Enhanced retention and clean dewatering of nutrients in a slow-release organic silicon fertilizer

The development of sustainable fertilizers prepared from local and renewable resources is an increasingly urgent challenge faced by agricultural and food sectors globally. This challenge is complicated by the need to deliver nutrients directly to crops with minimal environmental impact. Here, we explore the characteristics of an organic silicon fertilizer prepared by treatment of digestate using potassium silicate and calcium chloride. The results show that the fertilizer has a porous structure in which organic matter and nutrients of digestate become embedded, thus facilitating the benefits of digestate by increasing nutrient retention by 72%–98% and decreasing the nutrient leaching rate by 81%–96%. Crop trials demonstrate that crop yields were increased by 20%–91% compared with mineral and organic alternatives. The findings suggest that these fertilizers could enable a cost-effective end use for digestate and have profound implications for the achievement of net-zero policies.