Cotton Seed Distributors article
A video version is available at www.csd.net.au/  

David Armstrong and Bill Arthur, both longterm irrigated cotton growers on the Darling Downs, discuss their move into skip row systems, management implications , and yield and quality results.

Dave you have moved completely into skip row irrigation.  Obviously there have been a number of factors that contributed to this decision ?

Yes.  The main reason we have decided to change our configuration across the whole farm is that we are traditional 8 row 40 inch growers in a solid configuration and we have for several years been growing roughly 60% solid cotton and 40% single skip.  We were able to demonstrate some water savings and quality improvements in the single skip part of our operation and it had become a hassle machinery wise and staff wise to be running two sets of equipment. So we made the decision to grow 1.5 metre single row cotton on a 12 metre system.

So this move into the 1.5 metre single row system obviously necessitated quite a bit of change with machinery?

It has actually required a complete change of equipment. We have modified some existing equipment.  There hasn’t been a piece of equipment that we haven’t had to modify but we believe that we have obtained quite a few savings by doing that, particularly by going from the 8 row 40 to a 12 metre system and we have demonstrated a fairly significant fuel saving.

When compared with the solid plant, what are some of the differences you have seen in relation to the actual irrigation practices, water usage, irrigation, that type of thing?

Well last year was the first year that we completely converted the farm to 1.5 metre.  The year prior we had conducted a small trial and had demonstrated roughly 1/3 saving in our irrigation requirements.  Probably more important was the fact that the 1.5 metre system tends to give us an extra 2 – 3 weeks to apply irrigation.  So it gives us a little bit more control throughout heat stress periods and that was probably the main difference we noticed in our trial.

What sort of yield are you seeing in the system and how is your fibre quality standing up?

Fibre quality has been very good.  We were encouraged this year to see base grade on double cropped dryland 1.5 metre.  Yield was approximately 1 bale to the acre which, given the season, I thought was good for completely dryland.  Depending on field history we have been able to achieve probably between 2.8 and 3.6 bales to the acre average on our irrigation fields.  This year we had some three watered fields that went 4.1 bales to the acre across entire fields so we have been encouraged that we probably aren’t suffering a big yield penalty in our fully irrigated fields. Our average including the dryland was around the 2.6 – 2.7 bales to the acre which is the highest average we have been able to achieve in the last 5 years.

What degree of flexibility is built into the system if we do get back to a run of a season where your bores have a full allocation and ring tanks are full?

Well to be honest John there is absolutely no flexibility to return to either one metre or 40 inch or single skip conventional systems.  It has required a dedication or commitment to the new system because of the amount of equipment that we have had to modify.  But I don’t believe that we will be under a very significant yield penalty if we do return to full water because the blocks that  we did fully irrigate last season proved to be equal in yield to other years when we have fully irrigated 40 inch.

As far as the technology split goes, you have adopted a pretty high level of Bollgard and Roundup Ready here?

Yes we have been 100% on both technologies for as long as they have been available. We tend to be able to demonstrate some benefit in the system by  managing our volunteers.  Volunteers have probably been the biggest issue for us because of our 100% Roundup Ready.  We are controlling that through rotation and our new configuration where we now grow 16 row, 75 cm sorghum on a tram track equal to the 8 row 1.5 metre cotton system.  We are going away from black fallows to more of a stubble retention system.

You have been growing irrigated cotton in a double skip row configuration for over 10 years now.  You are obviously happy with the results you are achieving?

Yes John and given the rain scenario over that 10 year period, it’s one of the few options I thought we could take.

Your system is basically planting into fallow country and waiting for the river to flow to convert you into an irrigated grower?

 That’s correct. I can’t remember the last time we had a full ring tank, hence when we make a planting decision, we never have enough water to go around.  Last year we planted on rain and then received a flow to back us up and that’s the way it worked out.

Under a system like this, how do you manage things like your nitrogen fertilizing program?

For our nitrogen, we put down about 80 – 90 units preplant with a view to water running gas if we had the water to require it. That way if we don’t have the water it just goes through on its 80 – 90, and if we do get the water, then we can boost it up to 150 or something like that if we need to.

So as far as your irrigation practices go with this system, how many waters do you normally give the crop and how easy is it as a system in the double skip to manage irrigation practices?

Managing the irrigation is fine.  We use probes to schedule, particularly our first irrigation.  Often times we only have enough for two incrop.  This year for example we didn’t quite get across with our second irrigation. So yes, we use  diviner probes to schedule our first and second irrigations and if we’ve got enough water for three well that’s even better.

And you irrigate between the rows and down the skip?

Yes every 2 metres we will have a syphon, with one down between the rows and the other the centre of the skip.

Just talking about yields from this system.  What have you been averaging and what has been your best result?  

This year we averaged 6.1 bales to the hectare.  Previous year was 6.5.  Our best field result I suppose was a field of conventional 80 that went just over 3 bales to the acre two seasons ago.

Now obviously Bollgard has been grown in the system for the last two years.  This has made it more attractive to you? 

Well this has made management a bit easier for us.  This year we were all Bollgard.  So that saved us quite a few in crop sprays and stuff like that.  It worked out pretty well.

And fibre quality obviously has played an important part in your decision to go with this system over the years?

Fibre quality was the main issue and the main reason we went to the double skip.  The last time I planted solid was a particularly dry year and we took a punt on rain and a run on the river and it didn’t happen. The discounts from short thick fibre was just too heavy to continue with optimistically hoping for rain in a solid plant situation so fibre quality is definitely the reason we have gone that way.

As far as machinery goes, you haven’t had to make any major changes to manage your cotton under this system?

No John and that’s the main reason we have stayed at double skip.  We have tooled up for 8 metres and it’s just as easy to drop 4 out of the 8 rows and maintain the 8 metre configuration.  If I had a choice and was starting from scratch, I would seriously look at perhaps single 60’s or something like that as an option to the double skip but I am happy to stay with double skip at the moment.

Now any problems - obviously you get some pretty big plants in your double skip configuration with a couple of irrigations.  Has that created any problems for defoliation, picking or things like that?

Well it has, particularly for the big yielding conventional crop that we grew a couple of years ago where the bush got quite big. It almost closed in the double skip.  It made defoliating with our normal spray tractor impossible.  A coupe on 3 metres spacing didn’t quite handle it either so really the only option is to go by plane or as we did this year, we got a contractor in with a four metre wheel base and that worked out really well.

So possibly a bit of PIX management and using Bollgard crops could alleviate the problem to some extent?

Well it did and that was the case this year as well.  The Bollgard didn’t go quite the way the conventional did, and the rows didn’t close in quite as much but I think we still needed the 4 metre wheel base to reduce any damage on the bush when it’s fully laden.

I suppose on occasions you have considered a solid plant and taking a couple out if the water doesn’t come. Has that come into your decision making ever?

It hasn’t really.  It has been such a long time since we have had a full profile of moisture and a full ring tank. In that situation I would think about solid again but unless we had that, I am just as happy to go with my double skip with the potential to irrigate it and I know we probably won’t yield as high at the end of the day, but I can be pretty confident that if the season turns against us, our quality will be maintained and our yield will be OK.