Managing subsoil nutrition – a grower experience, James Olsson (Central Queensland Grower Solutions Group)
Author: compiled by Hayley Eames (DAF Qld) | Date: 05 Dec 2018
Take home message
Don’t be afraid to do some trials of your own. You don’t need flash gear, a few modifications to your existing equipment and you can generally get the job done.
James Olsson, Wowan QLD
Figure 1. James Olsson
What did your previous fertiliser program involve?
Starter fertiliser (Granulock® Z) at a rate of 25-40 kg/ha and then side dress urea.
What was the driver for undertaking a subsoil nutrition program?
We had a very reliable paddock that consistently out yielded the rest of our cropping country year in year out. Over a period of about three years under a mungbean/wheat rotation, we really noticed that our mungbean crops were suffering and starting to show visual deficiency symptoms.
Initially we tried applying potash at planting, however as the surface dried out and the crop started looking for moisture, we found the deficiency symptoms returned. This was the first indication that potentially the issue was lack of nutrient at depth.
How did you go about implementing your subsoil nutrition program?
- Depth: 15cm
- Row spacing: 48cm
- Timing: March/April 2015 prior to wheat
Applied Crop King 66S at a rate of 100kg/ha across one paddock. (13 kg N; 10.6kg P; 15kg K; 4.9kg S)
Modified an Orion Centurion chisel plough:
- Initially a 27 tyne machine, have reduced that down to 18 tynes
- Extended the frame from 7.6m to 9m to suit controlled traffic layout
- Equipped with 1,100lbs breakout pressure
- Added hydraulic ram to the front bar to help maintain depth over the contour banks.
We use a John Deere 8760 tractor (300hp) to pull the planter. When it was a 27 tyne machine we required duals to pull it, however modifying it to 18 tynes has meant we have reduced the horsepower requirements and can now use water loaded singles that line up with our controlled traffic configuration.
Figure 2. Modified planter
What results have you observed?
Table 1. Yield results from 2015 and 2016 crops comparing nil treatment and deep applied 100kg/ha of Crop King 66S
(13 kg N; 10.6kg P; 15kg K; 4.9kg S).
Both treatments had starter fertiliser of Granulock Z at a rate of 25kg/ha
We have recouped the cost of application over two crops (wheat & mungbean). The initial fertiliser cost was $80/ha. Based on the 0.5t/ha yield increase at $1000/tonne, we have increased our profitability by $500/ha in our 2016 mungbean crop alone.
Were there any challenges associated with implementing a subsoil fertiliser program?
Getting the timing of application right was our biggest challenge. It was a balancing act between fitting it in with our other business operations and completing it when soil moisture conditions were favourable.
Where to next?
We plan to apply a base rate of N, P, K at depth across all of our cultivation country. As mungbeans are such a big part of our rotation and being such a fast-growing crop, they really can’t afford any setbacks in terms of nutrition.
From there we will continue to monitor levels of nutrient removal through regular soil testing and reassess whether additional deep applications are required in 4-5 years’ time.
What advice would you have for other growers looking at implementing a subsoil fertiliser program?
If you think you are suffering a bit of a nutrient deficiency, get on top of it straight away. We’ve seen a gradual yield decline over the past 8 to 10 years and you can’t sustain or afford inefficiencies in your business in the long term.
Get a comprehensive soil analysis done at depth to accurately determine whether a nutrient deficiency is present.
Finally; don’t be afraid to do some trials of your own. You don’t need flash gear, a few modifications to your existing equipment and you can generally get the job done.
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