154 QUEENSLAND AGRICULTURAL JOURNAL. {1 Mar., 1902. 
on plants. It may be used for all purposes to which the nitrate is applied, but 
should be put on the land earlier than the latter, because it has to undergo 
NITRIFICATION (the process by which the material containing the nitrogen is 
decomposed, to set the nitrogen free) before the nitrogen is available as plant 
food. 
Other slow-acting nitrogenous manures are those I told you of in Lesson 
4, so I need not describe them here. Indeed, this whole lesson is really only 
an extension of the 4th. Of Porasn manures, the best known is that called 
Karyrr, a mineral obtained in Germany consisting mainly of Chloride of Potas- 
sium or Muriate of Potash, Sulphate of Magnesia, Common Salt, &c. Muriare 
or PorasH is a very useful fertiliser for potatoes and root crops. It is of not 
much value’in heavy soils, as they generally contain potash, but light soils are 
benefited by it. 
Common Saxr is often applied in small quantities to the soil. As a 
manure proper, salt is not required by plants, as Sodium has been proved by 
numerous experiments not to be essential to plant life; there must then be 
some other reason for its use. This reason we find in the INDIRECT acTrIoN of 
salt in decomposing some substances in the soil, and so setting free something 
needed by the plants. This was only lately discovered, and pages used to be 
written and extraordinary statements made about the use of salt, some declar- 
ing it a valuable manure, others a rank poison, and the chemists themselves did 
not know what use it was if applied to the soil. It is sometimes used to 
prevent too rank a growth, but how it acts in this case is not properly under- 
stood. It is quite possible that the checking of the growth is due to the plants 
being poisoned by the salt. At any event, such a suggestion is made by 
Professor Storer in his valuable work, “‘ Agriculture in some of its Relations 
with Chemistry,” Vol. JI. He says also that Nessler discovered that tobacco 
grown on land manured with salt had tougher and more flexible leaves than 
that grown on unmanured adjacent land. Now, there is a cheap, simple 
experiment you can and ought to make in your garden. You might make a 
discovery which might be of very great value to tobacco-growers in Queens- 
land. 
Limr.—the use of lime in agriculture is of such importance that I could 
write many pages on the subject, but here I shall just briefly tell you what 
it is used for and how to use it. Hereafter you will find all about it in 
various books on agriculture, which no farmer should be without. 
If there is no lime in a soil, no crop can grow on it. All plants require 
more or less of it. In an acre of average soil taken to the depth of 1 foot 
there are, at an exceedingly low estimate, 3,250 lb. of lime. There is a certain 
quantity of lime in farmyard manure and in all the artificial manures. Now, 
how does lime act on the soil? Is it a direct fertiliser? These are the only 
two questions you need replies to. 
Carponate oF Catcrum—that is, Limestonre—is, as Ihave stated, found 
in all soils. When this is burnt, it becomes QUICKLIME ; and when the latter is 
mixed with water, itis then sLAKED LIME. It acts with acids in making clay 
soils more friable and pervious to water, and it promotes the decomposition of 
vegetable matter and organic manures and the formation of nitrates in the soil. 
Thus the clay soil is rendered warmer and easier to work ; material containing 
potash is broken up, and the potash is, by the action of the lime, presented in 
an ayailable form as plant food, but which prevents it from leaching out of the 
soil. It also acts in rendering available all three of the plant foods which lie 
dormant in the soil. That is its chemical action. 
' Its physical action is to render stiff clays easier to cultivate and better able 
to supply moisture, heat, and air to the plants. 
It improves the texture of sandy soils, making them more compact and 
better able to retain moisture and fertilisers. But lime must not be used 
heavily on a sandy soil, or the latter will soon be exhausted by the above 
chemical action of the lime. 
