Physicochemical characteristics of substrates of the mixture of coir with municipal solid waste compost and with biochar

The aim of this study was to evaluate the effect of mixing municipal solid waste compost and of biochar with coconut coir, in different ratios, on some chemical and physical properties of mixtures and its potential to grow plants. Coir was mixed with MWS and with biochar in the following ratios: 1:0, 3:1, 2:1, 1:1, 2:1 and 0:1 (v:v). The physicochemical characteristics measured were pH, electrical conductivity, organic carbon, organic matter, mass wetness, moisture content and bulk density. The characteristics that raises more issues in the MSW compost were the high electrical conductivity (4.81 dS m^‑1) and pH (8.21) and in the biochar was the high pH (9.11). The increase of coir in mix improved the chemical and physical characteristics and in either case, the most suitable mixture is the one with the ratio 3:1 (75% coir by volume in the mixture). However, the electrical conductivity (2.69 dS m^‑1) of the mix 3:1 coir/MSW compost was still higher than the salinity threshold of the majority of the crops. The pH in coir/MSW compost and coir/biochar at the 3:1 ratio was 6.73 and 6.74, respectively, slightly above the maximal value of adequate range (6.4). These findings indicate that the mix of coir with MSW compost and biochar increases the potential of those materials to be used as substrates to grow plants, but it is still necessary to do some adjustments.