Latest Briefing in Sustainability and Communities for 2010

Towards a low-nitrogen future

Efficient use of nitrogen (N) by plants is critical for maintaining future crop productivity as artificial fertilisers become more costly to produce. Global N fertiliser use for crop production has increased approximately seven-fold in the last 50 years, enabling crop production to keep pace with population growth. However, the economic and energy costs of high N inputs to arable systems are not considered sustainable.

Production of artificial N fertilisers is expensive, requiring conversion of N gas into inorganic N, which relies on fossil fuels. The cost of N fertilisers has more than doubled in recent years, and prices are likely to increase further as fossil fuel supplies become limited. In addition, uptake and use of N fertiliser in cropped systems can be inefficient.

Globally, it has been estimated that only one-third of the N fertiliser applied to cereal crops ends up in the harvested grain. The N in agricultural soils is a major source of greenhouse gases such as nitrous oxides, and N can also be lost through leaching of nitrates into water courses. There is an urgent need for alternative crop management strategies to allow sufficient food production for human populations without exhausting global resources.

A combined approach is required to reduce our reliance on artificial N fertilisers for crop production. The key questions are:

1. What are the alternatives to chemically-synthesised N fertilisers? We need to consider alternative sources of N, including recycled farmyard and urban organic waste and green manures.
2. Can existing crop varieties maintain yield and quality with less artificial fertiliser and/or alternative fertilisers? We need new crop genotypes that are more efficient in the use of inorganic and organic forms of applied nitrogen.

Figure 1: Compost and slurry trials at Mylnefield, SCRI, showing the enhanced early development of the barley crop when quality green compost is used.

Published on 21 December 2010 in Sustainability and Communities

Briefings in Sustainability and Communities for 2010