Home » Agrochemistry » Liquid complex fertilizers (LCF)

Liquid complex fertilizers (LCF)

By in Agrochemistry on .

Liquid complex fertilizers (LCF) are complex fertilizers that are aqueous solutions or suspensions containing basic nutrients, sometimes with the addition of microfertilizers, pesticides and plant growth stimulants.

Fertilizers

Navigation

Fertilizers

Compared to solid fertilizers, the advantages of complex liquid fertilizers are ease of production, lower capital and operating costs. The ratio of nutrients in LCFs can be adjusted over a wide range. In contrast to liquid nitrogen fertilizers, LCFs do not contain free ammonia.

The tests showed the equivalence of solid and liquid complex fertilizers. A slightly higher efficiency of LCF was noted on carbonate and soils saturated with bases.

LPFs are one of the promising types of fertilizers. Fertilizer production scheme is to neutralize phosphoric acid with ammonia to pH 6.5. There are two types of LCFs with different types of acid: orthophosphoric and superphosphoric.

Ammonium nitrate, urea or a mixture of both are used as a nitrogen source for LCFs. Urea allows you to get a more concentrated fertilizer, especially in the presence of potassium in the solution, as formed by adding ammonium nitrate in a solution of potassium nitrate – the least soluble salt in liquid fertilizers.

Liquid fertilizers based on thermal orthophosphoric acid are almost transparent liquids, based on extraction orthophosphoric acid – cloudy solutions (due to the formation of aluminum and iron phosphates, silicic acid). Concentration of nitrogen-phosphoric LCF on the basis of superphosphoric acid is higher than on the basis of orthophosphoric acid.

Using thermal orthophosphoric acid produces LCFs with a nutrient ratio of 9:9:9, a total of 27% N, P2O5 and K2O. Crystallization of the solution does not increase the nutrient content. The typical composition of the 9:9:9 grade is as follows: (NH4)2HPO4 12-15%, NH4P2O4 2-4%, (NH2)2CO 12-13%, KCl 13-14%. Amide nitrogen is 61-66% of the total. These fertilizers can also be obtained from extractable phosphoric acid. Because of the low nutrient content, it is economically viable to use them locally. A good economic effect of LCF gives their application with irrigation water, including in orchards, berry fields, vineyards.

Table. Ratio of the main nutritional elements in liquid fertilizers produced on the basis of orthophosphoric and superphosphoric acid[1]Agrochemistry. Textbook / V.G. Mineev, V.G. Sychev, G.P. Gamzikov et al; ed. by V.G. Mineev. - M.: Publishing house of the All-Russian Scientific Research Institute named after D.N. Pryanishnikov, … Continue reading

N:P2O5K2O
Orthophosphoric acid
Superphosphoric acid
4:1:0
16-4-0
24-6-0
3:1:0
18-6-0
24-8-0
2:1:0
16-8-0
22-11-0
1:1:0
13-13-0
19-19-0
1:2:0
9-18-0
15-30-0
1:3:0
8-24-0
12-36-0

When polyphosphoric acid is used due to the high solubility of ammonium polyphosphates, basic solutions and balanced fertilizers with higher concentrations are obtained. Micronutrients that are chelated by polyphosphoric acid can be introduced into LCF on polyphosphoric acid, preserving their availability to plants, while the orthophosphates of trace elements, except for boron, form insoluble compounds. Micronutrients are introduced in the form of oxides, as this ensures high solubility and stability of solutions. Trace elements are introduced into basic solutions (8:24:0; 10:34:0; 11:37:0) at a temperature of 50-90°. Basic solutions obtained from polyphosphoric acid can be applied directly as a fertilizer or used for further mixing with nitrogen and potassium components.

Potassium chloride is a source of potassium for LCFs. Because of its insufficient solubility, it reduces the concentration of the liquid fertilizer. Potassium nitrate is less soluble and is formed when ammonium nitrate or urea-ammonium nitrate mixture is used as an additional nitrogen component. Urea slightly increases the overall solubility of the system.

In the USA, potassium fertilizer is applied separately in the fall or is added to the LCF at the expense of suspensions. Therefore, LCF of composition 10:34:0 is better to use on soils with sufficient available potassium. In this case, potassium fertilizers in the rotation is made once every 2 years under potassium-dependent crops.

The introduction of stabilizing additives in the solution, such as colloidal clay or silicic acid, protects the supersaturated solution from crystallization. Preparation of 1 ton of fertilizer requires 9-22 kg of dry clay. Recommended for use 28% suspension of clay in pure form, which is introduced first with a solution of 10:34:0, then a mixture of urea ammonium nitrate, in the last turn – potassium chloride. Red flotation potassium chloride with a particle size of 0.8-1 mm is suitable for suspensions. The sum of nutrients in suspended LCFs reaches 40-45%. Attapulgite or bentonite clays (1.0-1.5%) are used as stabilizing additives of suspended LCF.

Liquid propellant compounds are produced by methods of hot and cold mixing. When hot mixing at a temperature of 210-250 ° C neutralize phosphoric or polyphosphoric acid with ammonia, carried out at large plants, while receiving the basic (basic) solutions of ortho-and polyphosphate ammonium. The method of cold mixing at a temperature of 35-45 ° C is used in small plants near the areas of application, while producing fertilizers with a given ratio of nutrients by introducing urea, ammonium nitrate, potassium salts into the basic solutions.

Liquid complex fertilizers do not contain free ammonia, so they can be sprinkled on the surface of the field with subsequent embedding, and transportation is not necessary in hermetically sealed containers.

Liquid complex fertilizers are non-flammable, non-explosive and non-poisonous.

LCFs are applied by special machines locally, in bands, under any crops. They are used on irrigated lands and with irrigation water.

