NL192984C - Method of feeding plants, especially in substrate cultivation. - Google Patents

Description

1 192984

Method of feeding plants, especially in substrate cultivation

The invention relates to a method of feeding a plant, in particular in substrate cultivation, in which an aqueous nutrient solution containing the nutrient elements nitrogen, phosphorus, sulfur, potassium, calcium and magnesium is prepared and administered to the plant, in which method for the preparation of said nutrient solution use is made of a set of seven concentrated main solutions containing said nutrient elements, which solutions in water are mixed in amounts adapted to a predetermined nutrient requirement of the plant, these seven concentrated main solutions being a first to one seventh concentrated solution contains, respectively, of calcium nitrate, magnesium nitrate, ammonium nitrate, nitric acid, a sulfate compound, a phosphate compound and a basic potassium compound.

In hydroponic cultivation, crops are grown in a recirculating nutrient film or on a neutral substance that does not contain any natural nutrients and which allows the roots to develop and retain capillary water. The nutrient is applied to the plant in an aqueous solution, for example by means of a drip irrigation system, and contains nitrogen, phosphorus, sulfur, potassium, calcium, and magnesium ions. To obtain this nutrient or nutrient solution, concentrated aqueous solutions containing those nutrients are used. The required amounts of nutrients are offered to the plant in very low concentrations.

In practice, use is usually made of two separate storage vessels in which the horticulturist applies a solution of the necessary nutrients which he has prepared, a hundred times concentrated. The composition of the nutrient supplied to the plant is determined on the basis of the crop to be grown and the quality of the water used. On the basis of the composition thus determined, depending on the growth stage in which the plant is located, a certain amount of solution is taken from each storage vessel, which is then diluted with water and applied to the plant.

In practice, the horticulturist usually uses solids to prepare both concentrated solutions, which he dissolves in water. Since these solids always contain a small percentage of insoluble constituents, contamination of the supply line to the plant occurs, causing the risk of the supply line becoming blocked. Furthermore, dissolving the solids takes a lot of time and energy.

To avoid the risk of clogging of the supply lines, NL-A-8401261 proposes to make concentrated solutions of known solids and, before preparing the aqueous nutrient solution for the plants, to remove the insolubles from these concentrated solutions, for example by filtration . In the method according to NL-A-8401261, seven concentrated solutions are used for the preparation of the aqueous nutrient solution. These seven concentrated solutions contain calcium nitrate and ammonium nitrate, respectively; magnesium nitrate; potassium nitrate and nitric acid; potassium bisulfate; dipotassium phosphate; ammonium nitrate; and potassium carbonate. In addition to these seven concentrated solutions, a separate nitric acid or phosphoric acid solution must be provided, and under certain conditions also a solution of a base, in order to control the pH of the dilute nutrient solution. A further drawback of the method according to NL-A-8401261 is that, as can be seen from page 4, lines 3 to 4, the range of different nutrient solutions that can be realized with the seven concentrated solutions from NL-A-8401261 is quite limited. is. In particular, these two lines indicate that a slightly modified set of concentrated solutions is required if this feeding system is to be used for soil cultivation as well.

The object of the invention is to provide a method of feeding plants which makes it possible to realize a greater number of different combinations of the nutrient elements in the nutrient solution, and this only by using seven different concentrated main solutions.

A method according to the invention is therefore characterized in that as said fifth to said seventh concentrated solution, use is made respectively of a concentrated solution of sulfuric acid, phosphoric acid and potassium hydroxide.

It has been found that this particular choice of the seven main solutions provides greater flexibility in formulating the aqueous nutrient solutions and additionally requires no additional acid or base to control the pH.

A preferred embodiment of a method according to the invention is characterized in that said concentrated solutions are each individually dosed continuously in a water pipe leading to the plant. As a result, the dilution and neutralization take place directly in the supply line to the plant 192984 2 and intermediate storage is not necessary.

The invention further relates to the use of concentrated solutions of calcium nitrate, magnesium nitrate, ammonium nitrate, nitric acid, a sulfate compound, a phosphate compound and a basic potassium compound, respectively, according to the invention, in particular for preparing an aqueous nutrient solution for the feeding plants in substrate cultivation, characterized in that as sulfate compound, phosphate compound and basic potassium compound use is made of sulfuric acid, phosphoric acid and potassium hydroxide, respectively.

The invention will now be described in more detail with reference to an exemplary embodiment and with reference to the drawing, in which the figure shows an example of an apparatus for carrying out a method according to the invention. It will be clear that the invention is not limited to the exemplary embodiments described below and that several alternatives are possible within the scope of the invention.

