Fertilizing Bedding Plant Seedlings
Wednesday, 11 January 2012 15:33
Fertility is an important factor in the production of high quality seedlings by the plug method or traditional row or broadcast methods. Recent research has shown that fertilization must begin shortly after germination and that abnormal seedling growth is often caused by nutrient disorders.
The success of a fertilizer program for bedding plant seedlings and transplants is determined by more than just the rate (ppm) of fertilizer applied. Other factors which are as important as rate include fertilizer type (NPK analysis, micronutrient package, proportion of ammonium (NH4) vs. nitrate (NO3), and pH effect), frequency of application, volume of fertilizer solution applied, and how much leaches from the container. Also the growth rate of the young plant as it is affected by light intensity and temperature influences the fertility requirement of the plants.
Plug researchers have identified four stages of seedling growth and have developed guidelines for fertilizing each stage (below). Fertility is not a critical factor for most species during Stage 1 because most seeds have enough stored nutrients to carry out germination. Also, many germination media have a starter charge of fertilizer which is effective at supplying nutrients as the root emerges and elongates. The most important factors for germination are temperature of the growth medium and a proper balance between moisture level and aeration. Beginning in Stage 2 a dilute fertilizer program is normally started and the rate of application is gradually increased as the seedlings grow larger and approach transplanting.
Seedling or plug stage of development using a water-soluble fertilizer program
Stage 1: Germination and root emergence. No fertilizer
Stage 2: Opening of the cotyledons. 25-50 ppm N
Stage 3: Development of 1st set of true leaves. 50-100 ppm N
Stage 4: 1st set of true leaves to transplant. >100 ppm N
For more information, see the fact sheet: Fertilizing Bedding Plant Seedlings
by Doug Cox, University of Massachusetts
