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Take care with PGRs in spring crops

With more land going into spring cropping this year, leading agronomy firm Farmacy advises growers pay close attention to plant growth regulator (PGR) requirements ...

 With more land going into spring cropping this year, leading agronomy firm Farmacy advises growers pay close attention to plant growth regulator (PGR) requirements to manage lodging risk and aid establishment in a difficult season.

Most spring crops require at least one PGR application, but spring barley and oats often need two in order to reduce the lodging risks as crops race through growth stages, explains Alice Cannon, the firm’s regional technical support manager for East Midlands.

Experience also shows that, as in winter cereals, an early, low rate, application of trinexapac-ethyl or chlormequat plus phosphites to spring cereals can help improve tillering and root development; something that may be beneficial given the delays and disruption to drilling caused by the weather, she says. Zinc, and/or biostimulants can further assist root development and crop establishment.

Managing risks

Miss Cannon says lodging risks are often greater on heavier soils, or in thicker crops, such as where growers have increased the seed rate to compensate for later drilling.

“Increasing the seed rate by 100 seed/m2 in spring barley increases the lodging risk by 1.5-2 points on the Recommended List rating. Where crops are being positioned in heavier soils or high-risk situations, then at least one PGR application should be planned.”

There are three potential application timings in spring barley, namely T0 (growth stage 30), T1/1.5 (GS 31-32) and T1.5/T2 (GS 39), although the key timing is T1/1.5, she advises. Product choice should be tailored to crop type, lodging risk, growth stage and other crop requirements, recognising that the latest application cut-off may differ for individual products. Care should also be taken to check the label requirements if planning to use split doses of chlormequat.

The T1 and T1.5 (GS 30-32) timing is also the main period for PGRs in spring oats, although crop growth stages should be monitored extra closely to ensure applications are not missed, as oats can move through growth stages particularly quickly, she says.“I highly recommend starting the PGR programme early to ensure you don’t miss applications as the product cut-offs are much earlier in oats. Also be wary of end market contract restrictions for certain PGR products.”

Spring oats are also more sensitive to agrochemicals than spring barley, so extra focus should be given to cultural controls to reduce lodging risk, such as careful nitrogen application and timing, rolling and drilling date. She recommends avoiding mixing PGRs with herbicides to minimise the risk of crop damage.

“You may find that spring cereals grown in the traditional light land situations, may not need a PGR application as lodging risk can be well managed with cultural controls.”

Recognising the considerable disruption the weather has caused to drilling programmes this season, Miss Cannon also reminds growers that anything drilled from 1 February onwards is legally classified as a spring crop, so must be treated as such when planning any crop protection inputs, as options may differ to winter crops.

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