Experiences with using PGR  and FOO data

From Kelly et al (2003)

House et al (2002) reported the case studies of three farmers that successfully used remotely sensed pasture biomass and growth rate information to manage wool quality in fine wool sheep flocks based on the principle that there is a strong positive relationship between pasture biomass and fibre diameter of wool by merino sheep in spring.  Their objective was to reduce mean fibre diameter, and increase staple strength in fleeces of young merino sheep.  Overall fleece value per head increased by AUD$ 16.30, AUD$ 8.93 and AUD$ 2.63.  The additional benefit from running more sheep in a smaller area of land and releasing extra hectares for other farming activities were not measured.

In 2001 in a separate case study (Coole, R, pers comm by R. Kelly) the value of the information on pasture biomass and growth rate was estimated at AUD$ 6-10 per sheep.  The ability to capture these benefits was dependent on the satellite technology, because of its accuracy, the fact that it provided spatial distribution of plant biomass, and its reduced labour requirements by eliminating the 1 day per week needed to monitor pastures.

The value proposition for remote sensed estimates of feed on offer and pasture growth rate

From Gherardi and Oldham (2003)

Case study 1 (management of wool production to forward contract and budget for silage production)

Richard Coole farms 5500 ha spread over 6 farms between Frankland and Boyup Brook, approximately 400 km south of Perth.  Approximately 40% of the arable area is planted to crops and he runs 35400 DSE at a winter grazed stocking rate of 12.9 DSE/ha with an average annual rainfall of 600 to 700 mm.  In 2001, Richard used satellite-sourced estimates of FOO and PGR to both manage wool production and increase pasture utilization on his farm.  In concert with the satellite based pasture technology, he used the ‘measure as you grow’ approach to manage the wool production in two and four tooth dry ewes to a predetermined fibre diameter, staple length and staple strength by restricting their intake in winter-spring.  Because he was so confident that he had the tools available which would allow him to hit his target, he made the decision to forward sell 300 bales (a third of his clip) of 18-19 micron wool with a staple strength of around 30 N/ktex. 

 Through a combination of technologies he was able to meet his forward contracts and realize a profit of $50,000 over what he would have achieved if he had sold his wool into the spot market.  The profit achieved through the forward selling of his wool does not take into account the extra profit achieved over and above his current grazing management, through the management of wool production during winter-spring.  The surplus land that became available as a result of the more intensive grazing of dry ewes provided him with the option of fodder conservation.  He used the weekly PGR and monthly FOO predictions to develop feed budgets for his livestock and to provide him with the information as to how much land he should lock up for silage production.  He valued the 1,500 tonnes of silage produced from the surplus land at $150,000 (i.e. $100/tonne). 

 He also claimed that the provision of remote sensed PGR and FOO resulted in a labour saving by eliminating 1 day/week of the time needed to monitor pastures during the growing season.  This saving in labour for a skilled person was valued at around $3,900 per year ($30,000 annual salary).  In addition, the technology was used in the management of his five remote properties that resulted in a further labour saving to the enterprise.  The technology provided him with additional time to spend on making strategic and tactical management decisions on his farm. 


Case study 2 (use of historical knowledge of PGR to test the feasibility of a radical change in grazing management)

Brad Wooldridge farms 502 ha, at Arthur River, approximately 250 km south of Perth.  Approximately 60% of the arable area is planted to crops and he has traditionally run 2645 DSE at a winter grazed stocking rate of 12.2 DSE/ha with an average annual rainfall of 500 mm.  In 2002, Brad used satellite-sourced estimates of past PGR information to make a major stocking rate and grazing management decision for his farm.  His aim was to increase his stocking rate to 14 DSE to increase pasture utilization by better matching his total animal requirements to total pasture production and therefore stocking for an “average year” rather than the more conservative approach he had taken previously. 

 At the break-of-season in April he was running 12 DSE/winter grazed ha, with both his ewe and wether hoggets agisted on stubbles in the wheatbelt.  Following the return of the ewe hoggets in early May, the stocking rate had increased to 14 DSE/winter grazed ha, his target for the year.  By the end of May the season had not broken where he had the wether hoggets agisted and they returned increasing his overall stocking rate to 18 DSE/ha.  The decision had to be made as to whether the current stocking rate was going to be sustainable over the growing season or whether he would need to sell surplus stock and when they should be sold. 

