Relevance. Over the past few years, anthropogenic pressure on agrobiocenoses has been intensified by various pollutants, in particular heavy metals (HM), which contaminated more than 20% of the arable agricultural of Ukraine. Among them, mercury, cadmium and lead are characterized by high resistance, high toxicity expressed cumulative properties and belongs to the dangerous elements of the first class subject to continuous monitoring.

With the gradual growth of the concentration of mobile forms of heavy metal ions in the soil environment, their intense accumulation and redistribution in plant tissues, inclusion in metabolic processes, which leads to morphological and biochemical changes that manifest in suppressing the growth and development of plants, leaves of chlorosis, necrosis of the apex and edges of leaves, dying roots, etc.

Therefore, today is a very important is research and practical application in the specific soil and climatic conditions of an efficient and accessible ecologically safe system of fertilizer the vegetable crops, which will contribute to high-speed detoxification of cultivated soil, contaminated by heavy metals, restoring fertility of soil, increasing the buffering properties of soil systems, promoting the production of the ecologically safe production of white cabbage.

Analysis of recent research and publications. Phytotoxicity metals and plant resistance to them depend on many conditions. The resistance of plants to a single metal, as a rule, does not apply to others. The phytotoxicity of metals also depends on soil factors such as pH, cation exchange capacity of the soil, granulometric composition, clay and organic matter content, availability of nutrients during the vegetation period.

One of the most common vegetable plants in Ukraine is whitehead cabbage. However, biological stability (tolerance) plants from the Brassicaceae family to toxic effects of heavy metals is low, which is due to genetic features. It should be noted that the biological stability of white cabbage against the toxic effects of heavy metals is low because the exceeded levels of maximum permissible concentration (MPC) of hazardous mobile forms of Pb²⁺, especially in acidic, poor in humus content and clay, light granulometric composition soils can reduce the yield and quality of white cabbage.

The purpose of research. The purpose of the research is to study the effect of organic, mineral and organic-mineral systems fertilizing in combination with liming on the phytoproduction parameters of white cabbage plants, depending on the level of soil pollution with lead.

Materials and methods.

In the conditions of the Western Forest Steppe zone of Ukraine studied the effect of fertilizers and meliorants behavior of lead in the system "soil-plant". In particular, the study was intended to study the influence of the effect of different levels of soil contamination on the fhytoproductivity of white cabbage plants in different phenophases.

Sowing of white cabbage (variety Yaroslavna), as a test-plant was carried in second decade of April in previously contaminated of soil with lead. Salt Pb(CH₃COO)₂, were used as the pollutants that were introduced as an aqueous solution in simulated contamination levels 1; 3; 5 MPC in the total forms separately in autumn in soil in 0-20 cm depth and in a two week later there was applied the meliorants CaCO₃ at the norm 5 t/ha (by hydrolytic soil acidity) according to the scheme of experiment. The 1 MPC for Pb made 32 mg/kg soil. On the control variant salt of heavy metals was not introduced.

The soil of experimental plot is a dark gray podzolic whith light granulometric of composition. The mineral fertilizer nitroamofos of brand 16:16:16 and the organic fertilizer Biohumus according to the scheme of experiment were applied in early spring. The soil of experimental field area is a dark gray podzolic whith light granulometric of composition.

The following factors were studied in the laboratory-field model experiments: Factor A – the levels of soil contamination by lead; Factor В – the fertilizer system and meliorants. The scheme of the field micro-plot two-factor experiment concerning the growing of white cabbage included such variants: 1) Control variant (without fertilizers);  2) N₁₃₆P₁₃₆K₁₃₆;   3) Biohumus 8 t/ha; 4) N₆₈P₆₈K₆₈ + Biohumus 4 t/ha;            5) N₁₃₆P₁₃₆K₁₃₆ + СаСО₃ 5 t/ha;  6) Biohumus 8 t/ha + СаСО₃ 5 t/ha; 7) N₆₈P₆₈K₆₈ + Biohumus 4 t/ha + СаСО₃ 5 t/ha.

We determined the concentration lead in the plants of white planet by the method of atomic absorption spectrophotometry. Samples of cabbage plants for the biometric measurements were taken on five typical plants from each micro field area in the main phases of the vegetation: 1) the formation of the socket of the leaves;               2) tightening the head; 3) technical maturation (during harvesting and harvesting). The following phytoproduction parameters were determined: plant height; diameter of the socket of the leaves; the area of the leaf surface; head diameter; height of the cabbage stalk; head mass; yield.

