Device for soil irrigation

An irrigating device formed from an absorbent product, such as a polymeric pulp or hydrophilic textile contained within a filtering envelope, such as a woven, knitted or non-woven fabric. The device is placed in the ground in communication with a source of water which may be above or below ground. The irrigation device provides for a uniform rate of irrigation of the soil in which it is placed, requires less water than conventional irrigation devices providing the same overall coverage, and is not subject to dogging or blockage, as with conventional irrigation devices. In one embodiment for preparing the irrigation device, the absorbent product is in the form of a tow of hydrophilic continuous filament and the textile filter envelope is produced in a continuous in-line operation in conjunction with the production of the tow. The irrigation device can be applied to the irrigation of soils to facilitate the growth of plants, trees, crops and the germination of seeds.

BACKGROUND OF THE INVENTION 
1. Field of The Invention 
The present invention relates to an irrigation device for irrigating soils, 
to the process for manufacturing such irrigation device and to the process 
for using such irrigation device in irrigating soils. More particularly, 
the present invention relates to an irrigating device of the type in which 
a fixed or renewable source of water connected to the irrigating device is 
slowly, but continuously applied to the soil. 
2. Discussion of the Prior Art 
In the irrigation of soils, for example, to promote the growth of crops, 
water is generally supplied either to the surface of the soil or directly 
into the soil. This has typically been accomplished utilizing drip type 
devices or porous or perforated tubes through which it is possible to 
establish an equilibrium between the water source, or zone of excess 
moisture and the soil of insufficient moisture content. 
However, particularly from the economic point of view, these prior art 
devices are expensive and bulky. In addition, it has been technically 
difficult when using porous or perforated tubes to ensure moisture 
equilibrium, because of the necessity for filtering the water from the 
water source to avoid blockage of the installation. In this regard, the 
inorganic salts present in water tend to block the holes or the pores of 
the porous or perforated tubes. This tendency is particularly noticeable 
in the case of intermittent operation of the irrigation devices. Therefor, 
it has proven necessary to install, generally near the irrigation 
orifices, means for avoiding such blockage. However, even when such 
filtering devices have been installed, it has been difficult to regulate 
the irrigation flow rate and in addition, frequent maintenance is 
required. 
Still further, and particularly in connection with sloping terrains, it has 
been found that these types of irrigation devices require an excess 
consumption of irrigation liquid, which is believed to be primarily due to 
the fact that since the water tends to saturate the lowest zone of the 
terrain, it is necessary to supply additional irrigation liquid to the 
upper zones to ensure constant or uniform wetting of the soil. 
Still further, in the case of surface installations of the irrigation 
devices, there are significant losses of irrigation liquid by evaporation 
and consequently, also an increased danger of blockage of the holes and 
pores of the irrigation tubes. This defect is particularly noticeable in 
regions which are very sunny and in regions with sandy terrain. 
SUMMARY OF THE INVENTION 
It is therefore an object of this invention to provide an irrigation device 
which is both simple to use and inexpensive to manufacture and maintain. 
It is another object of this invention to provide an irrigation device 
which is not subject to blockage or clogging as a result of precipitation 
of insoluble salts or other constituents inherently present in or added to 
irrigation liquids. 
It is still a further object of this invention to provide an irrigation 
device for irrigation of soils which require a reduced amount of 
irrigation liquid compared to conventional irrigation devices to obtain 
the same coverage, that is, moisture content of the irrigated soil.

The irrigation device of this invention can be formed into any desireable 
shape or configuration depending upon the terrain in which it will be 
utilized and the desired degree of irrigation and moistening of the soil. 
When the absorbent product is an absorbent, amorphous, synthetic polymer 
pulp, it can be obtained by precipitating the polymeric material, from its 
solution in a solvent for the polymeric material, in a bath containing a 
non-solvent for the polymeric material, but which is miscible with the 
solvent. 
In use, the irrigation device is buried in the soil, in the zone to be 
irrigated, and connected by suitable means to a source of irrigating 
liquid. The irrigation device can be placed in the ground either 
horizontally, vertically or obliquely disposed with respect to the 
surface. 
