Response of cotton to nitrogen fertilization and early multiple applications of mepiquat chloride∗

Approved for publication by the Director of the Arkansas Agricultural Experiment Station.

Abstract

Studies were conducted for three years to determine the effects of early multiple applications of mepiquat chloride (MC) on field‐grown cotton (Gossypium hirsutum L.) fertilized with high rates of soil‐applied urea‐N (134, 168, and 202 kg N/ha). Foliar treatments of 0, 0.006, and 0.012 kg MC/ha in combination with 0 and 0.22 kg B/ha were applied when the cotton reached the first square stage. Applications were continued on a seven‐day schedule for three additional weeks. Significant differences in lint yield, percent first harvest (PFH) and final plant height were observed as a function of the N rate‐MC‐B treatment combinations. Plant heights were reduced by the MC applications, especially the 0.012 kg/ha rate. Tallest plants were found in plots treated with the two highest N rates (202 and 168 kg N/ha) without any foliar treatment. Petiole NO3‐ analysis indicated that the greater N rates resulted in greater N uptake by the plants. Lint yield was suppressed by the 0.012 kg MC/ha treatments at all N rates. Maximum lint yields were attained in plots fertilized with 134 kg N/ha that received foliar treatments of 0.22 kg B/ha and 0 kg MC/ha. The PFH was significantly affected by the treatments two of three years, but the means were tightly grouped.

Notes

Approved for publication by the Director of the Arkansas Agricultural Experiment Station.