Soil Water Uptake Research Articles

Transpiration and Soil Water Usage by Oat as Affected by Postemergence Herbicides

AbstractChanges in transpiration of plants as influenced by herbicides may or may not significantly affect soil water uptake in the field. We compared effects of the relatively new herbicides fluazifop [(±)‐butyl‐2‐(4‐{[5‐(trifuoromethyl)‐2‐pyridinyl]oxy}phenoxy)propanoate], haloxyfop [methyl‐2‐(4‐{[3‐chloro‐5‐(trifluoromethyl)‐2‐pyridinyl]oxy}phenoxy)propanoate], and sethoxydim {2‐[1‐(ethoxyimino)butyl]‐5‐2[2‐(ethylthio)propyl]‐3‐hydroxy‐2‐cyclohexen‐1‐one} applied at various rates to oat (Avena sativa L.) at the 5‐ to 6‐cm stage on transpiration, soil water use, and plant development. In controlled environments, transpiration rates in oat declined about 6 d after herbicide treatment. Time for and the degree of transpiration reduction were herbicide and herbicide‐rate dependent, as were the reductions in plant weight and leaf number. First reductions in soil moisture under laboratory conditions were found 10 d after treatment of oat with fluazifop and haloxyfop and 12 d after treatment with sethoxydim. Similarly, in the field fluazifop treatment required 9 d and haloxyfop and sethoxydim 11 d before significant differences in soil moisture occurred. The correlation coefficient of soil matric potential and dry weight of oat in the field was −0.89 and −0.90, respectively, for 2 yr, 1984 and 1985. Reduction of oat dry matter and soil water use in the field was also herbicide rate dependent.

WATER UPTAKE BY ROOTS IN CRACKS AND WATER MOVEMENT IN CLAYEY SUBSOIL

We evaluated the magnitude of soil water uptake by roots growing in cracks, using a simple crack model, and compared it with upward soil water flux in a clayey soil. The physical quantities used in the model are crack spacing (D), depth of the cracks (H), water uptake rate per unit length of root (q), and root length density in the cracks (L). These values, except for q, were obtained from an upland field converted from a paddy field. Daily water uptakes per unit of ground surface by the model were 0.7–1.3 mm d−1 when q was 0.01–0.02 cm3. cm−1.d−1 and D was 15 cm, whereas, upward soil water fluxes calculated by hydraulic conductivities and soil water pressures were of the order of 0.01 mm.d−1 1 wk after a heavy rain (143 mm). Roots growing in the subsoil through the cracks, therefore, are very important for water consumption by crops.

Experimental Test of a Model of Water Uptake by Soybean1

AbstractMechanistic models of soil water uptake have differed in the form of the water uptake term of Richard's equation. One of the most widely used uptake terms is that proposed by Hillel et al., although a detailed study comparing predicted soil water contents with those observed experimentally has been lacking. The purpose of this work was to develop a model that would test the accuracy of this water uptake term on a seasonal basis at various levels of water stress. Simulated soil water contents were compared with water contents observed biweekly in a 3‐yr field experiment that included three moisture treatments: irrigated, normal rainfall, and plastic covered. When a longitudinal resistance was included, 69 to 88% of the predicted soil water contents fell within the 95% confidence limits of the observed values from the irrigated and normal rainfall treatments in 3 yr. In the plastic‐covered treatment, however, only 17 to 49% of the predicted water contents were within the confidence limits. We conclude that the uptake term is accurate under normal and well watered conditions, but not under severe water‐stress conditions. Sensitivity analysis showed that the model was sensitive to net radiation, LAI, and rainfall and insensitive to hydraulic conductivity and root density.

Water balance and pattern of soil water uptake in a peach orchard

Five-year-old peach trees were irrigated at 50% and 100% of calculated maximum evapotranspiration (MET) in order to determine the influence of water stress on the pattern of water uptake from the soil and on the actual evapotranspiration (AET) of the crop. A simplified water balance method based on the relationship between the drainage component and the soil water content averaged over the soil profile has been used to estimate AET from periodic neutron probe measurements. Maximum water uptake is from the upper 60 cm of soil when trees are well-watered. Decreased soil water content induces a shift in the soil water uptake towards deeper layers, which can be due either to upward fluxes of water or to an increased water uptake by deeper roots. AET in the 50% MET regime is reduced from July to September, compared to the 100% MET regime, partly because of stomatal closure. There is no drainage in the 50% MET treatment from June to September; it is about 1 mm day −1 in the 100% MET regime until the end of August and ceases in September when the soil dries.

