Studies on the composts for raising seedlings of vegetable crops in hot beds. VII.

Abstract

In the previous works standard formulas of the composts for raising seedlings of forced vegetables have been proposed. Composts were made of soils (volcanic ash soil, clay soil and fine sand), and organic material (leaf-mold) with optimal fertility. Suitable components differed from sorts of vegetable crops. For cucumbers, the 1 volcanic ash soil-3 leaf-mold mixture (in volume), for tomatoes 2-2 mixture, and for egg-plants 3-1 mixture were most favourable, respectively.The purpose of this study was to determine the physical properties of these composts, and to find the relation between these properties and plant growth.In the first experiment, moisture constants of the mixtures, varying in their proportion of soil and organic material, were determined. From pF-curves of soil water, it was evident that, with increasing proportions of leaf-mold to the soil, macropore spaces were increased markedly. On the other hand, amount of available water were decreased in both volcanic ash soil and clay soil except in fine sand.In the next steps, physical changes in the mixtures which received daily watering at the field for four weeks were observed. The actual volume of solid and liquid phases in each mixture was increased, accompanied with decreasing air capacities, because the sedimentation of the soil particles into macropores occured, and the mixtures became compact considerably during experimental periods. Addition of leaf-mold to the soil was effective for reducing soil compression, though the 3-1 mixture showed more compact than 4-0 component (no leaf-mold added) at the end of experiment.Last of all, the permeabilities of the mixtures to water and to air were measured in the laboratory, after daily watering for four weeks. Both properties indicated similar tendencies, though there were great differences concerning to the soil types. There were noticeable improvements in the water-and air-permeability when leaf-mold was added to the soil. However, just as in the case of the former experiment, 3-1 mixture showed lower rate than other mixtures.It appears from these results that the application. of bulky organic matter to the soil altered remarkably physical characteristics of the composts. And also, it was suggested that their properties may affect on the growth of vegetable seedlings, particularly, on the development of their root. And it was considered that suitable components were determined by mutual relationship between nature of plant root and physical properties of mixtures, and consequently they differed with sorts of vegetable crops.