In substrate cultivation, the nutritional elements for the plant to be grown are added to the plant in an aqueous solution. The nutrient supplied to the plant always contains nitrogen (NO3 "), phosphorus (H2PO4), sulfur (SO4S2 '), potassium (K +), calcium (Ca2 *) and magnesium (Mg2 +) containing ions.

A feeding schedule has been drawn up for each plant in which the concentration of each of the ions mentioned is predetermined. These feeding schedules have been drawn up, for example, by the Horticultural Test Station in Naaldwijk (the Netherlands) and made available to the gardeners.

In order to compose this nutrient, a number of substances which are always present as concentrated solutions are used. These substances are potassium hydroxide (KOH), nitric acid (HN03), phosphoric acid (H3PO4), sulfuric acid (H2SO4), ammonium nitrate (NH4 NO3), magnesium nitrate Mg (NO3) 2 and calcium nitrate Ca (NO3) 2. The KOH contains K + ions while the HN03 contains H3PO4 and H2S04, NO3 ', H2PO4' and SO42 'ions which are necessary ions for the nutrition of a plant. After all, these substances can be dissolved as follows: 25 KOH 52 K + = OH 'HN03 yes H + + no3-H3P04 52 H + + h2po4-NH4 N03 52 nh4 + + no3-Ca (N03) 2 52 Ca2 + 2N03 30 Mg (N03) 2 52 Mg2 + + 2N03 '

Starting from these substances, the necessary ions, being K +, NO3 ", H2PO4", SO42 ", NH4 +, Ca2 + and Mg2 +, can be obtained for feeding the plant.

A storage solution always contains a concentrated solution of the substance in question.

Although the substances can now be present either as a lye or as an acid and in a concentrated solution, the neutralization takes place in a diluted state, when these components are mixed together in a pipe, so that no precipitation occurs and no disturbing heat development during the neutralization. The acids and lyes are the most basic options for forming nutrients. Nature is such that the plants need a large amount of nitrate (NO3) ions 40 for their nutrition. From an economic point of view it is therefore advantageous to work with very "rich" nitrate solutions, namely Magnesium as Magnesium Nitrate, Ammonium as Ammonium Nitrate and Calcium as Calcium Nitrate.

In practice, seven raw materials are used in which the nutrients are present in solution. These seven raw materials can be divided into three groups: 45 1. ACIDS: - nitric acid HN03 [H + + N03 ·) - sulfuric acid H2S04 [2H + + S042-) 50 - phosphoric acid H3P04 [H + + H2P041

2. BASE: - potassium hydr KOH

oxide tK "+ OH] 55 3. Neutral - calcium nitrate Ca (NO3) 2 solutions: [Ca2 + + 2NO3] 3 192984 - magnesium- Mg (NO3) 2 nitrate [Mg2 + + 2N03 '] - ammonium (NH4 NO3) nitrate [ NH4 + + IMOg ']

All these raw materials are included in table A. For each of these raw materials, the content 10 (in%) in an aqueous solution, the crystallization point, the nutrients in wt. % and in mol / kg. The acid / base is also given for the acids and bases.

The concentrations of acids and bases are determined in such a way that in any feeding scheme there is a balance between the acid (H +) and base (OH) input in mmol / l in the final nutrient liquid.

The essence of the method according to the invention is that there is no excess of H + or OH 'ions in the irrigation system, because a neutralization reaction has taken place.

The raw materials mentioned were chosen for a number of reasons given below.

Nitric acid, phosphoric acid, sulfuric acid and potassium hydroxide: - these substances are chemically pure products, contain only minimal amounts of impurities 20 - these substances do not contain insoluble particles, so they do not block the irrigation system - these substances contain simple nutrients, provide more possibilities for correct composition of nutrient schedules - the nutrient contents are as high as possible, without compromising the neutralization principle - even at low temperatures these substances will remain liquid and clear (crystallization point below 0 ° C).

Calcium nitrate, magnesium nitrate and ammonium nitrate solutions: These are neutral solutions, do not contain any additional H + or OH 'ions, and therefore do not affect the neutralization principle of the invention. The solutions are clear and free of insoluble particles, and contain only small amounts of impurities. The choice as nitrate solutions has different backgrounds: - the nitrate requirement of plants is great - the solubility of nitrate salts is very high - the active substance concentration is high.

35 The figure shows seven storage tanks 1 to 7. Each storage vessel is connected by means of a respective tap 8 to 14 to a pipe 15 to which the water pipe is connected by means of a tap 16 and which runs to the plants to be fed. The cranes can be operated either manually or by means of a computer in whose memory drivers for feeding one or more plants can be stored. The water pipe 15 leads to a series of drippers 17 located above or in the substrate 19 where the plant 18 is grown.

It is also possible, when the gardeners already have the two storage vessels (known method), to supply these storage vessels with concentrated solution of the above-mentioned substances.