The relative sensitivity of spring barley, spring field beans and sugar beet crops to soil compaction

Abstract The sensitivity of sugar beet ( Beta vulgaris , cv. Monoire), spring barley ( Hordeum disticon , cv. Carnival) and field beans ( Vicia faba , cv. Maris Bead) to topsoil compaction induced by tractor wheelings post sowing was investigated on a coarse gravelly sandy loam of the Arrow series in 1983. Compaction reduced leaf area and dry matter accumulation in sugar beet and field beans. Plant population was only reduced in sugar beet, which largely accounted for a yield reduction of 59%. Compaction did not affect the yield of spring barley but reduced the yield of field beans by 26%. The total length and distribution of roots in the soil profile was reduced by topsoil compaction in all crops: sugar beet (49%), field beans (28%) and spring barley (27%). However the reduced root length of spring barley was an order of magnitude greater than that of the other crops. Compaction did not affect tap root development of the field bean or total root dry matter. The rate of soil water uptake, depth of soil water extraction and crop transpiration were reduced by topsoil compaction in sugar beet and field beans but leaf water potential was not affected. It is suggested plants adapt to adverse soil physical conditions by reduction of leaf area expansion rather than by lowered leaf water potential, and hence stomatal conductance.

Effect of water stress on leaf and root growth, and water uptake ofGmelina arborea ROXB. seedlings

Young seedlings ofGmelina arborea Roxb. were subjected to 2 weeks of drought. Despite the gradual reduction in stomatal conductance, leaf and root growth was not affected until the later part of the stress period. This was attributed to solute adjustment in the roots of the plants. As the severity of water stress increased, root growth was prolific in all the soil segments. As a result, water in the lowest soil segment was used to maintain plant turgor, which in turn sustains the leaf and root growth during the water-stress treatment. The influence of soil water content and soil water potential upon soil water uptake rate was also evaluated on soil profile basis. Rates of extraction began to decline in all soil segments as soon as soil water potential fell below -0.06 MPa, presumably as a result of vapour gaps between the root and soil (root: soil interface resistance). It is suggested that the growth of roots ofGmelina plants away from drying soil will minimize the resistance to water uptake.

Interactions between seedlings of Chrysanthemoides monilifera and Acacia longifolia

Abstract Displacement of Acacia longifolia on coastal dunes in New South Wales by the invasive species Chrysanthemoides monilifera may be linked to the greater competitiveness by the latter in the seedling stage, as demonstrated in pot experiments. This occurs despite a lower chlorophyll concentration in shoots of C. monilifera which leads to a lower assimilation rate per unit leaf area and lower carbohydrate concentrations. However, this assimilate is spread over a greater total leaf area. Such a strategy associated with‘quantity’may thus be more important than leaf‘quality’in terms of competitiveness. In A. longifolia, the production of higher quality‘leaves’but of lower total area may be well‐suited in the often sparse native populations found in sand dunes, but appears disadvantageous when seedlings of C. monilifera also co‐exist. The competitive advantage of C. monilifera over A. longifolia is reduced but not reversed under water stress. Under severe stress, mortality of C. monilifera is greater than that of A. longifolia in monocultures but mortality of both species is similar in mixtures. The reason appears to be that C. monilifera transpires more water per plant even though its rate of transpiration per unit leaf area is reduced under water stress because of early stomatal closure. In mixtures, faster root growth of C. monilifera ensures faster uptake of the available soil water, thus minimizing the inherent advantage in A. longifolia of its lower water use and greater efficiency.

