Agro-environmental sustainability of using digestate fertilizer for solanaceous and leafy vegetables cultivation: Insights on fertilizer efficiency and risk assessment

Abstract

Digestate generated from anaerobic digestion (AD) has been widely used as digestate fertilizer (DF) for plant growth, but its application should be comprehensively investigated. This study evaluates the effects of different amounts of DF on crop growth, nutrient use efficiency (NUE), soil properties, and potential negative impacts of DF application (salinity and heavy metals (HMs)) with two different crops (Eggplant and Shanghai cabbage). In eggplant cultivation, the yield increased with the increase of DF amount, and the yield of the DF-680 group was the highest (65.4 t/ha) under the highest fertilizer amount. However, due to high ammonia volatilization loss and excessive application, the NUE of DF was only about half of that of chemical fertilizer (CF). Significantly different from eggplant, the high application amount of DF resulted in yield reduction in Shanghai cabbage cultivation. The yield and NUE of the DF-170 group were the highest, the yield was 46.5 t/ha, and the NUE was more than twice compared to CF. Moreover, DF can raise soil nitrogen storage and alleviate soil acidification caused by fertilization in both batches of cultivation. Nevertheless, the electrical conductivity (EC) value of the soil was increased by 2–3 times, and the long-term application may lead to soil salinization. On the other hand, the increase of DF application elevated the content of copper (Cu), zinc (Zn), and cadmium (Cd) in soil significantly but did not cause HMs contamination in crops and tillage soil. In summary, reasonable application amounts and methods should be considered when applying DF.