The influence of deep loosening on the ecological and meliorational state of drained mineral soils

The existing problems of energy, water, and food crises and climate changes determine the need to implement appropriate adaptive measures to improve the ecological and reclamation state of drained mineral soils. For the application of deep loosening of the soil as an adaptive agromelioration measure, a transition from traditional crack loosening of the soil and strip loosening of the soil to improved technologies of continuous layer-by-layer loosening of the soil based on energy-efficient and moisture-regulating principles is proposed. Their comparative evaluation according to the main indicators of overall efficiency was carried out on drained mineral soils of a representative object in the Western Polissia zone of Ukraine. According to the results of the evaluation of various technologies of deep soil loosening, it was determined that the technologies and technical means of continuous deep loosening of the soil have an advantage in all main indicators: agrotechnical, water-physical, energy, technological, ecological, and economic. In particular, the moisture availability of the soil increased by 27 % due to better accumulation of atmospheric precipitation, the yield of cultivated crops also increased by 20-30 %, and the aftereffect period increased to 4 years. This is a cost-effective and investment-friendly adaptive measure to ensure a satisfactory ecological and reclamation state of drained mineral soils (with an investment payback of 1 year). This provides modern principles of adaptive land use in changing climatic conditions and can be an effective alternative to expensive reconstruction and modernization of existing drainage systems.


Introduction
The current problems of energy, water, and food crises, as well as climate changes, determine the need to implement appropriate adaptive measures to improve the ecological and reclamation state of drained mineral soils.
In the zone of drainage reclamation, this is possible based on the development of a complex of adaptive, including agro-reclamation, measures.They are aimed at effective regulation of the water regime, regulation and accumulation of moisture in the soil profile and within the system, and improvement of technologies, and means of deep soil loosening according to energy-efficient and resource-saving principles.This will make it possible to effectively accumulate moisture in the soil profile and on the massif to be drained, to increase its moisture supply [1].

Analysis of previous studies
The positive aspects of using deep loosening as an effective agromelioration measure on sodpodzolic soils in the Western region of Ukraine have been shown in many studies.At the same time, it was noted the presence of negative agroecological and man-made components of impact on the soil by technical means for its implementation [1].
Some functional advantages of applying deep layer-by-layer loosening on over-moistened mineral soils using strip technology were noted and used by Kozhushko based on the developments of Kravets regarding a trenchless multi-tier soil loosener [2].
Depending on the hydrological, soil, and other conditions, continuous, strip, or crack loosening (cracking) is traditionally considered and used [1].
Traditional deep loosening of drained soils using slit or strip technologies is used only as an auxiliary measure to increase the efficiency of drainage using deep looseners mainly of the riser type.At the same time, only local influence is actually carried out on the active part of the soil massif (the active root layer and the aeration zone of the drained soil) with the formation of vertical filtration channels for the intensification of drainage of surface runoff.This really contributes to the strengthening of the technological effect on drainage, but at the same time, it strengthens the washing water regime in the soil, which over time leads to the impoverishment of the fertile layer and causes a negative ecological effect.
At the same time, the designs of traditional deep looseners actually perform rather coarse loosening, which does not provide the necessary quality of soil structure in accordance with agrotechnical recommendations.They compact the soil of the walls of the incised cracks, require significant energy expenditure during loosening, and have insufficient loosening completeness and the duration of its aftereffect [3].
Therefore, the use of deep loosening as an effective adaptive measure is restrained by the imperfection of existing technologies and means that do not provide the necessary quality and effectiveness of loosening in accordance with modern conditions and requirements.
Research methodology.For a comparative evaluation of the effectiveness of the application of various variants of deep loosening of drained mineral soils on a representative object for the conditions of the Western Polissia of Ukraine, experimental studies were carried out using the main methods of the general theory of the experiment (analytical, experimental and statistical), mathematical modeling and a machining experiment using modern information and computer technologies.
According to the obtained experimental results, predictive calculations were made based on the use of an appropriate complex of forecasting and simulation models, which includes a local climate model, models of the water regime and water regulation technologies of drained lands, a model of the development and formation of the crop of cultivated crops, which are implemented on the basis of a long-term forecast [4].
For an approximate assessment of the ecological sustainability of the researched measures, the degree of consideration of the factors of ecological reliability of their operation and to maintain favorable natural and reclamation and soil regimes within the project term, the calculation of the coefficient of ecological reliability (k n ) of the operation of the reclamation system was carried out based on the set of relevant physical indicators of ecological efficiency (indicators water regime, indicators of salt regime and productivity of drained lands).The ecologically optimal option is considered to be the one for which the coefficient of ecological reliability is in the interval of values k n = 0.5...1.0,in addition, the coefficient of ecological reliability indirectly reflects the ecological and melioration state of drained mineral soils [4].

