The mission of NuGAPS is to better quantify the performance of crop nutrients supplied as fertilizers. NuGAPs collects data estimates on: (1) Nutrient use through the application of fertilizers, and (2) GAPs in fertilizer use and crop yield that result from producing at less than realistically attainable yields. This database presents regional estimates of fertilizer use by crop for selected countries where the International Plant Nutrition Institute (IPNI) conducts its programs. Information on IPNI programs are available at www.ipni.net.
NuGAPS collects fertilizer use by crop data at two geographic scales. First, country-level data provides estimates that integrate our knowledge of fertilizer use at this commonly evaluated scale, and allows for readily accessible cross comparisons of nutrient management between countries. Secondly, estimates are provided for a select number of benchmark cropping domains within a country in order to document nutrient management at a narrower scale and begin to differentiate trends in nutrient use from the national context.
Fertilizer use by crop estimates are provided within NuGAPS at two yield levels: 1) current yields based on published statistical sources, and 2) realistically attainable yields based on field research and/or on-farm trials, conducted by IPNI and associates, or other avialiable sources.
The collection of these base data allows for the subsequent calculation and linkage of yield gap and fertilizer use gap information. One of the primary goals of NuGAPS is to derive, assess, and monitor a set of recognized indicators of nutrient performance in crop production, namely partial nutrient balance (removal-to-fertilizer use ratio) and partial factor productivity. These two indicators can be combined to help in the assessment of the efficiency and effectiveness of applied nutrients. Information from NuGAPS can be combined with local information on soil fertility trends, and local knowledge on best management practice adoption. For background, we recommend the IPNI publication Nutrient Performance Indicators: The importance of farm scale assessments, linked to soil fertility, productivity, environmental impact and the adoption of grower best management practices. Available to download at http://www.ipni.net/issuereview.
Attainable area fertilized (%) – estimated crop area reflecting reasonable expectations for adoption of fertilization practices aimed at the attainable yield goal.
Attainable fertilizer rates (kg/ha) – science based application rates prescribed to remove nutrient limitations with the aim of producing the attainable yield goal.
Attainable yield (kg/ha) – harvest yield achieved in farmers' fields with good agronomy including ample nutrient supply. It is limited by a region's yield potential and other factors not easily overcome by management (e.g., water availability, soil characteristics, etc.).
Crop Domain (Benchmark) – a distinct crop or component of a crop rotation nominated for monitoring within a country.
Current area fertilized (%) – estimated crop area currently receiving a fertilizer nutrient.
Current fertilizer rates (kg/ha) – application rates that correspond to common farm practice responsible for the estimated current yield.
Current yield (kg/ha) – harvested yield achieved with common farm practice.
Exploitable Yield Gap (kg/ha) – calculated as attainable yield - current yield, it is the portion of yield that can be realistically gained given the elimination of nutrient limitations and continued adoption of good agronomic management.
Partial Factor Productivity (kg yield/kg fertilizer nutrient applied) – crop yield per unit of fertilizer nutrient applied. It answers the question “How productive is this cropping system relative to its fertilizer nutrient input?” It will, by definition, decline with increased fertilizer inputs.
Partial Nutrient Balance (Removal-to-Fertilizer Use ratio) (kg nutrient removed/kg fertilizer applied) – It answers the question “How much nutrient is being taken out of the system relative to the amount of fertilizer being supplied?”
Potential yield (kg/ha) – represents the non-water limited, upper yield boundary for current crop genetic material.