Act early to mitigate water stress

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The exceptionally dry April has significantly reduced soil moisture levels and with only limited rain forecast, growers may have to intervene to mitigate potential crop stress during the crucial canopy-building stage, leading agronomy firm Hutchinsons advises.

“While we are some way from drought conditions as yet, the level of moisture is surprisingly low under many winter cereal and rape crops and the current forecast predicts only average rainfall at best for May,” says technical manager Dick Neale.

“When soils begin to rapidly dry it is important to react in the earliest stages of moisture stress, rather than take action three to four weeks after the impact has set in.”

Plant responses to drought stress are complex, but there are two key areas that growers can focus on to mitigate the effects. These are to support photosynthesis and build root structure to improve scavenging ability for water and nutrients, Mr Neale continues.

Magnesium plays a central role in photosynthesis, but is one of the first nutrients to decline in availability during dry conditions, so it is important to maintain levels according to crop need, he says.

Potassium availability also drops markedly in dry soils, so a foliar application may be beneficial given the nutrient’s role in cell turgor, he adds.

Like potassium, nitrogen is required in larger amounts to build canopy and is vital for most energy-driven functions within plants, so Mr Neale recommends applying a foliar product such as N-Durance 28 or Persist-N, which will be more available than granular applications reliant on soil moisture for uptake. Additional sulphur may also be needed to support nitrogen utilisation.

Growers applying standard liquid nitrogen should take care to avoid scorch though, as this can be very damaging to moisture-stressed crops, he adds.

Mr Neale also points out that research is increasingly showing a benefit from applying boron between GS 39 and GS 45, even under severe moisture stress, given the element’s important role in germ tube formation, pollen and flower fertility, Mr Neale says.

A final option is to consider applying an amino acid-based biostimulant product, which can further help alleviate the impact of stress factors on crops, by reducing the accumulation of damaging metabolites within plants and by stimulating rooting. Seaweed extract-based products can also relieve stress responses, he says.

Looking longer-term, Mr Neale suggests that with prolonged periods of limited rainfall becoming increasingly common, growers may need to employ more measures to improve soil moisture retention and resilience to weather extremes, such as the regular inclusion of multi-species cover crops within the rotation.

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