|
Résumé :
|
Three irrigation scheduling methods and two microirrigation tube placements were evaluated on three cotton (Gossypium hirsutum L.) cultivars for three years on a southeastern Coastal Plain soil. Irrigation scheduling methods included two computer models, GOSSYM/COMAX and PRISM, and a method using tensiometers. Microirrigation tibing was placed on the soil surface, either adjacent to every row or in alternate furrows. Growing-season rainfall amounts ranged from 313 mm in 1990 to 544 mm in 1988. Rainfall distribution also varied widely within each year. In a similar manner, irrigation amount and frequency varied among scheduling methods and years, but no method consistently required the largest or smallest amount of irrigation. Cotton lint yields ranged from 850 to 1105 kg/ha over all years, but there were few significant differences among irrigation treatments within a year, even between the rainfall-only and irrigated treatments. Lint yields were significantly greater for the PD3 and DPL90 cultivars than for the Coker 315 cultivar during the three-year period, and the PD3 cultivar had a greater yield response to irrigation. The tensiometerevery row tube placement is the only irrigation treatment that produced cotton lint yields significantly higher than the rainfall-only treatment each year. The tensiometer scheduling method also produced significantly greater yields each year. Although yield differences occured, they were relatively small. This fact, along with the inconsistent differences in the amount of irrigation water required, suggests that the preferred method for a particular application will probably depend more upon water or labor requirements, cost, or personal preference. Also, there was no difference in yield between the two tube placements. Because the alternate-furrow placements requires only half as much tubing, which will reduce installation costs by about 30%, it appears to be the preferred placement for this soil. Further research is needed to refine irrigation scheduling for cotton in this region.
|
