The effect of biochar on mycorrhizal fungi mediated nutrient uptake by coconut (Cocos nucifera L.) seedlings grown on a Sandy Regosol

Abstract

Biochar amendment of soil may ameliorate inherently infertile soils, such as in the typical coconut (Cocos nucifera L.) growth areas along tropical coasts, where, moreover, temporary moisture stress commonly occurs. We conducted a pot experiment to evaluate the effects of biochar soil amendment (1% w/w) produced from Gliricidia sepium stems (BC-Gly) and rice husks (BC-RiH) on the growth of coconut seedlings and on N and P uptake mediated by mycorrhizae under wet or dry conditions in a Sandy Regosol. The pots were divided into root and hyphal zones by a nylon mesh, where 15N labelled N and P nutrients were only provided in the hyphal zone. Under wet conditions, biochar application did not affect plant growth, while under dry conditions, the BC-Gly increased root and plant growth similar to that under wet conditions. BC-Gly increased the acidic pH of the soil to a neutral level, and the microbial community shifted towards a higher fungal abundance. The P accumulated (Pacc) in roots was higher with BC-Gly and BC-RiH under dry and wet conditions, respectively. Pacc weakly correlated with the abundance of arbuscular mycorrhizal fungi (AMF) in the hyphal zone. With BC-Gly roots showed lower N derived from fertilizer. We conclude that biochar application has no impact on crop growth under wet conditions, while under dry conditions, BC-Gly stimulates crop growth and P uptake, probably through liming induced P availability but also possibly by some enhancement of AMF growth. The shift in the fungal-oriented microbial community and reduced plant fertilizer N uptake suggested that BC-Gly acted as an additional N source. Graphical Abstract

Interactive effect of arbuscular mycorrhizal fungi (AMF) and transplanting media improves early growth, physiological traits, and soil nutrient status of coconut ‘Bido’ under tropical monsoon climate

“…Optimal AMF colonization is widely recognized for its ability to increase inorganic nutrients, especially P (Nirukshan et al, 2022). Several studies have indicated significant increases in P contents in the rhizosphere due to AMF effects, ranging from 54.39% to 76.13% (El-Sherbeny et al, 2022).…”

“…This study found that the treatment led to a significant increase in NRA (79.5%). In addition, AMF in the biochar can be utilized as a source of N for coconut seedlings, due to reduced absorption of chemical N fertilizer (Nirukshan et al, 2022). This increase in N was due to a symbiotic system (extra radicle system), in the form of C protein pools that capture C from NO3or NH4 + from the soil (Ebbisa, 2022).…”

“…The development of superior traits in coconuts across different environments relies on the influence of transplanting media and cultivation treatment. Research by Nirukshan et al (2022) found that a dry condition application of arbuscular mycorrhizal fungi (AMF) resulted in increased early growth of coconuts and enhanced P absorption. Similarly, Sulistiono et al (2020) report that the combination of AMF inoculation (commercial species) with NPK fertilizer during the transplantation of coconut seedlings, results in a 41.50% increase in AMF colonization, as well as improved nitrate reductase activity and root surface area under tropical monsoon climate, Indonesia.…”