THE VALUE OF HUMUS.

New Zealand Mail, Issue 1367, 12 May 1898, Page 4

THE VALUE OF HUMUS.

ITL FUNCTIONS, AND HOW IT IS MADE.

A reeent bulletin of the Minesota Experiment Station discusses humus, and draws the following conclusions : The animal and vegetable substance in the soil in varying degrees of decay or decomposition are collectively spoken of as humus, or organic matter. These substances, when they reach the proper stage of decay unite chemically with the potash, phosphoric acid, and lime of the soil, forming compounds called humates.

Humus has been found to be valuable in the following ways : 1. It absorbs or '• fixes" nitrogen, thus preventing the loss of this, the most valuable of all fertilising elements. 2. It absorbs water, thus enabling the soil to better -withstand droughts. 3. It render* r>c- w .a»h and phosphoric acid soluble, so that they can be taken into the sap of plants through the roots.

For thesft reasons farm manures possess an advantage and value over and a'"Ove the market price of the nitrogen, potash, and phosphoric acid they contain. Their bulk is mostly humus, a valuable material which exists in very small quantities in commercial fertilisers.

For the same reason, clover, peas, ; and other green crops—even weeds—turned out, are largely beneficial to land, aside from the nitrogen they have from the air and the phosphoric acid and potash their long roots may have brought up from, the subsoil. THINGS THAT PRODUCE HTJMUS. Investigations prove the following interesting and valuable facts relating to humus : Farmi manure, green clover, blood, fish, tank-age, cotton seed, &c, produoe humus rich in nitrogen ; while oats, straw, sawdust, and carbonhydrates form humus poor in nitrogen, but rich in carbon, and the nitrogenous humus more readily uniteß with the ♦potash and pjjosgmorjo acW of the soil

to form humates than does carbon* aceous humus. Tne humus of virgin soils is much richer in nitrogen and huraates than the humus of soils that have been cropped for a series of yea i s.

The practice of burning off lands preparatory to ploughing often permanently injures their crop-producing

powers. Clean culture to hoed crops tends to exhaust .soils of their humus, and this is why the old cotton fields of South America became so poor. It has been found that the growth of clover, cow peas, &c, soon restores these lands to a high degree of fertility, if the all needed potash and phosphoric acid be applied to the clover and pea crops.

Soils most in need of humus are sandy, and sandy loam soils that have long received clean culture without the application of farm manure. Mucky, peaty clay and prairie soils do not need humus for many years after they are put in cultivation. An ordinary prairie soil needs no humus added foi about ten years after it is first put in cultivation.