NURSERY PRACTICE FOR PRAIRIE-PLAINS PLANTING 59 



be used, a pump of less pressure is needed than in a set-up in which 

 irrigation is done by means of an overhead sprinkling system equipped 

 with oscillators. Oscillators work best at pressures of 30 to 45 

 pounds, and function poorly or fail entirely when the pressure drops 

 below 20 pounds at the point where the water enters the oscillator. 



It is strongly recommended that, before final decision is made on 

 the well location and depth, one or more test wells be dug under the 

 supervision of a driller, preferably working under contract. The test 

 will include an exact log of the hole, foot by foot, as recommended by 

 Brackett and Lewis (4), to indicate character of the substrate, depth 

 of water-bearing sand, and other pertinent data such as capacity and 

 flow of the well and amount of draw-down for different discharge 

 rates. The test will be used as a basis for recommending the type 

 and capacity of the pump. 



Before purchasing a pump, the buyer should become thoroughly 

 familiar with the rating charts provided for each pump by the manu- 

 facturer. These charts show maximum working pressure developed 

 and gallonage delivered at various heads, although it is best to deduct 

 30 percent from all claimed capacities for everyday working con- 

 ditions. The data often include the horsepower necessary to furnish 

 a specific flow of water at a given head and lift and give the speed in 

 rotations per minute of the pump, as well as maximum and effective 

 suction lift. Economy of operation and upkeep are additional factors 

 for the buyer to consider. 



PUMPING FROM SHALLOW WELLS OR OPEN WATER 



Considerable expense can be averted in installation cost if the 

 nursery lies in an area where there is a large permanent supply of 

 good water within 10 to 50 feet of the surface. Such areas on the 

 plains are invariably underlain by sand or gravel substrates and 

 usually occur as terraces along streams or in the beds of old glacial 

 lakes. In some places pumping can be done from a lake or stream, 

 provided the entire flow of the stream is not already appropriated. 

 Careful investigation should be made of legal priorities and water 

 rights on such streams. 



If the nurseryman is not familiar with the ground-water conditions 

 and depths in a given locality, valuable advice can be obtained from 

 an hydrologist or geologist familiar with the area. 



Where the water table is within 10 to 30 feet of the surface and 

 the water-bearing strata consist of sand or gravel, one of the most 

 economical units is a horizontal centrifugal pump set down in a well 

 pit so that it is within 5 to 10 feet of the surface of the water, which 

 is drawn either through sand points, well screens, or strainers (fig. 12). 

 If the water table fluctuates more than 10 feet, however, the water 

 table at the low water stage, after prolonged pumping, may be below 

 the effective suction lift of the pump. Although centrifugal pumps 

 have a suction lift up to 20 or 25 feet, they work much more efficiently 

 when placed closer to the water. 



For priming, it is good policy to have the discharge pipe sloping 

 upward from the pump, with a cut-off valve at the lower end. When 

 the valve is opened the water retained in the pipe primes the pump. 



