Method of inhibiting the formation of crystalline mineral deposits in soil

The present invention provides an improved method for growing a plant in soil while irrigating the soil with water which contains deposit forming minerals. According to the present invention, an effective amount of 1-hydroxyethane 1,1-diphosphonic acid (HEDPA) is admixed with irrigation water and applied to the soil in which the plant is growing.

TECHNICAL FIELD 
This invention relates to a method of growing plants in soil, and more 
particularly, to a method of using source water to water plants growing in 
soil while inhibiting the formation of crystalline mineral deposits in the 
soil. 
RELATED APPLICATIONS 
This application is a continuation-in-part of our copending application 
Ser. No. 08/052,065, filed April 22, 1993, and entitled "A Method and 
Composition for Inhibiting the Formation of Hard Water Deposits on Fruit." 
BACKGROUND INFORMATION 
A plant growing in soil requires irrigation with water. Irrigation water 
generally contains deposit forming minerals. Due to the presence of 
deposit forming minerals, irrigation of a plant results in the formation 
of crystalline mineral deposits in the soil which are virtually impervious 
to water. Such crystalline mineral deposits in soil can be detrimental to 
a plant growing in the soil and the future usefulness of the soil. As 
crystalline mineral deposits accumulate in the soil, irrigation water is 
diverted around the deposits, resulting in channeling of the water in the 
soil. As irrigation water begins to channel through the soil, a majority 
of the water is often channeled away from the root system of the plant 
resulting in a larger amount of irrigation water being required to provide 
moisture to the root system of the plant. The creation of larger flows of 
water in some areas of the soil than in others results in erosion of part 
of the soil. Further, crystalline mineral deposits can form a sublayer of 
virtually impervious deposits in the soil which inhibit the root system of 
a plant from penetrating past the sublayer to the deeper soil. When the 
root system of a plant does not penetrate deeply into the soil, the plant 
is weakened. Finally, crystalline mineral deposits make the soil difficult 
to cultivate. 
DISCLOSURE OF THE INVENTION 
The present invention provides a method of growing a plant in soil. The 
method includes providing water containing crystalline deposit forming 
minerals. A mixture is formed by admixing an effective amount of 
1-hydroxyethane 1,1-diphosphonic acid (HEDPA) with the water. The HEDPA is 
present in an amount sufficient to alter the crystalline deposit forming 
minerals such that following evaporation of the water, substantially all 
of the crystalline deposit forming minerals form an amorphous powder. The 
mixture is applied to soil in which roots of a plant are growing. The 
water is allowed to evaporate from the soil such that substantially all of 
the crystalline deposit forming minerals form an amorphous powder. 
Preferably, the effective amount of 1-hydroxyethane 1,1-diphosphonic acid 
(HEDPA) is at least about 1/4 ppm. In a more preferred form of the 
invention, the effective amount of HEDPA is between about 1/4 ppm and 
about 5 ppm. In an even more preferred embodiment of the invention, the 
effective amount of HEDPA is about 2 ppm. 
These and other advantages and features will become apparent from the 
detailed description of the best mode for carrying out the invention that 
follows. 
BEST MODE FOR CARRYING OUT THE INVENTION 
When a plant growing in soil is irrigated with water which contains deposit 
forming minerals, crystalline mineral deposits form in the soil after the 
water has evaporated. The crystalline mineral deposits are substantially 
impervious to water, resulting in later applied irrigation water flowing 
around the deposits. Thus, the channeling prevents the water from 
percolating throughout the soil to provide uniform irrigation to the root 
system of the plant. This redirection of irrigation water forms channeling 
in the soil which can result in erosion of the soil. Over a period of 
time, a sublayer of crystalline mineral deposits may form which is 
difficult for the root systems of the plant to penetrate. If the root 
system is unable to penetrate the sublayer, the root systems may extend 
horizontally across the top of the sublayer, resulting in a plant which is 
structurally weaker and more vulnerable to temperature changes. Another 
side effect of accumulation of crystalline mineral deposits is that the 
soil becomes very difficult to cultivate. Herein, the term "plant" refers 
to any type of plant, such as a tree, shrub, flower, herb, vine, or grass. 
Herein "soil" refers to a medium for growing plants, whether situated in 
containers or in a field. 
Generally, irrigation water is supplied from sources such as wells, rivers, 
and lakes. Such water is termed "source water." Source water is generally 
hard, referring to the presence of any or all of the following in the 
water: calcium, iron, silicate, magnesium, sodium chloride, sodium 
bicarbonate, sulphate, nitrates, and fluoride. The amount of hardness of 
water is measured in parts per million (ppm). Typically source water has a 
hardness between about 20 ppm to about 450 ppm. When soil is irrigated 
with hard water, crystalline mineral deposits form in the soil which can 
be detrimental to the crop growing in the soil and the use of the soil for 
future crops. 
