Mixtures and method for use in aqueous cultures

The subject of the invention is a method of stimulating the development of the population of marine life forms in closed aquatic ecosystems. The subject of the invention is, in particular, a method in which controlled release mixtures are used to release foodstuffs into closed aquatic ecosystems, such as ponds, lakes, river catchments and other aquatic environments, to accelerate the growth of phytoplankton algae populations in water and thus for population development of marine life forms.

One of the techniques considered so far important in the management of closed aquatic ecosystems, such as ponds, lakes, river basins, etc. was fertilization, especially used to accelerate the development of phytoplankton algae in water.

Plant plankton is the basis of the food chain in these aquatic environments, so it is necessary to increase fish production in this type of closed aquatic ecosystems. In addition, it has been shown that appropriate fertilization techniques perform a whole range of other useful functions, including inhibiting the growth of troublesome water weeds in enclosed water bodies and improving water quality.

For most freshwater ponds and lakes, it is believed that phosphorus should be the primary nutrient in the fertilizers used. Including nitrogen and other nutrients in the composition has also proved beneficial. However, phosphorus is a nutrient that limits the growth of phytoplankton algae inflorescences. Therefore, most ponds require frequent addition of phosphorus-rich fertilizers to maintain the phytoplankton inflorescence layer throughout the entire production cycle. Joints require a high frequency of phosphorus fertilization, because active phosphorus is absorbed very quickly by sludge or absorbed by phytoplankton. Phosphorus absorbed by the sludge can only be released back into the water in small amounts, because the interface between oxygenated water and sludge is a barrier between the sludge and higher surface waters Over the years, fertilization methods for ponds and lakes have undergone various stages of development. Recent changes are the result of attempts to reduce the growing costs of fertilization and concerns about the negative impact of fertilizers on the environment.

Early fertilization programs consisted simply of spreading over shallow areas of the pond or spreading from the boat on the border of shallow water granular nitrogen phosphorus potassium (NPK) fertilizers such as mixtures 8-8-2 or 20-20-5. Later studies showed that placing fertilizers on an underwater platform gave the same results with less fertilizer consumption and was less time consuming. It turned out that under the action of wind and waves, nutrients from fertilizers reached all corners of the pond and at the same time were more easily available for phytoplankton and were less bound by sludge. One well-positioned platform could support a pond of up to 6 hectares. Subsequent discoveries have shown that ponds that already have a certain fertilizing history only require phosphorus fertilization, which has significantly reduced fertilization costs. Despite the proven efficiency of fertilization platforms, only a few pond owners used them in practice. The biggest breakthrough in the use of fertilizers in fish ponds occurred after the introduction of liquid fertilizers.

In addition to superiority over granular mixtures in terms of increased fish efficiency, liquid fertilizers also had a number of other very attractive features. Liquid fertilizers, which were characterized by the fact that they were almost completely soluble in the water of a pond or lake, could be used effectively at lower feed rates, compared to previously used granular products, provided they are used correctly. They were also safe and easy to use and relatively economical to use.

For these reasons, ordinary soluble fertilizers were previously used cleanly in ponds and lakes to increase the concentration of inorganic nutrients, which in turn promoted faster growth of phytoplankton and ultimately resulted in increased fish and / or crustacean production in aquatic ecological systems. The current practice consists in using liquid fertilizers or ordinary, soluble granular fertilizers such as urea, ammonia, phosphates, ammonium polyphosphate, ammonium sulfate, potassium sulfate, etc. and feeding them in closed water ecosystems (ponds, lakes) throughout the entire production cycle . Maintaining fertilizer availability requires frequent fertilizer administration.

However, prior techniques have not solved problems arising on the one hand from the need for constant availability of nutrients to ensure phytoplankton growth, on the other hand from the fact that products previously reported for use in aquaculture provided only nutrients for a short period after use.

Consequently, to date, this type of fertilizer should have been applied 8 to 10 times during one production cycle, which allowed to maintain a constant growth of phytoplankton inside a large closed aquatic ecosystem such as a pond or lake. In the event of non-compliance with the fertilizer application plan, it was observed that fish production in the environment decreased. Of course, fertilizer application schedules with such frequency were costly, inefficient and time consuming.

