Micronutrient fertilizers
Micronutrient fertilizers — chemical substances and their mixtures used in agriculture as a source of trace elements for plant nutrition.
Trace elements — chemical elements found in plants in thousandths to hundred-thousandths of a percent and performing functions in vital processes.
The theoretical foundations for the use of micronutrient fertilizers in agriculture became possible after establishing the physiological role of trace elements in plant life. Significant contributions to solving theoretical and practical problems related to plant nutrition with trace elements were made by Ya. V. Peive, M. V. Katalymov, P. A. Vlasyuk, R. K. Kedrov-Zikhman, M. Ya. Shkolnik.
Importance of trace elements in plant life
The positive effect of trace elements is due to their participation in redox processes, carbohydrate and nitrogen metabolism. They increase plant resistance to diseases and unfavorable environmental conditions. Under the action of trace elements, chlorophyll content in leaves increases, photosynthetic processes improve, and the assimilatory activity of the whole plant intensifies. Many trace elements are part of the active centers of enzymes and vitamins.
Trace elements can form complexes with nucleic acids, influence the physical properties, structure, and physiological functions of ribosomes. They affect the permeability of cell membranes and the entry of nutrients into plants. Thus, when maize nutrition with trace elements is disturbed, the uptake of ammonium and nitrate nitrogen decreases. The greatest decrease in ammonium nitrogen absorption is noted with deficiency of zinc, molybdenum, and excess of cobalt, manganese. The rate of nitrate nitrogen uptake decreases with a shortage of copper and manganese. With excess zinc in the nutrient medium, ammonium nitrogen uptake decreases; with copper deficiency, it increases. Disturbance of molybdenum and zinc nutrition leads to an increase in the difference between ammonium and nitrate nitrogen uptake.
Overall, when trace element nutrition is disturbed, nitrate nitrogen uptake decreases first. When cobalt and zinc nutrition is disturbed, the rate of incorporation of ammonium nitrogen into proteins decreases.
In a number of soil-climatic zones, crops are responsive to various micronutrient fertilizers. This is most often observed with long-term application of high doses of mineral fertilizers, especially on drained peaty soils, irrigated lands, and soils light in granulometric composition.
Table. Requirement of agricultural crops for trace elements (according to scientific institutions, 1988).
| Crops | B | Cu | Mn | Mo | Zn |
|---|---|---|---|---|---|
| Cereals: | |||||
| winter wheat | — | ++ | ++ | — | — |
| winter rye | — | — | + | — | — |
| spring wheat | — | ++ | ++ | — | — |
| spring rye | — | + | + | — | — |
| barley | — | ++ | + | — | — |
| oats | — | ++ | ++ | + | — |
| Grain legumes: | |||||
| peas | — | — | ++ | + | — |
| beans | + | + | — | + | + |
| lupine | ++ | — | — | + | — |
| Oilseeds: | |||||
| winter rapeseed | ++ | — | ++ | + | — |
| spring rapeseed | ++ | — | ++ | + | — |
| mustard | + | — | — | + | — |
| flax | + | ++ | — | — | ++ |
| Vegetables: | |||||
| cauliflower | ++ | + | + | ++ | — |
| cucumber | — | + | ++ | — | — |
| carrot | + | ++ | + | — | — |
| radish | + | + | ++ | + | — |
| black radish | + | + | ++ | + | — |
| tomato | + | + | + | + | + |
| white cabbage | ++ | + | + | + | — |
| onion | — | ++ | ++ | — | + |
| Row crops: | |||||
| potato | + | — | + | — | + |
| sugar beet | ++ | + | ++ | + | + |
| Forage: | |||||
| red clover | + | + | + | ++ | + |
| alfalfa | ++ | ++ | + | ++ | + |
| lupine | ++ | — | — | + | — |
| maize for silage and green mass | + | + | + | — | ++ |
Note. — low requirement for the element; + — medium requirement; ++ — high requirement.
In leguminous crops, molybdenum content is higher; they accumulate 2–10 times more iron than cereals. Plants also accumulate trace elements differently, which becomes important when using crop products.
When trace element contents are above or below threshold concentrations, the organism loses the ability to regulate metabolic processes, which manifests as endemic diseases. In modern conditions of intensification and chemicalization of agriculture, knowledge of threshold concentrations of trace elements in plants and feeds is especially relevant.
