140 



THE GAKDENER'S ASSISTANT. 



air and water. Hence, so far as humus is bene- 

 ficial to vegetation, it is only by its oxidation 

 and nitrification, and a consequent supply of 

 carbonic acid within the soil — a source of im- 

 mense importance in the early stages of the 

 life of a plant, and before it has developed and 

 exposed a sufficient amount of green leaf-surface 

 to the atmosphere to render it independent of 

 soil supplies of carbonic acid. It is estimated 

 that the annual production of nitrates within 

 the soil ranges from seventy to eighty pounds 

 of nitrogen per acre in the case of good loamy 

 soils, but the capacity for producing nitrates 

 possessed by a fertile garden soil or leaf -mould 

 containing much organic matter (humus) far 

 exceeds that of ordinary loams. 



The following analysis by J. Hughes, F.C.S., 

 represents the composition of a good grape soil 

 from the neighbourhood of Motril, in the south 

 of Spain, and the results will be useful to those 

 interested in the production of grapes : — ■ 





Per cent. 



Water lost at 212° Fahr., 



.. 0770 



* Organic matter and combined water,. 



.. 2-220 



Oxide of iron, 



.. 4-678 



Alumina, ... 



.. 2-462 



Lime, 



.. 1019 



Magnesia, ... 



.. 0-684 



Potash, 



.. 0-266 



Soda, 



.. 0010 



Phosphoric acid, ... 



.. 070 



Carbonic acid, 



.. 0-440 



Sulphuric acid, 



trace 



Chlorine, ... 



.. 0-008 



t Silica and insoluble silicates, ... 



.. 87-373 





100 000 



* Containing- nitrogen, 



.. 0-045 



f Containing coarse sand, 



. 44-360 



Stones left on ^-inch mesh sieve, 



.. 32-07 



Gravel left on ^-inch mesh sieve, 



.. 15-74 



Total stones, 



4781 



The soil, as the figures show, consisted largely 

 of stones, there being in round numbers 48 per 

 cent of small stones and gravel having a light- 

 brown ferruginous appearance. The above re- 

 sults certainly indicate a really poor soil when 

 compared with our English soils of average fer- 

 tility. Thus, in the proportions of nitrogen and 

 phosphoric acid the amounts are quite one-half 

 what we should find in a native soil of average 

 quality ; but in regard to potash this soil stands 

 out prominently in richness, and there can be 

 little doubt that one of the greatest qualifica- 

 tions for a successful vine-producing soil must 

 be the presence of plenty of potash in a readily 

 available form. The distinguished French 

 chemist Ville, in his book on manures, lays 



particular stress upon the importance of potash 

 for vines. He says: "Where potash is lacking 

 the leaves do not attain their full development; 

 in the month of July they become red and 

 spotted with black, after which they become 

 dry, and are easily reduced to powder under 

 pressure of the fingers". Further, he adds: 

 "If potash be deficient, little or no fruit makes 

 its appearance ". 



The next soil to which we would direct atten- 

 tion is one specially prepared for the cultivation 

 of the Carnation. The available condition of 

 the plant-food depends much on the character 

 of the soil ; a much smaller proportion of plant- 

 food will render a sand fertile than would be 

 required in the case of a clay. This is partly 

 from the far greater development of the roots 

 in a sandy soil, and partly from the different 

 condition in which the mineral food is held. 

 Hilgard has also pointed out that the presence 

 of lime in a soil, especially when associated with 

 humus, much increases the availability both of 

 the potash and phosphoric acid, so that smaller 

 quantities of these suffice when lime is present 



Percentage Composition of Soils prepared for Carnation 

 Growing. 





Sample 1. 



Sample 2. 





per cent. 



per cent. 



Sand, 



79-924 



79-909 



* Organic matter (humus), 



12-582 



11-302 



Oxides of iron and alumina, 



5-220 



5-358 



Carbonate of lime, 



1-037 



2-382 



Magnesia 



0-259 



0-187 



Phosphoric acid, 



0-369 



0-349 



Sulphuric acid, 



0-076 



0-065 



Potash, 



0-256 



0-206 



Soda, 



0112 



0-096 



Chlorine, loss, &c, 



0-165 



0-146 



Total, 



100-000 



100-000 



* Containing nitrogen, 



0-386 



0-405 



Equal ammonia, 



0-469 



0-492 



We thus see that sand and organic matter 

 make up about 90 per cent of the total soil thus 

 prepared, with 5 per cent of oxides of iron and 

 alumina, which would consist of a loamy clay, 

 so that this leaves only 5 per cent to be divided 

 among the other ingredients, showing conclu- 

 sively that the proportion of plant-food present 

 in soils is very small, even when the soil is ex- 

 tremely fertile, the bulk of the soil serving 

 chiefly as a support, and like a sponge to hold 

 water. The percentage of nitrogen in the car- 

 nation soils is very large, but it is found, never- 

 theless, that if the plant is to be grown success- 

 fully it must be assisted with some nitrogenous 

 manure of a readily soluble character. This is 

 owing to the fact that a large part of the ele- 



