Horticulture. 



33(5 



[April, 1910. 



projecting from the side or top may 

 be cut off so as to keep the tree 

 evenly balanced and fairly compact. 



Cultivation. 



It must be understood that heavy 

 soils require a cultivation different to 

 that applied to light soils, and hillsides 

 have to be treated different to fiat land. 

 Good cultivation is the secret of success. 

 What is meant by " intense culture " 

 is very little understood in Ceylon. I 

 shall therefore gr> into the subject. 

 Cultivation means the admission of air 

 into the soil so necessary for the deve- 

 lopment and woiking of the bacteria 

 in it. This bacteria changes the insolu- 

 ble plant food in the soil into soluble 

 lood. This is t:> say, it converts the 

 nitrogenous compounds in the soil into 

 ammonia. This is the first process which 

 takes place in the soil in the case of 

 all natural nitrogenous manures, and 

 is caused entirely by the bacteria. This 

 process is called " nitrification," and the 

 bacteria which are instrumental in bring- 

 ing about this state of things are called 

 "nitrifying bacteria." These bacteria 

 must have air and warmth, and the 

 better these conditions are the quicker 

 the ammonia will be formed. The second 

 process is brought about by the air 

 which changes ammonia into nitric acid. 

 The nitric acid then combines with an 

 alkaline base, such as potash, soda or 

 lime and forms nitrates^ It is in this 

 form as nitrates and in no other, that 

 they can be dissolved by the soil mois- 

 ture and absorbed by the trees. It is 

 therefore obvious that this all-import- 

 ant nitrification requires the presence 

 of free oxygen (air), warmth and mois- 

 ture, and the only possible mode of 

 supplying this is by liberal and thorough 

 cultivation. 



There is another possible change 

 which might take place in uncultivat- 

 ed soils and is harmful. It has been 

 stated that, ordinarily, the bacteria 

 which causes nitrification require air. 

 There are, however, bacteria which can 

 cause organic matter to ferment in the 

 absence of free oxygen. Oxygen is 

 necessary for fermentation, and in the 

 absence of free oxygen these bacteria 

 obtain their supply by breaking up any 

 nitrates that may be present, using the 

 oxygen of the nitrate and allowing the 

 nitrogen of the nitrate to escape as a 

 gas. These bacteria are therefore very 

 injurious to the productiveness of soils, 

 since they destroy the valuable nitrates 

 and allow the nitrogen to escape, Their 

 effect is directly opposite to nitrifica- 

 tion, and hence it is called denitrifica- 

 tion. So it is again obvious that 



CULTIVATION IS VERY NECESSARY 



to admit free oxygen into the soil to 

 bring the valuable plant food into a 

 form that will make it readily avail- 

 able. Cultivation is also necessary to 

 prevent thedenitrificating bacteria from 

 obtaining the oxygen from the nitrates 

 and letting loose the valuable nitrogen 

 into the air. It is also necessary for 

 retaining the moisture that is in the 

 soil. Water is evaporated into the air 

 by means of fine hair-like tubes formed 

 in the soil and known as "capillary 

 tubes." These tubes are absolutely 

 necessary for bringing up moisture from 

 the subsoils, but if not checked, the 

 moisture will be lost, The only way 

 to check this loss is by cultivation. 

 The frequent breaking up of these tubes 

 means the minimising of evaporation. 

 Moisture in the soil is necessary for 

 two purposes. Available plant food can 

 only be taken up by the roots when 

 it is dissolved in the soil moisture, and 

 nitrification cannot take place without 

 moisture, so that insoluble plant food 

 cannot be made soluble without mois- 

 ture;, and without cultivation moisture 

 is not considered in the soil. 



Again, uncultivated, hard, compressed 

 land does not allow the rain to soak 

 into it, but the water, running over the 

 surface of the land, carries the vegetable 

 matter, fine particles of soil, the fertil- 

 ity brought to the surface by the 

 capillary action of the soil, the fertil- 

 ising elements brought down to the 

 soil by the rainfall, and the best of 

 the manures and fertilisers that may 

 be applied to the soil into water courses, 

 never to return. Each washing of the 

 surface makes the soil more compact, 

 thus adding to the surface flow of the 

 water and to the poorer conditions for 

 promoting the vigorous growth of plant 

 and tree. The injurious effect of such 

 conditions can be plainly seen in many 

 places, the trees being sickly, and bear- 

 ing small crops when they ought to be 

 vigorous, under favourable conditions 

 and in season bear abundance of fruit. 



The Remedy for Unfavourable 

 Conditions 

 of soil and waste of fertility is the 

 thorough cultivation of the soil, and 

 subsoil and under drainage. On clay 

 lauds having a retentive subsoil, culti- 

 vation is the first step to be taken in 

 providing the right condition for success- 

 ful tree growing. If the subsoil is so 

 hard and tenacious as to be what is 

 known as a "hard pan" so much the 

 more does it need to be cultivated to 

 a depth sufficient to si How the roots of 

 the trees to penetrate for food and 