Results and discussion. The results obtained indicate, that phytoproduction parameters of white cabbage plants depend on factors such as: soil and climatic conditions, the fertilizer system, meliorants and the levels of soil contamination by lead.

It must be noted, that by increasing the level of soil contamination by lead from 1 to 5 MPC there was observed the only tendency to the increase of concentration of heavy metals mobile forms in the soil of all variants, and thus intensified biological absorption of metal ions plants cabbage which was contributed to the increased phytotoxic effect of lead.

Some regularities in the distribution of lead in cabbage heads were noted. In particular, concentration of lead in the outer stem of cabbage was 8-12 times larger than in the head, because the root system are the first organ and biological barrier to the transport of metal ions from the soil.

The research has established, that lowest concentration of lead in cabbage plants was noted for the aplication of organic and mineral fertilizers in combination with liming of soil at norm N₆₈P₆₈K₆₈ + Biohumus 4 t/ha + 5 t/ha CaCO₃. On this variant (without metal), the concentration of lead in the heads of cabbage decreased, compared with the control (without fertilizers) on 0.176 mg/kg, or 73.9%, while in the outer stem of cabbage on 1.187 mg/kg or 61%. The application of the same norms of fertilizers and ameliorants, but at a level of soil contamination of 5 MPC, the concentration of lead in the head of white cabbage decreased to control on                0.265 mg/kg or 38.3%, while in the outer stem of cabbage on 2,235 mg/kg or 23,5%.

We observed a general tendency in all variants of the experiment, namely, with increasing levels of soil contamination, the phytotoxicity of lead increased, which manifested itself at the suppression of growth processes already in the first phenophases, up to technical maturation, and consequently it affected the reduction of phytoproduction parameters of cabbage plants: height of plants, the diameter of the socket, the area of the leaves, the height of outer stem of cabbage, the diameter and the mass of the head, and in the final result of decrease yield.

On the basis of the results of laboratory and field experiments, it has been established, that the effectiveness of fertilizers and meliorants in reducing the phytotoxic influence of lead on the phytoproduction parameters of cabbage plants was manifested differently. Thus, the application of only one organic fertilizer in the full norm Biohumus 8 t/ha proved to be more effective in reducing the phytotoxicity of lead than the application of mineral fertilizers nitroamofoska in the full norm of N₁₃₆P₁₃₆K₁₃₆ kg/ha active substance.  But use of organic and mineral fertilizers at half norm at N₆₈P₆₈K₆₈ + Biohumus 4 t/ha found the slightest phytotoxic influence of lead on cabbage plants. However, with the application of the same fertilizer standards, but with the background of liming of the soil (options 5 to 7), all the growth processes were much better, and the phytoproduction parameters of cabbage plants were higher, in comparison with other variants, where not application meliorants. Such a measure as liming allowed to significantly reduce the mobility of Pb²⁺ in the soil and to reduce the phytotoxicity of lead during the vegetation, and in general, contributed to the production of high yields with good quality products of white cabbage.

Experimental studies revealed a sufficiently close correlation between the amounts of fertilizers and meliorants and phytoproduction indices of white cabbage plants, as well as levels of soil contamination by lead in all phenophases.

By analyzing the dynamics of growth and development of white cabbage plants in various phenophase, it should be noted that the aplication of fertilizers and meliorants into various levels of soil pollution with a lead had a major influence on the phytoproductivity of plants. So, at a level of soil contamination with lead 5 MPC in the phase of formation the head, the highest plant height is 34 and 36 cm, the diameter of the socket is 15.0 and 46.9 cm, the leaf area is 36.96 and 38.84 thousand cm²/ha, the diameter of the head 14,1 and 15,3 cm were noted in 6 and 7 variants for the introduction of fertilizers and meliorants at norm Biohumus 8 t/ha + 5 t/ha СaСO₃ and N₆₈P₆₈K₆₈ + Biohumus 4 t/ha + 5 t/ha СaСO₃. Accordingly, by application of the above norms of fertilizers and meliorants, the yield of white cabbage was the highest and amounted to 90.3 and 94.6 t/ha, while in the control (without fertilizers) –          67.0 t/ha.

Conclusions and perspectives. The results of researches have revealed, that the highest phytoproduction parameters of white cabbage plants (height of plants, diameter of the socket, leafs area, head diameter, height of external cabbage stalk, head mass, yield) noted by application of the organic and organic-mineral fertilizer system at norms Biohumus 8 t/ha + CaCO₃ and N₆₈P₆₈K₆₈ + Biohumus 4 t/ha + CaCO₃ 5 t/ha.

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