Ecological regimes of reclaimed lands in the Novgorod region

Studies of the ecological regimes of groundwater and moisture reserves were carried out in the Novgorod Region in 2014–2023 in conditions of arid (HTC 0.9...1.1) and wet vegetation periods (HTC 1.69...2.46) on sod-podzolic loamy soils drained by closed drainage structures: shallow with a depth of 70 cm; two variants of a medium-deep drainage with a depth of 110 cm with filling of the drainage trench with wood chips and sand-gravel mixture; two-tiered, consisting of a lower tier of tubular drains with a depth of 110 cm and an upper tier of tubeless drains perpendicular to it, located at a depth of 60 cm. Analysis of the nature of changes in the groundwater level showed that the minimum depth of groundwater in both wet and dry years was observed at the beginning of the growing season, the second peak of groundwater rise in wet years was observed in August, in dry years it was absent. The highest average seasonal groundwater level was observed in excessively humid 2017 (HTC = 2.46) in the variants of medium–deep drainage with backfilling of chips (30 cm) and shallow drainage (33 cm), the lowest – in the variant of two-tier drainage (58 cm). Analysis of humidity regimes on experimental systems showed that with shallow drainage in a humid year, more than a third, and in an excessively humid year, more than 2/3 of the duration of the growing season, the upper 30-centimeter horizon was in a waterlogged state, and with two-tier drainage, there were no periods of excessive moisture. At the same time, in wet years, the probability of periods with insufficient soil moisture ranged from 8 % (with medium-deep drainage with sand-gravel mixture) to 25 % (with two-tier drainage) In dry years, there was a lack of moisture in the upper soil horizon in the two-tier drainage variant of about 70 %, in other variants this value was slightly lower (62–65 %). The ecological soil regimes formed under the influence of two-tier drainage in modern climatic conditions had a significant impact on the hay yield of perennial grasses (70 % of fodder cereals), which allowed for an average yield increase of 0.9 t/ha relative to the variant with shallow drainage during both wet and dry growing seasons.