Organic neutral liquid fertilizer and process for preparing the same

The present invention provides a neutral liquid fertilizer comprising as essential ingredients nitrogenous, phosphatic and potash fertilizers and an organic acid, and a thickener, and also provides a process for preparing the same.

FIELD OF THE INVENTION 
The present invention relates to an organic neutral liquid fertilizer and a 
process for preparing the same. 
PRIOR ART 
Fertilizers in current use are available in the form of dust, granules, 
liquid, and the like. Regardless of their forms, almost all fertilizers 
exhibit strong acidity. The major component of fertilizers is salts except 
for urea. 
For example, ammonium sulfate is strongly acidic and has a pH of 4.0-4.5. 
Potash fertilizer is mainly composed of potassium sulfate and potassium 
chloride and therefore, like ammonium sulfate, it contains a large amount 
of sulfate radical. Phosphatic fertilizer is mainly composed of liquid 
phosphoric acid and therefore, it exhibits strong acidity. To neutralize 
such acidity, liquid phosphoric acid has been combined with lime to 
produce a calcium superphosphate fertilizer or combined with plaster to 
form phosphatic fertilizer soluble in organic acid solution, both 
fertilizers being commercially available. 
PROBLEMS TO BE SOLVED BY THE INVENTION 
Conventional fertilizers render the soil of cultivated areas and paddy 
fields acidic, due to accumulation of inorganic salts such as sulfate 
anion, resulting in acidification of the soil to pH 4.0-4.5. Such 
accumulation retards the growth of crops and causes root rot, stem rot, 
and injury by continuous cropping. Ammonium sulfate is degraded to nitrous 
acid nitrogen in a strongly acidic soil. Nitrous acid nitrogen interferes 
with the protein synthesis and starch production in plants and is likely 
to accumulate in stems and leaves in the form of an incomplete protein, 
which decreases tolerance of plants to temperature changes. At a higher 
temperature, the undergradable nitrogen source in stems and leaves turns 
into a gaseous form to cause the cell burst. The cell burst makes plants 
susceptible to fungus diseases such as powdery mildew. Such diseases have 
been one of the major issues in agriculture. To prevent acidification of 
soil and to maintain productive soil in cultivated areas and paddy fields, 
the development of neutral fertilizer free of sulfate has been an 
imperative demand among the agriculturists. 
MEANS FOR SOLVING THE PROBLEM 
When a strong acid is reacted with a strong alkali in a large scale, the 
reaction is explosive. A neutral liquid fertilizer has not been 
industrially manufactured due to the danger of the reaction. The present 
inventor has found a method of preventing the explosion caused by heat of 
neutralization. Namely, it has surprisingly been found that explosive heat 
of neutralization can effectively be quenched by performing the reaction 
in an organic acid solution. 
SUMMARY OF THE INVENTION 
The first aspect of the invention is to provide an organic neutral liquid 
fertilizer comprising as essential ingredients nitrogenous, phosphatic 
acid potash fertilizers and an organic acid, and a thickener. 
The second aspect of the invention is to provide process for preparing said 
organic neutral liquid fertilizer, comprising the steps of: 
(a) adding an organic acid to water with stirring at room temperature; 
(b) adding 1/3 of the amount to be used of liquid phosphoric acid gradually 
to the above mixture with stirring; 
(c) adding 1/3 of the amount to be used of potassium hydroxide gradually to 
the mixture with stirring while keeping the temperature below 60.degree. 
C., and then allowing the temperature to rise to 90.degree. C.; 
(d) adding 1/3 of the amount of urea all at once to the mixture, which 
decreases the temperature to about 40.degree. C.; 
(e) repeating the above steps (b)-(d) twice; 
(f) adding a thickener and an amino acid to the mixture; and 
(g) adding either chelated iron and copper sulfate or ammonium iron citrate 
to the mixture. 
According to the invention, ammonium sulfate is usually used as a 
nitrogenous source, liquid phosphoric acid as a phosphatic source, and 
potassium hydroxide as a potash source. 
Thickeners which may be mentioned include synthetic resins such as 
polyvinyl alcohol, sodium alginate, seaweed extract, etc. These thickeners 
can encapsulate the essential ingredients such as nitrogenous, phosphatic 
and potash fertilizers and imparts slow-acting property to the product. 
Among the thickeners, sodium alginate is preferable since it has buffering 
effects on the pH value. 
Chelated iron and copper sulfate may attach to plants and facilitate the 
absorption of the sun light by the stems and leaves. In addition, these 
agents render the product of the invention moss-green, thus increasing the 
aesthetic value fo the product. Alternatively, ammonium iron citrate may 
be used instead of said chelated iron and copper sulfate. 
Examples of the amino acids include naturally occuring L-amino acids. 
Preferably, L-amino acid mixture prepared from hoof hydrolysates of a 
cattle or a horse is used. 
The organic neutral liquid fertilizer of the invention may contain a trace 
element (e.g., Mn, Fe, B, Cu, Zn, Cl, etc.) in addition to the above 
ingredients. 
Organic acids which may be mentioned include citric acid, acetic acid, 
malic acid, fumaric acid, and the like. 
The first aspect of the invention is to provide an organic neutral liquid 
fertilizer which does not acidify soil. Another aspect of the invention is 
to provide a process of said fertilizer wherein explosive heat of 
neutralization can be quenched by conducting the reaction of a strong acid 
and a strong alkali in an aqueous organic acid solution. The generation of 
explosive heat of neutralization may effectively be prevented by the 
following procedure: A portion of the amount intended to be used of 
phosphoric acid, normally about 1/3 in the case of a 200 l reactor is 
used, is first dissolved in an aqueous solution of an organic acid at room 
temperature. Then, 1/3 of the amount of potassium hydroxide is added 
portionwise to the solution with stirring while keeping the temperature 
below 60.degree. C. After the addition of potassium hydroxide is completed 
and when the temperature of the mixture rises to 90.degree. C., 1/3 of the 
amount of urea is added to the mixture all at once with stirring, which 
decreases the temperature rapidly to 50.degree.-60.degree. C. Thus, loss 
of nitrogen due to vaporization can also be prevented. The generation of 
explosive heat of neutralization from the reaction between liquid 
phosphoric acid and potassium hydroxide may thus be quenched through the 
use of organic acid and urea. The above procedure may be repeated twice 
more. The frequency of the repitition of the procedure depends on the 
volume of the reactor used and the ability of the cooling apparatus of the 
reactor. In the case a 200-300 l reactor is used, thrice repititions of 
the procedure are required. 
In the procedure as described above, phosphoric acid, potassium hydroxide, 
and then urea are added in this order. However, the order of the addition 
may be varied and the order of phosphatic acid, urea, and then potassium 
hydroxide, may also be possible for preventing the generation of explosive 
heat of neutralization. 
As described above, the present invention provides a safe process for 
preparing an organic neutral liquid fertilizer. In the manufacturing 
process of the fertilizer, the generation of explosive heat of 
neutralization can be quenched according to present invention. 
Furthermore, a maximum temperature in the manufacturing process of the 
fertilizer is kept below 90.degree. C. at which evaporation of nitrogenous 
ingredient is prevented, thus providing an organic neutral fertilizer 
containing a high concentration each of individual components N, P, K. The 
organic neutral liquid fertilizer of the invention prevents soil from 
acidification, facilitates the absorption of nutrients by plants and 
increases the crop yields because of less damage on plants by insects or 
diseases. Since the fertilizer does not acidify soil, the fertilizer may 
serve to conserve the environment.

