Formation of biometric parameters of switchgrass on acid soils

Purpose. To establish the peculiarities of the biometric parameters of switchgrass cultivated on acid soils attributed to the category of marginal land.
Methods. Field experiment was carried out at the Uladivka-Liulyntsi Experimental Breeding Station of the Institute of Bioenergy Crops and Sugar Beet of the National Academy of Agrarian Sciences in the years 2019–2021. Switchgrass variety ‘Morozko’ was grown in the a three-factor field experiment, with the application of lime (25% of the need), MaxiMarin granulated adsorbent (30 kg/ha), potassium humate (Humifield) (50 g/ha) and Antistress AminoStar (1.0 l/ha) to the soil. The adsorbent was applied two weeks before sowing the crop locally in the rows, foliar application of fertilizers was carried out in the budding stage and the second time after two weeks.
Results. In the second year of cultivation, the plant density in the tillering stage was from 12 to 21, in the third year from 16 to 23. Since the plants already formed an optically dense crop in the first half of the vegetation season, there was no further increase in the plant density, and in all treatments of the experiment, the number of plants determined in the tillering stage was preserved at the time of harvesting. Application of lime to the soil did not have a significant impact on the formation of this indicator, and the main differences were only compared to the treatments with applying the adsorbent. The height of the plants in the tillering stage in the experiment was approximately at the same level: in 2020, 24–30 cm and 2021, 12–16 cm. A tendency of the increase was noted only in the treatments with adsorbent. Starting from the stage of leaf-tube formation, the influence of the factor of foliar application of fertilizers increased significantly, the effectiveness of which increased against the background of the adsorbent application. In particular, in the treatment with potassium humate, the plants were 5–15 cm taller in both years of the experiment compared to the corresponding controls, and in the case of the combined application of potassium humate with AminoStar Antistress plant height exceeded by 5–25 cm. Soil deoxidation also had a positive effect on plant growth: on average of the treatments without liming, in the leaf-tube formation, the plants were 48–88 cm tall, while with the application of lime 54–115 cm. In 2020, similar patterns of this indicator formation were noted in the following stages of development. On the other hand, in 2021, at the later stages of the crop vegetation, the difference between these experimental treatments decreased, and in the harvesting stage, the plants in the treatments where lime was not applied were even taller by 6 cm. A similar situation was observed in the treatments with the combined application of the adsorbent and foliar application of humates: in the stage of leaf-tube formation, the plant height was significantly higher, but already in the flowering stage it was practically equal to the control treatments, and at the time of harvesting it was somewhat lower.
Conclusions. The maximum values of the biometric parameters of switchgrass were obtained mostly in the treatments with the combination of all three investigated agrotechnical measures. At the same time, their formation was more significantly affected by the use of adsorbent and foliar feeding of plants than by liming the soil, the effect of which was mostly tendentious. At the same time, the effectiveness of these technological factors was largely determined by the weather conditions of the growing season, which in turn affected the growth processes of plants and caused certain variations in their biometric parameters over the years of research.