Phosphate foliar application increases biomass and P concentration in P deficient maize

Background : Foliar application is mainly used in agriculture as a targeted top‐up application to prevent deficiencies or during anthesis to improve quality. Hence, foliar fertilization usually occurs in plants that are in good condition and capable of uptake through the leaf. However, the extent to which plants utilize a nutrient under conditions of deficiency is also of importance. Aims : Our aim was to determine the response of P deficient maize plants to P foliar application at various concentrations and to investigate possible differences between the adaxial and abaxial sides of leaves with regard to uptake. Methods : Maize plants were grown under P deficiency in nutrient solution for two weeks followed by 2–3 foliar P treatments over a period of three weeks. Three different foliar P concentrations were compared. Older and younger shoots and roots were analyzed. In a second experiment, the influence of the leaf side on P uptake was determined by an infiltration/centrifugation method on the 5 th leaf and total P in the 4 th leaf, older and younger shoot, and root. Results : Foliar application significantly increased the biomass and P concentration in deficient maize, including the roots. Omission of a third application and a concomitant increase in the application concentration achieved comparable results. Uptake occurred on both sides of the leaf with no significant differences. Conclusions : Maize plants are able to absorb and utilize foliar‐applied P, even under deficient conditions and independently of leaf side. P foliar application can therefore be used as a top‐up application in deficiency situations. Moreover, the number of applications can be reduced at higher P application concentrations.