Positive Effects of Biochar and Biochar-Compost on Maize Growth and Nutrient Availability in Two Agricultural Soils

Previous studies have reported positive, negative, or neutral effects on maize yield by the application of biochar and/or compost in the presence or absence of inorganic fertilization. This study investigated the influence of biochar, compost, and mixtures of the two, along with N fertilization, on maize (Zea mays L.) growth and nutrient status in two agricultural Mediterranean soils. Biochars (BC) were produced from grape pomace (GP) and rice husks (RH) by pyrolysis at 300°C (BC-GP; BC-RH). Maize was grown for 30 days after seedling emergence in a greenhouse pot trial in two Mediterranean soils (Sandy Loam-SL and Loam-L) amended with biochar or/and compost (BC-GP+compost; BC-RH+compost) at 2% (w/w) application rate with nitrogen (N) fertilization. The addition of BC-GP amendment resulted in the highest increase of aboveground dry weight (16 g/pot) compared to the control (6.27 g/pot) in SL soil, whereas in L soil the highest increase of aboveground dry weight resulted from BC-RH+compost (13.03 g/pot) compared to the control (2.43 g/pot). The addition of BC-GP+compost significantly increased phosphorus (P) concentration of the aboveground and belowground tissues only in L soil. Potassium (K) concentration of aboveground and belowground tissues significantly increased almost by all the amendments with the greatest increase being observed after the addition of BC-GP+compost in SL soil. To conclude, biochar addition could enhance plant growth, although soil conditions, type of biochar and additional fertilization should receive special attention in order to be used as a tool for sustainable agriculture.