FARM LANDS OK NEW SOUTH WALES. 59 



Excessive Concentration of the Soil water. 



Damage may also be done to the growing plant by otherwise harmless or 

 even beneficial ingredients, when the solution in which they are presented to 

 the plant is too concentrated. During dry spells, for example, the soil 

 moisture will contain a relatively larger amount of soluble saline matter 

 than under normal conditions; and it may quite easily happen lhat a soil 

 on drying out during a dry spell may lose moisture to such an extent that 

 the remaining water may contain an excessive quantity of salts in solu- 

 tion. If the quantity of matter dissolved in the moisture in the soil is in 

 excess of that present in the cell of the plant-roots, the result is that the 

 water will pass out of the cell into the stronger solution outside, with the 

 result that the contents of the cell will shrink and the plant itself wilt. 

 . The ill effects of want of water during a protracted dry spell are thus 

 accentuated by the danger of an over-concentration of mineral matter in 

 the remaining soil moisture. A rich soil, therefore, one well supplied with 

 soluble plant-food, would be expected to show the ill effects of drought even 

 more than a poor one. 



This would also account for the fact that heavy manuring with artificial 

 fertilisers is generally found to be rather harmful than beneficial in dry 

 seasons, and that under such conditions light dressings are superior to 

 heavy ones. 



Calcium Chloride. 



This substance is stated by some authorities to be harmful to the growth 

 of crops, though I am not aware of any exact experiments being recorded 

 which prove its toxicity in the field. We know that chlorides of other metals 

 are frequently injurious. The case of sodium chloride (common salt) has 

 already been dealt with, and certain other chlorides have been found inferior 

 fertilisers for certain crops (such as potatoes and tobacco) ; it is quite likely 

 that calcium chloride is an undesirable form in which to apply salts of lime. 



In certain bare patches at Coolabah Farm were found a considerable con- 

 centration of plant-food in the soil moisture, a small proportion of lime and 

 an absence of carbonic acid; and from the fact that the soil from the bad 

 patches was deliquescent, and contained a larger proportion both of lime and 

 chlorine than the good soil, the presence of calcium chloride was suggested. 



In such cases, also, the addition of lime is the remedy which suggests 

 itself, so that the crop can be supplied with lime in another form than that 

 of calcium chloride. Here, again, it must be borne in mind that the 

 toxicity of calcium chloride has not been proved by exact experiment. 



Alum. 



A substance which is frequently accused of causing infertility in soils is 

 alum. Alum is a double sulphate of alumina and potash, and it is not 

 quite obvious why it should have such a bad name. In water cultures of 

 spirogyra it has been recently found by M. Fluri (Bied. Centr. 1909, 38, p. 

 670) that proportions of aluminum salts as low as 003 per cent, deprive the 

 cells of starch. As a matter of fact, of all the soils examined here in which 

 alum is stated to have been the cause of the trouble, none have contained 

 alum; and the infertility has been due either to sourness (in the majority 

 of cases) or to the presence of common salt or alkali. 



Samples of incrustation or efflorescence occurring on such soils, and stated 

 to be alum, turn out on examination to be salt or alkali, and the trouble is 

 in all cases due to inefficient drainage, and disappears when the land is 

 properly drained. 



