New Zealand farmers could be using satellites to see how much grass is on their farms, and even predict how fast it will grow.

It may seem to be a trivial job, but it’s not easy to estimate grass stocks on whole farms accurately. It’s vital information for farmers, but they usually need it most when they are busy with milking or rotating stock.

Grass is their most valuable resource and many of their most important decisions depend on how much grass they have now and can reasonably expect over the following few weeks.

Australian farmers are already using the satellite technology. New Zealand’s dairy cooperative Fonterra has been working with the Australian research organization CSIRO to determine the feasibility of supplying the pastures from space information to the New Zealand dairy industry. Early indications are positive.

Now Fonterra and scientists at Dexcel and AgResearch want to see exactly how well the technology performs in New Zealand.

The scientists have received some funding from Meat and Wool New Zealand and are looking for more so that they can calibrate the pastures from space predictions for farms throughout New Zealand. Calibration is likely to take several years.

The scientists envisage New Zealand dairy, cattle and sheep farmers either dialling into the world wide web to collect information about their own farm, or receiving it via email at regular intervals.

Eventually, they may also be able to compare their pasture growth, and the way it is being used, against other farms and previous years, to help them improve their performance.

The information from the satellites would help them make more confident decisions about when to rotate stock, add fertiliser or irrigate, when to buy and sell stock, make hay and silage, and provide the feed supplies they need for milking, lambing and calving.

At present, only a small proportion of New Zealand farmers find the time to measure their pastures regularly and use the information to prepare a formal feed budget.

Cloud will be more of a problem here than in Australia.

Although the satellites that are currently being used can’t see through cloud, studies of past years have shown that they would have been able to produce measurements every two weeks 75 per cent of the time.

Like weather forecasts, the system does not depend on one satellite. There are many passing over New Zealand, so what one misses, another is likely to pick up.

The satellites use multi-spectral sensors which measure the electromagnetic energy reflected from the farms below. (The process is the same for the human eye.) The sensors can detect varying proportions of reflected, transmitted or absorbed energy to identify soil and different types of vegetation and their mass.