Search

The objective of this study was to compare the neutralization power of amendments based on calcium and magnesium and to assess their effects on the cation exchange complex in soils of flat Pampas of Santa Fe. Three amendments (lime, dolomite and mixture amendment) at rates calculated to neutralize 100% and 150% of exchangeable hydrogen were applied to samples from soils incubated for 60 days. The responses on actual and potential pH, and hydrogen, calcium and magnesium exchangeables were assessed. The increment of actual pH showed differences between amendments and the order of response was lime > dolomite > mixture amendment. No difference between the applied rates were observed. The potential pH was more sensitive to the type and of rates amendment. All treatments reduced the level of unsaturation, although the full neutralization was not achieved with the tested rates. Increments of exchangeable calcium were observed in all treatments and the greatest calcium saturation was obtained when lime or mixture amendment were applied at the highest rate. Dolomite and mixture amendment significantly increased the content of magnesium regardless of the rate. The information presented here is useful for prescribing magnesic-calcareous amendments in soils of the flat Pampas of Santa Fe. [ABSTRACT FROM AUTHOR]

Rice growth in wefiands or paddy soils is economically important in Latin America, where lime amendment is becoming a conventional practice. A field study was conducted to compare changes induced by liming a rice soil in Corrientes (Argentina). Three different treatments were considered: control, with no lime addition, and two applications of dolomite at rates of 625 kg/ha and 1250kg/ha. Physico-chemical parameters (Eh, pH) and nutrients (NH[SUB 4,SUP +]-N, K, Olsen-P and extractable Mn, Fe and Zn) were measured just before flooding and during a ten week period after flooding. At the beginning of the experiment pH ranged between 4.0 and 4.4 and in all the treatments a sharp pH rise was observed from week two to week four after flooding. The initial differences in pH between the control plot and plots amended with dolomite disappeared at the end of the ten week period, when pH conditions were near neutrality. Before flooding, high NH[SUB 4,SUP +]-N differences between treatments were observed; during anaerobiosis the trend was to increase the low initial NH[SUB 4, SUP +]-N level of the control plot, whereas the high initial level in the amended plots decreased during waterlogging. Olsen-extractable P was also initially higher in the amended plots than in the control plot and after flooding no unique trend was observed in the three treatments, in all of the treatments, Mn and Fe contents were found to increase during the waterlogging period. Lime enhanced the extractability of these two elements and differences of Mn and Fe levels between control and dolomite amended plots were greater as the flooding period increased. [ABSTRACT FROM AUTHOR]