Research into Comparative Performance of Different Tillage and Fertilization Systems Applied to Grey Forest Soil of Forest Steppe in Grain Crop Rotation

The paper summarises the results of the comprehensive scientific research carried out in the form of a two-factor stationary experiment (5 primary tillage systems × 3 fertilization systems) with rotation (2016–2020) of cereal crops (winter wheat – grain maize – spring barley – soybean) in grey forest fine sand and light loam soil. The effectiveness of the tested agricultural production method has been proven by the amplitudes of the actual crop ping capacities: winter wheat – 2.80–5.00 t ∙ ha –1 ; grain maize – 4.16–8.89 t ∙ ha –1 ; spring barley – 1.78–4.45 t ∙ ha –1 ; soybean – 1.02–3.17 t ∙ ha –1 . The rehabilitation of the physical, agrochemical and biological status of the edatope and the consolidation of the physiological processes in the grain cenoses achieved by the systemic approach to the soil tillage and fertilisation have provided for an increase in the natural biological potential of the plough land by a factor of 1.3–1.8 (from 2.96 to 5.21 t ∙ ha –1 of grain units, units for the equivalent measuring of different plant cultivation products). Factographic justification has been provided for the environmental, technological and technical-and-economic feasibility of implementing agronomic technologies based on the adaptive combination of mouldboard and non-mouldboard tillage (to a depth of 6–45 cm) and organic and mineral fertilization system (6.5–7.0 t ∙ ha –1 of plant cultivation by-products + N 70 P 58 K 68 ). In this case, the effective fertility of an area unit in crop rotation reaches 5.72 t ∙ ha –1 in grain units, the production cost of raised grain – 117 € ∙ t –1 , the earning capacity – 788 € (ha ∙ year) –1 , the level of plant cultivation profitability – 139%. In the comparable alternatives of the system-based soil tillage (every-year ploughing, subsurface blade tillage and especially tillage with disk implements), the indices estimated above are significantly lower.


INTRODUCTION
The transition of the agricultural sector to the market relations from diverse initial positions stipulates the coexistence of functionally different farming systems even within the same specific soil and climate region. The use of predominantly hybrid approaches is based on the following farming concepts: conventional, intensive, adaptive, soil protecting, ecological, resource conserving, balanced, sustainable, renewable, organic, environmental etc. (Baig & Gamache, 2009;Larocque, 2020). However, in all these cases, the rational combination of the mechanical tillage, fertilization, crop rotation and plant protection modules is an indispensable attribute of their efficiency. Today's spectrum of the practical agronomic process solutions employed by economic entities is Several researchers (Morgan, 2005;Friedrich & Kassam, 2009) point out that the implementation of the latest agronomic technologies takes place in the evolutionary way with imperative fulfilment of the preparatory and transition period conditions (cultivation, logistics and information support, staffing, meeting the social and economic demand). That is demonstrated by the propagation of no-till systems (official statistics on these technologies have been recorded since 1982), which -despite the boom in their advertising -currently cover only about 160 million ha, i.e., 12% of the world cropped land, while in Europe this figure is under 3% (Baker et al., 2007; Derpsch, R., Friedrich, Lindwall & Sonntag, 2010).
In the countries of Eastern Europe, the zoneadapted variable-depth tillage of the soil in field crop rotation systems with the use of all types of implements (chisel plough, plough, subsurface blade cultivator, heavy cultivator, disc tiller, compactor etc.) has been prevailing and, according to the long-term forecasts, will continue to dominate in the future. There are high hopes for the use of multifunctional modular combine units with the aim of the sparing use of resources and energy per unit of marketable output and the comprehensive remediation of agronomic landscapes. The need to substantially update the primary agronomic process procedures and tools is becoming relevant in view of the undesirable climate aridisation, the technical modernisation of the field husbandry, the universally adopted use of crop husbandry by-products in the capacity of fertilisers and also -due to the conflicts of the land laws (Farooq & Siddique, 2014;Kolomiiets et al., 2019;Kaminskyi et al., 2021).
The aim of the current study was to improve the performance of alternative tillage and fertilization systems in the grain crop rotation cycles used in the grey forest soil of the Forest Steppe region.

MATERIALS AND METHODS
The research was carried out over the 2016-2020 period in the stationary experimental field of the Department of Tillage and Weed Control, NAAS Institute of Field Husbandry National Research Centre, established in 1969 in the grey forest coarse dust and light loam soil in the northern area of the Right Bank Forest Steppe region. This paper refers, in particular, to the results of the sixth stage (reconstruction) of the stationary twofactor experiment: 5 alternative tillage systems using different production processes × 3 fertilization systems in the short grain crop rotation cycle, specifically: winter wheat -grain maize -spring barley -soybean.
