Study On The Cause Of Cotton Seedlings Death In Xinjiang And Corresponding Control Measures

Xinjiang is the main cotton production base of china. In spring, the climate is complex and multivariable, strong cold air usually occurs repeatedly and causes cotton seedling dead in large area, sometimes even over-sowing. There exist various explain for these phenomena, such as cotton seedling disease, drug injury of herbicide, varieties discrepancy, the improper usage of seed coating and so on, so it is necessary to study the reasons of cotton seedling death and make foundation for cotton production.Based on the experimental results in pot and field, it was found that the cotton variety to Rhizoctonia solani and chilling was significantly different, and there was a distinct coherent in resistance of the cotton varieties to Rhizoctonia solani and chilling. Xinluzao No.10, Xia 9 and 150-1 to Rhizoctonia solani and chilling were most susceptible, if these varieties were sowed early, they would be attacked by continuous low temperature and often resulted in sprouts or seed rot, even seedling dead. But the cotton varieties of "CCRI36", Xinluzao No.13, and Xi9 had high-level resistance to Rhizoctonia solani and chilling. So, the cotton varieties of higher resistance could be sowed a little earlier, while the lower resistance could be sowed later.In addition to Rhizoctonia solani and low temperature could cause cotton seed rot and seedling death, it was found herbicide could also cause cotton seed rot and seedling death, and the effect was most related to the herbicide-Acetochlor dosage, the depth, soil humidity, soil temperature, and soil character. The depth of herbicide in soil was critical for weed control. Spraying Acetochlor on the soil surface had good controlling effect and cause less drug injury. But when the soil layer including Acetochlor was near cotton seed, the drug injury occurred usually. So in field we should sow or harrow after spraying herbicide in soil surface. Recent years in Xinjiang, the cultivation methods were changed greatly such as sowing on the mulching film, seedling with dewing. These reforms had close relations to soil humidity. So, in order to avoid herbicide injury, a lower dosage should be applied for drop irrigation field, the fields with lower water level or the sandy soil.Recently, the seed coating of Fu Duojia and WeiFu were wide applied in the north of Xinjiang. Based on seed germination test, inoculation test and control test in the field, it was showed FuDuojia and WeiFu had not bad effect on the seedling and budding germination percent, but even could increase seedling germination to 10% usually. Mixed Fu Duojia and WeiFu with 3911 reduced the seedling germination compared with that of using Fu Duojia and WeiFu singly, but increased compared with that of using DiKesong. Fu Duojia is superior to the WeiFu on the control of the seedling disease. WeiFu had a good effect on the control of seeds rot, but the effect to cotton seedling damping-off was less than Fu Duojia. At present, in north of Xinjiang, we firstly suggested to use FuDuojia for seed coating. Furthmore, we found out there were more seed sprouted-later in spring of 2004 than ever, after investigation it was found that the phenomena had no relation to seed coating. The main reasons were related with cotton seed maturity and low-temperature in fall of 2003.