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Table 4. - The yields of green biomass and seeds of Columbus grass (t/ha)
Treatments Green biomass seeds
No fertilizers 1196.7±36.4 23.6±0.8
N,nnP7An 1757.8±30.6 29.8±0.9
N P K 200 140 inn 2119.2±59.4 33.6±1.1
N P K 300 210 150 2101.7±57.7 32.3±0.9
As can be seen from obtained data, the yield of green biomass of Columbus grass depends either from climatic factors or from rates of mineral fertilizers. The highest yield obtained in treatment N200P140K100 Further increase of fertilizers did not increase the yield and productivity of plants.
It is necessary to point out that during second cutting the yield was higher which can be explained by increase of air temperature and solar radiation intensities as well as with optimal branching of plants. Thus, plants of spring planting during first cutting had 4-5 lateral shoots, after first cutting branching intensity is increasing (up to 8-10 shoots). After second cutting it is formed 6-7 lateral shoots, climatic changes occurs (daily temperature changes, shorter days) and consequently the growth intensities also decreases.
Seeds production of Columbus grass varied also depending from applied mineral fertilizers. Thus, as it can be seen from table 4 in the treatment without application of mineral fertilizers seed production was 2.36 t/ha, in the treatment N200P140K100 the yield of seeds was 3.36 t/ha. It was stated that increase of applied mineral fertilizers caused to decrease of seed yield.
Conclusions. It was shown that in flowering of plants the size of a sheet index reaches the greatest size and the maximum of net productivity of photosynthesis is revealed. It is noticed that the yield of green biomass of Columbus grass varied from 11967 to 21191 t/ha in dependence from cultivation conditions and climatic factors. Application of mineral fertilizers leads to sharp increase of productivity of plant.
References:
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Jabbarov Zafarjon Abdukarimovich, National University of Uzbekistan, Associate professor, Department of Soil Science E-mail: [email protected]
Substantiation of the change of chemical content of the soils polluted by oil and oil production
Abstract: The change of organic and chemical content of desert soils polluted by oil and oil products has been studied in this article. The humus and carbon contents have been analyzed by up-to-date methods. Keywords: soil, oil and oil products, pollution, humus, carbon, cations.
In the soils of oil and oil polluted soils the total carbon content increases, destroys the biochemical balance, dehydrogenase, urease, phosphatase enzymes and the nitrifying process are intensified [1; 2]. The optimality of soil properties determines the self-cleaning process of soil that soil respiration, enzyme activity and plant cover [3; 14], management of microorganisms community, activity of soil humic acid [4; 5] are important measures of the soil.
In purification of the soils polluted oil and oil products the microorganisms, their consortium, the biotechnological approach based on strains and the phytoremediation method can be effective [6; 7; 8; 9; 10; 13; 15; 16]. Oil hydrocarbons affect on soil mineral, organic and chemical contents, physical and biological properties, plants as well as anions and cations, pH change, carbonate amounts and to the increasing of salt content in soil that are visible [11; 12; 17; 18].
Oil and oil products are complex pollutants that effect on soil overall. In initial period of pollution the microorganisms, plant cover can be affected, than soil physicochemical properties might be changed and in its turn it impacts of changing the soil chemical content. Moreover soil carbon nitrogen ratio is misbalanced and organic carbon content increases as well. If soil pollution level till 5%, the humus content does not change, if pollution level reaches from 25 to 97%, the humus amount decreases, resulting breakdown of humification process and purification measures can only be effective in rehabilitation of pollution prevention.
Oil doses can effect to the soils differently, for instance, sorghum cropped in 0.2, 0.4, 0.6 and 0.8 ml/kg doses that after 4 weeks their effect has not observed. The organic carbon, nitrogen and magnesium contents after pollution than control, the phosphorus content was vice versa. The increase of oil amount in soil,
Section 1. Biology
the Fe, Cu, Zn and Pb contents increased [19]. Some authors have studied the change of nutrients and carbon content. For instance, in the soils treated with 10 g/kg dose of diesel bacteria, available carbon, nitrogen and phosphorus elements have degraded within 15 and 40 days. Studies concluded that the degradation goes faster in forest soils than savanna soils [20]. It is observed the increasing of organic carbon in oil polluted soils. The increase of acidity in 0.1-0.3 pHKCl impacts on available form of nitrogen, phosphorus and potassium in soil. Besides, oil pollution leads to technogenic salinity, mostly the salinity type would be chloride. In providing recultivation measures it is necessary to apply the meliorants with calcium (gypsum, borate, calcium carbonate etc.) and in salinity high local areas it is more effective salt washing measures as well [21].
