126 AGRICULTURE ON THE PACIFIC SLOPE 



beets or turnips. These have tap roots and feed largely 

 on potash, while grains take up large amounts of phos- 

 phoric acid and nitrogen. Or grains may be followed 

 bya legume crop, such as peas, beans, clover, or vetches, 

 which also root deeply, and add nitrogen to the soil. 



Rotation of crops will keep up and sometimes renew 

 the crop production of lands in a surprising manner. 

 It is growing wheat after wheat for years which has 

 worn down so many rich lands in the United States, 

 until wheat growing became unprofitable. The wheat 

 must be replaced by clover, alfalfa, and root crops. 



In practicing rotation it is usual to have a " money crop/ 7 

 readily sold for cash, such as wheat or cotton; then a manu- 

 rial crop of some legume (clover, alfalfa, vetches) .which at 

 the same time may be a forage (cattle-feed) crop, or may be 

 followed by one ; then a " hoed crop " grown in drills or hills, 

 like corn or beets, which clears the ground of weeds. Then 

 we begin with the money crop again. 



Fallow. There is sometimes one year of fallow, that is, a 

 year when no crop is grown, the land being plowed and 

 either left rough or harrowed. This "bare fallow" often 

 results in a very much larger crop the next year, because of 

 plant food being made soluble in the soil. But that plant 

 food is very liable to be washed out of the land by rains. 

 This plajjJsjEejry wasteful of humus, and thereforeofnitrogen, 

 the most expensive^oTT!i^eSiirzTng elements. We should 

 therefore sow a " catch crop" of some rapidly growing plant, 

 such as barley, oats, buckwheat, and others, which can be 

 sown in summer and plowed under in autumn or early winter. 

 We thus add greenmanuring to the benefit of the fallow with- 



