Multivariate statistical technique was used to determine the potassium （K＋） status and to assess soil fertility and K leaching potential in some calcareous soils. Water-soluble K＋ （H20-K） and ammonium acetate-ex...Multivariate statistical technique was used to determine the potassium （K＋） status and to assess soil fertility and K leaching potential in some calcareous soils. Water-soluble K＋ （H20-K） and ammonium acetate-extractable K＋ （NHaOAc- K） ranged from 0.019 to 0.590 （mean value 0.095） and 0.390 to 3.320 （mean value 0.954） cmolc kg-1, respectively. The nitric acid-extractable K＋ （HNO3-K） varied from 1.03 to 13.63 （mean value 5.37） cmolc kg-1. The proportion of H20-K ranged from 0.34% to 14.8% of HNO3-K, and 2.2% to 53.2% of NHaOAc-K. The proportion of NHaOAc-K ranged from 5.8% to 80% of HNO3-K （mean value 23% of HNOa-K）. The tendency of the soil to lose K＋ by leaching was examined by determining K＋-Ca2＋ exchange isotherms. The soils mostly had moderate to high values of K＋ sorption capacity, ranging from 10% to 58% （mean value 28%） of added K＋. The Gapon coefficient varied widely from 1.1 to 12.0 （L mol-1）-1/2. Clay minerals were dominated by illite, smectites and vermiculite with small amounts of kaolinite. Principal component analysis （PCA） showed that the first four components accounted for 27.7%, 21.4%, 13.8%, and 8.9% of total variation, respectively. The non-hierarchical cluster analysis （k-means clustering） grouped 75 sampling sites into six clusters, based on the similarity of soil quality characteristics. The results suggested that such classes could form a basis for variable-rate application to maintain an adequate K＋ status for crop production and to reduce potential K＋ loss from soil by leaching.展开更多
文摘Multivariate statistical technique was used to determine the potassium （K＋） status and to assess soil fertility and K leaching potential in some calcareous soils. Water-soluble K＋ （H20-K） and ammonium acetate-extractable K＋ （NHaOAc- K） ranged from 0.019 to 0.590 （mean value 0.095） and 0.390 to 3.320 （mean value 0.954） cmolc kg-1, respectively. The nitric acid-extractable K＋ （HNO3-K） varied from 1.03 to 13.63 （mean value 5.37） cmolc kg-1. The proportion of H20-K ranged from 0.34% to 14.8% of HNO3-K, and 2.2% to 53.2% of NHaOAc-K. The proportion of NHaOAc-K ranged from 5.8% to 80% of HNO3-K （mean value 23% of HNOa-K）. The tendency of the soil to lose K＋ by leaching was examined by determining K＋-Ca2＋ exchange isotherms. The soils mostly had moderate to high values of K＋ sorption capacity, ranging from 10% to 58% （mean value 28%） of added K＋. The Gapon coefficient varied widely from 1.1 to 12.0 （L mol-1）-1/2. Clay minerals were dominated by illite, smectites and vermiculite with small amounts of kaolinite. Principal component analysis （PCA） showed that the first four components accounted for 27.7%, 21.4%, 13.8%, and 8.9% of total variation, respectively. The non-hierarchical cluster analysis （k-means clustering） grouped 75 sampling sites into six clusters, based on the similarity of soil quality characteristics. The results suggested that such classes could form a basis for variable-rate application to maintain an adequate K＋ status for crop production and to reduce potential K＋ loss from soil by leaching.