The study areas are situated in two regions of Uzbekistan, Kashkadarya and Surkhandarya, there are five soil types chosen for our researches. The main soils of study areas are sandy soils and they spread around of pollution sources "Kukdumalak", "Zevarda", "Khovdak" "North Oknazar" and "Kakaydy" oil fields. These soils form in the sandy areas that stabilized with plant species. Study objects in Surkhandarya region oil field "Tashkuduk" (Termez district), "Kakaydy" and "Khovdak" oil fields (Djarkurgan district), in Kashkadarya region "Kukdumalak" oil field (Mirishkor district),
Mubarak oilgas (Mubarak district) with soil types sandy desert, grey-brown, takyr, meadow-saz soils were investigated. Humus spots in some cases reach 25-30 cm with amount of 0.2-0.5% (without oil pollution), groundwater lie more than 5 meters.
The laboratory work was done at Czech University of Life Sciences Prague by the support of Erasmus Mundus CASIA Project and at National University of Uzbekistan, Department of Soil Science. Soil organic content was determined by Tyurin modification method, the cation content was done by Aqua regia method. Soil sampling was as following: the distances from "Kukdumalak" oil field 1, 3, 6, 9, 13 and 16 km accordingly with PK-10-1; PK-10-4; PK-10-6; PK-10-9; PK-10-12 and PK-10-14; in the same distance from "Khodvak" oil field samples were named PX-10-2; PX-10-5; PX-10-7; PX-10-10; PX-10-13 and PX-10-15 respectively. Samples were named according to oil field name, so that "PK"-Profile Kukdumalak, "PX"-Profile Khovdak.
These soils are less supplied with organic matter, so it can cause the oil pollution more serious problem. In the soil samples of PK, the humus content in unpolluted soil is 1.5-1.62% in average and organic carbon is 0.88-0.95%. The humus and carbon content decreased under oil pollution in 24% and 14% respectively. In PX samples, humus and carbon content decreased at 48% and 31% accordingly (table 1).
Table 1. - Humus and organic carbon contents in the soils polluted by oil and oil products
PK-10-1 PK-10-4 PK-10-6 PK-10-9 PK-10-12 PK-10-14 PX-10-2 PX-10-5 Px-10-7 PX-10-10 PX-10-13 PX-10-15
Carbon content, % 0,83 0,69 0,61 0,71 0,8 0,70 1,43 0,54 0,59 1,22 1,14 0,94
Humus content, % 1.43 1,18 1,050 1,22 1,38 1,20 2,46 0,93 1,01 2,09 1,96 1,61
Table 2.
Cox (%) Humus (%) Evaluation
<0.6 <1.0 Very low
0.6-1.1 1.0-2.0 Low
1.1-1.7 2.0-3.0 mediium
1.7-2.9 3.0-5.0 high
>2.9 > Very high
It can be proved that the decreasing of humus content in desert soil polluted with oil and oil products as follows:
First point — the physical properties of soil such as density increasing and moisture decreasing under oil pollution can lead to;
Second point — the humification process ongoing in soil breaks down;
Third point — if amounts of chemical substances in soil (such as oil and oil products, heavy metals, salts etc.) reach the maximum allowable concentrations can cause damage of whole processes in soil;
Fourth point — plant cover richness is decreased, in some areas totally destroys and it its turn the biomass incoming back to soil decreases sharply;
Fifth point — the microorganisms' amount and their physiological groups can decrease and if pollution is high in level they can negatively impacted by.
Furthermore, oil and oil products causing the soil chemical content lead changing of the element content of soil. The cations content changes differently according to pollution type (pic. 1).
In desert soils before oil pollution are more reach of calcium and magnesium as well as sodium content is high in sorption com-
plex. Calcium content is 8-12.5 mmol (+)/100 g, after pollution it raised to 12.3-20.5 mmol (+)/100 g.
Soil sorption complex in oil polluted soils may be affected by the substances and matters buried at the same time with oil water such as mineral salts, additives and other substances that leading to fluctuations of cations content in sorption complex of soil of these areas.
Oil and oil products influence on soil physicochemical, biological properties and features somehow effectively and negatively. Especially it is observable decreasing of soil microbial content, self-cleaning ability of soil decreases as well. The pollution with more than 4 years seriously affect to soil biological community and its functions.
Thus, it is necessary to provide complex remediation measures at polluted sites with applying modern approaches. The bases of the remediation technology are bacteria strains with ability to degrade oil and oil products, and agricultural crops with phytoremediation ability that when they will be introduced in association the high results are achievable.
Pic.1. Cations' amounts in the soils polluted by oil and oil products in different level
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