Uptake of Interstitial Water from Soil: Mechanisms and Ecological Significance in the Ghost Crab Ocypode quadrata and Two Gecarcinid Land Crabs

Mechanisms by which terrestrial crabs take up interstitial water from soil, limiting conditions and rates of uptake, and their ecological relevance in nature were examined in the ghost crab Ocypode quadrata. Comparisons were made with two species of land crabs (Gecarcinus lateralis and Cardisoma guanhumi). Rapid rehydration, by bulk uptake of water, occurs in desiccated individuals of all three species when sufficient moisture is present in soil, regardless of osmotic gradient. Slow rehydration from hypoosmotic soil moisture also occurs, particularly in G. lateralis, even when the water content is below the threshold for bulk uptake. Ocypode quadrata has the lowest threshold (<5% water) for bulk uptake from damp sand. Water is collected from soil spaces by capillary tufts of setae, drawn into the gill chamber by suction up to 76 mm Hg, and at least some of it passed to the mouth and swallowed. This mechanism provides water ad lib. anywhere the water table lies near the surface of sandy soil. The highly terrestrial land crab G. lateralis is less capable of producing suction and of extracting soil water in bulk. In this crab's natural habitat, burrow soil never contains sufficient water for bulk uptake to contribute significantly to water balance, although gradual "osmotic uptake" may be important. Cardisoma guanhumi, whose burrows contain a pool of water, presumably need not rely on uptake of soil water. Nevertheless, it possesses structures similar to, and soil-water extraction capabilities superior to, those of G. lateralis. The great terrestriality of the land crabs, particularly G. lateralis, cannot be attributed to highly developed mechanisms for taking up bulk water from soil. These species meet the challenge of water balance on land by relying on conservation, while ghost crabs emphasize water uptake.

A comparison of irrigated maize growth in southern New South Wales on sites with and without a preceding fallow

This experiment was carried out on a grey cracking clay soil near Griffith in southern New South Wales. Maize grown after a two year fallow produced 2.7 t/ha or 45% more grain than maize grown on a continuously cropped site. This difference occurred despite large fertilizer inputs and similar management procedures. The yield differences resulted from increased plant establishment (20%),kernel numbers per cob (26%), and kernel size (11%) in the fallow area. However, experimental results were mostly inconsistent with our initial hypothesis that restricted root growth and soil water uptake were limiting yields on continuously cropped sites. Water use was measured throughout the season with a neutron probe, but no differences in depth or amount of soil water extraction were detected. Root length density and leaf water potential measurements indicated that plant water relations were similar for the two sites and so this did not seem to account for the improved yield from the fallowed site.

Analysis of soil-water uptake from a drying loess soil by an oat crop using a simulation model

A simulation model of water uptake by a crop was developed to facilitate synthesis of field and laboratory observations with existing knowledge, and to analyze and predict affects of management practices, such as tillage, on water uptake from a drying soil. Radial water flow resistance in soil Rs was estimated by the single root flow model. Leaf stomata closure was represented by an observed minimal leaf water potential. Flow resistances, per unit root length Rr and in the plant Rp, were assumed to be constant and were evaluated together with an effective root length factor Frl, in the course of simulating a ten week period of observed soil water depletion by a crop of oats. Rr, Rp, and Frl were found to have similar values to those reported in the literature. Potential transpiration and evaporation and their ratio were estimated by the methods of Van Bavel (1966) and Denmead (1973). Evaporation reduction due to soil drying was estimated empirically.

ANALYSIS OF A DIFFUSION MODEL FOR PLANT ROOT GROWTH AND AN APPLICATION TO PLANT SOIL-WATER UPTAKE

ABSTRACTThis paper considers the problem of modeling crop root growth and soil-water uptake. The development of the plant root is modeled with a nonlinear diffusion equation. Root growth data for corn are used to evaluate the suitability of the model and to estimate the root diffusivity, which is in

Etude comparative de quatre dispositifs d'irrigation automatique: Application au mais irrigue en localise

On five plots under maize cultivation, each 1000 m 2 in area, comparison was made between four automatic irrigation methods. In three of the methods, the irrigation schedule depended upon gauges (tensiometers or electrical resistance probes) inserted in the cropped soil; the fourth method used a Class “A” evaporation pan; the fifth plot was irrigated in accordance with mean potential evapotranspiration. Both soil water uptake and plant growth were studied. The results indicated that tensiometer scheduling saved 30% of the irrigation water without any significant decrease in yield. On the other hand, with the commercial electrical resistance probes, the watering was not well suited to the plant needs and led to a 25% decrease in yield.

