Biochar and cow manure organic fertilizer amendments improve the quality of composted green waste as a growth medium for the ornamental plant Centaurea Cyanus L.

This study is aimed to examine the combined effects of biochar (BC) and cow manure organic fertilizer (CM) added to composted green waste (CGW) on the growth of Centaurea cyanus L. (cornflower) plants. With a constant amount of CGW, the research adjusted the addition ratios of BC as 0%, 15%, 2and 5%, and CM as 0%, 10%, 20%, respectively (the base of % is the volume of CGW). According to the above proportion, the growth media were prepared to culture cornflower seedlings. After a cultivation period of 180 days, growth indexes, ornamental indexes, and nutrient content of cornflower plants were measured to identify the optimal combination of BC and CM. The results showed that the additives BC and CM could significantly improve the plant growth and the nutrient content of cornflower plants, especially when added the two simultaneously. Compared with CGW without amendments, CGW amended with 15% BC and 10% CM increased shoots fresh weight, roots fresh weight, total nitrogen content, flower number, and total chlorophyll content of cornflower plants by 159.1%, 25.0%, 68.9%, 218.8%, and 26.4%, respectively. In conclusion, BC and CM addition could improve the quality and increase the agronomic value of CGW, and the CGW amended with 15% BC and 10% CM was an ideal growth media for cornflower plant.