Effect of liming materials for improvement of acid soils (Sanpatong soil series) under corn-blackbean cropping system   Khamchai Kanjanathanaset Bunjirtluk Jintaridth Jumpol Yuwaniyama and Charoen Charoenchamratcheep   ABSTRACT         The study on liming materials for improvement of acid soils (Sanpatong soil series) under corn-blackbean cropping system was conducted at the Lampang Land Development Station, Lampang Province, during 1992-1995. The experiment was designed in 4x4 factorial RCB with 3 replication comprising of 2 factors: sort of liming materials includes no liming, limestone, slaked lime and dolomitic limestone in the rate of 300 kg CCE/rai; and 4 rate of chemical fertilizer includes no chemical fertilizer (0-0-0), low rate (8-10-6), medium rate (12-15-9) and high rate (16-20-12) kg./rai of N , P2O5 and K2O. The first year results under chemical fertilizer application, the slaked lime showed the highest efficiency to increase soil reaction and gave the average corn yield of 468.7 kg/rai. The application of the slaked lime with the high rate of chemical fertilizer gave the highest corn yield of 523.5 kg./rai. The corn yield was not significant difference from the medium rate of chemical fertilizer but the low rate and no fertilizer. For the limestone and dolomitic limestone showed the lower residual effects. For the blackbean following corn, the application of the slaked lime and the high rate of chemical fertilizer gave the highest efficiency with the highest blackbean yield of 76.3kg./rai. The three sort of liming materials resulted the same residual effects on the blackbean yield. For the second year, the residual effects of the limestone application gave the highest corn yield of 161.7 kg./rai and applied with the high rate of chemical fertilizer gave the highest corn yield of 185.7 kg./rai , which was not significant difference from the medium rate. However, the limestone showed the same residual effect as the slaked lime. For the blackbean yield, the application of liming materials and chemical fertilizer gave the same result as the corn yield. The third year residual effect of dolomitic limestone gave the highest efficiency with corn yield of 478.9 kg./rai and applied with the medium rate of chemical fertilizer gave the highest corn yield of 567.5 kg./rai, which was not significant difference from the low and high rate. For the limestone and slaked lime gave the same lower residual effects. The application of the slaked lime and the high rate of chemical fertilizer gave the highest blackbean yield of 75.3 kg./rai. After the third year, it showed that the application of various liming materials increased soil pH form 4.4 to the highest pH 5.9 by dolomitic limestone, pH 5.8 by limestone and pH 5.6 by slaked lime. Furthermore, liming materials increased available phosphorus from 21 to 37-42 ppm, calcium from 0.46 to 0.93-1.24 me/100 g. soil and reduced aluminum to 0.09-0.11 me/100 g. soil         Keywords : limestone , slaked lime , dolomitic limestone , acid soils