ISHS Acta Horticulturae 511: XXV International Horticultural Congress, Part 1: Culture Techniques with Special Emphasis on Environmental Implications - Nutrient Management
NITROGEN DEMAND OF CUT CHRYSANTHEMUMS IN RELATION TO SHOOT HEIGHT AND SOLAR RADIATION |
| Author: | S. Zerche |
| Keywords: | Dendranthema x grandiflorum, cut chrysanthemum, year round, dry matter yield, shoot height, nitrogen uptake, solar radiation, water uptake, nitrogen demand, nutrient solution |
| Abstract:
For highly efficient nutrient management, environmentally-friendly culture techniques require sophisticated methods for nutrient application. Nutrient addition should reflect actual nutrient demand. Furthermore, nutrient and water supply must be synchronized with plant demand under fluctuating greenhouse climate conditions. To solve these problems, rapid analytical techniques and nutrient uptake models have been developed in horticulture. However, the necessity of relatively laborious analyses and determinations of model input parameters have prevented their commercial adoption. For this reason, we studied relationships between easily measured parameters of plant biomass structure, such as shoot height, plant density and dry matter production, as well as amount of nitrogen removal, water uptake and solar radiation. After analysing six data sets developed from hydroponically grown year-round cut chrysanthemums (cultivar ‘Puma white’) with a fixed plant density of 64 m-2, we found that actual dry matter could be accurately calculated from shoot height. Non-limiting supply of nitrogen resulted in constant nitrogen concentrations in dry matter during the entire growing period. This resulted in direct relationships between shoot height and nitrogen removal, which were well suited for calculations of nitrogen demand. The optimum nitrogen concentration in nutrient solution was determined as the quotient of nitrogen and water uptake rates, which were calculated from validated regression functions with current shoot height and solar radiation. The strategy for nutrient addition is to vary nitrogen concentrations of the nutrient solution (20 to 310 mg N*l-1) as a function of shoot height, leading to electric conductivities from 0.4 to 2.4 mS*cm-1 with constant relative proportions of nutrients. Thereby nutrient addition can easily be regulated by computer-controlled greenhouse irrigation. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
