Submitted to: BARC Poster Day
Publication Type: Abstract only
Publication Acceptance Date: 3/16/2009
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Nitrogen is a dominant factor in crop nutritional status. It is the most easily absorbed nutrient by maize crop and has the largest effect on yield. Knowledge of the factors governing maize crop N demand is essential to predict the needs of the crop under a wide range of field situations. To conduct plant-based N nutrition diagnosis, it is essential to establish a critical N concentration (Nc), which is the minimum N concentration necessary to achieve maximum growth. Several authors have shown that Nc declines as a function of aerial biomass accumulation (W): Nc = 34.0W-0.37. This Nc – W relationship has been shown to be a promising diagnostic tool of N status in maize. However, when applying this Nc-W relationship in maize N status diagnosis, knowledge on both biomass and nitrogen concentration of the whole aerial part are needed, making the diagnosis process both labour intensive and time consuming. The goal of this study is to evaluate the applicability of the established Nc-W relationship in maize nitrogen status diagnosis. There are three specific objectives: 1) to study if the established relationship can be used to describe the nitrogen status of maize crops; 2) to study the possibility of using the measured nitrogen concentration of specific organs (leaf, stem etc) in analyzing nitrogen status of a whole maize plant; 3) to establish a quantitative relationship between leaf SPAD meter measurement and maize leaf nitrogen concentration. Biomass of shoot and specific organs, N concentration, as well as SPAD meter measurement of specific leaves, were determined bi-weekly during the growing season at four sites for 2 years (2007 and 2008). The measured N concentration of the whole plant followed the trend described by the Nc-W function quite well, confirming the validity of the Nc-W function. However, the Nc-W function generally underestimated the measured nitrogen concentration through the growing season in both years, suggesting that there were excessive nitrogen applications of nitrogen fertilizer in these two years. Nitrogen concentration measured from different organs indicated that whole plant nitrogen status can be represented by the nitrogen concentration of the youngest leaf. Quantitative relationship between nitrogen concentration and SPAD meter measurement was established and validated. The established relationship between SPAD measurement and leaf nitrogen concentration strengthened the applicability of the critical Nc - W relationship in the diagnosis of maize nitrogen status.