The tilled soil layer (within the depth range of 0-45 cm) featured low natural fertility, because the grain-size composition was dominated by the fine sand fraction (53-56%), while the contents of silt particles (13-18%) and physical clay (22-24%) were insufficient for accumulative paedogenesis. That had been proven by the high steadystate bulk density equal to 1.50 ±0.1 g•cm -3 , the low humus content at a level of 0.9-1.3%, the sub-acid reaction of the soil solution at рН kcl -5.1-5.4; Н r -1.7-2.0 mg•(eq.) -1 per 100 g of soil, the low base saturation rate (V -75-79%), the insufficient content of exchange potassium (70-120 mg•kg -1 of soil) and the high content of labile phosphorus (165-180 mg•kg -1 ) according to the Kirsanov method. The following soil ecology indices had also been taken into account: the field water capacity at 22%, the available water range at 17%, the soil workability state water content at 14.5%, the annual total photosynthetically active radiation at 2.000-2.100 MJ•m -2 , the total of effective temperatures > 10 °С at 2.500 °С, the total precipitation at 350-670 mm, the hydrothermal factor at 0.8-1.3, the average soil quality index at 41-47 points, the bioclimatic potential at 2.1 (100 points).
The total area of a single plot was 200 m 2 , the recorded area -48 m 2 . The field experiment investigations were carried out with three replications using a split-plot design. In the design, the experiment alternatives were arranged in three rows systematically shifted relative to each other. The primary soil tilling was done with the use of PN-3-35 plough, PCh-2,5 chisel plough, PShchN-2,5 subsurface slitting cultivator, KPE-3,8 heavy erosion-preventive cultivator and BD-2,4 disk tiller. For the pre-sowing cultivation, an AKG-3 combined pre-sowing unit was used.
The following released cereal crop varieties were grown in the experiment: Polesskaya 90 winter wheat; Sontsedar spring barley; Arnica and Muza soybean; Oster mid-season maize hybrid. In order to protect the sowed plants against weeds, pathogenic agents and pests, an integrated protection system employing the present-day inventory of pesticides was used.
The statistical validity of the research results was assessed in terms of their variation range, standard deviation (S) and coefficient of variation (V, %) with the use of the PC and the Statistica 6.1 software.

RESULTS AND DISCUSSION
The agronomic meteorological conditions in the growing period (April-September): the mean monthly air temperature (18 °С) was 2.4 °С higher than the long-term standard air temperature, while the precipitation was noticeably deficient comparing to the long-term standard -156 mm against the normal 379 mm. At the same time, substantial variations were recorded in the atmospheric soil moistening: excessive -by a factor of 1.5-2.0 (May 2016 and 2020, June 2018); insufficient (-42-44% during June-July) and critically deficient -in August, when the long-term mean precipitation was equal to mere 22 mm (one third of the standard figure).
The type of the soil-forming process that takes place under the conditions of its cultivation directly depends on the input of the energy material -the mass of by-products, which in the experiments varied within the range of 9.16-11.05 t•ha -1 (Table 1) reaching the maximum in the case of the combined tillage system and incrementally decreasing after the conventional mouldboard ploughing (-6%) and deep and shallow subsurface loosening (-8.0 and -12.9%, respectively). In the yield of the post-harvest plant biomass, the share of top residues reached 61.7-62.3%, the rest was root residues.
The mathematical assessment of the mass of by-products by means of statistical analysis has proven that the mass of plant residues on the average for the experiment was within the range (X̅ ± Sx̅ ) of 6.24 ± 0.21 at a standard deviation (S) of 0.48 t•ha -1 . The average mass of root residues was significantly smaller, it was equal to 3.81 ± 0.11 t•ha -1 at a standard deviation of 0.26. It should be noted that both the indices featured insignificant variation, as indicated by the coefficients of correlation equal to 7.6 and 6.7%, respectively.
Taking grain maize cultivation (the most intensive primary tillage system) as an example, it has been established that only deep ploughing ensures the relatively uniform distribution of the unmarketable part of the preceding winter wheat harvest in the 0-30 cm layer. In the case of subsurface (nonmouldboard) tillage models, especially the annual disk harrowing to a depth of 6 to 12 cm, the typical result is the near-surface concentration (73-82%) of the mass of by-products and simultaneously the energy exhaustion of the 10-30 cm soil layer (Fig. 1). The research carried out in the past resulted in determining the optimum bulk density of the tilled soil layer in the period of active organogenesis: winter wheat 1.23-1.38 g•cm -3 , spring barley, panicum, sugar beet and maize -1.10-1.36 g•cm -3 . At the end of the crop growing period, it is acceptable for the soil to become compacted to a level of 1.45-1.50 g•cm -3 . This is directly related to the actual averaged (four crops) dynamics of the bulk soil density in relation to the applied tillage system (Table 2).
In particular, a significant decrease has been observed in the compaction of the 0-10 cm layer by the time of complete seedlings: from 1.36 g•cm -3 (variable-depth ploughing in crop rotation) to 1.27-1.28 g•cm -3 after applying combined and subsurface blade soil tillage technologies, further to 1.25-1.26 g•cm -3 in the case of annual shallow disk tillage in crop rotation. That is, the decompression effect due to the near-surface concentration of the aftermath plant residues from the preceding crops has been observed in practice.
In the middle of the crop growth period (time of flowering-grain formation) the above-mentioned relation becomes levelled off. At the same time, in the case of long-term non-mouldboard tillage to a depth of 6 to 12 cm, the lower part of the active root habitable layer (10-40 cm) remains compact at the first two recorded stages   Note: against background of mean by-product amount used in crop rotation at 6.5-7.0 t•ha -1 + N 70 P 58 K 68 .
