ABOUT WEEDS.

Dominion, Volume 5, Issue 1366, 17 February 1912, Page 8

ABOUT WEEDS.

OPINIONS OF AN EXPERT.' Agriculture is probably the most natural of all sciences, writes Mr. T. W. Lonsdale in the Agricultural Department's Journal, yet in its practice much is embraced which is essentially artificial. Evidence in support of this assertion nu\y be adduced by a cursory view of the system adhered to in tho cultivation of arable land. In this work, instead of supporting Nature and allowing her to work out changes in her own time, it is necessary, in the successful raising of crops, to work almost in direct opposition. No farmer, when allowing a piece of land to lie fallow for a season, would expect at the end of that timo to be able to reap a crop of oats, but there would inevitably bo an abundant crop of weeds derogatory to his interests. The soil is tiie foundation of agricul-ture,-therefore the first and best attention of every agriculturist is to clear the land of welSds, otherwise he cannot reasonably e.\];oct to raise profitable crops. The question is often asked: What is a weed? and the many attempts made to answer it, though in a tense successful, are lacking in precision. A weed may be termed a plant out of place, or a plant growing naturally among a crop which has been sown, but differing from this crop and hindering its growth. Briefly, all undesirable plants, whereverthey may be found growing, may safely bo "classed 1 as 'weeds.

. It is not only found that most weeds have restriction of growth and development on special classos of soils and -with special degrees of fertility of land, but it is noted that in many cases, where land is converted from a state of nature to arable cultivation,'plants which had previously nourished entirely disappear, 1 and are superseded by others of different habits which apparently are better able to adapt themselves to the prevailing circumstances. - How is it that the latter now make their appearance, or why do those which previously predominated now disappear? To enable these questions to be answered it is necessary to closely observe the habits of the various species and make a division. according to duration, e.g. (1) annuals, (2) biennials, (3) perennials. Annuals are those which complete their life-history in one year. From the seed which germinates in tho spring a fresh supply for the carrying-oa of the species is produced before tho end of the first season. Such are chickwood, spurrey, and groundsel. • Biennials during tho first season throw out luxuriant foliage and develop a strong tap-root, the second season being entirely devoted to the process of reproduction. The resources accumulated during the first season a,re drawn upon for this purpose. Examples arc species of docks and ragwort. Perennials are weeds which live more than two years. The foliage of tliese dies awav eaeli autumn and appears the following spring, being propagated-by buds which are ioutul on the underground stems. Canadian thistle and corn-bind-weed are examples.It is now necessary to consider the altered conditions of the soil brought about by cultivation. Assuming the land was previously-virgin pasture, there was then a compact surface layer, giving tho plant a thorough attachment to tho soil, and also preventing excessive escape of moisture, whilst on ploughed land tho reverse holds true.

The cosditions of tbo ploughed land favour annual weeds, whilst the perennials would be moro adaptable to the virgin pasture; and probably a few biennials would be found in both places. We may therefore safely assume that the altered soil conditions are responsible to some extent for the distribution of weeds. No one will deny that the injury oaused by weeds is enormous; and if an estimate oi' tho annual loss to the country incurred by the growth of weeds could be given tl'l9 result would be astounding. On arable land the amount, of water taken up by weeds and evaporated from tho surface"of the leaves is very great. This is considered by many to bo the most serious injury done by weeds. Not only do they absorb a largo amount of moisture, but they also rob the crop to a great extent of the available plant-food; an<l it is often noticeable that weeds grow more vigorously than useful plants, in some instances completely, destroying tho defined crop. 1 Eradication differs according to the species to be dealt with, but in tho treatment of all weeds a 6titch in timo saves nine. Prevention of seeding wherever possible, the destruction of any weeds that are already existent in the soil, and the prevention of the introduction of more weeds by seed or otherwise, oro cardinal points to be strictly observed. By strict adherence to these the writer is confident that a few years hence the progress made in the extermination of weeds will astonish the most pessimistic person of today.