New technology enables accurate pasture measurements

This article illustrates how science is improving our pasture production and quality measurements, so farmers with that information can make better management decsions.

Pasture meters are now a regular part of a dairy farmers tools, and are now also being  used by intensive sheep, beef and deer farmers to measure how much grass their farms are producing, to be allocated at appropriate rates for their stock.

Pasture quality analysis is also becoming more and more important, as farmers strive to achieve stock growth rate goals, to meet marketing targets.

Accurate tools are needed to help provide this information and a towed device behind a quad bike, looks like a practical solution that farmers will use.

Funded by the Pastoral 21 feed programme (a joint investment by DairyNZ, Fonterra, Beef + Lamb NZ and the Ministry of Science and Innovation), a team of researchers led by Dr Robyn Dynes, at AgResearch Lincoln, has been working to improve both pasture mass estimation techniques and real-time pasture quality measurements.This research will feature at the AgResearch exhibit at the Fieldays at Mystery Creek on 15-18 June 2011.

To estimate pasture mass, a technology called the C-Dax Pasture Meter has recently been introduced to provide more accurate and rapid measurements than could be achieved using previous devices. One of the key drivers of pasture productivity is grazing management, and how much and how often the pasture is grazed has a direct impact on both pasture production and quality.

The Pasture Meter is a commercially available tow-behind attachment for a quad bike, which enables rapid measurement over a large area. It continuously measures pasture height as the bike moves, and a calibration equation is then used to convert height into pasture mass. The calibrations used to make this conversion have, until recently, been based on restricted field data. Dr Dynes’ team began a project to develop customised calibrations to improve the accuracy of the C-Dax Pasture Meter. The team selected a range of paddocks in regions across NZ, and each month they measured the grass height and then cut, dried and weighed the grass to develop a set of calibrations converting grass height into pasture mass.

These measurements were repeated for a year so that the customised calibrations could be calculated for each region on a daily basis. The calculations were done for a number of dairy farms, as well as for beef and sheep farms in a reduced number of regions.The calibrations should give farmers greater confidence in their ability to measure pasture mass, and now that the calculations have been included in the C-Dax Pasture Meter package, it is even easier for farmers to use them.

Dynes’ team has also focused on improving pasture quality measurements, and are developing new methods that can measure pasture quality parameters in real time, which will enable farmers to respond to diurnal and seasonal changes in nutrients such as protein and carbohydrates. In the past, to get measurements of pasture quality parameters, farmers would have to cut a sample of grass and send it off to a laboratory for analysis. Real-time measurements would enable farmers to react to, and thus take advantage of, short-term changes in nutrient levels. For example, when protein in pasture grass is too high relative to its carbohydrate content, leading to sub-optimal animal production, farmers could feed animals supplemental carbohydrates in the shed, thereby improving their productivity.

In addition, such feeding could also improve environmental performance. When animals ingest too much protein, they excrete the excess in their urine, which is a primary source of nitrogen leaching into groundwater and nearby waterways. High carbohydrate supplementary feed can reduce excreted nitrogen. A second example of how pasture quality measurements can be used to drive both increased production and environmental performance is by using real-time measurements of nitrogen content in pasture to determine whether fertilisers are needed, and to develop a finely tuned, more efficient system for applying fertilisers, rather than just using a simple calendar schedule. Such a system could improve pasture production, reduce fertiliser costs and limit nitrogen losses to the environment.

Although currently no affordable devices are available for farmers to measure pasture quality in real time, such a device could be available in the future. The device will likely also operate as a tow-behind attachment on a quad bike.