State and ways to increase soil fertility of the south-steppe zone of Ukraine

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Institute of Irrigated Agriculture of NAAS

State and ways to increase soil fertility of the south-steppe zone of Ukraine

Goal. To scientifically substantiate the modern landscape-ecological state of agricultural lands and the development of agrobiological measures to increase the fertility of degraded dark chestnut soils of the Steppe zone of Ukraine in conditions of natural moisture. Methods. Field -- to study the interaction of the research object with biotic and abiotic factors of the Steppe zone; physicochemical -- to establish the fertility of dark chestnut soil and to determine the chemical composition of plants; comparable calculation -- to conduct the economic and energy evaluation of growing legumes of long-term grasses; dispersion analysis -- to determine the reliability of the results of scientific research. Results. The area of perennial grasses in the Steppe zone over the past 10 years had significantly decreased. That created real risks to enhance the processes of water and wind erosions of soils. Significant influence on the efficiency of agricultural production in the Steppe zone also had regional climate change. In studies on the selection of perennial legumes and cereals as well as legume-cereal grass mixtures, accumulation of symbiotic nitrogen by Lucerne in the first year of the use of mono-species crops was 60 kg/ha, by mixture Lucerne + Bromus inermis -- 68, and by Sainfoin -- 105 - 118 kg/ha. In the 2nd year of the use of herbs, the accumulation of symbiotic nitrogen was also high -- 37 - 55 kg/ha in Lucerne, and 52 - 80 kg/ha in Sainfoin. In the 3rd year of the use of grasses its accumulation decreased to 36 - 37 kg/ha in Lucerne, and to 15 - 22 kg/ha -- in Sainfoin. The fractional composition of nitrogen in the 0 - 20 cm and 20 - 40 cm layers of dark chestnut soil after the 3-year use of Lucerne in comparison to other levels of crop rotation was the highest and depending on the soil layer made: of the total -- 1006.3 - 1428.8 mg/kg, of mineral -- 24,9 - 46,3, of alkaline hydrolyzed -- 113,8 - 186,0, of heavy-hydrolyzed -- 155,5 - 214,4, non 712,1 - 982,1 mg/kg of soil. Conclusions. One of the main areas of decrease in the processes of degradation and preservation and increase of soil fertility is the creation of highperformance mono-species agro phytocoenoses of perennial legumes and binary legume-cereal grass mixtures, resistant to regional climate change in the steppe zone of Ukraine.

Key words: degradation, climate, structure of sowing areas, symbiotic nitrogen, Lucerne, Sainfoin, Bromus inermis.

Introduction

The Steppe zone of Ukraine is home to the world's richest chernozem soils, but currently almost all of them are plowed, about 80% of the territory is occupied by agricultural land. As a result, soil fertility is catastrophically deteriorating, and degradation processes are increasing. The total area of only eroded land here is more than 38%, that is, more than 11 million hectares, including 5 million hectares exposed to wind erosion [1].

Due to the lack of scientifically based farming systems and, above all, non-compliance with the optimal structure of acreage, the introduction of insufficient amounts of organic and mineral fertilizers in soils, the content of humus and mineral nutrients is significantly reduced.

Fixing with nodule blocks bacteria nitrogen from the atmosphere, alfalfa on unirrigated lands accumulates up to 120-150 kg/ha symbiotic nitrogen, which is equivalent to 3.5-4.3 c/ha of mineral nitrogen in the form of ammonium nitrate. Therefore, the study of the accumulation of symbiotic nitrogen in the soil during the cultivation of perennial legumes in the Steppe zone is of great importance and makes it possible to correct the structure of sown areas, fertilizer systems and improve existing technologies for growing agricultural crops based on the established patterns of its change [2].

Regional climate changes have also had a huge impact on the formation of crop productivity in recent years [3]. An increase in air temperature and an increase in climate aridity create additional risks for increasing water and wind erosion of soils [4, 5]. In addition, in the South there is a tendency to increase the processes that cause the occurrence of dust storms.

The purpose of the research is scientific substantiation of the modern landscape and ecological system state of agricultural land and development in conditions of natural moisture (without irrigation) agrobiological measures on increasing the fertility of degraded dark-chestnut soils of the southern-steppe zone of Ukraine.

