Global data on crop nutrient concentration and harvest indices

Estimates of crop nutrient removal (as crop products and crop residues)
are an important component of crop nutrient balances. Crop nutrient
removal can be estimated through multiplication of the quantity of crop
products or crop residues (removed) by the nutrient concentration of those
crop products and crop residue components respectively. Data for
quantities of crop products removed at a country level are available
through FAOSTAT (https://www.fao.org/faostat/en/), but equivalent data for
quantities of crop residues are not available at a global level. However,
quantities of crop residues can be estimated if the relationship between
quantity of crop residues and crop products is known. Harvest index (HI)
provides one such indication of the relationship between quantity of crop
products and crop residues. HI is the proportion of above-ground biomass
as crop products and can be used to estimate quantity of crop residues
based on quantity of crop products. Previously, meta-analyses or surveys
have been performed to estimate nutrient concentrations of crop products
and crop residues and harvest indices (collectively known as crop
coefficients). The challenges for using these coefficients in global
nutrient balances include the representativeness of world regions or
countries. Moreover, it may be unclear which countries or crop types are
actually represented in the analyses of data. In addition, units used
among studies differ which makes comparisons challenging. To overcome
these challenges, data from meta-analyses and surveys were collated in one
dataset with standardised units and referrals to the original region and
crop names used by the sources of data. Original region and crop names
were converted into internationally recognised names, and crop
coefficients were summarised into two Tiers of data, representing the
world (Tier 1, with single coefficient values for the world) and specific
regions or countries of the world (Tier 2, with single coefficient values
for each country). This dataset will aid both global and regional analyses
for crop nutrient balances.

作物养分移除量（作物产品及残茬中的养分移除）估算是作物养分平衡的重要组成部分。作物养分移除量可通过将移除的作物产品或残茬的数量分别乘以其对应养分浓度来估算。国家层面的作物产品移除量数据可通过FAOSTAT（https://www.fao.org/faostat/en/）获取，但全球层面的作物残茬移除量等效数据尚未公开。不过，若已知作物残茬与产品数量间的关系，则可估算残茬数量。收获指数（Harvest Index, HI）正是反映作物产品与残茬数量关系的指标之一。HI是地上生物量中作物产品所占的比例，可基于作物产品数量估算残茬数量。此前，已有荟萃分析或调查研究用于估算作物产品、残茬的养分浓度及收获指数（统称为作物系数）。在全球养分平衡中使用这些系数面临的挑战包括世界区域或国家的代表性问题。此外，数据分析中实际涵盖哪些国家或作物类型可能并不明确。另外，各研究使用的单位不一致，导致比较困难。为克服这些挑战，本数据集整合了来自荟萃分析和调查的数据，统一了单位，并标注了数据源所用的原始区域及作物名称。原始区域及作物名称已转换为国际通用名称，作物系数被归纳为两级数据：代表全球的一级数据（Tier 1，全球统一系数值）和代表特定区域或国家的二级数据（Tier 2，各国独立系数值）。本数据集将为全球及区域层面的作物养分平衡分析提供支持。