Table 1. Soil indicators, inclusion in ecosystem service assessments, indicator type and assessment methods.

Indicators included in more than 20% of soil health assessments are labelled as ‘>20%’. Those included in at least one but less than 20% of assessment methods are labelled as ‘<20%’. Those that are typically not included, but recommended to be included, are labelled as ‘proposed’. Those indicators less directly relevant for a certain ecosystem service are marked as ‘-‘, those that are more relevant with ‘+’.

		Ecosystem service
Indicator	Inclusion†	Plant production	Water quality	Human health	Climate control	Type of indicator	Methods to assess‡
N/S/P-mineralizing enzyme activity	<20%	+	+	-	+	B	Colorimetry, extraction; lab-on-a-chip; electrochemistry
N mineralization	> 20%	+	+	-	+	B	Incubation; extractions; lab-on-a-chip; electrochemistry
Microbial biomass	> 20%	+	+	-	+	B	Incubation; extractions; lab-on-a-chip; electrochemistry
Pathogens	Proposed	+	+	+	-	B	Extractions; optical analyses; lab-on-a-chip; color reactions; DNA probes; electrochemistry
Biodiversity	Proposed	+	+	+	+	B	Extractions; bioassays; metagenomics; high-throughput sequencing; Phospholipid fatty acid; lab-on-a-chip
Microbial activity	> 20%	+	+	+	+	B	Incubation; lab-on-a-chip; electrochemistry; biosensors
Parasites	Proposed	-	-	+	-	B	Extractions; bioassays; metagenomics; high-throughput sequencing; screening for pathogenicity genes; lab-on-a-chip; electrochemistry; ultrasound
Fauna	Proposed	+	+	+	+	B	Extractions; bioassays; metagenomics; high-throughput sequencing; lab-on-a-chip; electrochemistry; sound
Earthworms	< 20%	+	-	+	-	B	Extractions; lab-on-a-chip; sound
GHG emissions	Proposed	-	-	-	+	B	In-field and laboratory GHG sensors; robots; lab-on-a-chip; biosensors
Organic toxins	Proposed	+	+	+	-	C	Extractions; passive samplers; lab-on-a-chip; electrochemistry
Organic C fractions	< 20%	+	+	-	+	C	Near/mid infrared spectroscopy; density & size fractionation; oxidation
Norg fractions	< 20%	+	+	-	+	C	Protein assay; near/mid infrared spectroscopy; density & size fractionation
Organic carbon	> 20%	+	+	+	+	C	Near/mid infrared spectroscopy; combustion; ultrasound
Bio-available nutrients	> 20%	+	+	+	+	C	Near/mid infrared spectroscopy; extractions; passive samplers; colorimetry; electrochemistry
pH	> 20%	+	+	+	+	C	Near/mid infrared spectroscopy; extractions; passive samplers; colorimetry; electrochemistry
CEC	> 20%	+	+	-	-	C	Near/mid infrared spectroscopy; extractions; passive samplers; colorimetry; electrochemistry
EC	> 20%	+	+	+	-	C	Near/mid infrared spectroscopy; extractions; passive samplers; colorimetry; electrochemistry
Compound diversity	Proposed	-	+	-	+	C	Spectroscopy
Mobile nutrients	> 20%	-	+	-	+	C	Near/mid infrared spectroscopy; extractions; passive samplers; colorimetry; electrochemistry
Heavy metal toxins	> 20%	+	+	+	-	C	Near/mid infrared spectroscopy; extractions; passive samplers; bioassays; lab-on-a-chip; biosensors; electrochemistry
Pore size diversity	Proposed	-	+	-	+	P	Near/mid infrared spectroscopy; ultrasound
Aggregation	< 20%	+	+	-	+	P	Sieving; near/mid infrared spectroscopy; ultrasound; visible imaging; infiltrometry
Water storage	< 20%	+	+	+	+	P	Near/mid infrared spectroscopy; pressure plate
Penetration resistance	> 20%	+	+	-	+	P	Penetrometry; mid infrared spectroscopy
Infiltration	< 20%	+	+	+	+	P	Near/mid infrared spectroscopy; ultrasound; visible imaging; infiltrometer

B: biological; C: chemical; P: physical; N: nitrogen; OC: organic carbon; CEC: cation exchange capacity; EC: electrical conductivity; N_org : organic nitrogen

^†proportion from ref. 6

^‡broad categories are given; for some detailed methods have been proposed (see ref. 106), others are suggestion for future exploration