The conclusion of the above-said is that the theoretically possible increase of the mass of byproducts from 3.0 t•ha -1 (soybean) to 20.0 t•ha -1 (maize) is accompanied by the temporary decompaction of only the 0-10 cm soil layer (by 0.1 g•cm -3 or 4.9%). The cause of that is obvious -the mass of the edatope solid phase is almost 75 times greater than that of the plant residues. Moreover, the latter are subject to continuous three-dimensional (physical and biochemical) destruction, which minimizes the expected development of the "skeleton effect". This conclusion does not apply to the technologies of direct sowing with the projective cover of the soil surface with plant residues at more than 70-80%, where mulching, shading, micro-climate etc. work in unison.
It should be noted that such an index of the physical mechanical properties of the soil as its hardness, is of great informative value, because it adequately and promptly diagnoses the forces required for wedging, shearing, cutting and crumbling in the operation of the tilling implement as well as the seed germination conditions and the possibility for root fibrillae to "populate" the interand intra-aggregate space. It is generally accepted that for high quality crumbling, the mechanical impact by the implement has to be in accord with the total shearing and rupture resistance and cohesion of the soil aggregates with minimal parameters at the lower plastic limit point (0.6-0.9 НВ or 2.94-3.24 MPa for absolute measurement of the researched edatope). Depending on the agronomic background, the hardness of tilled soil has to be within the range of 0.2-0.59 MPa. The tentative optimal parameters of the soil hardness, at which the additional loosening becomes unnecessary for the majority of chernozem soil types, are as follows: primary tillage for winter crops < 0.98 MPa, for spring crops 0.98-1.96 MPa, presowing cultivation 0.49-0.78 MPa, interrow cultivation 0.39-0.54 MPa, hardness of the plough pan < 2.94 MPa (Medvedev, 2013). Regrettably, there is no data here about the required phytosanitary soil conditions and the use of different masses of by-products.
In Figure 2, the soil hardness diagrams are presented for a tilled soil profile in the area of maize drills against the organic and mineral agronomic background. It has been established that at the initial stage (seedlings), the hardness of the 0-10 cm soil layer does not depend on the tillage method and is insignificant -0.21-0.42 MPa (Borys & Küüt, 2016). The 10-30 cm soil layer after shallow disk tillage differs substantially by its higher mechanical resistance equal to 0.36-0.64 MPa, as compared to the other primary soil tillage systems. In the adaptive tillage system used in crop rotation, after a single use of chisel ploughing before sowing grain maize, the minimal weighted mean hardness of the 0-30 cm soil layer settles at a level of 0.34 MPa, which is by 37% lower, than in the case of annual ploughing.
At the complete grain ripeness stage, the penetration resistance of the upper 0-15 cm soil layer in the case of deeper tillage systems increases to 1.27-1.47 MPa, after For assessing the soil water content parameters of the experimental field, the own criteria have been used basing on the optimal hydrological conditions of a field: water permeability > 60 mm•h -1 , available water reserve within the range of 0.6-1.0 of field water capacity in the 0-40 cm soil layer -47-70 mm and 170-220 mm -in 1 m layer, precipitation assimilation factor > 0.7, water content of the aeration zone 15-23%, of the soil workability state -14-15%.
The initial reserve of soil water (Table 3) at the stage of the spring resumption of winter wheat growth in the 0-40 cm soil layer against the background of variable-depth tillage in crop rotation (108 mm) significantly exceeded the level of the subsurface blade cultivation system (8%), the shallow disk tillage (14%) and to the maximumafter surface disk tillage (16%). The same pattern was observed in the 1 m soil layer: 200, 178 and 162-168 mm, respectively. Therefore, decreasing the depth of non-mouldboard soil loosening impairs the inter-seasonal atmospheric precipitation assimilation by 11-19% and has a negative effect on the ontogenesis of plants at the stages of full tillering -stem elongation.
By the time of harvesting, the reserve of available water in soil substantially decreased with all tillage systems, while partial differences between alternatives were observed as a result of the unequal water consumption by the plants for producing a unit of biomass.
The satisfactory provision of water in the 0-40 cm active root habitable layer in this period (45-68 mm), which was, however, different among the alternatives, indicated the characteristics of the aftereffect on the reproduction processes and the final yield of winter wheat produced by each of the tested soil tillage systems. In the cases of variable-depth subsurface blade and shallow disk cultivation, the water stock averaged for the growth period was 4-16% lower in comparison to the traditional and adaptive soil tillage technologies. The critical dehumidification of the soil (-15 -23% in the 0-40 cm soil layer and 14-19% in the 0-100 cm soil layer) was observed as a result of long-term surface disk tillage in crop rotation, which correlated with the deterioration of the physical condition of soil in this case.
In the field of spring barley, the initial reserve of available water (0-40 cm) was equal to 70-98 mm -a sufficient level for the vital functions of plants, irrespective of the tested soil tillage models, while the maximum humidification of the soil profile (0-100 cm) was provided by the differentiated tillage in crop rotation. In particular, a positive aftereffect (restoration of favourable agrophysical condition of the soil) was produced by deep chiselling before sowing grain maize -179 mm, which was by 23-44 mm or 17-32% greater than in the case of long-term subsurface blade or disk tillage.
