TREATMENT OF THE DUNES IN HOLLAND.

New Zealand Journal of Agriculture, Volume XVIII, Issue 3, 20 March 1919, Page 150

TREATMENT OF THE DUNES IN HOLLAND.

From Conservation des Dunes: Plantations dans les Dunes des Pays Bas, by E. D. Van Dissel, Inspector of State Forests and Cleared Lands, Holland.

Translated by

E.Phillips Turner

The dunes of Holland extend in a long chain along the North Sea., They occupy an-area of about 92,625 acres that is to say, nearly-1-15 per cent, of the surface of • the country. ■ They are almost entirely composed of sand with a mixture—more, or less abundant—of broken shells and other material. This sand may show differences as great from the chemical as from the physical point of view. The nature - of the sand exercises a . great influence on its instability and on the vegetation. - It- is where the dunes are driest and -where their soil is the poorest that the sand is most mobile , the wind raises it in places and- disperses it as dust, this causes holes ; at the same time the vegetation in these places is not vigorous enough to oppose the . action of the wind with an effective resistance. It goes without saying that it is just.there, that it is important to fix the dunes by planting marram (HmwopAiZa arenaria), or by making an effort to plant trees on them. One must always understand that the lands that are most in want of these remedies are also those where it is most difficult to apply them.

FIXATION OF DUNES WITH MARRAM, ETC.

The oldest plan for fixing the soil of dunes consists in planting marram on them, and it is still the means generally resorted to.

This kind of grass, which grows on almost all dunes, develops itself best in those places where the wind brings plenty of sand. That comes about from its forming stems at the joints, where new stalks and roots can be produced. In time, thus extending itself under the influence of the dust from the sand, the plant succeeds in taking possession of a considerable area.

Where the marram increases abundantly supplies are obtained to serve in the fixation of the dunes. The plants are cut in the middle with a small spade at about 4 in. beneath the surface of the soil, but naturally care is taken to have plants in sufficient number. The cut plants are tied in bundles and carried to the place where it is proposed to fix the dune.

The works decided on for this fixation are begun by rounding off the edges of the holes made by the wind, and if necessary the projecting parts of the dunes, because it is there that the wind has the most effect. Narrow holes are then made with the spade in the sand, in which are placed at regular intervals bunches of marram, which are pressed down with care. If one does not lay out with marram, straw is sometimes substituted for it. (Note : Generally marram and straw are used, as a rule planting only marram where it is found in abundance at hand and where the highest seas cannot reach it.)

The bunches of marram are spaced on the slopes at about 12 in. by 12 in., and in the more level places about 20 in. by 20 in. Provided one does not use' too old plants (for example, plants not more than two years old), and that the stems have joints, the marram will put forth roots and spread. " If that has not taken place it will be necessary to maintain the ordinary repair—to fix the dune afresh and that generally at the end of three years, because then the stems of the marram are rotten. Where; however, the soil of the dunes is better there will have grown during this time, besides the marram, other plants which will help to fix the dune. ; ' >

Where, sufficient heather grows in the hollows {pannes} it is cut and used for the fixation of the dune. The heather is spread in thin layers on the ground and weighted down in the middle with shovelfuls of sand. This is more expensive than the use of the marram. In return, this kind of covering turns out to be more effective in the very dry parts where the marram does not take, and the maintenance of it is not onerous. -

The results of the methods described here are relatively of little durability, and necessitate considerable expense in maintenance and renewal. Afforestation, on the contrary, is capable of fixing the dunes in a permanent manner.

