Strip Intercropping
Strip intercropping involves multiple crops growing in side-by-side, narrow strips. There is a potential “biological efficiency” built into narrow strips. It has to do with the borders between the strips. That is where neighboring crops can use resources like light, fertility, and soil moisture in complementary ways. Properly managed strip intercropping improves both overall crop yields and soil conservation. This does not automatically occur, but crops that use these resources at different times of the season often make good neighbors in strip intercropping. Oats, for instance, are harvested in July, leaving extra resources for neighboring row crops. Corn and soybeans are potentially competitive. University and farmer researchers have seen that in stress years, the yield benefits of strip intercropping are less evident, as competition between crops dominates over the complementary use of resources.
Strip intercropping is a complex system requiring careful management. Ridge-till farmers have so far had the greatest success with this system. Strip placement and strip “drift” are largely overcome by the use of permanent rows in ridge tillage. Over a three year period, six cooperators compared three-crop strip intercropping to cropping in sole-crop blocks, recording crop yields and labor, and keeping ISU Crop Enterprise Records. The figure above shows net profits per acre in strips and conventional cropping for these 18 site-years. Corn yields were usually higher in strip intercropping, because corn on the borders of strips received extra sunlight. Soybean yields were not materially reduced by strip intercropping, probably because soybeans made use of extra resources after harvest of neighboring small grains. Strip intercropping was the more profitable system two years out of the three. In these trials strip intercropping tended to reduce the likelihood of low overall financial returns (risk reduction).
For a more extensive discussion of this strip intercropping research, see:
Exner, D.N., D.G. Davidson, M. Ghaffarzadeh, and R.M. Cruse. 1999. Yields
and returns from strip intercropping on six Iowa farms. American Journal of
Alternative Agriculture 14(2):69-77.