The introduction of transgenic cotton (Gossypium hirsutum L.) cultivars with resistance to certain herbicides has increased the interest in ultra-narrow-row production systems. A field study was conducted on Sharkey silty clay soil (very-fine, smectitic, thermic Chromic Epiaquerts) from 1995 through 1997 to evaluate the effects of ultra-narrow-row (UNR) and conventional wide-row (CONV) production systems on plant growth and yield components. Cotton grown in 19-cm rows with 530 000 seed ha-1 and harvested with a stripper was compared with cotton grown in 97-cm rows with 155 000 seed ha-1 and harvested with a spindle picker. Percentage of first position boll retention was higher in CONV than UNR in two of three years and averaged 30% in CONV and 27% in UNR across the three years. An average of 8.5% of the second position bolls were retained with UNR compared with 15% in CONV. The UNR plants were shorter, had fewer nodes, and had fewer total sympodia than the CONV plants. The UNR plants had fewer bolls than CONV plants, with a higher percentage of the total boll number in the first sympodial position and a lower percentage in the second position. Higher seed cotton yield of UNR cotton in 1995 and 1997 appeared to result from the higher plant populations, although the findings indicated that seeding rates lower than the one used in this study could have been used for UNR. Plant populations were also higher for UNR in 1996, but the low rainfall during fruiting appeared to impact the UNR more than CONV, possibly due to the high plant density.
