Pete Berry and Emily Guest
In early July, the yield potential for winter wheat was generally high, as most crops should have received enough rainfall by mid-May to see them through the dry June (except those on light land) and conditions have been favourable for high ear numbers and grain set. Exceptions will be the crops which had high Septoria levels, despite robust fungicide programs, which will have reduced their yield potential. Since early July, torrential rainfall has caused widespread lodging which will mean that the initial decent yield potentials will now be difficult to realise for many crops.
Positive factors for yield:
- Early harvest in 2022 meant that a lot of wheat crops could be established in September when conditions were good. However, wet weather later in autumn resulted in difficult establishment conditions, especially for those crops which were drilled late, to reduce black grass pressure.
- We had a bright, dry, and slightly warmer than average winter - the YENs have shown this to be positive for yields, aiding establishment and encouraging deep rooting.
- Though March was quite dull, the other spring months were much sunnier than average (apart from in the Southwest) which will have helped tillering and tiller retention.
- Plentiful spring rainfall meant that fertiliser was rapidly washed into the soil.
- March had well above average rainfall, April had average rainfall (albeit geographically sporadic) and the first half of May had near normal rainfall. On 16th May, typical soil moisture deficits were less than 20 mm. If roots extend to 1 m soil depth, then the available water of a medium loam soil will be about 170 mm. At an average evapotranspiration rate of 3 mm per day, there should have been about 50 days of water stored in the soil, enough for most crops (except those on light soil) to tolerate the subsequent dry period, which lasted about 6 weeks.
- June was very sunny which will have increased both the number of grains set per ear and the potential grain size.
Negative factors for yield:
- Some fields have more blackgrass than usual, potentially caused by dry periods during early autumn, making achieving a weed seed chit and effective stale seed-bed difficult before some earlier sown crops.
- The warm June conditions will have reduced some of the benefits of the sunny conditions on grain number and grain size by shortening the periods of development for grain set and potential grain size determination.
- Where high temperatures of >30oC occurred during flowering, this will have reduced grain set.
- The wet March led to issues with travelling, meaning some N applications were delayed.
- Septoria levels have been higher than average, whilst yellow rust pressure has been slightly lower than normal. The levels of disease depends on location, variety and sowing date, with early sown, more susceptible varieties seeing high levels of Septoria which has proved difficult to control.
- Torrential rainfall during July and early August has resulted in widespread lodging which will reduce yield and quality for many crops.
In conclusion, wheat yield potential was generally above average at the start of July, except for crops with i) high Septoria pressure - especially for early drilled crops, and ii) crops on light soil or with shallow rooting which could not tolerate the dry June. Since early July, the high rainfall and windy conditions have resulted in widespread lodging and mean that many crops will not now realise their potential yields.
Actions
At harvest time, measure ears/m2, grains per ear and thousand grain weight and compare these with wheat growth guide benchmarks of 460 ears/m2, 48 grains per ear and a TGW of 50g, to see how your crop performed.