As a result, it was recognized that the use of inorganic, granular fertilizers in water cultures is expensive and inefficient due to the rapid dissolution of most fertilizer preparations, leaching them into aquatic ecosystems and the inability to effectively use nutrients.

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The object of the invention is to develop such a composition of mixtures and such methods of application that will eliminate the problems and disadvantages of hitherto known fertilization techniques used in aquaculture.

A further goal is to develop a method of applying fertilizers in closed aquatic ecosystems that ensure the constant presence of appropriate nutrients that support phytoplankton growth in these aquatic environments over a longer period of time, without the need for repeated feeding.

Another object of the invention is to develop fertilizer mixtures that can be used once in closed aquatic ecosystems such as ponds, lakes, river basins and other aquatic environments, with lower dosage rates than previously used products to achieve satisfactory growth of the phytoplankton population in this environment over a longer period period of time.

A further goal is to develop a method and mixture for effective fertilization of fish ponds, lakes, river basins and similar water environments characterized by greater efficiency and cost reduction compared to the methods used so far.

The above and further objectives of the present invention have been accomplished by developing fertilizer mixtures with controlled release rates, from which individual fertilizers are released at a controlled rate over a longer period of time, in order to improve the state of closed aquatic ecosystems such as ponds, lakes, river basins and the like aquatic environments. The inventors have developed this type of material with controlled release rates for individual products to be able to delay the process or reduce the rate of nutrient delivery in an aqueous environment.

Until now, fertilizer technology with controlled release rate has been widely used for a long time in agriculture and horticulture. The use of this technology includes regulating the supply of nutrients to plants, i.e. fertilizers, as well as chemicals that control breeding, e.g. herbicides, insecticides, fungicides and the like, in a manner that maximizes the yield of cultured plants and minimizes the potential negative effects caused by overdosing and / or extends the time at which the appropriate dose of the product reaches its target.

However, with the current state of the art, this type of fertilizer mix was not used in aquaculture.

An example of the benefits of using controlled-release fertilizer mixtures in aquaculture is to reduce the entire pond fertilization process to one or two-stage operations within each production cycle. In addition, the use of fertilizer mixtures with controlled release rates allows the use of low rates of fertilizer feeding and allows the use of pond systems with moderate water exchange. The use of controlled-release fertilizer mixtures in pond waters is absolutely safe, and in addition, mixtures of this type are commercially available.

Thus, the essence of the present invention is to use controlled release fertilizer mixtures to release nutrients in enclosed aquatic ecosystems such as ponds, lakes, river basins and other aquatic environments to accelerate the growth of phytoplankton algae populations in water in a more efficient manner and with more efficient the use of financial outlays compared to the fertilization techniques used so far.

Generally speaking, the essence of the present invention is the use of controlled release fertilizers in closed aquatic ecosystems. The fertilizer preparation with controlled release rate is formed on the basis of macromolecular material constituting the nucleus of the preparation and releasing substance chemically associated with the nucleus of the preparation or constituting its outer coating. The content of the releasing substance is selected so as to ensure a slow release of the substance forming the nucleus of the preparation into the surrounding aquatic environment in quantities sufficient to cause population growth

184 498 phytoplankton to develop marine life in water systems in the long term.

The term 'marine life forms', whose development in the aquatic environment is supported by phytoplankton algae, covers a whole range of freshwater fish, marine fish and those living in brackish waters, as well as crustaceans such as shrimp, molluscs, crayfish and the like. The expression "marine life forms" used in the description of the present invention includes all these forms of aquatic life. Thus, the use of controlled-release fertilizers as nutrient delivery systems to enrich aquatic phytoplankton populations in the production of aquaculture in lakes and ponds is essential for a variety of enterprises such as: fishing ponds, production fish farms for various species of fish, e.g. toothed fish, crayfish and shrimp fish farms, tropical fish farms, exotic farms such as alligators, eel farms, both high-quality production farms and new farms, fish breeding ponds and many others.

Suitable fertilizer mixtures used in the present invention are referred to in agricultural and horticultural terminology by various terms such as: controlled release fertilizers, controlled availability, slow release fertilizers, delayed release fertilizers, etc. - all these terms are included in the present description of the invention the term "rate-controlled fertilizers".

