Intercropping Systems For Small Scale Vegetable Production

We learned that all of the methods we trialed can work. Of the three combinations the Winter Squash/Garlic planting had the highest return. Not factoring in long-term costs like land/infrastructure/insurance, etc. we estimated a net hourly wage of $83.95 per hour for this combination. The Broccoli/lettuce planting netted an hourly wage of $68.85, and the Sweet Potatoes/Onion combination netted an hourly wage of $40.90. See SARE Intercropping Trials for these calculations. The Winter Squash/Garlic combo had the highest sales value, the least annual costs, and required little labor. Conversely, the Sweet Potato/Onions combination had high annual costs because the Sweet Potato slips are expensive, and we start our onions from seed in the greenhouse and starting that many plants proved timely and expensive. In addition, the labor to harvest both the onions and the sweet potatoes was substantive. Still, for a CSA farm it makes sense to grow all three of these combos and we find that running a CSA is greatly helped by having these storage crops to buffer fresh greens and fruits that do not have store-ability. In particular, our winter shares greatly benefit from having Sweet Potatoes, Winter Squash, Onions and Garlic in storage. Also note that the numbers given were estimates based on going to Market. We did not actually go to market, all of this product was distributed through our CSA. Market farms would likely have issues moving this much product via a Farmer's Market.   

Here is why we chose to intercrop:

• It creates higher yields by using all available space.
• There are fewer weeds because all available space is always being used.
• It may reduce insect pressure.
• Gives shading advantages to cool crops.
• It is beautiful. 
• It is fun.

Here are some of the guiding principles we used:

1. Intercropping needs really good soil. I think the soil should test at over 5% organic matter. I would argue this organic matter should come from plant based compost. At least 3 inches of plant based compost to begin, an inch each year after for three years. Amend with custom mix and fish as needed. 
2. If your soil is right the only limitation is the sun. Try to use all available sunlight at all times.
3. Plants grow in circles not squares! So use staggered planting patterns. (Think like a pixel printer not like an 8 bit Atari).
4. Keep heavy feeders (Brassicas especially) in the center of inter-cropped beds and light feeders like lettuce on the outside.
5. Place longer season crops in the center and short season crops on the outside.
6. Experiment and have fun. Discover what combinations work for you.

Here is what we learned from the garlic/winter squash trial and the onion/sweet potatoes trial. We chose these combinations because:

1. All four crops are difficult to manage weeds with. Onions/Garlic because they are weakly rooted. Sweet Potatoes and Winter Squash because they vine out.
2. We wanted to use landscape fabric with vining crops, but fabric is expensive and labor intensive so we wanted a higher return on this investment.
3. Sweet Potatoes and Winter Squash take up a lot of space.
4. By intercropping these 4 crops we get a higher return on material and labor costs while maximizing space.

We were very successful in the garlic/winter squash planting.

What we did:

1. We planted the garlic the previous season. It is best to plant the garlic in October so that the bulbs root, some of our garlic that got planted in November somewhat heaved. In our second season Garlic was planted in October and we had no heaving.
2. Spacing: 32in. bed tops. 4½ ft. wide with pathway.
3. Winter Squash spaced at 12in. apart down the center of the bed, slightly offset.
4. Outer edges of the bed spaced at 6in. apart (see image in attached powerpoint presentation).
5. We burned holes in the fabric with a template using a plumbing torch. Can do multiple sheets at a time. We used 15ft. wide rolls to make sheets to cover 3 beds together. The fabric should be ground cover (smooth on both sides).
6. Use fabric staples to secure the fabric (about 6ft. apart). Reused staples are better because as they corrode and rust they grab the soil better. A staple setter (magnet on the end of a 3ft. handle) is a worthy investment.
7. Drip irrigation should be set up under the fabric.
8. We transplanted winter squash on June 28. The later the better so you give the garlic the time it needs. We used a 90 day Butternut variety (Waldo) to ensure that the squash would finish with a late planting.
9. Harvest the garlic after the tops begin to brown but before the whole top browns. This lets you easily pull up the garlic at harvest, otherwise tops can tear off and the garlic is difficult to harvest because you can't use a fork to lift the garlic because of the fabric.
10. We hand weeded weeds that emerged through the holes two-three times. Because the fabric controls the majority of the weeds this is a fairly quick task as long as it is done early.     
11. We had a strong harvest of both crops.

Onions/Sweet Potatoes:

This planting is very similar to the above planting. We used the exact same fabric and template spacing. Onions were planted in mid-April and the Sweet Potatoes after the risk of frost. We had a great onion crop. Onions were very large. In 2019, we missed an important second/third hand weeding though. As a result, we had a surge in tall grass that grew up and around the onions. We couldn't weed this because we did not want to disrupt the onions, but the tall grass shaded the sweet potatoes and lowered our sweet potato yields. After we harvested the onions we cleared the field of weeds and the sweet potatoes rebounded, but our short Michigan summers require the sweet potatoes to have full access to the sun through the whole growing season. In 2020, we made sure we did a very clean hand weeding the third time. This kept our field clean the whole season and harvesting for all crops much easier and we had a sizable sweet potato harvest. Our only issue was that many of the sweet potatoes had splits. We don't know if this was related to the intercropping, or the variety used. We observed that Beauregard had more firsts than Georgia Jet. We still weren't that pleased and will trial Covington in 2021. Several farmers on tours affirmed this as the best variety for quality sweet potatoes in Michigan.

Challenges:

We had some staff changes mid-season so we were unable to properly account for yields, labor and return on investment in 2019. We were able to track this data in 2020. 2020 had it own sets of challenges that need not be named. We survived though and had a good growing season.