Abstract: In order to determine the most appropriate uncovering time for cotton field in northern Xinjiang，the experiment set four plastic film treatments：uncovering plastic film at 10 days before first irrigation（T10），uncovering plastic film at 1 day before first irrigation（T1），uncovering plastic film at 1 day before second irrigation（E1），and plastic film mulched in the whole growth period（CK）in 2018—2019. The effects of uncovering film on the growth and yield of cotton（Xinluzao 42）were studied by measuring agronomic trait，dry matter，yield and residual plastic film weight in cotton field. The results showed that，the water content in 0—40 cm soil layer was reduced by film uncovering treatments，and the soil moisture content was lower in earlier treatments than later treatments. At boll‑opening stage,compared with CK，the plant heights of T10 and T1 treatments were decreased by 4.4%—18.8% and 4.2%—19.7%，the numbers of main stem leaves of T10 and T1 treatments were decreased by 4.8%—16.3% and 2.7%—22.8%，the numbers of fruit branches of T10 and T1 treatments were decreased by2.8%—26.0% and 4.7%—18.0%，respectively. Compared with CK，the dry matter of boll per plant of T10 and T1 treatments decreased by 28. 0% and 11. 7% respectively（boil‑opening stage in 2018），33. 9% and 25. 8% respectively（early boll‑opening stage in 2019）. The dry matter showed little difference between E1 and CK treatments. The lint yield of E1 was significantly higher than CK with increase of 15. 1% in 2018. There was no significant difference in lint yield between E1 and CK treatments in 2019. Compared with CK，the lint yield decreased by 4.4%—23.2% in T10 and by 11.8%—17.2% in T1. The residual film amount at 0—10 cm soil layer of T10，T1 and E1 treatments decreased by 54. 6%，54. 8% and 58.6%，respectively. The uncovering treatments had no significant influence on the residual film amount at 10—20 cm soil layer and 20—30 cm soil layer.The suitable period for film mulching in cotton field was from sowing to the second irrigation in northern Xinjiang.

Key words: Cotton, Uncovering plastic film, Soil water content, Growth and development, Lint yield, Residual plastic film

摘要： 为了明确北疆棉田最合适的揭膜时间，以棉花品种新陆早42号为材料，于2018—2019年设置第1次灌溉前10 d（T10）、前1 d（T1）和第2次灌溉前1 d（E1）3个揭膜时期，以全生育期覆膜为对照（CK），测定棉花农艺性状、各器官干物质积累动态变化、产量和田间残膜量，研究不同揭膜时间对棉花生长发育及产量的影响。结果表明，揭膜降低了0~40 cm土层的土壤含水量，且揭膜时间越早，土壤含水量越低。棉花吐絮期，与CK相比，T10和T1处理棉花株高分别降低4.4%~18.8%和4.2%~19.7%，主茎叶片数分别降低4.8%~16.3%和2.7%~22.8%，果枝数分别降低2.8%~26.0%和4.7%~18.0%。T10和T1处理棉花单株铃质量分别较CK降低28.0%和11.7%（2018年盛絮期）、33.9%和25.8%（2019年初絮期），而E1处理与CK差异较小。2018年E1处理皮棉产量显著高于CK，增幅为15.1%，而2019年与CK无显著差异；T10和T1处理皮棉产量较CK分别降低4.4%~23.2%和11.8%~17.2%。T10、T1、E1处理0~10 cm土层残膜量分别较CK降低54.6%、54.8%、58.6%，而不同时间揭膜处理对10~20 cm、20~30 cm土层残膜量无显著影响。综上可知，在北疆地区，棉花地膜覆盖的适宜期为播种至第2次灌溉前。

关键词: 棉花, 揭膜, 土壤水分, 生长发育, 皮棉产量, 残膜