In the course of the barley grain formation, the whole root habitable soil layer was to a significant extent drying out as a result of the undesirable combination of the biotic and natural factors: the intensive water consumption by the plants and the deficit in atmospheric precipitation in May-June (25-41% of the normal amount). The great residual water stock both in the 0-40 cm (60-73 mm) and in the 0-100 cm (90-108 mm) layers Note: against background of using by-products in crop rotation at mean amount of 6.5-7.0 t•ha -1 + N 70 P 58 K 68 .
can be explained by the strong July rains (2017-2018) as well as the insignificant water consumption by the plants at the end of their growth, when the water was well preserved under the cover of the plant mulch produced by the ripening haulm stand of the crop.
In the case of the adaptive soil tillage system, the conditional mean accretion of water stock in the 1 m soil layer in the course of the growth period (143 mm) was greater by 3-9 mm or 9-28%, than in any of the alternative cases. The water accumulation potential of deep chiselling (43-45 cm) was obviously fulfilled in the grain maize field, where the weighted mean available water stock in the 0-100 cm layer was equal to 189 mm, which was greater by 13-34% (12-48 mm) than the respective figures of the plough, subsurface blade and disk tillage of the soil.
The excessive dehumification of agronomic soils indicates that the mineralisation processes aimed at developing the productivity of agrocenoses prevail over the compensation of the organic matter loss by means of adequately returning the unmarketable part of the harvest into the soil. Although the supply of organic carbon rises in this case by a factor of 1.5-3.0 relative to the classic organic fertilizers, until now, no valid replacement for the latter has been found [FAO. 2014].
It has been proven by special pilot studies that the localised embedding of litter manure, crop husbandry by-products, mineral fertilisers and chemical amendments into the zone of relatively stable hydrothermal conditions (8-13 cm layer) or at least into the upper half (0-15 cm) of the arable layer is a suboptimal model for their use.
In effect, the described approach implies some kind of composting the soil-and-fertiliser mixture with an aim of adjusting the processes of the destruction-synthesis-release-assimilation of fertiliser elements contained in different-quality organic and mineral components.
At the end of the four-field crop rotation period, the distinct non-uniformity of the soil profile with regard to the humus content was recorded (Fig. 3). At the same time, the total stock of humus (0-40 cm) in the case of mouldboard (reference) and combined soil tillage systems turned out to be identical for practical purposes (64.6-66.0 t•ha -1 ), while the non-mouldboard tillage resulted in the decrease of the figure by 6.0-6.9%.
The conclusion is that the rational agronomic technology solutions provide for the non-deficit, but only simple reproduction of С org in grey forest soils, taking into account the genetic limitations for its accumulation and the equality of the microbiologic transformation processes that both the organic matter in the soil and the plant biomass undergo. There is an alarming fact of the significant deterioration observed in the humification that takes place in the 20-40 cm soil layer against the background of alternative non-mouldboard tillage systems (-10.3-16.4%).
It has been proven that the use of by-products has a positive effect not only on the physical properties of the soil, but also improves the nutrient conditions in it to a considerable extent. The average return into the soil with aftermath residues per annum per ha of land in crop rotation: 103-116 kg of nitrogen, 31-37 kg of Р 2 О 5 and 81-96 kg of К 2 О. The maximum enrichment of the soil with nutrients was observed in the case of the mouldboard and adaptive tillage systems -238-249 kg•ha -1 of NPK. In the case of subsurface blade tillage of the soil their amount decreased by 4.7-8.9%, after long-term shallow and surface disk tillage -by 7.6-11.7% and 10.6-14.0%, respectively.
The annual debit of nitrogen in crop rotation due to the entered by-products amounted to 432 kg•ha -1 , phosphorus -136 and potassium -356 kg•ha -1 . The following input of each crop in the recirculation of the soil nutrient pool seems to have been present, in ascending order: soybean 5.6-16.0%, spring barley -21.4-24.4%, winter wheat -15.2-21.1% and grain maize -40.6-54.8% (Fig. 4).
Once again, it should be noted that the soil profile features abnormal (excessive) layer-bylayer differentiation with regard to the contents of nitrogen, available phosphorus and exchange potassium against monotype (long-term) disk tillage backgrounds with disking to depths of 6 to 12 cm. On the face of it, it is good that the fertility of the 0-15 cm surface layer theoretically increases. However, the 20-40 cm layer, quite the reverse, is continuously becoming poorer and the regression from this phenomenon is noticeable, because the artificial contraction of the humusaccumulated horizon brings about the depression in the development of root systems, the dependence of the soil and plants on the instantaneous weather conditions increases, which results in the decline of the potential and effective soil fertility and the overall productivity of the experimental agrocenoses.
The calculated balance of mineral elements in the four-field grain crop rotation cycle (Table 4) indicate the equally slightly deficient provision of plants with nitrogen (-14 kg•ha -1 ) in the case of both the traditional and adaptive tillage systems and a trend of its deterioration (-16-21 kg•ha -1 ) after using non-mouldboard tillage systems, first of all, surface and shallow loosening with the use of disk implements. The intensity of balance of the key organogenic element (N) is equal to 88 and 81-86%, respectively.
