Yams

1. Scope and Applicability

This PCR covers managed cultivation, lifting, first farm-gate conditioning, and grading of fresh, unprocessed yam tubers (Dioscorea spp.) delivered at the farm gate. It excludes seed-yam production as the reference product, cassava, sweet potatoes, taro, yautia, processed yam products, off-farm storage, packaging, retail preparation, and cooking.

The default route ends when accepted whole tubers are weighed for transfer at farm gate. Irrigation, washing, powered handling, and input use are recorded only when they occur. Curing, extended storage, packaging, or transport beyond this hand-off requires a downstream process.

2. Product Category Identity

Field	Value
canonical_pcr_id	pcr.agriculture-forestry-and-fishery-products.products-of-agriculture-horticulture-and-market-gardening.yams
classification_refs	CPC 3.0 01540 (Yams), exact candidate mapping context; mapping relation: narrower
covered_products	Fresh whole ware-yam tubers of Dioscorea spp. at farm gate
excluded_products	Seed yams as sale product; other roots and tubers; peeled, cut, dried, frozen, cooked, fermented, chipped, or milled yams
representative_product	Fresh marketable yam tubers, whole and unprocessed
production_route	Managed field cultivation; tuber lifting; first cleaning or trimming when performed; grading and farm-gate hand-off
market_state	Fresh, unprocessed produce at farm gate

3. Reference Flow

Field	Value
What	Fresh, whole, marketable yam tubers at farm gate
How much	1,000 kg net mass
How well	Sound and saleable under the declared buyer or grade specification; soil, packaging, rejected tubers, and free wash water excluded
How long or cycle	A single-period declared yam crop cycle ending at farm-gate hand-off
reference_flow_link	accepted_yams

Field	Value
Reference amount	1000
Reference product flow	Yams 227a29cc-a11c-4357-9188-2ee8ead339bd
Reference flow property	Mass 93a60a56-a3c8-11da-a746-0800200b9a66
Reference unit group	Units of mass 93a60a57-a4c8-11da-a746-0800200c9a66
Reference unit	kg
Required qualifiers	species or species group; cultivar where known; production country and site; crop-cycle dates; rainfed or irrigated regime; whole fresh state; washing status; grade or buyer specification; farm-gate hand-off

4. Measurement and Unit Rules

rule_id	Applies to	Required property	Required unit	Rule
reference_mass	accepted farm-gate yams	Mass 93a60a56-a3c8-11da-a746-0800200b9a66	kg	Weigh net accepted tubers after grading; exclude tare, packaging, free water, loose soil, downgraded lots, and rejects.
transfer_mass	yam material transferred between nodes	Mass 93a60a56-a3c8-11da-a746-0800200b9a66	kg	Use measured wet mass at every hand-off and disclose any moisture-changing interval.
area_conversion	occupied field area	area per crop cycle	ha·crop_cycle	Match cultivated area to harvested tuber mass from the same plots and cycle before normalization.
nutrient_mass	fertilizer inputs	nutrient mass	kg nutrient	Preserve physical fertilizer products and calculate N, P2O5, and K2O equivalents separately.

5. System Boundary

Boundary Abstraction

Field	Value
declared_starting_condition	Prepared field and identifiable yam planting material are available; purchased inputs retain linked upstream datasets.
starting_condition_role	Foreground collection begins with field establishment and input application for one crop cycle.
product_classification_scope	Fresh whole ware-yam tubers at farm gate.
recursive_input_rule	Purchased or internally transferred seed yam/setts remain explicit Product-flow inputs. Same-category planting material links to a separately bounded dataset and does not recursively expand the current ware-yam process.
upstream_dataset_requirement	Link suitable upstream datasets for planting material, fertilizers, crop-protection products, fuels, electricity, irrigation supply, and waste treatment.
disclosure	Declare seed source, field area, crop dates, management regime, conditioning steps, grade definition, reject destinations, and excluded storage or packaging.

