6.4 Crop Rotation

This cropping system involves rotating various kinds of crops in turn of the same land. It reduces fertility degradation, micro-nutrient deficiency and the outbreak of specific diseases.

To develop a good crop rotation plan, it is important to consider the character of each crop. There are mainly two factors to consider.

One is the degree of consumption of nutrients. For example, after or before a high nutrient consuming crop, growing a low nutrient consuming crop is appropriate.

Nutrient Consumption (from low to high consumption)

1. Leguminous crop
2. Root crop
3. Leaf crop
4. Fruit crop
5. Cereal crop

Cereal crops have the highest nutrient consumption. Legumes consume the least. In addition, legumes supply nitrogen (N) to the soil. So a key point for soil fertility maintenance is to put leguminous crops in the rotation.

The other factor is disease tolerance. If soil becomes contaminated by a pest or disease, it is necessary to plant a disease tolerant crop (e.g. cereal).

Disease Tolerance (from strong to weak)

1. Cereal crop
2. Root crop
3. Legume crop
4. Leaf crop
5. Fruit crop

Cereals are the most disease tolerant while fruit is the weakest crop. Cereals clean or “heal” the soil subsequently minimizing disease problems. (Note: This is applicable to the land where mainly vegetable crops are planted, not to the paddy where continuous cereal cropping is practiced.) So, a key point in minimizing disease problems is to put a cereal crop in the rotation.