November, 1909.] 



438 



Scientific Agriculture. 



will contain as high as 190 pounds of 

 water. In other words, the soil of a 

 garden, rich in humus, will contain 

 nearly four times as much moisture as 

 sandy soil devoid of humus. 



Not only is the soil rich in humus a 

 better container of moisture, but it is 

 also a better retainer. Experiments 

 show that 88 per cent, of the moisture 

 in sandy soils will evaporate in four 

 hours in hot dry weather such as is 

 usually experienced in arid countries. 



In garden loam, reasonably rich in 

 humus, only 21 to 25 per cent, will eva- 

 porate in that time. In other words, 

 the garden loam will contain almost 

 four times as much moisture as the sand 

 bank and retain it almost four times 

 as long. Since evaporation may be 

 hindered by establishing a dirt mulch, 

 and since a dirt mulch is more easily 

 established in a mellow soil, rich in 

 humus, it can be seen how valuable 

 organic matter is to the soil in semi-arid 

 regions. 



In addition to the above, humus causes 

 the water in soils to rise nearer to the 

 surface. Experiments show that farm- 

 yard manure will strengthen the capillary 

 rise of soil moisture. King tells of an 

 experiment where it was found that the 

 surface foot of one acre of manured soil 

 contained over one per cent, more mois- 

 ture than the same soil unmanured. This 

 proves that the moisture in soils rich in 

 humus rises to the surface. This experi- 

 g ment showed that there were over 15 

 tons more moisture in the surface foot of 

 an acre of manured land than in the 

 same soil unmanured, while there were 

 nearly 7 tons less moisture in the fifth 

 foot below the surface of the manured 

 soil than the unmanured soil. The 

 humus brought the moisture up where 

 the crops could use it. Not only then 

 does the soil rich in humus contain and 

 retain more moisture, but it places the 

 moisture where it will most benefit the 

 crop. 



Every farmer knows that the above is 

 true. He knows that the garden plot 

 will be moist long after the clay bank 



has dried out and become so hard that it 

 cannot be ploughed. The reason lies in 

 the fact that the garden contains a 

 greater amount of humus, and will con- 

 tain more moisture and keep it longer 

 than the clay bank will. Therefore, the 

 farmer, who would make it possible for 

 his crops to get moisture longer in a dry 

 time should increase the supply of humus 

 or organic matter in the soil. 



6. Then, too, organic matter makes 

 the soil warmer. This may not seem 

 important in southern soils, but never- 

 theless it is beneficial. It is especially 

 important in the germination of the 

 seed of early crops. The soil that will 

 warm up first in the early spring will, 

 in the majority of cases, make the 

 farmer a larger profit than the soil that 

 is backward about becoming warm. 



Humus makes soils warmer for two 

 reasons. First, it makes them dark in 

 colour ; there the soil will absorb more 

 heat than the lighter-coloured soils. 

 Black, well-drained soils will warm up 

 earlier in the spring than light-coloured 

 soils. Second, the decay of the humus 

 warms the soil. Wherever vegetable 

 matter decays, there is a certain amount 

 of heat generated. Consequently, those 

 soils that contain a great deal of decay- 

 ing humus will be warmer than the soils 

 without humus. The decay of any 

 substance is, after all, nothing more or 

 less than slow burning. When anything 

 burns it produces heat. That humus 

 warms every soil the farmer is aware. 

 Compare the garden plot in early spring 

 with the clay bank, and you can soon 

 tell that the garden plot is ready to 

 germinate seed several days before the 

 clay bank. 



7. Humus decreases the weight of 

 soils. That is, it makes soils lighter 

 and more easily cultivated. Rich garden 

 soils weigh about 70 pounds per cubic 

 foot ; clay soils about 90 pounds. The 

 lighter the soil the easier it is to culti- 

 vate and less liable it is to pack. It is 

 more easily cultivated to establish the 

 much-needed dirt mulch and to enable 

 the plant to send its roots deep down 

 into the soil. 



