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STATE BOARD OP AGRICULTURE. 



nesium was not determined in case of the calcium salts treatments, but the 

 order of magnitude of calcium fixation in these experiments follows closely 

 the order of quantity of magnesium liberated from the soils as shown in 

 Table 2. Also, much greater quantities of calcium were fixed by the soils 

 after treatment with a MgCla solution containing 0.2581 gm. magnesium 

 per 500 c.c. of solution, and thorough washing, as shown in Table 5, column 

 4; evidence that the fixation of calcium in these cases depended upon the 

 quantity of magnesium in the soils in condition to react. Closely equivalent 

 relationships between magnesium fixed from MgClo and calcium found in 

 the soil solutions are shown in Table 5, the exact equivalent ratio in this case 

 being 1.6476. Also, calcium and magnesium were not fixed by the various 

 soils in equivalent quantities showing that different soil factors were operat- 

 ing in each case. Anions of the calcium and magnesium salts were not fixed 

 by the soils to any great extent at least, and the solutions from all the cal- 

 cium and magnesium salt treatments were alkaline to red litmus paper. 



Reversibility of the Fixation Processes 



It was previously shown that the fixation of magnesium by the soils was 

 reversed by a calcium salt treatment and that the magnesium treated soils 

 fixed much more calcium than the same soils in a natural state. Another 

 experiment was made to determine the reversibility of other fixed cations by 

 causing cations to be fixed in soils and then treating with salts containing 

 other cations. In this experiment the alkaline and acid sandy loam soils 

 were used, with the chlorides of potassium, sodium, calcium and magnesium. 

 No attempt was made to fix calcium in the untreated soils because the small 

 quantities of calcium fixed by the soils makes the experimental procedure 

 more difficult. Proportions of soils and solutions were the same as used for 

 the KCl treatments, namely, 100 gms. of soil and 500 c.c. of a 0.02 N salt, 

 solution. Results and further explanations of this experiment are given in 

 Table 0. Fixed cation equivalents were determined by computing from 

 the quantities of cations found in the solutions as shown in the table, other 

 than those used in the final treatments, the quantities necessary to be fixed 

 to satisfy the respective gram-equivalent ratios. 



TABLE 6. — (.4) Alkaline and acid sandy loam soils treated with KCl Solution. Washed thoroughly with 

 with distilled water, then treated separately with NaCl, CaCli and MgCH solutions. 



