Contrasted effects of biochar on maize growth and N use efficiency depending on soil conditions

Biochar amendment may improve crop growth through its nutrients and indirect fertility. However, this improvement varies in a wide range of biochars, crops, and soils. Our objectives were to determine the response of crop growth to biochar amendment and to assess the N use efficiency relative to the biochar and the soil types. In this pot experiment, we investi-gated five typical agricultural soils in China amended with two biochars. Four treatments were designed: the soil itself as a control, the soil amended with 1% biochar, the soil with fertilizer NPK, and the soil with added biochar and fertilizer. Biochar amendment increased the maize biomass and the N use efficiency in the red soil (p<0.05) but not in the other four soils (p>0.05). In the red soil, the biomass under biochar+NPK was 2.67-3.49 times higher than that of only NPK, and 1.48-1.62 times higher than that of only biochar amendment, 21-36 and 35-42% of which were contributed from biochar fertility and indirect fertility, respectively. This study indicates that biochar amendment is very plausible for the red soil but has a minor or even negative effect on the other four soils in China.