EVAPOTRANSPIRATION ETC., WITH IRRIGATED GRAIN SORGHUM 



these soils should be similar, because of rapid 

 lateral water movement in the plow layer and the 

 dense soil below the plow layer that extends to a 

 depth of about 3 feet. 



The soil on the experiment site was first ir- 

 rigated in 1956. Before 1956, the land was 

 fallowed in 1955 with a previous cropping history 

 of a wheat-sorghum-fallow dryland rotation. 



Climate 



The weather in the Great Plains is noted for its 

 great variability and rapid changes. Extreme 

 variations in monthly rainfall, daily temperature, 

 and windspeed are normal expectations, especially 

 during the months of March, April, and May. 

 Annual precipitation ranges from less than 10 

 inches to over 30 inches. 



A summary of average climatic conditions and 

 the weather conditions existing during this 4-year 

 study is presented in table 3. The probabilities 

 of receiving various amounts of rainfall are illus- 

 trated in figure 1 (5) . The pattern of precipitation 

 is similar for much of the area, but more precipi- 

 tation occurs east of Amarillo. 



100 



10 20 30 40 50 



PRECIPITATION (INCHES) 



Figure 1. — Probability of receiving various amounts of 

 annual, fallow period, and sorghum growing season 

 precipitation at Amarillo, Tex. The curves represent 

 the percentage of time that precipitation can be expected 

 to be less than the amounts shown. 



Table 3. — Summary of weather data for the grain sorghum growing season at Bushland, Tex., 1956-61, 



and averages for longer periods 





Preceding 

 fallow period, 



November- 

 May, average 

 or total 



Crop growing season 



Annual 



Year 



June 



July 



August 



September 



October 



Average 

 or total 



average 

 or total ' 





Precipitation (inches) 



1956 



6.65 

 8.62 

 9.61 

 6.39 

 7. 20 



1. 10 

 3.05 



1. 77 



2. 69 

 2. 60 



3. 18 



1. 70 

 7. 79 



2. 15 



2.88 



2. 03 

 4. 22 

 . 53 

 2. 50 

 2. 51 



0. 12 



1. 05 

 2.05 

 1. 13 

 1. 64 



0.32 

 2. 55 

 . 21 

 2.00 

 1.87 



6. 75 

 12.57 

 12. 35 

 10.47 

 11.50 



13. 40 



1957 



21. 19 



1958 



21. 96 



1959 



16 86 



1939-61 



18. 70 





Mean Daily Maximum Air Temperature (°F.) 



1956 ... 



66.2 

 63.6 

 59. 7 

 64. 4 

 62.9 



92. 6 



88. 6 

 93.5 



89. 3 

 89.4 



92. 9 

 96.5 

 91. 

 89. 6 

 91. 3 



91. 7 



89. 9 



92. 6 

 92. 1 



90. 5 



90. 2 



83. 3 

 85. 1 

 86.9 

 84 9 



80. 2 

 69. 9 

 73. 3 

 72. 2 

 74.6 



89.5 



85. 6 

 87. 1 



86. 

 86. 1 



75 9 



1957 



72 8 



1958- 



71 2 



1959. 



73 4 



1939-61 



72 6 









Mean Daily Minimum Air Temperature (°F.) 



1956 



31.0 

 33.3 

 32. 9 

 30.3 

 32. 1 



63. 1 

 57. 4 

 60.4 

 60. 2 

 59. 5 



63. 2 

 64 9 

 64.3 

 61. 6 

 63.3 



60.8 

 62. 8 



62. 



63. 5 

 62.3 



55. 5 

 51. 3 

 57.4 

 53. 8 

 54 7 



46.3 

 44 6 



43. 7 

 39. 5 



44. 1 



57. 7 

 56.2 

 57.5 

 55. 7 

 56.8 



42 2 



1957 



42 9 



1958 _. 



43 2 



1959_ . 



40 9 



1939-61. 



42 4 







See footnotes at end of table. 