Table. Threshold concentrations of chemical elements in feeds for agricultural animals.
| Chemical element | Content of elements in pasture plants, mg/kg dry matter, feed | |||
|---|---|---|---|---|
| average | insufficient (lower threshold concentration) | optimal* | excessive (upper threshold concentration) | |
| I | 0.18 | up to 0.07 | 0.07–1.2 | > 0.8–2.0 and above |
| Co | 0.32 | up to 0.1–0.25 | 0.25–1 | > 1 |
| Mo | 1.25 | up to 0.2 | 0.2–2.5 | > 2.5–3 and above |
| Cu | 6.40 | up to 3–5 | 3–12 | > 20–40 and above |
| Zn | 21.00 | up to 20–30 | 20–60 | > 60–100 and above |
| Mn | 73.00 | up to 20 | 20–60 | > 60–70 and above |
Notes.
* Limits under normal regulation of functions in animals of different species in different biological states.
Application of micronutrient fertilizers provides a significant increase in crop yield. On average, due to micronutrient fertilizers, it is possible to increase crop productivity by 10–12%. The greatest effect is achieved in regions whose soils are depleted in certain trace elements. There are quite many such soils. According to large-scale agrochemical soil survey data, low and medium supply of mobile boron is characteristic of 37.3%, molybdenum — 85.5%, copper — 64.9%, zinc — 94.0%, cobalt — 86.9%, manganese — 52.5% of the total arable area.
Table. Influence of trace elements on crop yield in the main areas of their application.
| Trace element | Crop | Soils | Increase in yield from trace element, t/ha |
|---|---|---|---|
| Boron | Sugar beet: roots | leached and podzolized chernozems | 2.0–4.0 |
| seeds | 0.2–0.3 | ||
| Flax: straw | sod-gley and peat soils | 0.06–0.15 | |
| seeds | 0.04–0.10 | ||
| Molybdenum | Clover: hay | sod-podzolic and gray forest soils | 0.6–1.3 |
| seeds | 0.05–0.08 | ||
| Cabbage, seeds | sod-podzolic loamy soils | 0.23–0.26 | |
| Vetch-oat mixture, hay | 0.60–0.85 | ||
| Copper | Barley, grain | peat-bog soils | 0.6–1.5 |
| Wheat, grain | 0.5–1.3 | ||
| Manganese | Sugar beet, roots | leached and podzolized chernozems | 1.0–2.0 |
| Winter wheat, grain | 0.15–0.35 | ||
| Sunflower, seeds | 0.23–0.27 | ||
| Zinc | Maize, grain | carbonate chernozems, humus-carbonate soils | 0.5–0.7 |
| Wheat, grain | 0.15–0.20 |
At present, the supply of trace elements to agricultural production has decreased, while the demand of Russian agriculture for the near future is estimated at 12 thousand t.
Table. Demand of Russian agriculture for micronutrient fertilizers (t of nutrients) (VNIPTIKHIM, 1999).
| Economic region, oblast | B | Mo | Cu | Zn | Co | Mn |
|---|---|---|---|---|---|---|
| Russian Federation | 4800.0 | 1012.6 | 3063.0 | 961.4 | 165.8 | 1976.7 |
| Central: | 350.0 | 108.2 | 638.0 | 392.0 | 54.5 | 170.8 |
| Bryansk | 59.9 | 12.2 | 46.7 | — | 0.7 | — |
| Vladimir | 14.1 | 8.1 | 49.7 | — | 0.6 | — |
| Ivanovo | 12.0 | 6.1 | 13.1 | — | 0.6 | — |
| Kaluga | 25.5 | 7.8 | 14.9 | — | 0.6 | — |
| Moscow | 58.9 | 38.0 | 412.8 | 392.0 | 50.0 | 170.8 |
| Ryazan | 59.3 | 120.5 | 46.6 | — | 0.8 | — |
| Smolensk | 77.1 | 16.8 | 46.7 | — | 0.6 | — |
| Tula | 43.2 | 8.7 | 7.5 | — | 0.6 | — |
Removal of trace elements with the harvest from 1 ha of soil ranges from fractions of a gram (molybdenum) to several hundred grams (manganese, zinc).
