Ag Productivity refers to the amount of carbon plants capture through photosynthesis and then stored as new above-ground plant mass. Here it is the rate of accumulation of carbon mass (grams of carbon per square metre per day, gC/m2/d). Valid values range from around -1 to 5. Units of Productivity can go negative when plants lose more carbon in keeping themselves alive (via respiration)
than they gain through photosynthesis. Note that the Ag Productivity estimates do not discriminate between different types of crops, pastures or grasses.
This is not the same as the total mass, that is, total above ground biomass. As a rule of thumb, biomass is about twice carbon mass, so to convert these Ag Productivity data to biomass they need to be doubled.
How is it different to NDVI ?
Ag Productivity data provide more powerful insights into productivity than the more commonly used Normalised Difference Vegetation Index (NDVI). NDVI is a spectral index and, while it is strongly related to foliage cover, has no inherent biophysical meaning. To derive meaningful information from the NDVI it must be related (calibrated) to some local, physical attribute, such as biomass or cover. Even when locally calibrated, the NDVI by itself is not always a good indicator of productivity because it saturates when cover is high (such as in the north’s wet season, the south’s dark winter months, and in the peak of the cropping season).
How can I use these data?
Ag Productivity is a biophysical variable that provides an excellent indication of pasture, grassland and crop production.
As estimates are produced every few weeks, they provide detailed insights into how variable productivity has been and how it is currently changing. Uses can include:
- Examine how the productivity of a given paddock has varied over the past 20 years, allowing for comparisons to made between current productivity and the average productivity for the same time of year.
- Compare the progression of the current season to that of previous seasons to get a feel for possible trajectories of the coming months.
- Gauge how well a given paddock is performing compared to surround paddocks in a region or further afield (even nationally). Such benchmarking can be useful in assessing the effectiveness of management strategies.
- Understand how productivity relates to crop yield and grazing records
- Assess at a regional level how the season is progressing to provide indicators of the likely production of livestock or grain in the region, or the demand for feed. This can further inform transport and processing requirements.
Pricing
Ag Productivity is priced as a monthly subscription. Purchasing from the shop will set up a recurring monthly charge to your nominated credit card.
See the Ag Productivity Grid page for further details and accessing the sample or subscription data.
1 Donohue, R.J., Hume, I.H., Roderick, M.L., McVicar, T.R., Beringer, J., Hutley, L.B., Gallant, J.C., Austin, J.M., van Gorsel, E., Cleverly, J.R., Meyer, W.S., & Arndt, S.K. (2014). Evaluation of the remote-sensing-based DIFFUSE model for estimating photosynthesis of vegetation. Remote Sensing of Environment, 155, 349-365. https://doi.org/10.1016/j.rse.2014.09.007.
2 Donohue, R.J., & Renzullo, L.J. (2015). C-Store: an Australian remote-sensing and observation-driven carbon assessment system. In. Canberra: CSIRO. https://doi.org/10.4225/08/5a3953b0a4d5c.