Boundary Rules

rule_id	Applies to	Rule	source_ids
boundary_managed_cultivation	yam_cultivation	Include field establishment, management inputs, irrigation when used, field energy, and direct managed-soil emissions for the crop cycle.	fao-quality-declared-yam-planting-material; iita-yam-yield-2020
boundary_harvest_handoff	yam_harvest	Treat lifting and field collection as a distinct hand-off; distinguish collected yams, damaged tubers, and uncollected loss.	fao-yam-postharvest
boundary_primary_conditioning	yam_primary_conditioning	Include loose-soil removal, trimming, conditional washing, drainage, and air drying before grading; exclude storage undertaken to extend life.	fao-yam-postharvest
boundary_grading	yam_grading	Reconcile conditioned tubers into accepted product, downgraded product, rejects, and physical loss.	fao-yam-postharvest; mass-balance-identity

6. Process Inventory Structure

Process Map

process_id	process_name	inclusion	inclusion_condition	role	quantitative_reference
yam_cultivation	Managed yam cultivation	required	Always	Establish and manage yam plants until tubers are ready for lifting	Per harvest-ready tuber output
yam_harvest	Yam lifting and field collection	required	Always	Lift tubers and transfer collected tubers to preparation	Per collected-tuber output
yam_primary_conditioning	Primary conditioning at farm gate	required	Always; individual operations conditional	Remove soil and plant matter; trim; conditionally wash and drain	Per conditioned-tuber output
yam_grading	Grading and farm-gate hand-off	required	Always	Separate accepted, downgraded, and rejected states	Per 1,000 kg accepted yams

Process: Managed yam cultivation (yam_cultivation)

Inputs

Product flows

Yam planting material (seed_yam_setts)

Record disease-screened whole seed yams or cut setts planted in contributing plots.

• Selected flow: Yam planting material

• Flow property / unit: Mass / kg

• Amount rule: measured fresh mass planted

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_material_energy_inputs

• Sources: fao-quality-declared-yam-planting-material

• Range: Provisional planting-material screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 20
  • Upper: 500
  • Unit: kg
  • Basis: per 1,000 kg accepted yam output at farm gate
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Fertilizer, urea input (yam_cultivation_agricultural_nutrient_inputs)

Include this conditional card only when Fertilizer, urea is actually used in the declared process. For every other actual product or carrier, create a separate atomic exchange with its own identity and measured amount; do not infer its use from this example.

• Selected flow: Fertilizer, urea

• Flow property / unit: Mass / kg product

• Amount rule: Measured quantity of Fertilizer, urea used by this process and period; report zero or not applicable only when the route records establish absence.

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_material_energy_inputs

Fertilizer, monoammonium phosphate input (yam_cultivation_agricultural_nutrient_inputs_monoammonium_phosphate)

Include this conditional card only when Fertilizer, monoammonium phosphate is actually used in the declared process. For every other actual product or carrier, create a separate atomic exchange with its own identity and measured amount; do not infer its use from this example.

• Selected flow: Fertilizer, monoammonium phosphate

• Flow property / unit: Mass / kg product

• Amount rule: Measured quantity of Fertilizer, monoammonium phosphate used by this process and period; report zero or not applicable only when the route records establish absence.

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_material_energy_inputs

Fertilizer, potassium chloride input (yam_cultivation_agricultural_nutrient_inputs_potassium_chloride)

Include this conditional card only when Fertilizer, potassium chloride is actually used in the declared process. For every other actual product or carrier, create a separate atomic exchange with its own identity and measured amount; do not infer its use from this example.

• Selected flow: Fertilizer, potassium chloride

• Flow property / unit: Mass / kg product

• Amount rule: Measured quantity of Fertilizer, potassium chloride used by this process and period; report zero or not applicable only when the route records establish absence.

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_material_energy_inputs

Cattle manure, as applied input (yam_cultivation_agricultural_nutrient_inputs_cattle_manure)

Include this conditional card only when Cattle manure, as applied is actually used in the declared process. For every other actual product or carrier, create a separate atomic exchange with its own identity and measured amount; do not infer its use from this example.

• Selected flow: Cattle manure, as applied

• Flow property / unit: Mass / kg product

• Amount rule: Measured quantity of Cattle manure, as applied used by this process and period; report zero or not applicable only when the route records establish absence.

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_material_energy_inputs

Agricultural limestone input (yam_cultivation_agricultural_nutrient_inputs_agricultural_limestone)

Include this conditional card only when Agricultural limestone is actually used in the declared process. For every other actual product or carrier, create a separate atomic exchange with its own identity and measured amount; do not infer its use from this example.

