December 4, 2022

How much fertilizer is the right amount to ensure crop production can meet local and global food security needs while limiting environmental impact?

Answering this question remains a major challenge, but one that can be better explored with new, robust data available in FAOSTAT, according to the Food and Agriculture Organization of the United Nations (FAO).

FAOSTAT is a joint effort of FAO and the International Fertilizer Association (IFA) in collaboration with top scientists and experts from the University of Maryland Center for Environmental Sciences, the Swedish University of Agricultural Sciences, CEIGRAM-Universidad Politécnica de Madrid and Wageningen University & Research, the University of Nebraska and the African Plant Nutrition Institute.

According to the FAO, the partnership has led to the development of novel data on arable land nutrient balances that allow the environmental impact of fertilizer inputs to be assessed in relation to the amounts needed to support sustainable crop production.

The Cropland Nutrient Budget is a new data domain from FAOSTAT, the world’s largest portal for food and agriculture statistics, which serves as a global public good, enabling Member States and all stakeholders in the world’s agri-food systems to access harmonized data on production, trade and view consumption. and now the streams of nitrogen, phosphorus and phosphate, the three main plant macronutrients needed for plants to thrive.

FAO takes the basic crop and animal production data provided by countries as part of their international reporting obligations and integrates them with methods and models provided by the scientific partners in this project to track over time a common set of reference data countries to generate -Series 1961-2020; which is updated annually. FAOSTAT data, explained FAO statistician Francesco Tubiello, represents a robust data tool that builds on basic national statistics to help unravel difficult sustainability issues such as nutrient fluxes at national, regional and global levels.

Nutrient balances of farmland

Cropland nutrient balance is an important indicator of nutrient fluxes, which can indicate under- or over-utilization of agricultural inputs in the form of the three main nutrients for plant growth, be it in mineral, chemical or organic form.

The budget approach counts the amounts of mineral and chemical fertilizers and manure applied to farmland soils along with biological nitrogen fixation – legumes are large nitrogen fixers – and atmospheric deposition, and subtracts nutrient runoff associated with crops.

In general, excessive soil nutrient loads (a household surplus) pose environmental risks such as leaching into water sources and volatilization in the form of greenhouse gas emissions. On the other hand, insufficient nutrient loads (a deficit in the budget) are often associated with lower crop yields and a lack of soil nutrients.

Budgets can also be converted into efficiency rates, which are a measure of how well plants use available nutrients (ratio between nutrient removal from plants and total nutrient input). However, the data shows that the results reflect underlying issues that need to be addressed with care. Seemingly impressive use efficiency rates, for example, may actually indicate soil nutrient depletion, an unsustainable situation where inadequate inputs applied relative to crop production levels otherwise required ultimately result in future production prospects being impoverished

Some takeaways

Globally, 85 million tonnes of nitrogen (N), 7 million tonnes of phosphorus (P) and 12 million tonnes of potassium (K) were distributed over cropland in 2020, a four-fold increase since 1961, with an increasing proportion provided by artificial fertilizers. N, P and K were distributed at average rates of 54, 4 and 7 kg per hectare, respectively. Compared to the 1960s, these application rates represent a 3.4-fold increase for N, stability for P, and a 36 percent decrease for K. Efficiency rates for all three have increased over the past few decades, averaging between 50 and 50% 62 percent over the entire period.

Nitrogen use efficiency values ​​in Africa clearly show that agricultural practices generally deplete natural soil nutrients for crop production.

China and India have some of the highest N budget surpluses in the world, with efficiency rates below the world average of 50 percent. Far smaller surpluses were found in Brazil and the United States of America, partly due to large-scale soybean cultivation, which required less input in these countries due to the natural biological supply of nitrogen from this crop.

Some countries have surpluses of one key nutrient and significant deficits of another, including large agricultural countries such as Argentina, Nigeria and Ukraine. That, explains Nathan Wanner, an FAO statistician who helped build the new database, could suggest strategies to refocus based on crop selection and fertilizer priorities.

Goals of sustainable agriculture

According to the FAO, a better understanding of cropland nutrient balances can help farmers and policymakers better identify and evaluate practices for more sustainable agriculture.

The FAO is the guardian of the Sustainable Development Goal Indicator 2.4.1, which monitors the proportion of land under productive and sustainable agriculture.

The new Cropland Nutrient Budget data offers a way to go beyond rudimentary criteria based on fertilizer application rates as a simplified benchmark. While policymakers disagree on the trade-offs between fertilizer use, food production requirements and environmental protection, the new data provide a more balanced and complete way to understand the interaction of each component in determining nutrient fluxes, and thus useful strategies better to identify.