Table 2.
Description of explanatory variables
| Category and variable | Description and levela | Unit |
|---|---|---|
| Farm management factors | ||
| Human | ||
| workers | Farm uses temporary workers (yes/no) | |
| workers_# | No. of temporary workers used on the farm (con) | No. |
| workers_time | Time since the last workers' visit during CGS (con) | Days |
| foodsafety_training | Food safety training provided to the staff/temporary workers on the farm (yes/no) | |
| toilets | Portable toilets used in the field (yes/no) | |
| toilet_training | Training to use portable toilets to staff/temporary workers (yes/no) | |
| toilet_distances | Portable toilet distances from the work area on the field (con) | Meters |
| washing_stations | Hand-washing stations used in the field (yes/no) | |
| Farm and field conditions | ||
| farm_size | Farm size (con) | Acres |
| organic | Organic farming practices currently applied on the farm (yes/no) | |
| organic_duration | Duration of application of organic farming practices on the farm (con) | Yr |
| organic_certified | Organic farming certified by the National Organic Program (yes/no) | |
| field_grazed | Farming on field previously used for grazing (yes/no) | |
| before_fallow | Field condition before planting of the spinach during CGS, fallow (yes/no) | |
| before_rotavated | Field condition before planting of the spinach during CGS, rotavated (yes/no) | |
| before_tilled | Field condition before planting of the spinach during CGS, tilled (yes/no) | |
| before_cover_crop | Field condition before planting of the spinach during CGS, cover crop (yes/no) | |
| before_hay | Field condition before planting of the spinach during CGS, hay (yes/no) | |
| before_riped | Field condition before planting of the spinach during CGS, riped (yes/no) | |
| tillage | Tilling, rotavating, or aerating soil for CGS (yes/no) | |
| tillage_time | Time since the last tilling, rotavating, or aerating of soil for CGS (con) | Days |
| Pesticide | ||
| pesticide_application | Pesticide application (yes/no) | |
| pesticide_time | Time since the last pesticide application during CGS (con) | Days |
| pesticide_herbicide | Type of pesticide applied to the field for CGS, herbicide (yes/no) | |
| pesticide_fungicide | Type of pesticide applied to the field for CGS, fungicide (yes/no) | |
| pesticide_insecticide | Type of pesticide applied to the field for CGS, insecticide (yes/no) | |
| pesticide_method_low | Method for applying pesticide for CGS, low-vol spray (yes/no) | |
| pesticide_method_high | Method for applying pesticide for CGS, high-vol spray (yes/no) | |
| pesticide_method_foliar | Method for applying pesticide for CGS, foliar (yes/no) | |
| pesticide_method_soil | Method for applying pesticide for CGS, soil (yes/no) | |
| Chemical fertilizer | ||
| chemical_application | Chemical fertilizer spread onto the field for CGS (yes/no) | |
| chemical_time | Time since the last chemical fertilizer spreading during CGS (con) | Days |
| chemical_method_fertigation | Method for spreading chemical fertilizer onto the field for CGS, fertigation (yes/no) | |
| chemical_method_spray | Method for spreading chemical fertilizer onto the field for CGS, foliar spray (yes/no) | |
| chemical_method_ground | Method for spreading chemical fertilizer onto the field for CGS, ground application (yes/no) | |
| Manure fertilizer | ||
| manure_application | Manure spread onto the field for CGS (yes/no) | |
| manure_time | Time since the last manure spreading during CGS (con) | Days |
| manure_age | Age of manure spread onto the field for CGS (con) | Wk |
| manure_source | Source of manure spread onto the field for CGS (dairy farm/poultry farm) | |
| Compost fertilizer | ||
| compost_application | Compost spread onto the field for CGS (yes/no) | |
| compost_time | Time since the last compost spreading during CGS (con) | Days |
| Irrigation | ||
| irrigation_time | Time since the last irrigation during CGS (con) | Days |
| irrigation_source_pond | Source of irrigation water applied during CGS, pond (yes/no) | |
| irrigation_source_well | Source of irrigation water applied during CGS, well (yes/no) | |
| irrigation_source_municipal | Source of irrigation water applied during CGS, municipal (yes/no) | |
| irrigation_source_river | Source of irrigation water applied during CGS, river/stream/creek (yes/no) | |
| irrigation_source_reservoirs | Source of irrigation water applied during CGS, reservoirs (yes/no) | |
| irrigation_method_drip | Method of irrigation for CGS, drip (yes/no) | |
| irrigation_method_overhead | Method of irrigation for CGS, overhead (yes/no) | |
| irrigation_method_spray | Method of irrigation for CGS, spray (yes/no) | |
| irrigation_method_flood | Method of irrigation for CGS, flood (yes/no) | |
| Equipment | ||
| own_equipment | Use of own farm equipment for all operations (yes/no) | |
| equipment_cleaning | Cleaning of farm equipment (yes/no) | |
| Microbial_test | Routine microbial test (yes/no) | |
| Planting_time | Time since planting of spinach (con) | Days |
| Farm environmental factors | ||
| Terrain, buffer zone, and proximity | ||
| terrain | Terrain where the farm is located (flat/sloped) | |
| buffer | Buffer zone from neighbors and roads, etc. (yes/no) | |
| buffer_fence | Type of buffer zone, fence (yes/no) | |
| buffer_ditch | Type of buffer zone, ditch (yes/no) | |
| buffer_road | Type of buffer zone, road (yes/no) | |
| proximity_dairy | Proximity within 10-mile radius, dairy farm (yes/no) | |
| proximity_beef | Proximity within 10-mile radius, beef farm (yes/no) | |
| proximity_poultry | Proximity within 10-mile radius, poultry farm (yes/no) | |
| proximity_swine | Proximity within 10-mile radius, swine farm (yes/no) | |
| proximity_water | Proximity within 10-mile radius, water resources (yes/no) | |
| proximity_landfill | Proximity within 10-mile radius, landfill (yes/no) | |
| proximity_residential | Proximity within 10-mile radius, residential (yes/no) | |
| proximity_forest | Proximity within 10-mile radius, forest (yes/no) | |
| proximity_roadways | Proximity within 10-mile radius, roadways (yes/no) | |
| Domestic/wild animals | ||
| domestic_animal | Domestic animal intrusion of the field for CGS (yes/no) | |
| wildlife | Wildlife intrusion of the field for CGS (yes/no) | |
| wildlife_control | Wildlife control on the farm (yes/no) | |
| wildlife_control_fences | Wildlife control method of the farm, fences (yes/no) | |
| wildlife_control_trap | Wildlife control method of the farm, trap (yes/no) | |
| wildlife_control_hunting | Wildlife control method of the farm, hunting (yes/no) | |
| Farm_location | Farm location (Southwestern U.S./Western U.S.) |
a
CGS, current growing season; con, continuous variable.