Cotton growth and development are determined and influenced by cultivars, meteorological conditions, and management practices.  The objective of this study was to quantify the optimum of temperature-light meteorological factors for seedcotton biomass per boll with respect to boll positions.  Field experiments were conducted using two cultivars of Kemian 1 and Sumian 15 with three planting dates of 25 April (mean daily temperature (MDT) was 28.0 and 25.4°C in 2010 and 2011, respectively), 25 May (MDT was 22.5 and 21.2°C in 2010 and 2011, respectively), and 10 Jun (MDT was 18.7 and 17.9°C in 2010 and 2011, respectively), and under three shading levels (crop relative light rates (CRLR) were 100, 80, and 60%) during 2010 and 2011 cotton boll development period (from anthesis to boll open stages).  The main meteorological factors (temperature and light) affected seedcotton biomass per boll differently among different boll positions and cultivars.  Mean daily radiation (MDR) affected seedcotton biomass per boll at all boll positions, except fruiting branch 2 (FB2)  fruting node 1 (FN1).  However, its influence was less than temperature factors, especially growing degree-days (GDD).  Optimum mean daily maximum temperature (MDTmax) for seedcotton biomass per boll at FB11FN3 was 29.9–32.4°C, and the optimum MDR at aforementioned position was 15.8–17.5 MJ m^–2.  Definitely, these results can contribute to future cultural practices such as rational cultivars choice and distribution, simplifying field managements and mechanization to acquire more efficient and economical cotton management.

cotton (Gossypium hirsutum L.) ,  temperature-light meteorological factors ,  seedcotton biomass per boll ,  boll positions