Trace element content in soil
Soils have a certain reserve of trace elements, which can be replenished by applying organic fertilizers, micronutrient fertilizers, and also as an admixture with mineral fertilizers. The mobility of trace elements in manure is inferior to mineral fertilizers and is no more than 25%.
Criteria for plant need for trace elements are their content in plants and their level in soil. What matters is not the total (bulk) amount in soil, but the presence of mobile forms, which to a certain extent determine availability to plants. Most often, the content of trace elements in mobile form is for copper, molybdenum, cobalt, and zinc — 10–15% of the bulk content in soil, for boron — 2–4%.
The degree of mobility of trace elements in soil depends on: reaction of the medium, composition of parent rock, vegetation, microbiological activity, carbonate content, redox properties, granulometric and mineralogical composition, humus content, sesquioxides, application of a complex of agrotechnical measures, especially water and chemical soil reclamation, and application of organic and mineral fertilizers.
The influence of soil conditions is specific and may differ for different trace elements. For example, acidification increases the mobility of manganese, copper, boron, zinc, but decreases the availability of molybdenum.
The concept of "mobility" in modern science does not have a precise definition. In most cases, mobility is understood as all forms of trace elements capable of passing into water, salt extracts, solutions of strong and weak acids, and alkalis. Often no distinction is made between mobile and plant-available forms.
Mobile forms of trace elements in soil are divided into:
- slightly mobile — pass into solutions of strong acids;
- moderately mobile — pass into solutions of weak acids and alkalis, acid-buffer solutions;
- readily soluble — pass into water and carbonic acid extracts.
It is important that the selected extract for determining the mobile form corresponds as much as possible to the assimilating ability of a particular plant. The suitability of extracts for determining soil supply with trace elements is assessed by field experiments with micronutrient fertilizers, in which correspondence is established between the content of mobile forms of trace elements and the effectiveness of micronutrient fertilizers.
In our country, a differentiated approach is used to select methods for determining mobile forms of trace elements in soil depending on soil type, properties, and agrochemical characteristics.
- For sod-podzolic soils, a system of extracts proposed by Ya. V. Peive and G. Ya. Rinkis is used. A scale of soil supply with trace elements has been developed.
- When analyzing forest, chernozem, chestnut, carbonate, and saline soils, to determine mobile forms of manganese, zinc, copper, cobalt, an acetate-ammonium buffer solution with pH 4.8 (according to Krupsky-Aleksandrova) is used; boron is determined in a water extract after boiling, molybdenum — in an oxalate extract (according to Grigg).
- When analyzing carbonate and saline, brown, bog-meadow soils and serozems, for extraction of zinc, copper, and cobalt, 1 N acetate-sodium buffer solution with pH 3.5 (according to Kruglova) is used; molybdenum is extracted with oxalate buffer solution with pH 3.3 (according to Grigg); boron — in a water extract.
Extensive agrochemical soil studies have shown that soils of individual biogeochemical provinces are often poor in mobile forms of certain trace elements. For example, in Moscow oblast, up to 80% of surveyed lands need application of boron fertilizers; molybdenum deficiency was found on 60% of areas, copper — on 50–60%.
B. A. Yagodin and I. V. Vernichenko summarized data on soil supply of the main biogeochemical zones with mobile forms of trace elements, obtained from analysis of soils and plants, field and greenhouse experiments.
Table. Gradations of supply of Russian soils with mobile forms of trace elements.
