Superphosphate

Is there any way to add phosphorus to soil without using commercial fertilizer? Yes, in the form of pulverized phosphate rock, bone meal, or basic slag. All may take a year or more to become available.

Are the effects of superphosphate somewhat similar to those of bone meal? Yes, the effects are similar. Bone meal contains a low percentage of nitrogen not found in superphosphate. The phosphorus in bone meal, however, is only available over a long period of time. It can "lock up" in completely insoluble form.

How should one use agricultural lime and superphosphate? They should not be mixed. If so, the phosphates are made unavailable.

Is there any advantage in applying superphosphate to perennial border or rock gardens? Many soils are deficient in phosphorus. If perennials or rock plants are planted in such a soil, they will be benefited by applications of superphosphate.

How should superphosphate be used? I have some and do not know how to apply it to flowers. Phosphate is best applied when the flower beds are first prepared, by working it into the upper 4 to 6 ins. of soil. If plants are already in the bed, apply the phosphate between the plants and work it into the soil as deep as possible (down 6 to 8 ins.) without disturbing or injuring the roots. Apply 30 to 40 lbs. per 1,000 sq. ft.

When and how often should superphosphate be applied to perennials and rock plants? In addition to the use of superphosphate at the time the beds are prepared, yearly applications of phosphorus are advisable, especially in soils tending to be deficient in this element, by an application of a complete fertilizer in the spring.