Drilling Seed into Tussock Grassland

New Zealand Journal of Agriculture, Volume 84, Issue 3, 15 March 1952, Page 221

Drilling Seed into Tussock Grassland

A TRIAL of a new method of introducATRIAL of a new method of introducing seed into tussock grassland by drilling it into an unprepared surface with a grain drill the coulters of which are fitted with special penetrating' points is described in this article by L. W. Blackmore, Instructor in Agriculture, Department of Agriculture, Timaru. Comparisons' are made between the effectiveness of this method compared with broadcasting and the use of a drill without special points. The trial also showed that both grasses and clovers could be established satisfactorily by this method. An added advantage was that phosphatic fertiliser could be placed close to the seed. The good establishment of white clover particularly is attributed to the method of sowing and the placement of the fertiliser.

THE success of surface sowing of seed on native or established pastures depends largely on the rainfall, the tightness of the sward, and the amount of roughage present. Even with the most favourable climate the chances of introduced seed being established are greatly reduced where existing vegetation prevents it from making direct contact with the soil. Under adverse climatic conditions, especially where the ground is likely to dry out quickly, contact with the soil is not sufficient to ensure establishment. Best results are secured when the seed is placed in the soil, preferably with manure in close contact to ensure satisfactory establishment. This can be achieved by either of two methods, one by cultivating and then drilling, and the other by drilling directly into the sward without any preliminary working. This article deals with the second method.

In October 1948 the Department of Agriculture laid down a trial in the Mackenzie Country in which various grasses and clovers were sown on tussock country by both drilling and broadcasting. The area, about 2000 ft. above sea level, was typical of many square miles of unimproved tussock land on the Mackenzie Plains. For most 'of the drilled area the coulters of the drill were fitted with special “grassland” tips. These consist .of specially designed castings with hard steel along the lower leading edges and bottoms. Because of their comparatively sharp, downward - tilted point, these attachments give the coulters greatly increased penetration. The action of the tip is as follows. When the drill is in motion the leading edge, which is comparatively sharp, cuts open the sward. This cut is opened to the full width of the point as the drill moves forward. The seed and manure fall in and the cut partially closes behind the coulter. A more complete cover of the seed may be obtained by light harrowing. The harrows may either be attached to the drill or used separately. The most suitable type of harrow to use depends on the nature of the country. Where tussock is present a long-tined harrow of a flexible nature such as the tripod has been found very suitable. Operation When the grassland tip is used the bottom of the tip (heel end) should be flush with the coulter point so that maximum support is given to the tip. The lower leading edge should be slightly dipped (see diagram) to give maximum penetration. The drill can be adjusted in two ways to achieve this penetration. First, the amount of “rake” on the coulters may be varied (the tips are made to operate when the hand lever is in the middle position for the Duncan type of drill and the forward position for the Massey type), and second, the hitch may be raised or lowered. After the tips have been used for some time penetration may

be reduced by wear. This can. be overcome by lowering the hitch a little, but it is better to build up the tips again with hard steel. To increase penetration and to reduce “skipping” to a minimum a spring-pressure drill should be set to exert a working pressure of about 101 b. per coulter. It is likely that on very uneven ground a drill without spring pressure, but with independently weighted coulters, would give a more uniform depth of sowing over the bumps and hollows, because the coulters would then be free to follow the contour of the ground surface. On rough going, however, drilling must be slow for good results. Comparison with Ordinary Points In the trial standard drill points were tried out against others fitted with the special tips described. - The tips have three main advantages:— 1. They ensure better and more even penetration, as was shown by the fact that seed established well in tussock. 2. They provide a good cover for the seed. After the tip passed over the surface it left a V-shaped depression into which the seed and manure fell. This is an advantage under very dry conditions, especially where little vegetative cover is present, as the seedling is protected in its early stages of development from the full effects of drying winds. Further, as the seed is on a firm bottom, it has all the advantages of being sown under conditions of good consolidation. This important advantage would largely be lost if the land was hustled before drilling. 3. They are self clearing. Because of their ability to penetrate readily, the points fitted with tips cleared much better. As the lower leading edges of the tips were almost constantly below the surface, trash could not collect under them and cause the points to ride on the surface.

