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Cotton Seed Distributors article

Today I am talking to Dr Mike Bange from the Australian Cotton Research Institute and we are going to talk a little bit about earliness and managing the crops for maturity.

So Mike you and some of your colleagues have done quite a bit of work on this over a number of years, could you explain a little bit about some of the experiments and trials that you have done to look at the concept of earliness?

Yes Rob, a few years back Grant Roberts and Steve Milroy and myself ran a series of trials at all different scales to look at the concept of maturity and earliness. We had a number of large scale field trials in a number of different regions looking at principally the impact of IPM and different varieties, the IPM elements being comparing INGARD® at that time versus conventional varieties. We had some detailed agronomy trials run here at the research station where we looked at full combinations of nitrogen, by water, by PIX, by varieties looking at how those different management regimes were impacting on maturity and we have run some detailed physiology trials where we are looking at different varieties with different maturity and trying to understand how those varieties mature and why they mature differently. So we have had a fairly complete look at earliness and maturity.

Can we go into a little bit more of the detail; could you outline what the components of earliness are that are driving early maturity ?

We pretty well broke it down into a series of factors affecting maturity or earliness. The major ones we saw as we had to look at were obviously the season length where you grew the crop, the next most important one was variety followed by and appropriate IPM strategy and modifying your IPM strategies to impact on fruit retention was the issue in terms of driving maturity then followed by some more minor things and we were quite surprisingly things like nitrogen, water and PIX were the other elements that contributed to earliness, but much less than variety and IPM.

So looking at correlations I guess there has always been a thought that there are negative correlations between yield and earliness, is that what you found?

Unfortunately with earliness there is a price to be paid. You have got less time to grow a crop and less time to produce yield. On average over five seasons we have found for up to .6 or around ½ a bale per hectare of lint yield was lost for every weak reduction in maturity – it can be quite significant.

And what management factors can influence earliness so if you had to produce an early crop what are some of the things you would do to do achieve earliness in a relatively short season area?

Probably the things that I would like to quote is some figures in terms of what management factors actually did in terms of their impact on earliness and these are averaged over four or five seasons. For variety obviously they can have big impacts and that varies for the regions and that short of thing. IPM, we could modifying fruit retention we could bring the crop forward by up to 10 to 20 days so that is quite a big impact. For nitrogen we could move the crop for up to 2 to 3 days and about a similar amount for PIX. Knocking off the last irrigation had little or essentially no impact, the fruit had been set and it was going to mature anyway but it did impact on yield, the bolls were smaller. - so there basically the scale of the affects of those different management regimes.

And what about spray on earliness such as PIX, there is a lot of anecdotal evidence that PIX will have a major impact on earliness?

Well it is important probably to make the distinction about how you use PIX so if you are using PIX to assist with vegetative growth there is no benefit in using PIX to bring the crop early. If you are using PIX for “cut out” rates of PIX it will have an impact, you are basically shutting the crop down but some of the work that Grant did he was spraying high rates of PIX at flowering and he found that in the end though he was only bringing the crop forward by 2 to 3 days but there are certainly lots of things to suggest that if you hit it with high rates of PIX and continually hit it with high rates of PIX it will shut the crop down. For some people that is an obvious management strategy if they want to finish a crop by a certain time.

I guess manipulating earliness in short season areas is important to reduce the chance of weather damage we are all aware of those concepts and they make sense, but just to bring it a little bit more relevant to the current year, quite a few areas are limited with water they are going to run out of water early, are early crops always more water use efficient?

Well essentially yes, they are not growing for as long so they are going to use less water but at the same time they are going to produce less yield. In terms of lint yield, we are not so much talking about water use efficiency as in terms of amount of lint per water applied, what we are talking about is just less water use, I can’t say that early crops are actually more water use efficient as in water applied per bale of cotton lint. So definitely shorter crops will use less water and that is an obvious management strategy to deal with in limited water years.

Is there any more ongoing research on earliness? Have you given up on it or is there still more work to be done?

Maturity obviously is an important element in terms of crops because if we change the maturity we are impacting on yield. Some of the things that we are investigating and still working with is we have got Rose Roche’s work on narrow row and different populations and looking at how those systems can impact on earliness and whether there is any relationship and one of the things that we are looking at is how the relationships of plant populations and row spacing interact with other management factors and potentially changing maturity. Some of the other work that we have followed on from the work that Grant, Steve and myself did is we looked at some of the issues relating to the physiology of crop determinacy so trying to understand the concept of crop determinacy. Then there is the work that Steve Yeates and Dirk Richards are doing with Bollgard high fruit retention cotton and obviously looking at the systems maturity is an important aspect that they are doing. So we certainly haven’t ignored it we are just looking at it in different ways.

Thanks very much for that Mike.

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