Assessing Nitrogen Availability in Biobased Fertilizers: Effect of Vegetation on Mineralization Patterns

• Main Authors: Hongzhen Luo, Ana A. Robles-Aguilar, Ivona Sigurnjak, Evi Michels, Erik Meers
• Format: Article
• Language: English
• Published: MDPI AG 2021-09-01
• Series: Agriculture
• Subjects: N dynamics; immobilization; maize; incubation; digestate
• Online Access: https://www.mdpi.com/2077-0472/11/9/870

Biobased nitrogen (N) fertilizers derived from animal manure can substitute synthetic mineral N fertilizer and contribute to more sustainable agriculture. Practitioners need to obtain a reliable estimation of the biobased fertilizers’ N value. This study compared the estimates for pig slurry (PS) and liquid fraction of digestate (LFD) using laboratory incubation and plant-growing experiments. A no-N treatment was used as control and calcium ammonium nitrate (CAN) as synthetic mineral fertilizer. After 100 days of incubation, the addition of PS and LFD resulted in a net N mineralization rate of 10.6 ± 0.3% and 20.6 ± 0.4% of the total applied N, respectively. The addition of CAN showed no significant net mineralization or immobilization (net N release 96 ± 6%). In the pot experiment under vegetation, all fertilized treatments caused N immobilization with a negative net N mineralization rate of −51 ± 11%, −9 ± 4%, and −27 ± 10% of the total applied N in CAN, PS, and LFD treatments, respectively. Compared to the pot experiment, the laboratory incubation without vegetation may have overestimated the N value of biobased fertilizers. Vegetation resulted in a lower estimation of available N from fertilizers, probably due to intensified competition with soil microbes or increased N loss via denitrification.