Effect of the application of acid treated biosolids on marigold (Tagetes erecta) development

The use of biosolids for land restoration and crop production is a potential solution to improve food production worldwide. However, the microbial content usually restricts its application in crops that are consumed uncooked. An alternative practice is their use in floriculture. In this study, the effects of acid treated sludge on the development of marigold (Tagetes erecta) plants were evaluated under green house conditions. Biosolids were applied at the agronomic rate (AR) based on nitrogen requirements of the marigold. In addition, higher rates (10 and 20×AR) were applied to study their effect on the plants. Biosolids were mixed with tepetate (hard volcanic indurate layers). Due to its origin, tepetate lacks nutrients and organic matter to adequately support plant development. The best treatment for marigold development was 10×AR, as plants reached an average height of 107 cm, with a growing speed of 1.01 cm/d, which is 20 times more than the control. Plants that received no biosolids produced 0.25 buds and 0.5 flowers per plant. In contrast, AR and 10×AR showed a production that ranged from 2 to 29 buds/plant and 4 to 15 flowers/plant, respectively. These results indicate the viability of reusing acid treated biosolids to improve marigold development.