FARM LANDS OF NEW SOUTH WALES. 57 



asparagus, benefit from its presence; it is also -aid to be a good manure for 

 mangels and cabbages; and such plants as saltbushes, &c, contain consider- 

 able quantities in their tissues. Most farm crops will stand as much as from 

 01 to 0-2 per cent, salt in the soil, but if the amount exceeds this quantity, 

 crops are likely to be affected. 



The action of salt is injurious in several ways. It affects the production 

 of nitrates and the process of nitrification, and also affects the texture of the 

 soil. The addition of salt, in the first instance, flocculates the clay particles, 

 and makes the soil temporarily more friable; but it has a very damaging 

 after-effect, due probably to its combining chemically, with exchange of base, 

 with the silicates, particularly silicate of lime, and forming colloidal sili- 

 cates, thus rendering the clay slimy. 



Manganese. 



Although salts of manganese, in small quantities, are found to be beneficial 

 (indeed some chemists go so far as to say necessary) to the growth of crops, 

 they are undoubtedly injurious in larger quantities. Several instances have 

 come under our notice in which small, bare patches occur in a field otherwise 

 fertile; and examinations of these patches and of the surrounding good soil 

 have shown them to be similar in all respects, except that the bare patches 

 contain manganese, whereas the good soil either contains none, or propor- 

 tionaltely much smaller quantities. 



The action of manganese is peculiar, and extremely interesting. It would 

 appear that certain compounds of manganese are more toxic than others, and 

 that the higher oxides of the metal are more toxic than the lower, so that 

 the process of aeration, usually of benefit in increasing the soil's fertility, has 

 in this case a distinctly prejudicial action. The result is that it may happen 

 that a soil may yield good results for a year or two, and suddenly develop 

 toxic properties, due to the conversion of the more innocuous forms of man- 

 ganese into higher oxides of greater toxicity. Another point of some interest 

 is that, when the quantity of manganese present is small in amount, it 

 frequently happens that crops suffer during the winter months, and provided 

 the quantity of manganese present is not excessive, recover themselves with 

 the advent of the warm weather, and when their growth is more vigorous. 

 Soils containing excessive quantities of manganese are generally dark in 

 colour, and frequently it is possible to distinguish small particles of man- 

 ganiferous compounds, black in colour, and very soft. 



Generally speaking, manganese poisoning may be suspected when the 

 affected patches are darker in colour than the normal soil, when the bad 

 effects do not appear until the land has been under crop for a year or two, 

 and when the crop suffers in the winter and recovers itself during the 

 summer. It not infrequently happens that these bare patches change their 

 position from year to year; that is to say, an area which was bare one 

 season will resume its normal condition in the next, while other patches in 

 the same paddock will become infertile. Such a condition of affairs will 

 lead one to suspect the presence of manganese. 



With regard to remedies, it has been found that the addition of super- 

 phosphate has a decidedly beneficial influence on such soils, probably due to 

 the formation of manganese phosphate — a compound of lower toxic action 

 than the oxide. The data so far obtainable are insufficient to justify this 

 being put forward as an infallible remedy, but it has been found to be 

 successful where it has been tried, and is worth further trial. 



