OXYGEN.
How does it affect the protoxide of iron?
How does it neutralize the acids in the soil?
How does it affect its organic parts?
How does it form nitric acid?
How may it affect excrementitious matter of plants?
What effect has it on the mechanical condition of the soil?
Oxygen, though not taken up by plants in its pure form, may justly be classed among manures, if we consider its effects both chemical and mechanical in the soil.
1. By oxidizing or rusting some of the constituents of the soil, it prepares them for the uses of plants.
2. It unites with the protoxide of iron, and changes it to the peroxide.