The cornerstone of an integrated system. A minimum of four different crops is usual - although a longer rotation will be better - it builds soil fertility and reduces pests and diseases. Livestock in a rotation is beneficial as it provides organic fertiliser. The crops will depend on locality, markets and prices, but there are some broad principles:
- Crops that build soil fertility (e.g. legumes and grass) should be alternated with those that reduce fertility (e.g. potatoes and sugar beet).
- The sequence of crops should be used to control grass weeds in broad-leaf crops and broad-leaf weeds in cereals.
- Insect pests can be kept below economic thresholds by making sure no single type or group of crops are grown in succession.
- A mixture of winter- and spring-sown crops is beneficial.Large blocks of a single crop should be avoided.
- Diverse crop rotations spread farm workload, reduce the risk of poor incomes and minimise the impact of any one crop on the environment.
The mosaic of different crops provides a diversity of habitats for wildlife, and certain species benefit from the shifting pattern of crops from year to year.