The balance calculations in agriculture are the basis for assessing the value of land and determining how to use it effectively. Replenishing the humus balance in soils is a long and multifactorial process, and therefore requires considerable expenditures to control it. Therefore, scientists pay particular attention to the benefits and the need to create geoinformation portals, first and foremost, in the agricultural sector in order to create effective market-based tools for balancing soil quality. However, today Ukraine has little experience in creating portals and software for the implementation of soil fertility balance calculations in the online system for the purpose of organizing organic land use. The article deals with the methods of humus balance calculation and the formulation of the humus balance calculation task, which will take into account regional peculiarities of Ukraine's Rivne region with the possibility of scaling to other areas. A mathematical model of the corresponding problem using differential equations was constructed. A numerical solution was found and implemented as the e-calculator module of online information system. The integration of IT technologies with the example of humus balance e-calculator for organic land use will allow crop rotations modeling and volumes of organic fertilizer application to stabilize or improve the soil quality. The main task of the calculator was to provide specific recommendations for the land plot on the efficiency of its use. In addition, the information system provided the background information on the economic efficiency of the transition to organic farming, certification, processing and marketing rules. The user can independently specify the order of crops cultivation in rotation, the amount of organic fertilizer application and as a result will receive the possible variants of the total humus content in the soil, for different volumes of application of organic fertilizers (biohumus) using the e-calculator of humus balance. The testing and verification of the e-calculator was carried out on the last 40 years data of the Rivne branch of the Soils Protection Institute of Ukraine, taking into account the cultivated crops, the introduction of mineral and organic fertilizers.

The agrochemical state of sod-podzolic soils of thе Western Polissya is analysed area of next agro-industrial groups: 27b-sod-podzolic gley-dried clay-sandy, 14b-sod-podzolic and podzolic-sod gley clay-sandy soils; 5b-sod-podzolic and non-glued and gleyy clay-sandy soils on sandy sediments. The content of humus, alkaline hydrolyzed nitrogen, mobile phosphorus and exchangeable potassium in sod-podzolic soils on arable land, under pasture and hayfields has been investigated. Determination of agrochemical indexes of soils, conducted in the laboratory of analytical support of agrochemical and agro-ecological research and quality of products Rivne branch of the state institution "Institute of Soil Protection of Ukraine". As a result, a low and medium degree of land provision was found for the studied parameters (with the exception of mobile forms of phosphorus in the agricultural group 14b under grass) irrespective of their agricultural use. In terms of humus content, agricultural production groups 14b and 5b under haymasters have an average degree of provision (2,1-2,2%), 27b for arable land and 5b for pasture-low; on the content of alkali hydrolyzed nitrogen-very low (< 101 mg/kg); on maintenance the movable forms of phosphorus themiddle is educed (51-100 mg/kg); with the content of mobile potassium, the agricultural production group 5b has a medium the degree of availability (84 mg/kg), other study groups-very low (< 41 mg/kg of soil). From depth, the content of all studied parameters decreases. Studying the dynamics of these indexes during 2011-2015 it is not set substantial differences in the process of the protracted cultivating, only on plough-land of the use of sederal cultures in 2014-2015 assisted the insignificant improvement of content of humus and other agrochemical indexes. Analysing agrochemical properties it is necessary to mark expediency of their improvement by application of the organo-mineral system of fertilizer in connected with the periodic liming, and also the use of the sederal sowing with the aim of passing to the conduct of organic agriculture.