• Selected flow: Agricultural limestone

• Flow property / unit: Mass / kg product

• Amount rule: Measured quantity of Agricultural limestone used by this process and period; report zero or not applicable only when the route records establish absence.

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_material_energy_inputs

Irrigation water (irrigation_water)

Record water delivered to the field only for irrigated production; rainfed production records zero.

• Selected flow: Irrigation water

• Flow property / unit: Volume / m3

• Amount rule: metered or calibrated field delivery

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_water_records

• Range: Provisional irrigation screen; applies only when irrigation is active

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 0
  • Upper: 5000
  • Unit: m3
  • Basis: per 1,000 kg accepted yam output at farm gate
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Mobile machinery fuel for cultivation (cultivation_diesel)

Record diesel used by field equipment; keep every other carrier as a separate exchange.

• Selected flow: Mobile machinery fuel, diesel carrier

• Flow property / unit: Volume / L

• Amount rule: measured fuel issued to cultivation

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_material_energy_inputs

• Range: Provisional cultivation-diesel screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 0
  • Upper: 100
  • Unit: L
  • Basis: per 1,000 kg accepted yam output at farm gate
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Waste flows

No waste input is prescribed. Imported manure or recovered nutrient material is a Product-flow input with declared origin.

Elementary flows

Occupied field area (field_area_occupation)

Match field area and crop-cycle dates to the harvest from the same plots.

• Selected flow: Agricultural land occupation

• Flow property / unit: Area-time / ha·crop_cycle

• Amount rule: Raw occupation = actual managed area multiplied by the dated attributable occupation duration in years, partitioned across non-overlapping phases and all co-users once. Convert ha to m2 by 10,000 only if the selected area-time identity requires m2*year. Area divided by product mass alone is not area-time. Attribute the area-time numerator using the original allocation rules, then normalize once to matched accepted final-reference mass, including actual wet-to-dry stage-throughput linkage where relevant; do not divide an already final intensity again.

• Value mode: Calculated value (calculated_value)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg harvest-ready yam tubers.

• Normalization basis: per declared reference flow

• Basis kind: Process output (process_output)

• Evidence kind: Calculated from collection (calculated_from_collection)

• Collection protocol: cp_field_area_and_yield

• Sources: iita-yam-yield-2020

• Range: Nigerian example derived from 13.1–23 t/ha reported yields

  • Range role: Typical range (typical_range)
  • Lower: 0.0435
  • Upper: 0.0763
  • Unit: ha·crop_cycle
  • Basis: per 1,000 kg harvest-ready yam tubers; regional example only
  • Basis kind: Process output (process_output)
  • Evidence kind: External source (external_source)
  • Sources: iita-yam-yield-2020

Outputs

Product flows

Harvest-ready yam crop (harvest_ready_yams)

This intermediate tuber state is handed to yam_harvest and is not the reference product.

• Selected flow: Harvest-ready yam tubers

• Flow property / unit: Mass / kg

• Amount rule: measured or plot-estimated tuber mass immediately before lifting

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_crop_mass_transfers

• Range: Provisional harvest-ready mass reconciliation screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 1000
  • Upper: 2000
  • Unit: kg
  • Basis: per 1,000 kg accepted yam output at farm gate
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Waste flows

Plant residues remaining in the field are recorded in the field balance and emissions model, not as waste outputs.

Elementary flows

Direct nitrous oxide from managed soil (direct_soil_n2o)

Calculate direct N2O separately from indirect pathways using the selected IPCC tier or a better regional method.

• Selected flow: Nitrous oxide, to air

• Flow property / unit: Mass / kg N2O

• Amount rule: nitrogen input multiplied by the direct N2O-N factor and by 44/28

• Value mode: Calculated value (calculated_value)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Method formula (method_formula)

• Sources: ipcc-2006-managed-soils-n2o

• Range: IPCC Tier 1 factor uncertainty screen before molecular conversion

  • Range role: Uncertainty range (uncertainty_range)
  • Lower: 0.003
  • Upper: 0.03
  • Unit: kg N2O-N/kg N input
  • Basis: per kg N input applied to managed soil
  • Basis kind: Nitrogen input (n_input)
  • Evidence kind: Method formula (method_formula)
  • Sources: ipcc-2006-managed-soils-n2o

Process: Yam lifting and field collection (yam_harvest)

Inputs

Product flows

Harvest-ready yam crop received (harvest_ready_yams_received)

Receive the cultivation output on the same lot and crop-cycle basis.

