Some Field Observations with Tensiometers (1)

Richards, L. A.; Neal, O. R.

doi:10.2136/sssaj1937.03615995000100000011x

Cited by 25 publications

(8 citation statements)

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“…Monitoring soil moisture is another scheduling procedure that has been used in horticulture since the fi rst grower scrutinized a hand full of semi-moist soil. The fi rst instrument used to quantify soil water status was the tensiometer, developed by L.A. Richards (Richards and Neal, 1936). Historically, the chief limitation of tensiometers was their relatively narrow working range of soil water potential, which made their use with surface irrigation methods problematic due to the wide range of soil water contents between irrigation.…”

Section: Processes In Irrigation Management Of Horticultural Cropsmentioning

confidence: 99%

Irrigation Water Management of Horticultural Crops

Fereres¹,

Goldhamer²,

Parsons³

2003

HortSci

172

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WP by increasing yield and/or reducing ET always results in net savings, thus reducing agricultural water requirements. This is a key point in assessing the opportunities for true water savings in horticultural crop cultivation and will be addressed in detail later in this paper.Water productivity in irrigated agriculture varies widely and depends on many biophysical and management factors. Because variations in ET among crops are within an order of magnitude apart, by far the most important factor infl uencing WP is the economic value of the product. Horticultural products are usually high value and thus WP normally exceeds that of fi eld and row (agronomic) crops. For example, using current values for yield and ET characteristic of California agriculture, the WP of corn is about 0.20 $/m 3 , compared to 0.70 $/m 3 for almond, 5.00 $/m 3 for strawberry, and even more for greenhouse and ornamental crops. An extreme example of this occurs with vegetable crops grown under plastic in southeast Spain during the off-season. The combination of high market prices and low ET leads to a WP of about 10 $/m 3 . While impressive, even this value cannot compete with that of industrial and urban uses. Nevertheless, it helps explain the trend of shifting irrigated acreage from low value fi eld and row crops to horticultural crops in many water-scarce areas of the US, a trend that will probably increase worldwide (National Research Council, 1996). Indeed, the WP of an irrigation district in Southern Spain increased over a four year period as the proportion of horticultural crops increased (I. Lorite, L. Mateos, and E. Fereres, unpublished data).This paper describes the evolution of water use as related to productivity with an emphasis on the U.S. experience, analyzes how irrigation systems and management have evolved since the early 1900s, and explores the challenges and opportunities for water conservation in horticulture. Because of the broad scope of the subject and limited space, the paper focuses primarily on tree crops although many principles are applicable to all horticultural crops.

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Section: Processes In Irrigation Management Of Horticultural Cropsmentioning

confidence: 99%

Irrigation Water Management of Horticultural Crops

Fereres¹,

Goldhamer²,

Parsons³

2003

HortSci

172

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“…Tensiometers have been used extensively to study water movement through field soils [e.g., Cannel and Stolzy, 1962;Haise et al, 1955;Marshall and Stirk, 1949;Richards, 1954;Richards and Neal, 1936]. In these investigations, their use was primarily directed toward measuring hydraulic gradients existing during infiltration or during short periods of drainage following infiltration.…”

Section: Introductionmentioning

confidence: 99%

Water movement through Panoche clay loam soil

Nielsen¹,

Davidson²,

Biggar³

et al. 1964

Hilg

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with tensiometers. Some experiments have involved measurements of tension only, while others have included corresponding changes in soil water content. Investigations by Israelsen [1918] ,8 Israelsen and West [1922], Scofield and Wright [1928], and Edlefsen and Bodman [1941] typify early endeavors to ascertain the water-storage capacity of soils. Soil water was measured gravimetrically in field plots before and after heavy irrigations. In addition to the quantity of water stored, the amount of water passing through soil profiles during extended periods of drainage was measured. In the case of the latter investigation it was found that the average rate of water lost from a 5-foot profile over a period of 2 days after irrigation to 30 days after irrigation was approximately 0.1 inch per day. Using a neutron meter to measure soil water repeatedly at the same depths within several field profiles, Burrows and Kirkham [1958] studied the redistribution of applied water under the action of gravity to define field capacity. The field capacity of each 6-inch layer to a depth of 5 feet was defined on the basis of the shape of the drainage curves.

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“…A tensiometer consists essentially of a fluid pressure measuring device and a porous membrane through which the tensiometer fluid communicates with the soil fluid. The response of the pressure measuring device can be characterised by the 'gauge sensitivity', S, (Richards and Neal, 1937) defined as the change in pressure registered by the gauge per unit change in volume of the fluid entering or leaving it. The porous membrane can take various geometrical forms such as cylinders, hemispheres, plane faces, or combinations of these.…”

Section: Theorymentioning

confidence: 99%

“…The porous membrane can take various geometrical forms such as cylinders, hemispheres, plane faces, or combinations of these. The flow properties of each can be characterised by the membrane or cup conductance, C , (Richards and Neal, 1937) defined as the volume of liquid crossing the membrane per unit time per unit pressure difference across the membrane. It perhaps ought to be remarked that the values of gauge sensitivity and of the cup conductance are not necessarily simply those of the sensing unit or of the tensiometer cup respectively: the gauge sensitivity specification must include the influence of all connecting tubes, and similarly, the value of cup conductance must include the 'contact conductance' which it has been found necessary to include in outflow type measurements of hydraulic conductivity (for example, see Rijtema, 1959).…”

Section: Theorymentioning

confidence: 99%

Theory of Time Response of Tensiometers

Towner¹

1980

Journal of Soil Science

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Summary The time taken for a tensiometer to reach equilibrium with the soil‐water pressure is a function not only of the tensiometer characteristics but also of the soil‐water transport properties. When. in an appropriate system of units. the numerical value of the conductance of the tensiometer cup is small compared with that of the hydraulic conductivity of the soil, and the sensitivity of the pressure ‘gauge’ is large compared with the differential water capacity of the soil. then the precision of the measurements is such that the observed response may be indistinguishable from that of a tensiometer in bulk water. referred to as ‘tensiometer limited’. The theory developed in this paper for a hemispherical tensiometer cup shows that tensiometer‐limited conditions can be achieved in practice. Moreover. such conditions would often correspond to a rapid response system. It is suggested that it might be advantageous in the design of a field recording system to choose a tensiometer‐limited system even if it is not the fastest realisable one in order that its response is completely predictable from the known tensiometer characteristics. independent of the unknown soil properties. which may be changing.

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Some Field Observations with Tensiometers (1)

Cited by 25 publications

References 0 publications

Irrigation Water Management of Horticultural Crops

Irrigation Water Management of Horticultural Crops

Water movement through Panoche clay loam soil

Theory of Time Response of Tensiometers

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