Crop Rotation and Intercropping

Crop Rotation and Intercropping

Allocating Space, Planning and Laying Out

Having decided what you want to grow, you can then decide how much space you need for it. Alternatively, work it out the other way round and fill whatever space is provided by proportion. Either way, the vegetable plot needs careful positioning and laying out if any choice is possible. Preferably, it should be in full sun with no overhanging trees and as far away from trees, walls or hedges on its sunny side as practical.

Crop Rotation and Intercropping Wet boggy sites and low areas should be avoided as they will cause winter losses and frost damage in the spring. However, they may be ideal for summer salad crops, leeks and celery. The plot should be kept well away from big hedges — especially leylandii cypress and privet which will steal any goodness and moisture from the soil. Competition from any nearby trees and hedges can be reduced by digging a hip-deep slit trench parallel to them, cutting out and removing their roots and preventing them from returning by setting in a continuous plastic sheet before refilling the trench.

A vegetable plot should not be too far from the kitchen, a water point and the tool/potting shed or much time will be wasted going to and fro. The most frequently used path will be best hard surfaced or gravelled to make it more pleasant to use in wet conditions. Grass paths dividing up a plot are a serious error. They look nice initially, but are difficult to keep cut and edged, encourage slugs and other pests and soon get smeared by wear and mud. One easy way to get more from less space is if paths are replaced by stepping stones.

The shape of a plot is best square or rectangular as others make harder work, and it must be designed so that rows or beds run north-south so that the sun can shine evenly and not cause dense shade behind taller crops. For this reason, a long rectangular plot is best running east-west, with short rows or beds going north-south. If this means the plot is best aligned askew to the main garden then surround it with triangular borders and screens of fruit or low hedges to disguise it.

Do not make the hedges too tall or dense as air must be able to circulate freely. Borders and beds around the main vegetable plot will be useful for the perennial crops, such as asparagus or artichokes, and for seed, nursery and salad beds which need even more intensive care than the main plot.

In the smallest garden choice is rarely possible and the best use has to be made of what is available. Of course with less area to deal with then time and money can be applied more intensively. Thick mulches, deep digging, heavy feeding and cunning cropping can be used to squeeze more out of the smallest sunny space.


Rotation

Provision for rotation is important, but it is not necessary to divide the plot up into four quarters as shown in many books, then religiously following the potatoes, legumes, brassicas and roots cycle. What is critical is that you do not grow the crop or its near relations on the same ground year after year, but move it around or abandon it entirely for a year or two. It is not that important which you follow with which, though some combinations can be less satisfactory. For example, potatoes do not happily follow brassicas or legumes if the soil was limed for them. So roughly sticking to the traditional rotation cycle makes sense, but it is not gospel.

What you need to take most care with, is ensuring that potatoes are not returned to the same spot for as long as possible, that brassicas are similarly kept away for as long as possible and that the other vegetables do not return to their previous site from the year before. Of course, the more elaborate your rotation and the longer the gaps then the better the results. This is made easier if you grow a range of different crops in smaller amounts and if you include break crops such as flowers, strawberries or artichokes.

Rotation is greatly facilitated if you keep accurate records of what is grown where and when. The fixed bed system lends itself to this, though it is not difficult with rows if you use permanent markers on the plot.

Keep a book or a card file and record not only the crop and its position, but also its variety, sowing dates and performance, as this information aids future planning.


Blocks, rows, fixed and raised beds

Block and row planting are alternative ways of laying out crops. For those that need support such as peas, rows have the advantage provided they run north-south and don’t shade other crops. Peas and beans can also be grown up strings tied in a circle round a central pole. Rows are more wasteful of space and the paths between each row get compacted and require digging.

For most crops, especially those that are closely planted such as carrots, block plantings are advantageous. Apart from saving space, block planting helps with weed control because once the plants are half grown their foliage meets and excludes light from the soil, choking out seedling weeds. This also forms a favourable micro-climate and prevents moisture loss. Where netting or fleece is used to prevent pests reaching the plants, then rectangular block planting is obviously convenient. Although row planting is easiest when very large areas are being cultivated, block planting in small beds is much more suitable for most crops in most gardens.

