Havaintoja muutamien nurmikasvien kehityksestä kylvökesän aikana

Abstract

The main part of grasslands in Finland are leys which are maintained 2 to 4 years. This is the rule, especially with regard to grasslands for hay, and during the last few years there has been a tendency to use pastures in a similar way. For these reasons it is necessary to sow about 300 000 hectares of new grasslands per year in the country. In Finland drought is very common in spring and summer, and it often delays or prevents the germination of seeds and hampers the development of small seedlings. Failures at the establishment of new leys are mostly due to drought. In order to establish succesful leys, the development of the seedlings of ley plants, above all the development of their underground parts, roots, must be known. And the most important thing is to know the very first development of the plants. In order to throw some light upon these problems, some observations were made concerning the very first development of the most important ley plants. In order to obtain suitable material for observations, various grasses and clovers were sown on the University farm, Viikki, in a suburb of Helsinki, in the spring of 1950. All plants employed at the test were sown separately, as stands of single crops. There were plots with nurse crop (barley Tammi) as usual, as well as plots without any nurse crop. During the summer 1950 regular observations were made on the development of the aboveground and especially the underground parts of the different plants. For the plants growing without any nurse crop, the dates of observation were towards the end of June, at the beginning and the end of July, towards the middle of August and towards the middle of September. For plants growing under a nurse crop, observations were not made until after the harvesting of the nurse crop (Aug. 11th), viz. towards the middle of August and towards the middle of September. The technique employed at the observation of the underground parts was that developed by the writer of this paper and employed by him in an earlier investigation (5). Main results of the investigation. Plants growing without nurse crop. The development of the aboveground parts is most clearly shown by yields (as oven-dry material) obtained at harvesting, September 5-th. They were: red clover 359 g. per m2, alsike clover 288 » white clover 157 » timothy grass 35 » cocksfoot 151 » meadow fescue 56 » red fescue 32 » Kentucky bluegrass 0 » Species of clover and cocksfoot produced yields corresponding to a fair yield of hay, but the others produced very little, and Kentucky bluegrass nothing whatever to be harvested. As to the underground parts, roots, the following facts can be stated: All species of clover were similar with regard to the development of the roots. The roots of red clover developed most quickly. Already by the beginning of July the depth of the roots was 35 cm. for red clover, 25 cm. for alsike clover, and 15 cm. for white clover. Even after that the depth of the roots increased rapidly. By the middle of September the maximum depth of roots was 105 cm. for red clover, 95 cm. for alsike clover, and 105 cm. for white clover. Thus the roots of all the investigated species of clover reached a considerable depth already during the first growing season. The development of timothy grass was very slow at the beginning. By the beginning of July the roots had only reached a depth of 6 to 7 cm. And even after that the development of the roots was continuously slow, e.g. the number of roots increased slowly. By the middle of September the roots had reached a depth of 18 cm. With cocksfoot and meadow fescue, the development of the roots was similar. In a short time the roots of both plants reached a depth of about 10 cm. Already in July the number of roots was considerable, but they mostly grew laterally, so that the increase in depth was slight. By the middle of September the maximum depth of the roots was 23 cm. for cocksfoot and 18 cm. for meadow fescue. With red fescue and Kentucky bluegrass, the root development was also similar. Of all the investigated plants, their root development proved the most slow. As late as the end of July the maximum depth of the roots was only about 10 cm. By the middle of September the maximum root depth was 20 cm. for red fescue and 15 cm. for bluegrass. Plants grown under a nurse crop. On August 11th when the nurse crop was harvested, the aboveground parts of all investigated plants were very little developed. The seedlings evidently suffered badly from drought, whereas the plants growing without a nurse crop did not seem to suffer from it. Some rains occurred at the end of August, but even after the rainfall the seedlings developing under a nurse crop recovered very slowly. At the beginning of September there was nothing to be harvested on the whole area. The underground parts were also very little developed by the middle of August. Only clovers had reached the maximum root depth of over 10 cm., with cocksfoot and meadow fescue it was about 10 cm., with timothy grass, red fescue, and bluegrass it was considerably less than 10 cm. By the middle of September red clover had reached a depth of 30 cm., alsike clover 25 cm., and white clover 20 cm. Timothy grass only reached a depth of 10 cm., cocksfoot 11 cm., meadow fescue 12 cm., red fescue 10 cm., and bluegrass only 8 cm. With grasses growing under a nurse crop, primary roots retained a good condition much longer than with grasses growing without any nurse crop. The most interesting thing about these observations is the extremely harmful influence exerted on all ley plant seedlings by the nurse crop.