296 ACTIONS OF AETIFICIAL MANURES 



know that the compound need undergo no change in order to 

 feed the plant, it can be taken up directly and has a very 

 immediate nutritive effect. Similarly it has little apparent 

 action upon the soil; nitrate of soda is not only readily 

 soluble in water, but it does not enter into combination with 

 any of the soil constituents, and is therefore not retained, but is 

 washed out at once when there is any drainage through the 

 soil. There is without doubt some interchange of bases 

 between the soda of the manure and the other bases in the soil 

 zeolites, because a dressing of nitrate of soda always assists 

 the plant to obtain potash from the soil ; but the nitrate part 

 of the salt suffers no change whatever before its absorption by 

 plants and other organisms. Yet it is very clear that nitrate 

 of soda has some action upon heavy soils, for all farmers upon 

 clay recognise that the use of nitrate of soda leaves the land 

 very wet and sticky. This is perhaps most apparent in districts 

 where early vegetables are grown, as in the Evesham country 

 and in Cornwall, for there the market gardeners, who are trying 

 to push on early cabbages and broccoli to secure the earliest 

 possible market, use quantities of nitrate of soda which seem 

 incredible to the ordinary farmer, as much as 10 and 15 cwt. 

 per acre. Such a dressing is apt to leave the land in a terrible 

 state of bad tilth, from which it takes some time to recover. 

 Some of the Eothamsted plots show exactly the same result ; 

 the bad texture of the soil, where nitrate of soda has been 

 applied regularly in large quantities, is not perhaps so marked 

 on the wheat field as it is on the mangold field, but there the 

 nitrate plots are excessively wet and sticky after rain, and dry 

 with a hard glazed surface that marks off the plots to the eye 

 from a considerable distance. In either wet or dry weather the 

 nitrate plots can at once be distinguished on walking over them 

 by their tread and feel to the sole of the foot. It is unnecessary 

 to multiply instances, as the effect is pretty generally recognised ; 

 usually it has been explained as due to the attraction of nitrate 

 of soda for moisture. Nitrate of soda is always damp because 

 of its fondness for water, and a bag of the salt left standing 



