| Summary: | One of the major factors limiting plant growth is acid soil. In general lime is used for soil amendment in acid soil. However, It has been reported that gypsum or phosphogypsum can be used for ameliorating soilacidity. Pot experiment was conducted to study the effects of lime, phosphogypsum and kieserite on soil properties and plant growth in Kho Hong soil series (coarse loamy, kaolinitic,isohyperthermic, TypicKandiudults) which was considered as acid upland soil (pH 5.07). Sweet corn variety INSEE 2 was used as the test crop. The experiment was a completely randomized design with 4 replications and 19 treatments asfollow : unamended, application of hydrated lime and dolomite to raise soil pH at 5.5, application of hydrated lime and dolomite combined with phosphogypsum at the rate that can supply calcium 0.25, 0.50,0.75 and 1 time of both limes, application of hydrated lime and dolomite combined with kieserite at the rate 0.25, 0.50,0.75 and 1 times of sulfur requirement for corn (40 kg S ha-1). The result showed that shoot and root dry weights of corn were increased when lime materials, phosphogypsum and kieserite were applied and the drymatter weights were increased according to the increasing of phosphogypsum and kieserite. The maximum shoot dry weight (18.98 g pot-1) was obtained when 1 times of kieserite was supplied with dolomite and wassignificantly (P<0.01) higher than those of the unamended treatment, only hydrated lime and dolomite treatments, which had dry weights of 12.64, 15.18 and 15.67 g pot-1 respectively. Phosphorus and K uptakewere not significantly different in all treatments and the lowest uptake of N, Ca, Mg and S was obtained in the unamended treatment. The maximum uptake of N (512.10 mg pot-1) was found when 0.5 times ofphosphogypsum was applied together with dolomite. Calcium and Mg uptake was likely to increase according to the increasing rate of soil amendment application. Highest uptake of Ca (42.51 mg pot-1) was obtainedwhen 0.75 times of phosphogypsum was applied together with dolomite and maximum uptake of Mg (54.12 mg pot-1) was found when 1 times of kieserite was supplied with dolomite. Sulfur uptake was also increasedwhen increasing the rate of phosphogypsum and kieserite application and maximum uptake of S (26.00 mg pot-1) was obtain when 0.75 times of phosphogypsum was supplied with lime. Application of limes combined with phosphogypsum and kieserite could increase Ca, Mg and S and was significantly decrease exchangeable acidity and aluminum of soils. It was found that application of dolomite and phosphogypsumat the rate of 0.5 time of Ca in dolomite resulted in the minimum decrease of exchangeable aluminum (0.27 cmol(+) kg-1).
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