Influence of media, nitrogen sources, and N-serve on growth of container grown Callistephus chinensis "Pink Princess"

In commercial nursery crop production, several advantages can be derived from growing plants in containers, however, large volumes of material are required to fill these containers. Because physical characteristics of most natural soils are not completely desirable for container-growing, amendments are usually added to improve the growth of plants. Plants are also frequently grown in mixes entirely devoid of natural soil. Although peat is the most commonly used amendment, the list is long and diverse. Soilless media have a lower capacity for fixing and storing nutrients so they have to be fertilized earlier and more frequently. Efficient methods of supplying nutrients for plant uptake are needed in containers, not only because of the low storage ability of the substrates, but also because large quantities of water are added to a relatively small volume of media which can lead to high leaching losses. Several approaches have been taken to improve the efficiency of nutrient uptake and use by plants. This can be achieved by reducing nutrient losses from the soil-crop root system and by regulating nutrient use by the plant. Generally speaking, four major approaches have been used and these are: 1. Supplying soluble fertilizers at regular intervals to the plants (i.e., split dressings). 2. Development of fertilizer compounds of limited water solubility (e.g., I.B.D.U.). 3. Altering the nature of soluble material so as to retard their release in the soil solution (e.g., Osmocote). 4. Development of chemical additives to control soil microbial activities affecting the release of fertilizer nutrients (e.g., nitrification inhibitor). The present study was designed to study the effects of three commercial New Zealand container mixes (peat/sand (1:1), peat/sand/sawdust (1:1:1) and peat/sand/soil (1:1:1), and four kinds of fertilizers (urea (NH₄)₂S0₄' IBDU and osmocote), and their interactions with a nitrification inhibitor (N-Serve) on the growth of Callistephus chinensis "Pink Princess" (Asters). The various container mixes were characterised physically and chemically so as to relate these properties to subsequent performance of Aster plants in the various mixes