Estimating N input from livestock manure: current work by FAO

Organic fertilizers and soil health

Soil is a non-renewable resource crucial for food production and ecosystem stability, thus improving and maintaining soil health and reversing soil degradation is critical to sustainable agriculture.

FAO defines soil health as: “The capacity of soil to function as a living system. Healthy soils maintain a diverse community of soil organisms that help to control plant disease, insect and weed pests, form beneficial symbiotic associations with plant roots, recycle essential plant nutrients, improve soil structure with positive effects for soil water and nutrient holding capacity, and ultimately improve crop production. A healthy soil also contributes to mitigating climate change by maintaining or increasing its carbon content” (http://www.fao.org/soils-2015/en/).

Organic fertilizers and amendments, such as manure and crop residues, enhance soil health and reverse soil degradation by providing essential nutrients for plant production and increasing soil organic matter content. Soil organic matter contributes to physical, chemical and biological soil properties and processes essential for crop production and ecosystem stability, including water and nutrient retention, nutrient cycling, carbon transformations, soil biodiversity, soil structure and soil stability.

Estimating nitrogen inputs from livestock manure

While a comprehensive database at global, regional and country levels on nutrients applied to soils by synthetic fertilizers has been available through FAOSTAT for many years, detailed information on the amount of nutrients applied to soils via organic fertilizers has been lacking.

In support of FAO Strategic Objective 2 on Sustainable Food and Agriculture, the Statistics Division (ESS), the Agricultural Production and Plant Production and Protection Division (AGP), and the Animal Production and Health Division (AGA) of FAO have addressed this gap and produced estimates on nitrogen (N) inputs from livestock manure. To date, the FAOSTAT Agriculture Emission Database (http://faostat.fao.org/) contains the largest dataset on manure availability and use at the country level, and presents estimates of N in manures left on pasture, in stored manure and in manure applied to soils for the years 1961 to 2012. Preliminary analysis of the dataset indicated that global N input from livestock manure is comparable to that of synthetic fertilizers, though this varies considerably among regions. 

At present, the FAOSTAT database presents estimates of N inputs from livestock manure using IPCC Tier 1 methodology. A second set of estimates was done following a Tier 2 methodology, using country-specific information and parameters that were extracted from the FAO Global Livestock Emission Assessment Model (GLEAM) (http://www.fao.org/gleam/en/). This work represents a major step towards the availability of nationally-relevant coefficients and estimates which further address the current lack of manure data.

The two datasets can be used to provide current trends in manure management and its potential contribution to greenhouse gas emissions (GHG) which can inform future sustainable agricultural policies. The results obtained from the second analysis and comparisons of the two datasets will be reported in early 2016.

In Africa where livestock manure is the main source of N, FAO held an international workshop on statistical estimation of N inputs to soils from livestock manure (http://www.fao.org/economic/ess/ess-events/ninputs/en/). The workshop aims to raise awareness and to develop capacity in data management for livestock manure, including its availability, storage and application as fertilizer.

Future work

Additional methodologies to estimate phosphorus and potassium inputs from manure and crop residues are currently being explored and developed.

Useful Links:

FAOSTAT: http://faostat.fao.org/

GLEAM: http://www.fao.org/gleam/en/

IYS: http://www.fao.org/soils-2015/en/

Workshop: http://www.fao.org/economic/ess/ess-events/ninputs/en/