The rate-controlled release fertilizers used in the present invention are granular fertilizers that have been formed as a reaction product or coating product. An example of granular fertilizers with a controlled release rate constituting a chemical reaction product and used in the present invention are urea and formaldehyde reaction products such as urea-formaldehyde, methylene ureas, compositions of MDU / DMTU compounds described, for example, in the US patent LIS Patent 4,378,23 S titled "Macromolecular blend fertilizers with controlled release rate ', whose disclosures have been incorporated into the present invention as reference and reaction products of urea with other aldehydes such as isobutilidene diurea (IBDU), guanylureas, crotonylidene diurea (CDU) and other reaction products such as oxamide and melamine fertilizers, inorganic metal complexes such as phosphate magnesiumammonium (megamp), magnesium potassium phosphate and the like.

The coated release rate fertilizers used in the present invention are coating products for granules of soluble fertilizer, which granules are the nucleus of the formulation (substrates), a water-insoluble or semi-permeable coating or such a release material that limits or regulates the rate of water penetration into soluble fertilizer nuclei and regulates the rate of release of dissolved fertilizer from inside the granules to the external environment.

In priority applications of the present invention, a coating or releasing material in an amount of about 0.5 to 35% by weight was used on the core material of the formulation.

Examples of coated granular fertilizers with a controlled release rate may be fertilizers in which sulfur was used as the coating material, as well as those in which wax and / or polymer material was used, and mixed products coated with a multilayer coating of sulfur and polymer. The following polymers have been found to be suitable for use in the present invention: polyvinyl chloride, polyvinylidene chloride, polyethylene, polypropylene, polyethylene terephthalate, polyurethane, polyamides, copolymers of dicyclopentadiene and vegetable oils such as linseed or soybean oil, copolymeric blends and vinyl chloride with monomer predominate ethylenically unsaturated comonomers, salts of sulfonated elastomers and mixtures thereof. In addition, the use of polymer coatings described in US Patents 4,657,576 under the title "Controlled granular fertilizer mixtures and the method of obtaining them", 5,089,041 under the title "Encapsulated fertilizers with low release rate", 5,300,135 under the title " Abrasion resistant coatings used for fertilizers 'and 5,219,465 after the title' Sulfur-coated fertilizers and their process

184 498 preparation ', the disclosures of which are incorporated into the present invention by reference.

In addition, the addition of oxidizing agents such as peroxides, nitrates and mixtures thereof to the controlled release fertilizer mixtures of the present invention, or the inclusion of such oxidants in the composition of controlled release fertilizer mixtures has proved to be very beneficial. Oxidizing agents recommended for use within the present invention include calcium peroxide, sodium peroxide, potassium peroxide, calcium nitrate, sodium nitrate, potassium nitrate, ammonium nitrate, magnesium nitrate, and mixtures thereof.

The incorporation of microelements such as iron, zinc, boron, calcium, magnesium, sulfur, manganese, copper, molybdenum, cobalt and mixtures thereof into the nucleus of the fertilizer formulation containing nitrogen, phosphorus and / or potassium has also proved beneficial. It is also possible to separately develop a preparation containing trace elements and attach to the mixtures constituting the subject of the invention. The microelements themselves can be prepared separately or all together. Particularly beneficial for aquatic cultures has been the inclusion in the blends or the addition of micronutrients in the form of chelates or salts such as nitrates, phosphates, oxides, chlorides, borates, molybdates, sulfates and mixtures thereof.

Requirements for the production of fertilizers for aquaculture differ significantly depending on the type of harvest, water quality and environmental conditions. The most frequently suggested indicators for nitrogen, phosphorus and potassium per production cycle are:

nitrogen (N) - 0 - 100 lbs per acre, phosphorus (P2O5) - 0 - 800 lbs on a surface of potassium (K2O) - 0 - 50 lbs on an surface of air

Materials constituting the nucleus of fertilizer preparations are prepared in a proper way so that they are released for a period of 1 to 12 months, depending on environmental and production parameters. Typical materials that form the nucleus of fertilizer preparations used in the southern US are prepared so that they then release over a period of 8 to 9 months.

The following examples have been developed to illustrate the priority applications of the present invention. Recommended mixtures and methods of their application are presented as well as comparative assessment in relation to preparations and methods used in the prior art. All percentages given below are weight percentages except when specified otherwise.

