Models for nitrogen uptake and quality assurance in horticultural and agronomic crop production
A main scientific objective in modeling research is to analyse fundamental relationships determining growth and quality characteristics of crop production systems. Further mathematical interpretations e.g. models finally enable an economic growth and quality control in horticultural and agronomic crop production. Thus, modern growth and quality control systems have to contain reliable decision tools determining nitrogen demand of crops to maximize yield with ensuring quality of products and environment. Moreover, these model tools have to meet demands of crop growers for easily measured growth and climate input parameters. Principles and results of nitrogen demand modeling presented here aspire an efficient control of nitrogen nutrition and nitrogen affected product quality in different horticultural and agronomic crop production systems.
Models for nitrogen uptake: Comparable principles for nitrogen uptake prognoses via canopy structure and environmental growth conditions in horticultural and agronomic crop production are used as demonstrated by Zerche (1997), Zerche (1998) and Zerche and Hecht (1999). These principles are demonstrated for modeling nitrogen demand in production of ornamental cut flowers (Dendranthema (syn. Chrysanthemum) Grandiflorum Hybr.), flower cuttings (Dendranthema, Pelargonium Zonale Hybr. – for identic plant reproduction) and cereal crops (Triticum aestivum; Hordeum vulgare; Secale cereale). They are based on common relationships between easily measured parameters of plant biomass structure, such as shoot height, plant density and dry matter production, as well as amount of actual nitrogen removal, water uptake and climate parameters like solar radiation and growth temperature.
Models for quality assurance: At Chrysanthemum (Ch) and Pelargonium (P) stock plants differently supplied with nitrogen, cuttings were grown, which nitrogen concentrations of dry matter ranged between 2 to 8 %N (Ch) and 2.5 to 5 %N (P) as documented for Chrysanthemum by Zerche et al. (1999). Then correlation relationships between nitrogen concentration, subsequent root regeneration of cuttings and shoot fresh and dry mass of rooted young plants were examined with data sets of trials carried out during four years under different environmental conditions and as presented partly for one year by Druege et al. (2000). Resulting first model functions could predict cultivar specific rooting capability of chrysanthemum cuttings as related to its nitrogen concentration and shoot fresh mass of young plants. Further models are developed for nitrogen and water uptake of stock plants as functions of temperature and radiation to control optimum nitrogen concentrations of 4.0±0.3 %N in Pelargonium cuttings.
It is concluded, that presented models control nitrogen nutrition by close connection to nitrogen uptake course for ensuring high yield and product quality. They also are beneficial in that they can consider the actual course of plant growth as feedback mechanism for nutrient demand prognoses in horticultural and agronomic crop production.
Zerche, S.; Druege, U.; Kadner, R. 2001 Models for nitrogen uptake and quality assurance in horticultural and agronomic crop production. Abstract, Modeling for the 21st Century: Agronomic and Greenhouse Crop Models. Programm and Abstracts of a Joint Meeting of the Biological Systems Simulation Group and International Society for Horticultural Science, 25.03.-29.03.01, Beltsville, Maryland USA