Absorption,accumulation and distribution of potassium in super highly-yielding winter wheat

In order to clarify the characteristics of potassium nutrition in super highly-yielding(≥ 9000 kg/ha) winter wheat,and to provide experimental basis for potassium application,field experiments were conducted in Gaocheng County,Hebei Province from 2004 to 2006.Four winter wheat cultivars,Shimai14,Shimai12,Jifeng703 and Shixin828 during 2004-2005,and four cultivars,Temai1,Shimai12,Shixin531 and Shixin828 during 2005-2006,were used as experimental cultivars.Plant samples were collected from the plots at different growth stages and used to determine potassium concentration in laboratory.The results show that the concentrations of potassium(K2O) in various above-ground organs of wheat are from 0.21% to 3.84%(dry weight) during the whole growing period.For the above-ground organs,the highest concentrations of potassium appear as early as they formed or at their early period of life,then the concentrations of potassium decrease until the maturity.The organs with the highest concentration of potassium succeed with the turnover of growth center at various growth stages.Before the anthesis,the accumulation amount and distribution percentage of potassium in leaf blades are the highest among all organs,and the distribution percentage of potassium in leaf blades can reach to 50% or higher before the jointing.After the anthesis,however,the accumulation amount and distribution percentage of potassium in stems are the highest,and the distribution percentage of potassium in stems are from 35.6%-45.3% at the maturity.The concentrations of potassium in various organs and the total accumulation amounts of potassium during the growing period for different wheat cultivars in a growing year are different,but usually insignificant,which indicate similar characteristics of potassium nutrition for different cultivars with the yield ≥ 9000 kg/ha.The total accumulation amount of potassium in wheat plants reaches the highest value 181.7-230.7 kg/ha at the anthesis.The amount of potassium required for the formation of 100 kg grain is from 2.0 to 2.6 kg.The potassium production efficiency(defined as the grain production per unit of K2O absorbed) is from 35.36-55.58 kg/kg.The period with the highest potassium absorption is from the double ridge to the anthesis and then the period from the seedling emergence to the double ridge,and after the anthesis,however,potassium presents negative accumulation.According to the characteristics of potassium nutrition,the potassium fertilizer amount applied for super highly-yielding winter wheat with a grain yield 9000 kg/ha should not be less than K2O 90 kg/ha under the conditions of straw returning to soil.