STUDY OF THE THEORY AND TECHNIQUES OF SELECTING MEDIA FOR SOILLESS RAISING OF VEGETABLE SEEDLINGS

Because the prices of vegetable products are low in our country, it is essential to select suitable media for Soilless Raising of Vegetable Secdlings(SRVS). These media should have rich natural resources and low cost, meet the requirements for the anchor of the root systcm of seedlings and provide adequate moisture, nutrition and air, Various materials may bc used for the media of SRVS, e.g, coal cinder, charred rice husk, peat, and vermiculite.In the three tables included in this paper, the physical characteristics of the SRVS media that arc commonly used at different areas in our country, the contonts of nutrient elements of some of the media, and the contents of nutrient elements of the peats at some areas in our country these tables provide the basicdata for the selection of a SRVS mono-medium at an area in our country.Both a mono-medium and a combined medium containing several diffcrcnt media mixed in a proportion may be used for SRVS. If a mono-mcdium can not meet the demands of the SRVS, a desirable combined medium may be made by mixing several media which are complenting in their properties. A good medium, mono-medium or combined medium, should has ideal physical characteristics. In this paper it is suggested that the diameter of a ideal medium ranges from 0.1 to 0.8g/cm³, the total porosity is from 54 to 133% and the ratio of air and water is 1 to 4, The contents of nutrient elements in medium is not the most important thing. If the charred rice husk is chosen as the medium,a proper readjustment of the prescription of the nutrient solution should be made according to the needs of the SRVS and the contents of nutrient elements in charred rice husk provided in this paper. Most vegetable crops prefer weak acidity. Theretore SRVS media and nutrient solutions should be adjusted to pH 6 to 7 before use.