VIDEO: Measure GAI with Farmers Weekly/BASF iPhone app

Farmers Weekly has combined with BASF to launch a simple-to-use specific agronomic tool for growers with an Apple iPhone.

The BASF/Farmers Weekly Mobile GAI tool iPhone app will help growers make instant judgements of the green area index of oilseed rape crops in the field, and shape fertiliser and growth regulatory fungicide decisions this spring.

The app, which is developed for the UK market, has been designed to provide the same functionality as the existing web tool, which is available on

However it offers several advantages over the computer-based web version, says Will Reyer, BASF’s oilseed rape product manager.

“The ultimate aim is for growers to take pictures of their crops and then receive the GAI for that crop almost instantly,” he explains.

“You can also process other photographs, either taken with that phone earlier, or ones uploaded to your phone to be processed with the app.”

Previously, pictures needed to be taken and downloaded onto a computer and uploaded to the website before any indices could be calculated.

In addition, using the app on the iPhone offers GPS functionality which allows the user to pinpoint where photographs are taken on a Google interactive map, Mr Reyer says.

Lincolnshire grower Ben Atkinson was impressed by the app after the product was demonstrated to him by Mr Reyer.

“I think the app is a useful crop management tool for a grower or an agronomist to make an educated assessment of the crops,” Mr Atkinson says.

“It allows you to walk around the field, do a number of GAI calculations and tailor your nitrogen requirements, or help decide whether the crop needs PGR manipulation.”

Mr Atkinson says growers have an environmental responsibility to apply artificial nitrogen fertiliser sensibly and the app would help achieve this goal.

“It’s proven that you can tailor nitrogen applications according to the green area index and the app is a useful tool to give you an accurate read-out to assess GAI, especially with the rising price of nitrogen,” he says.

The app is available for use with the Apple iPhone through Apple’s iTunes store, and costs £1.79. It will be released on other platforms if it proves successful this season. Click here to find out more and a link to the iTunes store.

What is green area index?

Green area index is the ratio of plant green area to the area of soil the crop is being grown on and it helps growers predict how the crop will look at harvest and allow them to manage the crop accordingly.

A clever mathematical model developed by ADAS based on reference photos calculates the GAI, from which growers can determine nitrogen management for the season and whether a growth regulatory fungicide will be beneficial.

Mr Reyer says the app is specifically designed for the use of Sunorg Pro (metconazole), BASF’s fungicide, but it can be used with other products.

“Ultimately, the app helps people to determine how best to use Sunorg Pro and to get the economic benefit out of it,” he said.

“But it can be used as a general agronomy tool for oilseed rape growers to determine whether it is right to use other inputs.”

How to use the app


1: After downloading the app from iTunes, tap the icon to launch the app.

iphone-22: The app home page will show latest messages and in-season advice, as well as recent photos, from which the GAI reading can be calculated. Along the bottom of the page are five navigation icons that allow the user to switch between taking a photo, viewing stored photos, accessing messages and further information.

iphone-33: By tapping the capture photo icon, you access a screen from which you can take a new picture.

iphone-44: The picture is taken using the iPhone’s camera, and ideally needs to capture about 1m of crop. The app then calculates the GAI virtually instantly, even if there is no signal.

iphone-55: Reference photos can be found by tapping the info centre icon, as well as links to the BASF and Farmers Weekly web sites.










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