The study deals with the evaluation of drinking water quality in rural settlements of Hoshcha (Rivne) district of Rivne region. It has been analyzed the concentration of biogenic (copper, zinc) and nonbiogenic (plumbum, cadmium) heavy metals in the water of the wells in the villages of Sadove, Zhalianka, Yuchyn and Tuchyn and artesian wells in the village of Tuchyn during 2012–2018. The research has given fundamental sources of underground waters pollution with heavy metals. It has been revealed that in the water of the wells Cu and Zn concentration does not increase maximum permissible concentrations during the whole period of research. The study demonstrates that water quality of the wells springs is not appropriate to the standard indicators according to the plumbum and cadmium. The authors point out the increasing of maximum permissible Pb concentrations in the wells of the villages of Sadove by 1.02–1.37 times (2012–2014, 2016, 2018) and the village of Tuchyn by 1.17–2.07 times (2012–2018). It has been stated that Cd concentration increases maximum permissible concentration in the wells of the villages of Sadove (by 1.6–3.8 times), Zhalianka (by 1.8–2.5 times), Yuchyn (by 1.3–2.7 times) and Tuchyn (by 1.8–4.5 times). Under the conditions of optimal concentrations biogenic heavy metals are necessary to provide life activities and functions of physiological processes of all organisms. However, continuous consuming of drinking water that is polluted with heavy metals negatively impacts on the organism and may cause acute and chronic diseases. Their impact depends on the concentration of the element, characteristics and intensity of its getting, absorption speed, retention and removal speed, and also human’s general state of health. In the village of Tuchyn according to cuprum, zinc, plumbum and cadmium concentration the water of artesian wells is appropriate to the permissible standards during 2012–2018 and is suitable for consumption and use. It is obviously that the use of deeper underground water horizons provides the inhabitants of the village of Tuchyn with qualitative drinking water. In the water of settlements wells where the increasing of standard Cd and Pb concentrations was observed it should be developed and implemented effective measures to develop the water quality.

Метою статті є оцінка вмісту нітратів у воді колодязів та артезіанських свердловин сільських населених пунктів, шляхів їх надходження і потенційні ризики для здоров’я населення внаслідок перевищення нормативних показників. Проаналізовано нітратне забруднення води колодязів с. Садове, с. Жалянка, с. Ючин, с. Тучин та артезіанських свердловин с. Тучин Гощанського (Рівненського) району Рівненської області впродовж 2012–2018 рр. Зафіксовано перевищення гранично допустимих концентрацій нітратів упродовж усього періоду дослідження у колодязях с. Садове (у 1,67–3,11 рази), с. Ючин (у 1,24–1,68 рази) та с. Тучин (у 3,06–4,06 рази), що свідчить про тривалий період забруднення водоносного горизонту. Показано, що вода колодязів с. Жалянка та артезіанських свердловин с. Тучин за вмістом нітратів відповідає встановленим нормам упродовж усього періоду дослідження і придатна до споживання та використання. За вмістом нітратів у воді колодязів населені пункти можна розмістити так: с. Тучин > с. Садове > с. Ючин > с. Жалянка. Визначено усереднені значення добової дози нітратів, що надходять із питною водою до організму дорослих (0,38–2,69 мг/(кг×добу)) та дітей (0,69–4,84 мг/(кг×добу)). Показано, що середньодобове надходження нітратів із питною водою до організму дитини вище, ніж у дорослих. в 1,8 рази. Розраховано коефіцієнти небезпеки впливу питної води колодязів з різним вмістом нітратів на організм, що варіюють в межах 0,20–1,81 (дорослі) та 0,36–3,26 (діти). Висновки. Рівень неканцерогенного ризику для здоров’я дорослих і дітей змінюється від низького рівня до високого та залежить від концентрацій нітратів у воді колодязів. Для зменшення забруднення питної води колодязів нітратами необхідно оптимально використовувати добрива та пестициди, обов’язково дотримуватися часових інтервалів їх внесення. Також важливо підтримувати технічний стан колодязів та щороку проводити очищення і знезараження відповідно до санітарних норм та правил.

The study concerns with the changes of heavy metals concentration in the water of human-made objects (ponds and canals of drainage system). It has been revealed the exceeding of maximum permissible norm of Cu, Zn, Pb and Cd in the ponds, and the exceeding of maximum permissible norm of Pb and Cd in the canals of drainage system during the continuous time that certifies their permanent getting in the soils and waters from point and diffuse sources. The paper analyzes basic sources of heavy metals getting in the waters and their positive and negative impact on the biota. In order to increase ecological value of water objects and resources of agricultural lands it has been offered to use fertilizers and pesticides in a rational way, move to electric car use gradually, arrange landfills in a proper way, standardize algicidal fertilization, use fish fauna representatives to regulate number and algae biomass, equip the bioplateau and implement phytoremediation technologies with the aim to remove heavy metals from the soils and waters.