Li Shutian, Xing Suli, Cui Rongzong, Zhang Yan
To determine the soil potassium status and supply capacity as well as their relation to cotton yield and quality in major cotton areas in north China, surface soil (0-20 cm), cotton plant and lint samples were collected and analyzed from representative cotton fields in Pingyuan County of Shandong Province, Weixian County of Hebei Province and Changji City of Xinjiang Province in 2012 and 2013. In Pingyuan County, more than 50% of the soil samples had 100-200 mg· kg－1 soil available K and 23% of samples had more than 300 mg·kg－1, with an average of 217 mg·kg－1. In Weixian County, 53% of soil samples had 100-150 mg·kg－1 soil available K and 22% of samples had less than 100 mg·kg－1, with a mean of 128 mg·kg－1. In Changji, more than 2/3 of samples had soil available K of 150-300 mg·kg－1 and 25% of samples had more than 300 mg·kg－1, with an average of 232 mg·kg－1. The soil K supply capacity, represented by uptake K of aboveground organs, was 120-140 kg·hm－2 in 68% of sites with a mean of 128.2 kg·hm－2 in Pingyuan County, 80-120 kg·hm－2 in 65% of sites with a mean of 105.1 kg·hm－2 in Weixian County, and 150-300 kg·hm－2 in 92% of sites with an average of 213.6 kg·hm－2 in Changji City. The average K uptake by aboveground organs required to produce 100 kg of lint cotton was 9.77, 7.82 and 12.25 kg, respectively, in Pingyuan County, Weixian County and Changji City. In Pingyuan County, significant positive correlations existed between soil available K and lint cotton yield, plant K uptake when the soil available K was less than 123 mg·kg－1. In Weixian County, there were no significant correlations between soil available K and lint cotton yield, plant K uptake. In Changji, significant positive correlations existed between soil available K and lint cotton yield, plant K uptake when the soil available K was less than 220 mg·kg－1. The correlations between plant K uptake and cotton yield varied by location, but there were significant positive correlations between lint K uptake and cotton yield in all three sites. There were great variations in the relationships between plant K uptake, lint K uptake, lint K content and fiber quality indices in different locations.
