Subsurface Broadcasting Modification To Drill Coulters

New Zealand Journal of Agriculture, Volume 72, Issue 1, 15 January 1946, Page 33

Subsurface Broadcasting Modification To Drill Coulters

By

DR. O. H. FRANKEL,

Wheat Research Institute, and

A. G. ELLIOTT, Crop Experimentalist, Department of Agriculture.

THE question of seed distribution in drilling has exercised the minds of agronomists and implement designers since drills were first invented. Obviously, for crops which do not get inter-row cultivation, a method of distributing seeds an equal distance apart would be the most favourable, since this would permit the best chance of development to individual plants.

I~XRILLS in commercial use do not DRILLS in commercial use do not and cannot attain this ideal, because rows —for grain sowing— 7in. apart, and because no drill mechanism has yet been invented which can achieve an equal spread within drill rows. It may be contended that broadcasting would achieve a more even distribution than drilling; but obvious disadvantages of this method are the shallow and uneven depth of sowing.

Cross Drilling That farmers are aware of the desirability of an even distribution is evident from the fact that some have resorted to drilling half of the seed in one direction and half in another, usually at right angles to the first, thereby achieving a distribution better than is possible in ordinary drilling, at the expense of going twice over the same area. Apart from the distribution of seed, z cross-drilling is pref erred, by some farmers who resort to wind sowing, since the stubble is said to hold up the wind rows better than the stubble of normally drilled crops.

From consideration of these facts Mr. J. E. Holland, of Avoca Valley, near Christchurch, concluded that the most advantageous seed distributor for many crops would be a device which would permit of broadcasting below, instead of on, the surface. Initially he viewed such a sowing method as especially valuable for small seedsparticularly grass seed on light plains land. Later, Mr. J. W. Hadfield, Director of the Linen Flax Division, drew his attention to the great importance of regular distribution for an even development of linen flax plants. The late Dr. F. W. Hilgendorf, who took a lively interest in Mr. Holland’s work, thought that subsurface broadcastingthe term was coined by him — also be of value for sowing cereals, especially wheat.

New Type of Coulter The new type of coulter was originally a combination of an ordinary drill coulter and a broad shoe. The latter provided a cavity about and below the bottom end of the drill

coulter. Attached to the coulter -was a deflector of shoehorn-like form, convex side up. and slanting down and rearward, so that the falling seed and fertiliser impinged upon it and were deflected by it. - This model is now superseded by a complete coulter, designed to give greater distance between front and rear coulter rows to eliminate sledging or soil blockage at the greater depths required for wheat and. peas. The designer claims that the new model will give an even better spread than j the original one. . The original and the new models distribute fertiliser with the seed. The experiments reported in this article were conducted with the original coulter. ■ The spread, though not always perfect, was sufficiently good to test the principle of subsurface broadcasting in its effect on yield. It is not . anticipated that the more recent development in comparison with the older type will materially raise yields. In the earlier trials, which were conducted with a normal type ,of drill, there was occasionally a slight tendency to sledging and soil blockage.' This tendency was removed in ; the later trials by a wider spacing between the two coulter rows. This principle which was incorporated in the new ~ design is now a . permanent feature. Distribution of seedlings was . good, though mot perfect. In the early growth stages the centre of each coulter was usually recognisable, the

density of seedlings diminishing with the distance from the centre.

Experiments with Wheat

If the new coulter is to be used for wheat, it must be shown to possess definite advantages. Though not specifically intended for wheat, it was decided to investigate whether wheat yields could be increased by its use. Experiments with the new coulter, tested against the standard type, were made in the 1943-44 and 1944-45 seasons. Since it was not known whether the new type of coulter would be at its best at the standard rate of seeding, or at a different one, some of the trials were laid down in a number of sowing rates, both for the new type and for the normal coulters. Further, a number of varieties were used to give the coulter a general trial. The trials were conducted on three types of soil —a stony silt loam at Oxford, a sandy loam at Templeton, and a silt loam at Lincoln.

Trials in 1943-44 The following yield figures in bushels per acre were secured from the trial at Oxford where sowings of Solid Straw Tuscan with this new type and the ordinary coulters were at the rate of 2 bushels per acre:— New type coulters .. 16.3 Ordinary coulters . . .. 17.2 Difference in favour of ordinary coulters of 0.9 bushels was not significant. There was a more even spread of plants on the new type coulter plots, although plants from adjoining coulter sowings did not meet —one-half to twothirds of each drill width was covered. In the trial at Templeton, Cross 7 was sown with the new type and the

ordinary coulters at rates of 1| and 2| bushels per acre. Yields in bushels per acre are shown in the following table:

New type coulters at 11 bushels 65.3 Ordinary coulters at 11 bushels 63.5 Difference in favour of the new type coulters of 1.8 bushels was not significant. . • " New type coulters at 21 bushels 77.3 Ordinary coulters at 21 bushels 68.2 Difference in favour of the new type coulters of 9.1 bushels was significant. Bird damage, which was more severe in this method than in ordinary sowings owing to the more shallow cover, adversely .affected early establishment in all plots. At a later stage, the heavier rate of seeding gave a better establishment than did the lighter one on the plots where the seed was sown through the new type coulter. Trials in 1944-45 At Lincoln, the varieties Hunters and Cross 7 were each sown at rates of It, 2, and 2| bushels per acre with the new' type and the ordinary coulters, and results are set out below: HUNTERS. Drill. 1j bus. 2 bus. 21 bus. Mean. New type .. 68.8 68.9 69.1 69.1 Ordinary .. 64.4 67.4 66.2 66.2 = I.Bo* Mean .. 66.6 67.8 68.6 *Significant difference. , CROSS 7. New type .. 62.8 60.8 62.9 62.2 Ordinary .. 61.4 65.2 62.5 62.9 Mean .. 62.2 63.0 62.7 Difference not significant. ,

It will be seen that with Tuscan at Oxford in 1943-44, the two coulters yielded practically the same. This was also the case with Cross 7 at Temple-

ton with 1| bushels of seed; but with the heavy, rate of 2J bushels, the new type of coulter gave an increase of 9.1 bushels per acre.

At Lincoln, in 1944-45, there were no significant differences in a trial with Hunters, at three rates .. of seeding; yet, in another trial in Cross 7, conducted alongside the first and treated in every way alike, the new type of coulter did markedly well in all three rates of seeding. , No substantial reason is yet apparent for these inconsistent performances. Yield increases for the new type have occurred on good land, but by no means in every case; they have occurred in Cross 7 and not in other varieties, but even in Cross 7 they have not been apparent every time; they have occurred at some rates of seeding and not at others, but there is no recognisable trend.

Moderate Promise Summing up these results, the new type of coulter increased yields sometimes, failed to at others, but . did not reduce yields in any of the trials. While, therefore, there is moderate promise of increased yields, the circumstances . under which these can be expected are complex and unknown. SHEEP IN N.Z. The number of sheep in New Zealand at April 30, . 1945, have been officially estimated at 33,975,000 — record. The latest figure ’• shows. an increase of 775,000 over the previous year’s total. The numbers of sheep in the respective classes are: Rams (560,000), wethers (2,526,000), breeding ewes (20,866,000) dry ewes (918,000), lambs (9,105,000).