What Is SoilIQ? The Soil Temperature App Built for Growers Who Watch the Ground

What SoilIQ Is — and What Problem It Solves

Most planting decisions in America are made with the wrong data. Gardeners check air temperature. Homesteaders watch the calendar. Farmers go by "when the forsythia blooms" or "after Memorial Day." These are all proxies — rough shortcuts developed before we had better tools.

The problem is that plants don't care about air temperature. They don't know what month it is. They respond to one thing: what the soil around their roots feels like. A plant seed sitting in 48°F soil won't germinate whether it's May 1st or June 15th. And a tomato transplant set into 58°F soil will stall, lose color, and struggle even if the daytime air is a perfect 75°F.

SoilIQ exists to give every grower access to the single most important number in agriculture: real soil temperature at actual depth, for their specific location, updated daily.

Before SoilIQ, getting accurate soil temperature data meant either buying a soil thermometer and checking manually, or finding a university extension office that published data for weather stations near you. Neither option told you what your soil would be doing over the next two weeks, and neither connected that number to what you should actually be planting.

Who SoilIQ Is Built For

SoilIQ is designed for anyone who grows things and wants to do it better. That turns out to be a wide group.

The app skews toward engaged, data-literate growers who've grown frustrated with generic planting calendars and want something more precise. They're not looking for a "plant this in April" reminder — they want to know what their soil is actually doing and what that means for what they're growing.

SoilIQ also serves a meaningful segment of users who aren't dedicated growers at all: weather enthusiasts, data nerds, and homeowners who simply want to understand their land better. The soil temperature data is interesting and useful on its own, independent of any specific crop decision.

Soil Temperature at Four Depths

This is the core feature — the one that everything else is built around. SoilIQ shows you soil temperature at four depths simultaneously, updated daily based on current weather and a physics-based heat transfer model:

Most planting guides reference one generic soil temperature without specifying depth — which is part of why they're unreliable. A 55°F reading at 2 inches means something very different than 55°F at 6 inches. SoilIQ shows you all four so you can match the right depth to whatever you're planting.

The app lets you select which depth is displayed as your "primary" reading — shown as the large hero number on the main dashboard — and you can switch between depths with a tap. The depth selector is prominently positioned so you always know what you're looking at.

14-Day Soil Temperature Forecast

Knowing today's soil temperature is useful. Knowing the trajectory over the next two weeks is what actually drives decisions.

SoilIQ's Forecast tab shows a 14-day projection of soil temperature at all four depths, displayed in three formats:

List view — Day-by-day readings with high/low soil temp, precipitation, and a color-coded condition indicator. Scrollable and quick to scan.

Chart view — A line chart plotting all four depth temperatures over the 14-day window, with an ideal growing range band overlaid in green. You can see at a glance when your soil is entering or leaving the optimal range for your target crops.

Heatmap view — A color-coded grid showing relative soil warmth across all 14 days and all four depths simultaneously. Excellent for identifying the exact day a warming trend crosses a key threshold.

The forecast also displays Growing Degree Days (GDD) — a heat accumulation metric used by agronomists to predict crop development, pest emergence, and harvest timing. SoilIQ shows both the projected 14-day GDD accumulation and the recent 3-day GDD, so you can see whether your season is running ahead of or behind typical patterns.

PlantAI — Planting Windows for 133 Crops

PlantAI is SoilIQ's AI-powered crop analysis engine. Every day, it evaluates your current soil temperature, moisture level, and recent weather against the specific planting requirements of 133 crops and sorts them into four categories:

Every crop in the PlantAI list shows the specific reason it's categorized the way it is: "Soil 54°F — needs 60°F+" or "Soil 78°F — above 65°F max for this crop." You're never left guessing why something is or isn't ready.

The 133 crops span 13 categories: vegetables, herbs, fruits, grains, legumes, root vegetables, brassicas, alliums, grasses and turf, cover crops, melons, cucurbits, and flowers. Whether you're timing tomato transplants, overseeding fescue, or establishing a cover crop after harvest, PlantAI has a data-driven window for it.

Tapping any crop opens a full detail sheet with its minimum, ideal, and maximum soil temperature thresholds, germination time, days to maturity, and a personalized planting window based on your current location's forecast.

