Abstract:

To investigate the effects of DPC on agronomic traits, dry matter accumulation, yield, and fiber quality of direct-seeded cotton following garlic in southwest Shandong, and to determine the appropriate growth regulator timing and dosage, a field experiment with single factor randomized block design was conducted in 2024 using the short-season cotton variety ‘Lumian 551’. Three treatments were designed and DPC was applied at the squaring, initial flowering, full flowering, and 7 days after topping stages, respectively. The spraying dosages were T1: 0, 0, 75.0, 105.0 g/hm²; T2: 0, 45.0, 60.0, 75.0 g/hm²; T3: 15.0, 30.0, 60.0, 75.0 g/hm², with water serving as the control (CK). Results showed that, under an equal total DPC dosage across the growth period, earlier and more frequent DPC applications significantly reduced plant height, increased boll number per plant and single boll weight, and ultimately improved lint yield. The lint yield followed the order T3>T2> T1 > CK, with T3 increasing yield by 3.8%, 12.5%, and 30.8% compared with T2, T1, and CK, respectively. DPC application also enhanced dry matter accumulation in roots and fruiting branches, while reducing that in vegetative branches. However, no significant differences were observed in fiber quality among treatments. Overall, the T3 treatment (15.0 g/hm² at squaring, 30.0 g/hm² at initial flowering, 60.0 g/hm² at full flowering, and 75.0 g/hm² 7 days after topping) exhibited the best yield and agronomic performance, suggesting it as the optimal DPC application strategy for direct-seeded cotton after garlic in southwest Shandong.

Key words: southwest Shandong region, direct-seeded cotton after garlic, DPC, dry matter, yield, fiber quality