| Trace element | Biogeochemical zone | Soil extract | Supply, mg/kg soil | ||||
|---|---|---|---|---|---|---|---|
| very low | low | medium | high | very high | |||
| B | Taiga-forest | H2O | 0.2 | 0.2–0.4 | 0.4–0.7 | 0.7–1.1 | 1.1 |
| Cu | 1.0 N HCl | 0.9 | 0.9–2.1 | 2.1–4.0 | 4.0–6.6 | 6.6 | |
| Mo | Oxalate extract | 0.08 | 0.08–0.14 | 0.14–0.30 | 0.30–0.46 | 0.46 | |
| Mn | 0.1 N H2SO4 | 1.0 | 1.0–25.0 | 25–60 | 60–100 | 100 | |
| Co | 1.0 N HNO3 | 0.4 | 0.4–1.0 | 1.0–2.3 | 2.3–5.0 | 5.0 | |
| Zn | 1.0 N KCl | 0.2 | 0.2–0.8 | 0.8–2.0 | 2.0–4.0 | 4.0 | |
| B | Forest-steppe and steppe | H2O | 0.2 | 0.2–0.4 | 0.4–0.8 | 0.8–1.2 | 1.2 |
| Cu | 1.0 N HCl | 1.4 | 1.4–3.0 | 3.0–4.4 | 4.4–5.6 | 5.6 | |
| Mo | Oxalate extract | 0.10 | 0.10–0.23 | 0.23–0.38 | 0.38–0.55 | 0.55 | |
| Mn | 0.1 N H2SO4 | 25 | 25–55 | 55–90 | 90–170 | 170 | |
| Co | 1.0 N HNO3 | 1.0 | 1.0–1.8 | 1.8–2.9 | 2.9–3.6 | 3.6 | |
| Zn | Acetate-ammonium | 4.0 | 4.0–6.0 | 6.0–8.8 | 8.8 | — | |
| B | Dry-steppe and semi-steppe | 1.0 N KNO3 | 0.4 | 0.4–1.2 | 1.2–1.7 | 1.7–4.5 | 4.5 |
| Cu | HNO3 (according to Gyulakhmedov) | 1.0 | 1.0–1.8 | 1.8–3.0 | 3.0–6.0 | 6.0 | |
| Mo | Same | 0.05 | 0.05–0.15 | 0.15–0.50 | 0.5–1.2 | 1.2 | |
| Mn | Same | 6.6 | 6.6–12.0 | 12–30 | 30–90 | 90 | |
| Co | Same | 0.6 | 0.6–1.3 | 1.3–2.4 | 2.4 | — | |
| Zn | Same | 0.3 | 0.3–1.3 | 1.3–4.0 | 4.0–16.4 | 16.4 | |
The range of extracts used is wide — from strong acids to aqueous solutions. A significant part of them is aggressive and hardly extracts only plant-available trace elements. When comparing values of trace element consumption by plants with their content in soil extracted by aggressive extracts, it was established that plants assimilate less than 1% of the extracted trace elements.
When assessing soil supply with available forms of trace elements and developing practical recommendations, changes in the content of mobile forms depending on sampling time should be taken into account. These fluctuations can be so significant that in different periods of vegetation the soil may be well or poorly supplied with trace elements.
Application of mineral fertilizers changes the mobility of trace elements due to changes in medium reaction, synergism, and antagonism. Thus, phosphorus reduces the uptake of zinc and copper, sometimes increases the uptake of manganese. Application of magnesium increases phosphorus uptake by plants. Organic substances change the adsorption of all mineral elements. Therefore, along with soil analysis for mobile trace element content, plant analysis can more accurately assess plant supply.
Depending on the amount of trace elements in soils of the Non-Chernozem zone, the following levels of supply with trace elements have been established (table).
Table. Grouping of soils of the Non-Chernozem zone by plant supply with trace elements.
| Supply | Content of trace elements, mg/kg soil | |||||
|---|---|---|---|---|---|---|
| Mn (0.1 N H2SO4) | B (water) | Mo (in oxalate extract, according to Grigg) | Cu (1 N HCl) | Co (1 N HNO3) | Zn (1 N HCl) | |
| First group of plants | ||||||
| Low | < 15 | < 0.1 | < 0.05 | < 0.5 | < 0.3 | < 0.3 |
| Medium | 15–30 | 0.1–0.3 | 0.05–0.15 | 0.5–1.5 | 0.3–1 | 0.3–1.5 |
| High | > 30 | > 0.3 | > 0.15 | > 1.5 | > 1 | > 1.5 |
| Second group of plants | ||||||
| Low | < 45 | < 0.3 | < 0.2 | < 0.2 | < 1 | < 1.5 |
| Medium | 45–70 | 0.3–1.0 | 0.2–0.3 | 2–4 | 1–3 | 1.5–3 |
| High | > 70 | > 0.5 | > 0.3 | > 4 | > 3 | > 3 |
| Third group of plants | ||||||
| Low | < 100 | < 0.5 | < 0.3 | < 5 | < 3 | < 3 |
| Medium | 100–150 | 0.5–1.0 | 0.3–0.5 | 5–7 | 3–5 | 3–5 |
| High | > 150 | > 1 | > 0.5 | > 7 | > 5 | > 5 |
Note. First group — crops with low removal of trace elements and relatively high assimilating ability: cereals, maize, grain legumes, potato.
