Fertiliser toxicity in lupins
15th June 2011
Welcome to NSW DPI online with Barry Haskins, Hillston District Agronomist.
Today we will be looking at fertiliser toxicity in lupins, and some early trial results from this season from a Variety Specific Agronomy trial at Merriwagga in SW NSW.
In western NSW, lupins are probably the most popular legume break crop. They fix nitrogen, and provide a break for leaf and root diseases, as well as allowing us to rotate herbicide chemistry.
Lupins, and in particular albus or broadleaf lupins have been well known to be sensitive to large amounts of fertiliser next to the seed. Most of the research looking at fertiliser toxicity was done in the 80’s and 90’s, when cultivation, wider sowing boots, and narrower row spacings were all very common.
In todays more common farming system, we are tending to utilise less of the seedbed because we have gone to wider row spacings in conjunction with knife point tines or discs in order to sow through stubble.
This has in effect concentrated much more fertiliser with the seed, and research is suggesting that this may be an issue with sensitive crops such as lupins.
In this picture, you can see Rosetta on 25cm with no fertiliser. As you can see we have achieved quite a good plant stand that would be commercially acceptable. As soon as we add fertiliser to exactly the same plot, in this case 60 kg/ha of Superfect, we have really reduced our plant stand to a stage which would not be commercially acceptable.
On 50cm row spacings which you can see in this picture, with no fertiliser we have had a pretty good result, and most of our plants have come up. Again on 50cm row spacings you can see with fertiliser added we have reduced our plant stand. This is quite a marked effect, and as you will see plant numbers were reduced significantly.
In the background you can see where we have taken fertiliser out of the equation all of the plants have developed quite well.
As we widen the row spacing to 75cm, we are concentrating more seed and fertiliser within the plant row. As you can see on the previous slide with no fertiliser, we have had a good establishment. As soon as we add fertiliser we are reducing plant numbers dramatically. Again in the background you can see most of the plants were pretty good where we didn’t add fertiliser.
So in this trial at Merriwagga, we had 6 varieties, 3 were albus lupins or broadleaf lupins, and 3 were angustifolius or narrow leaf lupins, and across all 6 varieties this is what we had as an average of plant stand under the various row spacings. A very common occurrence is to have lower plant stands as we widen row spacings at the same seeding rate. As you can see this trial confirms that. The other thing that we can see is that the impact from fertiliser is greater at wider row spacings.
In each of the graphs you will see here today a 0 indicated no fertiliser, and 1 indicates 60 kg/ha Superfect.
When we look at the effect on individual varieties in this trial, all at 25cm, you can see that the impact of fertiliser has probably had an equal effect on all varieties, so albus lupins and narrowleaf lupins are probably as sensitive as each other if you look at the results from this trial.
If we look at the impact of fertiliser on Rosetta specifically, which were in the video earlier on, you can see that fertiliser has had a larger impact as we widen row spacing, which is what we would expect, and even at 25cm the results were quite conclusive.
So from this trial, we can see that even low rates of fertiliser can affect the establishment of all varieties of lupins in some situations. Whilst there are other trials in recent years that have also shown lupins to be sensitive to fertiliser toxicity, the results from this trial are quite dramatic, and we really need to look at this over a number of years and across a larger number of sites.
These trial results will be available at the end of the season by contacting your local district agronomist.
Barry Haskins, District Agronomist, Hillston.
