143 



In our South Australian conditions, and with our present prevailing practice 

 it will generally be found that deficiency of phosphates is the greatest weakness 

 in our soils, and that phosphatic manures should first have the attention of 

 farmera. 



A Judicious Mixture. 



I would not have it understood that I am suggesting the use of phosphates 

 only and always and invariably. On the contrary, judicious mixtures have 

 much to recommend them, and a man cannot expect to get the best results unless 

 he adopts such as occasion demands. There is, however, much to lead me to 

 give phosphatic manures a fair trial first, as from experiments conducted here 

 and elsewhere it has been shown that phosphates alone have often given better 

 results on wheat lands than more expensive mixtures of phosphatic and nitro- 

 genous manures. As bone dust contains from 3 to 4 per cent, of nitrogen it has 

 been found that it can be used by itself for a longer succession of years than 

 superphosphate, but at the same time let it once be recognised that the mixtures 

 of artificial manures is the desirable practice, and that the application of one form 

 — phosphatic, nitrogenous, or potassic — by itself is the exception to be practised 

 only under suitable conditions, and much relatively unprofitable manuring will 

 be avoided. 



Value of Bare Fallowing. 



Again, our practice of bare fallowing for wheat, which is almost universally 

 practised in the colony, is a means of slightly increasing the relative proportion 

 of nitrogen, because — 



1. It promotes nitrification, i.e., it brings about conditions favourable for 

 the activity of the myriads of micro-organisms in the soil, and consequently 

 nitrification is correspondingly rapid. 



2. Bare fallowing further is a means of retaining moisture in the land, and 

 consequently a means increasing the absorption of the nitrogen from the air in 

 the form of ammonia or otherwise. 



3. Our dry siimmers and the absence of under-drainage enable us to avoid 

 the loss of nitrogen which occurs in many countries, as nitrates are very soluble 

 and readily go off in water. 



Potash, again, is almost invariably much more abundant in most soils than 

 phosphoric acid, and our practice of continuous wheat-growing is also less 

 exhausting of potash than of phosphoric acid, for much of the potash is left on 

 the farm in the straw, while much of the phosphoric acid goes off in the grain. 

 For these reasons the use of phosphates alone give more frequently than might 

 be anticipated very satisfactory results. 



Bones. 



Bones liaA^e been in use as a means of adding phosphoric acid for more than a 

 century. They were first used as half -inch or quarter-inch bones for the purpose 

 of top-dressing pasture, but now they are crushed very much finer, so as to be- 

 come more readily dissolved and available as plant-food, and applied as bonedust, 

 or bonemeal. They can be had for manurial purposes steamed or unsteamed. 

 Steaming is a means of reducing the percentage of organic matter, which forms 

 about one-third of the composition of bone, and, consequently, of reducing the 

 percentage of nitrogen. At the same time, it is better to have the bones steamed 

 in the process of manufacture of bone dust, because it has been found that the 

 fatty matter present, if not extracted, makes it most difficult to get the dust fine, 

 and also because the fatty matter prevents the agencies of Nature bringing about 

 the decomposition of the bone, and making it available for plant food so readily 

 as in the case of bone dust from steamed l>ones. Steamed bones further give a 

 bone dust richer in the percentage of phosphate of lime in so far as the organic is 

 mostly away. 



Good hone dtint should contain about 48 per cent, of phosphate of lime and 

 from 3 to 4 per cent, of nitrogen. However finely it be ground, it will always 

 become slowly available relatively for plants. It is tlierefore spoken of as a last- 

 ing manure, but that quality, as times are now, is a disadvantage, as the farmer 

 has to wait too long for the recovery of his money. 



Superphosphafe I believe to be the more profitable manure all round, except, 

 on soils deficient in lime and on peaty or very light soils under a heavy rainfall. 



By superphosphate is meant mineral superphosphate, of course, for boue 



