Abstract
Anaerobic digestion is a valuable process to use livestock effluents to produce green energy and a by-product called digestate with fertilising value. This work aimed at evaluating the fertilising value of the solid fraction (SF) of a digestate as an organic amendment and as a source of nitrogen to crops replacing mineral N. A field experiment was done with two consecutive vegetable crops. The treatments were: a control without fertilisation; Ni85 mineral fertilisation with 85 kg ha−1 of mineral N; fertiliser with digestate at an increasing nitrogen application rate (kg N ha−1): DG-N85 DG-N170, DG-N170+85, DG-N170+170; fertilisation with digestate together with Ni: DG-N85+Ni60, DG-N170+Ni60, DG-N170+Ni25. The results showed a soil organic amendment effect of the SF with a beneficial effect on SOM, soil pH and exchangeable bases. The SF was able to replace part of the mineral N fertilisation. The low mineralisation of the stable organic matter together with some immobilisation of mineral N from SF caused low N availability. The fertilisation planning should consider the SF ratio between the organic N (NO) and total N (TKN). Low NO:TKN ratios (≈0.65) needed lower Ni addition to maintaining the biomass production similar to the mineral fertilisation.
Highlights
The anaerobic digestion of livestock effluents is considered valuable since it adds value to slurries since the process provides biogas (45–85% CH4 and 25–50% CO2) as a renewable energy source and digestate with fertilising value to agricultural soils
In the case of the lettuce, the relative yield ranged from 72–74% in DG-N85 and DG-N170+85 to 111–112% in DG-N85+Ni60 and DG-N170+Ni60 treatments
We can observe that the lettuce biomass and relative yield (RY) of the DG-N85 and DG-N170+85 treatments showed statistically similar values to the control and were significantly lower than the Ni85 treatment
Summary
The anaerobic digestion of livestock effluents is considered valuable since it adds value to slurries since the process provides biogas (45–85% CH4 and 25–50% CO2) as a renewable energy source and digestate with fertilising value to agricultural soils. After S/L separation, the liquid fraction (LF) contain the majority of the total Kjeldahl nitrogen (TKN) of the digestate with values around 87% [12] and with an average content (n = 11) of 97.5 g TKN kg−1 DM which is mainly (61%) in the available N-NH4 (TAN) mineral form [13]. These authors concluded that the LF could be used as a substitute for N mineral fertilisers, and the solid fraction (SF) can be proposed as an NP-organic fertiliser. These results suggested that the SF can have a different ability to release N to crops, resulting from the proportion between their mineral and organic N forms
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
