COTTON YIELD, YIELD COMPONENTS AND FIBER QUALITY IN RELATION TO NITROGEN DOSAGE AND PLANT DENSITY

Abstract

Mexican cotton (Gossypium hirsutum L.) varieties are earlier and have smaller size than the foreign varieties commonly grown. Because
of their plant structure, Mexican varieties may require higher plant densities and a different nitrogen (N) fertilization rate, than those
required for late varieties. In this work it was determined the response of Laguna 89 to N fertilization and plant density. In a narrow
row production system (rows 0.70 m apart), six N rates: 0, 40, 80, 120 (commercial control), 160 and 200 kg ha^-1, and four plant densities; 70 000 (commercial control), 82 500, 95 000 and 108 000 plants/ha, were studied during 1997 and 1998 Seed and lint cotton yields, first pick precocity, yield components and fiber quality were measured. The variables evaluated showed differences among years, but the interactions year x N or year x plant density were not significant. No significant effects on lint yield and precocity were found among N rates and plant densities, neither for their interaction. However, N at 0, 40, 120 and 160 kg ha^-1 showed the highest fiber percentages, and high N levels increased seed index and fiber resistance. As density increased, the plant yield and number of bolls per plant decreased. Plant density affected fiber strength and fineness but not fiber length. Highest fiber strength was obtained at 82 500 and 95 000 plants/ha, and at high densities there was a thicker fiber.