278 



CULINARY OR KITCHEN GARDEN. 



although the modus operamdi has been treated 

 by some as a science, still by far the greater 

 number of operators have acted upon the most 

 incorrect principles. 



Few superficial observers are perhaps aware 

 of the great difference in temperature between 

 thoroughly-drained soil and that in which super- 

 fluous water is allowed to lodge. Dr Liudley 

 asserts — and, we believe, from very accurately 

 made experiments — that the difference in sum- 

 mer is from 10° to 20°. The reason for this is, 

 that heat cannot be transmitted downwards 

 through water. " Thus neither the heat of the 

 sun nor the warm rain can penetrate to the 

 roots of plants in ill-drained land ; even boiling 

 water poured on the surface would have no 

 effect in warming soil on which cold stagnant 

 water naturally stands. Air also cannot reach 

 the roots of plants grown in soil of this nature. 

 It is as important to admit air to the roots of 

 plants as to their leaves — both extremities of 

 plants feed on air, the roots more than, the leaves." 

 — Lindley. Place ■■•^ plant in a situation where 

 air can get no access to its leaves, and they fall 

 off, to be followed by the decay of the stem : 

 roots, under the same circumstances, will gra- 

 dually shrink and die. The same high authority 

 elsewhere observes, that " many believe that the 

 whole advantage (of draining) consists in remov- 

 ing water ; but water is not in itself an evil — on 

 the contrary, it is the food of plants, and its ab- 

 sence is attended with fatal results. It is the 

 excess of water which injures plants, just as an 

 excess of food injures animals — with this differ- 

 ence, that animals can refuse what is hurtfal to 

 them, while plants have no choice, but must 

 take into their systems whatever is in contact 

 with the spongioles of their roots. The latter 

 are, therefore, more readily gorged than the 

 former. But undrained land is not merely wet; 

 it is water-logged. All the interstices between 

 the particles of earth being filled with water, air 

 is necessarily absent, except that small quantity 

 which is dissolved in the water. In this way 

 plants are deprived of the most essential part 

 of their food; but when the water is removed, 

 tlie air takes its place, and holds in suspension 

 aa much water as the roots can thrive upon ; for 

 it is not water in a fluid state that plants prefer: 

 it is when it has assumed a state of vapour that 

 they feed upon it best ; so that the removal of 

 water permits air, and air-borne vapour, the best 

 of all food for roots, to take place." 



As to the depth and the distance between the 

 drains, opinions are still, and, we believe, ever 

 will be, at variance ; the case must therefore be 

 as it has been— left greatly to the judgment of 

 the operator. The following very sensible re- 

 mark has been made by Mr Stephens, in " The 

 Book of the Farm," voL ii. p. 617, on this sub- 

 ject : " With our present experience, however, 

 I do not see the utihty of cutting drains as deep 

 as 6 or 8 feet, merely to extend the space be- 

 tween them, when perhaps the same effect might 

 be obtained by 3 or even 4 feet drains at nar- 

 rower intervals, unless very deep drains at very 

 wide intervals can be executed with more eco- 

 nomy. Experience has yet much to elicit in 

 regard to the distance that should be between 



sub-drains of different depths in different soils, 

 to effect the best results." 



Pulverisation. — Next in importance to render- 

 ing the soil dry by draining, is the process of 

 pulverising, which is effected by trenching, dig- 

 ging, grubbing, stirring, &c. The depth to which 

 this operation should be carried, must of neces- 

 sity depend on the soil and subsoil. Sir H. 

 Davy observes, " In rich clayey soils it can 

 scarcely be too deep ; and even in sands, unless 

 the subsoil contains some principles noxious to 

 vegetation, deep comminution should be prac- 

 tised. When the roots are deep, they are less 

 liable to be injured, either by excess of rain or 

 drought." Trenching has a most beneficial effect 

 on all soils of a depth consistent with the best 

 principles of horticultural culture, by reversing 

 the surface, and mixing and transposing the 

 whole mass operated on. It improves the tem- 

 perature of the soil, renders it capable of allow- 

 ing the rain-water to filter through it, and en- 

 ables the roots of plants to travel freely in search 

 of food. " By changing the surface, fresh soil is 

 exposed to the action of the weather; by chang- 

 ing the position of all the parts, new facilities 

 for chemical changes are produced ; and by 

 loosening the whole mass of the soil, air and 

 rain are more readily admitted. By loosening 

 soil, the air is admitted among its particles, and 

 confined there; and hence it becomes a non- 

 conductor of heat, and is consequently warmer 

 in winter, and cooler in summer, than if it 

 were in one firm mass. By the confinement 

 of air in the soil, the heat imparted to it by 

 the sun during the day is retained, and accu- 

 mulates in all free open soils to such a degree 

 as to raise their temperature over that of the air, 

 especially during night. From thermometrical 

 observations made at different places, it appears 

 that the mean temperature of the soil, at about 

 one foot below the surface, is somewhat higher 

 naturally than the mean temperature of the at- 

 mosphere on the same spot ; and hence we may 

 reasonably suppose that, by draining and pul- 

 verisation, the temperature of the soil may be 

 permanently increased, as well as that of the 

 atmosphere."— iSm6. Hort, p. 55. The atmo- 

 spheric air which becomes buried in the soil 

 during the process of trenching and deep-digging 

 — in the latter case in a less degree — becomes 

 decomposed by the moisture in the soil, and the 

 following chemical changes take place : " Am- 

 monia is formed by the union of the hydrogen 

 of the water with the nitrogen of the atmo- 

 sphere, and nitre by the union of the oxygen and 

 nitrogen. The oxygen may also imite with the 

 carbon contained in the soil, and form carbonic 

 acid gas and carburetted hydrogen." Heat is 

 given out during these processes ; " and hence," 

 as Dr Darwin, in " Phytologia," sect. 2, remarks, 

 " the great propriety of cropping lands imme- 

 diately after they have been comminuted and 

 turned over ; and this the more especially if 

 manure has been added at the same time, as the 

 process of fermentation will go on faster when 

 the soil is loose and the interstices filled with 

 air than afterwards, when it becomes compressed 

 by its own gravity, the relaxing influence of 

 rains, and the repletion of the partial vacuums 