Research results
On the basis of the generalization of existing and our research, we scientifically substantiated the need and possibility through improved energy-efficient and moisture-regulating technologies and technical means of deep loosening to influence the improvement of the technical, technological, and economic efficiency of the use of drained mineral soils.
Deep loosening changes the macrostructure of drained mineral soils and affects the macroaggregate state of soils, their density and porosity, water-physical properties, and, accordingly, the ecological and melioration state of drained mineral soils and the conditions for the development of cultivated crops and productivity (figure 1).
To ensure the implementation of the necessary improvement of deep loosening for modern conditions and requirements, a transition from the traditional widely used crack and strip loosening technologies to continuous layer-by-layer deep loosening of the soil differentiated by depth is proposed.This soil loosening method has been improved according to energy-efficient and moisture-regulating principles, and according to tiered technical means [5].
The improved technology and means of deep continuous loosening make it possible to improve the structure of the soil, which is developed in each horizon, layer by layer.At the same time, it makes it possible to differentiate the value of its loosening by a depth of up to 0.6 m.
Implementation of continuous deep loosening with mechanical reformatting of the macroaggregate and granulometric composition of the soil massif with its layer-by-layer distribution according to agrotechnical recommendations affects the water-physical properties of the soil.It is also decisive for the technological and physical prerequisites for the creation of favorable water-air and natural-ameliorative regimes, and, therefore, the provision of the necessary economic and ecological effects [1].
The formation of a granular and fine-grained structure makes it possible to effectively use the moisture-accumulating potential of the soil.This is done by the formation of a large surface area of soil particles and small gaps between them in the zone above the plow sole, where the root systems of most agricultural crops are potentially located.
The formation of a large-and medium-granular structure to the depth of the drainage makes it possible to quickly remove excess fluid.This excess is removed through the increased gaps between soil particles and simultaneously accumulates in the soil due to the formation of a sufficient surface area of soil particles.The formation of a medium-granular structure in the upper quarter of the upper layer protects the accumulated moisture from excessive evaporation from the surface and weathering.
As a result, a moisture-accumulating structure is obtained in each of the soil layers.This structure is appropriate for the purpose of each layer: with maximum moisture accumulation potential in the upper part of the soil and sufficient water permeability with simultaneous moisture accumulation in the lower part of the soil profile.
The proposed design of the deep loosener for improved loosening is a frame with bearing risers.Soil-loosening working bodies are attached to them in the form of the conjugation of a plowshare with a concave arrow-shaped soil-loosening element of variable curvature.The shape and parameters of the surface of this element determine the necessary deformation, stress, and, therefore, crushing of the soil layer.The general layout of the deep loosener is determined by the spatial distribution of the soil-loosening working bodies in three perpendicular directions (figure 2) [6].
Comparative field production tests of various technologies and means of deep loosening were performed at the facility of the Private Agricultural Enterprise "Myrne" in the Kostopil district of the Rivne region (Ukraine) on an area of 25 hectares [6].
Soil conditions: sod-podzolic clayey sandy soils with a content of physical sand in the arable horizon of 58.3 % (0...20 cm) and in the subsoil layer -79.8%, with a filtration coefficient of the arable horizon -0.13... 0.4 m/day, and at a depth of 20 cm or more -0.13...0.003 m/day.
The study of the influence of various technologies and deep loosening means on the waterphysical properties and agro-melioration state of drained mineral soils was solved by conducting  Table 1 presents a generalized comparative characteristic of the values of the main indicators of water-physical properties in the 0.6 m soil layer averaged over time (by the after-effect period) and plane (by the soil profile) and by different types and variants of its loosening.The term of effective technological aftereffect of the considered methods of deep loosening of drained mineral soil was: crevice soil loosening -1 year; strip soil loosening -3 years, continuous soil loosening -up to 4 years.
Table 2 presents a generalized comparative characteristic of the averaged values of the main agromelioration indicators of a layer of loosened soil of 0.6 m with a change in the supply of productive moisture and according to the most universal indicator of the productivity of cultivated crops for variants of its loosening.
