The K
supplying potential of 11 main
soils in China was evaluated comprehensively with pot experiment of bio--
depletion of soil
potassium and chemical methods. Results were summarized as follows:The stage of the
minimum value appearance and amount of
Soil exchangeable K varied with soil type after soil potassium depletion.The soil exchangeable K also has "utilization ratio" or "availability degree". Its minimum value is one of the important characteristics of soil K supplying potential.As reaching the minimum value the nonexchangeable K increases again with the increase of the potassium depletion time, and finally, approaches or overtakes a level of pre-depletion. The results were suggested that potassium which could not be extracted by boiling in 1 mol/L HNO3 was released largely and absorbed by plants mainly. It would not be mineral K but nonexchangeable K .The closest correlation between the soil available K extracted by cold 2mol/L HNO3 and the content of K absorbed by plantS was revealed by all of the test methods. The procedure of thes method is simple and easy to operate. It is applicable tO test soil K of upland and paddy field. The K suPPlying potential of 11 main soils of China were classified preliminary based on the content of soil available K and its minimum value.
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