526 ANNUAL KEPOHTS OF DEPAETMENT OF AGRICULTURE. 



inaimfactiirci of clav drain tile was mado, and tlio manuscript for a 

 l)ullotin on this siil)joct was propar<>d. The scarcity and high cost 

 of hibor has mado hand ditching very expensive, and in some instances 

 it has been foimd advisable to use explosives in constructing ditches 

 which formerly would have been dug by hand. An investigation of 

 the use of tlynamite in the construction of drainage ditches is now in 

 progress. The manuscript for a bulletin containing the results of 

 investigations of pumping plants in southern T^ouisiana was com- 

 pleted. This bulletin presents the data relative to pumping plants 

 that have been collected during the past 10 years in soutiiern Louis- 

 iana. Farmers' Bulletin No. 698, Trenching Machinery for Tile 

 Drain Construction, was revised and issued as P'armers' Bulletin 

 No. 1131. Department Bulletin No. .300, Plvcavating Machinery 

 Used in Land Drainage, has also been revised and brought up to 

 date. An investigation of vertical drainage was completed and a 

 manuscript for a Farmers' Bulletin on the subject is in preparation. 



Investigations of the problems relating to the control of erosion 

 were continued as opportunity offered, and considerable material 

 was collected for a Farmers' Bulletin on soil-saving dams and other 

 devices for controlling gullying. Farmers' Bulletin No. 997, Terrac- 

 ing Farm Lands, was reprinted in revised form. 



vStudies of the subsidence of muck soils after drainage were contin- 

 ued in Louisiana and in Florida. The investigation of the optimum 

 depth of drainage for muck soils was continued in Florida. 



Investigations in regard to the effect of depth of drain and distance 

 between drains in tile drainage were continued. The investigation 

 at Tarboro, N. C, was completed and a report prepared. Similar 

 studies on another type of soil were made in Pitt County, N. C, and 

 A'aluable data secured. 



An investigation to determine the rate of run-off from tile-drained 

 areas and the hydraulic factors that govern flow in large tile drains 

 was begun in southwestern Minnesota in the spring of 1920 and is 

 now in progress. An agreement was entered into with the commis- 

 sioner of drainage and waters of the State of Minnesota which provides 

 for cooperative hydraulic investigations on drainage ditches in the 

 northwestern part of the State. The objects of these studies are to 

 determine the rates of run-off that shoidd be provided for in that 

 territory, and to ascertain the proper value for the coefficient of 

 roughness (rO in the Kutter formula. These investigations are now 

 in progress. 



Investigations were started and are now in progress in the south- 

 western part of Minnesota to determine the extent and concentration 

 of the alkalies that have caused the failure of a number of concrete 

 tile drains in that section. The ffuestion of whether or not it is safe 

 to use concrete tile in that part of the State is an exceedingly import- 

 ant one, as drainage districts have been organized which propose to 

 construct tile drains which will cost several million dollars. Con- 

 crete tile has been the tile most used, and it is desirable to determine 

 definitely the conditions under which the tile now manufactured can 

 be safely used, and if possible to devise methods of improving the 

 fjuality of the tile so tnat it will be more resistant to the action of 

 alkalies present in the soil. The results of the investigation during 

 the year were presented in a progress report that has been issued in 

 mimeographed form. 