Starting from these substances, it is now possible to prepare the nutrient suitable for that plant for each plant. Tables B and C illustrate a feeding schedule for strawberries in recirculating water and rock wool anemone, respectively. The ions are listed in the top row of each table and the various basic substances are listed in the first column. The second row serves to display the values (in mmol / l) of the ion concentrations for the respective plant. For example, for strawberries in recirculating water, there is 10 mmol / l NO3 ', 1.25 mmol / l H2PO4', 1.125 mmol / l S042 ', 0.5 mmol / l NH4 +, 5.25 mmol / l K +, 2, 75 50 mmol / l Ca2 + and 1.25 mmol / l Mg2 + in ion concentration necessary. These values are known per se and are made available to gardeners by the horticultural companies. The last two columns represent the OH 'and the H * ions, respectively.

Using the matrix given in the table, the concentrations of the various substances can now simply be calculated. In the example of strawberries in recirculating water, the 55 ion concentrations given above are shown in the second row of Table II. In order to realize the neutralization reaction, the concentrations of OH 'and H + ions must be the same. The OH 'ions can only come from KOH. Since there must be a concentration of 5.25 mmol / l of K + ions for strawberries 192984 4, there will therefore also be 5.25 mmol / l of OH 'ion concentrations. This number is entered in the appropriate box. Since there is 5.25 mmol / l of OH 'ions, 5.25 mmol / l of H + ions is also needed for equilibrium (neutralization principle).

The H2PO4 ions can only be supplied by the phosphoric acid, so that 1.25 mmol / l 5 phosphoric acid must therefore be taken. This then gives 1.25 mmol H + ions per liter. The same reasoning applies to the S042 'NH + 4, Ca2 + and Mg2 + ions, respectively, which only come from the sulfuric acid, ammonium nitrate, calcium nitrate and magnesium nitrate, respectively. In the matrix, therefore, the concentrations are entered at their respective places.

The amount of nitrate has yet to be determined. This is done as follows. Since there are 2NO3 'ions for one Ca2 + ion with calcium nitrate and 2.75 mmol / l of calcium nitrate is necessary for the Ca2 + concentration, 2 x 2.75 = 5.5 mmol / l nitrate must be taken for the contribution to NO3 ions, 1 mmol / l calcium nitrate dissolved in water gives 1 mmol / l Ca2 + and 2 mmol / l nitrate. Analogously, there are 2NO3 ions for one Mg2 + ion. 1.125 mmol / l magnesium nitrate is required, which gives 2.25 mmol / l nitrate. With ammonium nitrate, there is one NO 3 'ion for one NH 4 + ion such that 0.5 mmol / l ammonium nitrate is added. All this already gives 5.25 + 2.25 + 0.5 = 8.25 mmol / l concentration of NO3 * ions. However, this is not enough as strawberries require 10 mmol / l NO3 '. The remaining amount, i.e. 10 - 8.25 = 1.75 mmol / l, must therefore come from the nitric acid. All these values are shown in the NO3 'column of Table B.

It is now possible to check whether this matrix is correct. The last two columns are used for this.

As already mentioned, the 5.25 mmol / l of OH 'ions only come from the potassium hydroxide in such a way that this number can be filled in without further ado. The H + ions come from the sulfuric acid, the nitric acid and the phosphoric acid. Sulfuric acid gives 2 x 1.125 = 2.25 mmol / L, nitric acid gives 1.75 mmol / L and phosphoric acid gives 1.25 mmol / L as already determined. Adding these three numbers gives: 2.25 + 1.75 + 1.25 = 5.25 mmol / l, being the required concentration of H + ions.

25 Table C, in which an analogous calculation is given for anemone in rock wool, is given for illustrative purposes. Table C also shows how simply the various concentrations can be determined using the matrix.

To convert the number of mmol / l of the product into the number of kg in the hundred times concentrated stock solutions when working with the known two storage vessels, the following formula can be used: 0.1 x K x m x = kg. product / m3 where K = the number of mmol / l of the product 35 m = the molecular mass of the product L = the percentage by weight of the product

Table B requires 1.25 mmol / l H3PO4, which is converted 0.1 x 1.25 x 98 x = 20.76 kg of phosphoric acid 59% per 1000 l of stock solution.

In the same way, the other quantities are determined and added to the two storage vessels.

Based on these seven substances mentioned above, a nutrient for any plant to be grown can therefore be composed. Moreover, with this limited number, a feeding schedule can be made that is flexible over time, since the ion concentration in the nutrient can vary and can therefore be adapted to the growth stage of the plant. Since any arbitrary ion concentration can be obtained by using the method according to the invention, it is thus also possible to vary this concentration over time for a particular plant.

