Nutrient flows and balances

The sustainability of agro-food systems is at the centre of green growth considerations. There are three main concerns related to sustainability: food security, run-off of nutrients such as nitrogen (N) and phosphorus (P) from commercial fertiliser use and intensive livestock farming, and pesticide residues that may leach into surface water and groundwater and enter the food chain. Farming also contributes to climate change and can lead to deterioration in soil, water and air quality and to loss of natural habitats and biodiversity. These environmental changes can, in turn, have implications for agricultural production and limit the sustainability of agriculture. But farming can also provide sinks for greenhouse gases (GHGs), help conserve biodiversity and landscapes, and help prevent floods and landslides.

The main challenge is to progressively decrease negative impacts and increase environmental benefits associated with agricultural production. In this way, ecosystem functions can be maintained and food security ensured for the world’s growing population. This will require two types of interventions. First, the productivity and sustainability of agro-food systems must be improved through, for instance, better land management practices. In addition, pollution discharges from agriculture can be reduced through better management of nutrients (fertilisers and manure). Second, agricultural support measures linked to production that encourage intensive production and exacerbate the rate of biodiversity loss in the world must be addressed. Gains can also be expected from demand-side measures and changing consumption patterns (e.g. dietary preferences for red meat, as well as seasonal and local produce).

Progress towards green growth can be partly assessed against changes in agricultural nutrient balances and intensities. Nutrient balances indicate the level of potential environmental pressures from nutrients in the absence of effective pollution abatement. This is particularly true for soil, water and air.

Main trends and recent developments

Nutrient surpluses declined relative to agricultural output

For many OECD countries, nutrient surpluses declined both in terms of absolute tonnes of nutrients and nutrient surpluses per hectare of agricultural land (Figure 4.1). The rate of reduction in OECD nutrient surpluses has been faster in the early 2000s than before, but has slowed in recent years for nitrogen in some countries. Over the past decade, the value of OECD agricultural production increased by about 55% in real terms. Conversely nitrogen surpluses (tonnes) declined by about 16% and phosphorus surpluses by about 43%. These trends confirm the process of decoupling of agricultural production from environmental pressures related to N and P nutrients. They reflect some improvement in nutrient use efficiency by farmers.

The apparent consumption of commercial fertilisers per hectare of agricultural land compared to crop production reveal similar developments. On the one hand, consumption of nitrogen continued to rise (18% more in OECD, signalling relative decoupling). On the other, consumption of phosphate declined (4% less, signalling absolute decoupling) (Figure 4.2).

Yet in some countries fertiliser consumption is high and growing

In BRIICS economies (Brazil, Russian Federation, India, Indonesia, People’s Republic of China, South Africa) the apparent consumption of fertilisers per hectare of agricultural land increased sharply over the last decade, both for nitrogen (+36%) and phosphate (+48%) (Figure 4.3). Crop production value increased even faster (+143% in real terms), signalling a relative decoupling. However, the level of commercial fertiliser use per-hectare in BRIICS is, on average, about twice as high as in OECD countries.

There are sizeable variations within and between countries in terms of the intensity of, and trends in, nutrient surpluses and consumption. The variations depend on soil quality, cultivated crops (those that require high nutrient inputs, such as maize and rice) and local concentrations of livestock (associated with large volumes of manure) (Figure 4.1, Figure 4.4). Other factors that play a role include countries’ weight in international trade (e.g. Brazil is a major exporter of agricultural and food products) and farmers’ knowledge about appropriate fertiliser application methods.

Measurability and interpretation

The indicators presented in this chapter relate to agricultural nutrient balances and commercial fertiliser consumption. They include the following:

Nitrogen and phosphorus surplus intensities, expressed as gross nutrient balances in kilograms per hectare of agricultural land; see also Glossary.
Nitrogen and phosphate fertiliser use, expressed as apparent consumption of fertilisers per hectare of agricultural land; and compared to the gross production value in the agricultural sector.

These indicators describe potential environmental pressures, and may hide important spatial variations. The nutrient indicators are based on nutrient balances from primary agriculture. They do not consider nutrient flows from other food production systems, such as fisheries, or total nitrogen cycles in the economy. Agriculture, however, plays an important role in the nutrient cycle.

Nutrient balances (surpluses or deficits) expressed per hectare of agricultural land help the comparison of the relative intensity of nutrients in agricultural systems between countries. The estimation method used here does however not fully account for differences across countries, for example as regards differences in intensive agriculture systems that use double or triple cropping. Nutrient balance indicators should be read in conjunction with information on water use in agriculture, soil quality, biodiversity, land use, commodity prices, farm management and cropping practices.

Cross-country comparisons of commercial fertiliser use intensities should take into account the type of agricultural land to which the fertilisers are applied and the type of crops grown.

Sources

FAO (2017), FAOSTAT, Food and Agriculture Organization of the United Nations, Rome, http://faostat.fao.org (accessed in March 2017).

OECD (2017a), “Agri-environmental indicators: Nutrients”, OECD Agriculture Statistics (database), http://stats.oecd.org/Index.aspx?DataSetCode=AEI_NUTRIENTS (accessed in March 2017).

OECD (2017b), “Green growth indicators”, OECD Environment Statistics (database), https://doi.org/10.1787/data-00665-en (accessed in March 2017).