Determinação da época do plantio e uso consuntivo do algodoeiro herbáceo (Gossypium hirsutum L. var. Coker 100 A) no submédio São Francisco.

Abstract

The present work was conducted in a Vertisol of the Mandacaru Experimental Station, located in Juazeiro, Bahia. The main objectives are the determination of a time and planting for herbaceous cotton that would allow the development and harvest during a rainless season and the determination of the consumptive use of the crop. The experiment used the cotton variety "Coker-100A", planted at the beginning of each month for one year. Irrigations were made when the plants had the first symptoms of wilting from 9 to 10 hours and the amount of water applied to each irrigation depended on the water content in the soil at the time the plants showed such symptoms. The analysis of the results showed that the duration of the herbaceous cotton cycle varied between 122 and 158 days, for the sowing in early September and April, respectively. Air temperature above 25 ° C and sufficient soil water contributed to the earliest cycles. Excess water in the soil during the period between fruit formation and harvest contributed to the retardation of the crop cycle. Total water consumption by cotton was 588 and 686 mm when it grew in the subsequent dry-months of the year, respectively. The consumptive use of the crop varied with the growth stage of the plant. Plantings carried out at the beginning of June, July and August presented a maximum consumptive use of 10.6 mm / day; planting carried out at the beginning of September, October and November a maximum of 7.4 mm / day and planting carried out at the beginning of each month from December to May a maximum of 6.5 mm / day. In all cases the maximum consumptive use occurred during the period between maximum flowering and fruit formation. The correction factor (K) for estimating the current herbaceous cotton evapotranspiration from the Class A tank evaporation ranged from 0.28 to 1.00 depending on the stages of the crop cycle. The yields of the plantations carried out at the beginning of July, August, November and December (2510, 2664, 2664 and 2599 Kg / ha, respectively) were significantly higher (at the 5% probability level) than the other yields obtained with the planted crop. other times of the year. Finally it is recommended as the best time for cotton planting in the area where the Experiment took place, the first days of August.