Saranya Dam-ampai, Chairat Nilnond, and Jumpen Onthong

pp. 117 - 131

Abstract

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 soil
acidity. 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, Typic
Kandiudults) 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 as
follow : 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 dry matter 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 was significantly (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 uptake were 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 of phosphogypsum 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 obtained
when 0.75 times of phosphogypsum was applied together with dolomite and maximum uptake of Mg (54.12mg pot^-1) was found when 1 times of kieserite was supplied with dolomite. Sulfur uptake was also increased
when 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 phosphogypsum at the rate of 0.5 time of Ca in dolomite resulted in the minimum decrease of exchangeable aluminum (0.27 cmol(+) kg^-1).