The most common source of phosphorus, usually referred to as phosphoric acid, is acid phosphate. Some is obtained from bone, and bone meal is a good fertilizer to use among pecan trees. The results obtained from its use are not immediate, but since the bone does not decay rapidly, they extend over a considerable period. On the whole, acid phosphate is as satisfactory as any material as a source of phosphoric acid, and the goods with the highest percentage are usually the most economical in the end. A good grade is that analyzing fourteen per cent.
Potash may be purchased, as kainit, the raw salt, or as muriate of potash, low grade sulphate of potash and high grade sulphate of potash. Of these the sulphates are usually given the preference in fruit growing. Of the domestic sources of potash, woodashes are important.
The amount of fertilizer which it is best to apply is difficult to decide upon; much depends on the character of the soil, what crops are cultivated and whether a crop of legumes is grown or not.
If legumes are grown for the benefit of the orchard, they should be fertilized, and if the crop is turned back into the soil, this may be sufficient for the trees, particularly while they are young. For the legumes, a good fertilizer to use per acre is:
Kainit, 100 lbs.; Acid Phosphate, 200 lbs.
or, High-Grade Sulphate of Potash, 50 lbs.
Acid Phosphate, 200 lbs.
In any case some allowance should be made for the amount of nitrogen collected by the legumes. When corn, cotton or some other crops are grown in the orchard, fertilizing may simply consist in distributing an additional amount of the crop fertilizer for the benefit of the trees.
For the growth of the young trees, a larger amount of nitrogen and a relatively smaller amount of phosphoric acid and potash are required, while for older trees, the reverse is true. Phosphoric acid and potash are required by bearing trees for the formation of fruit. Consequently, when the pecan orchard comes into bearing, these materials should be increased in the fertilizer applied. If the soil is not very rich at the time of planting, good results will follow the use of a pound of good commercial fertilizer at the time of planting.
A good fertilizer for young trees should analyze five per cent. phosphoric acid, six per cent. potash and four per cent. nitrogen. For bearing trees, one analyzing eight per cent. phosphoric acid, ten per cent. potash and four per cent. nitrogen will give good results. If so desired, well-known brands of commercial fertilizers, having approximately the above analysis, can be purchased in the markets, but if preferred, the several materials may be purchased separately, then mixed and applied.
Applying the Fertilizer.
The roots of young trees do not extend to any great distance away from the trunk. In distributing the fertilizer this fact should be remembered. A safe rule for all small-sized trees is to commence just outside an imaginary circle of two feet radius and apply the fertilizer in a circular band extending out some distance beyond the spread of the branches. Old trees, or those having a considerable spread of top, when planted in orchard form, should be fertilized by broadcasting the fertilizer over the ground. In the northerly pecan sections, all the fertilizer should be given in one application, about the time growth starts in spring, and plowed in, while farther south, two applications may be made, one at the time mentioned above, the other from the first to the middle of June.