• Selected flow: Harvest-ready yam tubers

• Flow property / unit: Mass / kg

• Amount rule: equal to transferred harvest_ready_yams

• Value mode: Calculated value (calculated_value)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Method formula (method_formula)

• Sources: mass-balance-identity

• Range: Transfer-mass reconciliation screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 1000
  • Upper: 2000
  • Unit: kg
  • Basis: per 1,000 kg accepted yam output at farm gate
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Mobile harvest machinery fuel (harvest_diesel)

Record diesel used by lifting and collection equipment; manual harvest records zero.

• Selected flow: Mobile harvest machinery fuel, diesel carrier

• Flow property / unit: Volume / L

• Amount rule: measured fuel issued to harvest

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg collected yam output.

• Normalization basis: per declared reference flow

• Basis kind: Process output (process_output)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_material_energy_inputs

• Range: Provisional harvest-diesel screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 0
  • Upper: 80
  • Unit: L
  • Basis: per 1,000 kg collected yam output
  • Basis kind: Process output (process_output)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Waste flows

No waste input is prescribed.

Elementary flows

No separate elementary input is prescribed.

Outputs

Product flows

Collected yam tubers (collected_yams)

Record all tubers physically lifted and delivered to conditioning, including tubers later rejected.

• Selected flow: Collected fresh yam tubers

• Flow property / unit: Mass / kg

• Amount rule: measured transfer mass

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_crop_mass_transfers

• Sources: fao-yam-postharvest

• Range: Provisional collected-tuber reconciliation screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 1000
  • Upper: 1800
  • Unit: kg
  • Basis: per 1,000 kg accepted yam output at farm gate
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Waste flows

Tubers damaged or lost during lifting (harvest_damaged_yams)

Record unusable tubers damaged during lifting or separately quantified as uncollected loss; saleable downgraded tubers are not waste.

• Selected flow: Damaged yam tubers

• Flow property / unit: Mass / kg

• Amount rule: measured damaged or unrecovered tuber mass

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg collected yam output.

• Normalization basis: per declared reference flow

• Basis kind: Process output (process_output)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_reject_and_loss_records

• Sources: fao-yam-postharvest

• Range: Provisional harvest-loss screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 0
  • Upper: 300
  • Unit: kg
  • Basis: per 1,000 kg collected yam output
  • Basis kind: Process output (process_output)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Elementary flows

Equipment exhaust remains in linked fuel-combustion datasets unless directly measured.

Process: Primary conditioning at farm gate (yam_primary_conditioning)

Inputs

Product flows

Collected yam tubers received (collected_yams_received)

Receive the complete collected-tuber state before cleaning or trimming.

• Selected flow: Collected fresh yam tubers

• Flow property / unit: Mass / kg

• Amount rule: equal to transferred collected_yams

• Value mode: Calculated value (calculated_value)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Method formula (method_formula)

• Sources: mass-balance-identity

• Range: Transfer-mass reconciliation screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 1000
  • Upper: 1800
  • Unit: kg
  • Basis: per 1,000 kg accepted yam output at farm gate
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Conditioning wash water (conditioning_wash_water)

Record water only when washing occurs because of contamination or buyer requirements; dry cleaning records zero.

• Selected flow: Process water

• Flow property / unit: Mass / kg

• Amount rule: measured water supplied to yam washing

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg conditioned yam output.

• Normalization basis: per declared reference flow

• Basis kind: Process output (process_output)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_water_records

• Sources: fao-yam-postharvest

• Range: Provisional wash-water screen; applies only when washing is active

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 0
  • Upper: 2000
  • Unit: kg
  • Basis: per 1,000 kg conditioned yam output
  • Basis kind: Process output (process_output)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Conditioning electricity (conditioning_electricity)

Record electricity used by washers, conveyors, or fans; unpowered conditioning records zero.

• Selected flow: Electricity

• Flow property / unit: Energy / kWh

• Amount rule: metered electricity assigned to conditioning

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg conditioned yam output.

• Normalization basis: per declared reference flow

• Basis kind: Process output (process_output)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_material_energy_inputs

• Range: Provisional conditioning-electricity screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 0
  • Upper: 50
  • Unit: kWh
  • Basis: per 1,000 kg conditioned yam output
  • Basis kind: Process output (process_output)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Waste flows

No waste input is prescribed.

