Relationship of the humus components and the calcium form with the development of limestone soil

Selecting the limestone soil samples at different developing stages(black limestone soil, brown limestone soil and yellow limestone soil),the form and contents of the humus and calcium have been measured, the results show that:(1)at different developing stages of the limestone soil, the total carbon in the humus of black limestone soil, brown limestone soil and yellow limestone soil is 230.15 mg/g, 37.49 mg/g and 17.94 mg/g respectively, the proportion of humic acid is 31.94%、9.44% and 7.25% respectively, fulvic acid accountsfor1.04%,36.14% and66.16%,and humin is 67.02%, 54.41% and 26.59% respectively; (2)the total calcium of the black limestone soil, brown limestone soil and yellow limestone soilis21486.66 mg/kg,6913.33 mg/kg and5540.17 mg/kg respectively, the acid-soluble calcium has the highest proportion, with the proportion of57.58%,74.69% and80.83%,followed by the reduced calcium, oxidized calcium and residual calcium; (3)the correlation analysis shows that the soil calcium and the different forms are positively related with SOC, humic acid and humin, negatively related with fluvic acid. It means that the forms and components of the humus can influence the form and components of the soil calcium to a large extent.