The water source or other aqueous irrigation liquid can be any natural or 
artificial source, including above ground or underground installations, as 
well as natural bodies of water above and below the surface. 
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS 
As previously stated, the irrigation device of this invention comprises an 
absorbent, amorphous, synthetic polymer pulp or an absorbent textile in 
the form of a tow of hydrophilic, continuous filaments. 
The pulps are generally preferred because of their high absorption 
capacities, especially towards water. For example, pulp formed from 
polyamides and polyesters generally absorb up to fifteen times their own 
weight of water. 
The absorbent pulps which are particularly useful in the irrigation devices 
of this invention, are those having a bulk density of between 0.01 and 0.5 
g/cm.sup.3, preferably between 0.04 and 0.2 g/cm.sup.3, and also, 
possessing a specific surface area, determined by gas absorption according 
to the Brunauer-Emmet-Teller (B.E.T.) method of between about 2 to about 
12 m.sup.2 /g. 
Basically, these amorphous absorbent pulp materials can be obtained by 
precipitation of a polymeric material from its solution in a solvent 
therefor, in a bath containing essentially a non-solvent for the polymeric 
materials, which non-solvent is miscible with the solvent. The pulp is 
thereafter recovered from the solvent and non-solvent mixture by 
filtration, decantation, centrifugation, or any other suitable means. 
These pulp forming techniques are in themselves well known in the art and 
do not, per se, form part of the inventive feature of the subject 
invention. 
According to one preferred method for forming the amorphous polymer pulps, 
a solution of the polymer is introduced, with stirring, into a bath 
containing essentially a non-solvent for the polymeric material. The 
resulting pulp is thereafter filtered from the solvent/non-solvent bath 
and then drained, washed and dried. The pulps can also be obtained by a 
continuous method in which a stream of solution of the polymer is injected 
into a stream of non-solvent and the resulting pulp is then collected on a 
moving conveyor belt. After draining, washing, suction-draining and 
drying, the pulp is coarsely disaggregated to form the final absorbent 
amorphous pulp product. 
Generally, any synthetic polymeric material from which absorbent pulps can 
be prepared, can be used in the irrigation device of this invention. For 
instance, mention can be made of such cellulosic compounds as cellulose 
acetate and cellulose triacetate or synthetic polymers, such as 
polyamides, polyesters, vinyl polymers, polyolefins, polyacrylonitriles, 
and the like. Because of their high absorption capacities, absorbent pulps 
formed from polyamides and polyesters are most preferred. 
The absorbent product may also be formed from hydrophilic textile 
materials, preferably in the form of a tow of continuous, crimped or 
non-crimped filaments. This embodiment of the irrigation device of the 
present invention has the advantage that the textile filter envelope can 
be produced in a continuous in-line operation in conjunction with the 
manufacture of the tow. For example, this continuous production can be 
achieved by tubular knitting or by braiding, lapping or the like of the 
envelope about the tow, at the same rate by which the tow is produced. 
When desired, the tow can be crimped by any conventional crimping 
technique, such as by mechanical means or fluid means. The crimping 
operation can also be carried out as a continuous in-line operation during 
the manufacturing operation. The tubular knitting operation provides an 
elongate volume whose cross-section may, for example, be circular, oval, 
rectangular, and the like. 
The filamentary material of the hydrophilic textile tow may be any 
artificial or synthetic filamentary textile material which is either 
naturally hydrophilic or which has been rendered hydrophilic by suitable 
chemical treatment. Techniques for rendering filamentary textile materials 
hydrophilic are well known in the art and do not, per se, form a part of 
this invention. 
The amount of the absorbent product in the irrigation device of this 
invention is not, per se, critical, but should naturally be sufficient to 
absorb sufficient irrigation liquid to accomplish the desired degree of 
wetting of the soil. The amount of the absorbent product will therefor, 
depend on such factors as its absorption capacity, the depth below the 
ground of the irrigation device, the nature of the soil and climate, the 
type of crop or other product being irrigated, etc. 