Soil Health Score

Beyond temperature, SoilIQ synthesizes your current soil conditions into a single 0–100 Soil Health Score — displayed as a ring indicator on the main dashboard alongside four contributing metrics:

• Soil Temperature — How close the current reading is to optimal growing range (for the broadest range of crops)
• Moisture Level — Derived from recent precipitation, evapotranspiration rates, and seasonal patterns
• Recent Trend — Whether soil is warming, cooling, or stable — and at what rate
• Frost Risk — Probability of a frost event within the next 7 days, factored into the overall score

The score drives the condition text on your dashboard — ranging from "Excellent Growing Conditions" at the top of the range to "Frost Risk — Protect Plants" when temperature drops are forecast.

The Soil Health Score gives you a one-glance answer to the question growers actually ask when they walk outside: "Is today a good growing day?" The supporting metrics are there when you want to dig into why.

Growing Journal

SoilIQ includes a growing journal built specifically around soil data. Unlike generic garden apps that let you record planting dates and add notes, SoilIQ's journal automatically ties each entry to the actual soil temperature conditions at the time of writing.

Every journal entry captures:

• The date and your location
• Actual soil temperature at all four depths at time of entry
• Moisture level and recent precipitation
• Your written notes
• Up to 4 photos (resized for efficient storage)
• Crop or activity tags

The journal's most useful feature is the soil temperature progression chart — a sparkline that plots soil temperature over time across all your entries. If you recorded observations through spring, you can see exactly how your soil warmed, when it crossed key thresholds, and how that corresponded to what you planted and how it performed. This is the kind of multi-year ground truth data that professional farmers pay a lot of money to generate.

Widgets and Live Activity

SoilIQ's soil temperature data doesn't stay locked inside the app. The widget system brings it to your home screen, lock screen, and even your Dynamic Island.

Home screen widgets come in three sizes:

• Small widget — Current soil temperature at your selected depth, current condition, and trend arrow. Glanceable at a glance from any home screen.
• Medium widget — Adds depth label, location name, and a short condition description alongside the temperature.
• Large widget — Full hero temperature display plus a 5-day forecast bar chart showing the soil temperature trajectory. Ideal for growers who want their weather-equivalent dashboard always visible.

Lock screen widgets show the current temperature and depth in compact form — visible without unlocking your phone, so you can glance at soil conditions while working outside.

Live Activity — On supported iPhones, SoilIQ can run a persistent Live Activity in the Dynamic Island and on the lock screen. The Live Activity shows real-time soil temperature with a condition indicator, and updates whenever conditions change. It's particularly useful during frost risk periods — you can enable it to keep a constant eye on whether the soil is approaching dangerous temperatures for cold-sensitive plants.

Apple Watch App

SoilIQ includes a full Apple Watch companion app, letting you check soil conditions directly from your wrist without pulling out your phone.

The Watch app displays:

• Current soil temperature at the selected depth
• Soil condition label ("Ready to Plant," "Too Cold," "Warming," etc.)
• Trend indicator (warming/cooling/stable)
• Your current location name

The Watch app also supports complications — small data displays that appear on your watch face. Set up a SoilIQ complication and you'll see today's soil temperature every time you glance at your watch, alongside your steps, heart rate, or whatever else is on your face. For growers who spend significant time outdoors, this is genuinely useful: no need to reach for your phone to remember whether the soil was in range this morning.

Multiple Locations

SoilIQ supports saving multiple locations — essential for growers managing more than one property or garden.

Common uses:

• Home garden + weekend property — Different soil types, different elevations, different microclimates. Both available instantly with a tap.
• Multiple client properties — Landscapers and lawn care professionals can track soil conditions across client sites and make site-specific recommendations.
• Front yard vs. back yard — Surprisingly useful for large suburban properties where sun exposure creates meaningfully different soil temperatures on opposite sides of the house.
• Family farm locations — Different fields, different planting zones, tracked independently.

The free version of SoilIQ supports one saved location. SoilIQ Pro unlocks unlimited saved locations.

Probe Calibration

SoilIQ's soil temperature model is highly accurate for most users, but soil is hyperlocal. Dark soil absorbs heat differently than light sandy soil. Mulched beds hold temperature differently than bare earth. A shaded north-facing slope reads different than an open south-facing bed — even on the same property.

