Cotton in Ultra‐Narrow Row Spacing: Plant Density and Nitrogen Fertilizer Rates

Ultra‐narrow row spacing (UNR) of 25 cm or less may be a viable alternative to wide‐row spacing for cotton (Gossypium hirsutum L.) in the Mid‐South USA but yield and quality in relation to wide‐row cotton have been variable. Field experiments were conducted from 1997 through 2000 on Gigger silt loam (fine‐silty, mixed, thermic Typic Fragiudalfs) to: (i) determine the effects of plant density (128000, 256000, and 385000 plants ha−1) and N rate (90, 112, 134, and 157 kg ha−1) on irrigated and rain‐fed UNR cotton and (ii) compare performance of UNR cotton to wide‐row cotton (102‐cm row spacing) at a density of 116000 plants ha−1 and fertilized with 90 kg N ha−1. Increase in plant density decreased lint yield of irrigated cotton and had no effect on yield of rain‐fed cotton. Increase in plant density of irrigated cotton decreased boll number plant−1 and individual boll weight but had no effect on boll number m−2. Yield components of rain‐fed cotton were not affected by varying plant density. Increasing N rate did not affect yield or yield components of irrigated or rain‐fed cotton. Plant density, N rate, and row spacing affected fiber properties but effects were small and would not affect value or utilization. Under irrigation, UNR cotton averaged 771 kg lint ha−1 and wide‐row cotton averaged 1069 kg lint ha−1. Without irrigation, UNR cotton averaged 377 kg lint ha−1 and wide‐row cotton averaged 586 kg lint ha−1. Maximum yields of UNR cotton were attained from plant densities in the range of 128000 to 256000 ha−1 and a N rate of 90 kg ha−1