Elementary flows

No separate elementary input is prescribed.

Outputs

Product flows

Conditioned yam tubers (conditioned_yams)

Record intact tubers after loose-soil removal, trimming, and any washing and drainage, ready for grading.

• Selected flow: Conditioned fresh yam tubers

• Flow property / unit: Mass / kg

• Amount rule: measured mass transferred to grading after free water drains

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_crop_mass_transfers

• Sources: fao-yam-postharvest

• Range: Provisional conditioned-tuber reconciliation screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 1000
  • Upper: 1600
  • Unit: kg
  • Basis: per 1,000 kg accepted yam output at farm gate
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Waste flows

Removed soil and plant matter (conditioning_solid_residue)

Record solids removed during conditioning. Split soil and plant matter in a concrete dataset if destinations differ.

• Selected flow: Conditioning solid residue

• Flow property / unit: Mass / kg

• Amount rule: measured residue mass leaving conditioning

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg conditioned yam output.

• Normalization basis: per declared reference flow

• Basis kind: Process output (process_output)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_reject_and_loss_records

• Range: Provisional solid-residue screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 0
  • Upper: 200
  • Unit: kg
  • Basis: per 1,000 kg conditioned yam output
  • Basis kind: Process output (process_output)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Wash wastewater (conditioning_wastewater)

Record wastewater only when washing is active and identify discharge, reuse, or treatment.

• Selected flow: Wastewater from produce washing

• Flow property / unit: Mass / kg

• Amount rule: measured or water-balanced discharge

• Value mode: Calculated value (calculated_value)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg conditioned yam output.

• Normalization basis: per declared reference flow

• Basis kind: Process output (process_output)

• Evidence kind: Calculated from collection (calculated_from_collection)

• Collection protocol: cp_water_records

• Range: Provisional wastewater screen; applies only when washing is active

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 0
  • Upper: 2000
  • Unit: kg
  • Basis: per 1,000 kg conditioned yam output
  • Basis kind: Process output (process_output)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Elementary flows

Direct discharge may replace the wastewater row with substance-specific elementary flows when the foreground boundary discharges to the environment.

Process: Grading and farm-gate hand-off (yam_grading)

Inputs

Product flows

Conditioned yam tubers received (conditioned_yams_received)

Receive the complete conditioned state before grading.

• Selected flow: Conditioned fresh yam tubers

• Flow property / unit: Mass / kg

• Amount rule: equal to transferred conditioned_yams

• Value mode: Calculated value (calculated_value)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Method formula (method_formula)

• Sources: mass-balance-identity

• Range: Transfer-mass reconciliation screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 1000
  • Upper: 1600
  • Unit: kg
  • Basis: per 1,000 kg accepted yam output at farm gate
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Waste flows

No waste input is prescribed.

Elementary flows

No elementary input is prescribed.

Outputs

Product flows

Accepted farm-gate yams as intended output (accepted_yams)

This is the reference product after applying the declared grade or buyer specification.

• Selected flow: Yams 227a29cc-a11c-4357-9188-2ee8ead339bd

• Flow property / unit: Mass 93a60a56-a3c8-11da-a746-0800200b9a66 / kg Raw output measurement and reconciliation: exactly 1,000 kg net accepted tubers

• Amount rule: 1000 kg

• Value mode: Fixed value (fixed_value)

• Specificity: Generic (generic) Raw activity or stage basis: per 1,000 kg reference product.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Method formula (method_formula)

• Sources: mass-balance-identity

• Range: Fixed reference-flow identity

  • Range role: Allowed range (allowed_range)
  • Lower: 1000
  • Upper: 1000
  • Unit: kg
  • Basis: per 1,000 kg reference product
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Method formula (method_formula)
  • Sources: mass-balance-identity

Downgraded but saleable yams as intended output (downgraded_yams)

Record sound lower-grade tubers sold to a distinct destination as a separate intended Product flow.

