Nitrogen balances of different organic and conventional farming systems

From the report “Nitrogen balances and nitrogen-use efficiency of different organic and conventional farming systems“, from Hung-Chun Lin, Julia A. Huber, Georg Gerl and Kurt-Jürgen Hülsbergen, published in Nutrient Cycling in Agroecosystems by Springer

Nitrogen (N) is the most important yield-limiting factor in agricultural systems, however, N application can lead to emissions and environmental problems such as global warming (N2O) and groundwater contamination (NO3 ).
The conventional farming systems in this study were high N-input and high N-output systems. The conventional arable farming system had the lowest nitrogen-use efficiency and the highest N surplus. An optimised N management and the use of high-yielding crop varieties improved its nitrogen-use efficiency.
The establishment of conventional agroforestry resulted in the reduction of N input, N output and N surplus, while maintaining high yields. The organic mixed farming system is characterised by a relatively high N input and N output, the accumulation of soil organic nitrogen, the highest nitrogen-use efficiency, and the lowest N surplus of all analysed systems. These good results can be attributed to the intensive farm N cycle between soil–plant–animal. The shift from organic mixed farming to organic arable farming system extensified the N cycle, reduced N input, crop yield and N output.
As conclusion, the change from organic arable farming to organic agroforestry reduced the N input, increased the biomass yield, and remained the N surplus within an optimal range.