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Comparison of Cotton Genotypes Varying in Canopy Characteristics in 76-cm vs. 102-cm Rows

USDA-ARS, Cotton Physiology and Genetics, P. O. Box 345, Stoneville, MS, 38776

J. Ray Williford

USDA-ARS, Application and Production Technology, P.O. Box 36, Stoneville, MS.

^* Corresponding author (jheithol{at}ag.gov).

Our previous findings with cotton (Gossypium hirsutum L.) indicated that a leaf shape variant with reduced leaf area (okra-leaf) yielded more in 51-cm rows than in 102-cm rows. Yield of a normal-leaf type was unaffected. The objectives of this study were to determine whether this same response would occur with genotypes varying in canopy characteristics when grown in rows spaced 76 and 102 cm. From 1991 to 1993, seven to 14 genotypes (including two okra-leaf and one ultra-short season type) were grown in the field in 76- and 102-cm row spacings. The 1991 part of the study encompassed four soil types and the 1992 and 1993 study was grown on a Bosket fine sandy loam. Irrigation was provided when necessary to minimize water stress. The percentage of photosynthetic photon flux density (PPFD) intercepted and yield were determined. The 76-cm row spacing intercepted significantly more PPFD than 102-cm rows up until 80 d after planting. Row spacing did not affect yield in either an excellent environment (1991, 1475 kg ha^–1) or in a stressed environment (1993, 905 kg ha^–1). However, 76-cm rows outyielded 102-cm rows by 15% in 1992 (1280 vs. 1100 kg ha^–1). For each year, the genotype x row-spacing interaction was not significant. However, the combined analysis (1992, 1993) indicated that the P > F for the genotype x row-spacing interaction was 0.12. This was due to a trend for the cultivars to respond to 76-cm rows (9% increase) whereas the okra-leaf types did not respond to 76-cm rows. Despite genetic differences in morphology and canopy architecture, genotype x row-spacing interactions may not be important when comparing 76- and 102-cm rows in some U.S. Mid-South environments.

Received for publication May 30, 1995.