In a single-species crop population, all the individuals have the same requirements for nutrients, water, light, and other resources and have similar heights, root depths, and so on. As a result, the potential for mutually detrimental interactions (competitive interference) is very great, especially if a resource is limited. All other things being equal, the main factor affecting the level of negative interaction in a single-species population is the density of the plants. At a certain density, competitive interference among plants begins to become signicant, lowering the ability of each plant to produce harvestable biomass (Chapter 14 of Agroecology: The Ecology of Sustainable Food Systems).