UNDERDRAINING. 159 



The union of the elements where combination makes the atmos- 

 phere, coming thus in contact with the combined elements that 

 make the soil, produces a change favorable to the growth of 

 plants. This accounts for the increased productiveness of re- 

 cently drained soil. Latent elements are thus fitted to become 

 the food of the growing crop. 



Rain-water is a natural fertilizer, provided it can circulate 

 through and not stagnate in the soil. The introduction of 

 water, says Liebig, is an introduction of alkalies. If so, then it 

 is the cheapest liquid manure the farmer can seize upon. It 

 not only fertilizes, but warms, and cleanses the soil from nox- 

 ious and deleterious elements, carrying them into the drains, 

 by which the power of soils to absorb aqueous vapor, whether 

 in the form of dew or mist, is greatly increased and made much 

 more productive. 



Says Sir Humphrey Davy : " The power of soils to absorb 

 water from air, is much connected with fertility. When this 

 power is great, the plant is supplied with moisture in dry 

 seasons ; and the effect of evaporation in the day is counter- 

 acted by the absorption of aqueous vapor from the atmosphere, 

 by the interior parts of the soil during the day, and by both the 

 interior and exterior during the night." Soils most finely 

 comminuted, if underdrained and deeply tilled, are most favor- 

 able to this action. 



Thus it is shown what drainage is, what it does, and there- 

 fore, why it should be introduced especially into tenacious soils. 

 It removes stagnant water, and renders the soil porous. It 

 removes the sources of evil and is the occasion of good by 

 opening the interstitial canals of the soil for the reception of air 

 and healthful moisture. 



If you would drain tenacious clay soils effectively, reference 

 must be had to the season, as well as to the depth and nearness 

 of the parallel drains, and the main or discharging drain. The 

 best time is in the summer, when the weather is dry. The 

 drains, after they are opened, should remain a few days before 

 the pipes are laid, and the ditch refilled. Such soils are usu- 

 ally of greater intrinsic value than sandy soils, and require 

 more skilful treatment to make them produce well, especially 

 in the art of draining. 



