Application of nutrient-rich biochars derived from Siam weed and durian shell in acidic sandy soil of Cambodia

Acidic and infertile soils with fast decomposition of organic matter causes major constraints for limited resource farmers in the tropics. Biochar derived from various feedstocks potentially improves such soils and reduce fertilizer inputs. We investigated the effects of biochars made from locally available Siam weed (Chromolaena odorata) and durian (Durio zibethinus) shell on plant growth and soil properties through a greenhouse pot experiment in Cambodia. Five treatments, namely no input (Control), 5 Mg ha−1 of Siam weed biochar (SB5) or durian shell biochar (DB5), and 15 Mg ha−1 of Siam weed biochar (SB15) or durian shell biochar (DB15), were applied to an acidic sandy soil for growing kuang futsoi (Brassica chinensis var. parachinensis). Both high dose biochars (15 Mg ha−1) were less effective than both low dose biochars (5 Mg ha−1) on plant parameters such as plant weights but performed better on soil properties. Both biochars were considered to have a direct liming effect or supply direct nutrients to the soil and plant, and to reduce the acidity of the acidic sandy soil. Both biochars contributed to recycle available nutrients, particularly potassium (K) and phosphorus (P) resources. DB15 and SB15 accelerated exchangeable K by about 591% and 147%, respectively, as well as increased water-extractable P by about 3135% and 1413%, respectively, from those of Control. Gathering potentially abundant feedstocks like Siam weed and durian shell as biochar materials would be beneficial for limited resource farmers to reduce the input cost under limited soil nutrient conditions.