determine the combined effects of soil matric potential and evaporative demand on evape transpiration (ET) in nonirrigated and irrigated treatments. Water was applied to the irrigated treatment when the matric potential at the 15cm depth was −0.2 bar. Leaf water potential was measured using the pressure chamber technique and ET was measured using a portable chamber during a 34day drought. Only small differences in the midday leaf water potential were found between the two cultivars, whereas ET on the nonirrigated treatments was about two‐thirds of that on the irrigated treatments 25 and 32 days into the drought. Soil matric potential data indicated significant water extraction at the 153‐cm depth in the nonirrigated treatments near the end of the drought. The maximum incanopy air temperature during the drought in the nonirrigated Davis was 6.7 C higher than in the irrigated treatment. Irrigation resulted in a 351‐ and 364‐kg/ha increase in Davis and McNair 800, respectively. Even though the nonirrigated plants exhibited severe wilt symptoms during the drought, the results point out the importance of the root distribution and subsoil water in partially meeting the evaporative demand during drought.

Effect of Soil Matric Potential and Seeding Depth on Emergence of Barley1

AbstractAdequate crop stands resulting from vigorous seedling emergence is important for optimum crop production. Seedling emergence is usually influenced by soil water potential and seedling depth as well as other environmental factors. The effects of soil matric potential and seeding depth on emergence percent and rate of emergence of barley (Hordeum vulgare L.) were investigated. Seedling emergence of ‘Zarjo’ cultivar of barley was measured in a Calcixerollic Xerochrept soil at −0.6 to −30.0 bars soil matric potentials and at 2 to 12 cm seedling depths in the greenhouse. Cultivar response to seeding depth was determined by seedling emergence measurements of ‘Torsh’, Zarjo, and ‘Shaneii’ cultivars at seeding depths of 2 to 12 cm under the same experimental conditions. Soil matric potential of ‘30.0 bars reduced the seedling emergence of Zarjo and resulted in the lowest emergence rate. However, soil matric potentials of −0.6 and −1.5 bars also reduced Zarjo emergence at the 12‐cm seeding depth. Seedling emergence and emergence rate of Zarjo were lower at the 12 cm seeding depth at all levels of soil matric potentials. The emergence rate was also reduced at the 8‐cm seeding depth, but only at −30.0 bars. Seedling emergence of Shaneii was found to be lower than that of the Torsh and Zarjo cultivars. The rates of emergence of the cultivars were not greatly different at the various seeding depths.

Diurnal Fluctuation of Leaf‐water Potential of Corn as Influenced by Soil Matric Potential and Microclimate1

AbstractWater stress during critical growth periods is frequently the limiting factor in crop production. However few data are available on the variation of plant water status under field conditions. The object of this work was to quantify the effect of soil matric potential on plant water status. Sweet corn (Zea mays L.) was grown on a Varina sandy loam soil to determine the effect of the microclimate and irrigation on leaf water potential. Soil water stress was imposed naturally and by use of automated portable shelters that covered the plots during rainfall.Leaf‐water potential was closely related to the diurnal change of incoming energy. A maximum leaf‐water potential of −1.5 bars occurred just prior to sunrise. The minimum value, which occurred during the peak radiation load or stress, was dependent on soil matric potential and stage of plant development. Before tasseling, soil matric potentials of −0.08 and −0.60 bar at the 15‐cm depth in irrigated and nonirrigated plots resulted in minimal leaf‐water potentials of −12 and −18 bars, respectively. After tasseling, soil matric potentials were −0.07 bar at the 15‐cm depth in the irrigated and −3.0 bars in the nonirrigated plots, and the same minimal leaf‐water potential of −18 bars developed for both. Under the same radiation load, minimal leaf‐water potential of irrigated plants was −12 bars before tasseling and − 18 bars after tasseling. The results demonstrate the need to evaluate the influence of environmental stresses and soil water deficits on leaf‐water potential and associated physiological processes.

Comparison of the effects of soil matric potential and isotropic effective stress on the germination of Lactuca sativa

The matric potential contributes positively to the isotropic effective stress operating in the solid framework of a soil system. Collis-George and Hector (1966) suggested that the matric potential may influence seed germination through its contribution to the effective stress in the solid framework surrounding the seed. Experiments are described which separate the effects of matric potential on seed germination into those that can be attributed to the free energy of the soil water and those that can be attributed to the effective stress in the soil system. The results clearly indicate that (1) seed germination is influenced by the isotropic effective stress in the solid framework of the soil system, and (2) the influence of matric potential on seed germination in the range 0 to - 400cm of water can be wholly attributed to the isotropic effective stress in the solid framework and not to the free energy of the soil water as defined by the matric potential. These conclusions are discussed in terms of the behaviour of other organisms in response to an applied matric potential.