| What are the characteristics of cotton yield,fiber quality and boll temporal distribution under summer direct seeding conditions in the Yangtze River Basin?The experiment was conducted on the farm of Huazhong Agricultural University in 2019and 2020.A random block design was used with 2 early-maturing cultivars（Z425 and Z619）and 3 mid-early maturing cultivars（JH116,ZD2040 and HM3097）.Under late sowing（late May）,high density(8 plants/m-2),reduced nitrogen fertilizer(N 150kg·hm-2)and fertilization once when flowering conditions,the development of cotton reproductive organs was recorded every 3 days using the plant mapping,and parameters were studied such as cotton growth,agronomic traits,yield and its components,fiber quality,and canopy light distribution and so on in order to explain the temporal specificity of summer direct seeding cotton yield formation.The result shows:1.In 2019,cotton average growth period of five cotton cultivars was 88 days,including 30 days at the seedling period,23 days at the squaring period,and 35 days at boll setting period.There was no difference in the growth period between cultivars.The first branch average node is 6.8 nodes,and the first branch node of early maturing cultivars is lower than mid-early maturing cultivars.In 2020,due to the increase of precipitation in July and the low temperature in October,cotton growth period was extended by 30 days,and the plant height,the first branch node and the main stem leaves all increased.2.In 2019,the peak period of squaring was 43.8 to 63.4 days after emergence（July11 to 30）,and the peak period of flowering was 62.6 to 81.9 days after emergence（July29 to August 18）.The peak period of open boll setting was from 91.8 to 117.7 days after emergence（August 28 to September 23）.In addition,the reproductive organs of early-maturing cultivars entered rapid growth period earlier than that of mid-early-maturing cultivars.In 2020,the rapid growth period of buds,flowers and open bolls was delayed by 20 d,17 d and 34 d respectively,and the cumulative number of reproductive organs also decreased.3.The biomass increased gradually with the growth stage,and the source and flow biomass decreased after boll opening stage.The plant biomass of mid-early-maturing cultivar HM3097 was higher,while that of early-maturing cultivar was lower.In 2019,the rapid accumulation period of sink biomass was 73.1～105.4 days after emergence（August 9 to September 10）,and the rapid accumulation period of the plant biomass was 57.6～86.1 days after emergence（July 25 to August 22）.In 2020,the source biomass decreased,and the sink biomass increased,and the beginning of the rapid accumulation period was delayed by 10 days.4.In 2019,the average seed cotton yield of five cotton cultivars reached 2551.22kg·hm-2,and the average lint yield was 1038.60 kg·hm-2.The mid-early maturing cultivar HM3097 had the highest lint yield and seed cotton yield,mainly because its boll weight and lint were higher than other cultivars.In 2020,cotton yield was lower and there were no differences between cultivars.On the whole,HM3097 has better yield performance.Cotton fiber length and fiber elongation were higher in upper fruit branches than in middle and lower fruit branches,cotton fiber strength was higher in middle and upper fruit branches than in lower fruit branches,while fiber uniformity was higher in upper fruit branches than in middle and lower fruit branches.The fiber length,fiber strength,fiber uniformity and elongation of ZD2040 are better than other cultivars,and the best micronaire values are JH116 and ZD2040.In conclusion,under summer direct seeding conditions,cotton growth period was shortened,and the bolls were mainly composed of late summer bolls and early autumn bolls.The mid-early-maturing cultivar HM3097 has more reasonable plant types,boll setting characteristics and dry matter accumulation and distribution,so its yield is higher.JH116 and ZD2040 have unstable yields,but their fiber quality is better.In addition,the plant types and canopy structures of early-maturing cultivar were unsuitable,thus cotton yield and fiber quality perform poorly in this mode. |
