Évora researchers swap part of coconut fibre for walnut shells and biochar in lettuce growing

University of Évora researchers have shown that walnut shells and biochar can replace 20 per cent of the coconut fibre in a horticultural growing medium without hurting lettuce yields. The trial at the Herdade Experimental da Mitra compared several blends. The best was 80 per cent coconut fibre, 12 per cent crushed walnut shells and 8 per cent biochar, yielding 7.1 kg of lettuce per square metre, similar to the coconut-only reference. Nitrate levels in the leaves fell by about 61 per cent and anthocyanins rose. The team says further work is needed on formulations, irrigation and other crops. The results appear in the journal Horticulturae.