Muokkauskerroksen alla olevien maakerrosten merkityksestä kasvinviljelyssä

Authors

• Martti Salonen Yliopiston kasvinviljelystieteen laitos

DOI: https://doi.org/10.23986/afsci.71291

Abstract

The root systems of all crop plants are partly situated in subsoil, but under the conditions prevailing in Finland, the bulk of roots are in the ploughed layer. Is it then possible for plants to take water and nutrients from the subsoil? Investigations have been conducted in order to find out the significance of subsoil as the environment of roots, but experiments have been carried out either as pot tests, or in subsoil after removing the surface soil above it. It is evident that if the subsoil is no longer in its natural condition underneath the ploughed layer, considerable changes occur in it, at least in its physical properties. It would, however, be most interesting to find out what is the significance of the subsoil as such, in its natural condition, to plants. In order to illustrate this problem, a test method was developed, according to which it is possible to grow plants (oats) in ordinary undisturbed soil by means of subsoil only. Seeds were sown in glass tubes and the plants grew through these without having any contact with the ploughed layer (Fig. 1). The tubes were filled with quarts sand, free of all nutrients. Roots could not spread in the soil until after penetrating through the tube. It was observed that they did not begin to grow upwards after penetrating into the soil. Control plants were grown in usual manner beside the test plants. Yields per plant obtained from plants grown in this manner are given in centigrammes in Table 2. It is seen that it is possible for plants to grow by means of subsoil only. Individual plants of oats developed normally, they even yielded some grain, but remained very small in size. Thus subsoil can supply plants with all necessary nutrients, though their amounts are very small. Great natural variation of individual plants resulted in high standart errors for various treatments, but mean differences between various treatments were also so great as to make the differences statistically significant. A survey of the values of t in Table 2 shows that mean differences were significant between plants receiving nitrogen and those grown without nitrogen. From this it is possible to draw the conclusion that nitrogen is the nutrient the subsoil most of all lacks.