The best results of deep loosening of mineral soils are achieved when using continuous  3 .In addition, the possibility of predicting and obtaining the structure in any horizon of the vertical profile of loosened soil due to the possibility of adjusting the parameters of the working body of the deep loosener was proven.At the same time, unlike other technologies, the optimal structure of loosened soil was achieved: in the arable layer, 55...60% by weight of soil aggregates with a diameter of 10...50 mm; the remaining 40% -by the total weight of aggregates with a diameter of less than 10 mm and greater than 50 mm, and in the sub-arable horizon with a diameter of 20...50 mm -70...80%, and in total aggregates with a diameter of less than 20 mm and larger than 50 mm -20 ... 30%.According to research results, deep loosening also has a positive effect on the temperature regime of the soil, especially the arable horizon, where when the air temperature increases, the maximum temperature in the loosened soil becomes lower than without loosening.
Under the action of deep loosening, the depth of soil freezing decreases by 8...12 cm, and thawing is accelerated by 2-3 days in the spring.This is especially characteristic of the first year after the effect.
Moisture evaporation is related to temperature and water conditions.Deep loosening, breaking the capillary connection in the upper horizons, reduces the intensity of capillary nutrition and, accordingly, reduces its evaporation from the soil surface.
According to [7], deep loosening can be a mechanism that contributes to reducing the evaporation of other greenhouse gases from the soil surface by stimulating their accumulation and absorption deep in the soil mass rather than in the upper soil layer.At the same time, loose soil macroaggregates with a diameter of 2...8 mm are characterized by 51% better-absorbing properties (over a total 20-day period) than soil macroaggregates with a diameter of up to 2 mm.
In addition, the deep loosening carried out accordingly will contribute to the translocation processes of moving soil organic carbon into the depth of the massif, which are one of the methods of its sequestration.The measured rates of carbon sequestration by the soil range from 50 to 1000 kg/ha/year.The global carbon sequestration potential is 0.9...10.3Pg/year, which can offset from one quarter to one third of the annual increase in atmospheric carbon dioxide, which is 3.3 Pg/year.The cumulative potential of soil carbon sequestration for 25-50 years is 30-60 Pg [8,9].
Table 3 shows the comparative efficiency of using different variants of deep loosening on drained mineral soils according to the results of field experiments.
The obtained results of the harvest of cultivated crops adequately describe the achieved indicator of the improvement of their growing conditions and ensure their increase on average The results of the analysis show that the method of continuous loosening of the soil provides a greater increase in the yield of cultivated crops than with crackted or strip loosening of the soil.This not only compensates for the cost of its implementation, but also creates a profit.
According to the results of predictive and simulation modeling using the appropriate set of models [4,10], the effectiveness of the application of improved continuous loosening of the soil during the growing season was determined.This was carried out in combination with various methods of water regulation of drained mineral soils on the example of the studied object (soilsandy loam, area -10 ha, cultivated crop -perennial grasses for hay) for the estimated dry growing season under the conditions of heat and moisture supply (p = 70%).
The presented data show that the application of improved continuous loosening of drained mineral soils against the background of preventive sluicing in the estimated dry growing season increases the accumulation of precipitation by more than 90% and increases the moisture availability of the soil according to the n(IW ) indicator by 27%.At the same time, the positive effect is partially preserved after 1 year after the action with sufficient environmental reliability.
The efficiency of the technology of water regulation of drained lands (PS + DL) is similar to the moisturizing sluicing (MS, subsoil moistening) according to a set of technological and ecological indicators.At the same time, this method does not require additional costs of irrigation water for moistening the soil massif with lower material costs.
The summarized results of determining the economic efficiency of investments in the reconstruction and modernization of drainage systems using various technologies and means of deep loosening according to the appropriate methods and models [11] are presented in table 5.
The calculations performed to determine the comparative economic efficiency and investment evaluation of various options for deep loosening of drained mineral soils confirm the sufficient feasibility of their use in projects of reconstruction and modernization of drainage systems in the Western Polissia zone of Ukraine.
Thus, all considered technologies of deep loosening of the soil are profitable and economically beneficial.At the same time, the most technologically, economically, and ecologically effective is the improved continuous deep loosening of the soil.The technology and means of deep continuous loosening of the soil, which has been improved according to energy-efficient and moisture-regulating principles, make it possible to improve the macrostructure of the active layer of drained mineral soils layer by layer to a sufficient depth.This is done in order to influence their water-physical properties, water, air, heat, and other ecological components of the natural-ameliorative regime of the soil massif, which is positively reflected in the conditions of the development of agricultural crops and their productivity.

