CULTIVATING LUCERNE

Wairarapa Times-Age, 2 June 1938, Page 9

CULTIVATING LUCERNE

POINTS ON MANAGEMENT VALUE OF MANURE. CAREFUL TREATMENT NEEDED. On the basis of experience in many districts it has become the practice of successful growers of lucerne to apply two to four cwt of phosphate at or about the time of sowing the seed. Superphosphate, unless carefully used in the manner already described, may have a detrimental effect on the germination of the seed and on the inoculating organisms. Hence, for safety, some favour’ the use at this stage of basic slag or a mixture of equal parts of superphosphate and lime.

In most districts it is very advisable to dress lucerne at least annually with two or three cwt of superphosphate, which is at times successfully replaced by basic slag in the wetter climates.

The practice that should be adopted during the first year will vary greatly with circumstances. If annual weeds such as fat-hen and thistles have developed rapidly, and threaten by their competition to weaken or even destroy the young seedlings then it will probably be necessary to mow the crop earlier than otherwise in order to give the invading weeds a set-back, but if weeds are not threatening to give trouble it is harmful to mow the young plants until they are blooming or fresh young shoots have appeared at the bases of the plants. The delaying of the first mowing until this stage favours the growth of an extensive root-system, whereas a relatively early first mowing diverts the energy of the plant -to a renewal of the aerial portion, with a resultant check to root-development. In the warmer districts lucerne sown in November will usually be at a suitable stage for a first mowing in early February, and often a second cut will be available in April. In cooler districts the first cut may not be obtainable until late February or March, and unless the season is a favourable one a second cutting may not be advisable, although generally a second light cutting will be possible about the middle of April. The final cutting for the season should be carried out before the commencement of the dormant period of the crop; some growth on the plants during the winter is desirable for it fosters the stronger development of the rootsystem, and to some degree competes with and checks the invading weeds. MANAGEMENT FACTOR. At the end of its first winter a lucerne stand may contain a heavy population of weeds; indeed, on this account the lucerne crop may seem to possess every promise of a failure. The next few months probably constitute the most critical period in the life of the crop. However, provided the lucerne plants are present in satisfactory numbers and have been able during the previous months to develop strong root-systems, there is no essential reason why with suitable management a weedy crop should not become a success. When the new growth coming from the crowns is approximately two inches high, which frequently will be the case about September, the vegetation that has been standing during the winter may be removed by mowing, which should be adjusted so as to . leave three to four inches of stubble. Mowing in this manner may with benefit be made an annual practice, and if mowing is not carried out at this stage then at times light grazing is advantageous, but a field should not be grazed in its first year. Further, the heavier the soil the less likelihood is there of benefit from such grazing. At this stage top-dressing could suitably be carried out.

Generally the new growth, which should be allowed to grow unchecked, provides a cut towards the latter part of November. It is likely that year after year this first cut will contain a substantial proportion of weeds, inclusive of plants which ordinarily are useful, but which when invading lucerne are weeds. Partly because of its weed content and partly because the weather usually prevailing at this period is unfavourable to haymaking, the first cut of lucerne is as a rule most advantageously used for ensilage. Further, because of the weeds in the first cut it should be made enough to avoid ripening of the weed-seeds. CULTIVATION. Principally as a means of reducing the competition of weeds, cultivation of lucerne is at times well worth while. For such cultivation to be of value, it is essential firstly that the lucerne be not greatly damaged, and secondly that the cultivation be done under the conditions which will most greatly reduce the competition of weeds. In view of these requirements it follows that the implement employed should be fitted with tines designed for lucerne cultivation, that the use of disc harrows is generally too severe, and that dry summer or autumn conditions should be chosen for the work. As a rule a suitable time for such cultivation is after the second or third cuts; the dry weather which then is commonly experienced assists in the destruction of the weeds. Cultivation of lucerne has proved of value most commonly on open porous soils on which weeds may be disturbed effectively without at the same time materially injuring the deep-

rooting lucerne. It is certain, particularly on the heavier types of soils, that cultivation has at times resulted in more harm than good, because it has led to a gradual thinning-out of the lucerne plants until eventually they become so sparse as to make the area unprofitable. A method that is proving a useful modification of simple cultivation of lucerne which is being invaded by weeds is practised widely in parts of the North Island. This consists in sowing in late April or early. May from one to one and a half bushels of Algerian oats on stands which have been well cultivated shortly after having been mown or grazed. The cultivation injures the weeds and provides a seed-bed for the oats, with which about two cwt of superphosphate to the acre is usually applied. The oats furnish good feed in the spring, if required, and subsequently there will be available a heavy cutting of a mixture of oats and lucerne. It is as a rule highly advisable to use foi- silage the material thus provided. If it is not mown at an early stage the oats by shading the lucerne will unduly weaken it and thereby more than counterbalance the good they have done by checking persistent weeds. The success of the practice of growing oats with lucerne in this manner- will depend to some extent on the texture of the soil. The practice is followed almost wholly on friable soils.

Cultivation under relatively wet or cold conditions is an unsound practice; it merely injures some of the lucerne plants without leading to a useful reduction of the weed competition. Suitable cultivation can be carried out by use of the tine harrows or of a light spring-tooth cultivator possessing specially narrow teeth.

If stem-rot (Selerotinia trifoliorum) has appeared in a stand of lucerne cultivation is most inadvisable, as it assists in the spread of this disease by tending to scatter infected soil. In order to enable crops infected with stem-rot to survive in a useful condition as long as possible the aid to weed suppression provided by cultivation must be replaced by specially good management in respect to such matters as time of mowing and adequate manuring.