Cotton Seed Distributors article

A video version is available at www.csd.net.au/  

Probably the first consideration you have got to think about is what area do you grow?  You get some people who are very conservative and will plant only enough area that they have got full irrigation water for and that is probably the safest bet.  There are other people who say right ‘I will plant the whole farm’ and hopefully water allocations increase during the year and you are able to maximize your return on taking that punt.  There is obviously a lot of other people that go somewhere in between there so it is a big decision and it comes really down to your attitude towards risk and also obviously depends on where you are, that decision is not going to be the same if you are a grower on the Darling Downs or in the Upper Namoi where summer rainfalls may be a bit more common whereas somewhere like the Macquarie or western New South Wales, summer rainfall is probably not quite as common so you are going to approach it very differently.  

A lot of the hard work in terms of analysing historic weather data has been done by CSIRO through the development of HydroLOGIC which incorporates the OzCOTT model which is a crop development model with long term weather data so you can put in scenarios and say ‘if I enter a season with this much water, what chance have I got of achieving a good yield” and some of the information that the HydroLOGIC spits back out is that in say some of the western and southern regions without a good history of summer rainfall if you go into a season with five or six megalitres at the start of the year in nine years out of ten you might break even.  Some of the other areas with a bit more of a historic rainfall where you can go into the season with four or five megalitres per hectare and break even in nine out of ten years.  So it is a decision support tool, it doesn’t make the decision for you it just hopefully adds a little bit more data to the decision you are going to make.  I really encourage people to go to the Cotton CRC website and find our how they can get hold of HydroLOGIC.

If people have planted more area than they have got irrigation water for the scheduling of those limited irrigations is going to be very important.  Can you tell us a bit about what sort of things you think about in terms of scheduling with a limited water situation?

Yes, I think there is probably two main options for growers to consider and one is stretching the water out between irrigations so getting an extra day, two to three days between irrigations and try and get the water further into the season and the other one is to water as per normal and then at the end of the year if you run out the water gets cut off and we are in the ‘lap of the gods’ kind of thing.  

The overall success of both these strategies comes down to when you get rain and how much you actually get, what your soil type is like and it also comes back down to another thing of your seasonal conditions.  We all know that the crop uses different amounts of water throughout the whole season at the beginning of the season that the water is lower in the middle of the season when it is doing a lot of its work in boll filling and trying to grow and put more fruit on it is really starting to pump a lot of water through the soil profile and at the end of the season when things start to shut down the water use goes back down again.  It comes back to your timing of the stress, say early on you have probably got a slow node production in regards to if it is close to first flower or something like that could limit the potential of the crop and give you a premature cut out sort of a situation.  During boll fill it is going to impact on boll numbers and definitely fibre quality.  If it is one of the last irrigations it is probably only going to shed some of those last bolls.  If you had a choice of where you wanted to stress the plant it would probably be that end of the season, post cut out, post peak boll fill or that is where we feel that it would probably be the least impact on yield.  

Dave I suppose the other thing in regards to irrigation is the skipping of rows at planting time.  Guys might go in with a one in and one out crop type figure at double skip or single skip configuration and maybe give it one or two waters.  This is going to limit the actual yield figure per hectare on a per hectare basis but over the whole farm unit may be able to increase the bales per megalitre they may get.  

The considerations in regards to this are the same that would be considerations in dryland cotton.  What they are trying to do is basically buy some time.  Extend the period on where the plant is not in stress, take it out further hopefully get use of some handy rainfall showers and extend themselves further and further into the season before that plant comes under stress.  

Sometimes growers will plant solid with the option of ploughing some rows out to skip row.  Can you tell us what sort of consideration you go through for that sort of decision?

One of the key points these days is if you are going to do it you do it very early because you can actually limit the ability of those plants that you have left in there to get across the skip to source that moisture that you have hopefully made available to them.  In saying that the plants that you have are obviously going to be using moisture before you take them out and if you wait too long they have obviously taken a fair bit of moisture from the soil profile already and its wasting moisture.  

There are a couple of things in regards to that.  I think the soil type is one of those things in cracking clay, very nice forgiving soil that situation may be a little bit better than say a hard setting or a redder type soil where the roots are going to have trouble trying to expand across.  So if you do it, do it early or don’t do it at all.

You mentioned soil type.  That is probably going to have some bearing on what field you select too if you were going to have the choice of selecting a number of fields?

Yes I think field selection, it’s a curly one actually in regards to do you try and go close to the storage and try and limit the transmission losses of the system.  What I think is though I think that you have really got to start looking for your best soils in the first place.  The soils with the greatest water holding capacity.  If they are in fallow you have had a lot of time to fill that profile up through showers throughout the fallow period but you want to look for those best soils that have the best water holding capacity and will give you the best chance of growing that crop.  Soils that are a little bit less in the water holding capacity, it may have its other advantages but when it comes to the crunch you really need that big bucket to grow this crop and make sure that the amount of stress that you apply to them is a little bit stretched out until later and later into the season. 

Dave I suppose the final point that we have come to now is basically the grower’s variety selection. Can you just give us a run down on what your thoughts are in regards to that?

I guess the principles with managing, having a variety here in the limited water situation is very similar to selecting a variety for dryland situations and research and experience has really shown that vigorous full season very indeterminate varieties with inherently longer staple are the best suited to this sort of situation.  In the past some growers have in a limited water situation have said ‘I will grow a quicker maturing variety and try and finish the crop off while I have still got my available water and that really hasn’t worked.  Some of those shorter season varieties they are not actually that much shorter that you are going to save a huge amount of water by doing that and under a stress situation they tended to cut out and if you did get water allocation later on in the season they are probably less likely to grow on and put on that valuable second crop that are more indeterminate type thing would be.  

So I guess looking at some example varieties in the CSD suite, in the conventional we have got sort of the likes of Sicot 81, Siokra 24, are particularly good.  In the straight Bollgard’s we have got Sicot 80B, Sicot 289B, Sicot V-16B and now Siokra 24B.  In the Bollgard® Roundup Ready, Sicot 289BR, and in situations where you haven’t got Fusarium, probably Siokra V-16BR. The new Sicot 80 Bollgard Roundup Ready Flex® will probably have a great fit in there.  It has got a very similar yield and fibre quality package to Sicot 80B and having that Roundup Ready Flex® will probably also be a great advantage in these sort of situations to that if you are working in skip row situations you can manage weeds a lot quicker.  It is probably an important point to make that Bollgard II technology is very useful in this situation because basically having insect control happening all the time and in a limited water situation if your crop is going to stress and you have got insect pressure as well, in a conventional situation you are sort of wondering whether you want to spend a lot of money applying insecticides to it.  At least with Bollgard II the insect control has been done so it sort of takes yield variability out of it so it is a pretty useful piece of technology.