By Dr Jeff Reid, Crop & Food Research Hawke’s Bay

“When should I sow for a 250g average root size by early March?”,
“…what about 300g?”,
“What would happen if the germination was only 70%?”

For carrot growers, these sorts of questions are important, but very difficult to answer. New technology from The New Zealand Institute of Crop and Food Research promises to change all that.

The Carrot Calculator is a new product that our team is developing for the carrot industry. Deep down it is based on a mathematical model of how carrot crops grow – but don’t be intimidated! The Carrot Calculator software is simple to load and use, letting you ask and answer straightforward, important questions.

Around the country, carrot crops differ a lot in terms of varieties used, growing methods, and weather. For instance, process carrots are often grown on ridges or on beds with several single rows, whereas table carrots may be grown on beds with several double rows. To keep the Carrot Calculator simple we have decided to produce specialized stand-alone versions for each of the major planting systems.

The prototype Carrot Calculator is set up for process carrots grown on beds with 3 or more single rows per bed. The idea is for people to try this prototype, and let us know what they think. Then, if there is sufficient industry interest we can work on producing customized versions for other situations.

The prototype forecasts potential yield – that is the yield you could achieve if there are no water or nutrient stresses. The customized versions we envisage will be more advanced and adjust the yield for soil fertility, fertilisers, rainfall and irrigation. Even so, there is a lot of useful information to be had from the prototype.

What sorts of information? Have a look at Figure 1, which is a typical Carrot Calculator screen after the program has been started.

The software will work out how long the crop must be in the ground before the average root size reaches a target value. Change this target value (in the bottom left-hand corner), and see how this changes the date when the crop is ready and what the yield could be. Then click on the calendar (top left corner) and choose a new planting date. See what impact that can have on when the crop will be ready. The graph can display how potential root yield (both total and marketable), root dry matter percentage and root size change with time.

Planting density has a big influence on root size and harvest date. This easy to see if you change spacings or germination percentages (top right hand corner of the software window).

If you would like to try the Carrot Calculator you can download a copy and installation instructions from the internet at https://ssl.crop.cri.nz/distribution/carrot/. 


A typical screen view of the prototype Carrot Calculator.