BASIC SLAG.

Otaki Mail, Volume XXVIII, 26 January 1920, Page 4

BASIC SLAG.

As a top-dressing for pasture, in order to be beneficial, slag requires a climate with a well-distributed rainfall, slag being only slowly dissolved by water containing carbonic acid, whereas superphosphate is entirely and quickly dissolved by pure water. A moist climate is therefore a prominent factor in the successful use of slag; if deficient in phosphates, soils in dry climates with few rainy days are better treated with superphosphate. On soils very rich in humus and deficient in mineral matter, such as those resulting from tbe drainage of some swamps, basic slag will no doubt prove superior to superphosphate or mixtures of the two. "when drilled in with the seed. This type of soil is usually deficient in potash, which must be supplied with the slag, especially when attempting to grOw potash-loving crops like the mangel or potato. The greatest immediate effect of slag is manifested on the leguminous (clovers, etc.) components of the pasture, the white clover (Trifolium .especially is therefore necessary that these plants should be present in the pasture. Experiments with slag in Scotland, Professor Patrick Wright ("Improvement of Poor Pasture," page 10) tells us, failed owing to the absence of clovers in the pasture. When, however, clover seed was supplied the effect of slag on these soils was quite as remarkable as ou those of Cockle Park.

The process of the manufacture of basic .slag has been so often described in detail that it is unnecessary to repeat the story. It will suffice to explain briefly that it is a by-product in the manufacture of steel by the basic process introduced nearly o 0 years ago. It has been known as phosphate powder, Thomas» phosphate, basic slag, and slag phosphate. The name by which it is now generally known to farmers is basic slag, the other names having largely dropped out of use.