Tule Target PRI: Achieve Full Canopy and Yield Potential
author By Tom Shapland, PhD, April 21, 2015

One of the most important milestones for a successful growing season is sufficient canopy growth to support your yield targets. The new Tule Target PRI helps you get your field to its full canopy size and yield potential.

How Do I Use the Tule Target PRI?

The Tule Target PRI gives you a goal PRI for achieving full canopy size. To use the Tule Target PRI, log into your Tule dashboard and compare your current PRI to the Tule Target PRI .

To use this tool, we assume you are familiar with the Plant Response Index (PRI). For our purposes in this article, it is important to remember the PRI increases as the canopy develops in your field.

If the PRI from your field is already equal to or greater than the Tule Target PRI, then your canopy has already reached a sufficient size. In the figure below from 2014, we see that the PRI reached the Tule Target PRI -- hence, the canopies were fully developed -- by the middle of May.

If your PRI is below the target, but steadily progressing towards the Tule Target PRI, like we see below in the example from 2015, then the current irrigation strategy will likely produce the full canopy size. Proceed with your current irrigation strategy as informed by your Tule Actual ET monitoring.

If the increase in the PRI has slowed before reaching the Tule Target PRI, it is likely an indication that you need to increase your irrigation amounts to achieve the maximum canopy size. Use the measured Tule Actual ET to modify your irrigation levels. Below we see an example from a field in 2014 that did not achieve its canopy size potential.

How does the Tule Target PRI work?

The Tule Target PRI is based on the largest canopies that you have grown in your field over the last three years. The Tule Target PRI is calculated from historic satellite imagery from your field. We obtain the maximum Normalized Difference Vegetation Index (NDVI) between June and July for the previous three years. We transform the NDVI values into the Tule Target PRI, which is the maximum potential PRI for your field.

The Tule Target PRI also takes into account the largest canopies grown in similar fields throughout your region. The canopy in your field may not have reached its full potential size over the last three years -- if, for example, you may have replanted your perennial crop three years ago. We calculate the maximum PRI for similar fields (i.e., fields planted with the same crop, on the same row spacing, etc.) in your region. The Tule Target PRI is the greater of value of either: 1) the maximum PRI in your field over the last three years, or 2) the maximum PRI of similar fields in your region over the last three years.

Got it! Now what?

The Tule Target PRI is designed to help you achieve full canopy development in your field and help you meet your production goal. We at Team Tule are thrilled to release this new feature! If you have any questions, please email support@tuletechnologies.com. We’d love to hear from you!

[Update from April 2016: You now have the ability to choose a Target PRI based on historical data from the last five years. See this blog post for more information about this new improvement.]