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Copper fertilizer

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Copper in plant life

On average, plants contain 0.0002% copper, or 2 mg per 1 kg of weight, varies depending on the species and soil conditions. With the harvest of different crops carried 7-27 g of copper per 1 hectare.

In the plant cell about 2/3 of copper is insoluble, bound state. The largest amount of copper is concentrated in seeds and the most viable growing parts of plants. 70% of copper in the leaf is concentrated in chloroplasts. Physiological role of copper is determined by its incorporation into copper-containing proteins and enzymes catalyzing oxidation of diphenols and hydroxylation of monophenols: orthodiphenol oxidase, polyphenol oxidase and tyrosinase.

Table. Copper content in plants grown on sod-podzolic soil and powerful black earth (according to Katalymov)

Plant
Sod-podzolic soils
Powerful black earth
yield, t/ha
Cu content, mg/kg
yield, t/ha
Cu content, mg/kg
Spring wheat:
- grain
2,3
7,7
1,0
5,2
- straw
2,4
3,0
1,4
1,5
Oats:
- grain
2,2
5,8
2,0
3,6
- straw
3,9
7,5
2,1
3,7
Spring vetch (hay)
4,0
12,2
2,5
4,7
Potatoes:
- tubers
27,0
6,0
-
-
- haulm
50,0
18,0
-
-
Sugar beet:
- roots
54,2
6,4
28,0
6,5
- leaves
45,0
8,4
10,0
6,9

The copper-containing enzyme cytochrome oxidase has been well studied. It is assumed that the active center of cytochrome oxidase includes copper and iron. Almost half of all copper contained in leaves is in the copper-containing protein, plastocyanin. Copper deficiency has a negative effect on the activity of copper-containing enzymes.

Copper performs certain functions in nitrogen metabolism as a part of nitrite reductase, hyponitrite reductase and nitric oxide reductases. Due to the effect of copper on the biosynthesis of leghemoglobin and the activity of enzyme systems, these enzymes enhance the process of binding molecular atmospheric nitrogen and the assimilation of soil and fertilizer nitrogen.

There is evidence of an increase in the strength of the chlorophyll-protein complex under the action of copper, a decrease in the destruction of chlorophyll in the dark and a positive effect on the greening process in all plants.

As a result of inactivation by the copper-containing enzyme polyphenol oxidase auxins, copper inhibits the effect on growth of high doses of these substances. The copper-containing enzyme tyrosinase regulates the oxidation of the amino acid tyrosine to the black pigment melanin. Lack of this enzyme leads to albinism, the lack of green coloration in plants. The darkening of broken potatoes, apples, etc. is also caused by tyrosinase.

Ethylene inhibits tissue differentiation and inhibits cell division, DNA synthesis, and plant growth. Ethylene synthesis is regulated by a copper-containing enzyme. Reduction of phenolic inhibitors in plants leads to elongation of stems and lodging of plants. Probably by regulating the content of phenolic growth inhibitors in plants, copper increases lodging resistance of plants. It increases the drought, frost and heat tolerance of plants.

Copper deficiency leads to growth retardation, chlorosis, loss of turgor and wilting of plants, delayed flowering and death of crops. Cereal crops in acute copper deficiency have no ear development (white plague or processing disease), fruit crops have dryness.

Copper content in soils

The gross content of copper in soils ranges from 0.1 to 150 mg/kg of soil. In the arable layer in the mobile form is mainly divalent copper cation in the exchange-absorbed state. Copper is a part of soil minerals and organic matter. The greatest quantity of copper is connected with montmorillonite and vermiculite, iron and manganese oxides, iron and aluminum hydroxides. Stable complexes of humic and fulvic acids may form with copper, so upper peatlands, sod-carbonate, bog, swamp, sandy and sandy loam soils are poor in copper. Liming of acidic soils reduces the availability of copper to plants because it promotes fixation in the soil. Lime acts as an adsorbent for copper, and by alkalizing creates conditions for the formation of stable complexes with organic compounds.

