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March 13, 2014

Making the most of the developing crops

As we move into the second week of March we’ve still to see much in the way of winter, reports Yorkshire-based agronomist, Sam Patchett.  A few night frosts certainly. But, with daytime temperatures comfortably above 5oC, our earlier-sown crops, in particular, are beginning to show signs of taking off.

With oilseed rape GAIs ranging from 1.0 to 2.5 – depending on variety and sowing time – early nitrogen hasn’t been an issue. Thankfully, given the weather, even our lower GAI crops aren’t needing a pick-me-up just yet. Mainly because by keeping seed rates down we’ve got well-balanced populations of strong, decent-sized plants.

As soon as we can travel, our first priority with the OSR is applying sufficient sulphur to support stem extension. But, with most spring fertiliser on-farm as N:S compounds, this will mean giving them nitrogen earlier than we’d otherwise like.

With this in mind, in most cases we’ll be including a good canopy-managing dose of Juventus (metconazole) in our spring spray programme alongside Kestrel (prothioconazole + tebuconazole) to keep light leaf spot at bay. Although the disease isn’t hard to find, it isn’t romping away. So, fingers firmly crossed, we should be able to hold off until mid-stem extension to get the best combination of branching and shortening from the PGR. If LLS shows any sign of taking-off, though, we’ll go in with the Kestrel early and come back with Juventus. We simply have to protect the excellent potential we have in this year’s crop.

As mentioned last month, we’re keeping our eyes peeled for pollen beetle too; especially as some of our crops aren’t that far off green bud already. So we could well need an insecticide along with the fungicide and our usual molybdenum and boron at mid-stem extension. Thankfully, we haven’t encountered much in the way of pyrethroid resistance here yet. But our tracking clearly shows it’s been coming down from the north. So we’ll be assessing every threshold case carefully and using an alternative wherever we have concerns.

With an early flowering firmly on the cards, we’ll also have to be on the ball with our sclerotinia control as we go into April. Our first choice here is a combination of boscalid and metconazole for both efficacy and resistance management – not to mention the bonus of extra plant growth regulation.

Good PGR management looks like being equally important for many of our wheats. Thick, lush, well-grown crops from early sowing combined with poor anchorage support from very wet soils means we need to guard against both stem and root lodging this season; especially as many of today’s varieties having relatively poor levels of lodging resistance.

We’ll be including a low temperature PGR like Meteor or Adjust with the T0 our forward wheats will be getting at the end of this month to keep the lid firmly on the Septoria we can see in every crop and protect susceptible varieties against the major rust threat. Then we’ll go in again with a second PGR split at T1 two weeks later. And where we don’t use a T0, we’ll employ a combination of Adjust and Cutlass for extra PGR effect.

Our T1 fungicide choice will depend on whether crops have had a T0 and how far ahead of T1 it was as much as on the disease spectrum. Where no T0 has been applied, Boogie (bixafen + prothioconazole + spiroxamine) will be our mainstay because it stands out as one of the best SDHI combinations in all our trial work for T1. For forward crops that have had a T0 we’ll be using a combination of Helix (prothioconazole + spiroxamine) and Phoenix (folpet). Unless the T1 is more than two weeks after the T0, that is. In which case, we’ll revert to Boogie for its extra power. Rust susceptible varieties, of course, will also receive a strobilurin at T1.

With plenty of mildew about, not to mention net blotch and the danger of symptom-less rhynchosporium, our winter barleys will also be getting a combination of prothioconazole and spiroxamine plus an SDHI at T1 – in this case Zulu (isopyrazam). Like the wheats, we’ll be including a trace element mix to ensure performance isn’t limited by any nutrient shortages.

Little and often will be our approach with winter wheat nitrogen, in particular. We’ve already managed to get around 40kg/ha N on some of our second and later-sown wheats to help build root mass after the sort of mild, wet conditions that really favour take-all development. And, by early April we’re looking to have applied an early dressing to the forward crops as well.

Like many of our OSRs, they may not need much early nitrogen for the canopy. But we really want to give them some decent protection against drought. After all, if recent seasons have taught us anything it’s to expect the unexpected!