Avoiding nitrogen losses and leaching

Leaching is a complex problem and there is no single solution.

In addition, soil organic matter and mineralization builds up over many years. These important parameters can be changed only gradually from one year to the next. Strategies to reduce leaching exist and have been tested. Which factors should be included?

Applying best farming practices (BAT)

Leaching is limited when best agricultural practices are applied. Recommendations include:

  • Choose high yield crops that use available nitrogen efficiently
  • Determine soil mineral nitrogen content by frequent sampling
  • Use split application to adjust nitrogen availability to actual plant needs, ensuring rapid uptake, especially on sandy soils
  • Ensure balanced nutrition (P, K, S) to optimize nitrogen uptake 
  • Allow for a deep and extensive root system as to utilize nitrogen more efficiently
  • Apply fertilizers and manure accurately, well away from watercourses
  • Consider buffer strips between agricultural land and watercourses
  • Maintain green cover as long as possible to absorb excess nitrogen (cover crops, early drilling of autumn-sown crops)
  • Make sure that green cover is re-established rapidly upon ploughing of set-asides and grassland
  • Keep a porous soil structure to avoid surface run-off and sub-surface bypass flow on heavy soils
  • Avoid application of fertilizer and manure in autumn 
  • Use reliable nitrogen recommendation systems, considering spatial and temporary variations of soil nitrogen supply

Adjusting fertilizer input 

Adjusting fertilizer input to actual plant needs is the best way to control residual nitrate and thus leaching. Nitrogen uptake varies between years, fields and crops. It depends on the soil’s mineral nitrogen content, mineralization rates, yield expectations and weather conditions. Since it cannot be reliably predicted, actual plant needs should be assessed accurately and fertilization split into several adjusted applications. Precision farming tools, such as the Yara N-TesterTM and N-SensorTM allow plant needs to be measured on the spot and in real time.