740 EXPERIMENT STATION RECORD. [Vol. 37 



vegetative parts, such as the stem and leaves. The utilization of the potash 

 and pho.sphorous fertilizers was materially influenced by the nature of the nitro 

 gen carrier, the most complete utilization being obtained in connection with 

 ammonium sulphate. The effect of liquid manure in this respect is favorable 

 on loam soils. 



The irrigation of potatoes, F. S. Harris {Utah Sta. Bui. 157 (/9J7), pp. 5-20, 

 figs. 9). — Rather extensive irrigation experiment.^ ^^^th potatoes conducted on 

 the Greenville Experiment Farm are reported for the 5-year period of 1912 

 to 1916, inclusive. The life of the potato plant was divided into four stages, 

 (1) when the vines were 4 in. high, (2) when the tubers began to form, (3) 

 when the potatoes were in full bloom, and (4) when the potatoes were nearly 

 ripe. One, 2i, 5, and 7i in. applications of irrigation water were made weekly, 

 and 5-in. applications at the different stages of growth. Important literature 

 on the sub.iect is reviewed and detailed tabular data pre.sented. 



A comparison of the yields of tubers and vines on plats receiving different 

 quantities of irrigation water weekly showed the highest average yield of 

 tubers for the 5 years, 337.1 bu., to have been obtained from a total of 12.8 

 in. applied 1 in. per week during the growing season. The maximum application 

 of 96 in., or 7i in. weekly, resulted in a lower average yield of tubers. 140.5 

 bu., than where no irrigation water wa-s given. 153.3 bu.. although the weight 

 of air-dry vines was nearly doubled. 



In a comparison of single applications at different stage.s of growth the 

 lowest yield of tubers, 139 bu. per acre, resulted from an application made after 

 planting and before the vines were up. The best results were secured from 

 applications made when the plants were in full blormi and averaged 229 bu. 

 per acre. Neither 10, 15, nor 20 in. applied in two, three, or four irrigations 

 of 5 in. each gave results equal to regular weekly applications of 1 in. each. 

 Late applications, as well as large quantities, of water increased the relative 

 growth of the vines. 



The average size of the tubers wa? larger where the water was applied 

 weekly with 1-in. applications, both 5 and 7i in. weekly applications producing 

 smaller tubers than where no irrig.ition water was u.sed. The tubers on 

 plats receiving water at the third and fourth stage and those receiving it at all 

 four stages averaged the same size and were larger than for any other treat- 

 ment. 



The average number of tubers per hill was largest with a 2J-in. application 

 per week, while early applications appeared to be conducive to a large pro- 

 duction of tubers per hill. 



The average weight of the hills, determined by weighing 100 average hills 

 from each plat, was highest with 1 in. and 2} in. weekly irrigations, while a 

 rapid decrease in weight per hill was note<l with an increase in the amount 

 of water applied. Applications made in the third stage proved most effective in 

 increasing the weight per hill. 



All irrigation treatments produced vines that were higher than those pro- 

 duced with no irrigation, but a comparison of the vine growth is deemed in- 

 sufficient as an indication of the relative value of the different irrigation treat- 

 ments. A wide variation in the color of the vines was noted for the different 

 methods of irrigation and was considered a reliable means of determining 

 the moisture requirements of potato plants. 



The experiments are held to indicate the importance of an even supply of 

 moisture during the middle portion of the life of the potato, after the tubers 

 begin to form and before they begin to ripen. 



Shallu, or " Egyptian wheat," a late-maturing variety of sorghum. B. E. 

 RoTHGEB (17. S. Dept. Agr., Farmers' Bui. S27 (1917), pp. S, figs. 5).— Shallu Is 



