Like many graingrowers, Mike Smith had a pretty good idea of the high- and low-yielding areas of his cropping paddocks at Gurley, south of Moree. They'd been easy to see from the header cabin over the years.
And it worried him when it came to deciding fertiliser rates. He knew he would be wasting money with high applications to the poorer-performing areas, yet he didn't want that reality to lock him into conservative rates across the rest of a paddock.
Now, do-it-yourself development of precision farming on 1,300 hectare 'Tarnee' - 1,000 hectares cropped, 300 of 'nature' - means Mr Smith can fertilise each area to its target yield.
For example... A 276-hectare paddock of durum wheat in 1999 saw variable-rate fertiliser applied as:
- nitrogen: 140 kg/ha on 191 hectares; 115 kg/ha on 71 hectares, 70 kg/ha on 4 hectares and 50 kg/ha on 10 hectares
- phosphorus: 20 kg/ha on 191 hectares, 16 kg/ha on 71 hectares and 8 kg/ha on 14 hectares.
Based on $0.64/kg for N as urea and $2.56 for P in a 50-50 mix of Starterphos and Starter-Z, Mr Smith calculated his total savings at $2,889, or $10.44/ha.
Mr Smith began yield monitoring and mapping in 1996, discovering differences of up to 1 t/ha within the same paddock.
"We had been increasing fertiliser rates over the years but you can't put 150 units of N on the 30 per cent of a paddock that is only going to use half the fertiliser," he says. "We were never going to get any better out of them. It was a question of what can we get out of the better areas, with more moisture-holding capacity, which have most potential to lift yields."
Today's level of precision farming on 'Tarnee' didn't come easily. Mr Smith used a 'push probe' along with more high-tech GPS and mapping software to develop a farm map of soil depth. He took random soil cores "every 100 metres or so", carrying out most of the work when the moisture profile was pretty full.
(More recently, GRDC-supported researchers from the University of Sydney included 'Tarnee' in electro-conductivity soil mapping in northern NSW, with their results largely corresponding with the data Mr Smith generated with his manual probe.)
Mr Smith's next step was to automate variable-rate fertiliser and seed capability on his Gyral SR airseeder, only fully achieved in 1999. He found a Raven two-channel controller which could communicate, through his computer, with the AgLeader yield monitor fitted to the header and eventually control seeding, fertiliser and spray applications.
Then he sourced a Spragg variable-rate gearbox, with twin output cogs, for the Gyral airseeder and its two bins. The Raven controller varies the speed of both output drives to achieve variable-rate application. GPS and controlling equipment software is fitted to a John Deere 7800 tractor.
"I had to source and set up all the equipment because, at the time, I felt the commercial units were unsuitable, unavailable or much too expensive," Mr Smith says. "I did have a few wiring problems but, with the Spragg unit, if the electrics failed in the early days I still had a manually adjustable gearbox, and could set it by hand.
Finally, fully automated
"Last year was the first time I was fully automated. In 1998 I only did patches by visual assessment on the go, that I knew needed to be varied.
"There are obvious areas which should get only 50 units, but it is harder to tell where you should move from 100 to 120 units. So automation is required to achieve this, and avoid too many 'trial strips', where you forgot to change rates."
Despite the obstacles, Mr Smith enjoys his move to precision agriculture and the increasing reliance on computer technology. "I like doing the work myself and I have a special interest in precision agriculture," he says. "To run a financially viable farming business now — and in the future — costs, potentials and efficiencies need to be addressed and I believe precision technology can help provide some solutions."
The Smiths are working with a group of farmers, the University of Sydney and Incitec on a GRDC project to expand the exposure of precision farming methods in the Moree-Narrabri area. They are also cooperating with Queensland's Department of Primary Industries in research into protein and yield relationships within a paddock.
"We have done some yield mapping to enable higher rates to be targeted at heavier infestations, and tried mapping the levels of Ascochyta in chickpea in 1999 to see if there was any relationship between levels of infection," Mr Smith said.
Voted best regional communicator
Queensland Farming Systems Institute crop nutrition expert Wayne Strong won the GRDC's 2000 'Seed of Light' award for the best grains research communicator in northern NSW and Queensland.
With 30 years of experience in R&D on soil fertility, crop nutrition and field crop production, Dr Strong won the award for "a significant and valued contribution to the success of northern GRDC Research Updates". GRDC chairman Grant Latta presented Dr Strong with his award at Grains Week in Brisbane earlier this year. He later celebrated his victory with FSI board chairman, graingrower Marg Cover.
Contact: Mr Mike Smith 02 6754 6816