Cotton crop management under mediterranean conditions: use of water, N, Pix and plastic mulch for early production

摘要

Mediterranean conditions in the south of France that involve low temperatures and a short season limit cotton production potential. Potential duration, expressed as total degree-days (DD) (13 deg C basis) never exceeds 1400 DD, which is very low compared to most cotton production areas. Therefore, cotton production in this region requires the utilization of early season varieties and specific agronomic practices to get acceptable yields. Reported here are 1996 experimental results on the effects ofplastic mulch, water management, nitrogen fertilization (N), and Pix~(R) on phenology and blooming rate of a conventional, early-mid cotton variety (cv. DES 119-20). Twice weekly observations of blooms at the 1st position on sympodial branches allowed us to determine vertical flowering curves. Comparisons among plots for times of 1st bloom (DD), last bloom (DD) and the number of 1st position flowers per DD (slope of the curve) were accomplished by one-way analysis of variance (AOV). Compared to rain fed only plots, irrigated plots (with rainfall) significantly increased the last blooming node on the main stem, the total time (DD) elapsed to the last blooming node and the slope (i.e., rate of blooming). On irrigated plots, higher specific leaf N content due to the application of 120 kg N/ha increased the slope and significantly affected the last main stem node that bloomed in comparison with plants from unfertilized plots. Plastic mulch significantly decreased the time (DD) to 1st bloom, but had no effect on the slope and the duration of flowering. In addition to shortening the blooming, Pix~(R) drastically decreased the slope of the blooming curve while watered with irrigation and supplemental natural rainfall. An inverse relation between the slopeof the blooming curve and the time until cutout also indicates that further research should be done to optimize bloom duration and the number of fruiting sites plants establish under various conditions of water management.