Our planet is able to sustain life because of this thingie called carbon dioxide, also known as CO2. Plants breathe it, and it's also responsible for the greenhouse effect: light from the sun is converted to heat and trapped by the CO2, so we have a warm and cozy climate. This also means the greenhouse effect is basically a good thing, just too much of it is kinda bad (for humans, plants like it). Now, the CO2 in the atmosphere is washed out by the rain and reacts with minerals in the ground to form carbonates (basically another type of mineral, i.e. a solid). This would mean that after while, there would be no CO2 left in the atmosphere. Enter volcanos and plate tectonics. The continents that make up the surface of our planet are in constant motion, and they can move under and over each other. When a continent slides below another one, it will melt. When the minerals melt through the heat that the core of our planet produces, the carbonates are broken up, and when a volcano erupts, a lot of CO2 is released back into the atmosphere. In fact, volcanic eruptions are the single biggest source of CO2, even with us already creating a lot of this stuff.
Without this cycle that is constantly melting the surface of our planet, our CO2 would soon be gone.
Mars has no volcanic activity. It was pretty active once, probably more than Earth, just look at Olympus Mons, but not anymore. Now, even if you manage to terraform Mars by releasing enough CO2 into its atmosphere, it will be converted to carbonates after a while, and your beautifully terraformed planet becomes a cold, barren rock again. It's impossible to constantly plough up Mars's surface manually. Sorry to burst your bubble here