For application of suspensions a special complex of machines is required which differs from mechanized means for application of conventional liquid complex fertilizers. The Russian industry produces LCF of grades 8:24:0 and 10:34:0, the production of more concentrated solution – 11:37:0 is mastered.

Table. Characteristics of some of the properties of the LCF[2]Agrochemistry. Textbook / V.G. Mineev, V.G. Sychev, G.P. Gamzikov et al; ed. by V.G. Mineev. - M.: Publishing house of the All-Russian Scientific Research Institute named after D.N. Pryanishnikov, … Continue reading

Fertilizer grade
Sum of nutrients, %
Specific weight, g/cm3
Amount of nutrients, kg/m3
9:9:9
27
1,24
335
10:34:0
44
1,35
594
11:37:0
48
1,40
672
12:12:12 (суспензия)
36
1,35
486

The use of liquid complex fertilizers allows to mechanize loading and unloading processes, eliminate losses during transportation, storage and application to the soil. This eliminates manual labor and reduces costs.

The advantages of liquid complex fertilizers are also: automated control of fertilizer distribution in the field, the possibility of joint application of herbicides, insecticides, trace elements.

The economic effect is associated with a reduction in capital costs due to the elimination of some stages of the production process, such as drying and granulation. Capital expenditures for the construction of LCF production shops are 20-30% less than for solid fertilizers. Even with the equal cost of LCF, labor costs for their use are 3-3.5 times less. Transportation and application of LCFs is 2-2.5 times cheaper than solid fertilizers.

The introduction of liquid complex fertilizers requires the creation of special machines. It should be taken into account that these fertilizers (especially suspended) are corrosive.

Liquid complex fertilizers interact with the soil more fully than granular fertilizers. The rate of interaction determines the nature of the resulting compounds, their solubility and availability to plants.

Peculiarities of application and efficiency of liquid complex fertilizers

Peculiarities of liquid complex fertilizers application:

  1. When using LCF on the basis of orthophosphoric acid on acidic, phosphorus-fixing soil, such as red soil, with low phosphorus content, as well as on poor acidic sod-podzolic soils the effect of LCF is weaker than granular forms. This is noted when applying full LCF with a ratio of 1:1:1 and an additional nitrogen component (ammonium nitrate). When applying unbalanced solution with a ratio of N:P2O5 1:4,5 or 1:3, the reduction of phosphate component action on acidic sod-podzolic soil is not noted.
  2. On calcareous sod-podzolic soils and chernozems LCF and granular fertilizers are of equal value.
  3. On carbonate soils with an alkaline reaction, such as carbonate chernozems, chestnut soils, gray soils, the agrochemical value of liquid forms, more often than granular.
  4. On acidic sod-podzol soils, a short-term decrease in mobile phosphorus content is observed when the solution is applied, which is associated with phosphate fixation by halved oxides. This is not observed on chernozems.
  5. On gray soils after the application of LCF the amount of mobile phosphorus increases compared with the application of granular fertilizer.
    The effectiveness of LCF is determined by its constituent phosphorus and nitrogen components. For example, LPF with ammonium nitrate on acidic sod-podzolic soil and red soil is less effective than solid granular fertilizer, on urea – equally effective. On typical chernozem with weakly acidic reaction and gray soils, the form of the nitrogen component does not affect the effect of the fertilizer: the effectiveness of solutions and granular fertilizer is equal. Solutions are a better source of phosphorus for plants than granular forms. The presence of urea in the fertilizer positively affects the accumulation of mobile phosphorus in acidic soils and has no significance in chernozem and gray soils, which is due to the temporary alkalization of the environment during the transformation of urea.

The effect of liquid complex fertilizers on the quality of products (grain, potatoes, hay) is also equivalent to solid fertilizers.

The action of suspended fertilizers coincides with the action of LCF and depends on the properties of the nitrogen and phosphorus components. The suspended agent does not affect the efficiency of liquid fertilizers.

In liquid complex fertilizers based on polyphosphoric acid, half of the phosphorus is in the form of polyphosphate. The effectiveness of such fertilizers is determined by the presence of orthophosphate, the rate of hydrolysis of polyphosphate into orthophosphate and the properties of the compounds that are formed when applied to soil. Regularities of the action of polyphosphate LCF – 10:34:0 and 11:37:0 solutions with 45-65% phosphorus content:

  1. On sod-podzolic soils liquid ammonium polyphosphates create the same phosphate regime as orthophosphates, have the same effect on the yield, both in direct action and after action. Soil liming has no effect on this pattern. On strongly acidic, phosphorus-poor red soils the effect of liquid polyphosphates is slightly worse than that of granulated orthophosphates.
  2. On typical and leached chernozems the effect of liquid polyphosphates on grain crops is equal to that of liquid and granular orthophosphates.
  3. On carbonate chernozems polyphosphate LCF show a better effect on crop yields compared with granular fertilizers. This is explained by the fact that the application of polyphosphate in the soil for a longer time is stored more available orthophosphate, formed a reserve of soluble phosphate than the background orthophosphate fertilizers. On carbonate soils polyphosphates contribute to the supply of zinc to plants.
  4. On sulfur soils liquid ammonium polyphosphates are assimilated better than orthophosphates. The effect on the yield is equal to orthophosphates or exceeds them. Subsequently, polyphosphates are a better source of phosphorus than orthophosphates.
  5. Polyphosphates enriched with trace elements are effective.

Sources

Yagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry/Under ed. B.A. Yagodin. – M.: Kolos, 2002. – 584 p.: ill.

Agrochemistry. Textbook / V.G. Mineev, V.G. Sychev, G.P. Gamzikov et al. – M.: Publishing house of the All-Russian Scientific Research Institute named after D.N. Pryanishnikov, 2017. – 854 с.