REVERSING NATURE’S PROCESSES.

Otago Witness, Issue 3111, 29 October 1913, Page 14

REVERSING NATURE’S PROCESSES.

In considering how soils are exhausted of plant food one has to turn for enlightenment to the manner in which their fertility has been built up by Nature. Year after year vegetable matter of some kind has been added to the soil until it becomes rich in humus, dark in colour, and fitted to reward the industrious cultivator. The Field Instructor of the South Island is reclaiming sandy dunes so as to fit them to grow potatoes and other crops by growing gorse on them for a few years, and thus adding nitrogen and vegetable matter to the soil. All the soil in bush clearings is rich in vegetable matter. The leaves of centuries have fallen and been incorporated with the soil by various agencies, such as ants and worms. These humble workers bring up the fine particles from beneath and build up the forest floor, thus covering the leaves and producing the finest soils in the Dominion. One has only to collect worm casts from a green on some autumn morning to understand how effective their work could be in the course of a century. A suitable medium for the working of soil organisms is provided, and storage and steady ripening of plant food results in the virgin soil, which the farmer finds ready, with fair treatment, to yield him its wealth. ‘ His work immediately reverses Nature’s building up. Every ploughing and cultivating exposes some of the vegetable matter to the action of the air, rain, wind, and frost. Every form of cultivation is only a alow process of burning up the vegetable matter in the soil. Our experts tell us that there is a greater loss of vegetable maltor and nitrogen from exposure to the elements than there is from cropping. In any case when the vegetable matter and its products are exhausted in a soil it is said to be worn out. But long before that time arrives the careful farmer takes steps to replace some of the vegetable matter which has been removed from the soil bv his operations. The best means of doing this should therefore be of vital interest to him. Green manuring is not adopted so generally as it deserves to be, because it is considered that the crops ploughed in must take a number of years to decompose, or rather decompose very slowly—while the reverse is the case. When conditions as to warmth and moisture are favourable the greep crop decomposes without much delay, and the production of soluble plant food proceeds with considerable rapidity. This is especially the case with the valuable nitrogenous portion of the green crop. The conversion of these into nitrates takes place quickly. The system of green manuring is effective on both sandy and heavy clay sods, and in all soils deficient in humus. In the former, green manures nitrify more quickly 7 than ordinary 7 organic manures like bonedust, dried blood, etc., while in stiff clay soil it nitrifies more rapidly than even sulphate of ammonia or animal manures. The discovery of the function of nitrogen by the bacteria associated with leguminous plants at once singled them out as the best agents for green manuring. Of these red clover gives the most effective residue. Mustard, rape, saradella, lupins, beans, and several other plants have been used on different soils for this purpose. Most of these would require inoculation before being sown on peaty soils devoid of lime. Crimson clover has also been sown on the stubbles in February, and produces a large amount of fodder before July, when it may be ploughed under in time for a green crop. There are various other means of increasing the vegetable matter in the soil, such as working into a system of producing large quantities of 'farmyard manure, and applying it to the land, eating the crops on the ground with stock and feeding large quantities of hay and straw along with concentrated foods. Nature’s process cannot be reversed with impunity without either impoverishing the land or the farmer, or both.