FieldStat: A Superpower for Growers
author By Tom Shapland, PhD, July 14, 2015

We are thrilled to unveil FieldStat, a superpower for growers. FieldStat is the superpower to accurately know the water stress of every field, every day, and without wasting time driving to each field. With FieldStat, a grower knows the status of all of his fields – at any time, from any place, and with absolute certainty.

What is it?

FieldStat is the crop water status measured directly in your field by a Tule sensor. It tells you the water stress of your field daily, remotely, in simple terms, and without the hassle of the pressure bomb. FieldStat correlates with leaf water potential (i.e., pressure bomb readings). But unlike the bomb, which only tells you about one plant, FieldStat measures the plant water status for a 1 to 10 acre area. It gives you the power to see the water stress of every field, every day, from anywhere.

The iPhone app displays yesterday’s FieldStat and the Tule Irrigation Recommendations. The web dashboard will include daily, weekly, and seasonal FieldStat measurements (coming soon!).

What does it mean?

There are four categories of FieldStat:

Low Stress Mild Stress High Stress Extreme Stress
FieldStat > 75% FieldStat 65-75% FieldStat 50-65% FieldStat < 50%

Each FieldStat threshold correlates with a midday leaf water potential value. Most growers are familiar with pressure bomb readings, so it is easy to put FieldStat into context. The table below shows the analogous grapevine pressure bomb readings for each FieldStat category:

Crop Water Stress Level FieldStat Midday Leaf Water Potential Equivalent
Low Stress > 75% Greater than -12 bars
Mild Stress 65-75% Between -12 to -13 bars
High Stress 50-65% Between -13 to -15 bars
Extreme Stress < 50% Less than -15 bars

FieldStat Example

Below is an example from a vineyard. The black line is the vineyard FieldStat. The green, yellow, orange, and red background correspond to Low Stress, Mild Stress, High Stress, and Extreme Stress, respectively. The grower wants High Stress in this vineyard (between -13 and -15 bars). The grower irrigated when the vineyard falls below the High Stress threshold on July 13 and July 17 (blue dots). As you can see, the applied water relieved the plant stress, causing the FieldStat to stay within the desired stress range.

How do I use FieldStat?

Target FieldStat

The Target FieldStat is the water stress level required to meet your production goal. The objective is to keep the FieldStat from your field within the range of the Target FieldStat.

The Target FieldStat is set in one of the following ways:

  1. If we have Tule data for your field from last year, the Target FieldStat is the stress level that occurred in your field at this time last year. If you are happy with the yield and fruit quality of last year’s crop, then keep the Actual FieldStat within the Target FieldStat. If you would like a different crop stress level, please tap ‘Help’ at the top right corner of the app to email us with your desired Target FieldStat.
  2. If you are new to Tule, we set your Target FieldStat based on the Target FieldStat of other growers in your region. If you have a different stress goal for your field, please tap ‘Help’ at the top right corner of the app to email us with your desired Target FieldStat.
Goal Summary

We include a short narrative describing the current strategy to meet your production goal based on best practices. If the Goal Summary does not align with your stress goals for your field, please email us an updated Target FieldStat. Just tap “Help” at the top right of the app to let us know.

FieldStat and the Tule Irrigation Recommendation

The Tule Irrigation Recommendation is the amount of water required to keep your Actual FieldStat within the Target FieldStat range over the next seven days. No interpretation or calculations are required.

Know Where to Focus Your Attention (Alert versus On Target)

Each field is classified with a status of either Alert or On Target. We have organized your fields by status to help you decide where to focus your attention and resources each morning. If your Actual FieldStat falls within the Target FieldStat range, your field is On Target. If not, an Alert status is triggered.

How it Works

FieldStat builds on the power of Plant Response Index (PRI) with two fundamental improvements:

  • Clearly defining stress thresholds
  • Making water stress levels easy to compare between fields

This is possible because FieldStat normalizes the Plant Response Index (PRI) by accounting for the maximum canopy size. More specifically, FieldStat is the measured PRI divided by the PRI of your field at maximum canopy size. The result is a universal metric, allowing you to compare water stress across multiple fields, even if the canopy size and weather differ across sites.

An Irrigation Management Superpower

FieldStat unlocks the promise of 21st century technology to make irrigation management easier and exact. We have known there must be a better way to manage water, but it was never in our grasp. It was the stuff of science fiction and superheroes. Now you have it. FieldStat: an irrigation management superpower.

Let us know what you think! We'd love to hear from you.