Pete Berry YEN Conference

Speaker: Pete Berry, ADAS.

This is a summary of the YEN Conference 2026 session: Impacts of warm, dry and wet conditions on crop performance

The session began with a poll asking which factors most frequently reduce crop yields, with drought and lack of sunshine emerging as the top concerns. Definitions were provided to distinguish between climate (long-term weather patterns) and weather (day-to-day atmospheric conditions). The text outlines recent changes to the UK climate, noting increased warming, wetter winters, sunnier springs, and projections for hotter, drier summers. The challenges faced by farmers include both long-term climate trends, such as warming and altered rainfall patterns, and short-term weather difficulties like extended dry or wet spells, making it hard to predict conditions at the start of the season. Strategies for managing crops in warmer and drier conditions focus on earlier flowering, deeper rooting, adequate water supply, and sufficient nutrient application, particularly phosphorus. Dry conditions emphasise the importance of root depth and early drilling, while wet conditions bring risks such as waterlogging, nutrient leaching, disease, and lodging. Management recommendations include choosing resilient crop varieties, adjusting sowing times, using urea to reduce nitrate leaching, and maintaining robust fungicide and growth regulator programmes.

Key Messages:

  • We need a crop husbandry strategy that deals with the long-term climate trends for warmer conditions and the greater likelihood of very high temperatures, whilst also being resilient to seasonal challenges of long dry or wet periods.
  • We do not know the weather conditions of the growing season before it happens, so we need to grow crops that are resilient to both dry and wet conditions
  • A few key factors to get right include: maximising rooting depth, ensure sufficient N and P for canopy longevity and achieving well drained fields

The session started with an audience poll asking: 

Which of these factors reduce your crop yields most frequently?

  • Drought
  • Waterlogging
  • High temperatures
  • Low temperatures
  • Lack of sunshine

Lack of sunshine and drought came out as the top impact on crop yields from the poll.

Definitions:

  • Climate - long-term average weather patterns
  • Weather - short-term day-to-day state of the atmosphere

Changes to the UK Climate

  • UK has been warming at 0.25 degrees C per decade since the 1980s. (Frequency of very high temperatures has increased)
  • 2015-24 October to March period was 16% wetter than 1961-1990
  • 2015-24 springs were 16& sunnier than 1961-1990
  • UK climate projections for hotter drier summers (UKCP18 Science Overview Report)

UK Mean TemperatureUK Rainfall Oct-Mar

Kendon et al. (2025). International Journal of Climatology

Increasingly variable crop yields

UK Winter Wheat Yield

The challenges

  • Long-term climate trends:
    • The climate is getting warmer
      • Greater likelihood of high temperatures
      • General pattern of wetter winters and projection of dryer summers
  • Short-term weather challenges:
    • Long periods of dry or wet weather
      • Big challenge: Don't know before drilling whether the season will be dry or wet

To address these challenges we need a crop husbandry strategy that deals with warmer conditions and the greater likelihood of very high temperatures, while being resilient to long dry or wet periods.

Effect of warmer conditions

Effect of warmer conditions on growth phases

  • Warm conditions shorten all 3 growth phases, but shorten the production (grain filling) phase the most. 
  • Warm conditions have a limited impact on the length of the Foundation and Construction phases:
    • The start of stem extension depends on a combination of photoperiod (longer days in spring) and vernalisation (exposure to cool temperatures of 0-12 degrees C)
    • Flowering date depends of photoperiod
  • High temperatures during flowering (>30 degrees C) reduce the number of grains set.

Crop management for warm conditions

  • Earlier flowering and grain filling
    • Shift grain filling to slightly cooler conditions
    • Reduce risk of damaging high temperatures at flowering (but increase risk of frost)
    • Reduce water use as less biomass at flowering
    • Variety choice
  • Ensure sufficient water supply
    • Deeper roots
      • Earlier drilling (bad for black grass, septoria and some pests)
      • Alleviate soil compaction
    • Irrigate
  • Ensure sufficient N and P for canopy longevity (avoid self-destruction)
    • Is your fertiliser strategy enough for high yield?

Insufficient nutrients being applied

Current trends show a worrying depletion of soil nutrients, particularly phosphorus.

Phosphorus offtake

Nitrogen Offtake

Effect of dry conditions

In dry conditions, root depth is especially important. The required root depth for a high yielding crop varies based on soil type and rainfall. Consider strategies to improve rooting including alleviating compaction and early drilling.

Effect of dry conditions

Action: in a dry year estimate the depth of your roots based on yield, rainfall and soil type.

2025 drought: In 2025, the UK experienced around 40% of normal rainfall from March to June. So how did this effect the 2025 YEN Wheat entries?

Comparison of 2025 YEN wheat with previous years:

  • 2025 yields 13% less than YEN average
  • Ears/m2: Less
  • Grains per ear: Less
  • Total Grain Weight (TGW): Greater
  • Total biomass: Less
  • Harvest index: Slightly greater

Comparison of 2025 YEN Wheat with previous years

Oilseed Rape (OSR) and the 2024-25 growing season

The 2024-25 growing season was an exceptional one for Oilseed Rape. This was due to idea weather conditions and low Cabbage Stem Flea Beetle pressure. 

Weather factors associated with high OSR yield (1979-2017) include:

  • High Maximum Temperature in October
  • Dry December
  • Warm min temp March
  • Sunny/Dry April
  • Wet/Cool May

2024-25 weather & effect on OSR yield

2024-25 weather & effect on OSR Yield

These favourable conditions were reflected in the fact that the three best YEN crops of 2025 were all over 7t/ha.

Crop management for dry conditions:

  • Crop species that mature early typically perform better (e.g. winter barley, winter oilseed rape)
  • Early maturing varieties may also perfoRm better
    • Use AHDBs Recommended Lists to select varieties that perform better in dry years/environments
  • Early drilling (or avoid late drilling) to maximise autumn root growth
  • Avoid sub-optimal plant population as spring tillering restricted
  • Early fertiliser to minimise the risk of slow N uptake in dry conditions
  • Consider: early drilling, high plant population, early N will increase risk of lodging and disease , in an average or wet year
  • Place P as uptake appears to be reduced in dry spring
  • Improve soil water holding capacity

Effect of wet conditions

  • Waterlogging
  • Nutrient leaching
  • Disease
  • Lodging

Waterlogging effects

  • Shift from aerobic respiration to anaerobic fermentation
  • Plant uses up carbohydrate reserves
  • Uptake of nutrients is inhibited
    • within 48 hours
  • Plant stomata close - reduced photosynthesis
    • within 72 hours
  • Increased nodal root production, chlorosis, premature death of leaves and tillers
  • Most detrimental up to tillering (cereals) or green bud (OSR)
    • 46 days of waterlogging during tillering reduced yield by 20-24% (Dicken et al, 2008)

Crop management for wet conditions that do not contradict with strategies in dry conditions:

  • Choose varieties resistant to disease and lodging
  • Choose species/varieties that could be sown in spring if autumn is too wet
  • Use urea to help reduce risk of nitrate leaching
  • Be ready with a robust fungicide & PGR programme

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