Sorts aND FERTILIZERS FOR VEGETABLES 1299 
Furthermore, on account of location and ability to produce early 
crops, soils of low natural fertility are often the ones best adapted 
to trucking purposes. Principles regarding the maintenance of 
fertility in connection with vegetable growing are not radically 
different from those applicable in general farming; but considera- 
tions of earliness, quality and price of crop, together with pecul- 
iarities of soil, make necessary the more extended and special use 
of fertilizers. The maintenance of organic matter is here as every- 
where of prime importance, and the use of any amount of high- 
priced easily soluble plant food will not make up for a lack of it. 
If chemical fertilizers alone are depended upon, the tendency is 
for it to require more and more of them each year to produce the 
same results, and a condition may soon be reached where their cost 
will equal or exceed the profit from their use. 
The principles of crop rotation are also, from a fertility point 
of view, just as important in connection with vegetable growing as 
in general farming. It is much more difficult to maintain satis- 
factory yields when any one crop is grown continuously on the 
same land than if it is grown in a systematic rotation with other 
crops. However, special demands may sometimes make it advisable 
to sacrifice something in yield for the sake of specializing in a 
certain crop. 
Manures and Green Manures 
In the vicinities of cities stable manure is very largely depended 
upon to keep up fertility. Where this can be had in liberal 
amounts no chemicals may be needed and no other provisions made 
for keeping up organic matter. Yet very often a phosphorus 
fertilizer will be profitable in addition to manure and will help 
produce a better quality of crop and earlier maturity. Where 
manure is used only in moderate quantities phosphorus should 
always be used with it at the rate of 300 to 1000 pounds per 
acre of acid phosphate. On muck soils some potash will be needed 
in addition, and with market-garden crops on any soil both nitrogen 
and potash may be needed as mentioned later on. The use of 
manure can be overdone on some crops, such as potatoes, and in 
other cases it may induce too much vegetable growth or late ma- 
turity. The remedy, then, is less manure and more phosphoric 
acid and potash; but with the scarcity of manure its too liberal 
