Higher Phosphorus Use Efficiency with Foliar Applied Phosphorus.
Clint Wilcox, Kefyalew Girma, William Raun, and Brian Arnall. Oklahoma State Univ, 368 Ag Hall, Stillwater, OK 74078
Foliar applications of phosphorus could improve use efficiency by minimizing soil applications in corn and wheat. A prediction can be made that foliar applied P would have higher use efficiencies than when applied to the soil. P deficiencies could theoretically be corrected with small amounts of P applied in a foliar fashion. Nine experiments were conducted for corn in 2002 and 2003 to determine foliar P rates and appropriate growth stages for application. Treatments were comprised of ten factorial combinations of three foliar P application timings and four rates of foliar P. Foliar application times were V4, V8 and VT corn growth stages. Foliar P rates were 0, 2, 4 and 8 kg ha-1. Nine trials were also conducted in winter wheat during 2002, 2003 and 2004 at Lahoma, Orlando, and Perkins, OK. A randomized complete block design with three replications was used to evaluate 12 treatments containing varying foliar P rates (0, 1, 2 and 4 kg ha-1 in 2002 and 2003 and additional 8, 12, 16 and 20 kg ha-1 in 2004 )with and without pre-plant rates of 30 kg ha-1. Foliar P applied at the VT growth stage in corn improved grain and forage P concentration which was reflected in increased grain yield in some of the experiments. Foliar P rate of 8 kg ha-1 improved yield to some extent and largely improved forage and grain P concentration, more than the lower rates. Foliar application of P at Feekes 7 (two nodes detectable) generally increased grain yields and P uptake versus no foliar P. Use efficiency was higher when P was applied at Feekes 10.54 (flowering completed). The results suggest that foliar P could be used as an efficient P management tool in corn and winter wheat when applied at the appropriate growth stage and rate.