Abstract. A field experiment was conducted to investigate the response of maize silage ( L.) to tillage depth under different soil firmness levels. The study was carried out on a 16 ha center-pivot irrigated field in a commercial farm located in the eastern region of Saudi Arabia. A soil firmness map was generated and used as a management map. This map was divided into three soil firmness zones based on soil cone index (low: 617 to 1270 kPa for a 0 to 15 cm depth in undisturbed soil, medium: 1271 to 1652 kPa and high: 1653 to 2306 kPa). Three tillage depth treatments (10, 20, and 25 cm) were imposed on each of the three soil firmness zones, using a tandem disc harrow. Maize growth parameters [plant population, plant height, and Normalized Difference Vegetation Index (NDVI)] and maize silage yield were used to evaluate the response of the maize crop to tillage depth. The results revealed that soil firmness and tillage depth at both early (25 days after sowing) and late (60 days after sowing) growth stages did not introduce significant effects on maize plant population. However, the plant height measured at 60 days after sowing showed a significant response to soil firmness. The lowest mean value of plant height (114.4 cm) was recorded at the high soil firmness level, while the greatest mean value (136.3 cm) was recorded under low soil firmness level. Also, significant differences in maize silage yield were recorded under different soil firmness levels and tillage depths. For maize silage production, a tillage depth of 10 cm was observed to be optimum for areas of low and medium soil firmness. For areas of high soil firmness, the optimum tillage depth was 20 cm.