The Wardlow site is home to the some of the earliest and longest running nitrogen (N) deposition experiments in the world.

Established in 1995, on acidic and calcareous grassland, this experiment investigates the effects of nitrogen addition on upland grasslands and includes interactions with phosphate. 

Atmospheric nitrogen deposition is among the top three threats to biodiversity. It is estimated that by 2050 global N deposition will be almost twice as high as at the beginning of the 1990s. 

This site forms one of many under the UKREATE umbrella project funded by the Department for Environment Food and Rural Affairs (Defra) and the Natural Environment Research Council (NERC). 

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Treatments

As the main form of N deposition in upland areas is wet deposition, the treatments have been applied monthly, with N in distilled water applied  as a mist using a backpack sprayer.

Treatments rates range from  those similar to historical deposition levels, 35 kg N ha−1 per year (equivalent ambient deposition in 1995), to a 140N treatment that equates to application rates used in current agricultural practices.

A series of plots have now had their N treatments ceased, allowing the study of recovery of these systems along side the continued study of ongoing N deposition effects.  

Main study areas include impacts on botanical composition including flowering, soil microbial functioning, plant nutrient acquisition and changes in soil chemistry.

For further information please visit the UKREATE website.

Please also download Jonathan Leake's summary of the grassland, soil and vegetation response to N addition at Wardlow Hay Cop here.