BULLETIN 976, U. S. DEPARTMENT OF AGRICULTURE. 



PHYSICAL FACTORS. 



The more important physical factors which usually influence crop 

 production are (1) the soil, (2) the annual and seasonal rainfall and 

 its distribution, and (3) the seasonal evaporation and temperature. 



The soil at the Amarillo Cereal Field Station is a dark clay loam, 

 which is known on the Plains as ''tight" land. It bears a close turf 

 of buffalo and grama grasses. The soil is productive, which results 

 in high yields when the moisture is distributed so that crops can make 

 proper use of it. 



RAINFALL. 



Precipitation and its distribution probably are the prime factors in 

 crop production in the section of the Plains in which the Amarillo 

 Cereal Field Station is located. There is usually moisture enough to 

 grow a crop, but it is not always so distributed that the crop can make 

 the best use of it. When it is not, crop yields are low, and in extreme 

 cases total failures result. 



MONTHLY AND ANNUAL PRECIPITATION. 



Table I shows the monthly, annual, and mean annual precipitation, 

 in inches, at Amarillo, Tex., during the 28-year period from 1892 to 

 1919, inclusive. The mean annual precipitation at Amarillo for 

 these 28 years was 20* inches, of which 15-f inches fell during the 

 growing season, or from April to September, inclusive. 



Table I. — Monthly and annual precipitation at Amarillo, Tex., during the 28-year 

 period from 1892 to 1919, inclusive. 



[Data (in inches) furnished bv the observer of the United States Weather Bureau at 



T.=trace.] 



\marillo, Tex. 



Year. 



Jan. 



Feb. 



Mar. 



Apr. 



May. 



June. 



July. 



Aug. 



Sept. 



Oct. 



Nov. 



Dec. 



An- 

 nual. 



Mean 

 an- 

 nual. 



1892 



0.42 

 .09 

 .02 



1.60 

 .76 



2 26 

 .86 

 .29 

 .59 

 .03 

 .04 

 .12 

 .16 



1.00 

 .41 



1.11 

 .26 

 .07 

 .05 

 .13 

 T. 

 .11 

 .06 

 .72 

 .36 

 .69 



1.01 

 T. 



0.57 



2.03 



1. 15 



1.92 



.41 



.65 



.82 



.07 



.47 



.48 



T. 



2.93 



.08 



1.52 



.51 



.24 



.72 



.22 



.17 



2.88 



1.94 



55 



.10 



1.60 



.02 



.22 



.26 



.73 



2.10 

 T. 

 .05 

 .16 

 .21 

 .47 

 .36 

 .17 

 .48 

 .02 

 .74 

 .26 

 T. 



2.62 

 .64 

 .02 

 T. 



1.20 

 .34 

 .50 

 .82 

 .59 

 .15 



1.00 

 .57 

 .25 



1.06 



1.73 



0.21 



.16 



.85 



1.31 



1.95 



1.08 



.98 



.23 



5.47 



4.90 



1.83 



.90 



.63 



4.52 



3.23 



1.25 



1.90 



.50 



.59 



2.76 



.72 



1.76 



.95 



5.05 



1.71 



.71 



.48 



2.56 



2.70 



2. 19 

 1. 30 



1. 78 

 2.20 



4. 44 

 3.52 



3. 12 

 4.53 

 5.99 

 9. 14 

 1.79 



2. 88 

 6. 16 

 1. IS 



.99 

 3.55 



1. 08 



2. 99 



5. 88 

 1.67 

 1. 41 



4. 43 



1. 70 

 .89 



2. 49 

 2. 23 

 2. 08 



1.49 

 2.03 

 3.59 

 6. 84 

 2.31 

 2. 32 

 4.81 

 4.45 

 1.84 



.92 

 2.01 

 2. 83 

 5. 53 

 2. 19 

 2. 07 

 1.97 

 1.75 

 4.72 



.66 



.20 

 1.90 

 2.32 



.84 

 1.04 

 2.18 



.83 

 1.43 

 2.94 



1.85 

 2.05 

 1.82 

 2. 08 

 7.04 



2. 16 



3. 88 

 6.96 

 3. 21 

 1.66 



1. 45 

 3. 38 



2. 48 



3. 76 



2. 90 



1. 49 

 5. 40 

 3.63 



3. 57 

 3. 85 

 1.88 

 1.80 

 3.07 

 4.14 



.94 

 2.68 



2. 23 

 1.75 



1.93 

 2.67 

 3.41 

 3.87 



.63 

 2.71 

 4.03 



.51 



.S3 

 3.03 

 2 42 

 4^67 

 4.69 



.63 

 6.76 

 6.20 

 2.75 



.87 

 2.19 

 2.97 

 2.28 



.61 

 2.97 



5. 85 

 3. 82 



6. 17 



2. 36 



3. 21 



0.24 



5.27 



2.41 



.57 



2.45 



.73 



.48 



6.09 



5.25 



2. 19 



.95 



.82 



3.55 



3.08 



1.96 



.91 



1.83 



2.19 



.05 



.85 



2.28 



4. 19 



1. 07 



4.69 



1.76 



2.05 



.64 



4.5S 



2.85 



.03 



.59 



2.26 



3.09 



1.63 



.41 



1.15 



1.58 



3.26 



1. 74 



2.58 



.44 



.30 



2.49 



1.79 



.40 



1.18 



.26 



.84 



.39 



.61 



4.46 



1. 55 



2. 90 

 .34 



2.47 

 .67 



0. 16 

 .28 





 .SI 

 .35 

 .08 

 .34 



3.24 

 .98 



2.00 



2.24 





 .20 



5.09 



2.58 

 .66 

 .51 



3.25 

 .2S 

 .94 

 .02 



1.98 

 T. 

 .18 

 .40 

 .59 



L. 16 



1.26 



1.08 

 .43 

 .82 

 .79 



2.68 

 .63 



2.06 



1. 11 

 .07 

 .04 

 .55 

 T. 

 .69 



1.45 

 .19 



1.46 







.54 

 T. 

 .95 



1.18 



2.84 



1.17 

 .13 

 .88 

 .04 



2.7S 

 .50 



15.60 

 17.23 

 15.81 

 24. 79 

 24.28 

 19. 16 



22. 54 

 27.39 

 24.40 

 24.42 



23. 11 

 20.28 

 21.33 

 32.32 



24. 92 

 18.09 

 19. 05 

 19.59 

 11. 15 

 22. 73 

 15. 08 



15. 97 

 19.27 

 27. 64 



16. 43 

 17.06 

 18. 11 

 22.01 





1893 



16.42 



1894 



16.21 



1895 



18.36 



1896 



19.54 



1897 



19.48 



1898 



19.91 



1899.. 



20.85 



1900 



21.24 



1901 



1902 



21.56 

 21.70 



1903 



21.58 



1904 



21. 56 



1905 



22.33 



1906 



22.50 



1907 



22.22 



1908. . . 



22.01 



1909. . 



21.90 



1910 



1911 



21. 34 

 21.41 



1912 



21. 10 



1913 



21.01 



1914 



20. 93 



1915. . . 



21. 21 



1916 



21. 02 



1917 



20. 89 



191S 



20.74 



1919 



20. SI 







Average. 



.47 



.83 



.59 



1.72 



3.01 



2.43 



2.96 



3.04 



2.25 



1.47 



1.05 



.89 



20.81 