Example I. Tests were carried out at the Auburn Unicersity Fisheries Research Unit (Auburn University Fisheries Research Unit) in Auburn, Alabama. The first test involved six 0.04 ha ponds and the other one 0.022 ha pond. These ponds were shallow, their depth ranged from 0.25 m near the banks to 1.5 m at the height of the downpipes. The ponds were on average 1 m deep. The water level was maintained by the weekly addition of soft water with a low content of nutrients, coming from a nearby reservoir located on a wooded watershed to increase the quality of water in ponds, several types of actions were taken. The inlet pipes were covered with heavy raw material to prevent wild fish or harmful invertebrates from entering. Like last year, the joints were completely drained and allowed to dry thoroughly. High clumps of ground grasses were sprayed with herbicide ^^ hos ^ e) or removed manually before refilling the pond. Plastic screens were installed in all down pipes to prevent fish from accidentally escaping, and in some ponds extension cords (10 cm diameter PVC pipe pieces) were attached to the down pipes to maintain the same volume in all ponds. Agricultural lime in the amount of 600 kg / ha was spread on the bottom of the ponds.

Wooden box-shaped platforms were constructed (internal dimensions 114 cm x 60 cm x 9 cm deep) for placing samples of controlled release fertilizer (hereinafter referred to as CRF - controlled release fertilizer) and samples of soluble granular instant release fertilizer (hereinafter - grain fertilizer 184 498 Jan), then these platforms were moored to existing platforms so that they were about 30 cm under water. The experiment with granular fertilizer samples was based on a "standard" average application of 9 kg P2Os / ha and ten applications per season. The joints were freely divided into three experimental groups. The first of these was a control group in which granular fertilizer was used as the source. In the other two groups, CRF fertilizer samples were used in the proportions 100% and 50%, respectively.

The source of nutrients for soluble granular fertilizer samples was ammonium nitrate (33.5% N), triple superphosphate (46% P2O5) and potassium carbonate chloride (60% K2O). Nutrients for CRF samples were: ammonium nitrate (33.5% N) , ammonium phosphate (11-18% N, 48% P2O5) and potassium sulfate (50% K2O)

The CRF samples used in the tests were ready-made products commercially sold as "Osmocote" brand products by the Grace Sierra Company (now Scotts Company). This product consists of small lumps (3-5 mm in diameter). Each of the lumps is covered with a controlled release coating formed from vegetable oil (e.g. linseed or soybean oil), which has been subjected to the action of diene hydrocarbon to obtain a dicyclopentadiene copolymer - a product patented by US patent 4,657,576, which we provide here for reference.

Osmocote regulated release fertilizers, which were used in these tests, had equal content of N, P2O5, K2O - 13% each; they were considered extremely suitable for use in this experiment.

On March 21, ponds in which controlled release fertilizer was applied received a single dose of 45 or 90 kg (N, P2O5, K20) / ha. Ponds using soluble granular fertilizer received a dose of 9 kg (N, P2O5, K2O) / ha on March 21, and this operation was repeated on April 5, April 18, May 9, May 30, June 21, July 20, August 20 and September 20 to determine the usage rate according to the data in the following table.

Table 1

The amount of fertilizer ingredients for three different applications in the annual season has been replicated twice.

<td rowspan="2">Experience</td><td colspan="3">Application rate (kg / ha per season)</td>

<td>N</td><td>P2O5</td><td>K₂ABOUT</td>

<td>Samples of granular fertilizer *</td><td> 90</td><td> 90</td><td> 90</td>

<td>100% CRI samples</td><td> 90</td><td> 90</td><td> 90</td>

<td>50% CRF samples</td><td> 45</td><td> 45</td><td> 45</td>

* This means 9 kg (N, P2O5, K₂O) / ha for each application.

At the end of February, all ponds were stocked with large-mouth bass (Lepomis macrochirus) and sunfish (Lepomis microlophus) in an amount of 6000 / ha or 240 fish per pond. The average weight of one fish was 1 g. Between 16 March and 13 April, in order to regulate the amount of seaweed, a total of thirteen pieces of white amura (Ctenopharyngodon idella) with a total weight of 13 g were admitted to all ponds. On May 16, twenty pieces of 11-gram young tilapia (Tilapia nilotica) were admitted to all ponds. In the first week of October, the ponds were drained, and all fish were collected and weighed to determine total production. The numbers and weight of each species of fish were recorded, and the yield and percentage of survival in this experiment were calculated - they are listed in Table 2.

