84' BULLETIN 479, U. S. DEPARTMENT OF AGRICULTURE 
contain only one of the desirable elements. However, if this is neces- 
sary, it should be remembered that the growing of cover crops is the 
most inexpensive way of introducing nitrogen ; that phosphoric acid 
can be introduced by the use of Thomas meal and bone meal, both 
of which also add lime to the ( soil ; and that potash is most cheaply 
introduced by the use of kainites. 
Commercial fertilizers (with the exception of those containing 
lime) do not improve the texture of the soil to any extent, and lime 
does not improve loose soils ; commercial fertilizer is rather rapid in 
its action, making it preferable where quick effects are wanted, but 
is likely to be quickly lost through leaching out ; it is expensive and 
sometimes difficult to obtain; and some of it contains only one or 
two of the elements essential to plant growth. Manure is also often 
difficult and expensive to obtain in sufficient quantities; if mixed 
with much litter not well decomposed it is likely to cause drying out 
of the beds; and it does not give such immediate results. On the 
other hand, it does not leach out rapidly, it improves the texture of 
both heavy and light soils, and it furnishes sever aj. of the elements 
which are essential to plant growth. 
In choosing fertilizers the absorption capacity of the soil must 
also be considered. This is much greater in fine and clayey than in 
sandy soil; in the latter there is always danger of any soluble sub- 
stance, such as saltpeter, being washed out. In such cases the nitro- 
gen is best furnished by green fertilizing and stall manure, and 
lime by carbonate of lime instead of unslaked lime. 
TIME AND METHOD OF INTRODUCING FERTILIZERS. 
Inferior soil, even before the first crop is grown, should be fer- 
tilized. Fertilizer should be applied at a time when it will prove 
most beneficial to the plants. Stable manure which has not been 
well rotted should be applied the fall or winter previous to the 
spring planting. Such manure can be used just before sowing or 
planting if it is turned far enough under the soil so that it will not 
come in contact with the roots. Compost, bone meal, and slaked 
lime or carbonate of lime may be applied just previous to the sowing 
or planting of the beds. Thomas meal, kainite, and carnallite should 
be applied the previous autumn, or the last two in the spring just 
before sowing or transplanting, if used only in small quantities. 
Chili saltpeter should be scattered on the ground and worked in 
between the rows after the seed has sprouted, because it dissolves 
easily and is carried quickly into the soil by rain. The other 
fertilizers mentioned should be well mixed with the soil which makes 
up the root zone. It is better not to fertilize too deeply in order 
to encourage lateral development of the roots rather than develop- 
