

SOIL OF THE WOODED SWAMPS. 



851 



which boar a forest of black gum, cypress, and red maple (PI. LXVII). 

 In places the beds reach a thickness of 3, or even, according to Prof. 

 ■N. B. Webster, 1 of U meters (10 to 15 feet). The color is black. 

 Decomposition has here progressed further than in the "juniper" 

 deposits, and the black gum type is to lie regarded as a form of humus, 

 rather than of peat. When cleared and drained, black gum lands 

 afford a rich, mellow top soil, which differs markedly from the stub- 

 born juniper lands in being tractable and easily worked. 



The following arc determinations of the percentage of organic or 

 combustible matter in such soil at each of three depths: 



Per cent organic matter in soils. 



Depth. 





rm. 



()- 



50 



in. 



n- 



20 



cm. 



50 



100 



in. 



20- 



in 



cm. 



100-150 



in. 



40- 



ISO 



*-;,. ,;„ Soil culti- Soil culti- 

 ifs vated20 vatedft) 



years. years. 



1 

 1 



13. 10 



: 



3.30 



; 



1.90 



6.90 

 2.40 



I in 



5 in 

 2.10 

 I 00 



This table shows that the largest part of the organic matter occurs 

 in the upper 20 inches and that it decreases in amount for eacli suc- 

 ceeding 50 centimeters (20 inches) in depth. It furthermore shows, as 

 one would naturally suspect, that the virgin soil contains more organic 

 matter than that under cultivation, and that the longer the time of 

 cultivation the smaller the content of organic matter. This holds true 

 for each of the three depths, although the maximum change is in the 

 upper 20 inches. Yet, even where cultivation lias been continued for 

 fifty years, the soil still has enough organic matter to give it a black 

 color. In some places this black color extends into the second 20 inches, 

 but is usually absent, the second and third 20 inches being ordinarily 

 of a yellowish color. This abundance of organic matter is of great 

 importance since it (1) furnishes a large amount of nitrogenous plant 

 food, (2) increases the water-holding capacity of the soil, and (3) by 

 its black color increases the power of the soil to absorb heat. The 

 increased power to absorb heat is no doubt more than overcome by 

 the cooling tendency of the increase in water content, due to the 

 organic matter. From the standpoint, of the early trucker this reduc- 

 tion in temperature would be a serious objection, because it would 

 retard the maturity of his crops and throw them on the market when 

 prices are usually much reduced. Aside from this objection, how- 

 ever, the organic matter is of great value. 



ACIDITY. 



The virgin soil is invariably very acid, doubtless because of the 

 enormous accumulation of vegetable matter and the consequent 



Am. Naturalist, vol. !), p. 260 (1875). 



