This study investigated the response of corn silage to different combinations of zinc (Zn) and phosphorus (P) soil supply when grown in sandy soil. The soil was naturally poor in extractable Zn and rich in plant-available P. The experiment was conducted in outdoor containers. The treatments consisted of soil supply combinations of 3 levels of Zn (0, 5 and 10 mg Zn kg−1 of dry soil) and 4 levels of P (0, 12, 36 and 72 mg P2O5 kg−1 of dry soil). The results showed the absence of a significant effect (at p ≤ 0.05) of Zn-P interaction on plant growth, plant mineral content or total aerial dry weight at harvest. P application depressed Zn shoot content, and conversely, Zn supply slightly reduced P shoot content. The total aerial dry weight at harvest was not enhanced by P application. However, it was significantly increased by Zn supply of 5 mg·kg−1 only for the highest P (72 mg·kg−1) application (at p ≤ 0.05). This increase was around 15% compared to no Zn soil supply. It was especially linked to kernel dry weight and particularly to pollination rate. For the highest level of P supply, Zn applications significantly enhanced (at p ≤ 0.05) the kernel dry weight and the pollination rate by 22.1% and 38.4% respectively, compared to no Zn supply.