 Feed budgets were undertaken using historical information and previous satellite based information on PGR, along with a pasture allowance per DSE (Grimm 1998).  The conclusion was that the 18 DSE/ha was probably sustainable but would need the weekly satellite based PGR information to monitor the situation.  The decision was also made to use the satellite based FOO and PGR information to help rotationally graze his reproducing ewes in order to optimize the production of both the animals and the pastures. 

 He recognized that the satellite based pasture information was a key tool used in the strategic and tactical decision making processes on his farm.  The ewe flock quickly adapted to the rotation so long as they were only moved directly from one paddock to another when the residual FOO reached 500 to 800 kg/ha; that is transferred through a single gate between adjoining paddocks.  Over lambing, ewes and lambs that stayed behind were picked up in the next move with little or no effect on lamb survival.  There was a 5-day cold period in July when the PGR slowed dramatically and the rotation became very tight.  However, the increase in stocking rate was sustainable and the ewes produced finer and stronger wool than normal resulting in a 150% increase in the profit of his livestock enterprise.  He thought that other important spin-offs of the technology include its ability to identify low performing paddocks and areas within paddocks.  By addressing the issue of poor paddock performance producers will be in a better position to sustain higher stocking rates on their farms in the future.

My experience with satellite predicted estimates of feed on offer and pasture growth rates  

From House (2003)  


Wool producers and Scientists have long recognized the need for reliable and accurate pasture measurements and a number of producer training and educational groups have been formed such as Prograze and Woolpro etc. These groups are aiming to train producers to become better at evaluating their pastures so they can make informed grazing decisions to better utilize the available pasture. Visually evaluating pastures and cutting the necessary calibration samples is a time consuming job and results from my experience in our local Woolpro group clearly showed that producers ability to accurately predict feed on offer is variable; even very experienced technicians can occasionally get it very wrong.

 Developing a sustainable and efficient grazing system requires a clear understanding of pasture availability, how animals respond to changes in pasture availability, and therefore what pasture conditions are required to achieve target levels of feed intake and animal performance. Effective feed budgeting requires accurate and timely estimates of feed on offer and pasture growth rates. As discussed previously, I have convinced myself that current visual methods for feed budgeting are not sufficiently accurate in my hands to be cost effective 

In February 2001, I was approached to join a group who were investigating the feasibility of using Satellite images to predict green pasture biomass or feed on offer and pasture growth rates. The predicted estimates of feed on offer and pasture growth rates were reported retrospectively, 3 weeks after the satellite over pass. In 2002, the estimates of feed on offer and pasture growth rates were reported within 5 days of the satellite over pass and detailed 8 day weather forecasts were used to provide forecasted estimates of pasture growth rates 7 days ahead. This information was posted on a secure website or e-mailed. This paper will report on some of the ways I attempted to use this information to improve the productivity on my farm.

 Flock structure and grazing management

I have been farming for most of my life at Kojonup, which is situated in the southwest of Western Australia. The farm consists of about 850 arable ha and the average annual rainfall is around 550mm. My flock structure in the past has been 50% dry sheep 50% mated ewes but in the last couple of years have increased the ewes up to 65% of the flock. Up until the early 1990’s cropping was a very small part of the farms income but as wool became less profitable cropping was increased from 10% to 35%. Also during this time I changed my grazing management. I first started Strip Grazing my wethers at the modest stocking rate of 20 DSE/ha during winter and have gone as high as 35 ha/ha during winter in 2001. Also in 2001 I started to strip grazing my weaners. This gave me the option to run my ewes at a lower stocking rate to benefit the lambs. Now with the results from the Life Time Wool Program which has been running for two years in both Victoria and Western Australia, I am now reassessing the grazing management of my ewes and am involved in the on farm application of the research.

