The role of biochar in improving soil properties, water retention and potato yield in a Fluvisol under temperate monsoon climate

Soil amendment with biochar provides great potential for improving soil fertility. This study, conducted in Kanazawa, Japan, in 2018, evaluated the effects of soil amendment with biochar, carbonized from animal manure and slaughterhouse wastes, on some properties of a loamy sand-textured Fluvisol and yield performance of potatoes. The laboratory experiment investigated the effects of biochar (0%, 1%, 2%, 4% and 8% (w/w)) on soil properties and water retention. The field experiment combined three biochar application rates (0, 2 and 4 t ha(-1)) with three mineral fertilizer rates (0%, 50% and 100% recommended nutrients from mineral fertilizers, (RNPK)). The treatments were applied in randomized complete blocks with three replicates. Soil amendment at the rates of 1%, 2%, 4% and 8% biochar (w/w) (i) reduced bulk densities by 1%-22%; (ii) increased soil porosity by 1%-16%; (iii) increased readily available soil water (RAW) by 10%-40%; and (iv) enabled 1-5 days more retention of the soil water content within the range of RAW. The combined application of 2 or 4 t ha(-1) biochar with 100% RNPK increased yield by 219%-313% and 295%-340%, and increased water use efficiency (WUE) of potato by 59%-98% and 129%-163% under optimal irrigation conditions relative to the sole application of biochar and the control treatments, respectively. Considering agricultural and environmental sustainability, the integrated application of 2-4 t ha(-1) biochar with a full dose of nutrients from mineral fertilizers is recommended for the loamy sand-textured Fluvisol of the North-central coast of Japan and other similar agroecologies.