1. Nongkran Maneewan Land Development Department, Thailand

2.  Thailand occupied 5.5 million rais or 0.88 million hectares of acid sulfate soils. Distribution of acid sulfate soils in Thailand

3.  Most of area is in the Central plain  Some in the South and the East

4. 1/3KFe 3 (SO 4 ) 2 (OH) 6

5. Classification of ASS 1. Severely ASS pH<4.0 (jarosite 0-50 cm.) area 870,493 rais (0.139,278 m.ha.)

6. 2. Moderately ASS pH 4.0-4.4 (jarosite 50-100cm.) area 2,211,060 rais(0.353 m.ha.)

7. 3.Slightly ASS pH 4.5-5.0 (jarosite >100cm.) area 2,428,591 rais(0.388m.ha.)

8. Problems of ASS  low pH(<4.0 -5.0 )  lack of N P  Al Mn Fe toxicity  low micro organism activities

9. These soils are suitable for paddy but give the low yield, only 200-300 kg./rai(1.25-1.875 t/hec ) Therefore,managements of ASS are needed to increase rice yields.

10. Objectives study the appropriate rate of chem. fert. study the appropriate rate of liquid organic fert. and effect of GM Study the changed of soil properties To analyze the economic return

11. RCBD, 7 treats. with 3 reps. pH 8.12)Marl ( pH 8.12) was applied and incorporate in soil 7 days before planting. H 2 SO 4 +CaCO 3 CaSO 4 + H 2 O+CO 2

13. rates of marl for basal application rates of marl for basal application  Ayutthaya 499 kg./rai 1123 kg./rai 1123 kg./rai 1000 kg./rai  Okharak  Rangsit

14. 7 Treatments consist of 0-8-0, 8-8-0 and 12-12-0 N-P 2 O 5 -K 2 O kg./rai (RS and Ay soil series) 0-0-0, 8-0-0 and 12-0-0 N-P 2 O 5 -K 2 O kg./rai (Ok soil series) Liquid organic fert. 10 litre/rai Liquid organic fert. 15 litre/rai Liquid organic fert. 25 litre/rai

15.   Sesbania rostrata, green manure, was grown and incorporate in soil 10 days before rice planting

16.  chemical fert. was applied 2 times at planting date and 45 days after transplanting and liquid organic fert.was sprayed 3 times at 30 50 and 60 days of rice growth

17. Result Factors analysis  GM: N 2.46 % 0.417% 2.69 %  GM: N 2.46 % P 2 O 5 0.417% K 2 O 2.69 %  LOF: - oxin 1.68 mg/l. -giberellin 31.01 mg/l. -giberellin 31.01 mg/l.

18. Rice production

19. Rice growth and yields after soils management

20. Without liming, rice cannot grow

21. Rice production on ASS

22. Economic return (bahts/rai)

23. Changed of soil properties(Ay) Chem. properties pH OM(%) Before exp. 5.1 4.8 After exp. 5.5 3.4 P 2 O 5 ( mg./kg) K 2 O ( mg./kg) 10 >120 36 >120

24. Changed of soil properties(Ok) Chem. properties pH OM(%) Before exp. 4.0 4.6 After exp. 4.7 3.1 P 2 O 5 ( mg./kg) K 2 O ( mg./kg) 48 272 29 237

25. Changed of soil properties(Rs) Chem. properties pH OM(%) Before exp. 5.0 1.8 After exp. 5.8 6.2 P 2 O 5 ( mg./kg) K 2 O ( mg./kg) 21 177 17 158

26. Changed of ASS chemical properties Acidity decreased(higher in pH) OM. decreased P 2 O 5 decreased on Ok and Rs K 2 O decreased on Ok and Rs

27. Conclusion 1. Liming is necessary to improve ASS, reduced acidity of soils

28. 2.Fertilizer rates at 8-8-0 N-P 2 O 5 -K 2 O kg./rai (50-50-0 N-P 2 O 5 -K 2 O kg./hec.) gave the highest yields on Rs and Ay soil series.

29. 3. Green manure with liquid organic fert., increase in growth and yield of rice. 4. Water management, Pre-submergence and drainage, reduce soil acidity because sulfuric acid is leached from the soils and.

30. 5.For economic returns, GM with or without LOF gave the highest net incomes on three classes of acid sulfate soils. However, it depends on soil fertility. Therefore, soil analysis is necessary.

31. commentation 1.On irrigation areas, ASS can get more benefit than rainfed areas 2.Double crops of paddy/year can be done(2-3 crops/year)

32. 3.wet soils prevent sulfuric acid occurring in the soils because of no oxidation. 4. Liming at the rate of LR only 1 time can be useful for 5 years.