A new procedure to determine soil water availability

Soil Research ◽  
2001 ◽  
Vol 39 (3) ◽  
pp. 577 ◽  
Author(s):  
P. H. Groenevelt ◽  
C. D. Grant ◽  
S. Semetsa
Keyword(s):  
Root Zone ◽  
Matric Potential ◽  
Overburden Pressure ◽  
Weighting Functions ◽  
Swelling Soils ◽  
Water Capacity ◽  
Available Water ◽  
Physical Limitations ◽  
Plant Available Water ◽  
Least Limiting Water Range

The integral water capacity is first introduced as a flexible method to quantify various soil physical limitations when calculating available water in non-swelling soils. ‘Weighting’ functions that account for hydraulic conductivity, aeration, and soil resistance to penetration are applied to the wet and dry ends of the differential water capacity, and then integration is performed. The concept is extended to swelling soils by applying the theory of Groenevelt and Bolt (1972), which enables overburden pressures to be taken into account. A set of shrinkage lines measured by Talsma (1977) is analysed using this theory, which enables precise values of overburden potentials to be calculated as a function of the moisture ratio for different load pressures. The addition of the overburden potential to the unloaded matric potential causes minor shifts in the classical limits of plant-available water (viz. –1/3 bar and –15 bar). However, when other soil physical restrictions are taken into account (such as in the concept of the least limiting water range), the consequence for available water deeper in the root-zone (due to an overburden pressure) is far more serious. This is primarily because the matric potential at which aeration begins to be satisfied shifts to a considerably lower value, making a large quantity of water at the wet end no longer available. Examples of weighting functions derived from the literature are applied and their implications for available water in swelling soils are discussed.

Revisiting the wet and dry ends of soil integral water capacity using soil and plant properties

Soil Research ◽  
2018 ◽  
Vol 56 (4) ◽  
pp. 331 ◽  
Author(s):  
Fatemeh Meskini-Vishkaee ◽  
Mohammad Hossein Mohammadi ◽  
Mohammad Reza Neyshabouri
Keyword(s):  
Experimental Data ◽  
Sandy Loam ◽  
Limiting Factors ◽  
Clay Loam ◽  
Water Capacity ◽  
Available Water ◽  
Physiological Properties ◽  
Physical Limitations ◽  
Plant Available Water ◽  
Plant Properties

The integral water capacity (IWC) approach takes into account various soil physical limitations for calculating plant available water. However, the IWC approach cannot distinguish the differences in water uptake between various plants. Therefore, the objectives of this study were i) to modify the approach to include plant physiological properties to redefine the wet and dry ends of the IWC, called IWCplant and ii) to evaluate the performance of the IWCplant approach using experimental data. The restrictions imposed by poor soil aeration and rapid drainage flux were calculated using both soil and plant properties to modify the wet end of the IWC. The soil hydraulic resistance was considered to redefine the dry end of the IWCplant. Based on these approaches, physically meaningful weighting functions were developed for three proposed limiting factors at both ends of the wet and dry ranges of soil. Experimental data were obtained from a greenhouse trial with wheat and canola plants in two soil textures (sandy loam and clay loam) for 2 years. The IWCplant obtained values of 0.202 and 0.205 m3 m–3 for wheat and 0.189 and 0.194 m3 m–3 for canola in sandy loam and clay loam soils, respectively. These differences in the IWCplant between wheat and canola in the same soils demonstrate the importance of plant properties to estimate actual plant available water using IWC. These differences would be even more appreciable for root systems with a wider range of different properties.

