Run-off in per cent of total precipitation 



Land use 



Soil loss in tons per acre per year 



16.2 



14.5 



Hative grass 

 (protected) 



Native grass 

 (clippsd) 



Kafix 



Wheat 



Wheal 

 (on erodedi soil) 



s " io is qM 



Ceibysi%dasfto8W.5?8.siop.,,,,...g 



30 



20 10 



annual precipitation 20.36 ttidies 



g-ye8i]»riQd 1^4935 



Runoff in per cent of total precipitation 



Land use 



Soil loss in tons i3er acre per year 



28.64 



Cotton il% slope) 



Cotfcoa 



FaUow (tiUed) 



Fallow (cot tilled) 



Btam ^ 1-75 



Milo 



10.89 



14.07 



'30 20 10 



Average annual precipitation 20.91 inches 



S-yeaf i»riod 1^6-1933 



5 10 15 20 



Abilene day toam,2% slope (except plot 1) 



USING THE LAND AND LOSING THE SOIL AND WATER 



The rains ancJ snows run off the land more or less rapidly and thoroughly, according 

 to the way the soil is used and treated. Modern methods of extracting from the 

 earth its precious yield, as quickly as possible, and more than the inhabitants can use, 

 sometimes destroy the very earth upon which we depend 



ing the old growth away with a stick before scattering the seeds would yield 

 more. Man learned to scratch deeper. He hitched an ox or a camel to a 

 heavier stick. Later he used horses. He put a steel edge on his plow. Finally, 

 all merely mechanical work of man and beast is transferred to machinery. 



By using more and more machinery in cultivating, weeding, watering, 

 harvesting, and so on, a small crew of skilled operators is able to work twenty 

 or thirty times as much land as they could with horses and their own labor 

 (see illustration, p. 646). Through such intensification of effort, combined 

 with other improvements in practice largely based on biological knowledge, 

 men were able to increase the output per worker and also the yield per acre 

 up to several hundred per cent. But in this progress they failed to note 

 that there is a point beyond which bigger and bigger does not necessarily 

 mean better and better. For by using more powerful machinery for work- 

 ing the soil, they came to plow deeper and deeper and so defeated their own 

 purposes. Turning the soil over too completely covered the stubble and 



644 



