|Sorghum, Toongabbie, 5 May 2011|
Photo above (5 May 2011) is the sorghum approaching maturity. You may notice that just left of centre (in line with the electricity pole at the far end of the paddock), there is a change of hybrids. The headland was also sown to a different hybrid, it came up thinnner and so has more late tillers.
The photo below (5 June 2011) is the sorghum almost ready to harvest. It has been sprayed out but some of the tillers are still quite green.. Interesting photo with Loy Yang power station in the background (climate change, global warming, etc) and a crop that is not usually grown until you go several hundred kms north of here. :) Bring it on I say, as we're still a bit cold to really grow sorghum well as I'll discuss below. 1 degree warmer and our spring would start 2 weeks earlier and our autumn would finish two weeks later. Our summer would be 1 month longer. Bring it on!
|Sorghum, Toongabbie, 5 Jun 2011|
The plant above has 4 heads on it. The main shoot is in the front with a reasonable tiller on each side, a third tiller has come out the back of the plant and you can see it's head tiny head on the left. The next photo shows all four decapitated heads.
|Sorghum, main shoot and 3 tillers|
My agronomist friend in Alberta, Canada, Steve Larocque sends me his agronomy newsletter every week. It might sound strange, but it occured to me one day that sorghum growing in southern Victoria is much the same as wheat growing on the Canadian prairies. I'll explain.
In Canada they plant their wheat in April and May, as early in the spring as they can while avoiding frosts and cold soils. They have a very short window to get their crop in as it has to mature in time to avoid frosts at the other end. The harvest takes place in September. A rule that they use is that half the wheat yield comes from the main stem and half comes from the next two tillers. Quote Steve: "any more than two tillers is a waste of energy and a detriment to maturity". With this in mind I weighed the sorghum heads in the above photo. The weights, right to left, are 240g, 160g, 100g and 38g. The fourth head has no useful grain in it, even though it weighs 38g. I know that the weight of the stems has to come off, but I'll use these figures anyway. So the main head is 240g and the next two total 260g. Given that the main head is pretty dry and the next two are not, I'd say that half the yield coming from the main head is about right.
My friend Steve has an article you can read titled: "Ten tips to speed up maturity for spring seeded crops"
To summarise it all comes down to what you do on the day of seeding. I'll put my own list here as it applies to Sorghum.
- Start and finish sowing as early as possible. Use insecticides or seed treatments to avoid insect pressure.
- Optimise phosphorus rates and place with the seed. Phosphorus is less available in cool soils.
- Higher plant population and wider rows will reduce tiller numbers.
- Hybrid selection. Obviously earlier maturing but also cold tolerant varieties.
- Acurate seed depth control. Even seed depth = even maturity. Shallow seeding = warmer soil and quicker emergence, however soil temp is more even at depth and leads to more even emergence.
- Avoid fertiliser toxicity. Place N away from seed.