Reproduction of soil fertility in adaptive landscape farming systems of the foothill zone of the RNO-Alania

. Modern intensification of agriculture has significantly speeded up the processes of land destruction and loss of its fertility. This has led to the deterioration in the agroecological situation, boost in the potential fertility of land, and a significant decrease in yields and quality of agricultural products. The purpose of our research was the rational use of land, while compacting the link of the grain crop rotation. The studies were carried out in the foothill zone of the Republic of North Ossetia – Alania, on leached chernozems, in the subzone of sufficient moisture. In the experiments, oats were sown in pure form, mixed with peas, as well as a variant of a pea-oat-sunflower mixture, with harvesting terms for green fodder, grain haylage and grain. Today pea-oat-sunflower mixture, unlike corn for silage, is a resource-saving, low-cost and multicomponent mixture. After harvesting these crops, the crop rotation is compacted by buckwheat crops for grain. With such a sparing use of land resources, the high self-cleaning ability of these mixtures and buckwheat reduces the cost and increases the productivity of arable land. An increase in soil fertility is achieved by introducing green manure crops (winter and spring rapeseed, oilseed radish, white mustard, winter rye, etc.), which, when plowing, improve the soil structure (structural coefficient up to 3), boost the humus content in the soil by 0.02 – 0.05%, neutralize the acidity of the soil environment (up to pH = 5.5 – 6,7), clean the soil from excess nitrates, heavy metals, pesticide residues, etc., and enhance the yield by 15-20%.


Introduction
Adaptive landscape farming systems are used to increase soil fertility and crop productivity.Crop rotations remain a key link in modern farming systems and solve a set of tasks for the rational use of land, reproduction of soil fertility, its protection from erosion and harmful organisms.[1][2]4] The problem is particularly acute in peasant (private) farms, where rotation is disrupted due to low land, agricultural crops are repeatedly sown on the same plot, resulting in not only a decrease in the nutrient content, but also sharply deteriorate the water-physical properties of the soil, pathogens accumulate that affect productivity and product quality [5][6].
In the RNO -Alania, there is a high saturation of row crops in crop rotations, which leads to high mineralization of organic matter, over-compaction of the soil and a decrease in its fertility.
Currently, due to the acute shortage of material and technical means, the complexity of farming, significant environmental pollution, fruit-bearing crop rotations with an adaptive resource-saving tillage system, the use of fertilizers and plant protection products using intensive biological factors that improve the phytosanitary condition of fields should replace specialized crop rotations [7][8].
The main task of biological farming is to obtain high-quality, environmentally friendly products with simultaneous increase in soil fertility [9][10].
This task can be solved by introducing crop rotations with legumes, the use of biologics and siderites, increasing organic and decreasing mineral fertilizers rates, with wider use of a combined tillage system and the transition to biological methods of protection.Only a complex combination of agrotechnical practices can ensure the receipt of high specified yields of good quality

Materials and methods
The research was carried out in the foothill zone of the RNO-Alania, guided by the methodological manual "Agroecological assessment of lands.Design of adaptive landscape systems of agriculture and agrotechnologies" (Moscow: RASKHN, 2005, ed.members of the academy of Sciences RASKHN V.I.Kiryushina and A.L. Ivanova) [3].

