Antecedent soil water content and vapor pressure deficit interactively control water potential in Larrea tridentata

Abstract. The possible effects of broadleaved woodland on recharge to the UK Chalk aquifer have led to a study of evaporation and transpiration from beech woodland (Black Wood) and pasture (Bridgets Farm), growing in shallow soils above chalk in Hampshire. Eddy correlation measurements of energy balance components above both the forest and the grassland enabled calculation of latent heat flux (evaporation and transpiration) as a residual. Comparative measurements of soil water content and soil water potential in 9 m profiles under both forest and grassland found changes in soil water content down to 6 m at both sites; however, the soil water potential measurements showed upward movement of water only above a depth of about 2 m. Below this depth, water continued to drain and the soil water potential measurements showed downward movement of water at both sites, notwithstanding significant negative soil water potentials in the chalk and soil above. Seasonal differences occur in the soil water content profiles under broadleaved woodland and grass. Before the woodland foliage emerges, greater drying beneath the grassland is offset in late spring and early summer by increased drying under the forest. Yet, when the change in soil water profiles is at a maximum, in late summer, the profiles below woodland and grass are very similar. A comparison of soil water balances for Black Wood and Bridgets Farm using changes in soil water contents, local rainfall and evaporation measured by the energy balance approach allowed drainage to be calculated at each site. Although seasonal differences occurred, the difference in cumulative drainage below broadleaved woodland and grass was small.

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Relationships Among Water Potential Components, Relative Water Content, and Stomatal Resistance of Field-Grown Peanut Leaves1

Peanut Science ◽

10.3146/i0095-3679-11-1-10 ◽

1984 ◽

Vol 11 (1) ◽

pp. 31-35 ◽

Cited By ~ 12

Author(s):

J. M. Bennett ◽

K. J. Boote ◽

L. C. Hammond

Keyword(s):

Water Potential ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Leaf Water Potential ◽

Relative Water Content ◽

Leaf Water ◽

Peanut Crop ◽

Relative Water ◽

Volumetric Soil Water

Abstract Limited data exist describing the physiological responses of peanut (Arachis hypogaea L.) plants to tissue water deficits. Detailed field experiments which accurately define the water status of both the plant and soil are required to better understand the effects of water stress on a peanut crop. The objectives of the present study were 1) to describe the changes in leaf water potential components during a drying cycle, and 2) to define the relationships among soil water content, leaf water potential, leaf turgor potential, relative water content, leaf-air temperature differential, and leaf diffusive resistance as water stress was imposed on a peanut crop. During a 28-day drying period where both rainfall and irrigation were withheld from peanut plants, midday measurements of the physiological parameters and volumetric soil water contents were taken concurrently. As soil drying progressed, water extraction from the upper soil depths was limited as soil moisture approached 0.04 m3m-3. Leaf water potentials and leaf turgor potentials of nonirrigated plants decreased to approximately −2.0 and 0 MPa, respectively, by the end of the experimental period. Leaf water potentials declined only gradually as the average volumetric soil water content in the upper 90 cm of soil decreased from 0.12 to 0.04 m3m-3. Further reductions in soil water content caused large reductions in leaf water potential. As volumetric soil moisture content decreased slightly below 0.04 m3m-3 in the upper 90 cm, leaf relative water content dropped to 86%, leaf water potential approached −1.6 MPa and leaf turgor potential decreased to 0 MPa. Concurrently, stomatal closure resulted and leaf temperature increased above air temperature. Osmotic potentials measured at 100% relative water content were similar for irrigated and nonirrigated plants, suggesting little or no osmotic regulation.

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Soil water potential during different phenological phases of coffee irrigated by center pivot

Engenharia Agrícola ◽

10.1590/s0100-69162013000200006 ◽

2013 ◽

Vol 33 (2) ◽

pp. 269-278 ◽

Cited By ~ 1

Author(s):

Adão W. P. Evangelista ◽

Luiz A. Lima ◽

Antônio C. da Silva ◽

Carla de P. Martins ◽

Moisés S. Ribeiro

Keyword(s):

Water Potential ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Irrigation Management ◽

Soil Water Potential ◽

Field Capacity ◽

Limiting Factor ◽

Center Pivot ◽

Phenological Phases

Irrigation management can be established, considering the soil water potential, as the limiting factor for plant growth, assuming the soil water content between the field capacity and the permanent wilting point as available water for crops. Thus, the aim of this study was to establish the soil water potential interval during four different phenological phases of coffee irrigated by center pivot. The experiment was set at the experimental area of the Engineering Department at the Federal University of Lavras, in Brazil. The coffee variety planted is designated as Rubi, planted 0.8 meters apart, with rows spaced 3.5 meters apart. The treatments corresponded to the water depths applied based on different percentages of Kc and reference evapotranspiration (ET0) values. Sensors were used to measure the soil water potential interval, installed 25 centimeters depth. In order to compare the results, it was considered as the best matric potential the one that was balanced with the soil water content that resulted in the largest coffee productivity. Based on the obtained results, we verified that in the phases of fruit expansion and ripening, the best results were obtained, before the irrigations, when the soil water potential values reached -35 and -38 kPa, respectively. And in the flowering, small green and fruit expansion phases, when the values reached -31 and -32 kPa, respectively.

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Growth and yield of rice cultivars under sprinkler irrigation in south-eastern Queensland. 3. Water extraction and plant water relations dash comparison with maize and grain sorghum

Australian Journal of Experimental Agriculture ◽

10.1071/ea9880249 ◽

1988 ◽

Vol 28 (2) ◽

pp. 249 ◽

Cited By ~ 14

Author(s):

S Fukai ◽

P Inthapan

Keyword(s):

Water Potential ◽

Water Content ◽

Soil Water ◽

Soil Water Content ◽

Leaf Water Potential ◽

Osmotic Potential ◽

Root Length ◽

Dry Matter ◽

Root Length Density ◽

Leaf Water

Several physiological responses were compared, under irrigated and water-stressed conditions, in an attempt to explain the reasons for the greater reduction in dry matter production of rice compared with maize and sorghum in a water-limiting environment. Leaf water potential and leaf rolling were determined weekly, soil water profiles and root length density twice, and leaf osmotic potential once during a long dry period. Root length density of rice was at least as high as that of maize and sorghum in the top 0.6 m layer of soil in both the wet and dry trials. There was no difference in water extraction among the 3 species from this layer, while rice extracted less water than did the other species from below 0.6 m. High variability among replicates precluded any conclusion being drawn regarding root length in the deeper layer. Leaf water potential, measured in the early afternoon, was consistently lower in rice than in maize and sorghum, even when soil water content was high, indicating high internal resistance to the flow of water in the rice plants. The low leaf water potential in rice was accompanied by low osmotic potential, and this assisted in maintenance of turgor and dry matter growth when soil water content was relatively high. As soil water content decreased, however, leaf water potential became very low (less than - 2.5 MPa) and, for rice, leaves rolled tightly.

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