The textile filter envelope used for containing the absorbent product may 
be any woven, knitted or non-woven fabric. The textile material should, of 
course, be one which will be able to withstand the soil environment in 
which it is buried. When the textile filter envelope is of a non-woven 
material, it is preferably obtained as a "spunbonded" material, although 
non-woven obtained by dry methods can also be used in this invention. 
The weight per square meter and texture of the textile filter envelope are 
not particularly critical, but will depend, in general, on the nature of 
the desired irrigation. As previously mentioned, the textile filtering 
envelope is preferably produced as a continuous in-line operation in 
conjunction with the operation of assembling the absorbent tow of 
hydrophilic textile. In this regard, it should be understood that the word 
"tow" as used herein, is intended to include not only a single tow, but a 
plurality of tows. In fact, particularly for relatively thick irrigation 
devices having large absorption capacities, it would generally be 
preferred to combine several tows in a single device. In this case too, 
the filter envelope can be produced as a continuous in-line operation in 
conjunction with the operation of assembling the tows of the hydrophilic 
textile filamentary materials. 
This invention is, of course, not limited to forming the textile filter 
envelope continuously with the formation of the tow, but the textile 
filter envelope can also be placed around the tow after the manufacture of 
the latter. 
Also, the irrigation device of this invention need not necessarily be in 
the form of a tubular product of uniform cross-section, but may 
additionally, be in the shape of a flat bag containing the absorbent 
product, or formed as a plurality of textile webs of suitable width and 
length, depending upon the desired end use, with the absorbent product 
placed between the textile webs. 
The irrigation device, in use, is located beneath the surface of the soil 
and is connected through suitable pipes and valves to a source of 
irrigation liquid. The irrigation device can be placed either 
horizontally, vertically or at an angle relative to the surface of the 
soil. The liquid supply can be either a stagnant source or under pressure. 
Particularly for long lengths of the irrigation device, the liquid supply 
should be under suitable pressure to assure that all of the absorbent 
capacity of the absorbent product is utilized. The irrigation liquid is 
typically water, although other adjuvants such as fertilizers, 
insecticides, pesticides, nutrient solutions and the like can be added. In 
addition, where desired, the liquid can be heated. 
The irrigation device is located at a suitable depth below the surface of 
the soil. The depth will depend, in part, on the type of crops to be 
irrigated, taking into consideration, for example, the root depth of the 
crops, the amount of moisture needed by the crops, etc., as well as on 
whether the irrigation device is placed horizontally, vertically or 
obliquely. 
The irrigation device of this invention makes it possible to regulate and 
meter the moistening and irrigation of all types of soils. By virtue of 
the filtering property of the textile wrapper and in view of the fact that 
the water or other aqueous irrigation liquid issues gradually from the 
absorbent filling, it is possible to maintain constant moisture without 
water losses or excess feed of water, in such environments as pastures, 
sports grounds, food crop locations, etc., with or without combination 
with a greenhouse effect. 
With particularly long lengths of the irrigation device of this invention, 
in order to overcome possible adverse effects due to pressure drops, it is 
preferred to feed the irrigation liquid to the irrigation device under 
pressure and/or to have the absorbent product filling packed within the 
textile filter wrapper somewhat less densely than with shorter lengths of 
the irrigation device. On the other hand, the irrigation device can be 
used in short lengths, such as for watering of house plants. The use of 
the irrigation device for watering house plants is particularly 
advantageous when it would not otherwise be possible to care for the plant 
over extended periods of time. By regulating the supply of water to the 
plants such as, for example, with a valve system, the flow rate to the 
irrigation device and from the irrigation device to the soil can be 
regulated to provide the desired degree of moisture. Also, when the 
irrigation device is intended to cover large areas and consequently, must 
be of long length, it is possible to use the irrigation device as shorter 
segments connected to lengths of unobstructed pipe or other conduit. It is 
also possible to connect the liquid supply to the irrigation device of 
this invention at a plurality of points along its length in order to 
counteract any possible unduly high pressure drops inherently present in 
long lengths of the irrigation device. 
