448 QUEENSLAND AGRICULTURAL souRNaL. [1 June, 1900. 
Paradoxical as it may seem, it is none the less noteworthy that liming often 
does good service on lands which already contain no small quantities of lime 
salts. 
It is stated by Hilgard that the general effect of a large percentage of 
lime on vegetation is to encourage a low compact growth and increased fruit- 
fulness, whilst a deficiency of lime in a soil otherwise of good composition 
produces a thin growth and diminished fruitfulness. In support of this, the 
low compact forms of the trees in Western California, Oregon, Nevada, an 
Arizona are cited, due probably less to the parching influence of the sun than 
to the high percentage of lime in the soils. 1s 
Spring or autumn is recommended for the application of lime. In deciding 
which time is most suitable, it must be remembered that rain exerts a great 
leaching action upon lime salts, as appreciable quantities of these are found 1 
the water from field drains. Recent investigations of Heiden show that nine 
times as much lime was dissolved by water from soil limed at the rate of 14 
tons per acre, as from the unlimed soil. ‘The experiment was made six months 
after the lime had been applied. 
The action of lime upon soils is partly chemical and partly physical. AS 
to the first, lime has the power to liberate certain insoluble and inert 
ingredients in the soil— potash, soda, &e., &¢.,—which are of great importance _ 
for plant foods. Fuchs and Zierl have shown that if powdered felspar be 
digested with milk of lime, even at ordinary temperatures, much of the potas! 
in the mineral will pass into the water, and its place be taken by lime. This 
power depends on the chemical condition of the lime, caustic lime being more 
owerful than the other forms. Stoeckhardt has further inyestigated this, and 
Ree shown that caustic lime attacks not only felspar, but also produced quartz, 
forming a hydrated silicate of lime. 
Lime promotes the formation of double silicates of alumina from the clay, 
which is chiefly composed of silicate of alumina. A portion of the alumina 
can be replaced by the compounds potash, soda, lime, and ammonia, forming 
these “double silicates,” which act as reserves of plant food. According t0 
the generally accepted theory, it is in this form that much of the available 
mineral plant foods are retained. 
Hilgard argues that the presence of calcium carbonate in the soil must 
be of great importance for maintaining fertility, because it promotes the 
formation of the more soluble silicates, called zeolites. Lime decomposes 
vegetable matter, setting free the inert nitrogen, which nay become ayailab: € 
as plant food. Lime might profitably be used as an adjunct to green manurilg, 
im which case it should be well worked into the field when freshly slaked. 
It may be remarked that lime must not be mixed with ammoniacal galts—for 
example, sulphate of ammonia—since a loss of ammonia will take place. 
Lime combines with certain organic acids which, when produced in large 
quantities, render the land what we term “sour” By removing this sournes* 
by neutralising these acids with lime, the general conditions of such soils are muc 
benefited, and many of the forms of plant life which exist on sucha soil are kille 
out, their place being taken by others of afinernature. Killern has shown that 
lime sometimes acts upon phosphates, making them more readily available for 
plant food. ; 
Regarding the physical action of lime on soils, lime has the power of 
causing the coagulation of small particles of soil (clay), thus causing the forma- 
tion of larger channels for the passage of air and water. Any farmer can prove 
this for himself by repeating the experiment made by Schloesing, who fou2 
that the extremely fine particles of mud in a mud-puddle which will not settle 
ean readily be made to do so by the addition of a little lime water. ‘Thous 
some other salts will effect this cleaning, Schloesing and Hilgard find none *° 
effective as limewater. 
In stiff clay soils the particles are very fine and very closely packed together 
so that water can only with great difficulty percolate through such. The effec 
of lime on such soils is clearly shown by Pearson, who took three samples ° 
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