The necessity of lime has been indicated in previous paragraphs. Malnutrition disease may become serious when lime is not used or when soils become acid. In vegetable gardening it is important to keep soils slightly alkaline and this is best accomplished by the rational use of lime. Va. Truck Expt. Sta. Bul. 4, p. 80: "Experiments on Norfolk soils show that liming is very beneficial to all crops except peas, beans and tomatoes. On cabbage lime was added in the spring of 1909, just before planting, and the yield was greatly increased thereby. The succeeding year the experiment was extended to include other crops, and the yield of all crops except peas and beans was markedly increased."
Lime not only neutralizes soil acidity, thus providing favorable conditions for friendly micro-organisms, but it also improves the physical character of soils, promotes decomposition, makes plant food available and enters into the composition of plants. It is also the best known preventive for club root of cabbage and allied crops.
Spring applications of lime gave better results at Norfolk than fall treatment. Lime should never be applied with manure, because it releases the ammonia. When both manure and lime are to be applied to the same soil it is best to plow under the manure, then spread the lime and mix thoroughly with the soil by harrowing.
The acid soils at Norfolk require from 3,500 to 6,300 pounds of lime to the acre to become alkaline. A ton of lime on many soils would be sufficient for the best results.
When a grower learns that it is possible to increase profits materially by the use of fertilizers there is danger of his depending too much upon special plant foods and not enough upon other closely related questions, such as tillage, soil moisture and the supply of humus. It should be borne in mind that no amount of fertilizer will make up for poor tillage, insufficient soil moisture and a small percentage of vegetable matter. More than this, the fertilizers applied will not be of full value unless all other conditions are satisfactory. It is impossible to incorporate fertilizer thoroughly in a poorly prepared soil. If the moisture content is insufficient the fertilizer cannot decompose or enter into solution to become available to the growing plants. Again, soils lacking in organic matter cannot continue to produce large crops even with the lavish use of fertilizers. Harmony of all conditions must exist before it is possible to harvest maximum crops of high quality.
In vegetable gardening commercial fertilizers should be applied after plowing and before much harrowing has been done. The fertilizer will then be mixed thoroughly with the soil in making preparations for sowing or planting.
Various drills and distributors have been placed on the market for applying fertilizers. Figure 11 shows a single-row distributor, and Figure 12 a wheelbarrow style. Both of these are very useful in some lines of garden work. The McWhorton distributor (Figure 13) is one of the best types; it may be adjusted to apply from a few hundred pounds to two tons to the acre. A lime spreader is shown in Figure 14.
While the various drills and machines are convenient and usually save labor, fertilizers may be sown satisfactorily and at small expense by hand. Bags of 50, 75 or 100 pounds should be distributed at proper intervals over the field to secure the desired application to the acre.
The material may then be carried in a bucket or a bag, and sowed with the same movements of arm and hand as are used in broadcasting clover seed. A more even distribution is possible, however, with machines.
It usually pays to buy only high grade fertilizers for vegetable gardening. They should be bought, of course, on guarantee. Not only is it important to know the percentages of the various elements, but the grower should know the sources. This information is not always procurable, but it is exceedingly important. Intelligent plant feeding is not possible without knowing the source of the various materials which enter into the composition of the brands used.
Home mixing of fertilizers is increasing in popularity. The following advantages may be mentioned: (1) The grower knows exactly the kind and amount of each ingredient used; (2) he can adapt the mixture to the needs of the different classes of crops to be grown; (3) he can adapt the mixture to the needs of the particular soil to be cropped; (4) he usually saves several dollars a ton; (5) he becomes more intelligent every year in the application of the principles relating to plant nutrition.
Numerous experiments have proved that home-mixed fertilizers are fully as valuable as factory-mixed goods of equivalent composition.
The arithmetic of home mixing is very simple. Suppose fertilizer is wanted that will contain 4 per cent of nitrogen, 8 per cent of phosphoric acid and 10 per cent of potash. (Dr. Edward B. Voorhees calls a mixture of this composition the basic fertilizer.) The nitrogen should be derived from at least two sources, say nitrate of soda, and an animal product, as dried blood. To make a more simple example, we will suppose that the nitrogen is to be derived from nitrate of soda, the phosphoric acid from rock phosphate and the potash from muriate of potash. It simplifies matters to think of percentages as pounds. Four per cent of nitrogen means four pounds in each hundred pounds or 80 pounds for the ton. As nitrate of soda contains about 16 per cent nitrogen, it is readily-seen that 500 pounds of this salt will be required to furnish the required amount of nitrogen. We will suppose that the rock phosphate is 17 per cent available, and 160 pounds of phosphoric acid are needed. By dividing 160 by .17, we learn that 941 pounds of rock phosphate are required. Muriate of potash contains 50 per cent of actual potash. By calculating in the same manner it is ascertained that 400 pounds of this ingredient is required to supply the potash. These three materials aggregate 1,841 pounds. To make a ton it is necessary to add some foreign matter, as sand. The sand would be known as the filler, which is of no value, but it increases the cost of freight, drayage and application to the land.
The home mixing of fertilizers is a very simple operation. Two men provided with short-handled shovels can do the work rapidly upon any smooth floor. The bottom of the shovels should be flat and the corners square. The grower should also provide a sand screen with a ¬-inch mesh, not less than 3 feet wide, 5 feet long, and mounted on a frame that may be propped up at any angle to the floor.
It is not convenient to mix more than half a ton at a time. The various materials are weighed and spread in a flat pile, each ingredient constituting a separate layer. The sand screen is placed conveniently near the pile and at an angle of about 45 degrees to the floor. The men stand on either side and shovel the fertilizer up on the screen. The finer particles fall through and the lumps roll to the bottom of the screen, where they can be crushed with the shovels. After the pile has been screened in this manner the screen is set aside and the pile shoveled over twice. When shoveling the bottom of the shovel should be kept on the floor to secure thorough mixing.
After mixing, the material should be rebagged in convenient amounts. A common practice is to place 100 pounds in each bag. A uniform amount in the bags is necessary to make an even distribution over the field before spreading or drilling. Mixing and rebagging should not cost more than 50 cents a ton. To prevent the forming of hard lumps the mixing should not be done more than a month before applying, especially if chemicals are largely used.