The substances used are present in very pure solutions with these simple acids and lyes (99% purity), so that the purity of the nutrient that goes to the plant is very high. The use of seven raw materials also has the advantage of limiting the product range.

Since all these substances are dissolved in water and since the ion concentration of the water 50 differs from place to place, it is usual to check the final concentration of the nutrients in the water in the usual manner. Depending on the measured values, it is then possible to make any corrections to the concentration.

5 192984

TABLE A

PRODUCT CONTENT <RISTALLISA- FOOD, FOOD / BASE

% TIEPOINT SUBSTANCES IN SUBSTANCES

5% by weight MOL / kg

Nitric acid 38 - 33 ° C N (nitrate) 8.4 6 mol / kg NO 3 6 mol / kg H

Sulfuric acid 59 - 38 ° C S03 48.1 6 mol / kg S04 12 mol / kg H

10 -

Phosphoric acid 59 -18 ° C P2Os 45.7 6 mol / kg H2PO4 6 mol / kg H

Potassium hydr 33-50 ° C K20 27.9 6 mol / kg K 6 mol / kg OH

oxide 15--

Calcium nitrate 52 + 4 ° C N (nitrate) 8.8 3.2 mol / kg Ca

Approx. O 17.7 6.4 mol / kg NO3 20 Magnesium- 37 - 14 ° C N (nitrate) 7 5 mol / kg NO3 nitrate

MgO 10 2.5 mol / kg Mg 25 Ammonium- 52 + 2 ° C N (nitrate) 9 6.2 mol / kg NH4 nitrate N (ammonia) 9 6.2 mol / kg NO3

30 TABLE B

CROP: Strawberry in recirculating water NO3- H2P0 £ 042 'NH4 + K + Ca2 + Mg2 + OH * H + 35 - - - - - - CALCULATE COMPOSITION mmol / l FERTILIZER mmol / 10 1.25 1.125 0.5 5.25 2.75 1.125 5.25 5.25

Itr 40 ____

Phosphoric acid H ++ / ¾¾¾, 25 ^^ 1.25 ^ _pp

Ammonium nitrate 0.5 (nh ^ no »> _ mmT wmzm._pUt

<* r + ** u ^ _É1ËI

Potassium hydroxide (K + 5.25

Claims (3)

192984 6 TABLE B (continued) CROP: Strawberry in recirculating water 5 Calcium nitrate (Ca2 + 5.5 ^^^^^^^^ 2.75 / ¾¾¾ ^ _w ^ wm m mm Sulfuric acid (2H ++ ^^^^^^ 1.125 ^ ^^ 2,25 TABLE C CROP: Anemone in rock wool i5 N03- H2P04S042 'NH4 + K + Ca2 + Mg2 + OH' H + COMPOSITION COMPOSITION mmol / ltr FERTILIZER mmol / 13,0 1,5 1,25 0,5 6,5 4, 0 1 6.5 6.5 20 (tr Phosphoric acid H ++ ^^ p1.5 25 Nitric acid H + + 2.5 y | pp2.5 Ammonium nitrate 0.5, n (NH ^ N ° 8) __ i »Potassium hydroxide (K + + Calcium nitrate (Ca2 + + 8 mm-mm. M._ 40 Sulfuric acid (2H ++ ^^ iÉ ^ 1-25 ^ ¾¾¾5 ïï_ «M i— Él 45 Conclusions A method of feeding a plant, in particular in substrate cultivation, in which an aqueous nutrient solution containing the nutrient elements nitrogen, phosphorus, sulfur, potassium, calcium and magnesium is prepared and administered to the plant, in which method of preparation of said 50 nutrient solution using a set of seven concentrated main solutions containing said nutrient elements, which solutions in water are mixed in amounts adapted to a predetermined nutrient requirement of the plant, these seven concentrated main solutions containing a first to a seventh concentrated solution respectively of calcium nitrate, magnesium nitrate, ammonium nitrate, nitric acid, a sulfate compound, a phosphate-55 compound and a basic potassium compound, characterized in that as said fifth to said seventh concentrated solution, respectively, use is made of a concentrated release of sulfuric acid, phosphoric acid and potassium hydroxide. 7 192984 Method according to claim 1, characterized in that said concentrated solutions are each individually dosed continuously in a water pipe leading to the plant. 3. Use of concentrated solutions of calcium nitrate, magnesium nitrate, ammonium nitrate, nitric acid, a sulfate compound, a phosphate compound and a basic potassium compound, respectively, as a combined set in a method according to claim 1 or 2, in particular for preparing a aqueous nutrient solution for feeding plants in substrate cultivation, characterized in that as sulfate compound, phosphate compound and basic potassium compound use is made of sulfuric acid, phosphoric acid and potassium hydroxide, respectively. Hereby 1 sheet drawing