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Table 2

Summary of the average value of fish production in ponds that received a standard dose of granular fertilizer (13-13-13) and a two-level dose of regulated release fertilizer (13-13-13). Each experiment was repeated twice.

<td rowspan="2">Measure</td><td colspan="3">Experience</td>

<td>samples granular fertilizer</td><td>samples CRF 100%</td><td>samples CRF 50%</td>

<td>Large mouth bass output (kg / ha)</td><td> 95</td><td> 99</td><td> 32</td>

<td>Tilapia yield (kg / ha)</td><td> 77</td><td> 63</td><td> 34</td>

<td>Yield of young tilapia and large-mouth bass</td><td> 1256</td><td> 1236</td><td> 689</td>

<td>White amur yield (kg / ha)</td><td> 281</td><td> 189</td><td> 240</td>

<td>Total yield (kg / ha)</td><td> 1709</td><td> 1588</td><td> 995</td>

<td>Average large-mouth bass weight (g)</td><td> 23,5</td><td> 26</td><td> 22,5</td>

<td>Percentage of primary fry survival</td><td> 69</td><td> 63</td><td> 22</td>

<td>Average tilapia weight (g)</td><td> 190</td><td> 124</td><td> 94,5</td>

<td>Percentage of primary fry survival</td><td> 83</td><td> 100</td><td> 75</td>

<td>Average weight of white amur (g)</td><td> 1386</td><td> 664</td><td> 873</td>

<td>Percentage survival</td><td> 67</td><td> 80</td><td> 89</td>

Using a 90 centimeter sampler, two water samples were taken from two places in each pond and placed in liter polyethylene bottles. A general water analysis was done the same day. All samples were analyzed for soluble reactive P (SRP - soluble 41 reactive P), total P (TP - total P), total) ammonia (TAN - total ammonia N), N-nitrate (N), ph and chlorophyll a . The Secchi shield and light-dark bottle measurements were also made. Every two weeks, total alkalinity and total water hardness were measured. The analyzes of SRP, TP, ph, chlorophyll, light-dark bottle, total alkalinity and water hardness were a reproduction of the procedures established by the American Society for Public Health (1992). For N-nitrate analysis, the Hach procedure (1989) was used with the modification of the Cadmium Reduction Method (Nitra Ver 5). The salicylic acid esters method was used to determine the total ammonia (TAN) content. The third sample was taken into a 125 ml polyethylene bottle and analyzed for K content by Inductively Coupled Plasma (1CP) at Auburn University Soil Research Laboratory. The detection limits were: 0.01 mg / l for SRP, 0.01 mg / l for TP, 0.02 mg / l for TAN, 0.005 for N02 - N, 0.01 mg / l for N03 -N, 0.07 mg / l for K, 0.5 mg / l for total primary productivity, 5 mg / l for total alkalinity and hardness, 5 cm for the Secchi disk depth and 0.1 unit for pH.

Measures of other useful nutrients and ionic ingredients, including P, Ca, Mg, Na, Si, Cu, Fe, Mn, Zn, B, Mo, Al, Ba, Co, Cr and Pb, were also determined by this method. The temperature in the joints was measured daily with a max / min thermometer. The results of this study are shown in Table 3.

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Table 3

Summary of variable water quality in ponds that received a standard dose of granular fertilizer (13-13-13) and a two-level dose of regulated release fertilizer (13-13-13) in 1992. Each experiment was repeated twice

<td rowspan="2">Variable</td><td colspan="3">Experience</td>

<td>samples granular fertilizer</td><td>samples CRF 100%</td><td>samples CRF 50%</td>