AFFORESTATION OF THE DUNES

The experiments in afforestation not only of the dunes belonging to private persons but also those of the State date from a long way back. Well known is the trial made by the State in 1865 and the two following years on the dunes of Schoorl. There were then used the following species of- trees : Pinus Laricio var. austriaca, P. montana, P. silvestris, P. maritima, and Picea excelsa. Unfortunately the planters had no experience ; many of the young plantations perished from want of care, and the results, obtained with the others were only partly successful. This attempt has at least not only shown particularly that' the three first species named above can give excellent results, and that Pinus silvestris succeeds very well in sheltered places, but that Picea excelsa and above all Pinus maritima are unfitted for this use. •

New trials have been made since the year 1893 on the dunes in the neighbourhood of Schoorl. At first, following the example of Denmark and Jutland, they planted chiefly Picea alba. This species, however, has been found unsuited for the afforesting of the Dutch dunes. They have therefore had recourse particularly to the species used at the trials of 1865 and 1867. The young plants are raised in nurseries situated near or on the dunes. They endeavour to obtain young spruces from two to three years old, not too big, but with fibrous and long roots very important conditions, seeing the dryness of the dunes.

As a rule, preparation of the soil can be dispensed with in situations where the sand is mostly dust, the soil being there generally sufficiently mellow and containing enough moisture.

It is necessary before afforesting dunes to suitably fix them, in order to preserve the plantations against the dust from the sand. They use for that (after having rounded off the sharp ridges) heather, marram, or straw in the manner that we have described.

If, however, the dune harbours much vegetation it is necessary to prepare the soil, because in this case it is generally not sufficiently moist for spruces to thrive in it. At times this is done by means of a special shovel, with which are made holes from about 12 in. to 20 in. deep in which to put the young trees. For some years, however, more care has been taken with this work ; with an ordinary shovel are made trenches from 10 in. to 12 in. deep, even making this digging as deep as 20 in. in places much covered with plants and in those where the soil is poor and sterile. After this operation the soil ought to be naturally fixed afresh. In the dune-hollows the soil is fairly firm and humid ; there are dug trenches about 20 in. deep, and, if required, they are provided with borders to ensure them from an excess of water. Among the species enumerated those which succeed the best are (1) P. Laricio austriaca, (2) P. montana, (3) P. Laricio corsicana, and in sheltered places P. silvestris raised from Scotch seed. The plants are put in at a distance of from about 23 in. to 31 in. apart. In places most exposed to the wind they space at a less distance, and plant principally P. montana, which stands the violent winds and quickly covers the soil. Besides the conifers, broad-leaved trees are planted in the better places where the soil is sufficiently moist and sheltered, but it is necessary to prepare the soil carefully. Those concerned have expressed themselves as particularly satisfied with alder and oak; they have besides made trials on a small scale with other broad-leaved trees.

The afforestation of dunes in Holland is met with considerable difficulties. Not only do the winds, but also numerous parasites, hinder vegetation, and as much damage is done by the prevalence of animals as by the vegetable pests. Among the pests may be mentioned different species of Retinia, Pissodes notatus, Cneorrhinus geminatus, Hylesinus piniperda,' Lophyrus pini, Polyphylla fullo, Agaricus melleus, Coeoma pinitorquum, and Hy st enum pinastri. One is obliged to be always on the lookout to fight these enemies at the right time. It happens also that the soil is very poor. To this is added the great difficulty of planting enough broad-leaved trees, which increases the danger from fires. In spite of all, the results, particularly in recent years, have been more encouraging.. Without doubt afforestation means a much enhanced initial expenditure, but as against this the expense of maintenance is reduced to a minimum, and one can even see some pecuniary profits in the future, without mentioning the advantage that will be obtained from the aesthetic and climatic point of view. .1 even estimate, not reckoning the eventual profits, that in the long-run the fixation of dunes by means of afforestation will turn out more advantageous than the costly use of marram, &c., which involves each year great expense in maintenance-.

The. “ Anconia. Sheep-dip ” Case.— In the Journal for March, 1918, a warning was given regarding a worthless preparation termed the Anconia sheep-dip, then lately placed on the market by one J. C. Harrison. After the lapse of a —delays being caused by Harrison's flight from the Dominion and somewhat protracted legal proceedings after his return under arrestthe case ended in Auckland this month, by the accused being convicted of fraud and sentenced to six years’ imprisonment. Harrison was shown to have a bad criminal record in Australia for similar frauds.

Invaluable features in the control of field-crop insects are cooperation, clean farming, and a suitable scheme of crop-rotation, the last arranged according to the presence of any likely insect pest, thus breaking the continuity of the food-supply of such an insect.