Foliar phosphorus fertilization and the effect of surfactants on winter wheat (Triticum aestivum L.)

Reactions of phosphorus fertilizer in soils make its use efficiency very low. The common application practices are to broadcast and incorporate or to band P with the seed. Foliar application of P can be used as a supplemental P source allowing for the application of lower rates and when it is most needed, reducing costs and potential environment concerns due to surface run-off. The objective of this study was to evaluate the effect of applying triple super phosphate as a foliar P source with and without surfactant on winter wheat grain yield, phosphorus use efficiency, and grain P content. Four field trials at two experimental sites were established in 2008/2009 and 2009/2010 in Oklahoma using a randomized complete block design with three replications. Treatments were applied at Feekes 7 using triple super phosphate dissolved in water as a foliar fertilizer. The solution had a concentration of 66 g P L-1. All treatments received 112 kg N ha-1 preplant in both trials. The effect of broadcast preplant at rates of 0, 10, 20, and 40 kg P ha-1 and foliar top-dress at rates of 0, 5, and 10 kg P ha-1 were evaluated, with and without surfactants.;Foliar P fertilization and the combination of preplant and foliar P often resulted in a yield increase compared to the check and/or the broadcast application of 20 and 40 kg P ha-1. These methods of fertilization frequently produced maximum yield. Phosphorus use efficiency was improved with foliar nutrition compared to broadcast. The effect of foliar P on grain P concentration was not consistent. The influence of surfactant was also not consistent over trials. Non-ionic surfactant and crop oil improved phosphorus use efficiency, grain yield and grain P concentration compared to the lack of a surfactant in some cases but had a negative impact in other occasions. Foliar fertilization using TSP at 10 kg P ha-1 had a negative impact on yield and grain P concentration. Foliar P allows for supplemental applications of phosphorus and when it is most needed. Foliar P allows for the application of lower rates in relation to soil applied P while still being able to correct in-season deficiencies, and improve yield and phosphorus use efficiency.