Abstract: The effect of K supply regimes and plastic film mulching on the harvest index (HI), reproductive allocation (RA) and size inequality of Lilium davidii var. unicolor population, was determined and the underlying mechanisms were explored. Compared with K₀ treatment, bulb yield, biological yield, HI and RA of L. davidii treated with K fertilizer increased 44.42%, 20.60%, 14.30% and 5.55% respectively under non-mulching conditions, while the increases were 57.21%, 13.89%, 23.30% and 7.35% respectively under mulching conditions. Either with mulching or non-mulching, size differences always decreased along the K supply gradient. The bulb yield and biological yield of L. davidii under mulching conditions increased by 15.59% and 13.09%, respectively compared with those under non-mulching conditions. However, HI and RA under mulching conditions were lower by 4.19% and 3.20% respectively than those under non-mulching conditions. Results suggest that the size inequality of L. davidii populations are closely correlated with K supply, and that under greater K supply there were relatively larger plants with higher HI. Growth redundancy under mulching conditions occurred in L. davidii populations, which may result from the exacerbated interplant competition and greater size inequality. Although there was a significant increase in bulb yield, L. davidii cultivation with plastic film mulching was not always the best method.