Cotton Yield and Fiber Quality As Affected by Low Light

Cotton exposure to periodsofshademightdecrease yieldsandfiber quality. Thestudyaimed toevaluatetheeffect of shade at different growth stages and it’s interaction with row spacingoncotton yield andfiber quality. The experiment was carried out in Paranapanema, SP, Brazil. Treatments resulted from combinations of row spacings (0.48, 0.75 and0.96m) and7-day shade periods(pin head square – B1, first white flower – F1,one white flower at the reproductive branch 7 – F7, one boll open in the reproductive branch 3 – C3, and without shade). A shade cloth was used to reach a 50% reduction in PPFD. Leaf net photosynthesis decreased as row with decreased, and were higher on no-shade treatments during F1 and C3 stages. There was no interaction between row spacing and shading periods on cotton seed and fiber yields, boll weight, micronaire and fiber length. However, cotton grown in row spacings of 0.75m (4514 kg ha-1) and 0.48m (4296 kg ha-1) yielded more seed cotton than in 0.96m (4114kg ha-1). Shading during seven days from C3 decreased cotton yields as a result of a lower boll weight. Lint percentage was not affected by treatments and ranged from 34 to36%. The wider spacings resulted in heavier bolls and fiber yield was1466 kg ha-1, 1625 kg ha-1 and 1473 kg ha-1, at 0.48, 0.75 and 0.96 m rows, respectively. There was no effect of treatments on micronaire, however, the fiber was shorter in the smallest row spacing.