The next phase in the Mars base plan would be
for the human population on Mars to grow their own food, which could prove to have an
extremely successful yield. The Martian atmosphere is dense enough to protect crops grown
on the surface against solar flares. On Mars, as we have seen, age inflatable greenhouses
protected by geodesic domes could be readily deployed, rapidly creating a huge
temperate-environment domains for crop growth. In order for the crops to give a bountiful
yield, they will be kept in a separate dome from that of the habitation domes, which will
house the human population. The main difference between the two types of domes will be in
the carbon dioxide partial pressures allowed. In the habitation domes, the carbon dioxide
pressure will be limited to typical terrestrial levels of about 0.4 mbar. But in the
greenhouses, larger carbon dioxide levels of about seven mbar will be employed in an
effort to greatly increase the crop yield.
Concerning the fertility of Martian land, it seems that Mars is likely to prove an excellent medium for crop growth, even better than some areas on Earth! The Martian soil is rich with many elements such as phosphorus, calcium, magnesium and iron; however, the quantity of nitrogen, an obviously essential element, is unknown. If the Martian soil should indeed turn out to be lacking nitrates, then the nitrates could be synthesized.
The physical properties of Martian soil also seem to be favorable for plant growth. The soil layers appear to be loosely packed and porous, and well adapted to supporting plants. In addition, Martian soil contains smectite clays which are highly effective at buffering and stabilizing soil pH in the slightly acidic range.
The Martian greenhouses will be pressurized at five pounds per square inch. Initially the domes will be pressurized with Martian air, which is 95% carbon dioxide. Thus, the Martian plants will grow in heavily carbon dioxide rich greenhouse environment, and photosynthetic efficiency should benefit accordingly. Due to this carbon dioxide rich environment, the photosynthetic efficiency will be greater than that of Earth's!