Research methods. Field experiments on the tinning of arable land were conducted in the State Enterprise “Experimental Farm “Kopani” IIA of NAAS in 2010-2019. The soil of the experimental sites is dark-chestnut, residual slightly saline, medium loamy, with the content in the arable layer: humus (according to Tyurin) - 2.02-2.34%, nitrate nitrogen (N-NO3) - 8.0-12.3 mg/kg; mobile phosphorus (according to Machihin) - 24.2- 36.3 and exchange potassium - 330-413 mg/kg of soil. Due to the lack of moisture in dry (95%) years of precipitation availability, the soil cracked to a depth of 0.5-0.7 meters (fig. 1).

Fig. 1. The state of unirrigated dark-chestnut soil of the Southern Steppe subzone in summer during dry years in terms of precipitation availability

At the same time, the yield of cultivated crops in previous crop rotations decreased by 10-20% or more, which are, in particular, signs of soil degradation.

Irrigation of arable land was carried out with cereals and legumes of perennial grasses, the biological features of which are most adapted to the natural and climatic conditions of the Southern Steppe. For short-term (no more than 2-3 years) use of single-species crops of cereals and legumes of perennial grasses, lolium multiflorum (Lolium multiflorum Lam.) Yaroslav variety and sainfoin (Onobrychis arenaria Kit.) Ingulsky variety. During the medium-term reproduction of soil fertility (3-4 years), used festuca orientalis (Festuca orientals (Hack.) V. Krecz.) Domenica variety and variable lucerne (Medicago varia T. Martyn.) Veselka variety.

For long-term reproduction of the fertility of dark-chestnut soil, used variable lucerne (Medicago varia T. Martyn) Veselka variety and bromus inermis (Bromopsis inermis (Leyss.) Holub) Tavriyskyi variety.

Sowing of perennial grasses and legumes in single-species crops and binary grass mixtures was carried out in early spring for three years (2016-2019). The seeding rate for short-term reproduction of the fertility of degraded dark-chestnut arable land, for 100% of its economic suitability, in monofilament crops was: lolium multiflorum - 24 kg/ha, festuca orientalis - 24; sainfoin - 80; as part of grass mixtures, respectively - 12; 12 and 60 kg/ha.

For long - term reproduction of land fertility, the seeding rate of lucerne seeds in single-species crops was 24 kg/ha and bromus inermis - 28 kg/ha. As part of binary grass mixtures, the seeding rate was: lucerne + bromus inermis - 12 + 14 kg/ha. The sown area is 60 m², the accounting area is 20 m². Crop accounting was carried out by the mowing method.

Determination of the amount of fixed nitrogen from the atmosphere by lucerne and sainfoin was carried out by a comparative method with bromus inermis, since when growing it with perennial legumes, all plant species consumed the same amount of nitrogen from the soil. The established difference between nitrogen removal in lucerne, sainfoin, and bromus inermis was equated to nitrogen fixed in legumes.

The dry matter content, the density of herbage, changes in the species botanical composition, the yield of feed units, gross and metabolic energy were determined according to generally accepted methods [6]. Fractional composition of soil nitrogen - according to E. I. Shkonde - I. Ye. Korolyova [7]. Evaporation rate (Eo), lack of moisture supply (AEo) by years of research were determined by N. M. Ivanov [8]. Statistical analysis of the yield of perennial grasses was carried out by the method of variance analysis [9].

Results of research

The structure of land use in developed countries of the world is optimized, since up to 40-50% of the land is occupied by protected landscapes, i.e. meadows and forests. The most striking example of inefficient use of land resources is the existing structure of acreage, which has developed over the past 30 years in the Steppe zone of Ukraine. With a total area of arable land equal to 15528.7 thousand hectares, due to the removal of legumes and perennial grasses from the structure of sown areas, the area of eroded land in recent years has increased to 8362.0 thousand hectares, or 53.8% of the total arable land area [1].

Compared to 1990, the acreage of forage crops, according to the State statistics service of Ukraine, has significantly decreased. If the area of perennial grasses in 1990 was 3986.6 thousand hectares, then in 2020 it did not exceed 869.3 thousand hectares, including in the Steppe zone - only 119.2 thousand hectares [10]. Because of this, over the past 10 years, soils of all types have begun to develop intensively erosion processes. In addition for growing for most agricultural crops, only mineral fertilizers were used, while organic fertilizers were almost never used. The latter is due to a reduction in the number of cattle, as a result of which the production of organic fertilizers decreased to 9.8 million tons and only 0.5 tons were applied per 1 ha of sown area.

According to the structure of the acreage that has developed, it can be noted that the main direction of economic activity of existing enterprises was the cultivation of grain and industrial crops, primarily winter wheat, winter and spring barley, corn, sunflower, soybeans and winter rapeseed, which are in demand on the world market (fig. 2).

References

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