According to the present invention, an effective amount of HEDPA is admixed 
to the irrigation water. As crops growing in soil are irrigated with the 
water which includes HEDPA, an amorphous powder is formed in the soil. The 
amorphous powder is permeable by water, enabling irrigation water to 
percolate through the soil and provide uniform moisture to the crop 
growing in the soil. In addition, the soil remains loose, thus easily 
cultivated or penetrated by a plant's root system. HEDPA is an alkyl 
diphosphonate. A commercially available form of HEDPA is termed 
1-hydroxyethane 1,1-diphosphonic acid and has the following structure: 
______________________________________ 
HO O OH O OH 
P C P 
HO CH.sub.3 OH 
______________________________________ 
Herein HEDPA is used to describe a number of behave alike alkyl 
diphosphonates of the basic structure: 
______________________________________ 
HO O R O OH 
P C P 
HO R' OH 
______________________________________ 
The following is a list of known HEDPA variants and their structures which 
indicate what constitutes and may be represented by --R and R': 
______________________________________ 
HO O H O OH methylene diphosphonic 
P C P acid (MDP) 
HO H OH 
HO O OH O OH hydroxymethylene 
P C P diphosphonic acid (HMDP) 
HO H OH 
HO O Cl O OH dichloromethylene 
P C P diphosphonic acid (Cl.sub.2 MDP) 
HO Cl OH 
HO O OH O OH hydroxycyclohexylmethylene 
P C P diphosphonic acid (HCMDP) 
HO OH 
HO O OH O OH 1-hydroxyethylidene 
P C P diphosphonic acid (HEDPA) 
HO CH.sub.3 OH 
HO O OH O OH 1-hydroxy-3aminopropane 
P C P 1,1-diphosphonic acid 
HO CH.sub.2 
CH.sub.2 
NH.sub.2 
OH (ADP) 
______________________________________ 
An effective amount of HEDPA may be provided in the irrigation water 
mixture when there is as little as 1/4 ppm HEDPA. In some circumstances, 
additional amounts of HEDPA may be needed. It has been found that the 
amount of HEDPA which is needed may be increased when the hardness of the 
irrigation water increases. Seldom is more than 5 ppm HEDPA necessary. In 
fact, usually no more than 2 ppm is needed. Although, adding additional 
HEDPA has not been found to negatively impact the scale or deposits in the 
soil. But, as additional HEDPA is added to irrigation water, the cost of 
utilizing this invention increases. 
The effective amount of HEDPA is added to the irrigation water before the 
irrigation water is applied to the soil. In a preferred form of the 
invention, a metering pump is provided and operably attached to the 
irrigation water feed line. The metering pump is set to feed an effective 
amount of the HEDPA into the irrigation water. Then, the irrigation water 
HEDPA mixture is applied to the crop growing in the soil by the use of an 
irrigation system. 
When soil is watered with irrigation water which includes HEDPA, the 
accumulation of crystalline mineral deposits in the soil is retarded. 
Similarly formation of a sublayer of crystalline mineral deposit in the 
soil is retarded. Accordingly, the root system of a plant growing in the 
soil is able to penetrate deeply into the soil resulting in a structurally 
sound plant which is more tolerant of variations in temperature. In 
addition, the soil remains more permeable to water, allowing irrigation 
water to percolate through the soil and to the root system of the plant 
without excessive watering. Further, the soil remains easy to cultivate 
due to the lack of large amounts of crystalline mineral deposits. Also, 
channeling of irrigation water through the soil is inhibited, reducing 
erosion of the soil. 
The nature and substance of the instant invention as well as its objects 
and advantages will be more clearly understood by referred to the 
following specific examples.

EXAMPLE 1 
Three hundred milliliters of artificially created hard water (180 ppm total 
hardness as CaCO.sub.3) were added to each of two beakers, beaker 1 and 
beaker 2. Beaker 1 was untreated while beaker 2 was treated with 5 ppm of 
HEDPA. The water in the beakers was allowed to evaporate to dryness at 100 
to 110.degree. F. The residue in each beaker was observed under a 
microscope. When magnified (100.times.) the residue in untreated beaker 1 
showed crystalline angular structures, as shown in photograph 1. The 
crystalline angular structures are considered by the inventors to be 
crystalline mineral deposits from the deposit forming minerals of the hard 
water. In contrast, when magnified (100.times.) the residue in treated 
beaker 2 showed irregularly shaped amorphous structures, as shown in 
photograph 2. The amorphous structures are considered by the inventors to 
be amorphous powder resulting from the reaction of the deposit forming 
minerals in the hard water with the HEDPA. 
