The importance of potassium (K) in both plant growth and soil fertility is widely recognized and has a close relation to the long-term sustainability of the soil in which a plant grows. Hence, characterizing the soil K reserve and its availability to plants is important in determining the K supplying capacity of soils. Currently, soil K is understood to exist in four distinct K pools that differ in their accessibility to plant roots, with reversible transfer of K between the pools.

A team led by Huoyan Wang from Institute of Soil Science CAS established a new grading system for plant-available potassium (K) in soils based on K release rate from soils and plant growth indices. In the study, fourteen different agricultural soils from the southern subtropical to the northern temperate zones in China were analyzed by both chemical extraction methods and exhaustive cropping techniques. Based on the change trends in plant growth indices, relative biomass yields of 70% and 50%, K-deficient coefficients of 35 and 22 under conventional exhaustive experiments, and tissue K concentrations of 40 g/kg and 15 g/kg under intensive exhaustive experiments were obtained as critical values that represent different change trends. In addition, the extraction method using 0.2 mol/L sodium tetraphenylboron (NaTPB) suggested soil K release rates of 12 mg/kg/min and 0.4 mg/kg/min as turning points that illustrated three different release trends. Thus, plant-available K in soils was classified into three categories: high available K, medium available K and low available K, and grading criteria and measurement methods were also proposed. This work has increased our understanding of soil K bioavailability and has direct application in terms of routine assessment of agriculture soils.

The research achievements have been published in the Scientific Reports.

Paper links: http://www.nature.com/srep/2016/161123/srep37327/full/srep37327.html

(Information Source: Nanjing Branch of CAS)