Groecological soils assessment of agrospheres urban system zones of influence

Abstract

The research in the agrosphere urban system zone of influence of Rivne city was conducted. For determinating of the territories, which are suitable for the cultivation of environmentally safe products, agroecological assessment of the agrarian soils of the agrosphere urban system zone of influence of Rivne city for an integrated indicator of the quality of soil cover has been carried out.

The purpose of the work is agroecological assessment of agricultural soils of the agrosphere urban system zone of influence . To achieve the purpose of the study, the following tasks were identified: to investigate the changes in fertility, environmental sustainability and sanitary-and-hygienic status of the agrosphere urban system zone of influence, to assess the qualitative state of the soil cover of the agrosphere urban system zone of influence and to distinguish the territory by the degree of suitability for the cultivation of environmentally safe products. Agrosphere urban system zone of influence is located within the West-Polis region, covering the eastern parts of the Volyn Polissya region, the Volyn Upland and the Small Polissya region. It is represented by the territories of seven administrative districts that border the city of Rivne. The study area is 6859 km2 and covers 157 rural and 7 village councils. The prevailing soils of the agrosphere are turf-podzolic, podzolic, gray, turf-gleyed and marshy soils, 60% of sod-podzolic soils are intensively used in agricultural production. 64% of the territory under study is agricultural land. The study used methods of systematic approach and system analysis. The assessment of the qualitative state of the soil cover of the rayon was carried out using a systematic approach to aggregating and integrating a number of initial baseline indicators for the subsystems: environmental sustainability of the soil (basic parameters of humus content, soil solution reaction); level of fertility (basic indices of nitrogen content that is rapidly hydrolyzed, content of mobile phosphorus, content of exchangeable potassium); sanitary and hygienic status (soil density 137, cyanium nitride and nitrogen content - 90 and heavy metal content such as zinc, mercury, cadmium and lead). Bringing the basic indicators to the normalized form was carried out according to the corresponding formulas.

Normalization of the baseline indicators was as follows: 1) as the ratio of the difference between the value of the indicator and the minimum indicator of the difference between the maximum and the minimum values - for indicators of increase in the value of which improves the state, or improves the quality (positive indicators); 2) as the ratio of the difference between the maximum indicator and the value of the indicator to the difference between the maximum and the minimum values - for indicators of increasing the value of which worsens the state, or worsens the quality (negative indicators).

For the minimum and maximum values of soil quality indicators, criteria and normative indices of suitability of agricultural lands for requirements of special raw material zones were taken. The agrochemical indicators were characterized by the reporting of the center of obscurricity, which determined: the content of humus - in accordance with Ukrainian national standardization system DSTU -4289, DSTU ISO-10694; pH - DSTU ISO-103940, GOST-26483; nitrification capability of DSTU ISO-4114; DSTU-4115; DSTU-4405; micronutrient content of the industry standard OST -10147-88.

Aggregation of indicators at all levels was conducted using weighted geometric estimates. To assess the agroecological state of the soil, a unified measurement scale was used according to which the soil condition was evaluated qualitatively and quantitatively: 0-0.2 - critical, 0.2-0.4 - threatening 0.4-0.6 - satisfactory, 0.6 -0.8 - favorable, 0.8-1.0 - reference. At the same time, it was considered that the degree of suitability of the soil is divided into unfit for the cultivation of environmentally safe products with an integral index of 0-0.4; Limited fit - 0,4, - 0,8 and suitable 0,8 -1,0.

As a result of the study, it has been established that the soils of the agrosphere urban system zone of influence are characterized by low and very low humus content. The content of humus in soils during 2001-2010 ranged from 1.7 to 3.5% (for the Polissya region, from 1.5 to 2.0%, for the forest-steppe zone from 2 to 4%). Only selected areas where the content of humus was more than 3% were noted. It has been established that the majority of arable land in the territory of village councils is limited in terms of the content of humus in the soil.

The soils studied are mostly slightly acidic, and only some are acidic or neutral. According to this indicator, the soils are limited to suitable and only certain soils are suitable for the cultivation of environmentally safe products.

The aggregate index of environmental sustainability of the agrosphere urban system zone of influence  for the 8th and 9th round of the survey is calculated. It has been established that this indicator decreases over time. The territory of the agrosphere is classified as a critical and satisfactory state, and the soils in question are unsuitable or limited in terms of the ecological sustainability of the soil.

The fertility level was studied based on the basic indicators of nitrogen content that is easily hydrolyzed, the content of mobile phosphorus and potassium. It was established that the level of soils hydrodilized nitrogen is very low and low with nitrogen content of 75 - 140 mg / kg. The analysis of soils by moving potassium showed that the soils of the village councils are characterized mainly by low (41-80 mg / kg soil) and medium (81-120 mg / kg soil) content. There is a slight decrease in this indicator in the 9th round of the agrochemical survey. We estimated the aggregate indicator of soil fertility in the agrosphere and found that significant changes in this aggregate in the 9th round of the agrochemical survey. Especially the situation deteriorated in the soils of village councils of Kostopil district. The change in the aggregate indicator in the direction of improvement to a favorable state is monitored in the soils of the village councils of Dubensky and Mlynivskyi districts.

It is established that the content of mercury in soils does not exceed the background values. In terms of lead, cadmium and zinc content, they significantly exceed the background values and MAC. The difficult situation has arisen in the Rivne, Zdolbunivskyi and Ostrozhsky districts, and there is also an overrun of normative values in the Dubensky, Kostopilsky, Zdolbunivsky and Goschansky districts. As a rule, these village councils are located in the zone of influence of highways both state and international.

Calculations of the quality state of the soil cover of the of the agrosphere urban system zone of influence have shown that its value ranges from 0.2 to 0.6 corresponding to a threatening and satisfactory state were conducted. The spatial analysis of the distribution of soils of the agrosphere by this indicator has been carried out and the territories that are unsuitable or restricted to grow environmentally safe products are defined.