Relationship between Root Distribution of Upland Crops and their Yield : IV. Soil water uptake pattern in upland rice under different soil moisture levels

The field experiments were conducted during summer in 1978 and 1979 on a field of volcanic ash soil at Kitamoto to improve a method determining the soil water uptake patterns by field crops. The amount of the evapotranspiration in upland rice was measured by the chamber method developed by KATO et al. after cutting roots horizontally by piano wire at 15, 20 and 30 cm in depth, respectively, for three soil moisture levels controlled by irrigation just before treatment. The main results obtained are as follows: 1. When soil moisture was kept at low level of pF 2.0-2.3, the cutting roots at 20 and 30 cm in depth was not effective for the evapotranspiration in case of the rate less than 0.9 mm per hour. 2. When soil moisture was kept at pF 2.8, the results obtained by cutting roots at 15 cm in depth was the same as shown in item 1. 3. Under the condition of 42% soil moisture in surface soil, the evapotranspiration of treated plot decreased to 60% of the controlled one and wilted in daytime. 4. It was suggested from these results that upland rice grew mainly by water in the layer of 0-20 cm if the moisture was at low (pF1 2.0-2.3), but, when evapotranspiration rate got higher than 0.9 mm per hour even the moisture of surface soil was kept at low level (pF 2.0-2.3) or moisture of surface soil was less than 42%, the roots above 15 cm in depth did not uptake soil water enough to support the normal evapotranspiration.

Simulation of Soil Water within the Root Zone of a Corn Crop1

AbstractKnowledge of the distribution and movement of soil water in the root zone of a row crop is important in farm and watershed management, and in research on the transport of soil nutrients and pollutants. The objective of this study was to develop a model that would calculate the infiltration, evaporation, transpiration, and deep drainage of soil water in the root zone of a corn (Zea mays L.) crop throughout a growing season, using readily obtainable climatic data as daily inputs. The model differed from existing models in that the effect on the distribution of rainwater due to channeling in the cracks and non‐capillary pores of a highly structured soil was considered. This distribution was obtained by adapting equations used to describe analagous distributions in ion exchange chromatography. Two methods of modeling plant uptake of soil water were compared. An empirical approach assumed that the plant took water from the layer in the root zone with the lowest energy level (determined four times daily) and the amount taken was given by a curve that related the ratio of actual and potential transpiration to the water content at that level. A mechanistic approach, similar to that used by Nimah and Hanks in 1973, considered root distribution, hydraulic conductivities, plant resistance, and root‐soil contact resistance.The model was tested using seasonal soil moisture records from 4 years on one soil and a single year on a second soil. Mean squared error of prediction for the seasons ranged from 0.05 to 0.15%. Use of the partial displacement infiltration component improved the accuracy of the results in all but one trial. The two methods of modeling plant uptake of soil water, mechanistic and empirical, differed very little in accuracy.

Effect of Tillage on Soil‐Water Movement During Corn Growth

AbstractThe occurrence of drought during the growing season often limits the amount of soil water available for plant growth. The availability of soil water can further be limited if a hard layer exists not too far below the soil surface. Field experiments were therefore conducted on a Cahaba sandy loam soil (Typic Hapludult) to determine the effect of tillage practices on soil water movement during corn (Zea mays L.) growth. Four tillage practices, viz., conventional‐tillage‐without‐subsoiling, conventional‐tillage‐with‐subsoiling, no‐tillage‐without‐subsoiling, and no‐tillage‐with‐subsoiling, were studied on a soil with a plow plan. Soil water contents and soil water pressure heads were measured with a neutron probe and tensiometers, respectively. Water extraction by roots was determined by application of the integral form of the general transport equation for soil water. Soil water movement and water uptake were less for the conventional‐tillage‐without‐subsoiling treatment than for the other treatments. The two subsoiled treatments and the no‐tillage‐without‐subsoiling treatment indicated root penetration and soil‐water uptake below 50 cm.When soil water uptake patterns were compared with corn yield on a weight‐per‐ear basis, there was a direct, positive correlation between the amount of water taken up by the corn plants and corn yield.