• Selected flow: Downgraded fresh yam tubers

• Flow property / unit: Mass / kg

• Amount rule: measured lower-grade saleable mass

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_reject_and_loss_records

• Sources: fao-yam-postharvest

• Range: Provisional downgraded-output screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 0
  • Upper: 300
  • Unit: kg
  • Basis: per 1,000 kg accepted yam output at farm gate
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Waste flows

Rejected yam tubers (grading_rejects)

Record unsaleable cut, crushed, punctured, diseased, or rotten tubers by destination.

• Selected flow: Rejected yam tubers

• Flow property / unit: Mass / kg

• Amount rule: measured rejected mass

• Value mode: Foreground record (foreground_record)

• Specificity: Site-specific (site_specific) Raw activity or stage basis: per 1,000 kg accepted yam output at farm gate.

• Normalization basis: per declared reference flow

• Basis kind: Reference flow (reference_flow)

• Evidence kind: Collected record (collected_record)

• Collection protocol: cp_reject_and_loss_records

• Sources: fao-yam-postharvest

• Range: Provisional grading-reject screen

  • Range role: QA guardrail (qa_guardrail)
  • Lower: 0
  • Upper: 300
  • Unit: kg
  • Basis: per 1,000 kg accepted yam output at farm gate
  • Basis kind: Reference flow (reference_flow)
  • Evidence kind: Reasoned estimate (reasoned_estimate)

Elementary flows

No direct elementary output is prescribed.

7. Allocation and Co-product Handling

rule_id	Applies to	Rule	source_ids
allocation_subdivide	separately measured fields, operations, grades, or destinations	Prefer subdivision and direct assignment before allocation.
allocation_single_output	residues and rejects without an intended product function	Assign burdens to accepted yams and retain residues and rejects as Waste flows; do not credit avoided disposal without an explicit scenario.
allocation_saleable_downgrade	downgraded yams sold as intended product	Declare all intended outputs and use a justified physical or economic allocation only when subdivision is impracticable; report basis and sensitivity.	mass-balance-identity
allocation_seed_retention	internally retained planting material	Record an internal Product-flow transfer and burden decision; prevent the same tuber mass and burden from being both current output and free next-cycle input.

rule_id	Applies to	Rule	source_ids
allocation_residual_precedence	remaining common burden with no specified primary branch	Resolve any study-specific joint-product instruction in this PCR that has no specified primary branch using this precedence; retain an already explicitly prescribed category-specific primary method. First directly assign separable output-specific activities. For the remaining common burden B, use a physical driver d_i only when measured operation or biological-service records demonstrate the causal consumption represented by that driver. A product being weighable, valuable or lower grade alone is insufficient; do not switch arbitrarily between area, time, mass and revenue. For comparable grades receiving the same common handling, measured processed mass is applicable only with the same service demand, state and moisture basis demonstrated. Share a_i=d_i/sum(d_j); B_i=Ba_i. If no defensible causal physical driver exists for that common operation, use gate- and period-matched economic shares a_i=(q_ip_i)/sum(q_j*p_j), with the complete independently intended output set, compatible quantity/price units, currency, representative prices and values before output-specific downstream processing. Missing price or denominator evidence makes the allocated result incomplete, not a zero-priced product or a single-output system. Report shares summing to one and sensitivity to a material alternative; an alternative is not an interchangeable primary result. Waste, retained residues and internal transfers receive no co-product share, while their attributable production/handling burdens remain with the producing saleable route. Retain unallocated physical quantities and mass balances separately. This branch gives no automatic substitution credit; any separately scoped substitution analysis retains the gross inventory and its actual displaced-function evidence.	ghg-protocol-product-standard-2011

8. Foreground Data Collection, Calculation, and Quality Rules

Retain raw site, lot, cycle and stage quantities and denominators in each collection protocol. Reconcile stocks, losses, moisture and co-product attribution first, then normalize: normalized exchange = attributable raw exchange × declared reference quantity / accepted hand-off product quantity on the same boundary and measurement basis. Apply perennial-establishment and shared-operation attribution before this normalization. Never set an internal-transfer quantity equal to the final reference quantity. Per declared reference flow means the amount, unit and product state in section 3; the data package must declare its actual route and gate.

