Rational Agriculture.

Waikato Times, Volume XXIV, Issue 1961, 31 January 1885, Page 2 (Supplement)

Rational Agriculture.

Bt R. W. Ejieh^-i Miclvob, F. 1.0., F.C R. 40. Lecturer on Agrirulture, Technical College,

Sydney. Am, soils not naturally barren when in a virgin ■tats arc oapable of sustaining what may bo termed tHeir normal amount of vrgetation, and they will continue to do po bo long as evervihing removed from them is returned, either by the decay of the plants themselves * in the form of manure. If no such iestoration takes place, and the prodace be continually removed, then the land may in time become exhausted. When the matters referred to arc returned to the coil, not only « fertility preserved, but, by adding more of the aubstancch, than is requisite to make good what the crop* removed, its productive power may be vpry much increased ; and, indeed, it may ')e stated as a rule that all ordinary soils, by tho jedicion* use of manure?, are much improved in fertility. The main object of manuring is to return to the land adequate supplies cf tho Ribstances removed by the crops ii a condition in which they aro suitablo for absorption by the roots of yonng plant". On con.-: '-ring the practical bearing of thin principle it might bfi a-aumed to be needful that a manure should contain all the oonFtituents of plant food in the proportions in v?hich they have been removed from the soil in the crops. This is by no means the case. When a soil becomes exhausted through the reptated cropping of the same plant without manure being u»ed, tho exhans tion i« Dover duo to the simultaneous withdrawal of all its available plant food constituents, but usually to the more or lees complete removal of one or tvo of those only which, from thnr having existed in the land in comparativdy small quantities, are more quickly removed than the others. To bring back fertility to such a soil it is not necessary to return all the substances taken away in the crops, but it will suffice to restore only those which are absolutely wanted, or, in other wordf, which haTe become deficient. A plant will grow healthfully so long as it obtains a supply of all the substances required to build up its structure ; but iti development if as effectually checked by the want of one of thrse as by the want of all of them. Hence it follows that, in the case •npposed, it would be necessary to use the manures in quantity sufficient to furnish the soil with an Adequacy of the deficient iubstance or sub■tancPß.< If, on the other hand, a soil be treated with a manure containing only a •mall proportion of one of the necessary cen■tituents of plant food and large proportions of all the others, the increase in the fertility of the land will be regulated not by the substances nhich are abundant, but by the deficient component. Were this course pursued for some years in succession the other constituents of the manure would not have been ntilised to any extent by the crops, and mast, therefore, hare accumulated in the soil. Now in order to bring into. active use these dormant snb•tanoes the system of manuring, and if practicable, also of cropping must be changed. In order to restore the proportions of the different constituents of the soil required by plants, all that would be necessary would be to add a sufficient quantity of what is termed a special manure, that is to say a manure containing one or two of the substances which existed in the soil in too small quantity. A fertiliser containing all the constituents of plant food is said to be a ncneral manure, While one containing one or two of these only, is called tprcial manure. The latter in itself is incapable of permanently maintaining the fertility of land, to which it is eon•tantly applied, but acts mainly in bringing into u?e tho dormant material in the soil. A general manure, on the other side, used in jquantities, prevents the exhaustion of the poil, and by causing the accumulation of plant -food constituents, may render fertile an uliuoot barren sand. Of *he two Kinds of manure it U hard to gay which i« the moro important. One thing is certain, and that is that special manures would not be employed were it possible to obtain peneral manures of a composition exaotly adapted to meet the requirements of the crops to be grown. This is impossible in practical farming. The composition of the only general manure to be met with on the farm, viz., farmyard manure, is quite beyond our control, and it does not necessarily contain its constituents in the moßt snitablo forms or proportions, and, as a consequence, when used for a succession of years certain of its constituents must accumulate in the ground, and it is under such circumstances that special manures are particularly uspful. The " muck-heap" has been described ai "tho manure par crcelUjpt ■which prnctice has realised; a collection of all residue of the harvest, a true caput moituum of agricultural operations," and in thepe colonitß is justly regarded at its proper Talue. Its employment as a top dressing for pasture land previous to the latter being broken up for cultivation has proved satisfactory in most places, but its direct use on wheat lands has, in many instances proved not only unprofitable, but disastrous. Upon green crop manuring or feeding off with aheep, and the systematic use of artificial or special manures, the colonial farmer of the future will depend for large orops and the maintenance of the productive capabilities of his land.