Elemental composition of the aboveground biomass of energy plants as affected by growth stages

Abstract

Purpose. Determine the content of chemical elements in different parts of the vegetative mass of bioenergy crops. Methods. Experiments on the technology of growing switchgrass, energy willow and miscanthus were laid at the Yaltushkiv EBS. Winter wheat was a pre-crop for energy crops. The experiments were based on generally accepted methods of growing these crops. During the growing season accounting and observation were conducted and determination of the biochemical composition of the aboveground mass of energy plants. was performed. Results. It was found that the nitrogen content changed the most in June. Thus, in June, its content in the leaves varied from 0.20 to 0.22%, and in the stems from 0.18 to 0.24%, depending on the energy crop. By August, the nitrogen content increased by 9–50% in miscanthus and willow leaves and by 4–22% in switchgrass and willow stems. During the growing season, the phosphorus content in the leaves decreased by 2–12%. The dynamics of phosphorus accumulation in the stems of energy crops was different. In the stems of miscanthus, its content did not change, while in other energy crops increased. The potassium content in switchgrass and willow leaves increased by 5–13% during the growing season, while in miscanthus it decreased by 3%. In stems, its content in miscanthus and switchgrass increased, and in energy willow decreased. It should be noted that the potassium content in the leaves was 8.1–9.8 times higher compared to nitrogen and 5.3–8.5 times higher in the stems. Of the studied trace elements, the manganese content was the highest. Thus, in the leaves of miscanthus its content was 1.9 mg/kg or 2.1 times, willow 1.24 mg/kg, or 12%, and switchgrass 1.13 mg/kg, or 2% higher compared to the stem. The iron content changed similarly. The content of zinc in the leaves and stems of willow and switchgrass almost did not change, but in the leaves of miscanthus was 2.0 times higher than the stem. The content of copper and cadmium was almost the same in the leaves and stems and was 0.01–0.04 and 0.001 mg/kg of dry weight, respectively. The lead content in miscanthus and willow stems was higher, and in switchgrass the same (0.01 mg/kg). The chlorine content in the leaves of bioenergy crops was 1.3–2.5 times lower compared to the stems. The sulfur content in miscanthus leaves was 1.4 times lower than in stems, and in other crops almost the same. Conclusions. It was found that in the leaves of switchgrass nitrogen content and in miscanthus potassium content and phosphorus content of all crops decreases during the growing season. In the leaves, the nitrogen content in miscanthus, willow and potassium content in switchgrass and willow increases. The content of trace elements in the vegetative mass is the highest in miscanthus and willow. The content of copper and cadmium in the leaves and stems is almost unchanged.