There are two primary benefits to crop rotation, and they apply to the smallest of backyard farmers as much as to huge agro-conglomerates.

The first is based on the fact that all plants are prone to certain pest issues. For some it is a specific insect, while others are likely to get fungal infections. To prevent these issues from becoming overwhelming, one of the best tools of smart and chemical-free gardening is to put a given type of plant in a new place every year, as space allows. The idea is that any pest specific to your plant that is living in the soil from last year won't be able to find the plant in its new home. This is a great way to keep blemishes and worms off of root vegetables, minimize leaf miners, and generally keep the pests populations low for any kind of plant.

The second is the fact that each plant needs, depletes, and sometimes adds, a different combination of nutrients from the soil. Some plants, like peas, beans, and clover, will add nitrogen. Others, like carrots, tend to strip nitrogen out of the soil really quickly. As a result, you can accidentally create nutrient-poor zones if you keep planting something in the same spot.


Orderly rows make crop rotations easier

So how does a regular backyard gardener take this into account? The most basic part is simple: Plant each zone with a different plant than last year, and try to do it in an orderly fashion so that you can remember what you did. So, for instance, if you imagine each bullet below is a garden row,

if year one's rows are organized:

• carrots


• peas


• tomatoes


• onion


• potatoes

Then year two should go:

• potatoes


• carrots


• peas


• tomatoes


• onion

And year three:

• onion


• potatoes


• carrots


• peas


• tomatoes

There are some tricks here, like the fact that potatoes and tomatoes are biologically similar, so it helps if you don't make them direct neighbors. And the carrots are always marching behind the peas, which helps with soil nutrition. But really, the most important thing is to keep your plants on the move throughout the years. Even if you just grow two things in a single swath of dirt, switch them from side to side each year.

In another post, I'll delve a tiny bit into plant families, which will help the more adventurous gardeners plan a better crop rotation scheme. For most backyard veggie gardeners, though, just a one-year row shifting scheme as written above will do the trick.

New York Times contributor Olivia Judson examines a new species in the making:

The appearance of a new species is not so dramatic. The first members of a new species will typically be indistinguishable - to us - from the species they have evolved from. And while extinction has a clear final moment - the last member of a species dies - the formation of a new species does not usually happen in a single recognizable instant. Which is why we haven’t yet raised our glasses to celebrate, say, Rhagoletis pomonella, the apple maggot fly.

This species is in the process of splitting into two. Until the mid-1800s, R. pomonella was a hawthorn fly: adults met at hawthorn fruits to mate and lay eggs. But then apples were introduced to North America. Some haw flies found these fruits attractive places to gather, and began to mate and lay their eggs on apples instead.

Today, flies that like apples have become genetically distinct from those that like haw. There are a couple of reasons why. First, flies meet each other at fruits. Since most flies have a preference for one fruit over the other, haw-preferring flies tend to meet other haw-preferring flies, and ditto for apple flies.

Read all about it at the link.