Analysis and discussion of the results
The conditions for increasing soil fertility and increasing crop yields are the use of organic and mineral fertilizers.
Currently, there is no possibility of using organic fertilizers in the republic due to a significant reduction in the number of livestock and a decrease in manure yield, as well as due to a lack of technical and financial resources to carry out work on harvesting, storage and application of organic fertilizers to the soil.Research on the study of two types of 8field crop rotations (grassland and grain-tillage), comparison of efficiency, compaction of their intermediate crops, as well as resource-saving and soil-protective technologies of cultivation of individual crops as elements of adaptive landscape farming were carried out in the SKNIIGPSKH VNTS RAN in the foothill zone on chernozems.
Grassland According to the research results, it was revealed that in terms of productivity and product quality in the studied crop rotations, the grass-field crop rotation had an advantage, where the yields of the main field crops were higher than in the grain crop rotation.So, on average, during the rotation, the grain yield of winter wheat in the grass-field crop rotation was higher by 2.5-3.8dt/ha, corn -3.7-5.6 dt/ha and potatoes by 18.0-26.0dt/ha.
In the studied crop rotations, the influence of predecessors on the yield of corn grain was tracedaccording to the layer of perennial grasses, it was 63-65 dt/ha, and the turnover of the formation was 5.9-6.5 dt/ha lower.In the grain-tillage crop rotation, a higher yield of winter wheat grain 46.5-50.8dt/ha was provided by winter and spring cabbage crops for grain + postharvest buckwheat, and corn grains according to the predecessor winter wheat -58.4 dt/ha.
Studies have established that it is economically advantageous to cultivate agricultural crops in the studied crop rotations.The profit from growing with 2-3 mowing use of perennial grasses reaches 10.1-13.8thousand rubles/ha, corn grains by 11.7-15.2thousand rubles/ha, winter wheat 13.0-15.5thousand rubles/ha, and potatoes 30-38 thousand rubles/ha.
The energy efficiency of crop rotations is quite high.The best indicators of exchange energy are provided by the grass-field crop rotation due to higher yields of grain, potatoes and perennial grasses, where the energy efficiency indicators were 5.4-9.5, and in grain cultivation -4.6-8.5 GJ per 1 hectare.
In postharvest crop sowing, after early harvested grain crops, it was studied the following: the cultivation of buckwheat, millet, etc., which provided a grain yield of 9.5-18 dt/ha, as well as 3-component mixtures of corn, sunflower and peas with a yield of green mass of 210-250 dt/ha.
Intermediate crops of winter rapeseed and winter ginger, characterized by high cold resistance and starting to grow 2-3 weeks earlier in spring than winter bean-cereal mixtures, on a fertilized (N 90 P 90 K 60) agrophone form a harvest of green mass 360-420 dt/ha, freeing up fields for sowing corn, sunflower, soybeans, beans for grain.
In the structure of the sown areas of the foothills, harvested grains, legumes and cereals occupy more than 50% of the arable land area.In the liberated fields in the post-harvest period, for 100-125 days, mechanical tillage leads to degradation processes, increased cost, and with limited tillage, the fields become overgrown with weeds.
In order to minimize tillage in the summer-autumn period, reduce costs, prevent soil from destruction, clogging of crops, we studied temporary phytoconservation of soils by combined sowing of winter wheat with perennial grasses.At the optimal time, winter wheat was sown in one operation with a seeding rate 10-15% lower and the full rate of perennial grasses (cocksfoot, meadow oats, multi-corn ryegrass or a mixture of cocksfoot with ryegrass).
In the autumn, winter wheat and cereal grasses provide friendly shoots and development, and in the spring the plants intensively start to grow.
After harvesting winter wheat with a grain yield of 35-42 dt/ha, cereal grasses grow and by the end of the growing season provide a harvest of 145-214 dt/ha of green mass.
The biomass of grasses with a root system plowed in autumn enriches the soil with organic matter and nutrients, which later in the second year provides an increase in the yield of corn grain by 8-14 dt per hectare.In order to replenish organic matter in the soil in crop rotations on leached black soils without special labor-intensive costs and to obtain a high yield of potato tubers, we studied the influence of biological meliorants (siderates, straw, slurry) and local zeolite-containing agrorudes (irlites) on the agrophysical, agrochemical and biological properties of the soil, contributing to the increase of soil fertility and the yield of potato tubers of 200 dt/ha or more.
One of the ways of sustainable farming is to improve the structure of acreage by compacting crop rotation fields, as well as the use of various environmentally friendly means to increase the yield, improve its quality and preserve soil fertility.
In order to biologize the intensification of precursors for winter wheat and potatoes in the crop rotation link, early spring fodder cropswinter wheatpotatoes in the first field it is effective to cultivate multicomponent mixtures of oats with peas or vetch and sunflower, at different ratios used for green fodder, silage, grain planting, which increase the yield by 25-35%.They leave a large amount of postharvest-root residues enriched with nitrogen, phosphorus and potassium in the soil, increasing soil fertility and weakening erosion processes.
In the second field of the crop rotation link (winter wheat), after multicomponent mixtures, a long post-harvest period allows for semi-steam tillage of the soil before sowing winter wheat and cleaning its surface layer from viable weed seeds, having a positive effect on the yield and grain quality.
