Rotational effects of cuphea on corn, spring wheat, and soybean
Diversifying crop rotations can give economic and environmental benefits. Cuphea (Cuphea viscosissima Jacq. x C. lanceolata W.T. Aiton) is a new oilseed crop that grows well in the Corn Belt. However, little is known about its rotational effect on corn (Zea mays L.), soybean [Glycine max (L.) Merr.], and spring wheat (Triticum aestivum L.), which are predominant crops in this region. A 4-yr study conducted in Minnesota evaluated the previous crop effects of all 2-yr rotational sequences of cuphea with corn, soybean, and wheat on crop yields and stands, soil water and N content, and production economics. Cuphea seed yield was unaffected by previous crop and yields of the other crops were unaffected by cuphea. Wheat stand was 17% greater and grain crude protein content 8% greater when following cuphea than following corn or soybean. This response was attributed to nitrate N remaining after cuphea harvest. Cuphea slightly negatively influenced soybean stands, but this was not reflected in yield. Cuphea production cost averaged $172 ha–1 less than corn and $118 and $126 ha–1 higher than soybean and wheat, respectively. While cuphea was not profitable at a price less than $1830 Mg–1, it could provide rotational benefits, with net returns for corn and soybean following cuphea comparable to other non-monoculture sequences and higher than when grown continuously. However, the economic viability of including cuphea in rotation will be limited until the cuphea phase of the rotation can also be produced profitably. Cuphea agronomically fits in rotation with corn, soybean, or wheat, but may be best after soybean and before wheat or corn.