Media preparation for greenhouse production

• Good balance between physical properties like water holding capacity and porosity.
• The medium should be well drained.
• Medium which is too compact creates problems of drainage and aeration which will lead to poor rootgrowth and may harbor disease causing organisms.
• Highly porous medium will have low water and nutrient holding capacity, affects the plant growth and development.
• The media reaction (pH of 5.0 to 7.0 and the soluble salt (EC) level of 0.4 to 1.4 dS/m (deciSiemens permetre) is optimum for most of the greenhouse crops.
• A low media pH (<5.0) leads to toxicity of micronutrients such as iron, zinc, manganese and copper and deficiency of major and secondary nutrients while a high pH (>7.5) causes deficiency of micronutrients including boron.
• A low pH of the growth media can be raised to a desired level by using amendments like lime (calcium carbonate) and dolomite (Ca-Mg carbonate) and basic, fertilizers like calcium nitrate, calcium cyanamide, sodium nitrate and potassium nitrate.
• A high pH of the media can be reduced by amendments like sulphur, gypsum and Epsom salts, acidic fertilizers like urea, ammonium sulphate, ammonium nitrate, mono ammonium phosphate and aqua ammonia and acids like phosphoric and sulphuric acids.
• It is essential to maintain a temperature of the plug mix between 70 to 75ºF.Irrigation through mist is a must in plug growing.
• Misting for 12 seconds every 12 minutes on cloudy days and 12 seconds every 6minutes on sunny days is desirable.
• The pH of water and mix should be monitored regularly.