Suitability of different crop parameters for the determination of site-specific nitrogen fertilizer demand
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In order to investigate the suitability of different plant characteristics to be used for the derivation of site-specific N recommendations, a series of 10 field trials with winter wheat and winter barley was conducted in 2001 through 2003. The trials were set up as small plot trials with various N rates and different seed densities. Plant samples were taken at the time of second and third nitrogen dressing. At harvest, yields were measured. Yield response functions and optimum N rates were calculated. The investigated plant parameters biomass, N content and N uptake were negatively correlated with optimum N rate. Higher coefficients of determination at the 3rd N dressing indicated a stronger relationship later in the season. Comparing the three plant parameters, the closest relationship to optimum N rate was detected for the parameter N uptake, followed by the parameters N content and plant biomass.
It is concluded that approaches which determine the in-field variability of N uptake are most suitable for the derivation of site-specific nitrogen fertilizer recommendations.