[Regulation effect of water and nitrogen on cotton biomass and yield under different drip irrigation patterns]

Three levels (low, medium, and high) of irrigation amount and nitrogen application rate were installed in a field experiment to study the regulation effect of water and nitrogen on the cotton biomass and yield under different drip irrigation patterns. Under the irrigation patterns 1 lateral 4 rows, 2 laterals 4 rows, and 2 laterals 6 rows, when the irrigation amount increased from low (90, 140, and 140 mm) to medium level (150, 200, and 200 mm), the aboveground dry biomass was increased by 9.2%, 37.9%, and 23.5%, and the seed yield was increased by 19.1%, 14.1%, and 16.0%, respectively. When the irrigation amount increased from medium to high level (210, 260, and 260 mm), the aboveground dry biomass was increased by 15.8%, 19.1%, and 16.7%, and the seed yield was increased by 7.7%, 11.2%, and 9.5%, respectively. When the nitrogen application rate changed from low (67.6 kg x hm(-2)) to medium level (95.2 kg x hm(-2)) the aboveground dry biomass under irrigation pattern 2 laterals 4 rows was increased by 14.3%, the seed yield under irrigation pattern 1 lateral 4 rows was increased by 22. 2% , while these two parameters under other irrigation patterns had no significant change. When the nitrogen application rate changed from medium to high level (122.8 kg x hm(-2)), the seed yield under the irrigation patterns 1 lateral 4 rows, 2 laterals 4 rows, and 2 laterals 6 rows was increased by 7.4%, 13.9%, and 9.9%, respectively, but the aboveground dry biomass had no significant change. Comparing with that under the irrigation patterns 1 lateral 4 rows and 2 laterals 6 rows, the regulation effect of water and nitrogen on the aboveground dry biomass and seed yield under irrigation pattern 2 laterals 4 rows was more apparent. As for the same water and nitrogen treatments, the aboveground dry biomass and seed yield were higher under the irrigation pattern 2 laterals 4 rows, suggesting that this drip irrigation pattern was most appropriate to the water- and nitrogen management of cotton field.