Estimating Plant-Available Water Capacity for Claypan Landscapes Using Apparent Electrical Conductivity

2007 ◽  
Vol 71 (6) ◽  
pp. 1902-1908 ◽  
Author(s):  
Pingping Jiang ◽  
Stephen H. Anderson ◽  
Newell R. Kitchen ◽  
Kenneth A. Sudduth ◽  
E. John Sadler
Keyword(s):  
Electrical Conductivity ◽  
Water Capacity ◽  
Available Water ◽  
Available Water Capacity ◽  
Plant Available Water ◽  
Apparent Electrical Conductivity

scholarly journals Root-zone plant available water estimation using the SMOS-derived soil water index

2016 ◽  
Vol 96 ◽  
pp. 339-353 ◽  
Author(s):  
Ángel González-Zamora ◽  
Nilda Sánchez ◽  
José Martínez-Fernández ◽  
Wolfgang Wagner
Keyword(s):  
Soil Water ◽  
Root Zone ◽  
Water Index ◽  
Available Water ◽  
Plant Available Water

Deep drainage and soil salt loads in the Queensland Murray - Darling Basin using soil chloride: comparison of land uses

Soil Research ◽  
2011 ◽  
Vol 49 (5) ◽  
pp. 408 ◽  
Author(s):  
P. E. Tolmie ◽  
D. M. Silburn ◽  
A. J. W. Biggs
Keyword(s):  
Root Zone ◽  
Drainage Water ◽  
Native Vegetation ◽  
Deep Drainage ◽  
Water Capacity ◽  
Available Water ◽  
Murray Darling Basin ◽  
Available Water Capacity ◽  
Secondary Salinity ◽  
Soil Chloride

Increases in deep drainage below the root-zone can lead to secondary salinity. Few data were available for drainage under dryland cropping and pastures in the Queensland Murray–Darling Basin (QMDB) before this study. Modelled estimates were available; however, without measured drainage these could not be validated. Soil chloride (Cl) mass-balance was used to provide an extensive survey of deep drainage. The method is ‘backward-looking’ and can detect low rates of drainage over longer times. Soil Cl and other soil properties were collated for a number of soils, mostly Vertosols and Sodosols, for paired native vegetation, cropped and sometimes pasture sites, from historical data and new soil sampling. Large amounts of salt and Cl had accumulated under native vegetation (Cl mean 25 t/ha, range 6–54, in 2.4 m depth), due to low rates of drainage. Steady-state Cl balances for native vegetation gave average drainage of 1.2 mm/year at wetter, eastern sites and 0.3 mm/year for Sodosols and Grey Vertosols in drier, western areas. Chloride profiles were mostly of a shape indicating matrix/piston flow. One site (Hermitage fallow trial) appeared to be affected by diffusion of Cl to a watertable. The Cl profiles from 14 longer term cropping sites (18–70 years), mainly used for winter cropping/summer fallow, indicate: (i) large losses of Cl since clearing (mean 50%, range 13-85% for 0–1.5 m soil); and (ii) drainage rates from transient Cl balance are a relatively low percentage of rainfall but are considerably higher than under native vegetation. Drainage averaged 8 mm/year and ranged from 2 to 18 mm/year. This variation is partly explained by rainfall (R2 = 0.63) (500–730 mm/year) and soil plant-available water capacity (R2 = 0.77) (80–300 mm). Deep drainage increases with increasing rainfall and with decreasing available water capacity. Drainage under pasture was less than under cropping but greater than under native vegetation. The deep drainage water (leachate) was of poor quality and will increase salinity if added to good quality groundwater. Leachate at nine sites was too saline to be used (undiluted) for irrigation (>2500 mg Cl/L) and was marginal at the remainder of sites (~800 mg Cl/L). Cropping areas in the QMDB have the precursors for secondary salinity development—high salt loads and an increase in drainage after clearing. The Vertosols and Sodosols studied occur in 90% of croplands in the QMDB. Salinisation will depend on the properties of the underlying regolith and groundwater systems.

Estimation of the plant available water capacity of a soil profile

Soil Research ◽  
1981 ◽  
Vol 19 (3) ◽  
pp. 197 ◽  
Author(s):  
JA Mullins
Keyword(s):  
Electrical Conductivity ◽  
Soil Profile ◽  
Feature Model ◽  
Alternative Technique ◽  
Dryland Agriculture ◽  
Water Capacity ◽  
Available Water ◽  
Available Water Capacity ◽  
Conductivity Profile ◽  
Plant Available Water

