18 CIRCULAR NO. 116, BUREAU OF PLANT INDUSTRY. 



per acre, of which 95.1 per cent were marketable tubers. It has been 

 found that such varieties as Somer's Early, Early Rose, Early Man- 

 istee, and Burbank are not adapted to local conditions and produce 

 a tuber that is not marketable. Of the seedlings grown, about 10 

 seem to be very promising; the others have been discarded. 



METHODS OF IRRIGATION AND CULTIVATION OF POTATOES. 



The work on methods of irrigation and cultivation was carried on 

 in cooperation with the Office of Horticultural Investigations of the 

 Bureau of Plant Industry. Potatoes were planted on three dif- 

 ferent soils — alfalfa sod, stubble, and fallow land. On each of these 

 soils the following work was conducted in duplicate plats: Twelve 

 plats were deep cultivated and deep ditched for irrigation, and 12 

 plats were shallow cultivated and shallow ditched. In each case on 

 two plats alternate rows were irrigated throughout the season: on 

 two plats every other row was irrigated ; two plats were irrigated so 

 that the plants should never lack moisture: three check plats were 

 irrigated in alternate rows, but not until the plants showed actual 

 need of water. 



The largest yield was obtained on alfalfa land, where alternate 

 rows were irrigated under the shallow cultivation and ditching. In 

 all cases the alfalfa sod produced the largest yields and the stubble 

 land the lowest yields. The percentage of culls on the stubble land 

 ran from 50 to 75 per cent higher than that on the alfalfa sod. 



FIELD PEAS. 



Several varieties of field peas were grown in cooperation with 

 the Office of Forage-Crop Investigations of the Bureau of Plant 

 Industry. The highest yield was 23.5 bushels per acre, which was 

 produced by the variety S. P. I. No. 11200. The lowest yield was 

 11 bushels per acre. The average yield of the seven varieties was 

 16.0 bushels per acre. Unless higher yields can be secured it will not 

 be profitable to grow peas for feeding purposes on these high-priced 



irrigated lands. 



FALL IRRIGATION. 



During the past two years experiments have been conducted to 

 determine the value of irrigating land in the fall and letting it go 

 into the winter wet. The test has been applied to sugar beets., pota- 

 toes, wheat ; oats, barley, and corn (fig. 5). In both years the sugar 

 beets were a partial failure, owing to blowing out in the spring. The 

 first year the potato crop was a failure, due to diseases. 



The average yield of wheat on the fall-irrigated land was 3G.4 

 bushels per acre, as against 30.4 bushels on land not fall irrigated, 



[Cir. 116] 



