Researchers studied how two types of beneficial fungi (mycorrhizal and saprophytic) can help a Chilean tree called Quillaja saponaria grow better in sandy soil mixed with treated sewage sludge. When plants were inoculated with these fungi and given moderate amounts of sludge, they showed significantly improved growth. The saprophytic fungus alone produced the best results, increasing plant height by over 300%. This approach could help recycle sewage waste while growing useful plants that produce saponins used in medicine and industry.