10 



BULLETIN" 1087, U. S. DEPAETMEISTT OF AGRICULTURE, 



number of plants of the same alfalfas. The roots taken in October, 

 1916, and May, 1917, were from the central portion of 8-rod rows; 

 the roots taken in August, 1919, were from the north ends of the rows 

 and those taken in October, 1919, were from the south ends. Data, 

 unless otherwise stated, were obtained on the first 18 inches of root. 

 This portion of the work was concluded in 1919. It was later found 

 desirable to include data comparing southern-grown common and 

 Grimm with plants of the same age of the prostrate and decumbent 

 forms of pure Medicago falcata. In the fall of 1920, after grow- 

 ing six seasons, plants were removed from the nursery. No appar- 

 ent mortality had occurred among the yellow-flowered plants from 

 the time they were planted in May, 1915, to September, 1920. Only 

 a 5 per cent mortality occurred in the Grimm variety, although some 

 of the surviving plants showed winter injury. ^ In the southern - 

 grown common, 40 per cent of the plants had been killed or very 

 seriously injured. All plants of Medicago falcata had pure yellow 

 flowers and there were no evidences of hybridization. 



CONDITIONS UNDER WHICH VARIETIES WERE GROWN. 



^oot studies were conducted from 1916 to 1919 upon varieties of 

 alfalfa sown May 24, 1916, in drilled rows 36 inches apart and under 

 similar soil conditions. The alfalfas studied in September, 1920. 

 were sown in 42-inch rows in May, 1915. The only treatment to 

 which these rows were subjected was clean cultivation throughout 

 the season and the burning off of the dead stems in the early spring. 

 The soil is fertile, well drained, and well supplied with organic 

 matter and nitrogen-fixing organisms. In order to determine the 

 character of the soil, a trench was opened in the alfalfa nursery in 

 October, 1916, and samples taken at various depths and sent to the 

 Bureau of Soils, United States Department of Agriculture, where 

 a mechanical analysis and determination of calcium carbonate were 

 inade. The results obtained are shown in Table 3. 



Table 3. 



-Jlechauicai analyses and determination of calcium carbonate in rep- 

 resentative soils at the Redfield Field Station, S. Dak. 



JDepth from 



which soil 



sample was 



taken.i 



Description. 



tol foot ' Silty clavloam... 



1 to 4 feet 1 Clay . .. . ." 



4 to 5 feet Silt loam 



5to8feet Clay 



8 to 10 feet do 



Constituents (per cent). 



Lime 



(CaCOa). 



0.25 

 13.63 

 11.45 

 6.97 

 6.31 



Fine 



gravel, 



2 tol 



mm. 



Coarse 

 sand, 



1 to 0.5 

 mm. 



0.3 

 .1 

 1.0 





 



Medium 

 sand, 

 0.5 to 

 0.25 

 mm. 



0.4 

 



.4 

 

 



Fine 

 sand, 

 0.25 to 

 0.10 

 mm. 



11.6 



1.1 



1.0 



.2 



1.2 



Very 

 fine 



sand, 



0.10 to 



0.05 



mm. 



13.1 



1.9 



2.2 



.3 



1.0 



SUt, 



0.05 to 



0.005 



mm. 



52.1 

 24.7 

 81.4 

 33.5 

 21.6 



Clay, 

 0.005 

 to 

 mm , 



22.1 

 72.2 

 13.2 

 66.0 

 76.1 



^ Samples, as listed in the table, are averages for the depths stated. 



