Effects of biochar, compost and straw input on root exudation of maize (Zea mays L.): From function to morphology

•Root exudation plays a vital role in the soil–plant system.•Maize roots under straw input had different 1H NMR exudate profiles compared no straw.•Root modification mainly characterized by elongation of BC switched to thickening of SD.•Molecular evidence was provided by qRT-PCR for organic acid exudation and root growth.•Responses of root morphology and metabolome to straw input linked to exudation shift.