Yield of Green Mass of Forage Crops in Grain Plants Crop Rotations

This study focuses on evaluating the green mass yield of forage crops in grain-grass crop rotations with varying durations of using a clover-alfalfa-timothy grass mixture, considering certain abiotic factors. A stationary experiment conducted from 2013 to 2018 investigated three third-rotation crop rotation schemes: with one-year (A1), two-year (A2), and three-year (A3) utilization of the clover-alfalfa-timothy mixture. Two levels of mineral nutrition (N and N) were also studied against a background application of PK. The highest above-ground biomass yield was observed with two cuttings of the perennial grasses, averaging 17.6±0.9 t/ha, which represents a 14.2% increase compared to single-cut management. However, the drought in 2014 reduced the productivity of the second cut by half (2-fold) in the A2 rotation and by 1.4 times in the A3 rotation. The maximum green mass yield was recorded in 2015 within the A3 rotation, reaching 23.1 t/ha, 33.8% higher than in preceding years. Winter rye demonstrated high yield stability, averaging 15.4±1.1 t/ha regardless of the Selyaninov hydrothermal coefficient (HTC) and other studied factors. The application of N increased rye productivity to 17.5±1.0 t/ha (a 32.6% increase). Mustard, sown as a catch crop after cutting, showed a dependence on the HTC, with maximum yield (8 t/ha) achieved at an HTC of approximately 1.3. It was established that increasing the proportion of perennial grasses in the crop rotation did not consistently lead to higher green mass yield; the average annual yield in the A2 rotation was 15.1 t/ha, which was 31.3–37.0% lower than in the A1 and A3 rotations (19.8–20.7 t/ha). Humus content showed a positive correlation with yield: a 0.1% increase in humus corresponded to a 1.9% increase in green mass yield. The results indicate that the key factors influencing green mass formation for the studied crops are moisture availability (optimal HTC range 0.8–2.3), the level of mineral nutrition (yield increase from nitrogen application up to 24.0%), and soil humus content.