Model based estimation of nitrogen fertilization recommendations using agrometeorological data K. Christian Kersebaum WMO Expert meeting Geneva 11/2004

Outline Introduction Modell description Examples for applications on farm level Applications for groundwater protection Requirements for agrometeorological services

Introduction Weather conditions have a strong impact on crop growth and soil processes and their interactions. Nutrient, especially nitrogen management is therefore a challenge due to the annual variability of nutrient demand by crops on one side and nitrogen support from the soil on the other. The adoption of fertilization considering the supply from the soil and the demand of crops in their temporal behaviour is important for an economically effective use of fertilizer and for environmental protection avoiding leaching of surplus nitrogen to water ressources. Measurements of soil and crop nutrient status are only representing a snapshot with limited temporal validity. Process oriented simulation models provide to help in the estimation of spatial and temporal variability and probable future developments

Methods: Scheme of the nitrogen model HERMES

Kersebaum & Beblik, 2001 predicted N demand covered by subsequent doses actual weather data site specific weather scenario N-uptake mineral N in root zone time net-mineralisation next development stage for fertilization N deficiency Fertilizer application N-deficit occurs day of recommendation Methods: Scheme of model based fertilizer recommendations

Results of 3-year fertilizer trials with different methods (41 field trials from agricultural advisory office Hannover ) Fertilizer efficiency = additional yield per kg N-fertlization compared to Zero plot Fertilizer efficiency, rel. % yield, rel. % Winter barley Winter wheat Winter rye Zero model chloroph. model chlorophyll 100% = recommendation based on soil mineral N analysis

Messpunkte Corg [%] [kg N*ha ]: Grid sampling to get spatial information of soil properties and state variables on field Autobahn/Beckum Stone content texture organic initial N min -content matter ( )

Results: Spatial patterns on field Autobahn

Model based nitrogen fertilizer recommendation for winter wheat in 2000 on field Autobahn

Reduction of nitrogen leaching through model based site specific fertilization compared to a uniform fertilization of the usual farm level (185 kg N/ha) Total fertilzer saving for 20 ha field: 256 kg N

Simulated average yields and their variations in a period of 11 years on field Autobahn (average precipitation 800 mm) Yield [ dt ha -1 ] Coeff. variation [ %]

Restrictions for fertilizer recommendations for winter wheat to match the drinking water quality standard of 50 mg nitrate/l in seepage water Estimation of zones with fertilization restrictions max fertilization [kg N ha -1 ] Set aside

Relief effects on spatial distribution of model inputs Clay content Relative irradiation annual average 1998 Corg-content Topographic wetness index Digital elevation model (laser scan 1x1 m grid)

SRAD-Validation (12d - field)

Observed and simulated yield distribution of spring barley in 1998 Yield spring barley observed

Experimental design of fertilizer trial on Sportkomplex Kersebaum et al., 2003

Fertilizer: kg N/ha yields 2000 yields 2002 Fertilizer: kg N/ha Comparison of different fertilizer recommendations on Sportkomplex Zero N min +Sensor HERMES SS HERMES HERMES -30% Zero N min +Sensor HERMES SS HEMES HERMES +30%

Requirements for agrometeorological services The model requires weather data on a daily basis: Precipitation Air temperature (2m) Humidity (average or 2 p.m. depending on evaporation formula) Global radiation or sunshine duration Optional: wind speed Upto now the model works mostly in conjunction with automatic weather stations because accessability of upto date data with a high spatial resolution is limited. Longterm site specific data sets are desirable to create specific weather scenarios for predictive simulations. 3-5 day forecast can be used to adopt the fertilization schedule to site specific requirements (e.g to avoid nitrate leaching).

Thank you for your attention

Simulierted N-leaching Austräge für Acker und Grünland bei unterschiedlichen Böden und Düngungsintensitäten

Effekt der Jahreswitterung auf N-Aufnahme, Restnitrat nach der Ernte und N-Auswaschung

Topographic shading ( )