Salaojituskoetoiminnasta Suomessa

Authors

• Taneli Juusela Maataloushallituksen vesiteknillinen tutkimustoimisto , Helsinki

DOI: https://doi.org/10.23986/afsci.71334

Abstract

According to the agricultural census of 1950 about 124.000 ha., or 5,4 % of the field area, have been deep-drained on farms with more than 2 ha. field. Of this, 50 % are tile drainage, 15 % nailed wooden case or bored wooden pipe drainage, while about 35 % are drained by other methods, which for the most part consist of brush drainage. Only 10 % of the field area is nowadays cultivated without ditches: the total cultivated area drained with open ditches amounts to almost 2.000.000 ha., and the total length of the open ditches to at least 1.600.000 km. About 1.400.000 ha. have been calculated to be in need of deep-drainage and also worth deep-draining. The increasing use of machines in field cultivation has made it urgently necessary to determine the best way to eliminate the disadvantages caused by open ditches. If this work were to be carried out with the present deep-drainage methods, it would take at least 200 years at the present speed, and would cost over 100 milliard marks, calculated according to present prices. However desirable deep-drainage may be, it is hardly possible to realize it with sufficient speed and to its full extent. By using the present methods such an undertaking would exceed the capacity of our agriculture, owing to the great expense involved. Deep-drainage in Finland is generally more expensive than in many other countries. This is not only due to the differences in soil and climate or the high level of prices and wages, but partly also to the special character of our deep-drainage. Thus we use a 30—50 cm. deeper drainage here in Finland than in Sweden, yet the drain distances are almost the same in the two countries. The present methods used in deep-drainage are based partly on the practice that prevailed abroad in the nineteen-twenties, and partly on the belief of the farmers themselves and the deep-drainage experts in the general need for drainage of the cultivated land. The recent trials have unfortunately been limited and scattered. Their results have, however, shown that the method of drainage has affected the crop yield to a surprisingly small extent both where open drainage and deep-drainage are concerned, provided that the side and main ditches have been in order and waterfurrows have been used to a sufficient extent. That the need for drainage seems to be smaller than expected may in part be due to the fact that the ploughing depth has been almost doubled during the last 20—30 years, and that the tilling has become more efficient than before, owing to the increased use of tractor-drawn tillage implements.
The scope of the trials
In order to solve the drainage problem finally, in the early spring of 1951 the Ministry of Agriculture appointed a special committee of deep-drainage experts, to draw up a plan of the experiments and trials to be carried out all over the country. Mr. A. H. Schroderus, chief engineer at the Board of Agriculture, was appointed chairman of the committee, which otherwise consists of Mr. Veikko Ihamuotila, B. Sc., Dr. Taneli Juusela, Prof. Pentti Kaitera, Prof. Lauri Keso, Mr. H. Korpela, M. A., Mr. Eino H. Seppänen, engineer and Prof. Otto Valle. A general scheme for the trials was confirmed by the Ministry of Agriculture on May 24, 1951. At the same time Dr. Taneli Juusela was appointed by the Ministry to direct this work at the hydrotechnical bureau of the Board of Agriculture. Mr. Erkki Pälikkö has worked from the beginning as the agricultural expert in charge of the investigations. In case of need, students of agronomy have also been used as summer assistants in field work. In tasks such as surveying etc., it has continuously been necessary to employ additional labour. The main part of the scheme consists of the setting up of experiment fields for deep-drainage to be started at four state-owned farms. These are completed by separate experimental areas to be established mostly at private farms in different parts of the country. The expenses involved by the surveying, planning, drawing up of documents, and inspection are financed out of special founds granted for the investigation. Thus these expenses will not burden the owners of the experiment farms. On the other hand, the farmer himself is responsible for the actual drainage work, being granted however, the customary deep-drainage compensation and loan. Experimental deep-drainage areas are to be set up on 143 farms in all. They are divided according to their purposes as follows:
Experiments on need of drainage 10 farms
» » drain depth 40 »
» » drain distance 80 »
» » mole drainage 10 »
» » gravel drainage 3 »
Grants for the basic phase of the trials have been obtained from the Ministry of Agriculture out of funds intended for the promotion of agricultural production and for levelling the costs of same. The annual grants have been as follows:
1951 4.500.000 mk
1952 10.350.000 »
1953 5.623.000 »
Total 20.473.000 mk
An attempt is being made to have the foundation work of the experimental deep-drainage areas and fields ready within the year 1953. The sums needed annually for the care of the experiment areas and for the treatment of the data obtained are included in the annual budgets of the hydrotechnical bureau of the Department of Agriculture.
The purpose of the trials
