Effects of different acidic materials on pH value of calcareous soil

The effects of acidic material on calcareous soil pH were studied by soil culture experiments in lab.The results indicate that the phosphoric acid can effectively reduce the pH value of calcareous soil and the proper acid amount is 3.27g/100g soil which can reduce soil pH from 8.89 to about 6.0.It is not practical to use pH 5.5 phosphoric acid or sulfuric acid solutions to acidify calcareous soil.NH_4H_2PO_4 not only presents better acidification effects,but also has pH buffer capability.It can reduce soil pH value from 8.89 to 6.39 and keeps the acid condition longer as adding 2.3g NH_4H_2PO_4 pre 100g calcareous soil.As an adding dosage of S is 5% of soil,the soil pH value can decrease from 8.90 to 7.0～7.5 in 30 dyas.