Raised beds are becoming popular, but their main advantages accrue from their being fixed beds. They are simply permanent sub-plots surrounded with narrow paths (packed soil is sufficient). Since the beds are not walked on they need digging only every seven or eight years and they make block planting easy. Rows can still be run down the middle if they run north south. The ideal width is about four feet, as it is comfortable to reach in two feet from either side, and make them no longer than say sixteen feet or there is temptation to walk over rather than around them. Having permanently fixed beds makes record keeping and rotation simple, with each bed considered and treated as a separate little plot. Fixed beds slowly become raised beds naturally as mulches, compost and root residues build up.

Being raised has several advantages. It reduces the need for bending, increases the surface area which provides extra planting space, and improves aeration and evaporation. Raised beds warm up sooner, too, which gives an earlier start in the spring. In winter, cold air runs off the bed like water so giving slightly warmer conditions. However, raised beds also dry out more quickly in summer and mulches tend to slide off or be pulled off by birds. Still, on the whole, their advantages outweigh their drawbacks, especially if their shape is kept to the natural sine curve formed by slumping soil.

This then gives several useful micro-climates. The south end is a hot slope suitable for early cropping and tender herbs, while the north end is permanently shaded and suits saladings and leaf crops. The sides are protected from the wind and so keep moist, suiting leeks, roots and saladings. The top is open ground, but especially well suited to onions, shallots, brassicas, legumes as row crops and to overwintering vegetables.

Raising the beds artificially with planks, bricks or whatever reduces the area available, removes many of the useful micro-climates, adds to costs with the materials required and provides hiding places for pests. Paths of packed soil are sufficient, but get muddy in the wet. Straw and other mulches harbour pests and are hard to weed. So sharp sand or crushed gravel are much the best option, and it doesn’t matter if some gets mixed into the soil.


Extending the season

Using a seedbed makes it easier to spread the harvesting period because when a crop is transplanted it receives a slight check — the bigger a crop has grown the greater the check. For example, if one sowing of Brussels sprouts or lettuce is divided into three portions and then each portion is transplanted to its final position at ten days apart, each portion will mature at a slightly different time. Of course, for most vegetables, successive crops can also be ensured by sowing in several batches over weeks or months and by sowing different varieties that mature at different rates. The fastest are usually called earlies and tend to produce less than the slower main crops. Of course, cloches and growing under cover can greatly extend the season.


Intercropping, catch cropping and companion planting

These are ways to get more out of a small plot, and are made easier if you raise as many plants as possible in seedbeds or in pots (though remember that some crops, such as root vegetables, have to be sown in situ). The idea is that many crops, especially the slower growing ones, do not need all the space allocated to them all the time.

Catch cropping means using the quickest-growing crops, such as radishes, baby turnips and saladings, to fill the space before another crop has grown very big.

Intercropping is similar and refers simply to growing crops together. Also, when the main crop has finished growing and is standing waiting to be used, as with cabbages, intercropping means starting off the next crop in between so that when the latter is removed, the follow-on crop is already established and grows rapidly to fill the space made available. Do not overdo this, however, as crowding will give poorer results. Crops will compete as fiercely as weeds unless the spacing and timing are well controlled.

Companion crops are those which can be combined together most successfully and give added benefits over simple intercropping. Again great care must be taken not to crowd plants, but provided that sufficient air, light, nutrients and water are available, some combinations of crops do particularly well together, while others do not – see Companion Planting for a Healthy Garden. For example, instead of three beds growing peas, potatoes and sweet corn respectively, I find that growing three beds with all three crops on each I get a higher yield overall. I put the peas in a thin row down the middle and flank it on either side with alternate sweet corn and potato plants. The peas provide shelter for the tender young shoots, the potatoes keep the soil-covered and moist which the sweet corn and peas enjoy, while none shades out the others.

Crop Rotation and Intercropping - French Marigolds Further and most importantly, combining and mixing up crops significantly reduces the damage from pests and diseases. For example, I have found that beetroots grown between swede and parsnip do not get attacked by the birds, and brassicas surrounded by French beans suffer far fewer pests.

Most useful of all are French marigolds which should be planted in every plot and by paths and gates so you brush against them releasing their pungent, pest-confusing smell. Similarly, some annual herbs, such as chervil, dill and summer savory, are beneficial when grown amongst crops as their strong scents help hide the plants from their pests.

Perennial herbs, such as rosemary, thyme, sage, chives, southernwood, hyssop and lavender are beneficial when confined to the edges of the vegetable plot, where their scents are effective pest deterrents and their flowers bring in predators and pollinators.

06. January 2011 by admin
Categories: Featured, Organics, Vegetable Gardening | Tags: , | Comments Off on Crop Rotation and Intercropping

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