Second group — crops with increased removal of trace elements, with high and medium assimilating ability: root crops, vegetables, grasses (legumes, cereals, mixed grasses), orchards.
Third group — crops with high removal of trace elements — all above crops under good agrotechnical background: irrigation, high fertilizer doses, use of best varieties, good soil cultivation and plant care.
Grouping of soils by plant supply with manganese, copper, zinc, cobalt extracted from soils with acetate-ammonium buffer solution with pH 4.8 (according to Krupsky-Aleksandrova) is given in the table.
Table. Grouping of soils by plant supply with trace elements (extractant: acetate-ammonium buffer with pH 4.8 according to Krupsky-Aleksandrova).
| Supply | Content of trace elements, mg/kg soil | |||
|---|---|---|---|---|
| Mn | Cu | Zn | Co | |
| Low removal of trace elements | ||||
| Low | < 5 | < 0.1 | < 1 | < 0.07 |
| Medium | 5–10 | 0.1–0.2 | 1–2 | 0.07–0.15 |
| High | > 10 | > 0.2 | > 2 | > 0.15 |
| Increased removal of trace elements | ||||
| Low | < 10 | < 0.2 | < 2 | < 0.15 |
| Medium | 10–20 | 0.2–0.5 | 2–5 | 0.15–0.30 |
| High | > 20 | > 0.5 | > 5 | > 0.30 |
| High removal of trace elements | ||||
| Low | < 20 | < 0.5 | < 5 | < 0.3 |
| Medium | 20–40 | 0.5–1 | 5–10 | 0.3–0.7 |
| High | > 40 | > 1 | > 10 | > 0.7 |
The content of mobile manganese in soils extracted with acetate-ammonium buffer solution with pH 4.8 is approximately 3–4 times less than in 0.1 N H2SO4 extract (according to Peive-Rinkis). The content of zinc, on the contrary, in acetate-ammonium extract is 2–4 times higher than in 1 N KCl. Copper and cobalt are extracted by buffer solution on average 6–8 times less (with fluctuations from 3 to 15 times) than by 1 N HCl and 1 N HNO3 solutions.
Don State Agrarian University developed a scale for supply of carbonate chernozems and chestnut soils with zinc (table).
Table. Scale of zinc supply of carbonate chernozems and chestnut soils (E. V. Agafonov, 2012).
| Supply | Content of mobile phosphorus in soil, mg/kg soil (according to Machigin) | |||
|---|---|---|---|---|
| < 15 | 16–30 | 31–45 | 45–60 | |
| Content of mobile zinc in soil, mg/kg soil (in AAB, pH 4.8) | ||||
| Low | < 0.15 | 0.16–0.25 | 0.26–0.35 | 0.36–0.45 |
| Medium | 0.16–0.25 | 0.26–0.35 | 0.36–0.45 | 0.46–0.60 |
| High | 0.26–0.35 | 0.36–0.45 | 0.46–0.60 | 0.61–0.75 |
Classification of micronutrient fertilizers
Micronutrient fertilizers are usually classified by the main trace element:
- boron fertilizers;
- copper fertilizers;
- manganese fertilizers;
- molybdenum fertilizers;
- zinc fertilizers;
- cobalt fertilizers;
- selenium-containing fertilizers;
- lithium fertilizers.
Application of micronutrient fertilizers in agriculture
Results of studies on promising types and forms of micronutrient fertilizers show the expediency of producing and using fertilizers enriched with trace elements, including complex ones. Tests of experimental and pilot-industrial batches of main fertilizers enriched with trace elements showed that, for example, due to boron in nitroammophoska applied on leached chernozem and sod-podzolic soils, additional yield increases are obtained: sugar beet roots 3–4 t/ha, cabbage seeds 0.23–0.29 t/ha, pea seeds 0.21–0.37 t/ha.
Application on sod-podzolic soils of superphosphate enriched with molybdenum provides an additional harvest of 0.5–0.6 t/ha of legume hay. Under conditions of severe copper deficiency, for example, on drained lowland peat-bog soils, against the background of basic fertilizers, cereals almost do not produce grain, whereas potassium chloride enriched with copper allows obtaining barley grain yield of 2.5–3.0 t/ha, increasing grass yield by 15–18%, and vegetable yield by 20%.
