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Row spacing less than 76 cm for corn ( Zea mays L.) and soybean Glycine max (L.) Merr. is becoming more common. However, little information is available on row spacing in different rotation sequences. The objective of this study was to determine the influence of rotation sequence, row spacing, and tillage system on corn and soybean yield. Corn and soybean were planted in 19‐, 38‐, and 76‐cm row spacing in conventional tillage and no‐tillage systems. Both crops were compared in seven rotation sequences. Few interactions were found between row spacing and tillage or between row spacing and rotation sequence for corn or soybean yield. Corn grain yield decreased 11% using the 19‐cm row spacing compared with the 38‐ and 76‐cm row spacings. Corn grain yield decreased 5% using the no‐tillage system compared with the conventional tillage system. Corn rotated annually with soybean and first‐year corn after 5 yr of consecutive soybean yielded 15% more than continuously grown corn. Soybean yield was not affected by row spacing. No‐tillage soybean yield was 6% higher than the conventional tillage system. First‐year soybean after 5 yr of consecutive corn yielded 8% more than the other six rotation sequences. We concluded that corn–soybean cropping history and tillage system were not important for determining optimum row‐spacing system for corn or soybean. The use of a row‐spacing system less than 76 cm was not beneficial for either crop.
Pedersen et al. (Tue,) studied this question.