Accordingly, the irrigation device of this invention can be used to provide 
and maintain constant moisture levels in various types of soils for 
facilitating the growth of plants, crops and trees and for the germination 
of seeds. The irrigation device is particularly useful in regions, such as 
desert zones, wherein the water source is present as a sheet or lake under 
a sandy soil surface. With the irrigation device of this invention, the 
need to frequently water crops in such areas due to the high rates of 
evaporation from the heat of the sun and by absorption of the water into 
the sand, is eliminated. Further, by maintaining the soil at a constant 
moisture level at a fixed depth below the surface without evaporation, 
excessive consumption of liquid is avoided making it possible to permit 
greater preservation of the underground sheets of water. 
The present invention will now be described by the following illustrative, 
non-limiting examples. 
EXAMPLE 1 
An irrigation device if formed from a tube of 100 m. diameter made from a 
non-woven fabric of continuous filaments of poly(ethylene glycol 
terephthalate), weighing 150 g/m.sup.2, and this tube is filled with an 
absorbent product consisting of poly(hexamethylene adipamide) pulp, which 
is obtained in the following manner: 
Poly(hexamethylene adipamide) is dissolved, at a rate of 10% by weight, in 
98% strength sulfuric acid, with stirring for four hours. The solution 
obtained is fed, with stirring, into a bath containing a normal aqueous 
sodium hydroxide solution. The resulting precipitate is filtered off, then 
washed at ambient temperature, and thereafter, drained and dried to 
constant weight. The white dry pulp obtained has a bulk density of 0.6. A 
section of the irrigation device is shown schematically in FIG. 1. 
The irrigation device of 250 cm long thus produced is buried at a depth of 
10 centimeters in a trough two meters long containing fine sand of 
particle size between 100 and 200 microns. The end of the tube is 
connected to a vessel of five liters capacity containing water. Through 
capillary action, the water is absorbed by the poly(hexamethylene 
adipamide) pulp and passes through the permeable non-woven textile 
filtering wrapper and moistens the sand up to the surface. 
Over the course of eight days, samples of sand were taken at various points 
of the trough at a distance of 25, 50, 100 and 150 centimeters from the 
water supply source. A constant moisture content of 15% was found, 
regardless of the day or the sampling point. Furthermore, the level of 
water in the vessel fell only very slightly over the eight day period. 
In order to assess the effect of a source of heat on the surface of the 
trough, infrared lamps were provided 50 cm above the surface, of four 1000 
watts/220 volts. A dry zone was found to appear at the surface of the 
trough, but the interior of the soil remained moist. Shortly after removal 
of the source of heat, the dry zone of the surface of the soil 
disappeared. 
EXAMPLE 2 
Pulp was produced as in Example 1 and placed between two webs of non-woven 
fabric weighing 210 g/m.sup.2. The fabric was formed from continuous 
filaments of poly(ethylene glycol terephthalate). The irrigation device of 
350 cm long and 45 cm wide thus produced was placed in a trough one meter 
wide, three meters long and 0.50 meters deep, filled with soil, at a depth 
of 15 centimeters, over half the width and over the entire length of the 
trough. Seeds of a half long, 18 day type of radish were sown over the 
whole trough, and the part containing the irrigation device was connected 
to a supply source in the form of a vessel containing 10 liters of water. 
The part not containing the irrigation device was watered regularly. As of 
three weeks, it was found that the radishes which had grown in the zone 
containing the irrigation device, had 18 centimeter high leaves, while the 
watered radishes had leaves which were only 13 centimeters high. 
Furthermore, it was found that only 4.5 liters of water were used with the 
irrigation device, while 7 liters of water were used with the other half 
of the trough, still producing inferior results. 
EXAMPLE 3 
An irrigation device according to the subject invention was produced by 
placing 42 tows, weighing 28 g/m of continuous viscous filaments, each of 
gauge 17 dtex, in an envelope formed from a knitted fabric of a continuous 
yarn of poly(hexamethylene adipamide) of gauge 110 dtex/30 strands. A 
section of the irrigation device is shown schematically in FIG. 2. The 
irrigation device of 12 cm diameter and 250 cm long thus produced were 
used for moistening roots of young shrubs in a reafforestation zone having 
a low water content. The loss of water observed with conventional 
irrigation devices was avoided and the moisture was sufficiently 
maintained around the roots of the shrubs, without interference of the 
development of the latter.