The surficial concentration of mineral fertilisers, grain cenosis by-products and soil microbiota in the case of the absent soil layer overturning allegedly brings about favourable conditions for the phosphorus and potassium contents in the soil and plants, as proven by the data on their balance intensity (181-187% Р 2 О 5 and 138-143% К 2 О). These figures exceed the ones observed in the case of the conventional mouldboard and advanced combined soil tillage systems by 26-32 and 14-19%, respectively. In reality, the mobile compounds of phosphorus and potassium are apparently assimilated to a lesser extent in the first case because of the more strained hydrothermal conditions in the root habitable layer, while in the second case the above-mentioned major nutrient elements are taken up more intensively for the build-up of vigorous biomass, resulting in higher grain productivity of the crops under investigation. The long-term application of non-mouldboard, in particular, surface and shallow primary soil tillage techniques strains to a considerable extent the herbological situation, first of all in the plantings of crops with low weed resistance -maize and soybean. In the experiment, the actual amount of grass species was as follows: barn grass varied across the range of models within the range of 8-120 pcs•m -2 , yellow-foxtail grass 4-42 pcs•m -2 ; separate beds of couch grass -1-4 pcs•m -2 . The occurrence of dicotyledonous weeds (wild radish, lamb's quarters, galinsoga parviflora, black nightshade, red-root amaranth) did not exceed 5-24 pcs•m -2 . In both the agrocenoses, a few-year, mostly grass-type weediness developed. The share of the grass synusia decreased from 93% (without fertilisers) to 65% (organic and mineral fertiliser system) with the adequate replacement (from 7 to 35%) by the annual dicotyledonous component. The first waves of weed seedlings were eradicated by means of cultivation before sowing the crop, in the postemergence period -by chemical weeding with the use of herbicides admitted for application and corresponding to the structure of eradicate weeds. Their technical effectiveness reached 90-95%.
The research results have proven that, in the case the productive atmospheric precipitation occurs in the second half of the growth period, the quantity of weeds growing in the plantings of the above-mentioned crops against inalterably non-mouldboard tilled backgrounds is greater by 6-88%, than in the case of either the conventional mouldboard or combined soil tillage in crop rotation. The harmful effect of weeds in the reproductive organ formation period is proven by the averaged data on the accumulation of weed dry weight in the pre-harvesting period (Fig. 5). In turn, the minimum level of it (216 g•m -2 ) was reached after differentiated tillage, after subsurface blade tillage it rose to 260 g•m -2 (+20.4%), the rise was especially strong against the background of surface and shallow disk tillage -to 299-378 g•m -2 or by 38.4-75.0%. It is indicative that, due to the powerful plant habit of maize and soybean against the organic and mineral fertiliser background and the weed shading effect, the weed load on the average for the soil tillage systems was equal to 183 g•m -2 , which was 1.4-2.0 times lower, than in the case of fertilising solely with the by-products of the predecessor or controlling (without fertilisation), respectively.
No distinct alternative-specific preference for the development and propagation of fungal diseases (blister smut, rust, Septoria blight, Cercospora blight) and insect pests (sod webworm, corn-worm, wheat thrips, red spider) has been found in the experimental grain and bean agrocenoses. Moreover, the spread and intensity of the attack on the crops by hazardous organisms did not exceed the standard economic harmfulness limits, that is, no additional measures were needed for controlling them.
The yield capacity of the crops under investigation as the defining economic effectiveness Note: against background of by-products used in crop rotation at mean amount of 6.5-7.0 t•ha -1 + N 70 P 58 K 68 .
criterion increased in proportion to the intensity of the agronomic background: natural fertility > fertilisation with by-products at 6.5-7.0 t•ha -1 > the same + N 70 P 58 K 68 in all soil tillage systems ( Table 5). The statistical analysis of the crop yield indices has proven that each of them had certain variation range and coefficient of variation. The yield of winter wheat had a medium coefficient of variation (V = 16.4%). The other crops featured significant variability, as indicated by the respective coefficients of variation (V = 24.7-34.2%).
In particular, the highest mean yield of winter wheat (5.0 t•ha -1 ) was achieved with the use of the agronomic technology model based on shallow disk tillage (10-12 cm) within the framework of the system of adaptive tillage and organic and mineral fertilisation in crop rotation. The statistically equal grain productivity of the crop was provided by the mouldboard tillage system. In its turn, ploughing, first of all, against a balanced agronomic background, was significantly superior to the every-year shallow disk tillage (10%), variable-depth subsurface blade tillage (12.3%) and, especially, surface disk tillage (by 21.5% or 0.87 t•ha -1 ).
Comparing to the reference case without fertilisation, fertilisation with by-products increases the crop yield capacity after ploughing by 30%, after surface and shallow disk tillage by 23.4-25.6% and after subsurface blade tillage -by 18%. Due to the additional application of N 80 P 60 K 80 , the total increase in the winter wheat yield rose to 44.4%, 35.9-44.3% and 34.4%, respectively. However, the yield increase due to the additional application of solid mineral fertilisers did not exceed 11.0-13.8%.