 Feed Budgeting

The key to higher productivity in the future hinges on increasing pasture utilization that in the past has been less than 40% at average district stocking rates. To achieve this producers need to be able to feed budget. Accurate feed budgeting requires knowledge of how much pasture is on offer (feed on offer) and how fast the pasture is growing (pasture growth rate) to know how long the flock can graze at that stocking rate. In the future with these measurements provided via the satellite it will be a time efficient method of determining the grazing days available on your property. This year we will be using a computer program called PAM (Paddock Action Manager) to run a feed budget for the whole farm. It is planned that the computer program will automatically download the new information from the web site, when I turn it on in the morning, and plot the estimated accumulation of feed on offer in each paddock. I will be able to set critical decision aids such as the minimum level of feed on offer for cessation of hand feeding after the break and minimum or maximum levels of feed on offer in particular paddocks. When, I check PAM later in the day, there will be clear reminders if any of my preset limits have been exceeded. In the future PAM or similar farm management packages may also do feed budgeting calculations similar to current decision aids such as ‘PRO Plus’ which will make the process very time effective.

 Last year the paddock that was being used to calibrate the satellite ran extra sheep. Usually I would split some off the mob before lambing but I had the confidence to leave them all in the paddock after doing a feed budget. The 30 ha paddock ran 15dse/ha in 2002 when usually it would only run 11-12 dse/ha. Last year the pasture growth rate in June was 20+kgs/ha/day when we would normally expect less than 10 kg/ha/day.

 Historical Information

Information from past years, which can also be provided from the satellites, can be used to create trigger points for decisions that are needed to be made about stocking rate for a particular year. Rather than just stocking to the worst pasture years, as has been the practice for a lot of producers, we now have the ability to find out how our pastures performed given  a range of dates for the break of season and variable amounts and distribution of rainfall over the growing season. During 2000, which was a very poor year I was able, to maintain my stocking rate due to the fact that all my dry sheep were being strip grazed, and I had sufficient silage to get the ewes through. It shows what can be produced per tonne of dry matter grown. Knowing Pasture Growth Rates gives us the ability to make capital decisions about our sheep with some certainty rather than plain old guess work.

Figure 1. Historical Pasture Growth rates for my farm for the years 1995 to 2000

Yield Mapping

Theoretically, the information about the spatial distribution of feed on offer provided by the satellite images may also give me the opportunity to identify high and low performing areas of pasture paddocks (see Figure 2). The low performing areas can be soil and tissue tested to identify reasons for poor performance. It may be as simple as low plant density or waterlogging and options can be explored to remedy the problem. In the future more and more wool producer will have the option of treating the pastures like crops and improving productivity markedly.

Figure 2. The spatial distribution of feed on offer showing areas within paddocks at the peak of the growing season in September 2002

 Precision Wool Growing

Staple strength in sheep often depends more on the amount of wool grown on green feed, than on the low point on dry feed. The minimum diameter varies less than the maximum diameter reached in spring, Figure 3 shows a graph of the micron profile for a mob of young sheep I split at random and managed differently. One mob was set stocked at 13 sheep/ha and basically had adlib grass from the break of the season. The other mob I strip grazed at 33 sheep/ha to restrict intake. Strip grazing decreased the average fibre diameter from 18.8 to 17.4 microns and increased staple strength by 4.6 N/ktex. Although the clean fleece weight was reduced by 200 g/hd the overall value of the fleece was increased as was the wool cut per hectare. The satellite technology should make this far easier to achieve over the whole farm by grazing to set feed on offer targets and increasing the staple strength and lowering micron of as many mobs as required.  

Figure 3.  Fibre diameter profile showing average micron at monthly intervals for both strip grazed and set stocked ewe weaners, shorn as lambs in April and again in February the following year


The use of the satellite technology in the future is dependent on the ability of the providers to deliver in a cost and time effective manner. Even at this stage the accuracy is acceptable as it takes into account the whole paddock, which is something that would take producers far to long. We found that even a 1 kilometer transect was not representative of the whole paddock in some cases. Last year the delivery of information was poor due to cloud cover but there has been some more work to overcome this with the use of different satellites that are passing over more frequently. This information is just the tip of the iceberg as there are developments going on at the moment to look at the dry biomass plus other properties of the pasture.



Copyright © 2003 Pastures from Space
Last modified: October 01, 2003

Disclaimer of Liability