According to forecasts, the demand of agriculture for micronutrient fertilizers should be met 60–70% in the form of main fertilizers enriched with trace elements and 30–40% through technical salts used for foliar feeding and presowing seed treatment.
Some industrial wastes can be used as a source of trace elements, for example, metallurgical slags, pyrite cinders, sewage sludge, etc. Fertilizers of this type do not always contain nutrients in a form available to plants and often contain toxic impurities.
Micronutrient fertilizers "MiBAS" developed on a lignin basis, manufactured from wastes of pulp and paper, printing, electronics, machine-building, and other industries, may prove promising. The developed technologies for recycling these wastes allow extracting trace elements in pure form and obtaining ecologically safe fertilizers from them. At the same time, lignin-containing wastes of pulp and paper production and metal-containing wastes are utilized.
A distinctive feature of the new fertilizers is the lignin base, which creates a polymer film on the surface, for example, of seeds, and reliably adheres to this surface. The composition of "MiBAS" micronutrient fertilizers includes copper-, zinc-, and cobalt-containing components. "MiBAS" fertilizers are technologically convenient to use, do not dust, and are compatible with plant protection products. Field and production experiments have established the effectiveness of these micronutrient fertilizers.
Lignin-based micronutrient fertilizers are produced in granular form with prolonged action for basic application and as a liquid concentrate for presowing seed treatment. The content of trace elements in granular forms is 10±5%, in the concentrate, which is diluted 3 times before treatment, 1.3±0.3%. The consumption of granular fertilizers is 50–150 kg/ha, of liquid concentrate in diluted form — 10–20 kg/t of seeds.
Timing and methods of micronutrient fertilizer application
It is better to apply micronutrient fertilizers to the soil as part of basic mineral fertilizers. It is promising to introduce trace elements into the composition of slow-acting fertilizers, as well as to apply them with irrigation water.
Based on information about the content of trace elements in soil and plants, the doses of trace elements required for application are determined. Doses of micronutrient fertilizers vary depending on soil-climatic conditions and biological characteristics of crops.
For the conditions of the North Caucasus region, recommendations have been developed on the rates of micronutrient fertilizer application for field crops depending on application methods and trace element content in soil (Podkolzin, Demkin, Burlai, 2002).
Under protected ground conditions, trace elements (boron, molybdenum, copper, manganese, zinc, cobalt) are important. Application methods: pre-sowing application to the soil, presowing seed treatment, and foliar feeding. Per 100 kg of seeds, 2–3 L of solution is used. Watering seedlings at the rate of 10 L per frame. Seed soaking — up to 24 h at a seed-to-solution weight ratio of 1:2. Foliar feeding is carried out at the rate of 300 L per 1 ha.
Table. Doses of micronutrient fertilizers for vegetable crops in protected ground.
| Fertilizers | Applied to soil, kg/ha | Seed soaking | Foliar feeding | Watering seedlings | |
|---|---|---|---|---|---|
| total amount | calculated per element | solution concentration, % | |||
| Boron-magnesium | 43 | 1 | — | — | — |
| Boric acid | 6 | 1 (once every 3–5 years) | 0.02–0.04 | 0.02–0.05 | 0.005–0.03 |
| Copper sulfate | 12 | 3 | 0.005–0.03 | 0.01–0.05 | 0.005–0.03 |
| Manganese sulfate | 10–12 | 3 | 0.02–0.2 | 0.05–0.2 | 0.01 |
| Ammonium molybdate | 0.4–0.6 | 0.2–0.3 | 0.01–0.08 | 0.03–0.05 | 0.02 |
| Zinc sulfate | 6–8 | 2 | 0.02–0.05 | 0.02 | 0.005 |
| Cobalt sulfate | 0.9–1.4 | 0.3–0.5 | — | 0.02 | — |
Doses of micronutrient fertilizers are significantly lower than those of macronutrients, and requirements for uniformity are higher. Therefore, it is more rational to use basic fertilizers enriched with trace elements.
Effectiveness of micronutrient fertilizers
For effective use, it is necessary:
- Knowledge of crop requirements for trace elements and their content in soil in a plant-available form. Nutrition optimization should be carried out in a balanced manner for macro- and trace elements.
