Yield mapping is an essential tool for precision management of arable crops. Crop yields can be measured once, at harvest, automatically by the harvesting machinery, and be used to inform a wide range of activities. However yield mapping has had minimal adoption by pastoral farmers.

 

Yield mapping is also a potentially valuable tool for precision management of pastures. However it is difficult to practically map yields on pastures, as they are harvested many times through the year, and usually harvested by grazing animals rather than by machine. The pattern of yield variation also varies by season, as different drivers of pasture yield become more influential. Although pasture yield can be mapped using tools such as the C-Dax Pasture Meter, mapping involves an extra operation on top of usual management and is too time consuming to expect farmers to map yields before every grazing / mowing of the paddock. For yield mapping to be practical on pastures, techniques are needed to allow a few strategic mapping events to be used to estimate annual pasture yields.

 

Pasture height was mapped using the C-Dax Pasture Meter, pre- and post-grazing, every grazing, for 12 months on a rotationally grazed, irrigated, ryegrass and white clover dairy pasture in Canterbury, New Zealand. Pasture cover in kgDM/ha was determined from the measurements of pasture heights using calibration equations. Post-grazing pasture cover maps were subtracted from pre-grazing cover maps to obtain maps of pasture intake by cows for each grazing. The intake maps at each grazing event were added together to obtain a map of total pasture intake for the year.

 

The yield variation present in individual pre-grazing maps was compared with the total annual variation in intake by cows, to identify individual maps that give a good estimate of the total annual yield variation. This paper presents an initial protocol that allows a small number of pre-grazing maps to be collected at strategic times of the year, and used to estimate the variation in total annual pasture yield, on a rotationally managed dairy pasture in New Zealand.

 

This method will allow pastoral farmers to practically map total annual yield variation, and use this to inform management in the same way that arable farmers can use maps of grain yield, opening many new management possibilities for pastoral farmers.