Biochar improves agro-environmental aspects of pig slurry compost as a substrate for crops with energy and remediation uses
2016
Sáez, J.A. | Belda, R.M. | Bernal, M.P. | Fornes, F.
Composting is considered an appropriate approach for stabilising and sanitising pig slurry, incorporating its nutrients into the soil-plant system. However, pig slurry compost (PSC) can be highly saline with high concentrations of Cu and Zn, and can emit greenhouse gases (GHGs) and volatile organic compounds (VOCs), when not properly stabilised. In order to produce substrates with adequate characteristics for containerised soilless plant production, PSC must be mixed with other materials. In this study two materials were chosen: coir (coconut fibre; CF), as the most popular material after peat for this purpose, and biochar (BCH), a novel material in this scenario. Substrates were prepared by mixing PSC:CF and PSC:BCH at 60:40, 40:60, 20:80 and 0:100 (% v:v) ratios and their physical and chemical characteristics, their emission of GHG and VOC and seed germination and growth of two species grown for non-food purposes (milk thistle (Sylibum marianum L.) and sunflower (Helianthus annuus L.)) were studied. The results showed that BCH was more adequate than CF for the preparation of substrates with PSC, enabling seed germination and plant growth by decreasing the EC and available Cu and Zn contents, hence limiting phytotoxic effects, whilst also reducing CO2, NO and VOC emissions. Toxic effects appeared in plants grown in substrates prepared with PSC at proportions greater than 20%; whilst at low rate (up to 20%) the beneficial effects might have been caused by the nutrients (N, P and K) supplied by PSC to the crops.
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