1. Introduction

When cultivating agricultural crops, risks are identified that can affect the development of winter crops during the autumn-winter-spring growing season and the phytosanitary condition of agrocenoses after overwintering. These include dynamic temperature changes from positive to negative in the tillering node zone of cereals; repeated thawing and freezing of the upper soil layer; the formation of an ice crust; lack of snow cover, and, conversely, prolonged snow cover [1], [3], [5], [7].

Additionally, among the limiting risk factors in the region for cultivating winter crops is the water regime of the soils. A deficiency or excess of moisture negatively impacts the development of the plant organism, which directly manifests as a decrease in the generative potential of varieties. In the Kaliningrad region, more than 70% of agricultural landscapes have been converted to arable land thanks to technical solutions for water reclamation — using a closed ceramic drainage system with water discharge into an open channel. Within the drained agro-landscapes of the region, elements of local secondary waterlogging are observed, with signs of gleying [8], [9] appearing in the lower soil horizons of the morphological profile. The formation of waterlogging (rising groundwater levels, formation of surface water) creates an edaphotopic environment in agrocenoses that is detrimental to plant growth, manifesting as necrosis of their tissues, first at the tip of the leaf blade, then at the growth point, stem, and tillering node. The partial or complete death of plants under such conditions depends on the duration of flooding and negative temperatures during the winter period.

The dominant agricultural crops for winter sowing in the Kaliningrad region are rapeseed and wheat. The share of winter wheat in the 2025 sowing amounted to 82%, while barley and rye accounted for 14% and 4%, respectively. The allocation of significant areas for winter wheat is explained by the indispensable value of the product for the country's food security and high seed yield [10], [11], [13], [14]. In 2024, the Kaliningrad region ranked among the top five regions in Russia for wheat yield, taking second place with 59.3 centners per hectare; the total grain harvest of wheat amounted to 436.57 thousand tons (figure) [15], [16].The issue of monitoring agrocenoses of winter crops to assess the overwintering of plants is particularly relevant in the distinctive climatic conditions of the Kaliningrad region [6], [18], which has a humid climate (moisture coefficient — 1.3) [8].

The objective is to monitor the overwintering of winter wheat plants of the Sinava variety on drained sod-podzolic and sod-gley soils in the Kaliningrad region under conditions of possible secondary waterlogging.

2. Research method

Object of Study: Winter wheat (Triticum aestivum L.) of the Sinava variety (hybrid population Lutescens ABCG x Mironovskaya 67) of intensive type; variety Lutescens; reproduction II. The originator of the variety is the Federal State Budgetary Scientific Institution "Federal Scientific Center for Leguminous and Cereal Crops," LLC "ZBK-Center," and JSC "Shchelkovo-Agrohim" [19].

Sowing Dates: September 17, 2021, and September 20, 2024; sowing rate: 210 kg/ha; sowing method: narrow-row; predecessor: winter rapeseed. Spring fertilization of winter wheat with nitrogen fertilizers is carried out in March (March 13, 2022, and March 25, 2025).

The winter wheat crops were located on drained sod-podzolic and sod-gley semi-hydromorphic soils within the Polesskaya Lowland. The entity managing land resources is the Kaliningrad Research Institute of Agriculture — a branch of the Federal State Budgetary Scientific Institution "Federal Scientific Center for Forage Production and Agroecology named after V.R. Williams." This land area has been designated as a cultural forage land of pasture and haymaking type with a regulated grazing system for over 30 years, maintaining its purpose until 2018 [20], [21]. Field and agrometeorological observations and analyses were conducted from October 2021 to March 2025. The density of plant stands was determined using trial plots of 0.25 m² in four repetitions at the end of the autumn vegetation period (quantitative method) and at the beginning of the spring vegetation period (quantitative and weight method) (GOST 20915-75), expressed as an arithmetic mean:

where: a — the number of encountered individuals (stems) of plants;

 S — total accounting area, m².

The condition of the crops was assessed using the following grading scale: excellent condition — at least 400 plants; good — 300–400 plants; satisfactory — 200–300 plants; poor — less than 200 plants; 130 or more plants per square meter — the area is subject to reseeding; less than 130 plants — reseeding is carried out.

