ROOTING HABIT OF NORTHERN SPY APPLE STOCKS.

New Zealand Journal of Agriculture, Volume 47, Issue 6, 20 December 1933, Page 362

ROOTING HABIT OF NORTHERN SPY APPLE STOCKS.

C. E. Woodhead,

Plant Research Station, Palmerston North.

In a previous article, in this a brief account was given of the rootstock- investigations which are being carried out at the Plant Research Station, and reference was made to a botanical study of a large number of stocks grown from root cuttings. During this particular investigation some interesting facts were noted in regard to the vigour and root characters of the Northern Spy stocks which form the greater part of the collection. These stocks, grown from root cuttings, afford an interesting comparison with others of the same variety propagated by the usual method of “ layering.”

Fig. i shows two-year-old Northern Spy stocks grown from root cuttings, and Fig. 2 Northern Spy stocks of the same age produced by layering. There is a marked contrast between the root-systems of the two types ; note the strong and almost vertical roots of the former, and the relatively slender and horizontal roots of the latter. The difference in vigour of top growth is equally remarkable, the stocks grown from root cuttings having an average height and girth of 6 ft. 8 in. and 3I in. respectively, and the layered stocks 3 ft. 8 in. and 2% in. respectively. The disparity in growth suggests a definite correlation between vigour and type of root-system, with the depth of rooting as the significant factor.

Some four-year-old layered stocks (Fig. 3) show the surface rooting habit still persisting, only a small proportion of the roots exhibiting a downward tendency. These stocks were cut back to ground level two years ago, and the stems are in consequence younger than the roots. Typical trees of the three classes of stock are contrasted in Fig. 4.

It is, of course, possible that with increasing age the present differences in vigour and root habit may become less marked or even be eliminated. Furthermore, tests will be necessary to determine whether the relative vigour of the two types of stock is reflected in the scion. Any conclusions, therefore, drawn at this stage must necessarily be tentative.

The experience of other workers is of interest in this connection. Knight, Amos, Hatton, and Witt ( 2 ), in discussing methods of vegetative propagation employed at East Mailing, state: “ Stools, layers, hardwood and softwood stem cuttings, and root cuttings have all been used to multiply root stocks or varieties on their own roots . . . it is significant to observe here that in the case of a variety (Brom' ton) which has been propagated by every one of them, the resulting plant has the same characeristics, by whatever means it is obtained. There is apparently no difference in root character or general vigour, which is thus dependent upon inherent qualities of the plant. This is to be expected, but it is important in view of the necessity of using different procedure for different varieties.” Their findings are thus contradictory to those of the writer, but it should be noted that the example given is that of a.

plum variety. The data given above relative to Northern Spy stocks show that the method of propagation employed has a marked influence' on the type of root-system produced, and also suggests. (a) that the root type bears a definite relationship to the vigour of' the stock, and (&) that the degree of vigour is in direct ratio to the depth of rooting.

The importance of deep rooting in relation to the vigour and productivity of fruit-trees is shown by Oskamp and Batjer( 3 ) in a. study of the size, production, and rooting habit of apples on various soil-types in New York. They found that “ Trees in the betterdrained soils root more deeply, as a rule, and even though these deeper roots make up only a small percentage of the total rootsystem, they seem to have a stabilizing influence on the orchard as indicated by tree size and yield." In New Zealand the fact that the largest trees were almost invariably the deepest rooted was noted by Orchard Instructors in some districts when collecting root cuttings for the present stock survey.

The Northern Spy stock has been thoroughly tested, in thiscountry and has many good qualities. It is immune to woolly aphis, and varieties worked on it come into bearing early and produce highly coloured fruit of the finest quality. For thesereasons it should hot be lightly discarded for stocks of unknown: performance under New Zealand conditions. Its one serious disadvantage ■ is that on some types of soil and in combination with certain scion varieties it apparently lacks the vigour necessary to produce a tree of satisfactory size and high cropping capacity. If it can be established that a more vigorous type of Northern Spy stock is to be obtained by propagation solely from root cuttings, the only serious objection to the use of this variety as a stock will be removed.

Literature cited. : (J) Allan, H. H. and Woodhead, C. E. : : Apple Root-stock. Investigations.. New Zealand Journal of Agric., Vol. 46, pp. 256-259. ( 2 ) Knight, R. C., Amos, J., Hatton, R. G., and Witt, A. W. : TheVegetative Propagation of Fruit Tree Rootstocks. East Mailing Res.. Sta. Ann. Rep. for 1926-27 (Oct., 1928), II. Supplement, 13. ( 3 ) Oskamp, Joseph, and Batjer, L. P. : Soils in Relation to Fruit Growingin New York, Part II. Cornell Univ. Agric. Exp. Sta. Bui. 550, 1932.

Group Control of Mammitis in Dairy Herds. The Director-General of Agriculture refers to this method in his annual report for 1932-33 as follows r “The grouping system of milking dairy cows, commenced last year, for the control of mammitis in herds has been continued and has given promisingresults. The scope of this work experimentally is controlled by the staff available, as the arrangement of cows in order established by preliminary microscopic examination of milk and . the. subsequent examination necessary entails extensive concentration on. detail. The reports to hand and covering fifty herds over two seasons show that distinctly beneficial results have been, obtained, and the scheme can be definitely advised under ordinary conditions."