Co-application of biochar and phosphorus increases soil microbial biomass, mycorrhizal colonization, growth, and nutrition of subterranean clover

Phosphorus (P) plays important roles in the arbuscular mycorrhizal (AM) colonization and rhizobium nodulation processes. Additionally, biochar's positive roles in mycorrhizal colonization and nodulation are articulated. However, the effect of the co-application of biochar and P on AM colonization and rhizobium nodulation was poorly studied. This study investigated the effect of the co-application of wheat straw biochar and P using soil columns on mycorrhizal colonization, nodulation, and the growth of subterranean clover. The soil was amended with wheat straw biochar at 0, 5, and 10 t ha^-1 with different levels of P fertilizer at 0, 5, and 10 kg P ha^-1. These studies showed that adding biochar at 5 t ha^-1 along with mineral P fertilizer increased plant growth, mycorrhizal root colonization and nodulation, and P concentration in plants. In most cases, the increasing trend of the biomass yield was higher when biochar and the P fertilizer were applied together at a higher level (P10). These findings suggested that an increased biochar application rate can increase the subterranean clover growth in soil with either no (P0) or a lower P (P5) fertilizer application. Mycorrhizal colonization could help to improve the P supply and subsequently stimulate the root nodulation of leguminous plants.