Phosphorus fertilization of plants tends to balance some of the effects that may occur with nitrogen fertilization. Phosphorus fertilization increases the strength of stems by increasing the thickening of cell walls. The strengthened cell walls increase the resistance of plants to diseases. The rate of maturation of crops is accelerated by phosphorus fertilization, thereby somewhat, but not fully, offsetting the delay in maturity that may occur with nitrogen fertilization. Lateral root development (branching) is stimulated by phosphorus. Roots proliferate in phosphorus-rich zones of soil due to the high availability of phosphorus and its stimulation of cell division. Lengths of primary roots may not be changed by phosphorus fertilization as the effects are principally on the development of branch roots.
Phosphorus is essential for flowering of plants. If phosphorus is defiient, flower size and abundance will be suppressed. Supplying of phosphorus to a defiient plant will increase flowering, but once suffiiency of phosphorus has been achieved, further increases in phosphorus fertilization will not increase flowering. If flowering has been restricted by an overabundance of nitrogen supply, phosphorus fertilization generally will not reverse this effect. Time is needed for plants to enter the reproductive stage and to begin flowering.