施氮量对黄河滩区棉花叶片生理特性、干物质积累及产量的影响

为探讨黄河滩地植棉适宜的施氮水平，以转双价（Bt Cry1A+CpTI）基因抗虫杂交棉品种中棉所72为试验材料，设置了N 0、 150、 300和450 kg/hm2 4个施氮水平，研究了施氮量对棉花叶片生理特性、 干物质积累及产量的影响。结果表明，随着施氮量的提高，棉花叶面积指数（LAI），叶片叶绿素和全氮含量，谷氨酰胺合成酶（GS）和超氧化物歧化酶（SOD）活性呈增加的趋势，丙二醛（MDA）含量有下降趋势，进而延缓了叶片的衰老进程。在施氮量为N 300 kg/hm2 时，棉花干物质积累量较大，且分配到生殖器官的比例较高；施氮量过低时，干物质积累量较少；施氮量过高时，有利于营养器官生长，干物质积累量最大，但分配到生殖器官的比例较低。棉花施氮量为N 300 kg/hm2时籽棉产量最高，比不施氮（N 0）和施氮量为N 150 kg/hm2的处理分别增加15.29% 和9 .77%，差异达到显著水平；与施N 450 kg/hm2的处理产量差异不显著。因此，在土壤肥力较低且下层土质沙性较强的黄河滩地，棉花的适宜施氮量为300 kg/hm2。

Effects of nitrogen application rates on main physiological characteristics of leaves, dry matter accumulation and yield of cotton cultivated in the Yellow River bottomlands

Soil in the Yellow River bottomlands is sandy and poor in fertility. To investigate the effects of nitrogen (N) application rates on main physiological characteristics of leaves, dry matter accumulation and yield of cotton cultivated in the Yellow River bottomlands, field experiments were conducted using transgenic Bt Cry1A+CpTI hybrid cotton CCRI (China Cotton Research Institute) 72 in 2010. The contents of soil organic matter, total N, available N, available phosphorous and available potassium in 0-20 cm layer are 606 g/kg, 044 g/kg, 7080 mg/kg, 927 mg/kg and 11526 mg/kg, respectively. The contents of soil particles (0002 mm, 0002-002 mm and 002-2 mm) in 0-20 cm soil layer are 12.3%, 28.0%, and 59.7%, respectively. The rates of the application of N fertilizer were 0, 150, 300, and 450 kg/hm2, respectively, and the ratio of the application of N fertilizer before the sowing, at the flowering stage and the peaking bolls setting stage was 0.4∶0.4∶0.2 .The experiments were carried out with a completely randomized design with three replications. The results show that leaf area index (LAI), the contents of chlorophyll and total N, the activities of GS and SOD in leaves of cotton are increased, and the content of MDA in leaves is decreased with the increased N fertilization which has a role in delaying senescence of leaves. The results also indicate that the N 300 kg/ha treatment is of advantage to the dry matter accumulation and distribution of reproductive organs of cotton relatively, the N 0 or 150 kg/ha treatments are of disadvantage to the dry matter accumulation, and the N 450 kg/ha treatment is of advantage to the vegetative growth and dry matter accumulation but disadvantage to the dry matter distribution of reproductive organs. The yield of seed cotton is the highest when N 300 kg/ha is applied which could increase the yield by 15.29%， 9.77% and 0.26% compared to the treatments of N 0, 150 and 450 kg/ha, respectively. Under the experimental condition of this study, we conclude that N 300 kg/ha should be applied when cotton is cultivated in Yellow River bottomlands.