EXAMPLE 2 
One hundred grams of caliche soil of 20+ mesh were added to each of two 
beakers, beaker 3 and beaker 4. Three hundred milliliters of artificially 
created hard water (180 ppm total hardness as CaCO.sub.3) were added to 
each beaker. Beaker 3 was untreated while beaker 4 was treated with 5 ppm 
of HEDPA. The beakers were thoroughly mixed, and then the water in each 
beaker was allowed to evaporate to dryness at 100 to 110.degree. F. 
resulting in a composition of soil deposits from the hard water. Under 
magnified examination (100.times.), the soil composition in untreated 
beaker 3 showed crystalline, angular structures composed of small crystals 
arranged in a regular pattern, as shown in photograph 3. The crystalline 
angular structures are considered by the inventors to be crystalline 
mineral deposits from the deposit forming minerals of the hard water. 
Under magnified examination (100.times.), the soil composition in treated 
beaker 4 showed round, amorphous structures, as illustrated in photograph 
4. The amorphous structures are considered by the inventors to be 
amorphous powder resulting from the reaction of the deposit forming 
minerals with the HEDPA. 
EXAMPLE 3 
In order to determine the mechanical strength of the soil composition in 
each of beakers 3 and 4, a ten gram weight was dropped from a height of 
eight inches above the soil composition in each beaker. No affect was 
shown in either beaker. 
EXAMPLE 4 
Example 3 was repeated using 20 gram weights. A small portion of the soil 
composition in untreated beaker 3 was displaced by the 20 gram weight. A 
larger amount of the residue in treated beaker 4 was displaced by the 20 
gram weight. 
EXAMPLE 5 
Example 3 was repeated using 50 gram weights. When the weight was dropped 
on the soil composition in untreated beaker 3, a firm "thud" type sound 
was heard and there was displacement of the residue in the beaker. When 
the weight was dropped on the soil composition in treated beaker 4, a 
muffled thud was heard and there was a large displacement of the residue 
in the beaker. 
EXAMPLE 6 
Example 3 was repeated using 147.5 gram weights. The soil composition in 
untreated beaker 3 displayed an area of disturbance upon impact of the 
147.5 gram weight. The soil composition in treated beaker 4 completely 
disrupted upon the impact of the 147.5 gram weight, resulting in a 
scattering of the soil composition. 
EXAMPLE 7 
Container 1 and container 2, each with drainage holes in the bottom, were 
filled with soil. The containers were placed under a 250 watt heat lamp. 
Sprayers were hung over each container. The sprayers operated on a ten 
minute cycle timer, calibrated to deliver 0.33 gallons of water per hour. 
The sprayers were to set to spray for one minute and dry for nine minutes. 
The spraying cycle continued twenty-four hours a day for twenty-one days. 
Container 1 was sprayed with hard water (180 ppm total hardness as 
CaCO.sub.3). Container 2 was sprayed with hard water (180 ppm total 
hardness as CaCO.sub.3) plus 5 ppm HEDPA. After twenty-one days, the 
containers were placed in an oven operating at 150.degree. F. and allowed 
to dry for two days. Then, an initial 500 milliliters of water were 
simultaneously poured over each container. The water passing through each 
container was monitored for speed as well as quantity. Three minutes after 
the initial 500 milliliters had been poured, no water had passed through 
untreated container 1. 25 milliliters had passed through treated container 
2. Then, a second 500 milliliters of water were simultaneously poured over 
each container. Water began to pass through the container 1 and container 
2. After three minutes from the second pouring, 90 milliliters of water 
had passed through untreated container 1 and 130 milliliters had passed 
treated container 2. 
EXAMPLE 8 
Container 1 and container 2 were inverted. Untreated container 1 showed the 
formation of channels through the soil with most of the moist soil being 
around the edges of the container. Treated container 2 show more even 
patterns of absorption with most of the moist soil located on the top area 
of the container. 
While specific embodiments of the present invention have been shown and 
described in detail to illustrate the utilization of the inventive 
principles, it is to be understood that such showing and description have 
been offered only by way of example and not by way of limitation. 
Protection by Letters Patent of this invention in all its aspects are set 
forth in the appended claims. The scope of the appended claims is to be 
interpreted as the broadest scope that the prior art allows.