OVERDRILLING WIDELY USED

Press, Volume XCVIII, Issue 29004, 19 September 1959, Page 8

OVERDRILLING WIDELY USED

Review Of Farm Practice As a result of last summer's intense drought many farmers in the North Canterbury and Christchurch areas were forced to consider alternative methods of quickly and cheaply renovating their drought-stricken pastures. One of the methods most widely used has been the direct overdrilling of established pastures with grasses, clovers and cereals, both alone and in combination. This technique has been used under a surprisingly wide range of conditions and with a worthwhile measure of success, although the development of grasses and clovers so introduced will naturally be governed by the future course of the weather.

Reviewing the experience of a cross section of farmers in the Christchurch and in North Canterbury districts who have used this method to restore pastures and supplement their feed supplies, Mr D. J. Davies, an instructor of the Department of Agriculture in Christchurch, who has been supervising trials of cereal introduction, says that in general drills of two distinct types have been used. The most popular has been the disc drill and to a lesser extent the conventional rigid coulter drill fitted with Blackmore points and specially adapted for the job. In some cases a special high country sod seeder developed by the extension division of the Department of Agriculture has been used. Field trials laid down with this machine are at present being evaluated and the results of these will be presented later in the year.

Mr Davies says that it would appear from field experience that some of the disc drills, where the coulters are independently spring mounted, are able to overdrill very stony soils—in the riverbed category—and in general are the more versatile of the two machines. Nevertheless, there still locks to be room for modification of these machines to incorporate at least a device to prevent bridging of the furrow slice in heavy soils so that there is no imprisonment of the seedlings under the lip of the furrow. Most Valuable The soil and moisure conditions under which drilling has been done have been many and varied. Soil conditions have ranged from light sandy and stony soils to medium-heavy stiff clay loams, and much of this work was done under extremely dry conditions so that in many instances seed did not germinate until the drought broke in March. In general, however, farmers would probaly be prudent to delay drilling until soil moisture was adequate to enable quick germination of the seedlings and to reduce bird interference to a minimum.

Field experience has indicated that because of ease of penetration it is easier to overdrill established pasture on the lighter sandy soils than bn the heavier soils, but this does not mean that results are necessarily any better on the lighter soils and indeed more often than not the reverse is the case.

Ryegrasses, and particularly short rotation, have been widely used for renovating pastures which have become clover dominant The type of seed mixture

has been largely determined by conditions on the particular farm and the' circumstances prevailing at the time. Species which have been successfully introduced, apart from the ryegrasses, have been cocksfoot, red and white clover and subterranean clover.

Where cereal varieties have been introduced satisfactory results have been largely confined to the heavier, more fertile soils, although good results have also been obtained on undulating hill country. The varieties used have been largely of two types—the fast producing types like Garton, Russet and Winter Grey oats and Cape barley and the long producing varieties, the best of which have been C.R.D. ryecorn, Wong and Research barley and to a lesser extent Arawa wheat. In some cases grass has been successfully established with oats when sown in the autumn, but in no cases have the oats continued to give production through to the spring. Wide Variation Several farmers have said that the contribution of feed by the cereals was most valuable. For instance, one farmer with a big ewe flock used hardly any hay this winter and for six weeks after early lambing had no worries about feed. On this farm Research barley overdrilled into the stubble immediately after harvesting of a barley .crop has given a tremendous amount of. winter feed—about five grazings since early in the year and ewes and lambs were still on it this week when it was still showing a fair amount of feed. In this particular field subterranean clover has also made a useful contribution to the overall position. Another farmer who overdrilled soft turnips was able to use three acres to carry through 250 ewes for five weeks during the early winter. Other farmers have, however, not always had such satisfactory results with turnips. Most farmers have used at least lewt of superphosphate at sowing. It is felt, however, that in some instances the application of some nitrogenous fertiliser would have been beneficial for initial growth and subsequent development of the feed.

Management procedures have varied according to the payability of the species in the sward at the time of sowing. On the more fertile soils better establishment of introduced grasses has been achieved where the pasture has been grazed by sheep immediately after sowing to reduce competition from established

species and weeds and to allow root development of the introduced species. The best results have been obtained with cereals where the grazing has been fairly frequent—that is when growth has reached about three or four inches in height In the case of fast growing oats under dairy farm grazing systems best results have been obtained where maximum leaf growth has been allowed to develop and the feed has then been rationed on the break principle with the electric fence. In this case only one large grazing of greenfeed can be expected. While heavy rains in May made grazing of some of these paddocks difficult in every case the feed grown was completely utilised because of the firm ground conditions. This was in striking contrast to greenfeed grown under the conventional system. A lot of wastage occurred last winter on cultivated ground with poaching and bogging down of cows.

Town Milk Farm On the town milk supply dairy farm on high fertility soils Mr Davies believes that the technique of growing a greenfeed crop on top of an existing pasture has been proved a success this year. Where these farmers have irrigation systems it would be possible in a dry season to use water to bring the introduced species through, but that was not necessary last autumn. The main points arising out of the introductions since last summer are: (1) the high proportion of successful establishments of grasses, clovers and cereals under a wide range of soil conditions; (2) the versatility of the disc drill for overdrilling on light, stony soils and into stubble, and the successful results obtained with the convenentional drill, especially adapted, on heavy soils where shallow V grooves., with good crumb structure for covering the seed have been obtained: (3) the most suitable conditions for overdriljing are where the soil

moisture is adequate and the pasture has been grazed bare; (4) weeds in general have provided little competition; (5) complete utilisation of feed has been possible, particularly where cereals have been grown under wet winter conditions; (6) the method allows utilisation of unploughable hill country on which conventional cultivation would be unwise because of the risk of erosion; (7) in the present state of knowledge normal seeding and fertiliser practices have given satisfactory results; and (8) the overdrilling of depleted pasture in the autumn has resulted in the establishment of almost a brand new pasture by the spring without loss of production and in many cases with substantially increased winter growth. Points still under study are: (1) the usefulness of overdrilling in the spring; (2) the manurial requirements, of particularly cereals on various soil types; (3) the selection and testing of further cereal varieties; and (4) the design or modification of machinery for this type of work. Many farmers under pressure of circumstances have embarked on overdrilling, says Mr Davies. The proof of the usefulness of the technique will be whether they continue to use it in the future.