The plant available water capacity (PAWC) was measured for a range of soils (black earths, grey, brown and red clays, krainozems, yellow earths and solodized solonetz/solodics) used for dryland agriculture in the uplands of th,- eastern Darling Downs of Queensland. Using these data, two one-parameter models - one based on the electrical conductivity profile and the other on observable profile features - were derived for estimating the PAWC of the soil profile. The electrical conductivity profile model reliably estimated the PAWC for black earths and grey, brown and red clays. In the case of the deep, black earths, it accounted for 90% of the variation. The observable profile feature model reliably estimated the PAWC for black earths and grey, brown and red clays and in the case of the grey, brown and red clays accounted for 88% of the variation. The models for the solodized solonetz/solodics were not significant. In addition the profile feature model provided estimates of PAWC for the krasnozems (grouped with black earths) and for the yellow earths and solodized solonetz/solodics as a group. An alternative technique for the estimation of PAWC for krasnozems and yellow earths is also presented. The techniques will provide a rapid first appraisal of the PAWC of a soil profile.

Soil water availability for plants as quantified by conventional available water, least limiting water range and integral water capacity

2010 ◽  
Vol 335 (1-2) ◽  
pp. 229-244 ◽  
Author(s):  
Hossein Asgarzadeh ◽  
Mohammad Reza Mosaddeghi ◽  
Ali Akbar Mahboubi ◽  
Akram Nosrati ◽  
Anthony Roger Dexter
Keyword(s):  
Soil Water ◽  
Water Availability ◽  
Soil Water Availability ◽  
Water Capacity ◽  
Available Water ◽  
Least Limiting Water Range

Advances in precision agriculture in south-eastern Australia. IV. Spatial variability in plant-available water capacity of soil and its relationship with yield in site-specific management zones

2009 ◽  
Vol 60 (9) ◽  
pp. 885 ◽  
Author(s):  
M. A. Rab ◽  
P. D. Fisher ◽  
R. D. Armstrong ◽  
M. Abuzar ◽  
N. J. Robinson ◽  
...  
Keyword(s):  
Grain Yield ◽  
Soil Properties ◽  
Clay Content ◽  
High Yield ◽  
Site Specific ◽  
Management Zones ◽  
Water Capacity ◽  
Available Water ◽  
Plant Available Water ◽  
The Mean

Spatial variability in grain yield can arise from variation in many different soil and terrain properties. Identification of important sources of variation that bear significant relationship with grain yield can help achieve more effective site-specific management. This study had three aims: (i) a geostatistical description/modelling of the paddock-level spatial structure in variability of plant-available water capacity (PAWC) and related soil properties, (ii) to determine optimal number of management zones in the paddock, and (iii) to assess if the variability in PAWC and related soil properties is significantly associated with the variability in grain yield across the management zones. Particle size distribution, bulk density (BD), field capacity (FC), permanent wilting point (PWP), and soil water content (SWC) at sowing were measured at 4 soil depths (to 0.60 m) at 50 representative spatial sampling locations across a paddock near Birchip (Victoria). PAWC and plant-available water at sowing (PAWs) were derived from these data. Moderate to strong spatial dependence across the paddock was observed. The magnitude of the structural variation and of range varied widely across different soil properties and depths. The south-east edge and the central areas of the paddock had higher clay content, FC, PWP, PAWC, and lower PAWs. The paddock was divided into 6 potential management zones using combined header yield and normalised difference vegetation index (NDVI). The adequacy of zoning was evaluated using relative variability (RV) of header yield and soil properties. The mean RV for 3 zones differed little from that of 6 management zones for header yield and for each measured soil property, indicating division of the paddock into 3 zones to be adequate. The results from residual maximum likelihood (ReML) analysis showed that low yield zones had significantly higher clay content, FC, PWP, SWC, and PAWC and significantly lower PAWs than both medium and high yield zones. The mean FC, PWP, and PAWC in the low yield zones were, respectively, 25%, 26%, and 28% higher, and PAWs 36% lower than their corresponding values in the high yield zones. Linear regression analysis indicated that 59–96% of the observed variation in grain yield across management zones could be explained by variation in PWP. The practical implications of these results are discussed.

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