Intercropping: an Underutilized Tool

 

After nearly two decades of vegetable and fruit production, I have come to the conclusion that one of the most under-used tools in a farmer's toolbox is intercropping.  It doesn't seem to matter how big the farm is, whether it is certified organic, or if the main focus is on perennial or annual plants.  If intercropping techniques are used at all, they are rarely prioritized and are often discarded if they fail to meet unrealistic expectations the first time a grower tries them.

My own experience tells me that intercropping is just like any other potentially effective tool.  You need to expend a little effort on becoming proficient before you fully understand what it can do for you.  It was only when we fully embraced intercropping for our melons and watermelons that we unlocked the potential for vine crops on our own farm.

What is intercropping?

A brief, and simple, explanation is that intercropping is the intentional use of plant diversity within a growing system.  And, I offer up the example at the top of this article as exhibit A.  In that picture you will see melons surrounded by zinnias and borage.  Not easily seen in the photo are two additional types of melon, watermelons, buckwheat, calendula, and sunn hemp.  All of this diversity was fully intentional on our part - and very successful in terms of our production for the season.

A grower, whether they are a large-scale row cropper or a small-scale vegetable producer, can effectively introduce diversity several ways.  Some of that diversity can come in the form of different cash crops (crops that we intend to harvest).  In the example above, the melons and watermelons were our targeted cash crops.  The rest of the plant diversity we identified as support crops because we did not intend to harvest them.

We introduced diversity within our cash crops by growing three types of melons and two types of watermelon in this plot.  We enhanced the diversity in the field further by introducing several types of flowering crops as well as some things that are considered to be cover crops (buckwheat and sunn hemp).  The flowering crops help to support pollinator services and the cover crops help to improve soil health.

How might a grower introduce intercropping?

Every farm has different needs and different strengths, so intercropping may not be entirely the same from location to location and farm to farm.  Row crop farms could add diversity to their fields by using "strip intercropping."  I noticed a couple of farms on a recent drive that integrated corn and soybeans into the same field along with grassy terraces in some of the steeper areas.  Each cash crop strip was twice as wide as their planting equipment.  I also was pleased to see another farm who added perennial prairie strips into their fields to support pollinators and add diversity to their land.

On my own farm, we have always implemented row intercropping.  Each row or bed in our fields is intentionally paired with other rows in hopes that we can introduce positive interactions between crops.  Row intercropping keeps it simple so the increase in necessary labor is minimal.  And, the positive interactions can take many forms.  We typically have planted our carrots between our peas.  There is not a specific interaction between the plants, but we do trellis our peas.  That fencing keeps the deer out of our carrots.

I like to call it functional on-farm diversity.

Over time, we've taken our intentional diversity further by doing more with mixed intercropping (putting different plant types in the same row or bed) and relay intercropping (having two crops in different stages of development in the same bed).  This can be as simple as putting in a few flowers as crop markers to tell us when a crop variety changes to starting lettuce in the tomato rows and harvesting that lettuce as the tomatoes grow and the lettuce matures.

It seems complicated, why do it?

Research in ecology has shown us that biological systems are healthiest and most productive when there is more, not less, diversity.  So, it stands to reason that the closer we get to a single plant type for large areas of land, the less healthy it is because the natural services of the ecosystem are hindered.

But, if you need an argument from the standpoint of farm productivity, consider the natural crop insurance a farm can enjoy when it raises multiple crops.  Some years favor one crop, some years favor other crops.  A diversified cropping system is more likely to provide consistent returns from year to year without external support.  Perhaps you have heard the phrase, "don't put all of your eggs in one basket?"  That's exactly what our reliance on huge agricultural fields with one plant species is like.  It is less robust and far more likely to break when stress is put on it.

There is research that shows us that intentional diversity in cropping systems can provide natural pest control, improve soil health, decrease weed biomass, attract beneficial organisms and - believe it or not - improve overall production.

This brings me back to our cover photo for this article.  That field was a "grand experiment" for the farm that season.  We made the intentional choice to plant 33% fewer melon and watermelon plants that season and we replaced them with more support crops to increase our intentional diversity in that plot.   We were fully prepared to harvest fewer melons and watermelons as a result.  Instead, we harvested 33% more melons and watermelons than we had in prior years.  And we replicated that same thing the next year - and the year after that - and the year after that.