For users who want maximum precision, SoilIQ supports probe calibration. If you have a physical soil thermometer — a $12–15 probe you push into the ground at a specific depth — you can enter your actual reading into SoilIQ and the app will adjust its model for your location.

The calibration is saved per depth and per location. Once set, SoilIQ uses your real-world measurement as a correction offset, so the app's data reflects your specific garden's actual conditions rather than the generalized model for your coordinates.

The Data Behind SoilIQ

SoilIQ's accuracy comes from the quality of its underlying data sources and the model that connects them.

Forecast data: SoilIQ uses Open-Meteo, a high-resolution meteorological data service that aggregates global weather model output from NOAA (National Oceanic and Atmospheric Administration), the European Centre for Medium-Range Weather Forecasts (ECMWF), and other national weather services. Open-Meteo provides hourly soil temperature readings at four standard depths, updated multiple times daily.

Historical data: For seasonal context — understanding what soil temperature typically does in your region across the year — SoilIQ uses the Open-Meteo historical archive, which provides verified weather data stretching back decades. This powers features like the multi-year soil temperature trend view and the historical monthly averages used to calibrate the forecast model.

The depth model: Raw meteorological data is delivered in metric depths (0, 6, 18, and 54 centimeters), which SoilIQ translates to the consumer depths displayed in the app (surface, 2", 6", and 21"). A physics-based heat transfer model accounts for precipitation cooling effects, recent moisture levels, and seasonal thermal patterns to produce readings that reflect actual field conditions rather than raw model output.

Update cadence: Soil temperature data refreshes automatically when you open the app, with a freshness guard that prevents excessive API calls. Background refresh keeps your data current even when the app isn't open, so your widgets always display current conditions.

Free vs. Pro

SoilIQ is free to download and useful from day one. The free tier delivers live soil data and health intelligence. Pro unlocks the full forecast, crop AI, and field journaling for serious growers.

The free tier gives every grower access to real soil temperature intelligence — the live readings and health score that matter most. Pro adds the full forecast, crop AI, and field journaling for those who want the complete picture.

Platforms and Availability

SoilIQ is available on the following Apple platforms:

SoilIQ works globally — wherever you have GPS signal and a data connection, the app can pull soil temperature data. It's been used by growers in North America, Europe, Australia, New Zealand, and South America. The only thing that changes with location is the underlying weather model data resolution, which is highest in North America and Western Europe and somewhat lower in more remote areas.

Frequently Asked Questions

Does SoilIQ work offline?

Partially. SoilIQ caches your most recent soil temperature data and forecast locally, so you can view the last-fetched data without a connection. New data requires an internet connection to refresh. The journal and all local features work fully offline.

How often does the data update?

SoilIQ refreshes data automatically when you open the app, subject to a 15-minute freshness guard to prevent excessive API calls. Background App Refresh updates data periodically when the app isn't open. Widgets update on their own schedule and reflect the most recently fetched data.

Can I use SoilIQ without sharing my location?

Yes. If you prefer not to use GPS location, you can manually search for and save any location by city name or address. The app will use that saved location for all soil temperature data rather than your device's GPS position.

How does SoilIQ's soil temperature compare to a physical probe?

In most cases, SoilIQ's model-based readings are within 2–4°F of actual soil temperature. Accuracy varies with local soil composition, mulch cover, shade patterns, and other hyperlocal factors. The probe calibration feature (Settings → Probe Calibration) lets you enter an actual reading and adjust the model to match your specific garden's conditions — closing most of that gap.

What's the difference between soil temperature and air temperature?

Air temperature fluctuates dramatically through the day — often by 20–30°F between night and afternoon. Soil temperature is much more stable, especially at depth, because soil stores thermal energy and releases it slowly. Surface soil might track air temperature loosely, but at 6 inches, readings typically shift by only a few degrees over 24 hours. This stability is why soil temperature is a far better predictor of plant growth than air temperature.

Does SoilIQ work for warm-season crops like bermuda grass and sweet corn?

Yes. PlantAI covers warm-season crops including corn, sweet corn, watermelon, cantaloupe, okra, southern peas, and warm-season grasses including bermuda and zoysia. The thresholds for warm-season crops are higher — corn needs 50°F minimum, bermuda needs 65°F for active growth — and PlantAI accounts for this correctly.