96 Commercial Gardening 



3. MECHANICAL ANALYSIS OF SOILS 



Besides an examination of the natural vegetation referred to at p. 90 

 the experienced plant -grower will also make a physical or mechanical 

 examination. He will handle the soil, feel its texture, noting its colour 

 and whether its particles cleave together or fall asunder and crumble 

 into dust; and if he is wise he will also have a good-sized hole dug out 

 to a depth of 3 or 4 ft. so that he may see the geological formation. 

 He will then be able to form a good opinion as to what may be done with 

 the land. If the vertical section of the hole shows a good depth of yellow 

 loam resting on sand, gravel, or chalk it is a good sign. Such a soil will 

 contain plenty of plant food, may be easily, deeply, and economically 

 worked, will not require large quantities of manures, will not be too dry 

 or too hot in summer, nor too cold or too wet in winter, and will respond 

 readily to good cultural practice. 



It follows that any other soil which does not approach this ideal is 

 less valuable and may cost a good deal more to cultivate. 



To gain a fairly accurate idea as to the physical condition of a soil 

 a fair sample of it should be taken from the first, the second, and the 

 third spit down. A cubic foot of each might be taken and weighed. 

 This multiplied by 43,560 will be the weight per acre. A certain quantity 

 of soil, say 10 oz., should be spread out and allowed to dry in the sun 

 and air. Weigh again, to see how much moisture has escaped, and com- 

 pute the amount per acre. After air-drying and noting the amount of 

 water given off, the samples should then be baked over a fire until all 

 the organic material is driven off by combustion into the atmosphere. In 

 this way the carbon, oxygen, hydrogen, and nitrogen will be liberated, and 

 the residue will represent the mineral substances which cannot be further 

 reduced. Then pass each sample through a sieve with an -in. or -in. 

 mesh, so as to take out all the larger stones. Weigh these also and 

 compute for the acre. The finer soil left should be mixed with water 

 in a glass vessel and well churned up with a stick; hot water will free 

 the finer particles better from the sand and gravel than cold. All the 

 fine clayey particles will remain suspended in the water and make it 

 muddy, while the sand and grit will fall to the bottom. By pouring 

 off the muddy water time after time, until at last the water is quite 

 clear, the mud or clay will be separated from the sand. Allow to settle, 

 pour the water off carefully, and when sand and clay are dry they can 

 be weighed. The result will show the proportion of each in the sample, 

 and the weight may be computed for the acre. 



The weight of a cubic foot of soil of various kinds in a dry and 

 wet state, and the amount of water each contains, have been computed 

 >ias follows by M'Connell in his Notebook of Agricultural Facts and 

 Figures: 



