Effects Of Potassium Application On The Yield And Quality Formation On Different Boll Weight Cotton Varieties And Its Physiological Basis

The experiment was carried out at the experimental station of the Southern School Science and Technology Demonstration Park of Shandong Agricultural University in 2016 to2017.The field experiment was a split-plot design with three replicates.Three different boll weight cotton varieties as main plots were DP99B,L21,and J169.Two application levels of K as subplots were 0 and 240 kg/hm~2.The objectives of this study was to address the physiological mechanism of different boll weight cotton varieties and application levels of K on cotton yield formation and quality,which would provide a theoretical basis for the selection new variety with high yield and quality,and optimization of K.The main findings were as follows:1.Effect of potassium fertilizer on the growth characters of cotton with different boll weightCompared with no application of potassium,application of K after two consecutive years significantly increased the number of fruiting branches,number of fruiting nodes,and final plant height of the three varieties,and significantly reduced the shedding rate of fruits at the squaring and boll opening stages.In addition,the application of K slightly increased plant height and height of the first fruit branch.Application of potassium after two consecutive years increased plant height and the height of the first fruit branch of L21,and the height of the first fruit branch of J169.Overall,application of potassium contributes to a larger effect on the growth traits of L21 and J169 than that of DP99B.2.Effects of potassium on leaves photosynthetic and aging characteristics of cotton with different boll weightCompared with no potassium application,potassium application had an important effect on the photosynthetic characteristics of the main stem leaves during bud stage and mid-late stage.Potassium application promoted chlorophyll synthesis in the main stem leaves,increased leaf stomatal conductance,transpiration rate,and net photosynthetic rate(Pn),and improved leaf photosystem II properties to a certain extent(Wk and Vj decreased.PIabs andΨo increased)and the increase of activity of the leaves of Ru BP carboxylase and PEP carboxylase in the mid-late stages will eventually help to increase the photosynthesis of the main stem leaves of cotton and extend the functional period.Compared with the three varieties,the Pn of DP99B,L21 and J169 during bud stage increased significantly by 9.60%,19.84%and 11.85%,respectively.In the middle and later leaves,the Pn of DP99B and L21had a significant effect on the leaf age of 30 and 45 days.The growth rates of DP99B were7.75%and 11.27%,and the growth rates of L21 were 8.84%and 33.34%.The Pn of J169significantly increased by 8.53%,9.85%,and 14.62%at 30,45,and 60 days of leaf age.Potassium application has the effect of delaying senescence in middle and late cotton leaves.Potassium application increased SOD activity and decreased POD activity and MDA content in mid-late leaves.The three varieties were L21 leaves in four periods(15,30,45,and60 days of leaf age),three periods of J169(15,45,and 60 days of leaf age),and one period of DP99B(45 days of leaf age).The results showed that potassium had the best anti-aging effect on leaves of middle and late leaves of the three varieties at the age of 45 days,and the effect on L21 was better than that of J169 and DP99B.3.Effects of potassium on the dry matter accumulation of boll and the Soluble sugar and nitrogen content in corresponding leaf of cotton with different boll weightCompared with no application of potassium,potassium application reduced the content of soluble sugar in the opposing leaves of bolls,increased the content of nitrogen,promoted the accumulation of dry matter in bolls,seed cotton and fiber,reduced the rate of bell shells,and increased the fiber rate.Compared with the three varieties.Final dry matter accumulation of bolls was the highest in J169,while the highest increase rate of dry matter occurred L21.4.Effects of potassium on cotton yield and fiber quality of cotton with different boll weightCompared with no application of potassium,application of potassium significantly increased the number of summer and autumn bolls and their ratios,and increased the number of prunes to a certain extent,which significantly reduced the bolls of pre-hot.Application of potassium increased bolls number of per plant and single boll weight,thereby increasing seed cotton yield and lint yield,but had no significant effect on lint percentage.Compared with the three varieties,application of K had the largest influence on the increase of single boll weight in J169,while it had the largest effect on the increase of bolls number per plant in L21.Compared with the three varieties,the effect of continuous application of potassium on the boll number of per plant was L21>J169>DP99B;the effect of continuous application of potassium on single boll weight was J169>DP99B>L21.The effect of continuous application of seed cotton yield and lint yield was J169>L21>DP99B.Potassium fertilization had no significant effect on the fiber quality of the three varieties,and there was no significant difference between the three varieties.