The aim of the drainage trials is to discover and develop methods, better both in terms of ultimate yields and of costs, for use in different circumstances. On the whole, the problem is not only one of deep-drainage. The purpose of the experimental deep-drainage work is to find out when and what kind of deep-drainage is needed and to what extent the fields can be cultivated either entirely without drainage or by using open ditches at greater distances than are used at present.
Investigations regarding different drainage methods. When trying to discover more profitable drainage methods than the present ones notice has been taken of the fact that about 44.000 ha. or 35 % of the deep-drained field area has been drained by the famers themselves, using their own materials. In the investigation carried out on about 7.300 ha. of fields thus drained, about 80 % of them werse found to be brush drained. Stone drainage amounted to 15 % and gravel drainage and drainage carried out with various other methods to 5 % of the area investigated. Of the brush drainage, 74 % was in good condition, 22 % satisfactory and only 4 % poor, in spite of the fact that about a quarter of the drains were over 30 years old. Consequently, carefully done brush drainage remains active for an average of at least 30 years. The expences of brush drainage are in general less than half those of tile drainage, provided that no price is counted for the timber (about 5 cu.m, needed for 100 metres of drain). The use of this kind of drainage can still be recommended as a solution preceding deep-drainage on small farms where home labour is easily obtainable. As far as stone drainage is concerned, the conclusion has been reached that there will not be much chance of utilizing this method, owine to the great amount of work involved. Gravel drainage has so far been used to quite a small extent in this country, but it is evident that expenses could be cut down by using this method in regions where gravel of suitable particle size is available in great quantities and the transport distances are not too long. For the purpose of ascertaining the effects of the depth of the drains, the amount and quality of the gravel, the effects of the soil, and the declivity, a few experimental deep-drainage areas will be set up on private farms, situated mostly in parts of the country where this method may find general application on account of the availability of gravel. On the basis of the experiences lately gained in Sweden of mole drainage it is to be supposed that this kind of drainage would be suitable especially on the mud and mud clay areas of Southwest and South Finland, and perhaps on a larger scale also on the heavy clay areas. Besides the investigations regarding the distances and depths of mole drains, the purpose of the trials is to discover the relation between of the durability of the drains and the soil, declivity, frost and other possible factors.
Investigations regarding drain depth. A change over to a shallower deep-drainage would help to reduce the expenses of digging the deep-drains and the main ditches. When working out the technical requirements for such a measure, a study has been made of the oldest tile drainages in this country. The bulk of these deep-drainages are over 70 years old and are shallower than the present ones, with an average depth of only 70—90 cm. It is felt that it will be very much helpful to find out, amongst other things, to what extent frost damage and root stoppages are occurring in them. Besides the technical requirements involved in a change over to a shallower deep-drainage system, the effects of such a measure from an economic point of view have to be investigated. For this purpose the effect of drain depth on the crop yield will, amongst other things, be studied on the experiment areas which have been set up in different parts of the country. 60, 90, 120 and 150 cm. are the depths that have been chosen for comparison. Owing to the voluntary nature of the trials private farms cannot be burdened with a sufficient number of simultaneous experiments. The consequent unreliability of the experimental results is to be eliminated by increasing the number of the experiment farms correspondingly.
Investigations regarding drain distance. Where the number of drains per areal unit can be decreased, this will cause a nearly corresponding reduction in the total expenses on the deep-drainage work. Thus a change in the drain distance has considerably greater importance in this respect than a change in the depth. Consequently it is considered necessary, in connection with the trials in question, to set up, in addition, a considerable number of experimental areas to ascertain the optimum drain distance in different parts of the country. Two different methods are included in the scheme. The simplest and most general is the method of deep-draining one half of the experimental area by using the present drain distance, while on the other half every other drain is omitted, the distance being thus doubled. The other kind of distance trial is to be tried on farms where a combine is used. In these experiments the present distance, a double one and in some experiments an even broader distance are used alternately. The crops are harvested with the combine from strips parallel to the deep-drains. Consequently the changes in the crops are noticed when drawing farther away from the drain both where the drains are frequent and less frequent. Furthermore attempts are to be made to ascertain the effect of drain distance on the spring drying and its evenness as well as on the capacity of the surface to carry machines.