Grain maize and soybean are less sensitive to the layer-by-layer differentiation of the soil fertility in view of the rather high grain crop yield, but that is true only subject to meeting the key requirement -to ensure the depth (22-45 cm) of the autumn ploughing that is biologically necessary for them with the use of a usual plough, a subsurface blade cultivator or a chisel deep tiller.
The maximum yield of both the crops (maize 8.89 t•ha -1 and soybean 3.17 t•ha -1 ) on the average for 2016-2020 was obtained in the case of the alternatives with differentiated primary soil tillage (chisel tillage 43-45 cm and ploughing 22-24 cm, respectively) against the background of the organic and mineral fertilisation system and the input of soil-applied and postemergence herbicides. Despite their technological identity, the single-type shallow and especially surface disk loosening resulted in the substantial decline in the yield capacity of both grain maize (11-19%) and soybean -by 16-20%. Special consideration is to be given to the fact that the chemical weed control in the plantings of grain cenoses is highly effective, as it enhances the performance of the other production methods in crop growing, in particular, in the case of maize , 2016-2020. Tillage system: 1 -mouldboard, variable-depth; 2 -subsurface blade, variable-depth; 3 -adaptive, variable-depth; 4 -shallow disk; 5 -surface disk. Fertilisation system: a -no fertilisation; b -by-products; c -by-products + NPK by 26-30%, while in the case of soybean -by a factor of 1.9-2.3. The conclusion is that noherbicide technology of growing the latter is just economically inadvisable.
Spring barley positively responds to the concentration of the physical, agrochemical and biological components of fertility in the upper part of the tilled topsoil. That is the exact cause of the fact that the maximum yield of the crop (4.45 t•ha -1 ) was achieved after carrying out one-time disking to a depth of 10-12 cm with the aftereffect of the deep chisel ripping that had been done for the preceding maize. The only exception was the invariable surface soil tillage in crop rotation, in which case even with the organic and mineral fertilisation system the shortfall in the grain harvest was at a level of almost 24%. Alongside the bundle of problems stipulated by the sharp differentiation in the fertility of the humus horizon, the difficulties have also been noted in the performance of high quality sowing with the use of a standard grain seeder caused by the presence of great amounts of plant residues in the near-surface soil layer.
The effectiveness and complementarity of the agronomic engineering measures applied in the experiment has been proven by the wide range of variation in the actual crop yield (2016-2020): winter wheat 2.80-5.05 t•ha -1 (mean value X̅ 3.96 t•ha -1 ), grain maize 4.1-8.89 t•ha -1 (X̅ 7.22 t•ha -1 ), spring barley 1.78-4.45 t•ha -1 (X̅ 3.44 t•ha -1 ) and soybean 1.02-3.17 t•ha -1 (X̅ 2.0 t•ha -1 ). That is, depending on the resource and engineering support, under the conditions of Right Bank Forest Steppe, credible possibilities exist for the further improvement of productivity of main grain crops.
The average grain crop yield in crop rotation against the agronomic background of no fertilisation is equal to 2.8 t•ha -1 , with the input of 6.5-7.0 t•ha -1 of plant residues from the predecessor -3.6 t•ha -1 (126%) and in case of their application in combination with N 70 P 58 K 68 -4.90 t•ha -1 (171%).
Almost 25% increase in the productivity, when the best model of combined soil tillage (5.38 t•ha -1 ) is compared to the relatively worst one -surface disk tillage (4.31 t•ha -1 ), even when correct organic and mineral nutrition is provided for the plants, convinces that exactly adaptive (dynamic) primary tillage technologies are the ones to be chosen for application. Note: *a -without fertilisers; b -by-products; c -by-products + NPK. Mean input over crop rotation cycle: byproducts 6.5-7.0 t•ha -1 + N 70 P 58 K 68 .
The productivity of the crop rotation system under investigation correlates with the dynamics of the yield capacities of individual crops in the tested alternatives, but with 10-15% surplus above the estimate rated parameters: when using the natural fertility (without fertilisers) -2.96 t•ha -1 of grain units; against the background of biologic fertilisers (use of by-products) -3.76 t•ha -1 of grain units (+27.1%); against the organic and mineral fertilisation background on the average for the five alternative soil tillage systems -5.21 t•ha -1 of grain units (+76.1%).
Thus, the consolidation of natural and anthropogenic factors activated by mechanical soil cultivation facilitates (in accordance with the agronomic background) improving the initial biologic potential of a hectare of plough land by a factor of 1.3-1.8.
The minimum productivity of the crop rotation cycle within the range of fertilisation backgrounds (2.56-4.60 t•ha -1 of grain units) has been recorded for the most simplified continuous disk tillage to a depth of 6-8 cm, the maximum one (3.28-5.72 t•ha -1 of grain units) -in the case of clear differentiation of both the techniques and depths of soil tillage in accordance with the distinctive agrobiological features of each crop: disk tillage (10-12 cm) for winter wheat; strip chisel tillage (43-45 cm) for grain maize; disk tillage (10-12 cm) for spring barley and mouldboard ploughing (20-24 cm) for soybean, subject to indispensable rationalisation of the fertilisation system and protection of plantings against hazardous organisms.