EXAMPLE 
The present invention will be illustrated in detail by the following 
Examples which are not intended to limit the scope of the invention. 
EXAMPLE 1 
1 kg of citric acid was added with stirring to 100 l of water in a 200 l 
enameled tank equipped with a stirrer, a thermometer and a cooling 
apparatus. A total of 18 kg of 75% liquid phosphoric acid was then added 
in 1 kg portions with stirring to the citric acid solution (17.degree. C.) 
over a period of 30 minutes. The temperature of the mixture rose to 
28.degree.-30.degree. C. A total of 17 kg of potassium hydroxide flakes 
was added in 1 kg portions with stirring to the mixture over a period of 
30 minutes while keeping the temperature below 60.degree. C. After the 
addition of potassium hydroxide was completed, the temperature of the 
mixture rose to 90.degree. C. When 20 kg of urea was added all at once to 
the mixture, the temperature of the mixture decreased rapidly to about 
40.degree. C. Then the addition of 18 kg of liquid phosphoric acid, 17 kg 
of potassium hydroxide and 20 kg of urea were repeated twice more. 2 kg of 
sodium alginate and 0.2 kg of a mixture of L-amino acids prepared from 
horse hoof hydrolysate were then added gradually to the mixture to impart 
viscosity. Separately, 800 g of chelated iron was dissolved in 5 l of warm 
water and to this solution, 400 g of copper sulfate was added. The two 
mixtures were then combined to give a viscous moss-green liquid 
fertilizer. The pH of the product was about 7.0. 
EXAMPLE 2 
1 kg of citric acid was added with stirring to 85 l of water in an enameled 
tank as described in Example 1. A total of 18 kg of liquid phosphoric acid 
was then added gradually in 1 kg portions with stirring to the above 
solution. After stirring thoroughly 20 kg of urea was added all at once to 
the mixture. When urea was dissolved completely, a total of 17 kg of 
potassium hydroxide was added in 1.7 kg portions with stirring. Heat of 
neutralization elevated the temperature of the mixture to about 75.degree. 
C. During continuous stirring for about 25 minutes, the temperature was 
decreased to about 50.degree. C. when liquid phosphoric acid was added 
again to the mixture. The addition of liquid phosphoric acid, urea, and 
potassium hydroxide was repeated as above. Thereafter, sodium alginate, 
amino acid, chelated iron and copper sulfate were added to the mixture as 
in Example 1. The resulting product, a neutral liquid fertilizer, was a 
viscous moss-green mixture. 
The content each of N, P and K of the product was about 12%, and such 
content was considerably high. The pH of the product was about 7.0.