Data Collection Protocols

protocol_id	process_id	flow_role	record_type	raw_fields	collection_method	unit	frequency	temporal_coverage	site_scope	aggregation_rule	quality_evidence
cp_material_energy_inputs	cultivation, harvest, conditioning	planting material, fertilizer products, diesel, electricity	invoice, issue log, meter, product analysis	date, identity, quantity, unit, analysis, process, plot or lot	reconcile purchases and issues; preserve physical products before conversion; Raw aggregation and attribution: sum by product and process, then normalize	native unit and kg nutrient	each event	complete crop cycle	contributing farm and plots	per declared reference flow	invoices, labels, meter and issue logs
cp_water_records	cultivation and conditioning	irrigation water, wash water, wastewater	meter, pump log, vessel count, balance	source, date, volume or mass, destination	meter preferred; otherwise calibrated pump-time or vessel count; Raw aggregation and attribution: sum by source and destination	m3 or kg	each event	crop cycle and conditioning	field and conditioning area	per declared reference flow	calibration and balance check
cp_field_area_and_yield	cultivation	area occupation and yield	field map, plot register, harvest ticket	plot, area, dates, harvest-ready mass	match surveyed area to plot harvest; Raw aggregation and attribution: include only plots entering package	ha, date, kg	each plot and harvest	complete crop cycle	every contributing plot	per declared reference flow	map, register, calibrated scale
cp_crop_mass_transfers	all nodes	intermediate and accepted yam masses	scale and transfer log	time, origin, destination, gross, tare, net, lot, state	calibrated weighing at each hand-off; Raw aggregation and attribution: sum by state and reconcile	kg	each lot	harvest through hand-off	all contributing lots	per declared reference flow	calibration and traceability
cp_reject_and_loss_records	harvest, conditioning, grading	damaged tubers, residues, downgraded yams, rejects	sorted-bin weights and disposition logs	role, reason, grade, mass, destination, lot	weigh every separated state; Raw aggregation and attribution: sum separately by identity and destination	kg	each lot	harvest through grading	all contributing lots	per declared reference flow	scale, inspection, receiving evidence

Calculation Rules

rule_id	Applies to	Formula or rule	Inputs	Output	source_ids
calc_reference_normalization	every inventory row	attributable amount × 1,000 / net accepted-yam mass	attributable amount; accepted mass	amount per 1,000 kg reference product	mass-balance-identity
calc_nutrient_equivalent	fertilizer inputs	physical fertilizer mass × declared nutrient fraction; keep N, P2O5, and K2O separate	product mass; analysis	kg nutrient
calc_land_intensity	field area	contributing area × 1,000 / harvest-ready tuber mass from the same plots	ha; kg tubers	ha·crop_cycle per 1,000 kg tubers	iita-yam-yield-2020
calc_direct_n2o	direct soil N2O	apply selected direct N2O-N factor, then multiply by 44/28	kg N input; factor	kg N2O	ipcc-2006-managed-soils-n2o
calc_node_mass_balance	harvest, conditioning, grading	input yam mass = yam Product outputs + yam Waste outputs + stock change + documented loss	transfer, reject, and stock records	residual and completeness flag	mass-balance-identity
chemical_species_mass_accounting	elementary_nutrient_emissions	Final elementary exchanges use the mass of the identified substance and one actual receiving compartment. Keep nutrient/activity ledgers separate: species-specific N2O-N × 44/28 gives N2O, NH3-N × 17/14 gives NH3, nitrate-N × 62/14 gives nitrate, and phosphate-P × 95/31 gives phosphate. If the selected flow is elemental phosphorus instead, report kg P and convert phosphate mass by 31/95 only when that species basis is evidenced. Apply a conversion exactly once only when the method output is on the elemental basis; measured compound mass is not reconverted. Total nutrient losses cannot be assigned to a single species without a supported split, and residual/retained soil nutrient is not an emission. Keep direct/indirect pathway ledgers and avoid repeating a pathway already included in the chosen method or upstream inventory. Factor uncertainty ranges screen factors on their stated basis, not final compound amounts or admissible site emissions. Normalize the attributable compound mass once using the accepted reference quantity and the matched measured output. Unknown activity, identity or compartment remains an evidence gap and blocks a completeness claim.	cp_material_energy_inputs; species-specific activity ledger, method pathway and factor basis, matched accepted output	Identity-specific exchanges and reconciled activity records