The mean productivity of the crop rotation cycle in the case of such primary tillage differentiation is equal to 4.37 t•ha -1 of grain units, which exceeds the level of the conventional variable-depth ploughing by 4.0%. At the same time, the long-term variable-step minimisation -application of the variable-depth subsurface blade, shallow and especially surface disk tillage systems -results in a substantial decrease (by 0.54-1.12 t•ha -1 of grain units or 10.4-24.3%) in the productivity of the crop rotation cycle. The priority in the updated model of adaptive soil tillage is given to the multiple-vector remediation of old arable edaphotopes and the agrobiological production processes towards self-reproduction (homoeostasis), ecophilia, efficiency, resource and energy conservation in agronomic technologies. That is supported by the results of the earlier research performed by other authors in 2012-2018 (Kravchuk et al., 2019).
The expert appraisal of the economic efficiency achieved with the use of the experimental agronomic technologies mostly coincides with the theoretic indices obtained for the yield capacities of individual crops and the productivity of the overall crop rotation cycle in the tested alternatives. The scope of this paper is limited to the thesis accents on the performance of the alternative tillage and fertilisation systems in monetary terms.
The analysis of data on the economic efficiency has revealed ( Table 6) that the mean grain production cost for the four crops in crop rotation (117 €•t -1 ) is kind of the median value for the anthropogenic load and the actual biological productivity present in the discussed agronomic technology alternatives.
On the basis of the above, the minimum estimated cost value (107 €•t -1 ) is typical for the purely organic fertilisation system due to the combination of high productivity and moderate process costs. In contrast, the technologies with no fertilisation or combining organic and mineral components, on account of upsetting that balance, cause the corresponding increase in the grain cost value -by 17 and 14 €•t -1 or by 15.8 and 13.1%, respectively.
It has been established that in the total financial expenses connected with the implementation of the tested agronomic technologies the fertilisers account for 41%, pesticides -26%, machinery and fuels and lubricants -14%, seeds -11%, electric power and manual labour -8%.
The level of profitability of grain farming in the case of fertilisation with by-products amounts to 158%, while in the absence of fertilisers (low productivity) and against the organic and mineral background (excessive costs) its reduction by 20-25% at a mean crop rotation cycle parameter of 134% has been proven.
Due to the optimisation of the agrochemical components, the differentiated tillage system delivered the maximum (154%) technical and economic payback in the researched crop rotation system. On average, this value is greater by 11%, than in the case of the reference alternative (mouldboard ploughing) and by 17-49% -in comparison to continuous non-mouldboard tillage techniques.
Accordingly, it is obvious that the economic feasibility of growing grain in the edaphic and ecologic conditions of the Right Bank Forest Steppe region with regard to the discussed crops is as follows, in descending order: grain maize (163%) < winter wheat (146%) < soybean (132%) < barley (97%).
In the completed research, comprehensive original scientific factual data have been obtained on the transformation of the physical, agrochemical and biological condition and the effective and potential fertility of grey forest light loam soil within a crop rotation cycle (2016-2020). The research included an experiment with the following design: in the four-year grain crop rotation cycle, five alternative soil tillage systems with different techniques and tillage depths were applied against three alternative agrochemical backgrounds, which included the use of crop husbandry by-products as a fertiliser and moderate amounts of mineral fertilisers N 70 P 58 K 68 .
The differentiation in the topsoil has been revealed with regard to its fertility criteria (distribution of after-harvest crop residues, bulk density, hardness, microbiological activity, humus content and reserve, potential weed infestation, availability of assimilable forms of NPK and balance of major nutrient elements) in the case of continuous non-mouldboard tillage, especially superficial and shallow disking.
The initial hypothesis that the priority is to be given to the evolutionary implementation of agricultural technological innovations has been confirmed. The evolutionary approach has to be based on the rational combination (depending on the crop rotation design and the cultivated crops) of adaptive tillage (with a variable depth of 10-45 cm), traditional ploughing, subsurface blade tillage, strip chisel primary tillage and disking, in conjunction with the optimal organic and mineral fertilisation system, an essential component of which is the utilisation of by-products after their composting and controlled biological destruction. Note: *a -no fertilisation; b -by-products; c -by-products at 6.5-7.0 t•ha -1 + N 70 P 58 K 68 .
The agronomical technology optimisation ensures, depending on the agrochemical load, a 1.3-1.8 times increase in the mean productivity of the experimental crop rotation from 2.96 to 5.21 t•ha -1 of grain units with a variation range of 5.72-4.60 t•ha -1 of grain units after adaptive tillage (to depths 10-45 cm) and every-year superficial disking (6-8 cm), respectively, against balanced organic and mineral fertilisation backgrounds.
The results of the comprehensive research give evidence of the environmental, agrobiological and socioeconomic efficiency of applying adaptive (flexible) resource-saving soil tillage and fertilisation technologies in regional crop rotation systems, subject to the adequate technical, informational and navigational support throughout the complete crop production cycle.
Among the relevant publications on the discussed topic, the following are to be pointed out: Medvedev (2013) and Marandola et al. (2019).
