Ten plants a metre isn't always a ten-plant stand

By James Quinn, General Manager, Sales and Operations, Goanna Ag

For a long time, one of the first things we've done after cotton emergence is count plants. Walk a metre, count them, and if the number lands somewhere between eight and twelve, call the population target achieved and move on.

It's a sensible habit, and it has served the industry well. But after many years of looking at cotton establishment, I've become increasingly interested in a different question. Are we just counting plants, or are we measuring how well the stand can actually function?

Some multi-year trial work we pulled together has made me think differently about this. Across seven seasons, 35 sites and 883 plots, we looked not only at plant population but at the distance between individual plants. One finding in particular caught my attention. When plants were less than about 3 cm apart, the yield relationship was better explained by treating them as one effective plant rather than two.

Think about what that means in the paddock. You might count ten plants in a metre and conclude you have an excellent stand. But if several of those are doubles or tight clumps, and another part of that same metre has a significant gap, you don't really have ten productive plants. Our analysis suggests you have fewer.

And it isn't just about doubles. At similar effective plant populations, stands with more variability in the spacing between plants tended to yield less. The most reliable high-yield zone in the dataset combined an adequate effective population with relatively uniform spacing down the row.

That makes sense when you think about what each plant needs: fair access to light, water and nutrients, room to branch and set fruiting sites, and enough space from its neighbours to make its own contribution to yield. Cotton compensates, and it compensates well. But compensation doesn't mean poor spacing is free.

This is why establishment sits first among the five traits we work through in our High-Performance Irrigation Masterclasses. When we analysed thousands of irrigations across our irrigation management solution, GoField the remarkable thing wasn't how different seasons and regions were. It was how similar the best irrigators were, and how consistently they started with a strong, even stand planted at the right time. Well sown really is half grown.

Timing is where a lot of that is won or lost. In the 2023/24 season, our analysis showed around 14% of crops were planted early, into soil that wasn't ready to give them an even start. That's the thinking behind the Australian Cotton traffic light soil temperature forecast we developed for the FastStart Program through links to Goanna Ag weather stattions, which forecasts soil temperature to within half a degree out to five days.

Modern varieties have raised the stakes further. Cotton Seed Distributors' trial work found establishment around 90% in good/green traffic conditions regardless of seed density. In poor conditions, normal-density varieties fell to about 55% and low-density varieties to between 20 and 35%. At that point, the conversation is about replanting.

What happens at establishment doesn't stay at establishment. An even stand sets the crop up from the start,  We all know that cotton establishment is driven by soil temperature and knowing what the soil temperature is going to be is the first step in getting that uniform and healthy established plant stand.

So perhaps we need to change the way we assess establishment. Instead of walking into the field and asking only how many plants per metre we've got, we should be asking how many effective plants we've got, and how well they're distributed. Look for the doubles, the clumps and the gaps, and whether the plants are spread reasonably evenly down the row. The practical target emerging from the work remains around 8 to 12 effective plants per metre for most irrigated valleys, but the word that matters most is effective.

Ten plants per metre isn't necessarily a ten-plant stand. And sometimes the opportunity to improve yield isn't about putting more seed in the ground. It's about getting it right from the start, that starts with field and planter set up, the correct soil temperature at planting. Because every decision that follows through the season is built on it.