The harvest of winter wheat grain sown on the above crops in an average of two years of research yielded the following results: in the variant of pure oats with different harvesting periods ranged from 33.35 dt/ha to 38.20 dt/ha, and in the variants of pea-oat and pea-oat sunflower mixture, the yield indicators were higher -38.9-44.9dt/ha.
The indicators of volumetric weight, air capacity, humidity and borehole were also different and were higher on crops of pea-oat and pea-oat-sunflower mixtures.
The nitrogen content under winter wheat in the pure oats variant varied depending on the harvesting time of 7.36-9.9mg/kg, and in the variants mixed with peas it was higher and amounted to 20.6-21.4mg/kg.Phosphorus under pure oat crops was from 155.36 to 156.46 mg/kg of soil, on variants of pea-oat mixture from 155.7-264.5 mg/kg of soil, and under pea-oat-sunflower mixture 161-272 mg/kg of soil.
The quality of winter wheat grain was assessed by the content of raw protein, gluten, weight of 1000 grains, nature, vitreousness, all of them were higher than the predecessors of oats mixed with peas and lower on pure oat crops.
Pea-oat mixtures and postharvest sideral crops included in the link of the grain crop rotation, make it possible, through the biological accumulation of nitrogen and essential nutrients, to increase the content of organic matter in the soil, increase and improve the quality of winter wheat grain.
Cultivation of multicomponent mixtures of early spring crops, as precursors of winter wheat, is economically justified and provides an increase in yield by 10-12%, improving the quality of grain corresponding to strong wheat.
In the third field of the crop rotation link (potatoes), after harvesting winter wheat, multicomponent mixtures of postharvest sideral crops should be cultivatedspring rapeseed + white mustard; white mustard + oilseed radish; white mustard + oilseed radish + winter rye.From legumes, include vetch or peas in the mixture.With their powerfully developed aboveground mass and root system, they oppress and suppress weed-field vegetation, when plowing them, loosen the surface layer of the soil, improve its biological activity, enrich it with organic matterhumus, activate the accumulation of available forms of nutrients, which has a positive effect on the crop and its quality.The increase in soil fertility is achieved by introducing sideral crops (winter and spring rapeseed, oilseed radish, white mustard, winter rye, etc.), which, when plowing, improve the soil structure (structural E3S Web of Conferences 463, 01011 (2023) EESTE2023 https://doi.org/10.1051/e3sconf/202346301011coefficient up to 3), increase the humus content in the soil by 0.02 -0.05%, neutralize the acidity of the soil environment (up to pH = 5.5 -6,7), clean the soil from excess nitrates, heavy metals, radionucleides, pesticide residues, etc., increase the yield by 15-20%.
Compared with semi-steam tillage of the soil for potatoes (145 dt/ha), the increase in the yield of potato tubers when plowing sideral crops ranges from 11.5 to 45.9 kg/ha with simultaneous improvement in the quality of tubers in terms of starch, protein, vitamin C. It has been studied that it is advisable for agricultural enterprises of various forms of ownership to grow potatoes in crop rotations and with permanent plantings with using biological meliorantspostharvest sideral crops, straw and zeolite-containing agricultural ores (Irlit -1, Irlit -7), which in combination with organo-mineral fertilizers provide an increase in the yield of tubers from 22.7 to 61.1 dt/ha with high quality indicators and a simultaneous increase in soil fertility.
By changing the structure of crops in the crop rotation, introducing intermediate crops into it for green fertilizer, it is possible to purposefully manage biological factors of soil fertility, to ensure an increase in crop yields and crop rotation productivity without disturbing the ecological balance.
The combined use of plastic cruciferous plants is highly effective: spring rapeseed, white mustard, oilseed radish and winter rye, as crops of intermediate sideral crops, in the compacted link of the grain crop rotation.
Saturation of crop rotation with intermediate crops contributed to the rational use of moisture, improvement of plant nutrition, reduction of contamination of the main croppotatoes, increase in total soil productivity, humus content, as well as increase in yield and quality of potato tubers.
The yield of potato tubers by siderates on average for two years of research ranged from 146.9 dt/ha to 200.6 dt/ha, and the increase in the variants with siderate from 10.7 dt/ha to 53.7 dt/ha.The humus content in the control variant (semi-steam tillage) was 5.38%, white mustard -5.41%.The mustard + radish + winter rye variant showed the highest result of 5.46%, which is associated with the productivity of sideral crops.
The total yield of the soil under control (semi-steam tillage) was 59%, and in the variants with the smell of biomass of sideral crops, spring rapeseed -63%, white mustard -71%, oilseed radish -72%, especially in the 0-20 cm layer.
The yield of the green mass of postharvest crops in the years of research depended mainly on the meteorological conditions of the postharvest period and the timing of sowing and averaged 256.3-366.0c/ha over the three years of research.

Conclusion
Biologization is a new stage in the development of agriculture and in agro-technological resource conservation.The implementation of the planned techniques and various measures will make it possible to improve soil fertility and increase the productivity of cultivated crops in the future, reliably preserve the ecology of the environment, improve human living conditions.
Compaction of the crop rotation link with multicomponent mixtures of oats, postharvest buckwheat and postharvest sideral crops can increase soil fertility, improve its physicochemical properties, phytosanitary condition and productivity.And all this in a complex is environmentally friendly, harmless agricultural products and uncontaminated environment.