524 Circular No. 4. 



(2) Stable manure, either plowed in or topped dressed, as condi- 

 tions may warrant. Stable manure is more valuable for the humus 

 material it furnishes than for the amounts of plant food elements it 

 contains. The liquid part, however, contains a highly soluble and 

 available form of nitrogen which is lost by the leaching of manure piles. 

 A valuable addition to stable manure is made by mixing 40 to 50 pounds 

 of floats (ground phosphate rock) per ton of manure. Experience 

 has shown the least loss in fertilizing value of manure when the fresh 

 manure is hauled directly to the field and spread. 



(3) By green manuring, especially with the nitrogen-gathering legu- 

 minous crops, as clovers and vetches, 



B. Drainage 



There are large areas of land devoted to crops in this region which 

 are too wet for plant growth at some season of the year. Usually land 

 is too wet in spring and too dry in summer. Ordinary crops will not 

 grow in a soil saturated with water. 



Some important effects of drainage are: 



(j) Drainage improves tilth and granulation. 



(2) As a result of improved granulation a larger part of the rain- 

 fall is held in a form available to plants. This results in more moisture 

 being retained during the dry part of the summer. 



(j) Drainage by removing the excess of water admits air into the 

 soil. Air is essential to root growth. 



(4) In a well-drained soil as a result of the removal of the excess 

 of water and better aeration, plant roots strike deeper throughout the 

 season and thereby come in contact with a larger available supply of 

 water. 



(5) Wet soils are cold and late; drained soils are warm and early. 



(6) The air admitted as a result of good drainage promotes the decay 

 of humus and thereby increases the available food supply. 



(7) "Heaving" of soil is a sure indication that it is too wet. Drain- 

 age reduces or prevents " heaving." 



Drainage is accomplished in tzvo ivays: 

 (i) By open surface ditches or furrows. 

 {2) By covered ditches or tile drains. 



Open ditches have been used most generally, but are very ineflfective 

 in removing water and a troublesome and expensive interference with 

 tillage ancf harvesting operations. It is seldom that they are properly 

 graded, they quickly fill with weeds and rubbish, and they are generally 

 too shallow" to accomplish thorough soil drainage. They are expensive 

 because they must be so constantly repaired and because they occupy 

 a considerable area of land which should bear crops. 



Tile drains, on the other hand, have been demonstrated to be much 

 more efifective. As a rule, tile drains are carefully laid to an accurate 

 grade. They drain the soil deeply. They are a permanent improvement 

 when carefully constructed of gorvl. hard tile. They do not interfere 



