La maggior parte non espelle - assorbe!

Le radici di alcuni legumi emettono azoto fisso che migliora la qualità del suolo e alimenta le colonie di microrganismi del suolo che aderiscono alle radici. L'uso della parola 'rifiuti' è inappropriato in questo contesto.

Plant roots can exude many substances in liquid form, and these serve many different functions. Much of this is root mucilage made of polysaccharides (polymers of sugar in the same class as starch and cellulose). Root exudates are not quite like animal waste excretion, though. (They are closer in concept to urine than feces in that they are liquids which contain a lot of dissolved substances produced or processed by the plant, rather than the undigested food and dead gut bacteria of feces.)