Comparison with Surface Sowing To compare the strike and establishment from surface broadcasting with that of drilling in the way described a block in the trial was sown broadcast by removing the coulters and allowing the seed and manure to fall on to the surface. The strike and establishment in the drilled area were strikingly better than in the broadcast block. The reasons for the difference appear to be that the bulk of the drilled seed was effectively placed in the soil .whereas part of the broadcast seed was either caught up in the tussock or other vegetation or at best lay on the surface of the soil and exposed to the vagaries of the weather. The drilled seed was, on the other hand, assured of a more continuous supply of moisture, while the fertiliser placed in direct contact with the seed gave quick establishment. Over 20 different species and strains of plants were sown by this method. Very good strikes were obtained with lucerne, sweet clover, crested wheat grass, white clover, and subterranean clover. The strike of the clovers was particularly good due to drilling and placement of the fertiliser.

It is doubtful whether • the strike and establishment of seed sown in the broadcast area were one twentieth that of the drilled portion, in spite of the fact that the conditions for establishment were better than average for the district. The average rainfall is between 15in. and 20in. per annum. When the present high cost is considered the establishment in the broadcast area could not possibly be regarded as an economic proposition. In view of the lesson learned from this trial the wisdom of surface sowing in areas of low rainfall is very much open to question. Uses of Grassland Tip The grassland tip would appear to have possibilities for introducing seed into native pasture where ploughing is not desirable or economic. For instance, it is likely to be valuable on tussock country where it is essential to retain the tussock or where wind blowing of ploughed or worked soil is a problem. A further possible use is for the introduction of clovers into pasture where these have failed to establish successfully. The tips have been tried out for the surface introduction of subterranean clover on light, stony soil, but though they met

with a measure of success, they were not very satisfactory under these conditions because the stones prevented good penetration and wear was excessive. The best procedure in such conditions is first to • hustle twice in the same direction with narrow points, then drill with no pressure on the springs, and finally cover with the harrows. Lack of .consolidation round the seed if the weather after drilling is dry is the chief disadvantage of this method. The attachment of grassland tips to the coulter points of a drill shows promise for the surface drilling of grassland under certain conditions. The tips have yet to prove themselves for use on a wider, scale. However,, they would seem to be worth a trial where conditions appear suitable. Oversowing Hill Country SOME 70 co-operative trials on the introduction of clovers on hill country are being conducted by the Department of Agriculture as part of a topdressing; improvement programme. These trials are, a continuation of trials carried on since 1939 and aim at finding the most suitable, clovers for different classes of hill country, the best time for sowing, the most suitable, conditions for oversowing, and the best! stock management for oversown areas. WHITE clover is recommended for oversowing on the more fertile types of hill country, where the rainfall is between 45 and 50in. a year. Topdressing with phosphates is essential to the establishment and good growth of white clover. Subterranean clover is recommended for sunny, dry faces and on all country with under 45in. of rain a year. Phosphatic topdressing is also essential for the establishment and good growth of subterranean clover. Lotus major is recommended as a pioneer legume with or without phosphatic fertilisers in highrainfall districts. Satisfactory establishment and growth have been, obtained with red clover on the better soil types with 45 to 60in. of rain a> year. Time of Sowing In the trials all clovers have shown, better establishment from autumn than from spring sowings. Generally the earlier the seeding in the autumn the better the establishment, providing thedry summer weather has broken and there is no prolonged dry spell after seeding. Rate of Seeding The trials indicate that the strike is? more affected by climate, type of soil, area of ground, time of sowing, and. other factors than by the amount of seed sown. Very satisfactory strikes, have been obtained by seeding rates, of to 21b. of white clover per acre, 3 to 41b. of subterranean clover, Jib. of Lotus major, and 3 to 41b. of red clover. Stock management after sowing is important, particularly the spelling of newly established subterranean clover pasture to allow reseeding.

—C. J HAMBLYN,

Fields Superintendent, Department of Agriculture, Palmerston North