The dissertation presents the results of scientific research on the optimal combination of primary tillage methods and preceding crops, which makes it possible to increase crop yield, preserve soil fertility, and ensure the economic efficiency of production while avoiding the negative effects of tillage.
For the first time, under the conditions of the Right-Bank Forest-Steppe of Ukraine, on typical medium-loamy chernozem, a comprehensive agrotechnical, economic, and energy evaluation of primary tillage variants (moldboard tillage – plowing to a depth of 23–25 cm; non-moldboard shallow tillage – disking to 14–16 cm; and non-moldboard surface tillage – disking to 6–8 cm) and preceding crops (grain corn, winter rapeseed, soybean, and sunflower) in the cultivation of spring barley was carried out.
Soil available moisture reserves were determined by the studied factors and also significantly depended on the moisture conditions of a particular year. On average over the years of research, the best conditions for accumulation and conservation of soil moisture were created when spring barley was grown after soybean and winter rapeseed. The most effective primary tillage options were shallow non-moldboard and surface non-moldboard tillage. As a result, the use of winter rapeseed as a preceding crop in combination with surface non-moldboard tillage provided the highest reserves of available moisture in the one-meter soil layer at the time of sowing over four years of research –170.1 mm (+7.5 mm compared to the control). This combination also ensured the highest values of available moisture in the 0–10 cm and 0–30 cm soil layers – 17.2 and 64.7 mm, respectively.
However, the analysis of soil moisture use efficiency by spring barley plants, expressed through the crop water consumption coefficient, showed that the most efficient moisture use for yield formation was observed when soybean was used as a preceding crop combined with moldboard plowing as the primary tillage, providing a water consumption coefficient of 280.6 m3/t.
The use of winter rapeseed as a preceding crop for spring barley, together with shallow and surface non-moldboard tillage, ensured the most favorable soil structural parameters throughout the growing season compared to other treatments.
The best combination of factors in terms of the content of agronomically valuable air-dry and water-stable structural aggregates was the use of winter rapeseed as a preceding crop against the background of shallow non-moldboard tillage.
As a result of the conducted research, a complex effect of preceding crops and primary tillage on the potential and actual weed infestation of the spring barley agrocenosis was established. It was noted that the best weed control effect was achieved when winter rapeseed was used as a preceding crop combined with moldboard tillage, which ensured the lowest number of weed seeds in the 0–10, 10–20, and 20–30 cm layers – 61.9, 57.8, and 34.1 million seeds/ha, respectively.
This treatment also provided the lowest levels of actual weed infestation at the beginning and throughout the growing season. In particular, the lowest number of weed seedlings before herbicide application was recorded–250 plants/m2, and by harvest–15 plants, of which 5 were reproductive. The fresh weight of weeds was 23.5 g/m2.
In terms of grain yield, the best combination in the experiment was soybean as a preceding crop and moldboard plowing (23–25 cm) as the primary tillage – 7.14 t/ha, which resulted in the highest increase compared to the control – 1.63 t/ha or 29.74 %. This combination also provided the highest yield structure indicators: number of grains per spike – 17.7 (+1.1), and 1000-grain weight – 49.1 g (+2.3 g).
Replacing moldboard plowing (23–25 cm) with shallow surface tillage (disking at 14–16 cm) with the same preceding crop provided the second highest yield – 6.96 t/ha (+1.45 t/ha or 26.33 % compared to the control). Considering LSD05(AB)=0.49 t/ha or 8.12 %, these results were not significantly different from the previous treatment.
Correlation and regression analysis showed that among the studied indicators, a strong positive correlation with yield was observed for nitrate nitrogen content in the soil (r=0.9); a moderate positive correlation–for available phosphorus (r=0.6), available moisture reserves at sowing (r=0.5) and flowering (r=0.3); and a moderate negative correlation – for soil bulk density (r=–0.3).
No significant correlation was found between crop yield and soil structure, available potassium content, or weed infestation at the time of weed control measures.