- Improvement of the assortment of micronutrient fertilizers.
- Strengthening agrochemical and sanitary control over the use of industrial waste as fertilizer.
- Study of the influence on product quality formation under balanced plant nutrition with macro- and trace elements, and the role of trace elements in forming individual quality indicators.
- Study of transformation, reutilization, balanced optimization of metabolism of organic compounds in plants that characterize product quality, and the importance of trace elements in these processes.
- At present, the production of micronutrient fertilizers is developing in two directions: production of one-sided micronutrient fertilizers in the form of individual salts, chelates, and frits; production of complex and one-sided macronutrient fertilizers enriched with trace elements.
One-sided micronutrient fertilizers are used for crops with severe deficiency of a particular trace element. The disadvantage of using one-sided micronutrient fertilizers is the difficulty of applying them in small doses, especially to the soil, when it is difficult to achieve uniform distribution over the surface. One-sided micronutrient fertilizers are used in the form of chelates and frits, which is especially important when applying boron, since this excludes the effect of locally high boron concentrations on sensitive crops.
Enriched macronutrient fertilizers reduce application costs, have a lower risk of toxic effects when excessive fertilizer doses are applied, and reduce environmental pollution.
For foliar feeding, individual salts are mainly used, for example, sulfates of manganese, zinc, and iron.
The use of trace elements in combination with macronutrients in the composition of complex fertilizers or nutrient mixtures should be limited, and used under conditions of absolute nutrient deficiency when cultivating plants on low-fertility sandy and sandy loam soils, under hydroponics or protected ground conditions, in horticulture and ornamental floriculture.
Tasks of agrochemistry of micronutrient fertilizers
In the field of agrochemistry of trace elements, of primary importance for practical application in agriculture and for ensuring high agrochemical and economic efficiency are tasks on:
- development of methods for predicting the effectiveness of micronutrient fertilizers based on agrochemical soil analysis for the content of available forms of trace elements and plant diagnostics;
- study of the effect of forms of micronutrient fertilizers on the yield and quality of agricultural crops in a network of geographical field experiments conducted according to unified methodology and program, against the background of increasing doses of basic mineral fertilizers;
- study of the balance of macro- and trace elements in long-term field experiments with fertilizers in crop rotation in various soil-climatic zones, including in fertilization systems;
- study of the interaction of macro- and trace elements in nutrition and metabolism processes, and the influence of micronutrient fertilizers on the use and assimilation of basic nutrients from soil and fertilizers.
Research on developing methods for predicting effectiveness includes:
- determination of limiting values of trace element content in soils and plants;
- development of improved methods for determining available forms in soils;
- establishment of scientifically substantiated gradations of soil supply with trace elements for specific soil-climatic zones.
These methods should take into account crop characteristics, soil type and granulometric composition, application of organic and mineral fertilizers, and methods of regulating water regime.
Of great importance is the development of methods for rational use of industrial production wastes containing trace elements, and the search for raw materials suitable for the production of micronutrient fertilizers.
The study of the balance of macro- and trace elements in long-term field experiments with crop rotations should be accompanied by research on the influence of applying high doses of organic and mineral fertilizers, methods of chemical reclamation, and chemical plant protection products on the content and availability to plants of trace elements in soil and fertilizers.
Promising is the study of the agrochemical importance of trace elements: iodine, lithium, aluminum, vanadium, titanium, selenium, rubidium, bromine, and fluorine, as well as determination of the negative impact of copper, fluorine, arsenic, chromium, lead, cadmium, and nickel as a result of technogenic environmental pollution.
It is necessary to study hidden deficiency of trace elements without external manifestation of signs, which leads to a decrease in yield and product quality.
At the present stage of development, it has become possible to take into account many factors determining the rates of application of macro- and micronutrient fertilizers using computer technology.
References
- Yagodin B. A., Zhukov Yu. P., Kobzarenko V. I. (2002). Agrochemistry. Ed. by B. A. Yagodin. Moscow: Kolos.
- Mineev V. G., Sychev V. G., Gamzikov G. P. et al. (2017). Agrochemistry. Textbook. Ed. by Mineev V. G. Moscow: Publishing House of VNIIA named after D. N. Pryanishnikov.
