44 AGRICULTURE. 



material of the soil, it merely works over what is in the soil 

 for feeding the plant ; it can not and does not prevent the soil 

 from becoming worked out. Furthermore, there is the loss of 

 one season's crop, and if the soil can be kept in good condition 

 and a crop grown at the same time, all will admit that the latter 

 should be done. In bare fallowing, however, the soil is more 

 or less cleared from weeds when the fallowing is thoroughly 

 done. But weeds can be cleared out by other means than 

 the bare fallow. First of all a cultivated crop can be grown, 

 such as corn or roots the constant cultivating required during 

 early growth will clear out the weeds. Or a crop can be put 

 in that grows quickly and that covers the ground well, such as 

 clover, buckwheat, etc. This smothers or checks the young 

 weeds, and the green growth can be plowed under to decay 

 and form humus. This practice is called green-manuring. 

 In green-manuring there is less water lost by drainage than in 

 bare fallowing and hence less loss of soluble plant food. In 

 addition everything that the plant takes from the air is turned 

 into the soil and the amount of humus is thereby increased. 

 This latter result is very beneficial in loosening up heavy soils 

 and in making light sandy soils more loamy. 



FERTILIZING THE SOIL. The plant gets some food out of 

 the air through its green leaves ; the water comes from the 

 rains that fall on the soil and pass in through the roots ; the 

 mineral matter or ash comes only from the soil, passing into 

 the plant through the roots along with the water. The air is 

 free for all and is about the same everywhere. The rains and 

 snows are largely beyond the control of man, except as 

 affected by the cutting away or growing of trees, the drainage 

 of the land, and its proper cultivation. But as for the soil food, 

 the mineral substances, the ash compounds these must be in 

 the soil, and in such form that plants can take them up, or else 

 no crop will be produced. This soil food is mainly compounds 

 of nitrogen (nitrates, such as saltpetre or nitrate of potash); 



