George's Gardening Tips - Crop Rotation!

Starting a vegetable garden from scratch is an exciting experience for many. Problems will inevitably arise and require patience and learning to overcome, but usually if the fundamentals of growing crops are well observed such as adding nutrients to the soil and ensuring adequate amounts of water and sunlight are available then initial yields can often be bountiful. After a few years, however, yields may decrease and plants can often look weaker than during previous seasons. To prevent this from happening it is important to apply the principles of crop rotation.

Crop rotation is the practice of rotating where annual crops are planted in a garden. This is typically done on a four year cycle, with a crop returning to its initial planting area after two or three years of being planted elsewhere.

There are two main reasons for crop rotation. Firstly, by rotating crops there is less chance that they will fall prey to pests each season. Pests will begin to gather in an area where there favourite crop is located. Over time their populations will increase, thus causing increasing amounts of damage to the crop. The same applies for soil-borne pathogens. Secondly, different crops require different types of levels of nutrients from the soil to grow. By rotating crops we prevent the soil from being depleted of nutrients (providing we also feed the soil with good quality compost).

There are two ways to devise a sequence for crop rotation. The first is to group crops into their plant families. This is because crops in the same families share many of the same characteristics, including which pests they are vulnerable to, and which nutrients they extract from the soil. As an example, potatoes and tomatoes are in the same family and very closely related genetically so it would be wise to avoid planting them after one another. Root crops such as beetroot and carrot can also be grouped together. Another method of crop rotation is to group crops into ‘heavy feeders’, ‘heavy givers’ and ‘light feeders’. Heavy feeders refer to crops which typically require a high level of nutrient from the soil, such as tomatoes and cabbage. Most crops are heavy feeders. Heavy givers such as peas and legumes actually feed the soil with nitrogen – an essential nutrient for leaf growth – and are good for following heavy feeders in a rotation system. Light feeders pull a lower volume of nutrients from the soil and are good for following heavy givers. Light feeders include carrots, mustard greens and Swiss chard.

It is also sensible to occasionally rest a garden bed completely for the season after applying a layer of compost and mulch.

In the Margan Garden we have numerous almost identical sized beds, and therefore crop rotation is relatively simple as there is not a great worry about available planting space when creating crop plans. However, in a small garden crop rotation can still be easy. Try to identify different spaces around the garden where crops could be grown, perhaps up a fence, or maybe incorporate some creative raised beds using different recycled materials such as bathtubs and tyres. Vegetable beds can also be divided into sections, with sections being separated by a perennial crop which doesn’t require rotation.