When corn grows along a field edge or a shorter neighboring crop, the outside two rows respond especially well to extra sunlight. Corn (a C4 plant, like sugarcane and pineapple) is more photosynthetically efficient than most plants (C3 plants). Soybeans have less to lose from taller neighboring corn plant shadows than do other corn plants.

Strip intercropping creates more light-saturated corn outside rows by alternating swaths of shorter crops (like soybeans, small grains, perennial grasses or specialty crops) with corn swaths. Those with variable-rate planters can boost outside-row corn populations to 60,000/acre (5 in. between plants in 20-in. rows), and scale back proportionately in rows further from the edge.

This further leverages the extra sunlight those outside rows to deliver up to 400 bu./acre corn yield in that single outside row, according to research led by Bob Recker, Cedar Valley Innovation, Waterloo, IA, in collaboration with local growers.

The second row in from the edge has responded with roughly 281-bu./acre corn yields.

Typically a grower who tries six-row-wide strips at normal populations would see outer-row-only yield equivalents of about 290 bu./acre corn, Recker says. If he bumps his outer-row population to 50,000, he should see roughly the equivalent of a 350-bu./acre yield in that outer row alone, Recker says.

Soybean yields often suffer 10-15% yield hits when grown in strips, although a number of growers featured here have overcome that, Recker says.

Ben Witte, Fairbank, IA, for example, has average bean yields in his strips of 56.7 bu. by using a proven Group 3.1 disease-tolerant, fungicide- and insecticide-treated variety, planted at 152,000/acre.