Plants are deficient in copper, and soils are considered poor, when the content in the soils of the Non-Black Earth zone – less than 1.5-2.0 mg, in the Black Earth zone – less than 2.0-5.0 mg per 1 kg of soil.

The need for copper fertilizers is mainly observed in the North-West, Central, Volga-Vyatka regions of Russia.

Copper fertilizers are effective on peaty, light sandy and sod-gley soils. On drained peatlands, even with the application of full mineral fertilizer, a full harvest of grains and other crops can be obtained only with the application of copper. According to experiments, the application of copper fertilizers on peat bog and light loamy soils increases the yield of cereals by 0.2-0.5 t/ha.

Mobility of copper in the soil increases with acidification of the reaction of the soil solution, reducing the content of organic matter and clay fraction. Fixation of copper is promoted by the high content of organic substances and carbonates, alkaline reaction and fine granulometric composition of soil, with a large proportion of silt.

Wheat, oats, barley, grasses, flax, hemp, root crops, meadow clover, millet, sunflowers, mustard, sugar and fodder beets, fodder beans, peas, vegetable and fruit crops respond well to copper fertilizers. The need for copper increases under conditions of high doses of nitrogen fertilizers. Peas, vetch, lupine, hemp, flax, beets, vegetables, and fruit crops suffer from copper deficiency in soil.

Copper fertilizer application

Agricultural demand for copper fertilizers is mainly met by copper sulfate, copper-potassium fertilizers and copper-containing industrial waste.

Table. Assortment of copper fertilizers

Fertilizer
Active substance
Content of active substance in water-soluble form, %
Copper sulfate
CuSO4⋅5H2O, Cu
92,0-98,0
Cu
23,4-24,9
Powder containing copper
CuSO4
14-16
Cu
5-6
Pyritic burns
Cu
0,25
K2O
58,6±0,6

Sulfuric copper or copper sulfate pentahydrate, copper sulfate (CuSO4⋅5H2O) is a blue-blue crystalline salt containing 25.4% of copper, well soluble in water.

Pyrite cinders are copper fertilizers of local importance, containing 0.2-0.7% of copper, an industrial waste product for production of sulfuric acid. They contain impurities of iron, manganese, cobalt, zinc and molybdenum. The disadvantage of pyrite slag is the presence of arsenic, lead and other heavy metals, so their use requires systematic control of the potential pollution of soil, plants and agricultural products. It is applied once in 4-5 years at a dose of 500-600 kg/ha in the fall under the autumn plowing or spring under the pre-sowing cultivation.

Slags from zinc-electrolyte and copper-smelting plants containing 0.2-0.5% copper are used as copper fertilizer. Also – low percent oxidized copper ores containing about 0.9%.

Seed pre-sowing treatment is carried out by spraying with 0.1-0.2% copper sulfate solution or by powdering. Consumption of the solution by spraying is 6-8 liters per 100 kg of seeds. To sprinkle 100 kg of seeds you should use 50-200 g of well dried and ground copper sulfate. Sprinkling is combined with seed dressing. Sprinkling with copper sulfate is convenient for flax, the seeds of which soak when soaked. Covering foliar dressing rate is 200-300 g per 1 ha of seeds or 0.02-0.05% solution. When ground spraying of row crops – 300-400 l/ha, when aerial application – 100 l/ha.

Pyrite slag, copper-containing slag, and low-percentage oxidized copper ore are used to apply to the soil. Pyrite slag and slags are applied in an amount of 500-600 kg/ha once every 4-5 years, and low percent oxidized copper ore – 200-300 kg/ha. Fertilizer is applied with a plow when plowing the fallow land, or with a cultivator.

Copper fertilizers increase the yield of spring wheat by 0.2-0.5 t/ha, barley by 0.2-0.3 t/ha, oats by 0.4-0.6 t/ha, corn green matter by 2.1 t/ha, and cobs by 9-13%. Copper fertilizers improve product quality: protein content in cereal grains, vitamins in vegetables, fruits and berries increase, fiber quality of flax and hemp improves.

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 and Research Institute named after D.N. Pryanishnikov, 2017. – 854 с.