174 



THE IRRIGATION AGE. 



DRAINAGE OF FARM LANDS. 



Results of Careful and Extended Investigations by the Govern- 

 ment for the Benefit of the Farmers. 



BY C. G. ELLIOTT, 

 Expert in Drainage and Irrigation U. S. Department of Agriculture. 



"In the cultivation of retentive soils," says Waring, 

 "drainage is the key of all improvement." 



Farmers frequently desire an improvement in 

 methods and in the general management of their lands 

 without being sufficiently informed regarding the 

 specific changes that will be necessary to bring it about 

 or clear in their minds as to the profits that would 

 accrue should such changes be made. When a farmer 

 finds his land too wet for cultivation, he admits the 

 necessity of drainage for the time being, but often 

 hopes that the following season may be more favorable 

 which hope is frequently realized and so takes the 

 loss as one of the contingencies of the industry. He 

 waits in the spring for slow natural drainage and evap- 

 oration to relieve his land of the surplus water and per- 

 mit the sun to dry and warm the soil sufficiently for 

 the reception and germination of the seed, when by the 

 aid of drainage the seeding could be done a week or ten 

 days earlier. The injury resulting to crops growing 

 upon land imperfectly drained when the season is not 

 the most favorable is frequently taken as unavoidable 

 one of the vicissitudes of farming rather than a loss 

 to be prevented by the use of well located and con- 

 structed drains. 



Facts which are easily discerned by the casual ob- 

 server have pressed the subject of drainage home to 

 both practical farmers and non-resident landowners in 

 a most emphatic way. Those who have gone ' further 

 into the subject of soil improvement by drainage have 

 discovered greater advantages and more surprising ben- 

 efits than were formerly thought possible. It is con- 

 ceded to be a necessary accompaniment of scientific ag- 

 riculture, and our most progressive farmers have taken 

 advantage of it to a greater extent than is generally 

 supposed. It is an improvement applicable to all land 

 not possessing natural drainage, and hence is required 

 for the attainment of the best results from some of our 

 most fertile land. The farmer, when convinced that it 

 will be to his interest to construct some kind of a drain- 

 age system for the improvement of his soil, desires to 

 know how to plan and perform the work in an effective 

 way at an expense not exceeding the limit of profitable 

 returns which can reasonably be expected. He will find 

 it an advantage to have an intelligent idea of the theory 

 as well as of the practice of drainage in order that he 

 may adapt his work to the several varieties of soil and 

 conditions with which he lias to deal. 



NATURE OF A DRAINED SOIL. 



A drained soil is one which is moist but not sat- 

 urated with water. Soils used for the production of the 

 plants most prized by the farmer, gardener, or fruit 

 grower must, in addition to other necessary elements, 

 contain a certain percentage of water in order to yield 

 the largest possible returns. This is usually termed 

 "moisture," and soils in which the proper percentage 

 of moisture exists are commonly called "dry soils," to 

 distinguish them from those containing a surplus of 

 water, which are called "wet soils." The farmer, there- 

 fore, in speaking of a "dry" soil does not mean one 

 which is devoid of water, but one which does not con- 



tain enough water to hinder or prevent the growth of 

 his plants, while the term "wet" indicates one that con- 

 tains more water than is needed, the presence of which 

 prevents the plants from reaching their greatest per- 

 fection. A perfectly dry soil is dead, and is worthless 

 for producing crops. A soil which is completely satu- 

 rated with water will produce nothing but aquatic 

 plants and hence is worthless for cereals and other valu- 

 able products. 



Plants take their nutriment from the soil in liquid 

 form only, it having been prepared by the action of 

 heat and moisture on the elements present. An excess 

 of moisture reduces the temperature, excludes the air, 

 and dilutes the plant food, thus retarding or entirely 

 stopping the growth of the plant as effectually as a lack 

 of moisture. 



MECHANICAL MAKE-UP OF SOILS. 



Soil is made up of exceedingly fine particles of ir- 

 regular shapes, varying composition and different prop- 

 erties. It is formed by the breaking down of rocks of 

 different composition which are disintegrated by the 

 weather, ground up and distributed by glacial action 

 and floods, and mixed with the products of successive 

 ages of vegetable growth. These particles as they ap- 

 pear under the microscope are rough and irregular, 

 some of them being exceedingly small. The differences 

 in size of the particles of ordinary soils (exclusive of 

 gravel, pebbles, etc.) are illustrated in the following 

 classification usually adopted in the mechanical analysis 

 of soils : 



COMPARATIVE DIAMETERS OF SOIL PARTICLES IN DIFFERENT SOILS. 



Inch. 



Coarse sand 0.04 to 0.02 



Medium sand 02 to .01 



Fine sand 01 to .004 



Very fine sand 004 to .002 



Silt 002 to .0002 



Clay ..." 0002 and less. 



The peculiar shapes of soil particles as they appear 

 under the microscope are shown in Figs. 1 and 2. Here 

 it is shown that the particles of sand are not less than 



FIG. 1. Soil paiticles magnified 

 162 times.* 



FIG. 2. Silt particles fiom sub- 

 sjil magnified 225 times.* 



200 times larger than the particles of clay. 



As the soil particles can not lie together so as to 

 form a solid mass, there is a large amount of inter- 

 vening space, which in an average soil equals nearly 

 half its volume. The smaller the particles the greater 

 the proportion of space. Thus clay contains 65 per 

 cent of space, while a sandy truck soil contains 37 per 

 cent, ordinary soils varying all the way between these 

 extremes. 



As a result of a force which is known as surface 

 tension, each particle of soil holds a film of water over 

 its entire surface and thus provides a supply of this 

 material for the roots of the plant. When the quantity 



*l''rom Bulletin No. 187 issued by U. S. Dept. of Agriculture. 



