Productivity and profitability of strip intercropping systems as implemented by agronomists and farmers
On-station experiments investigated whether three-crop strips produced net gains in yield and profit and examined different crop rotations in strips for profitability, border interactions, and fertilizer nitrogen requirements. The sites were the Northeast Research Station (NERC), at Nashua, Iowa, and Living History Farms (LHF), near Des Moines. A corn-soybean rotation was compared to three-year crop rotations that included a sole-seeded forage legume or a forage legume established with a small grains nurse crop;For three years, six cooperating farmers recorded yields and kept Iowa State University Crop Enterprise Records (CER) for strip intercropping and for single-crop blocks. Four compared three-crop intercropping to the same three-crop rotations in sole-crop blocks ("planting pattern"), while two producers compared three-crop strips to the corn-soybean rotation in sole-crop blocks ("system comparison"). Labor requirements were similar in strips and field blocks (planting pattern) to 22 percent less in intercropping (system comparison). Profit averaged 3.80 per acre greater (planting pattern) and 14.76 per acre greater (system comparison) in strips than field blocks. There was a tendency for risk reduction in strip intercropping;Three-crop rotations on the experiment stations performed comparably to corn-soybeans, although drought reduced yields. At NERC, corn at strip borders yielded more than corn in strip interiors. At LHF the reverse was true. There was no significant difference between yields at the east and west borders. Corn yields at both sites were less next to soybeans than other crops;In two site-years drought prevented significant yield response to nitrogen. Corn grain nitrogen concentration consistently responded to nitrogen fertilizer and occasionally to crop rotation. Soybean yields were reduced at strip borders. There was a tendency for lower soybean yields next to corn than other crops;Grain and straw yields of small grains were not significantly different by position. Hay harvests averaged slightly less at strip borders; however, at first hay cutting east borders yielded more than strip centers;There is a place for extended crop rotations and strip intercropping systems that incorporate them. Prerequisites include adequate management and cost-effective uses for crops in the rotation third year.