WEEDS ON THE FARM.

Waikato Times, Volume 112, Issue 18809, 3 December 1932, Page 10

WEEDS ON THE FARM.

METHODS OF CONTROL. PERSISTENCE OF LIFE IN SEEDS. IMPORTANCE OF STRAIN. (By H. Woodyear-Smlth, Technical Fields’ Adviser). Many farmers throughout the Waikato are concerned with the amount of weed growth present In the pastures and also the astonishing recovery of weeds on land after ploughing. Suitable methods for the control of these weeds, both in the pastures and in arable land constitute a very present problem and although it is not possible ’n an article of this nature to go fully into the question, the following should be of interest and assistance both Jn understanding the position of weeds and the possible measures for control. Many types of weeds, especially those found in pastures, are really indicators of a condition, low fertility, a weak poor invigorous sward of grasses and clovers resulting from the use of bad seed, the effect of trying to establish some grasses outside their natural habitats, etc., and in this way, these weeds, in a sense, serve a useful purpose in acting as symptoms describing various conditions. Farmers are often Astonished at the comparative freedom from weeds in a pasture to lie ploughed and the •enormous weed growth which takes place after ploughing. Undoubtedly many of the weed seeds •can lie dormant in our soils for a considerable length of time. Mention has? been made at times of seeds which have been recovered from ancient tombs in Egypt and which have germinated when sown. “Mummy” wheat is often quoted, but there is no foundation in fact for such statements, as such seeds have never been grown. Nevertheless life will persist in some •seeds for a great length of time as is shown hy the following comment hy Professor Sir J. Arthur Thompson, who says:— “We have several times referred to the question of the length of time that vitality may linger in inactive seeds. The question refuses to be put to •sleep because it Is a relative one, and because good instances of long latency are of frequent recurrence. While It is probably true that genuine ‘mummy wheat’ never sprouts, though what is called ‘mummy .wheat’ often does, there is no doubt that seeds may occasionally be latent for a century. “A good case Is vouched for by Sir Arthur Hill, the Director of Kew. It concerns some lotus seed (Nebumbium) from the Manchurian peat, which germinated at the Gardens after lying latent for 120 years. Robert Brown germinated a seed of the same plant which had been in the British Museum for 150 years, and other cases have been carefully recorded. After the fruit of the lotus or water lily rots and bursts. It Is the habit of the seeds to lie latent for a time In the mud at the foot of the pool, and it may be that this is life-saving in situations where drying up of the pools Is of common recurrence.” Retaining Vitality. Professor E. J. Salisbury, writing to the Times from Herts, calls attention to the re-assertion of the Blue Pimpernel after many years of latency, and many a farmer has noticed similar cases. “The site was a twoacre meadow which, though under hay for at least 60 years, bore unmistakable signs of having been once under the plough. There is indeed little doubt that It is one of the many arable fields which were laid down to grass at the end of the Napoleonic wars. In several places where the turf was stripped off, various cornfield weeds appeared, and notably plants of the Blue Pimpernel, a plant now exceedingly rare in Hertfordshire.” The plant did not appear except where the turf was stripped, and the strain was exceptionally dark flowered, as compared with that still found as a casual in the county. Thus it is likely that the seeds had remained dormant for more than a century, since the area in question was cornlald. Seeds that have this power of retaining vitality without sprouting, may secure the survival of the species in untoward condition? such as drought. In a recent letter to the Times, Messrs Sutton, the well-known seedsmen, recall the fact that there are only some plants which have this quality of lying low. It depends on a combination of qualities, and thus, In the struggle for existence, only certain kind? of plants would survive when dormancy was Indespensable. Thus smallness of seeds Is sometimes of great advantage in reducing the area of vulnerable surface; hardness of seed envelope may be useful in withstanding bacteria, or there may be protection oils In the seed substance that are of great value in retaining vitality. Messrs Suttnn report fifty years survival for black mustard and curled dock, twenty-three years for charlock, poppy and fumitory. Tt will he understood that, the actual turning up of the soil is not necessary to bring about the actual revivification of dormant weed seed. Seeds drop,pod or carried into dense vegetation, may fall Into crevices and lie shut off from light and rain hy Hie close growing plants well adapted for such a situation, but when this shade is removed and radiation and moisture are made available there comes a sprouting of dormant seeds which reassert themselves on the cleared space. In order to control weed growth in permanent pastures, it is vitally necessary to use grain seed of approved strain and type. Tills not only ensures lone: life of tlio pasture, but Ihe individual pasture plants forming the sward, hy virtue of their true perennial eharaclerislics, together with llieir dense close habits of growth, will form a dense close liiiT which by keeping mil light and air from the soil underlie, l lh will not permit the undesirable weed lo establish. Thus il is that proper management and treatment of the pastures nr" so essential in Ihe maintenance of a good clear pasture, coupled with snriessential practice as the building up of Ihe fertility lo enable I lie good perennial grasses to wage unceasing warfare against the inclusion of weed growth. Over-grazing and over poaching at any period of Ihe year are dangerous praeliees. while under-grazing, besides being imernmonie. is eoually unsound. >urh perennial weeds as ragworl ( S"n""ln .Tarohoeai will establish in really good pastures. Ini! i! is significant (o remark that this weed is never found In be widespread where first-class pastures are maintained under ideal ■•onditious of management and fertility.

Methods to Adopt. Suitable methods for the control of general pasture weeds are therefore: The sowing down of true vigorous, perennial, pasture seeds. The building up arid maintenance of the soil fertility to support the high producing, vigorous perennials. The proper cultivation of the sward to bring about root pruning, soil aeration and the removal of useless dead matter. The treatment in grazing, neither over-grazing nor under-grazing at any period of the year. . The topping of pastures under grazing, if the stock cannot control the growth and the plants run away to seed, thereby losing a great deal of their vigour which should be directed to producing leaf. Tor the control of weeds in pastures such as ragwort, such measures as spraying with a 3J per cent solution of sodium chlorate, or broadcasting a mixture of lime and sodium chlorate, containing 281 b of sodium chlorate to every 5 cwt of lime, have been adopted. In the turning up of land with the plough for cropping, fallowing in the summer months, and repeated cultivations are the most efficient methods to adopt for weed control. The young seedlings should he cultivated out of the soil. Being deprived of their food and moisture supply from the soil and exposed to tlie withering effect of sun and wind, the young plants quickly die. Short cut methods in freeing ploughed land from weeds arc seldom if ever successful, and although it appears wasteful to allow ground to he idle for a long period, yet it is Ihe only practical method of providing a clear, seed bed for the succeeding crop. Smother crops will undoubtedly check weed growth and in fact cause a percentage of death amongst flic weeds, but IliCy do not clear the ground so thoroughly as fallowing and repeated cultivation.