3. Results and discussion

The agroclimatic conditions during the autumn-winter-spring period of 2021-2022 and 2024-2025 are objectively assessed as typical for the Kaliningrad region. The winter was mild, influenced by the maritime climate. Air temperatures in winter varied from 6 to -1°C (Figure 3), with high humidity levels of 75–95%. There were three instances of snowfall (the last decade of November, the first decade of January, and the second to third decades of February), with a snow cover lasting from 5 to 11 days and a rapid snowmelt. There was no soil freezing during the winter period of 2021–2022, and there was also no snow cover. In contrast, soil freezing during the winter period of 2024–2025 reached 8–10 cm. The maximum snow cover height was 12 cm (on February 19, 2025); the hydrological load after snowmelt in the experimental field was 12 l/m², which is equivalent to 12 mm.Sharp short-term temperature minima were not recorded in the Kaliningrad region during the winter period of 2021-2022. However, on February 20, 2025, the air temperature dropped to minus 20°C (see Fig. 4), followed by an anomalously sharp increase to 5°C within three hours of the daily temperature cycle. During this period, winter crops were covered by a loose snow layer, which reached a height of 12 cm in the experimental field, protecting the aboveground biomass from freezing.

In the winter periods of 2021–2022 and 2024–2025, there were no prolonged heavy rainfall events, which are characteristic of the region. The highest average precipitation during the studied periods occurred in the second half of November — 37.4–38.6 mm; in the first and third decades of January — 30.5–38 mm; and in mid-February — up to 30.8 mm, coinciding with snowfall periods.From October to February, the Kaliningrad region receives an average of about 352.66 mm of precipitation (see Fig. 5).In the conditions of a humid climate and the presence of gleic soils, with gleyness in the lower soil horizons, signs of soil overmoistening manifested locally on the surface of the studied field in the form of "water lenses" — secondary overmoistening of drained soils. The sizes of the flooded areas ranged from 60 to 260 m². Seven such areas were identified in this field. On one of them, the surface water reached 16–18 cm (in the experimental field area with turf-gley soils), while in the others, it was up to 4–8 cm (in the elementary soil area with turf-slightly podzolized gleic soils).

The conditions of overmoistening in the edaphotopic environment of the agroecosystem of winter wheat affected the state of the plants during their winter dormancy. Under overmoistening conditions, degradation processes were recorded in the main tissues of the upper parts of the leaf blades (on January 18, 2022, and January 26, 2025), which resulted in a reduction of healthy leaf area (Figure 6).Crops in areas of waterlogging experience oxygen root "starvation" — the leaves are wilted, yellow, and brown in places, and the leaf sheaths and roots have also changed color from the normal milk-white to straw-yellow. The formation of the root system under conditions of soil overmoistening is characterized by the elongation of some adventitious roots. The average plant density over the two studied winter periods was 384±14 plants/m².

Overmoistening of the plant growth environment primarily manifests as partial necrosis of the protective, fundamental, and conducting tissues of the leaf blade. A decrease in biomass from 539.84±29.6 g/m² (under moderate overmoistening) to 343.52±13.7 g/m², and by 85–90% (under flooding conditions), which in percentage terms is 36.37%, was observed 10 days after spring fertilization.

When daytime temperatures in March rose to 8-15°C and remained at that level for 7 days, a resumption of tillering and plant growth was noted. At a soil moisture content (SMC) of 36.8%, the resumption of vegetation was more intense compared to plants growing in soil with an SMC of 41.44% (Figure 7), which exhibited low vitality, with significantly fewer healthy leaf blades remaining by that time. When SMC increased to 55.12%, a mortality rate of 85-90% of the plant organisms was recorded. This generally corresponded to areas where surface water was present.In the overall condition of the winter wheat crop by mid-March, a critical period was noted in the need for nitrogen nutrition — the beginning of the 21–23 development stage (according to BBCH), mitigated by the application of nitrate-ammonium fertilizer (NH4NH3) at a rate of 100 kg/ha. The assessment of plant density per square meter showed that the number of plants under prolonged soil overmoistening decreased by 7.5%, while the productivity of underground and aboveground biomass was lower by 196.32±32.1 g/m².

4. Conclusion

In the conditions of the Kaliningrad region, the most likely occurrence is the development of waterlogging in gley soils. In this regard, monitoring and the creation of ecological-hydrological passports for fields are necessary to make targeted, economically justified decisions for optimizing the water-air regime of soils.

Waterlogging of soils during the overwintering period of winter crops can be classified as a separate risk group, as it is forecasted to lead to a decrease in the productivity of cereal crops. This forecast will be localized, specifically for areas of the agro-phytocenosis where surface water has accumulated.

Waterlogging of the plant habitat primarily affects the partial necrosis of protective, fundamental, and conducting tissues of the leaf blade. A decrease in biomass from 539.84±29.6 g/m² (under conditions of moderate waterlogging) to 343.52±13.7 g/m², and by 85-90% (under flooding conditions), which in percentage terms amounts to 36.37%, was observed 10 days after spring fertilization.

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