In organic farming, different cropping patterns (crop rotation, mixed cropping and intercropping) are used to protect crops from weeds.
In crop rotation, different types of crops are grown in succession on the same piece of land. It helps in restoring mineral content of the soil. If same crop is grown in a field again and again, the soil becomes deficient for a particular set of minerals.
When different crops are grown alternately, the minerals used by one crop are replenished by the successive crop.
For example, a crop of cereals that uses up nitrogen is followed by a crop of pulses or groundnuts which has nitrogen-fixing bacteria in the root nodules. Hence, their roots help to replenish nitrogen content in the soil.