Stable manures are universally regarded as the most valuable fertilizing materials for the growing of all classes of vegetables upon all types of soils. This is a very broad statement, but it is not likely to be challenged, since the most successful vegetable growers in all parts of the world place their main dependence upon stable manures. In many instances applications of special fertilizers have a more marked effect for the season or possibly for several seasons, but their long-continued use without additions of vegetable matter to the soil is always disastrous. It is true that examples can be cited of gardening operations that have been conducted for many years without any increase in the supply of vegetable matter, but in all such cases the supply of humus is very large to begin with. Muck soils are often farmed for a long term of years without manure, but even upon these soils stable manures are highly beneficial.
Market gardeners are especially dependent upon the use of stable manure, because there is no interval between crops for the growing of green manures. Near all our large cities immense quantities of manure are used by growers following intensive methods. In trucking or farm gardening, however, growers are learning to rely mainly upon cover crops and green manures, so the demand from this class of producers is not quite so great, perhaps, as a few years ago. But there are many instances of manure being shipped hundreds of miles. One very extensive grower on the eastern shore of Maryland declares that he could not be successful in producing melons and cucumbers without stable manure shipped from Philadelphia and New York.
Many growers of vegetables would never buy manure were it not for the necessity of maintaining the supply of soil humus. That is, it would be cheaper for thousands of gardeners to purchase commercial fertilizers for the needed plant foods than to buy bulky manure, pay freight and then haul several miles perhaps, not to mention the cost of spreading and of composting. But a liberal supply of soil humus is absolutely essential to success in growing all classes of vegetables. It increases the water-retaining capacity of soils; secures improved soil aeration; aids important chemical changes; increases soil temperature; helps to create favorable conditions for the work of friendly bacteria ; improves the texture of soils; makes it possible to begin work earlier in the spring and reduces the labor of tillage. Stable manures are superior to green manures as humus-making materials because they decompose more rapidly and are, therefore,' of greater value to the crops under cultivation.
In many instances manure is the cheapest source of plant food. Gardeners living near the cities often procure it at nominal prices. Under such conditions it would be unwise to make large expenditures for commercial fertilizers unless for special foods, such as nitrate of soda. Stable manures do not become available so quickly as many forms of commercial fertilizers, although composting (86) is of great value in hastening decomposition. The following table (U. S. Department of Agriculture, Farmers' Bulletin 192, page 9) shows the relative composition and the value of the manure of various animals:
Value a ton
The commercial values as expressed in the last column of the above table vary greatly. It is probably seldom that horse manure from city livery stables is worth as much as $2 a ton for the actual supply of plant food.
The bulk of manures purchased in the cities is horse manure. It is much drier than most other manures, looser in texture and acts more quickly than cow manure. It is practically the only kind of manure used in the making of hotbeds. Its decomposition in compost piles is very rapid and it must be carefully managed to prevent the loss of ammonia.
Cow manure is highly valued by vegetable growers as a slow-acting manure. It is much slower in decomposition than horse manure and may be safely applied nearer the time of planting. Limited quantities can often be bought at reasonable prices in small towns.
Hog Manure is also slow in action and generates very little heat in decomposing. It is valued by vegetable growers, although very small quantities are used. Some market gardeners near eastern cities have hogs fed mainly with the refuse from kitchens, and kept generally in cellars or covered sheds that are frequently very foul. Such practice is not to be commended from a sanitary point of view.
Sheep Manure is a hot manure, and when sufficiently moist decomposes very rapidly. Because of the fine texture, it is regarded as especially valuable for frame, greenhouse and open-ground crops that require a fine manure and a large amount of nitrogen. Onions are especially benefited by this manure.
Hen Manure, of all the farm manures, is the most valuable for garden purposes. It contains a large percentage of potash and phosphoric acid and is especially rich in nitrogen. It has long been regarded the best fertilizer for onions as well as for all other garden crops requiring large amounts of nitrogen. The fine texture, when an absorbent has been used in sufficient quantity, makes it highly desirable for intensive systems of cropping.
At the Pennsylvania State College, manure was collected from May 1 till May 18 from the dropping boards under the roosts of 145 hens. During this period 75 pounds of 14 per cent available rock phosphate were scattered on the platforms daily to prevent the loss of nitrogen. The platforms were cleaned about twice a week. A barrel filled in 18 days contained 330 pounds of manure, including the rock phosphate. The manure was analyzed by the experiment station and found to contain 52.46 per cent of moisture, 1.85 per cent of nitrogen, 3.17 per cent of phosphoric acid and 0.31 per cent of potash. At the prices usually paid for fertilizers it was worth $9 a ton. The 145 hens would produce a ton in no days. These figures of course do not take into account the amount of manure dropped in the litter and in the yards, but they do show that it is well worth while taking care of the poultry manure. The added rock phosphate prevents the escape of ammonia and increases the value of the manure, since a liberal amount of phosphoric acid is required by all garden crops. The greatest objection to this plan of handling poultry manure is that it is too wet to spread very satisfactorily, but this trouble can be easily avoided by using sifted coal ashes, dry soil or other absorbents in addition to rock phosphate.