By: Jose G. Franco and Joseph G. Masabni
Home gardeners and small-scale farmers can increase their properties’ productivity by intercropping—growing two or more crops together on the same plot—using species that perform specific functions to benefit their companion crop (Fig. 1).
In a 2-year study, researchers with Texas A&M University and the Texas A&M AgriLife Extension Service planted five vegetable species: okra, peanuts, peas, peppers, and watermelon. Each species was grown separately in different plots (monoculture) as well as intercropped with other species.
The vegetables were intercropped to take advantage of each species’ natural benefits to the other crops (Table 1):
- Peanuts and peas fix nitrogen from the air and supply it in the soil as nitrates to other plants.
- Watermelons shade the soil and suppress weeds.
- Okra also provides shade, and its flowers attract pollinators.
- Hot peppers provide a barrier to pests.
Two types of intercropping were used: row intercropping, in which a row of one crop was alternated with a row of another crop (Fig. 2); and mixed intercropping, in which plants of different species were alternated within each row (Fig. 3).
The species combinations and intercropping systems included:
- Peanuts and watermelon, mixed intercrop
- Peanuts and watermelon, row intercrop
- Okra, peanuts, and watermelon, mixed
- Okra, peanuts, peas, and watermelon, mixed
- Okra, peanuts, peas, peppers, and watermelon, mixed
Individual plants of all species were spaced about 12 inches (30 cm) apart, arranged so that each plant was neighbored by a legume species and another species.
The researchers weighed the vegetables harvested and calculated the yields per plant and per land unit area. They then compared the yields from species planted monoculture and those intercropped.
Planting three or four species together consistently yielded more per land unit than did those crops grown alone (Fig. 4):
- Four of the five intercropping combinations produced more pounds per land unit than did those crops planted monoculture in Year 1.
- Three of the five intercropping combinations produced more pounds per land unit than did those crops planted monoculture in Year 2.
- Watermelon yields benefited most from intercropping in Year 1.
- Okra and peanut yields benefited most in the second year.
However, peppers and peas produced less than expected both years, regardless of intercropping combination. Yield from the other crops varied in production by treatment and by year (Table 2).
The researchers planted the crops on different dates to prevent the fast-growing species from crowding out those that grow more slowly. The pepper plants were transplanted into the garden at 3 inches tall; for other crops, seeds were planted directly in the ground (direct seeded) where they would mature.
- August 1: Peanuts
- August 7: Watermelon
- August 14 and 15: Okra and peas
- August 18: Peppers Year 2:
- June 21 and 22: Peanuts and okra
- June 27: Peas
- July 3: Peppers
- July 12: Watermelon
Conclusion and considerations
Texas A&M researchers showed that intercropping three or four crops produced the most on a per-landunit basis, despite changes in relative planting dates between the 2 years.
Vegetable producers and home gardeners thinking about practicing this type of intercropping should keep in mind the growth rates and competitive nature of the crops they choose, and select planting dates based on this information.
For example, because peanuts grow more slowly than do watermelons, growers should plant peanuts first and give them time to emerge before planting watermelons.
Another guide to determining relative planting dates is to choose which crop’s production to maximize the most. If you want to maximize watermelon production, plant it earlier than the other component crops.
Those wishing to intercrop should also leave enough space between plants to avoid overcrowding but not so much that the plants cannot benefit each other. A good way to determine how to close to plant species of different spacing requirements is to use the average recommended plant spacing of all of the crops used.
With this strategy, you may plant some crops slightly closer than recommended and other crops with slightly farther apart. However, most should fall within an acceptable range.
Other options are to use companion crops that have similar spacing requirements to avoid overcrowding or to select varieties that tolerate tight spacing. For instance, the study used a mini watermelon variety because it required half the spacing of a standard sized watermelon—1.5 feet versus 3 feet apart.
Intercropping diverse species where each performs a specific function in the garden can lead to overall yield increases per unit area and per plant. This technique can enable home gardeners and vegetable producers with limited space to maximize the overall productivity of their land.
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