A farmer cultivates a different crop in a field during each of the first three years. In the fourth year, he plants a leguminous crop, such as clover, and then ploughs it back into the soil. In the following year, he begins the rotation again. How does the crop grown in the fourth year add mineral ions to the soil?
- Adecomposition: no; nitrification: yes; nitrogen fixation: yes
- Bdecomposition: yes; nitrification: no; nitrogen fixation: yes
- Cdecomposition: yes; nitrification: yes; nitrogen fixation: no
- Ddecomposition: yes; nitrification: yes; nitrogen fixation: yes