Scientific Agt iculture. 



456 



[May 1908. 



and not knowing whether it will be able 

 to outlive it, produced seed to ensure the 

 preservation of its own kind. 



It is a well-known fact, that trees, 

 having been severely injured by stormy 

 winds, ring-barking, or other such causes 

 will seed abundantly before they die, 

 and I think that no better example and 

 proof for my theory could be given, 

 than the enormous amount of nuts on a 

 gum tree, after it has been ring-barked. 

 Is there any explanation but the tree, 

 foreseeing its approaching end, tries to 

 make sure of the preservation of its own 

 kind ? Often, after a long dry summer, 

 fruit tree will grow into blossom in 

 autumn (shortly after losing their 

 leaves) ; and this is nothing but a des- 

 73erate last attempt to propagate its own 

 kind before the dreaded end. A well- 

 pruned tree, if heavily manured, will 

 produce more wood and less fruit, be- 

 cause it is too well off, and not anxious 

 to reproduce its own kind. Under nor- 

 mal conditions the tree would have 

 answered to the pruuing by producing 

 abundant fruit ; but the heavy manuring 

 makes it again feel strong and vigorous ; 

 it forgets the injury of the pruning 

 knife and it produces wood, to continue 

 its individual lite. We find, therefore, 

 that only he is a good pruner, who 

 knows how to estimate the vigour of 

 life in every single tree, and prunes 

 accordinglv — Journal of Agriculture, 

 W. A. Vol. XVI. Part 2. February 1908. 



LIME AND ITS RELATION 

 TO AGRICULTURE. 



Br. Percy G. Wickex. 



Lime, according to the works of 

 ancient writers, was one of the earliest 

 substances used for improving the 

 productiveness of the soil. It has been 

 largely used in Europe for several cent- 

 uries, and the earliest American writ- 

 ings show that lime took a prominent 

 place in the agricultural history of that 

 country. 



Lime has also been used to a more or 

 less extent in the Australian States, 

 but has by no means been universally 

 adopted, and its use in a judicious 

 manner would prove beneficial to the 

 Australian farmer in many ways. 



The term "lime" is generally under- 

 stood to mean quick or caustic lime or 

 calcium oxide, chemical symbol (CaO. 

 "When any form of caibonate of lime, 

 limestone, oyster shells, or shell marl, is 

 burned, the caibonic acid is given off 

 and lime or quicklime is produced. In 

 burning, the calcium caiboinale under- 



goes decomposition, the carbonic acid 

 being throwu off and the caustic or 

 quicklime remaining in the kiln. The 

 fuel generally used in burning is wood, 

 and some of the ashes from this will be 

 found as impurities in the lime. 



Lime may be burnt in a number 

 of ways from the rough pile of 

 logs with the stone of shells piled on 

 top, to the most modern furnance made 

 ot solid masonry, firebricks, and boiler 

 plate steel, but the result is about the 

 same, except in the cost of carrying out 

 the operations. 



Burning : — Limestone or any carbon- 

 ate of lime begins to decompose at 

 about 300 degrees C, and the temper- 

 ature usually employed is indicated by 

 a bright red heat ; it should not be allow- 

 ed to exceed 1,100 degrees C. The 

 facility with which lime is burned de- 

 pends upon the poi'osity and composi- 

 tion of the stone, the size of the lumps, 

 and the quantity of air passed through 

 tbe burning mass. Again, the expul- 

 sion of carbonic acid is facilitated by 

 the introduction of steam into the mass, 

 This accomplished by lime burners by 

 watering limestone which has become 

 dry by exposure to the air. If the tem- 

 perature rises too high, the lime is said 

 to be "dead burnt," or "over burnt" 

 and will not slack. In burning, lime- 

 stone retains about the same volume, 

 but loses about 44 percent, in weight, 

 that is 100 lb. of stone yields about 56 lb. 

 of lime. If the lime has been properly 

 burned, it forms a hard white stony sub- 

 stance, which slakes or combines with 

 water in the proportion of 18 lb. of water 

 to 56 lb. of lime ; both under burnt or 

 over burnt lime slake badly, and are not 

 so valuable as well burnt lime. 



Terms. — We often hear the term 

 " agricultural lime" and "building lime" 

 mentioned, as if they were different 

 articles, but in reality no difference 

 exists, and the same article is used for 

 both purposes. Sometimes the term 

 "agricultural lime" is used to mean 

 " building lime " that has been air or 

 water slaked, and sometimes refers to 

 the kind of stone from which is derived ; 

 more often, however, any inferior lime 

 which is not suitable for building is 

 termed "agricultural lime." The vari- 

 ous kinds of lime used in agriculture are 

 as follows :— 



Stone Lime. -Good limestone contains 

 from 50 to 55 per cent, lime CaO aud 

 40 to 44 per cent, carbonic acid, with 

 smaller amounts of magnesia, silica, iron, 

 and alumina. Such limestone when 

 burnt would produce the best quality of 

 caustic or quicklime, containing SO to 

 98 rcer cent, of calcium oxide (CaO). 