In the studies by the scientists of the National Scientific Centre "O.N. Sokolovsky Institute of Soil Science and Agrochemistry Research under the National Academy of Agrarian Sciences of Ukraine" (Medvedev, 2013 and2015), significant attention has been paid to the physical and physical-and-technological criteria of the advisable minimization in the tillage of soils of different origin (mostly chernozem soils). At the same time, they do not contain any data on the effectiveness (practical validation of the theoretical imperatives in the soil tillage rationalisation methods). Moreover, the extent of the possible introduction of the no-till technology is clearly overestimated. That said, the scientists of this scientific institution advocate the application of exclusively adaptive (combined) soil tillage systems (technologies) with due account for the whole set of edaphicecologic and socioeconomic conditions. Such an approach is in line with the main provisions of this paper.
Despite the certain informational boom around the innovative no-till technology, the Italian scientists have also expressed only reserved optimism with regard to the trend towards nonmouldboard tillage as an agrotechnological panacea. That is supported by the official statistics: as of April 2019, the no-till technology was applied throughout the world in an area of 156 mln•ha. That means just 11% of the world's cultivated land after half a century of the implementation of the supposedly revolutionary scientific concept.
A distinctive feature of this study is the long-term stationary experimental research that evolves in accordance with the socioeconomic needs of society and the concurrent situation.
The further theoretical and practical development of arable farming will most likely take place in the form of the efficient utilisation of the existing resources and facilities in the existing agricultural businesses, the gradual re-equipment of the agricultural industry with up-to-date machinery and the further rational implementation of the controlled transformation (biodestruction) technologies in order to make use of the crop husbandry by-products as a most important (in fact, the dominant) form of organic fertilisers with an aim of raising the soil fertility and utilising in full the biological potentials of agrocenoses.

CONCLUSIONS
1. The progress and direction of the mobilisation and regeneration edaphic and production processes in grain agrocenoses under stochastic unfavourable changes of the climate are determined by the specific interaction of the following factors: tillage-fertilisation-crop. 2. The near-surface concentration of mineral fertilisers, crop husbandry by-products, microbiota and weed seeds (in excess of 65%) in the case of long-term subsurface blade tillage and, especially, surface and shallow disk tillage in crop rotation results in the excessive layerby-layer differentiation of the grey forest light loam soil with regard to its fertility ("enriched" 0-15 cm, "emaciated" 18-40 cm soil layers). 3. The adaptive (combined) and purely mouldboard soil tillage systems against a balanced organic and mineral fertilisation background are superior to the non-mouldboard alternatives as regards the total stock of humus and the intensity of balance of mineral nitrogen (88% and 81-86%, respectively). However, in the absence of mouldboard ploughing, the phosphorous and potassium conditions in the soil improve (up to 26 kg•ha -1 and up to 12 kg•ha -1 , respectively) with the corresponding improvement of the intensity of their balance (by 29% and 17%, respectively).
4. Uniform disk tillage, in view of its higher "provocative" capacity, strains the herbological situation, in particular, in the plantings of grain maize and soybean. Comparing to every-year ploughing and combined soil tillage, the number of weeds in the case of shallow and surface disk tillage is increased even in the pre-harvesting period by 6-88%, their mass -by 12-91%. 5. During the rotation cycle (2016-2020), the biological potential of the four-field grain crop rotation on the average for the five alternative soil tillage systems increases in proportion to the agrochemical load by a factor of 1.3-1.8: natural fertility -2.96 t•ha -1 of grain units; fertilisation with by-products at 6.5-7.0 t•ha -1 -3.76 t•ha -1 of grain units; the same + N 70 P 58 K 68 -5.21 t•ha -1 of grain units. 6. The minimum productivity of the experimental crop rotation cycle (2.56-4.60 t•ha -1 of grain units, depending on the agronomic background) has been recorded in the case of continuous surface disk tillage (6-8 cm), its maximum level (3.28-5.72 t•ha -1 of grain units) -in the case of the adaptive soil tillage system: disk tillage (10-12 cm) for winter wheat; strip chisel tillage (43-45 cm) for grain maize; disk tillage (10-12 cm) for spring barley; ploughing (22-24 cm) for soybean. 7. The mean grain production cost in advanced agronomic technologies based on adaptive primary soil tillage techniques and organic and mineral fertilisation systems applied to the crops in rotation is equal to 113 €•t -1 , earning capacity -761 €•ha -1 per annum, level of profitability -139%, while in the case of the other tested alternatives, these indices are lower by 3-21 €•t -1 , 45-110 €•ha -1 per annum and 9-23%, respectively. The economic feasibility (payback) of growing grain crops in the edaphic and ecologic conditions of the Right Bank Forest Steppe region is as follows, in descending order: grain maize (163%) < winter wheat (146%) < soybean (132%) < barley (97%). 8. The results of the completed comprehensive research give evidence of the environmental, agrobiological and socioeconomic efficiency of using exclusively adaptive (flexible) resource saving soil tillage technologies in the crop rotation systems of the Forest Steppe region with the state-of-the-art technical and technological, information and navigation support throughout the whole crop husbandry production cycle.