Conclusion
According to the results of the evaluation of various technologies of deep soil loosening, it was determined that the technologies and technical means of continuous deep loosening of the soil have an advantage in all main indicators: agrotechnical, water-physical, energy, technological, ecological, and economic.In particular, the moisture availability of the soil increased by 27% due to better accumulation of atmospheric precipitation, the yield of cultivated crops also increased by 20-30%, and the aftereffect period increased to 4 years.This is a cost-effective and investment-friendly adaptive measure to ensure a satisfactory ecological and reclamation state of drained mineral soils (with an investment payback of 1 year).This provides modern principles of adaptive land use in changing climatic conditions and can be an effective alternative to expensive reconstruction and modernization of existing drainage systems.

Figure 1 .
Figure 1.Structural and hierarchical scheme of the necessary principles of improving technologies and technical means of deep loosening of draining mineral soils based on consideration of the interaction between the parameters of heterogeneous elements.

Figure 2 .
Figure 2. Tiered deep loosener: a) -construction, b) -loosening of the cross profile of the soil; c) -action on the element of the soil layer, d) -the principle of soil grinding; 1 -structural loosening; 2 -loosening by chipping; 3 -soil layer; 4 -working bodies.

Table 2 .
Comparative characteristics of the main agromelioration indicators of the 0.6 m soil layer according to loosening options.
2deviation from control loosening based on the use of a multi-layer deep loosener.At the same time, the density of the soil in the arable soil layer decreased to 1.1...1.15t/m 3 , and in the sub-arable soil layerto 1.2...1.3t/m

Table 3 .
Comparative effectiveness of deep loosening on drained mineral soils.

Table 4 .
Comparative characteristics of indicators of technological and environmental efficiency according to research options.-productive moisture reserve in the calculated soil layer, m 3 /ha; W P -weighted average productive moisture reserve in the estimated soil layer for the growing season, m 3 /ha; n(IW ) the duration (part) of the optimal moisture supply of the estimated soil layer for the growing season; OR -amount of effective atmospheric precipitation during the growing season, m 3 /ha; EF -value of the effective value of the total evaporation during the growing season, m 3 /ha; K ycrop yield reduction factor; Y a -actual yield, c/ha; H -weighted average level of groundwater, m; k r -the coefficient of ecological reliability.

Table 5 .
Comparative characteristics of indicators of technological and environmental efficiency according to research options.