Data Quality Requirements

requirement_id	Applies to	Requirement	Evidence
dq_identity	product and intermediate states	Preserve species or group, cultivar where known, lot, grade, and state; never merge other tuber crops into yam output.	lot records and buyer specification
dq_temporal	foreground records	Use one reporting period covering one complete crop cycle and every included harvest, conditioning, and grading event; no replacement or termination event occurs.	dated field and transfer records
dq_mass_balance	transfer nodes	Reconcile accepted, downgraded, rejected, residue, wastewater, loss, and stock-change states without double counting.	node reconciliation
dq_conditional_routes	irrigation, washing, powered operations	Record zero only after confirming the operation did not occur.	operation log and meter or invoice
dq_range_use	amount ranges	Use ranges as screens; actual foreground records determine reported values, and regional examples are not universal limits.	range exception review

9. Validation Rules

rule_id	Applies to	Rule	source_ids
validate_reference_identity	reference flow	The reference output shall be exactly 1,000 kg net accepted Yams flow with every required qualifier declared.
validate_node_linkage	process graph	Cultivation, harvest, conditioning, and grading transfer rows shall match by lot and mass basis.	mass-balance-identity
validate_grade_completeness	grading	Every incoming tuber mass shall be accepted, downgraded, rejected, stock change, or documented loss with a destination.	fao-yam-postharvest; mass-balance-identity
validate_conditional_inputs	irrigation, washing, electricity, diesel	Zero is conforming only when records show the relevant operation or carrier was absent.
validate_range_denominators	all ranges	Each bound shall use its stated field, process-output, nitrogen-input, or reference-flow denominator; conditional ranges apply only when active.
validate_no_extended_boundary	dataset boundary	Curing, extended storage, packaging, and post-gate transport shall be excluded or represented as explicit downstream processes.	fao-yam-postharvest

10. Published Dataset Profile

Field	Value
dataset_role	Foreground farm production package suitable for reviewed secondary_dataset or background_dataset publication
downstream_use	Attributional process and lifecycle-model construction for fresh whole yams at farm gate
allowed_use	The declared geography, crop cycle, management regime, conditioning route, and grade
excluded_use	Seed-yam production; other tuber crops; processed, packaged, or stored yam chains; retail and consumption
required_metadata	geography; site and plot coverage; crop dates; species; cultivar where known; seed source; irrigation status; input products; harvest method; washing status; grade; destinations; allocation
required_quality_disclosure	record coverage; measured versus estimated shares; calibration; range exceptions; mass-balance residuals; unresolved UUIDs; source representativeness
update_trigger	Changed boundary, flow identity, market state, methodology source, process topology, allocation decision, or evidence invalidating a range or rule

11. Data Sources

Source id	Type	Reference	Used for
fao-yam-postharvest	official_guidance	FAO, Yams: Post-harvest Operations, https://www.fao.org/fileadmin/user_upload/inpho/docs/Post_Harvest_Compendium_-_Yams.pdf; FAO crop profile, https://www.fao.org/4/x5014e/X5014e0f.htm	maturity, careful lifting, conditional washing and drying, damage removal, grading, route decomposition
fao-quality-declared-yam-planting-material	official_guidance	FAO, Quality declared planting material — protocols and standards for vegetatively propagated crops, https://www.fao.org/4/i1195e/i1195e00.pdf	seed-yam and sett identity and quality context
iita-yam-yield-2020	extension_guidance	IITA, IITA BIP team achieves 23 tons per hectare yield for yam in Nigeria (2020), https://iita.org/news-item/iita-bip-team-achieves-23-tons-per-hectare-yield-for-yam-in-nigeria/	Nigerian regional yield example, crop duration, cultivation operations
ipcc-2006-managed-soils-n2o	method_factor	IPCC, 2006 Guidelines for National Greenhouse Gas Inventories, Volume 4, Chapter 11	direct managed-soil N2O method and factor uncertainty
mass-balance-identity	method_factor	Conservation of mass applied at each declared process node	transfers, reference identity, node reconciliation
ghg-protocol-product-standard-2011	standard	WRI/WBCSD, Product Life Cycle Accounting and Reporting Standard (2011), Chapter 9, https://ghgprotocol.org/sites/default/files/standards/Product-Life-Cycle-Accounting-Reporting-Standard_041613.pdf	General allocation hierarchy and comparable-gate economic basis. Applicability conditions and the explicit residual branch are this PCR's method convention; no product-specific causal coefficient, price or output quantity is prescribed by this source.