Offered Papers Theme C: Delivering the Benefits from Grassland
Description
The Nitrogen Nutrition Index (NNI) is based on the concept of a critical nitrogen concentration, defined as the minimum N concentration in the aerial biomass necessary to obtain maximum yield. Values of Ncrit are high at the start of the growing period and decline during growth, in relation to dry matter accumulation (t DM/ha) according to the equation of Lemaire & Salette (1984): Ncrit(%) = 4.8(DM)-0.32. The NNI is calculated as the ratio of the actual N concentration of the sward to the N concentration required at a similar biomass to sustain non-limiting growth and biomass accumulation (Lemaire & Gastal, 1997). However, the evaluation of NNI requires the determination of aerial biomass per unit area, in addition to the determination of N concentration. This is time-consuming and is a practical limit to using NNI on farms. The objective of this experiment was to assess NNI by a more practical and easier method based on the determination of the N concentration in the upper leaves, as proposed by Gastal et al. (2001).
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Agricultural Science Commons, Agronomy and Crop Sciences Commons, Plant Biology Commons, Plant Pathology Commons, Soil Science Commons, Weed Science Commons
Assessment of the Nitrogen Nutrition Index (NNI) by the Nitrogen Concentration of the Upper Part of the Sward
The Nitrogen Nutrition Index (NNI) is based on the concept of a critical nitrogen concentration, defined as the minimum N concentration in the aerial biomass necessary to obtain maximum yield. Values of Ncrit are high at the start of the growing period and decline during growth, in relation to dry matter accumulation (t DM/ha) according to the equation of Lemaire & Salette (1984): Ncrit(%) = 4.8(DM)-0.32. The NNI is calculated as the ratio of the actual N concentration of the sward to the N concentration required at a similar biomass to sustain non-limiting growth and biomass accumulation (Lemaire & Gastal, 1997). However, the evaluation of NNI requires the determination of aerial biomass per unit area, in addition to the determination of N concentration. This is time-consuming and is a practical limit to using NNI on farms. The objective of this experiment was to assess NNI by a more practical and easier method based on the determination of the N concentration in the upper leaves, as proposed by Gastal et al. (2001).
