It has been previously demonstrated that dicotyledonous plants perform rhizophagy, a process in which live microbial cells are engulfed by root cells and digested to acquire the nutrients from the microbes. Here we tested the hypothesis that rhizophagy is a mechanism of nutrient acquisition that is not restricted to dicotyledonous plants. We report that the monocotyledonous species sugarcane (Saccharum officinarum x spontaneum), grown in controlled axenic conditions, incorporated yeast cells into root cells. This suggests that rhizophagy is an evolutionarily conserved trait that predates the divergence of dicot and monocot species. To explore the potential relevance and practical application of rhizophagy, we investigated brewers' yeast (Saccharomyces cerevisiae), a waste product of the brewing industry, for its role as biofertilizer. The addition of live or dead yeast to fertilized soil substantially increased the nitrogen (N) and phosphorus (P) content of roots and shoots of tomato (Solanum lycopersicum) and young sugarcane plants. Yeast addition to soil also increased the root-to-shoot ratio in both species and induced species-specific morphological changes that included increased tillering in sugarcane and greater shoot biomass in tomato plants. These findings support the notion that brewers' yeast is a cost-effective biofertilizer that improves not only plant nutrition but also plant vigor during the early growth phase. It remains to be established which yeast-derived substances trigger the observed plant growth effects, and how rhizophagy contributes to plant nutrient acquisition.