Cr. Camp et al., MICROIRRIGATION SCHEDULING AND TUBE PLACEMENT FOR COTTON IN THE SOUTHEASTERN COASTAL-PLAIN, Transactions of the ASAE, 36(4), 1993, pp. 1073-1078
Three irrigation scheduling methods and two microirrigation tube place
ments were evaluated on three cotton (Gossypium hirsutum L.) cultivars
for three years on a southeastern Coastal Plain soil. Irrigation sche
duling methods included two computer models, GOSSYM/COMAX and PRISM, a
nd a method using tensiometers. Microirrigation tubing was placed on t
he 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 schedu
ling methods and years, but no method consistently required the larges
t or smallest amount of irrigation. Cotton lint yields ranged from 850
to 1105 kg/ha over all years, but there were few significant differen
ces among irrigation treatments within a year, even between the rainfa
ll-only and irrigated treatments. Lint yields were significantly great
er for the PD3 and DPL90 cultivars than for the Coker 315 cultivar dur
ing the three-year period, and the PD3 cultivar had a greater yield re
sponse to irrigation. The tensiometer-every row tube placement is the
only irrigation treatment that produced cotton lint yields significant
ly higher than the rainfall-only treatment each year. The tensiometer
scheduling method also produced significantly greater yields each year
. Although yield differences occurred, they were relatively small. Thi
s fact, along with the inconsistent differences in the amount of irrig
ation water required, suggests that the preferred method for a particu
lar application will probably depend more upon water or labor requirem
ents, cost, or personal preference. Also, there was no difference in y
ield between the two tube placements. Because the alternate-furrow pla
cement requires only half as much tubing, which will reduce installati
on costs by about 30%, it appears to be the preferred placement for th
is soil. Further research is needed to refine irrigation scheduling fo
r cotton in this region.