Crop Rotation - mixing things up
As very amateur home gardeners (speaking from personal experience) most of us know that crop rotation is something that is going to help us grow healthy happy veggies that we (instead of very hungry caterpillars and other pests) get to enjoy munching on.
Knowing is one thing, but being organised enough to do more than not plant the tomatoes in the same bed as last year, is another. However, we don’t need to have a degree in agro-science or horticulture to understand the common sense theory that different crops use up different nutrients in the soil, so it might be better to give that patch a rest from this year’s lodgers and offer it a crop with different tastes.
A useful fact to remember is that while many vegetables remove many and various nutrients from the soil during their growing periods, a number also replace nutrients (eg beans, peas and other legumes). So by varying what we plant, and what type of crop follows another, we can ensure that our vegies get what they need from the soil… and we get what we need from our vegies!
Essentially, each area should be planted with a different plant family each season (generally every six months), to help avoid any nasty pest and disease outbreaks.
The other reason for this type of planting sequence is that some plants are referred to as “heavy” feeders, while others are “light” feeders. By introducing a crop rotation system, we can estimate the potential levels of soil nutrients remaining in the plot and plant up accordingly.
So a key basic for crop rotation is a little bit of knowledge about plant families.
Know your vegies. How hungry are they?
- Fruity things, such as cucumbers and tomatoes, are heavy feeders
- Brassicas (cabbages, etc) are medium feeders.
- Rooty things, eg onions and carrots, are light feeders.
- Legumes (beans, etc) are non-feeders (they can fix their own nitrogen).
- Leafy things (lettuce, spinach, silverbeet, etc) are pretty neutral - don’t have much impact on the soil and are not too fussy.
So, alternating light and heavy feeders, a six year crop rotation (if you have an extensive vegie garden) might be:
- Legumes (beans, peas etc).
- Brassicas (cabbage, broccolietc).
- roots:onions, leeks
- cucumber, pumpkin, etc
- roots: carrots
- tomatoes, potatoes
But of course you might not have the space, time or energy for such a minimarket garden approach. So to make it more manageble, you might:
- Combine some things: eg all the ‘roots’.
- Omit some things: eg never plant brassicas (did you really want cabbages and brussel sprouts anyway?)
- The most common solution: plant a cool season crop (e.g. brassicas) followed by a warm season crop (e.g. tomatoes or cucumbers) into a single bed over the course of a year.