FIELD WATER BALANCE AND SIMULATED WATER RELATIONS OF PRAIRIE AND OAK-HICKORY VEGETATION ON DECIDUOUS FOREST SOILS

A steady-state model of atmosphere-soil-plant water relations, implementing both the combined energy balance, aerodynamic calculation of evapotranspiration and a five-layer Darcy soil-water flow system, was used to simulate on a daily basis the water status and budget of experimental plots with either prairie grass or oak forest vegetation. A field water balance study provided independent estimates of evapotranspiration and drainage, based on measurements of soil water at several depths during the growing season. Oak forest and prairie grass vegetation in southern Wisconsin showed an average evapotranspiration rate of 2.0 cm3cm-2 week-1 from mid-June to early October based on a water balance of the top 180 cm of soil. Simulation results were in close agreement with the field estimates, although differences in time distribution were shown, particularly for the prairie grass plots. Actual evapotranspiration would be greater than these results due to soil water uptake at depths below 180 cm. Soil water drainage was negligible during most of the growing season for vegetated plots whereas drainage from treatments without vegetation was slightly less than the precipitation received. Soil water content was generally lower on vegetated plots than on nonvegetated plots during the growing season. The model provided a means of evaluating some phenomena not measured in the field experiments. Simulations suggested that the oak vegetation was under water stress on more days during the growing season than the prairie grass.

Uptake of soil capillary water by ghost crabs

SEVERAL semiterrestrial crabs, including some ghost crabs (genus Ocypode) can extract interstitial water from damp sand1–3. This enables them to offset their high evaporative losses even in habitats lacking surface water. The mechanism involved has remained unknown, although there have been a few observations of how Gecarcinus lateralis takes up droplets of water applied to its venter4. I have found that uptake of soil water by Ocypode quadrata, the common ghost crab of Caribbean and temperate Atlantic North American beaches, is accomplished by a mechanism involving capillary attraction and the production of a substantial vacuum.

Soil Water Uptake by Alfalfa1

AbstractWater uptake patterns of alfalfa (Medicago sativa L.) assist us in understanding proposed models governing plant water uptake. The data in this paper are presented to elucidate some details of passive water uptake from profiles with nonuniform soil water distributions. Soil water content under an alfalfa seed crop was monitored with a neutron moisture probe. Alfalfa roots withdraw soil water in the lower portion of the root zone (where soil matric potentials were between −7 and −10 bars), while the upper portion of the profile was above −2 bars. This indicates that for passive water uptake to occur, large water potential differences must exist between the root xylem and the soil in the upper, moist portion of the profile. Plant water potential measurements support passive uptake.

Diurnal and Seasonal Soil Water Uptake and Flux within a Bermudagrass Root Zone

AbstractDiurnal water movement within a bermudagrass [Cynodon dactylon (L.) Pers.] root zone and the uptake of water by the roots was studied in a field plot. A fast response tensiometer‐pressure‐transducer system was used to measure the hydraulic heads. The relations of pressure head to water content and to hydraulic conductivity were determined in situ. Diurnal water content and soil water flux profiles were derived by using the established hydraulic properties. The fast response tensiometer system enabled calculation of flux and water content changes over 2‐hour intervals. Diurnal water extraction rates calculated for different depths and times during the growing season yielded evapotranspiration rates that agreed well with rates measured on similar days in previous years using a lysimeter.

EFFECTS OF SOIL WATER MOVEMENT ON ACTUAL EVAPOTRANSPIRATION ESTIMATED FROM THE SOIL MOISTURE BUDGET

Actual evapotranspiration was estimated from the soil moisture budget for a grass-covered sandy loam soil at Simcoe, Ontario. Soil moisture was measured at 25 sites distributed over a 6-meter-square grid. The coefficient of variation for actual evapotranspiration estimated at all sites averaged 13% and rose as high as 19%. Average actual evapotranspiration exceeded both the Penman and Thornthwaite estimates of potential evapotranspiration for three of the six measuring intervals, due to deep seepage losses. The application of corrections for the vertical water movement, determined from experimentally derived matric suction and hydraulic conductivity data, gave a substantial deep seepage loss for some periods and a capillary uptake of soil water for others. Vertical losses and gains created errors of up to + 28 and − 29%, respectively, in the standard estimates of actual evapotranspiration. The large spatial variations in evapotranspiration estimates resulted from variations in volumetric soil moisture between sample points, apparently creating differences in the magnitude and direction of vertical water movement across the terminal depth. The horizontal flux of water between measuring points was relatively unimportant in accounting for the spatial variations.