Farm Business Survey 2021-22: Farm level emissions and nitrogen usage

Measuring farm nitrogen (N) use

Nitrogen is an essential nutrient for plant growth. Nitrogen supplied by fertiliser, soil and other sources are consumed in harvested crops and animal products. However, excess nitrogen can also be lost to the wider environment. Losses of nitrogen to the environment can have harmful effects on, for example, climate change, biodiversity, air quality and water quality.

Definitions

Nitrogen use is measured by:

• Nitrogen balance (kg N surplus per hectare)
• Nitrogen use efficiency NUE (% N output / N input)

Nitrogen balance is the difference between total nitrogen input and ouput. A higher balance indicates less efficient use of nitrogen. It provides an estimate of the size of the nitrogen surplus not being captured in agricultural products that is potentially available for losses.

Nitrogen use efficiency (NUE) is the ratio of nitrogen outputs to inputs. It indicates the proportion of nitrogen used in the farm system. This measure allows for better comparison across farms. NUE values should always be interpreted in relation to nitrogen surpluses and nitrogen outputs.

A higher NUE typically indicates a more efficient use of nitrogen but very high values may indicate unsustainable “soil mining”. The best range of NUE values depends on the type of farming activity as well as environmental conditions, livestock types and feed types.

Nitrogen estimates are based on standard estimates of nitrogen content in farm inputs and outputs. The amount of nitrogen is estimated for all farm inputs and outputs up to farm gate, where possible. Limited information is available for some inputs and outputs.

Results are shown for the average (median) farm. Organic farms are excluded from these estimates as limited information is collected on their use of biological fixation of nitrogen. As such, the results are not directly comparable to results published on farm income. Error bars show the upper and lower quartiles and demonstrate the variability of emissions.

More information can be found in Data sources and more information.