It is not uncommon to find market gardens managed successfully without the use of commercial fertilizers. In all such cases stable manures and perhaps night soil are applied in liberal quantities. Although it is possible to make large profits when fertilizing with manures only, it is doubtful whether there are any instances when commercial fertilizer in some form could not be used to advantage. Manure is an unbalanced ration; it is richer in nitrogen than in mineral elements and there is likely to be a surplus and, therefore, a waste of nitrogen when it is applied without corresponding additions of potash and phosphoric acid.
The most forceful argument for the use of commercial fertilizers is the inadequate supply of animal manures. While hundreds of market gardeners near the cities depend mainly upon stable manures, thousands of truckers remote from the great sources of supply must resort to the use of commercial fertilizers in order to secure maximum returns.
There are other reasons for the use of commercial fertilizers. Stable manure must undergo changes before it is accessible to plants, while some of the commercial fertilizers are immediately available when incorporated with moist soil, a characteristic which gives chemical fertilizers a great advantage over stable manure, for it is possible to mature crops in less time by their use than can be done with manure alone. Rapid growth is of immense importance in commercial vegetable gardening. Therefore, with the aid of commercial fertilizers the gardener may be able to harvest several crops from the same ground in one season, to clear the land in time to start a cover crop or mature a green manurial crop before cold weather, and to secure far better quality than is possible when the growth is slow. The quality of many vegetables is closely associated with rapidity of growth. A slow growth is likely to cause a bitter flavor in lettuce, a sharp flavor in onion and a pungent flavor in radish". Again, slow growth is certain to cause greater development of fiber, making the vegetables tough, woody or stringy. A rapid growth usually secures succulence, crispness and palatability. And, in addition, rapid-growing vegetables are less subject to injury from insects and diseases than are slow-growing ones.