Helle Sønderbo

Ph.d.-studerende

Helle Sønderbo

Profil

Title: Prediction of nitrogen leaching based on soil content of mineral nitrogen

Project description:

A key issue in modern agriculture is the amounts of nitrogen fertilizer added to the fields versus the resulting effects on the water environment. The issue is how to reach a balance between obtaining the highest possible yield in the crop production while the leaching nitrogen do not harm the water environment. It is a key element to be able to determine the actual nitrogen leaching from agricultural fields in order to come closer to this balance.

The predominately part of the nitrogen leaching from agricultural fields happens during the late autumn and winter months when the precipitation is higher than the rest of the year and similarly with the plants growth and nitrogen uptake.

Based on the knowledge of the soil and nitrogen cycle in the soil-water system it seems reasonable that the soil content of mineral nitrogen (SMN) in the autumn months could be an important factor for the size of the yearly nitrogen leaching.

This PhD will focus on this relationship between the leaching and the soil mineral nitrogen content and aim to describe this by an empirical model.

In addition this PhD project will also investigate another model used in Denmark for prediction of nitrogen leaching called N-LES.

The specific objectives of this PhD project are to:

  • Develop and calibrate an empirical model that can predict N leaching from the root zone based on autumn field measurements of mineral N in the soil, soil type, water balance, N fertilizer level and crop cover (summer and winter crops) in the actual year.
  • Investigate the spatial variation of soil mineral nitrogen in an agricultural field and give recommendations for a best practice for autumn sampling of mineral nitrogen in order to use the sample as a predictor for the nitrogen leaching.
  • Investigate the time-related variation of soil mineral nitrogen in the autumn months (start of October to start of December) and give recommendations for a best timing for sampling of mineral nitrogen in order to be used as a predictor for the nitrogen leaching.
  • Develop and calibrate an empirical model that can predict the content of mineral N in the soil based on information of N leaching from the root zone, N fertilizer level, crop cover and soil type
  • Re-calculate the marginal response effect of nitrogen fertilizer and other parameters and re-design the model function for this sub model in order to improve the overall performance of the NLES 4 model.

This should contribute to the development of new regulations methods and more cost-effective methods for optimizing the fertilization and management strategies in order to reduce the N leaching to the aquatic environment.

ID: 87091993