钾是植物营养的三要素之一.土壤含钾矿物是土壤中的自然钾源,在自然情况下,植物所需的钾主要来自含钾矿物的风化.在岩石中,如花岗岩和片麻岩含钾量(K_2O)可达4～6%,玄武岩中约为1～5%,地壳中平均含钾量为2.6%.土壤中主要含钾矿物有黑云母(K_2O为6～10%),白云母(7～11%),伊利石(4～7%)和钾长石(11～12%).通过物理风化和化学风化作用,含钾矿物中的钾释放到土壤中,由于成土母质和风化条件的不同,土壤全钾含量差异很大,一般为0.1～3%,平均为1%左右. Potassium is one of the three essential elements in plant nutrition. Potassium is the natural source of potassium in soils and in natural conditions the potassium needed by plants comes mainly from weathering of potash-bearing minerals such as granites and gneiss K2O can reach 4 ~ 6%, about 1 ~ 5% in basalt and 2.6% in the crust. The main potassium-bearing minerals in the soil are biotite (6 ~ 10% K2O) Muscovite (7 to 11%), illite (4 to 7%) and potassium feldspar (11 to 12%). Potassium is released into the soil from potassium-containing minerals by physical weathering and chemical weathering. Different parent materials and weathering conditions, the total potassium content in soils varies widely, generally from 0.1 to 3% with an average of about 1%.