Saturday's Scribe - Gardening by plots

Combine Street Community Garden, Coffs Harbour

Kincumber Community Garden plots

Let’s talk about crop rotation. Generally speaking, the longer you can leave between planting the same crop in the same bed, the better. The reasons for this are quite simple and the two most obvious are:
• pests and diseases will build up, and,
• soil nutrients that the crop fed on will be depleted and need replacement.

Crop rotation is not rocket science, however, at the same time it is not a hard-and-fast rule. Sometimes, if the seasonal conditions are right and you have good soil bed nutrients you will get away with repeat season crops. For rotation purposes, however, if you want to fallow the rotation method and your soils are not good and need lots of nutrient replenishing, you should rotate between 3 beds, but obviously, your method of rotation will depend on how big your garden is and what you choose to grow.

I tried a two plot rotation and only got moderate success until I changed to three plots and changed what was in those beds once a year. But, regardless of how many beds you have, it's a good idea to put a green manure crop in every year or two and to also fork in some good compost.

For a cheap green manure gather up all your old and out of date seed packets - they can be anything as long as they're not woody plants not root vegetables – and lightly fork the bed to loosen up the soil and then broadcast the seed generously across the whole bed. Water the seed in well and in about 6 to 10 weeks, when the plants are approximately 1 metre high, cut them down and dig them through and this green manure crop will revitalise your soil, in situ. Now take your compost and fork that through your beds and give it a good watering. Leave it for about two weeks.

If you haven't got a lot of left over seeds to make your own green manure, you can top it up with some commercial green manure mix.

I also compost my grass clippings in five bottomless bins – the plastic type with a lid where when the material is ripe for use you merely lift the bin off the contents – and I add all my kitchen waste with the exception of fats and citrus waste material. A handful of blood and bone, a handful of complete fertiliser and also a handful of hydrated lime also help to break down the compost material and add essential nutrients.

Australian-made Gedye compost bin made from recycled plastic

Any animal manure you can get access to is also a good additive, particularly poultry manure that is contained in straw floor bedding from poultry sheds, although, sheep dung, cow pads and even horse manure will also do. A word of caution tho’ – do not overuse horse manure as it does not contain a great amount of nutrients but it is a good ‘compost conditioner’ insofar that it does help prevent compost materials from becoming too wet and ‘clogging’.

Let your compost bin fill – it will shrink down as the vegetable matter looses moisture – and when full, cap and seal with some gaffer tape and leave all winter. Come spring, gently lift the bin to check your progress. If the material has composted it will be a blackish-brown semi-solid, holding its shape without the bin to secure it and should fork nice and easily. It should also have that ‘manure odour’ to it.

A local friend of mine is a real ‘green thumb’ gardener who runs a four plot rotation garden bed. This is what his thoughts are:

"The first bed starts off with a mixture of roots crops (carrots, parsnips and beetroot) and vegetables belonging to the allium family (onions, garlic and leeks). The second bed begins with sweet corn and cucurbits (pumpkins, squash, cucumber, zucchini and maybe even some watermelons). The third bed in spring starts with the vegetables that prefer a slightly lower pH (also known as acid lovers) such as tomatoes, capsicums (bell peppers), chillies and eggplants. And the fourth bed can be used to grow legumes (peas and beans) and brassicas (cabbages, broccoli, cauliflower and bok choy).

As a general rule, in a crop rotation method, a leafy bed which is a high nitrogen feeder may be followed by a legume crop to fix that nitrogen back into the soil and then you may want to chuck a crop of corn in to take advantage of that nitrogen.By the following year the sweet corn and cucurbits replace the root crops and onions. The tomatoes, bell peppers and eggplants replace the sweet corn and cucurbits (after the green manure has been dug into the bed). The legumes and brassicas replace the tomatoes and their friends. And of course next, the root crops and onions replace the legumes and brassicas. This system continues so that no vegetable group is ever planted in the same place twice over the four year period.”

Like most things, when it comes to crop rotation, don't be too fanatical. As long as you move things around, put in the occasional green manure crop and rest your beds, you can prevent pest and diseases and you'll be well on your way to a rich, well structured soil.