Assessment of catalase soil activity under amaranth cultivation not exposed to chemical protection methods

The aim of the study was to determine the influence of habitat, cultivar and developmental growth stage on catalase activity in soil under two amaranth cultivars – Rawa (Amaranthus cruentus L.) and Aztek (Amaranthus hypochondriacus × Amaranthus hybridus L.). In a 3-year field experiment (2013–2015), amaranth’s plants were grown in a wide-row spacing on the soil of the good wheat complex in south-eastern Poland (50°71'N, 23°04'E). The field experiment included 4 variable factors: weather conditions; selected amaranth growth stages (5-leaf, full flowering and seed maturity stages); NPK dose combinations (I: 40 kg N ∙ ha–1, 30 kg P ∙ ha–1, 30 kg K ∙ ha–1; II: 60 kg N ∙ ha–1, 40 kg P ∙ ha–1, 40 kg K ∙ ha–1; III: 80 kg N ∙ ha–1, 50 kg P ∙ ha–1, 50 kg K ∙ ha–1; IV: 120 kg N ∙ ha–1, 70 kg P ∙ ha–1, 70 kg K ∙ ha–1) and two cultivars (‘Rawa’ and ‘Aztek’). No pesticides are applied in the cultivation due to the absence of pathogens and pests of this plant in Poland. Plant protection was limited to reducing weed infestation twice. The conducted research showed that weather conditions were the main factor affecting catalase activity in the soil under amaranth cultivation, followed by other factors, such as fertilization, cultivar and growth stage. All the analyzed factors proved to exert a significant impact on organic matter content in the soil, while only the applied NPK fertilization had effect on sorption capacity. Moreover, it was found that the cv. Aztek positively influenced the activity of catalase and humus accumulation in the soil in comparison to the cv. Rawa. The beneficial effect of amaranth on the soil environment and its enzymatic activity was ascribed to the lack of introduced pesticides.