<td>TP (mg / l)</td><td> 0,16</td><td> 0,17</td><td> 0,09</td>

<td>SRP (mg / l)</td><td> 0,10</td><td> 0,07</td><td> 0,03</td>

<td>NO3 - N (mg / l)</td><td> 0,15</td><td> 0,17</td><td> 0,14</td>

<td>TAN (mg / l)</td><td> 0,03</td><td> 0,03</td><td> 0,01</td>

<td>Chlorophyll a (ąg / 1)</td><td> 31</td><td> 26</td><td> 20</td>

<td>pH</td><td> 9,0</td><td> 8,9</td><td> 8,8</td>

<td>Secchi visibility (cm)</td><td> 56</td><td> 54</td><td> 60</td>

<td>Primary productivity (mg O2 / 1/6 hr)</td><td> 2,2</td><td> 2,9</td><td> 1,4</td>

<td>Alkalinity (mg / l CaCO₃)</td><td> 38</td><td> 40</td><td> 39</td>

<td>Hardness (mg / l CaCO₃)</td><td> 39</td><td> 41</td><td> 39</td>

<td>Potassium (mg / l)</td><td> 3,7</td><td> 4,2</td><td> 2,6</td>

Twelve hydroponic ponds with an area of ​​0.02-0.07 ha were fertilized with samples of CRF fertilizer during a series of tests. These tests were performed on similar principles to those described above in Example 1, except that the samples of soluble granular fertilizer were replaced by samples of soluble liquid fertilizer.

Similar actions were carried out as in the previous test. Basic water samples indicated low alkalinity (&lt;20 mg / l CaCOa) in most joints. On March 17, ponds were calcified at 700 kg / ha. Samples were tested with a lower application rate (90 kg P2O2 / ha) per season compared to the conditions of the previous test. Therefore, during the second series of tests, the joints were arbitrarily divided into four experimental groups, as in Table 4.

Table 4

Amount of fertilizer ingredients per season for four different experiments.

Between April 20 and September 13, nutrients were applied six times using a liquid fertilizer sample. One-time use of the CRF sample was based on an application rate of 9 kg P2O5 / ha with ten applications per season.

Each of the experiments was repeated three times.

<td rowspan="2">Experience</td><td rowspan="2">Degree</td><td colspan="3">Application rate (kg / ha per season)</td>

<td>N</td><td>P2O5</td><td>K2O</td>

<td>Liquid fertilizer sample</td><td> 10-34-0</td><td> 26,5</td><td> 90</td><td> 0</td>

<td>50% CRF sample</td><td> 13-13-13</td><td> 90</td><td> 90</td><td> 90</td>

<td>CRF sample 25%</td><td> 13-13-13</td><td> 22,5</td><td> 22,5</td><td> 22,5</td>

<td>12.5% ​​CRF sample</td><td> 13-13-13</td><td> 11,3</td><td> 11,3</td><td> 11,3</td>

The source of nutrients for experiments with liquid fertilizer was ammonium polyphosphate (10% N, 34% P2O5). The use of liquid fertilizer consisted of diluting it in a bucket of water and spreading it evenly over the surfaces of the joints. Fertilizers

184 498 were added to all ponds on April 20. The ponds from the liquid fertilizer test group also received doses of fertilizer on May 11, June 7, June 22, July 19 and August 16.

Despite fertilization, phytoplankton developed in two ponds.

May, a decision was made to systematically drain (80% by volume), remove seaweed and algae manually, and fill all ponds again. This was done in two weeks. Because of this action existing fertilizer in ponds tested with controlled release fertilizer. Osmocote was removed and replaced with a new June 9 all ponds were again covered with lime (600 kg / ha).

At the end of February, all ponds were stocked with young fish in the scale of 6,000 fish / ha. Between March 1 and May 26, ponds were fed with white carp in the amount of 125 fish / ha. The ponds were drained on September 13-15, 1993 and then the fish was collected. All recovered fish were weighed and counted. Measurements of weight and length of all white amur were taken. For juvenile sunfish, the number of fish was estimated based on weighed and counted samples. These data were used to calculate the yield and survival percentage of adults for sunfish, young sunfish and white amur, as shown in Table 5.

Table 5

Summary of average production in ponds that received a standard dose of liquid fertilizer (10-34-0) and a three-level dose of fertilizer with controlled secretion (13-13-13). Each experiment was repeated three times.

