26 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



and should be sparingly used on clay soils. Nitrate of soda also 

 produces a similar result owing to the chemical action of its residue 

 soda, which deflocculates the clay. Salt acts in the same way for the 

 same reason and should not be used on heavy soils. Soot has its 

 greatest effect on cold heavy soils and will be found very useful. So 

 much for the treatment necessary to improve the mechanical condition 

 of heavy soils. 



Let us now consider the other extremity — the light sandy soil. 

 We have seen that the sandy nature of a soil is due to the large size 

 of its particles. Such soils are therefore liable to be too much like a 

 sieve in that they let the moisture through them too quickly and with 

 it the food materials that are dissolved in it. Our object, therefore, 

 will be to bind them together and make them more like a sponge 

 that will hold the moisture and less like a sieve. Light soils are 

 generally deficient in humus, and owing to free aeration and great 

 bacterial activity any humus added soon disappears. We must 

 therefore, in dealing with these soils, remember that humus must be 

 added, but bulky manures must be used carefully, otherwise they are 

 apt to open these soils too much and make them hollow. When 

 this mistake is made light soils dry out extraordinarily quickly. It 

 must be remembered that a sand is largely dependent on sub-soil water 

 for its moisture, and therefore nothing must be done to upset the 

 capillary attraction by which the water passes from below to the root 

 area near the top of the soil. 



It is generally claimed that lime acts as a binding agent in light 

 soils in the same way as it does in mortar. Light soils are frequently 

 deficient in lime, and the point should therefore not be overlooked. 



With regard to manuring such soils, as we have already seen, humus 

 is very necessary, but on the other hand nitrate of soda may be used 

 without harmful mechanical effect, and acid minerals may also be 

 resorted to when necessary, provided of course that sufficient lime 

 is present. 



The intermediate soils are easier to manage. The considerations 

 referred to above will come into play more or less according to whether 

 a soil is on the heavy or light side. It may be noted that the manage- 

 ment of all soils is largely directed towards the obtaining of the best 

 water supply. In a clay soil we require to let the water through : in 

 a sandy soil we require to hold it. In this connexion it is interesting 

 to note the " colloidal " property of water. Water, as is well known, 

 has to a certain extent an adhesive elastic nature. This is seen in the 

 capillary attraction referred to above, on which we rely when rolling 

 a soil in order to attract the moisture from below. The hoeing of 

 a soil in dry weather has for its object the conserving of the moisture 

 below the top few inches by severing the capillary tubes in the soil, 

 and keeping a " mulch " of dry soil on the top. This is quite a different 

 thing from the ordinary mulching resorted to in green-houses and 

 in the garden generally, the object of which of course is to place a 

 spongy layer on the top of the soil to hold the moisture. 