<td rowspan="2">Measure</td><td colspan="4">Experience</td>

<td>A sample liquid fertilizer</td><td>A sample CRF (50%)</td><td>A sample CRF (25%)</td><td>A sample CRF (12%)</td>

<td>Application indicator</td><td></td><td></td><td></td><td></td>

<td>Large hassa yield (kg / ha)</td><td> 90</td><td> 99</td><td> 93</td><td> 86</td>

<td>Yield together with young (kg / ha)</td><td> 259</td><td> 233</td><td> 360</td><td> 183</td>

<td>White amur yield (kg / ha)</td><td> 147</td><td> 163</td><td> 135</td><td> 88</td>

<td>Total yield (kg / ha)</td><td> 408</td><td> 397</td><td> 495</td><td> 272</td>

<td>Average large-mouth bass (g)</td><td> 22,4</td><td> 17,9</td><td> 16,9</td><td> 17,5</td>

<td>% survival</td><td> 73</td><td> 99</td><td> 102</td><td> 90</td>

<td>Estimated weight of young (g)</td><td> 0,81</td><td> 0,76</td><td> 0,77</td><td> 0,93</td>

<td>Average weight of white amur (g)</td><td> 1405</td><td> 617</td><td> 677</td><td> 466</td>

<td>% survival</td><td> 76</td><td> 172</td><td> 104</td><td> 121</td>

In addition, water quality was assessed using the same procedures as listed in Example 1, and the results are shown in Table 6.

Table 6

Summary of average variables of water quality in ponds that received a standard dose of liquid fertilizer (10-34-0) and a three-level dose of regulated release fertilizer (13-13-13). Each of the experiments was repeated three times.

<td rowspan="2">Variable</td><td colspan="4">Experience</td>

<td>Liquid fertilizer sample (100%)</td><td>A sample CRF (50%)</td><td>A sample CRF (25%)</td><td>A sample CRF (12%)</td>

<td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td>

<td>Application indicator</td><td></td><td></td><td></td><td></td>

<td>NH4- N (mg / l)</td><td> 0,02</td><td> 0,07</td><td> 0,02</td><td> 0,02</td>

184 Table 498 continued

<td> 1</td><td> 2</td><td> 3</td><td> 4</td><td> 5</td>

<td>WELL₂ - N (mg / l)</td><td> 0,004</td><td> 0,007</td><td> 0,004</td><td> 0,002</td>

<td>NO3 - N (mg / l)</td><td> 0,23</td><td> 0,35</td><td> 0,23</td><td> 0,16</td>

<td>SRP (mg / l)</td><td> 0,06</td><td> 0,03</td><td> 0,02</td><td> 0,01</td>

<td>TP (mg / l)</td><td> 0,20</td><td> 0,24</td><td> 0,14</td><td> 0,11</td>

<td>Chlorophyll a 4 ąg / 1)</td><td> 59</td><td> 75</td><td> 66</td><td> 35</td>

<td>pH</td><td> 8,9</td><td> 9,1</td><td> 9,0</td><td> 8,7</td>

<td>Secchi visibility (cm)</td><td> 57</td><td> 49</td><td> 57</td><td> 60</td>

<td>Original productivity (mg 0211 / GHR)</td><td> 2,4</td><td> 3,2</td><td> 2,8</td><td> 2,1</td>

<td>Alkalinity (mg / l CaCO₃)</td><td> 32</td><td> 31</td><td> 32</td><td> 39</td>

<td>Hardness (mg / l CaCO))</td><td> 35</td><td> 34</td><td> 35</td><td> 44</td>

<td>Potassium (mg / l)</td><td> 2,1</td><td> 2,7</td><td> 2,7</td><td> 2,7</td>

<td>Seaweed coverage (% bottom)</td><td> 42</td><td> 21</td><td> 21</td><td> 18</td>

This study has shown that controlled release fertilizers can be used in much smaller quantities and give similar results in water quality and fish production as previous fertilization techniques. In addition, the use of controlled-release fertilizers in hydroponics has a commercially significant advantage, namely the need to fertilize only once a season. In addition, regulated release fertilizers retain valuable nutritional resources and, as demonstrated here, function efficiently in systems with moderate water exchangeability.

Although the invention has been described herein in its preferred solutions and in a rather detailed manner, it is understood that this explanation is only an example of numerous changes in the details of the composition, in the individual steps of the methods and in the compositions used will be obvious and will not depart from the heart and scope of the defined invention in the claims.

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